dropbear: add ed25519 and chacha20-poly1305

- add Ed25519 support (backport): * DROPBEAR_ED25519 option for ssh-ed25519, * disabled by default - add Chacha20-Poly1305 support (backport): * DROPBEAR_CHACHA20POLY1305 for chacha20-poly1305@openssh.com, * enabled by default - update feature costs in binary size Signed-off-by: Vladislav Grishenko <themiron@mail.ru>
author: Vladislav Grishenko <themiron@mail.ru> 2020-04-13 03:24:28 +0500
committer: Hans Dedecker <dedeckeh@gmail.com> 2020-05-30 21:27:10 +0200
commit: f166cf9ca07ceb023db356532cf4154ef433322a (patch)
tree: dbc22710b222fb4e437a3d581fa085c8e423033d /package/network/services
parent: 02f08056bcbc5f014894b7edcea43f2ff822fd90 (diff)
download: upstream-f166cf9ca07ceb023db356532cf4154ef433322a.tar.gz
upstream-f166cf9ca07ceb023db356532cf4154ef433322a.tar.bz2
upstream-f166cf9ca07ceb023db356532cf4154ef433322a.zip
5 files changed, 3613 insertions, 3 deletions
diff --git a/package/network/services/dropbear/Config.in b/package/network/services/dropbear/Config.in
index 61a04ec876..3de4189e08 100644
--- a/package/network/services/dropbear/Config.in
+++ b/package/network/services/dropbear/Config.in
@@ -8,7 +8,7 @@ config DROPBEAR_CURVE25519
 		This enables the following key exchange algorithm:
 		  curve25519-sha256@libssh.org
 
-		Increases binary size by about 8 kB uncompressed (MIPS).
+		Increases binary size by about 4 kB (MIPS).
 
 config DROPBEAR_ECC
 	bool "Elliptic curve cryptography (ECC)"
@@ -49,6 +49,24 @@ config DROPBEAR_ECC_FULL
 
 		Increases binary size by about 4 kB (MIPS).
 
+config DROPBEAR_ED25519
+	bool "Ed25519 support"
+	default n
+	help
+		This enables the following public key algorithm:
+		  ssh-ed25519
+
+		Increases binary size by about 12 kB (MIPS).
+
+config DROPBEAR_CHACHA20POLY1305
+	bool "Chacha20-Poly1305 support"
+	default y
+	help
+		This enables the following authenticated encryption cipher:
+		  chacha20-poly1305@openssh.com
+
+		Increases binary size by about 4 kB (MIPS).
+
 config DROPBEAR_ZLIB
 	bool "Enable compression"
 	default n
diff --git a/package/network/services/dropbear/Makefile b/package/network/services/dropbear/Makefile
index b30229300c..8de0739d56 100644
--- a/package/network/services/dropbear/Makefile
+++ b/package/network/services/dropbear/Makefile
@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=dropbear
 PKG_VERSION:=2019.78
-PKG_RELEASE:=4
+PKG_RELEASE:=5
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.bz2
 PKG_SOURCE_URL:= \
@@ -29,6 +29,7 @@ PKG_FIXUP:=autoreconf
 PKG_CONFIG_DEPENDS:= \
 	CONFIG_TARGET_INIT_PATH CONFIG_DROPBEAR_ECC CONFIG_DROPBEAR_ECC_FULL \
 	CONFIG_DROPBEAR_CURVE25519 CONFIG_DROPBEAR_ZLIB \
+	CONFIG_DROPBEAR_ED25519 CONFIG_DROPBEAR_CHACHA20POLY1305 \
 	CONFIG_DROPBEAR_UTMP CONFIG_DROPBEAR_PUTUTLINE \
 	CONFIG_DROPBEAR_DBCLIENT
 
@@ -63,6 +64,7 @@ define Package/dropbear/description
 endef
 
 define Package/dropbear/conffiles
+$(if $(CONFIG_DROPBEAR_ED25519),/etc/dropbear/dropbear_ed25519_host_key)
 $(if $(CONFIG_DROPBEAR_ECC),/etc/dropbear/dropbear_ecdsa_host_key)
 /etc/dropbear/dropbear_rsa_host_key
 /etc/config/dropbear
@@ -110,6 +112,12 @@ define Build/Configure
 			$(PKG_BUILD_DIR)/localoptions.h; \
 	done
 
+	echo '#define DROPBEAR_ED25519 $(if $(CONFIG_DROPBEAR_ED25519),1,0)' >> \
+		$(PKG_BUILD_DIR)/localoptions.h
+
+	echo '#define DROPBEAR_CHACHA20POLY1305 $(if $(CONFIG_DROPBEAR_CHACHA20POLY1305),1,0)' >> \
+		$(PKG_BUILD_DIR)/localoptions.h
+
 	# remove protocol idented software version number
 	$(ESED) 's,^(#define LOCAL_IDENT) .*$$$$,\1 "SSH-2.0-dropbear",g' \
 		$(PKG_BUILD_DIR)/sysoptions.h
@@ -160,6 +168,7 @@ define Package/dropbear/install
 	$(INSTALL_DIR) $(1)/etc/dropbear
 	$(INSTALL_DIR) $(1)/lib/preinit
 	$(INSTALL_DATA) ./files/dropbear.failsafe $(1)/lib/preinit/99_10_failsafe_dropbear
+	$(if $(CONFIG_DROPBEAR_ED25519),touch $(1)/etc/dropbear/dropbear_ed25519_host_key)
 	$(if $(CONFIG_DROPBEAR_ECC),touch $(1)/etc/dropbear/dropbear_ecdsa_host_key)
 	touch $(1)/etc/dropbear/dropbear_rsa_host_key
 endef
diff --git a/package/network/services/dropbear/files/dropbear.init b/package/network/services/dropbear/files/dropbear.init
index 173ab09285..daf111fadb 100755
--- a/package/network/services/dropbear/files/dropbear.init
+++ b/package/network/services/dropbear/files/dropbear.init
@@ -66,7 +66,7 @@ hk_generate_as_needed()
 	kdir='/etc/dropbear'
 
 	kgen=''
-	for ktype in ecdsa rsa; do
+	for ktype in ed25519 ecdsa rsa; do
 		hk_verify "${kdir}/dropbear_${ktype}_host_key" && continue
 
 		kgen="${kgen} ${ktype}"
diff --git a/package/network/services/dropbear/patches/020-backport-ed25519-support.patch b/package/network/services/dropbear/patches/020-backport-ed25519-support.patch
new file mode 100644
index 0000000000..00a3bbbee1
--- /dev/null
+++ b/package/network/services/dropbear/patches/020-backport-ed25519-support.patch
@@ -0,0 +1,2890 @@
+From 3d12521735e7ef7e48be217af0f27d68e23050a7 Mon Sep 17 00:00:00 2001
+From: Vladislav Grishenko <themiron@users.noreply.github.com>
+Date: Wed, 11 Mar 2020 21:09:45 +0500
+Subject: [PATCH] Add Ed25519 support (#91)
+
+* Add support for Ed25519 as a public key type
+
+Ed25519 is a elliptic curve signature scheme that offers
+better security than ECDSA and DSA and good performance. It may be
+used for both user and host keys.
+
+OpenSSH key import and fuzzer are not supported yet.
+
+Initially inspired by Peter Szabo.
+
+* Add curve25519 and ed25519 fuzzers
+
+* Add import and export of Ed25519 keys
+---
+ .travis.yml            |   1 +
+ FUZZER-NOTES.md        |   3 +
+ LICENSE                |  71 ++--
+ Makefile.in            |  12 +-
+ README                 |   1 +
+ cli-kex.c              |   2 +-
+ common-algo.c          |   3 +
+ common-kex.c           |  14 +-
+ curve25519-donna.c     | 860 -----------------------------------------
+ curve25519.c           | 502 ++++++++++++++++++++++++
+ curve25519.h           |  37 ++
+ default_options.h      |   7 +-
+ dropbear.8             |   6 +-
+ dropbearkey.c          |  25 ++
+ ed25519.c              | 184 +++++++++
+ ed25519.h              |  54 +++
+ filelist.txt           |   4 +
+ fuzz-common.c          |   8 +
+ fuzz-hostkeys.c        |  10 +
+ fuzzer-kexcurve25519.c |  72 ++++
+ gened25519.c           |  47 +++
+ gened25519.h           |  36 ++
+ gensignkey.c           |  10 +
+ keyimport.c            | 158 +++++++-
+ signkey.c              |  60 ++-
+ signkey.h              |   7 +
+ ssh.h                  |   2 +
+ svr-kex.c              |   8 +-
+ svr-runopts.c          |  24 ++
+ sysoptions.h           |   7 +-
+ 30 files changed, 1289 insertions(+), 946 deletions(-)
+ delete mode 100644 curve25519-donna.c
+ create mode 100644 curve25519.c
+ create mode 100644 curve25519.h
+ create mode 100644 ed25519.c
+ create mode 100644 ed25519.h
+ create mode 100644 fuzzer-kexcurve25519.c
+ create mode 100644 gened25519.c
+ create mode 100644 gened25519.h
+
+diff --git a/.travis.yml b/.travis.yml
+index 9bcbce4..99499c8 100644
+--- a/.travis.yml
++++ b/.travis.yml
+@@ -57,6 +57,7 @@ script:
+   - ~/inst/bin/dropbearkey -t ecdsa -f testec256 -s 256
+   - ~/inst/bin/dropbearkey -t ecdsa -f testec384 -s 384
+   - ~/inst/bin/dropbearkey -t ecdsa -f testec521 -s 521
++  - ~/inst/bin/dropbearkey -t ed25519 -f tested25519
+   - test -z $DO_FUZZ || ./fuzzers_test.sh
+ 
+ branches:
+diff --git a/FUZZER-NOTES.md b/FUZZER-NOTES.md
+index 7b88238..4967eba 100644
+--- a/FUZZER-NOTES.md
++++ b/FUZZER-NOTES.md
+@@ -72,3 +72,6 @@ Current fuzzers are
+ 
+ - [fuzzer-kexecdh](fuzzer-kexecdh.c) - test Elliptic Curve Diffie-Hellman key exchange like fuzzer-kexdh.
+   This is testing libtommath ECC routines.
++
++- [fuzzer-kexcurve25519](fuzzer-kexcurve25519.c) - test Curve25519 Elliptic Curve Diffie-Hellman key exchange
++  like fuzzer-kexecdh. This is testing `dropbear_curve25519_scalarmult()` and other libtommath routines.
+diff --git a/LICENSE b/LICENSE
+index c400d94..a4849ff 100644
+--- a/LICENSE
++++ b/LICENSE
+@@ -90,52 +90,25 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ 
+ =====
+ 
+-curve25519-donna:
+-
+-/* Copyright 2008, Google Inc.
+- * All rights reserved.
+- *
+- * Redistribution and use in source and binary forms, with or without
+- * modification, are permitted provided that the following conditions are
+- * met:
+- *
+- *     * Redistributions of source code must retain the above copyright
+- * notice, this list of conditions and the following disclaimer.
+- *     * Redistributions in binary form must reproduce the above
+- * copyright notice, this list of conditions and the following disclaimer
+- * in the documentation and/or other materials provided with the
+- * distribution.
+- *     * Neither the name of Google Inc. nor the names of its
+- * contributors may be used to endorse or promote products derived from
+- * this software without specific prior written permission.
+- *
+- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+- *
+- * curve25519-donna: Curve25519 elliptic curve, public key function
+- *
+- * http://code.google.com/p/curve25519-donna/
+- *
+- * Adam Langley <agl@imperialviolet.org>
+- *
+- * Derived from public domain C code by Daniel J. Bernstein <djb@cr.yp.to>
+- *
+- * More information about curve25519 can be found here
+- *   http://cr.yp.to/ecdh.html
+- *
+- * djb's sample implementation of curve25519 is written in a special assembly
+- * language called qhasm and uses the floating point registers.
+- *
+- * This is, almost, a clean room reimplementation from the curve25519 paper. It
+- * uses many of the tricks described therein. Only the crecip function is taken
+- * from the sample implementation.
+- */
++crypto25519.c:
++crypto26619.h:
++
++Modified TweetNaCl version 20140427, a self-contained public-domain C library.
++https://tweetnacl.cr.yp.to/
++
++Contributors (alphabetical order)
++Daniel J. Bernstein, University of Illinois at Chicago and Technische
++Universiteit Eindhoven
++Bernard van Gastel, Radboud Universiteit Nijmegen
++Wesley Janssen, Radboud Universiteit Nijmegen
++Tanja Lange, Technische Universiteit Eindhoven
++Peter Schwabe, Radboud Universiteit Nijmegen
++Sjaak Smetsers, Radboud Universiteit Nijmegen
++
++Acknowledgments
++This work was supported by the U.S. National Science Foundation under grant
++1018836. "Any opinions, findings, and conclusions or recommendations expressed
++in this material are those of the author(s) and do not necessarily reflect the
++views of the National Science Foundation."
++This work was supported by the Netherlands Organisation for Scientific
++Research (NWO) under grant 639.073.005 and Veni 2013 project 13114.
+diff --git a/Makefile.in b/Makefile.in
+index bc55b7d..aaf7b3b 100644
+--- a/Makefile.in
++++ b/Makefile.in
+@@ -36,8 +36,9 @@ COMMONOBJS=dbutil.o buffer.o dbhelpers.o \
+ 		queue.o \
+ 		atomicio.o compat.o fake-rfc2553.o \
+ 		ltc_prng.o ecc.o ecdsa.o crypto_desc.o \
++		curve25519.o ed25519.o \
+ 		dbmalloc.o \
+-		gensignkey.o gendss.o genrsa.o
++		gensignkey.o gendss.o genrsa.o gened25519.o
+ 
+ SVROBJS=svr-kex.o svr-auth.o sshpty.o \
+ 		svr-authpasswd.o svr-authpubkey.o svr-authpubkeyoptions.o svr-session.o svr-service.o \
+@@ -52,7 +53,7 @@ CLIOBJS=cli-main.o cli-auth.o cli-authpasswd.o cli-kex.o \
+ CLISVROBJS=common-session.o packet.o common-algo.o common-kex.o \
+ 			common-channel.o common-chansession.o termcodes.o loginrec.o \
+ 			tcp-accept.o listener.o process-packet.o dh_groups.o \
+-			common-runopts.o circbuffer.o curve25519-donna.o list.o netio.o
++			common-runopts.o circbuffer.o list.o netio.o
+ 
+ KEYOBJS=dropbearkey.o
+ 
+@@ -264,7 +265,7 @@ tidy:
+ ## Fuzzing targets
+ 
+ # list of fuzz targets
+-FUZZ_TARGETS=fuzzer-preauth fuzzer-pubkey fuzzer-verify fuzzer-preauth_nomaths fuzzer-kexdh fuzzer-kexecdh
++FUZZ_TARGETS=fuzzer-preauth fuzzer-pubkey fuzzer-verify fuzzer-preauth_nomaths fuzzer-kexdh fuzzer-kexecdh fuzzer-kexcurve25519
+ 
+ FUZZER_OPTIONS = $(addsuffix .options, $(FUZZ_TARGETS))
+ 
+@@ -303,6 +304,9 @@ fuzzer-kexdh: fuzzer-kexdh.o fuzz-harness.o
+ fuzzer-kexecdh: fuzzer-kexecdh.o fuzz-harness.o
+ 	$(CXX) $(CXXFLAGS) $@.o $(LDFLAGS) $(svrfuzzobjs) -o $@$(EXEEXT) $(LIBTOM_LIBS) $(LIBS) $(FUZZLIB) @CRYPTLIB@
+ 
++fuzzer-kexcurve25519: fuzzer-kexcurve25519.o fuzz-harness.o
++	$(CXX) $(CXXFLAGS) $@.o $(LDFLAGS) $(svrfuzzobjs) -o $@$(EXEEXT) $(LIBTOM_LIBS) $(LIBS) $(FUZZLIB) @CRYPTLIB@
++
+ fuzzer-%.options: Makefile
+ 	echo "[libfuzzer]"               > $@
+ 	echo "max_len = 50000"          >> $@
+@@ -313,7 +317,9 @@ fuzz-hostkeys:
+ 	dropbearkey -t rsa -f keyr
+ 	dropbearkey -t dss -f keyd
+ 	dropbearkey -t ecdsa -size 256 -f keye
++	dropbearkey -t ed25519 -f keyed25519
+ 	echo > hostkeys.c
+ 	/usr/bin/xxd -i -a keyr >> hostkeys.c
+ 	/usr/bin/xxd -i -a keye >> hostkeys.c
+ 	/usr/bin/xxd -i -a keyd >> hostkeys.c
++	/usr/bin/xxd -i -a keyed25519 >> hostkeys.c
+diff --git a/README b/README
+index b8a6fd2..d197ec7 100644
+--- a/README
++++ b/README
+@@ -55,6 +55,7 @@ To run the server, you need to generate server keys, this is one-off:
+ ./dropbearkey -t rsa -f dropbear_rsa_host_key
+ ./dropbearkey -t dss -f dropbear_dss_host_key
+ ./dropbearkey -t ecdsa -f dropbear_ecdsa_host_key
++./dropbearkey -t ed25519 -f dropbear_ed25519_host_key
+ 
+ or alternatively convert OpenSSH keys to Dropbear:
+ ./dropbearconvert openssh dropbear /etc/ssh/ssh_host_dsa_key dropbear_dss_host_key
+diff --git a/cli-kex.c b/cli-kex.c
+index b02cfc7..7cefb5f 100644
+--- a/cli-kex.c
++++ b/cli-kex.c
+@@ -81,7 +81,7 @@ void send_msg_kexdh_init() {
+ 				}
+ 				cli_ses.curve25519_param = gen_kexcurve25519_param();
+ 			}
+-			buf_putstring(ses.writepayload, (const char*)cli_ses.curve25519_param->pub, CURVE25519_LEN);
++			buf_putstring(ses.writepayload, cli_ses.curve25519_param->pub, CURVE25519_LEN);
+ 			break;
+ #endif
+ 	}
+diff --git a/common-algo.c b/common-algo.c
+index 2f896ab..558aad2 100644
+--- a/common-algo.c
++++ b/common-algo.c
+@@ -222,6 +222,9 @@ algo_type ssh_nocompress[] = {
+ };
+ 
+ algo_type sshhostkey[] = {
++#if DROPBEAR_ED25519
++	{"ssh-ed25519", DROPBEAR_SIGNKEY_ED25519, NULL, 1, NULL},
++#endif
+ #if DROPBEAR_ECDSA
+ #if DROPBEAR_ECC_256
+ 	{"ecdsa-sha2-nistp256", DROPBEAR_SIGNKEY_ECDSA_NISTP256, NULL, 1, NULL},
+diff --git a/common-kex.c b/common-kex.c
+index d4933dd..16b7e27 100644
+--- a/common-kex.c
++++ b/common-kex.c
+@@ -36,6 +36,7 @@
+ #include "dbrandom.h"
+ #include "runopts.h"
+ #include "ecc.h"
++#include "curve25519.h"
+ #include "crypto_desc.h"
+ 
+ static void kexinitialise(void);
+@@ -703,23 +704,18 @@ void kexecdh_comb_key(struct kex_ecdh_param *param, buffer *pub_them,
+ #endif /* DROPBEAR_ECDH */
+ 
+ #if DROPBEAR_CURVE25519
+-struct kex_curve25519_param *gen_kexcurve25519_param () {
++struct kex_curve25519_param *gen_kexcurve25519_param() {
+ 	/* Per http://cr.yp.to/ecdh.html */
+ 	struct kex_curve25519_param *param = m_malloc(sizeof(*param));
+ 	const unsigned char basepoint[32] = {9};
+ 
+ 	genrandom(param->priv, CURVE25519_LEN);
+-	param->priv[0] &= 248;
+-	param->priv[31] &= 127;
+-	param->priv[31] |= 64;
+-
+-	curve25519_donna(param->pub, param->priv, basepoint);
++	dropbear_curve25519_scalarmult(param->pub, param->priv, basepoint);
+ 
+ 	return param;
+ }
+ 
+-void free_kexcurve25519_param(struct kex_curve25519_param *param)
+-{
++void free_kexcurve25519_param(struct kex_curve25519_param *param) {
+ 	m_burn(param->priv, CURVE25519_LEN);
+ 	m_free(param);
+ }
+@@ -736,7 +732,7 @@ void kexcurve25519_comb_key(const struct kex_curve25519_param *param, const buff
+ 		dropbear_exit("Bad curve25519");
+ 	}
+ 
+-	curve25519_donna(out, param->priv, buf_pub_them->data);
++	dropbear_curve25519_scalarmult(out, param->priv, buf_pub_them->data);
+ 
+ 	if (constant_time_memcmp(zeroes, out, CURVE25519_LEN) == 0) {
+ 		dropbear_exit("Bad curve25519");
+diff --git a/curve25519-donna.c b/curve25519-donna.c
+deleted file mode 100644
+index ef0b6d1..0000000
+--- a/curve25519-donna.c
++++ /dev/null
+@@ -1,860 +0,0 @@
+-/* Copyright 2008, Google Inc.
+- * All rights reserved.
+- *
+- * Redistribution and use in source and binary forms, with or without
+- * modification, are permitted provided that the following conditions are
+- * met:
+- *
+- *     * Redistributions of source code must retain the above copyright
+- * notice, this list of conditions and the following disclaimer.
+- *     * Redistributions in binary form must reproduce the above
+- * copyright notice, this list of conditions and the following disclaimer
+- * in the documentation and/or other materials provided with the
+- * distribution.
+- *     * Neither the name of Google Inc. nor the names of its
+- * contributors may be used to endorse or promote products derived from
+- * this software without specific prior written permission.
+- *
+- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+- *
+- * curve25519-donna: Curve25519 elliptic curve, public key function
+- *
+- * http://code.google.com/p/curve25519-donna/
+- *
+- * Adam Langley <agl@imperialviolet.org>
+- *
+- * Derived from public domain C code by Daniel J. Bernstein <djb@cr.yp.to>
+- *
+- * More information about curve25519 can be found here
+- *   http://cr.yp.to/ecdh.html
+- *
+- * djb's sample implementation of curve25519 is written in a special assembly
+- * language called qhasm and uses the floating point registers.
+- *
+- * This is, almost, a clean room reimplementation from the curve25519 paper. It
+- * uses many of the tricks described therein. Only the crecip function is taken
+- * from the sample implementation. */
+-
+-#include <string.h>
+-#include <stdint.h>
+-
+-#ifdef _MSC_VER
+-#define inline __inline
+-#endif
+-
+-typedef uint8_t u8;
+-typedef int32_t s32;
+-typedef int64_t limb;
+-
+-/* Field element representation:
+- *
+- * Field elements are written as an array of signed, 64-bit limbs, least
+- * significant first. The value of the field element is:
+- *   x[0] + 2^26·x[1] + x^51·x[2] + 2^102·x[3] + ...
+- *
+- * i.e. the limbs are 26, 25, 26, 25, ... bits wide. */
+-
+-/* Sum two numbers: output += in */
+-static void fsum(limb *output, const limb *in) {
+-  unsigned i;
+-  for (i = 0; i < 10; i += 2) {
+-    output[0+i] = output[0+i] + in[0+i];
+-    output[1+i] = output[1+i] + in[1+i];
+-  }
+-}
+-
+-/* Find the difference of two numbers: output = in - output
+- * (note the order of the arguments!). */
+-static void fdifference(limb *output, const limb *in) {
+-  unsigned i;
+-  for (i = 0; i < 10; ++i) {
+-    output[i] = in[i] - output[i];
+-  }
+-}
+-
+-/* Multiply a number by a scalar: output = in * scalar */
+-static void fscalar_product(limb *output, const limb *in, const limb scalar) {
+-  unsigned i;
+-  for (i = 0; i < 10; ++i) {
+-    output[i] = in[i] * scalar;
+-  }
+-}
+-
+-/* Multiply two numbers: output = in2 * in
+- *
+- * output must be distinct to both inputs. The inputs are reduced coefficient
+- * form, the output is not.
+- *
+- * output[x] <= 14 * the largest product of the input limbs. */
+-static void fproduct(limb *output, const limb *in2, const limb *in) {
+-  output[0] =       ((limb) ((s32) in2[0])) * ((s32) in[0]);
+-  output[1] =       ((limb) ((s32) in2[0])) * ((s32) in[1]) +
+-                    ((limb) ((s32) in2[1])) * ((s32) in[0]);
+-  output[2] =  2 *  ((limb) ((s32) in2[1])) * ((s32) in[1]) +
+-                    ((limb) ((s32) in2[0])) * ((s32) in[2]) +
+-                    ((limb) ((s32) in2[2])) * ((s32) in[0]);
+-  output[3] =       ((limb) ((s32) in2[1])) * ((s32) in[2]) +
+-                    ((limb) ((s32) in2[2])) * ((s32) in[1]) +
+-                    ((limb) ((s32) in2[0])) * ((s32) in[3]) +
+-                    ((limb) ((s32) in2[3])) * ((s32) in[0]);
+-  output[4] =       ((limb) ((s32) in2[2])) * ((s32) in[2]) +
+-               2 * (((limb) ((s32) in2[1])) * ((s32) in[3]) +
+-                    ((limb) ((s32) in2[3])) * ((s32) in[1])) +
+-                    ((limb) ((s32) in2[0])) * ((s32) in[4]) +
+-                    ((limb) ((s32) in2[4])) * ((s32) in[0]);
+-  output[5] =       ((limb) ((s32) in2[2])) * ((s32) in[3]) +
+-                    ((limb) ((s32) in2[3])) * ((s32) in[2]) +
+-                    ((limb) ((s32) in2[1])) * ((s32) in[4]) +
+-                    ((limb) ((s32) in2[4])) * ((s32) in[1]) +
+-                    ((limb) ((s32) in2[0])) * ((s32) in[5]) +
+-                    ((limb) ((s32) in2[5])) * ((s32) in[0]);
+-  output[6] =  2 * (((limb) ((s32) in2[3])) * ((s32) in[3]) +
+-                    ((limb) ((s32) in2[1])) * ((s32) in[5]) +
+-                    ((limb) ((s32) in2[5])) * ((s32) in[1])) +
+-                    ((limb) ((s32) in2[2])) * ((s32) in[4]) +
+-                    ((limb) ((s32) in2[4])) * ((s32) in[2]) +
+-                    ((limb) ((s32) in2[0])) * ((s32) in[6]) +
+-                    ((limb) ((s32) in2[6])) * ((s32) in[0]);
+-  output[7] =       ((limb) ((s32) in2[3])) * ((s32) in[4]) +
+-                    ((limb) ((s32) in2[4])) * ((s32) in[3]) +
+-                    ((limb) ((s32) in2[2])) * ((s32) in[5]) +
+-                    ((limb) ((s32) in2[5])) * ((s32) in[2]) +
+-                    ((limb) ((s32) in2[1])) * ((s32) in[6]) +
+-                    ((limb) ((s32) in2[6])) * ((s32) in[1]) +
+-                    ((limb) ((s32) in2[0])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in2[7])) * ((s32) in[0]);
+-  output[8] =       ((limb) ((s32) in2[4])) * ((s32) in[4]) +
+-               2 * (((limb) ((s32) in2[3])) * ((s32) in[5]) +
+-                    ((limb) ((s32) in2[5])) * ((s32) in[3]) +
+-                    ((limb) ((s32) in2[1])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in2[7])) * ((s32) in[1])) +
+-                    ((limb) ((s32) in2[2])) * ((s32) in[6]) +
+-                    ((limb) ((s32) in2[6])) * ((s32) in[2]) +
+-                    ((limb) ((s32) in2[0])) * ((s32) in[8]) +
+-                    ((limb) ((s32) in2[8])) * ((s32) in[0]);
+-  output[9] =       ((limb) ((s32) in2[4])) * ((s32) in[5]) +
+-                    ((limb) ((s32) in2[5])) * ((s32) in[4]) +
+-                    ((limb) ((s32) in2[3])) * ((s32) in[6]) +
+-                    ((limb) ((s32) in2[6])) * ((s32) in[3]) +
+-                    ((limb) ((s32) in2[2])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in2[7])) * ((s32) in[2]) +
+-                    ((limb) ((s32) in2[1])) * ((s32) in[8]) +
+-                    ((limb) ((s32) in2[8])) * ((s32) in[1]) +
+-                    ((limb) ((s32) in2[0])) * ((s32) in[9]) +
+-                    ((limb) ((s32) in2[9])) * ((s32) in[0]);
+-  output[10] = 2 * (((limb) ((s32) in2[5])) * ((s32) in[5]) +
+-                    ((limb) ((s32) in2[3])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in2[7])) * ((s32) in[3]) +
+-                    ((limb) ((s32) in2[1])) * ((s32) in[9]) +
+-                    ((limb) ((s32) in2[9])) * ((s32) in[1])) +
+-                    ((limb) ((s32) in2[4])) * ((s32) in[6]) +
+-                    ((limb) ((s32) in2[6])) * ((s32) in[4]) +
+-                    ((limb) ((s32) in2[2])) * ((s32) in[8]) +
+-                    ((limb) ((s32) in2[8])) * ((s32) in[2]);
+-  output[11] =      ((limb) ((s32) in2[5])) * ((s32) in[6]) +
+-                    ((limb) ((s32) in2[6])) * ((s32) in[5]) +
+-                    ((limb) ((s32) in2[4])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in2[7])) * ((s32) in[4]) +
+-                    ((limb) ((s32) in2[3])) * ((s32) in[8]) +
+-                    ((limb) ((s32) in2[8])) * ((s32) in[3]) +
+-                    ((limb) ((s32) in2[2])) * ((s32) in[9]) +
+-                    ((limb) ((s32) in2[9])) * ((s32) in[2]);
+-  output[12] =      ((limb) ((s32) in2[6])) * ((s32) in[6]) +
+-               2 * (((limb) ((s32) in2[5])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in2[7])) * ((s32) in[5]) +
+-                    ((limb) ((s32) in2[3])) * ((s32) in[9]) +
+-                    ((limb) ((s32) in2[9])) * ((s32) in[3])) +
+-                    ((limb) ((s32) in2[4])) * ((s32) in[8]) +
+-                    ((limb) ((s32) in2[8])) * ((s32) in[4]);
+-  output[13] =      ((limb) ((s32) in2[6])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in2[7])) * ((s32) in[6]) +
+-                    ((limb) ((s32) in2[5])) * ((s32) in[8]) +
+-                    ((limb) ((s32) in2[8])) * ((s32) in[5]) +
+-                    ((limb) ((s32) in2[4])) * ((s32) in[9]) +
+-                    ((limb) ((s32) in2[9])) * ((s32) in[4]);
+-  output[14] = 2 * (((limb) ((s32) in2[7])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in2[5])) * ((s32) in[9]) +
+-                    ((limb) ((s32) in2[9])) * ((s32) in[5])) +
+-                    ((limb) ((s32) in2[6])) * ((s32) in[8]) +
+-                    ((limb) ((s32) in2[8])) * ((s32) in[6]);
+-  output[15] =      ((limb) ((s32) in2[7])) * ((s32) in[8]) +
+-                    ((limb) ((s32) in2[8])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in2[6])) * ((s32) in[9]) +
+-                    ((limb) ((s32) in2[9])) * ((s32) in[6]);
+-  output[16] =      ((limb) ((s32) in2[8])) * ((s32) in[8]) +
+-               2 * (((limb) ((s32) in2[7])) * ((s32) in[9]) +
+-                    ((limb) ((s32) in2[9])) * ((s32) in[7]));
+-  output[17] =      ((limb) ((s32) in2[8])) * ((s32) in[9]) +
+-                    ((limb) ((s32) in2[9])) * ((s32) in[8]);
+-  output[18] = 2 *  ((limb) ((s32) in2[9])) * ((s32) in[9]);
+-}
+-
+-/* Reduce a long form to a short form by taking the input mod 2^255 - 19.
+- *
+- * On entry: |output[i]| < 14*2^54
+- * On exit: |output[0..8]| < 280*2^54 */
+-static void freduce_degree(limb *output) {
+-  /* Each of these shifts and adds ends up multiplying the value by 19.
+-   *
+-   * For output[0..8], the absolute entry value is < 14*2^54 and we add, at
+-   * most, 19*14*2^54 thus, on exit, |output[0..8]| < 280*2^54. */
+-  output[8] += output[18] << 4;
+-  output[8] += output[18] << 1;
+-  output[8] += output[18];
+-  output[7] += output[17] << 4;
+-  output[7] += output[17] << 1;
+-  output[7] += output[17];
+-  output[6] += output[16] << 4;
+-  output[6] += output[16] << 1;
+-  output[6] += output[16];
+-  output[5] += output[15] << 4;
+-  output[5] += output[15] << 1;
+-  output[5] += output[15];
+-  output[4] += output[14] << 4;
+-  output[4] += output[14] << 1;
+-  output[4] += output[14];
+-  output[3] += output[13] << 4;
+-  output[3] += output[13] << 1;
+-  output[3] += output[13];
+-  output[2] += output[12] << 4;
+-  output[2] += output[12] << 1;
+-  output[2] += output[12];
+-  output[1] += output[11] << 4;
+-  output[1] += output[11] << 1;
+-  output[1] += output[11];
+-  output[0] += output[10] << 4;
+-  output[0] += output[10] << 1;
+-  output[0] += output[10];
+-}
+-
+-#if (-1 & 3) != 3
+-#error "This code only works on a two's complement system"
+-#endif
+-
+-/* return v / 2^26, using only shifts and adds.
+- *
+- * On entry: v can take any value. */
+-static inline limb
+-div_by_2_26(const limb v)
+-{
+-  /* High word of v; no shift needed. */
+-  const uint32_t highword = (uint32_t) (((uint64_t) v) >> 32);
+-  /* Set to all 1s if v was negative; else set to 0s. */
+-  const int32_t sign = ((int32_t) highword) >> 31;
+-  /* Set to 0x3ffffff if v was negative; else set to 0. */
+-  const int32_t roundoff = ((uint32_t) sign) >> 6;
+-  /* Should return v / (1<<26) */
+-  return (v + roundoff) >> 26;
+-}
+-
+-/* return v / (2^25), using only shifts and adds.
+- *
+- * On entry: v can take any value. */
+-static inline limb
+-div_by_2_25(const limb v)
+-{
+-  /* High word of v; no shift needed*/
+-  const uint32_t highword = (uint32_t) (((uint64_t) v) >> 32);
+-  /* Set to all 1s if v was negative; else set to 0s. */
+-  const int32_t sign = ((int32_t) highword) >> 31;
+-  /* Set to 0x1ffffff if v was negative; else set to 0. */
+-  const int32_t roundoff = ((uint32_t) sign) >> 7;
+-  /* Should return v / (1<<25) */
+-  return (v + roundoff) >> 25;
+-}
+-
+-/* Reduce all coefficients of the short form input so that |x| < 2^26.
+- *
+- * On entry: |output[i]| < 280*2^54 */
+-static void freduce_coefficients(limb *output) {
+-  unsigned i;
+-
+-  output[10] = 0;
+-
+-  for (i = 0; i < 10; i += 2) {
+-    limb over = div_by_2_26(output[i]);
+-    /* The entry condition (that |output[i]| < 280*2^54) means that over is, at
+-     * most, 280*2^28 in the first iteration of this loop. This is added to the
+-     * next limb and we can approximate the resulting bound of that limb by
+-     * 281*2^54. */
+-    output[i] -= over << 26;
+-    output[i+1] += over;
+-
+-    /* For the first iteration, |output[i+1]| < 281*2^54, thus |over| <
+-     * 281*2^29. When this is added to the next limb, the resulting bound can
+-     * be approximated as 281*2^54.
+-     *
+-     * For subsequent iterations of the loop, 281*2^54 remains a conservative
+-     * bound and no overflow occurs. */
+-    over = div_by_2_25(output[i+1]);
+-    output[i+1] -= over << 25;
+-    output[i+2] += over;
+-  }
+-  /* Now |output[10]| < 281*2^29 and all other coefficients are reduced. */
+-  output[0] += output[10] << 4;
+-  output[0] += output[10] << 1;
+-  output[0] += output[10];
+-
+-  output[10] = 0;
+-
+-  /* Now output[1..9] are reduced, and |output[0]| < 2^26 + 19*281*2^29
+-   * So |over| will be no more than 2^16. */
+-  {
+-    limb over = div_by_2_26(output[0]);
+-    output[0] -= over << 26;
+-    output[1] += over;
+-  }
+-
+-  /* Now output[0,2..9] are reduced, and |output[1]| < 2^25 + 2^16 < 2^26. The
+-   * bound on |output[1]| is sufficient to meet our needs. */
+-}
+-
+-/* A helpful wrapper around fproduct: output = in * in2.
+- *
+- * On entry: |in[i]| < 2^27 and |in2[i]| < 2^27.
+- *
+- * output must be distinct to both inputs. The output is reduced degree
+- * (indeed, one need only provide storage for 10 limbs) and |output[i]| < 2^26. */
+-static void
+-fmul(limb *output, const limb *in, const limb *in2) {
+-  limb t[19];
+-  fproduct(t, in, in2);
+-  /* |t[i]| < 14*2^54 */
+-  freduce_degree(t);
+-  freduce_coefficients(t);
+-  /* |t[i]| < 2^26 */
+-  memcpy(output, t, sizeof(limb) * 10);
+-}
+-
+-/* Square a number: output = in**2
+- *
+- * output must be distinct from the input. The inputs are reduced coefficient
+- * form, the output is not.
+- *
+- * output[x] <= 14 * the largest product of the input limbs. */
+-static void fsquare_inner(limb *output, const limb *in) {
+-  output[0] =       ((limb) ((s32) in[0])) * ((s32) in[0]);
+-  output[1] =  2 *  ((limb) ((s32) in[0])) * ((s32) in[1]);
+-  output[2] =  2 * (((limb) ((s32) in[1])) * ((s32) in[1]) +
+-                    ((limb) ((s32) in[0])) * ((s32) in[2]));
+-  output[3] =  2 * (((limb) ((s32) in[1])) * ((s32) in[2]) +
+-                    ((limb) ((s32) in[0])) * ((s32) in[3]));
+-  output[4] =       ((limb) ((s32) in[2])) * ((s32) in[2]) +
+-               4 *  ((limb) ((s32) in[1])) * ((s32) in[3]) +
+-               2 *  ((limb) ((s32) in[0])) * ((s32) in[4]);
+-  output[5] =  2 * (((limb) ((s32) in[2])) * ((s32) in[3]) +
+-                    ((limb) ((s32) in[1])) * ((s32) in[4]) +
+-                    ((limb) ((s32) in[0])) * ((s32) in[5]));
+-  output[6] =  2 * (((limb) ((s32) in[3])) * ((s32) in[3]) +
+-                    ((limb) ((s32) in[2])) * ((s32) in[4]) +
+-                    ((limb) ((s32) in[0])) * ((s32) in[6]) +
+-               2 *  ((limb) ((s32) in[1])) * ((s32) in[5]));
+-  output[7] =  2 * (((limb) ((s32) in[3])) * ((s32) in[4]) +
+-                    ((limb) ((s32) in[2])) * ((s32) in[5]) +
+-                    ((limb) ((s32) in[1])) * ((s32) in[6]) +
+-                    ((limb) ((s32) in[0])) * ((s32) in[7]));
+-  output[8] =       ((limb) ((s32) in[4])) * ((s32) in[4]) +
+-               2 * (((limb) ((s32) in[2])) * ((s32) in[6]) +
+-                    ((limb) ((s32) in[0])) * ((s32) in[8]) +
+-               2 * (((limb) ((s32) in[1])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in[3])) * ((s32) in[5])));
+-  output[9] =  2 * (((limb) ((s32) in[4])) * ((s32) in[5]) +
+-                    ((limb) ((s32) in[3])) * ((s32) in[6]) +
+-                    ((limb) ((s32) in[2])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in[1])) * ((s32) in[8]) +
+-                    ((limb) ((s32) in[0])) * ((s32) in[9]));
+-  output[10] = 2 * (((limb) ((s32) in[5])) * ((s32) in[5]) +
+-                    ((limb) ((s32) in[4])) * ((s32) in[6]) +
+-                    ((limb) ((s32) in[2])) * ((s32) in[8]) +
+-               2 * (((limb) ((s32) in[3])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in[1])) * ((s32) in[9])));
+-  output[11] = 2 * (((limb) ((s32) in[5])) * ((s32) in[6]) +
+-                    ((limb) ((s32) in[4])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in[3])) * ((s32) in[8]) +
+-                    ((limb) ((s32) in[2])) * ((s32) in[9]));
+-  output[12] =      ((limb) ((s32) in[6])) * ((s32) in[6]) +
+-               2 * (((limb) ((s32) in[4])) * ((s32) in[8]) +
+-               2 * (((limb) ((s32) in[5])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in[3])) * ((s32) in[9])));
+-  output[13] = 2 * (((limb) ((s32) in[6])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in[5])) * ((s32) in[8]) +
+-                    ((limb) ((s32) in[4])) * ((s32) in[9]));
+-  output[14] = 2 * (((limb) ((s32) in[7])) * ((s32) in[7]) +
+-                    ((limb) ((s32) in[6])) * ((s32) in[8]) +
+-               2 *  ((limb) ((s32) in[5])) * ((s32) in[9]));
+-  output[15] = 2 * (((limb) ((s32) in[7])) * ((s32) in[8]) +
+-                    ((limb) ((s32) in[6])) * ((s32) in[9]));
+-  output[16] =      ((limb) ((s32) in[8])) * ((s32) in[8]) +
+-               4 *  ((limb) ((s32) in[7])) * ((s32) in[9]);
+-  output[17] = 2 *  ((limb) ((s32) in[8])) * ((s32) in[9]);
+-  output[18] = 2 *  ((limb) ((s32) in[9])) * ((s32) in[9]);
+-}
+-
+-/* fsquare sets output = in^2.
+- *
+- * On entry: The |in| argument is in reduced coefficients form and |in[i]| <
+- * 2^27.
+- *
+- * On exit: The |output| argument is in reduced coefficients form (indeed, one
+- * need only provide storage for 10 limbs) and |out[i]| < 2^26. */
+-static void
+-fsquare(limb *output, const limb *in) {
+-  limb t[19];
+-  fsquare_inner(t, in);
+-  /* |t[i]| < 14*2^54 because the largest product of two limbs will be <
+-   * 2^(27+27) and fsquare_inner adds together, at most, 14 of those
+-   * products. */
+-  freduce_degree(t);
+-  freduce_coefficients(t);
+-  /* |t[i]| < 2^26 */
+-  memcpy(output, t, sizeof(limb) * 10);
+-}
+-
+-/* Take a little-endian, 32-byte number and expand it into polynomial form */
+-static void
+-fexpand(limb *output, const u8 *input) {
+-#define F(n,start,shift,mask) \
+-  output[n] = ((((limb) input[start + 0]) | \
+-                ((limb) input[start + 1]) << 8 | \
+-                ((limb) input[start + 2]) << 16 | \
+-                ((limb) input[start + 3]) << 24) >> shift) & mask;
+-  F(0, 0, 0, 0x3ffffff);
+-  F(1, 3, 2, 0x1ffffff);
+-  F(2, 6, 3, 0x3ffffff);
+-  F(3, 9, 5, 0x1ffffff);
+-  F(4, 12, 6, 0x3ffffff);
+-  F(5, 16, 0, 0x1ffffff);
+-  F(6, 19, 1, 0x3ffffff);
+-  F(7, 22, 3, 0x1ffffff);
+-  F(8, 25, 4, 0x3ffffff);
+-  F(9, 28, 6, 0x1ffffff);
+-#undef F
+-}
+-
+-#if (-32 >> 1) != -16
+-#error "This code only works when >> does sign-extension on negative numbers"
+-#endif
+-
+-/* s32_eq returns 0xffffffff iff a == b and zero otherwise. */
+-static s32 s32_eq(s32 a, s32 b) {
+-  a = ~(a ^ b);
+-  a &= a << 16;
+-  a &= a << 8;
+-  a &= a << 4;
+-  a &= a << 2;
+-  a &= a << 1;
+-  return a >> 31;
+-}
+-
+-/* s32_gte returns 0xffffffff if a >= b and zero otherwise, where a and b are
+- * both non-negative. */
+-static s32 s32_gte(s32 a, s32 b) {
+-  a -= b;
+-  /* a >= 0 iff a >= b. */
+-  return ~(a >> 31);
+-}
+-
+-/* Take a fully reduced polynomial form number and contract it into a
+- * little-endian, 32-byte array.
+- *
+- * On entry: |input_limbs[i]| < 2^26 */
+-static void
+-fcontract(u8 *output, limb *input_limbs) {
+-  int i;
+-  int j;
+-  s32 input[10];
+-  s32 mask;
+-
+-  /* |input_limbs[i]| < 2^26, so it's valid to convert to an s32. */
+-  for (i = 0; i < 10; i++) {
+-    input[i] = input_limbs[i];
+-  }
+-
+-  for (j = 0; j < 2; ++j) {
+-    for (i = 0; i < 9; ++i) {
+-      if ((i & 1) == 1) {
+-        /* This calculation is a time-invariant way to make input[i]
+-         * non-negative by borrowing from the next-larger limb. */
+-        const s32 mask = input[i] >> 31;
+-        const s32 carry = -((input[i] & mask) >> 25);
+-        input[i] = input[i] + (carry << 25);
+-        input[i+1] = input[i+1] - carry;
+-      } else {
+-        const s32 mask = input[i] >> 31;
+-        const s32 carry = -((input[i] & mask) >> 26);
+-        input[i] = input[i] + (carry << 26);
+-        input[i+1] = input[i+1] - carry;
+-      }
+-    }
+-
+-    /* There's no greater limb for input[9] to borrow from, but we can multiply
+-     * by 19 and borrow from input[0], which is valid mod 2^255-19. */
+-    {
+-      const s32 mask = input[9] >> 31;
+-      const s32 carry = -((input[9] & mask) >> 25);
+-      input[9] = input[9] + (carry << 25);
+-      input[0] = input[0] - (carry * 19);
+-    }
+-
+-    /* After the first iteration, input[1..9] are non-negative and fit within
+-     * 25 or 26 bits, depending on position. However, input[0] may be
+-     * negative. */
+-  }
+-
+-  /* The first borrow-propagation pass above ended with every limb
+-     except (possibly) input[0] non-negative.
+-
+-     If input[0] was negative after the first pass, then it was because of a
+-     carry from input[9]. On entry, input[9] < 2^26 so the carry was, at most,
+-     one, since (2**26-1) >> 25 = 1. Thus input[0] >= -19.
+-
+-     In the second pass, each limb is decreased by at most one. Thus the second
+-     borrow-propagation pass could only have wrapped around to decrease
+-     input[0] again if the first pass left input[0] negative *and* input[1]
+-     through input[9] were all zero.  In that case, input[1] is now 2^25 - 1,
+-     and this last borrow-propagation step will leave input[1] non-negative. */
+-  {
+-    const s32 mask = input[0] >> 31;
+-    const s32 carry = -((input[0] & mask) >> 26);
+-    input[0] = input[0] + (carry << 26);
+-    input[1] = input[1] - carry;
+-  }
+-
+-  /* All input[i] are now non-negative. However, there might be values between
+-   * 2^25 and 2^26 in a limb which is, nominally, 25 bits wide. */
+-  for (j = 0; j < 2; j++) {
+-    for (i = 0; i < 9; i++) {
+-      if ((i & 1) == 1) {
+-        const s32 carry = input[i] >> 25;
+-        input[i] &= 0x1ffffff;
+-        input[i+1] += carry;
+-      } else {
+-        const s32 carry = input[i] >> 26;
+-        input[i] &= 0x3ffffff;
+-        input[i+1] += carry;
+-      }
+-    }
+-
+-    {
+-      const s32 carry = input[9] >> 25;
+-      input[9] &= 0x1ffffff;
+-      input[0] += 19*carry;
+-    }
+-  }
+-
+-  /* If the first carry-chain pass, just above, ended up with a carry from
+-   * input[9], and that caused input[0] to be out-of-bounds, then input[0] was
+-   * < 2^26 + 2*19, because the carry was, at most, two.
+-   *
+-   * If the second pass carried from input[9] again then input[0] is < 2*19 and
+-   * the input[9] -> input[0] carry didn't push input[0] out of bounds. */
+-
+-  /* It still remains the case that input might be between 2^255-19 and 2^255.
+-   * In this case, input[1..9] must take their maximum value and input[0] must
+-   * be >= (2^255-19) & 0x3ffffff, which is 0x3ffffed. */
+-  mask = s32_gte(input[0], 0x3ffffed);
+-  for (i = 1; i < 10; i++) {
+-    if ((i & 1) == 1) {
+-      mask &= s32_eq(input[i], 0x1ffffff);
+-    } else {
+-      mask &= s32_eq(input[i], 0x3ffffff);
+-    }
+-  }
+-
+-  /* mask is either 0xffffffff (if input >= 2^255-19) and zero otherwise. Thus
+-   * this conditionally subtracts 2^255-19. */
+-  input[0] -= mask & 0x3ffffed;
+-
+-  for (i = 1; i < 10; i++) {
+-    if ((i & 1) == 1) {
+-      input[i] -= mask & 0x1ffffff;
+-    } else {
+-      input[i] -= mask & 0x3ffffff;
+-    }
+-  }
+-
+-  input[1] <<= 2;
+-  input[2] <<= 3;
+-  input[3] <<= 5;
+-  input[4] <<= 6;
+-  input[6] <<= 1;
+-  input[7] <<= 3;
+-  input[8] <<= 4;
+-  input[9] <<= 6;
+-#define F(i, s) \
+-  output[s+0] |=  input[i] & 0xff; \
+-  output[s+1]  = (input[i] >> 8) & 0xff; \
+-  output[s+2]  = (input[i] >> 16) & 0xff; \
+-  output[s+3]  = (input[i] >> 24) & 0xff;
+-  output[0] = 0;
+-  output[16] = 0;
+-  F(0,0);
+-  F(1,3);
+-  F(2,6);
+-  F(3,9);
+-  F(4,12);
+-  F(5,16);
+-  F(6,19);
+-  F(7,22);
+-  F(8,25);
+-  F(9,28);
+-#undef F
+-}
+-
+-/* Input: Q, Q', Q-Q'
+- * Output: 2Q, Q+Q'
+- *
+- *   x2 z3: long form
+- *   x3 z3: long form
+- *   x z: short form, destroyed
+- *   xprime zprime: short form, destroyed
+- *   qmqp: short form, preserved
+- *
+- * On entry and exit, the absolute value of the limbs of all inputs and outputs
+- * are < 2^26. */
+-static void fmonty(limb *x2, limb *z2,  /* output 2Q */
+-                   limb *x3, limb *z3,  /* output Q + Q' */
+-                   limb *x, limb *z,    /* input Q */
+-                   limb *xprime, limb *zprime,  /* input Q' */
+-                   const limb *qmqp /* input Q - Q' */) {
+-  limb origx[10], origxprime[10], zzz[19], xx[19], zz[19], xxprime[19],
+-        zzprime[19], zzzprime[19], xxxprime[19];
+-
+-  memcpy(origx, x, 10 * sizeof(limb));
+-  fsum(x, z);
+-  /* |x[i]| < 2^27 */
+-  fdifference(z, origx);  /* does x - z */
+-  /* |z[i]| < 2^27 */
+-
+-  memcpy(origxprime, xprime, sizeof(limb) * 10);
+-  fsum(xprime, zprime);
+-  /* |xprime[i]| < 2^27 */
+-  fdifference(zprime, origxprime);
+-  /* |zprime[i]| < 2^27 */
+-  fproduct(xxprime, xprime, z);
+-  /* |xxprime[i]| < 14*2^54: the largest product of two limbs will be <
+-   * 2^(27+27) and fproduct adds together, at most, 14 of those products.
+-   * (Approximating that to 2^58 doesn't work out.) */
+-  fproduct(zzprime, x, zprime);
+-  /* |zzprime[i]| < 14*2^54 */
+-  freduce_degree(xxprime);
+-  freduce_coefficients(xxprime);
+-  /* |xxprime[i]| < 2^26 */
+-  freduce_degree(zzprime);
+-  freduce_coefficients(zzprime);
+-  /* |zzprime[i]| < 2^26 */
+-  memcpy(origxprime, xxprime, sizeof(limb) * 10);
+-  fsum(xxprime, zzprime);
+-  /* |xxprime[i]| < 2^27 */
+-  fdifference(zzprime, origxprime);
+-  /* |zzprime[i]| < 2^27 */
+-  fsquare(xxxprime, xxprime);
+-  /* |xxxprime[i]| < 2^26 */
+-  fsquare(zzzprime, zzprime);
+-  /* |zzzprime[i]| < 2^26 */
+-  fproduct(zzprime, zzzprime, qmqp);
+-  /* |zzprime[i]| < 14*2^52 */
+-  freduce_degree(zzprime);
+-  freduce_coefficients(zzprime);
+-  /* |zzprime[i]| < 2^26 */
+-  memcpy(x3, xxxprime, sizeof(limb) * 10);
+-  memcpy(z3, zzprime, sizeof(limb) * 10);
+-
+-  fsquare(xx, x);
+-  /* |xx[i]| < 2^26 */
+-  fsquare(zz, z);
+-  /* |zz[i]| < 2^26 */
+-  fproduct(x2, xx, zz);
+-  /* |x2[i]| < 14*2^52 */
+-  freduce_degree(x2);
+-  freduce_coefficients(x2);
+-  /* |x2[i]| < 2^26 */
+-  fdifference(zz, xx);  /* does zz = xx - zz */
+-  /* |zz[i]| < 2^27 */
+-  memset(zzz + 10, 0, sizeof(limb) * 9);
+-  fscalar_product(zzz, zz, 121665);
+-  /* |zzz[i]| < 2^(27+17) */
+-  /* No need to call freduce_degree here:
+-     fscalar_product doesn't increase the degree of its input. */
+-  freduce_coefficients(zzz);
+-  /* |zzz[i]| < 2^26 */
+-  fsum(zzz, xx);
+-  /* |zzz[i]| < 2^27 */
+-  fproduct(z2, zz, zzz);
+-  /* |z2[i]| < 14*2^(26+27) */
+-  freduce_degree(z2);
+-  freduce_coefficients(z2);
+-  /* |z2|i| < 2^26 */
+-}
+-
+-/* Conditionally swap two reduced-form limb arrays if 'iswap' is 1, but leave
+- * them unchanged if 'iswap' is 0.  Runs in data-invariant time to avoid
+- * side-channel attacks.
+- *
+- * NOTE that this function requires that 'iswap' be 1 or 0; other values give
+- * wrong results.  Also, the two limb arrays must be in reduced-coefficient,
+- * reduced-degree form: the values in a[10..19] or b[10..19] aren't swapped,
+- * and all all values in a[0..9],b[0..9] must have magnitude less than
+- * INT32_MAX. */
+-static void
+-swap_conditional(limb a[19], limb b[19], limb iswap) {
+-  unsigned i;
+-  const s32 swap = (s32) -iswap;
+-
+-  for (i = 0; i < 10; ++i) {
+-    const s32 x = swap & ( ((s32)a[i]) ^ ((s32)b[i]) );
+-    a[i] = ((s32)a[i]) ^ x;
+-    b[i] = ((s32)b[i]) ^ x;
+-  }
+-}
+-
+-/* Calculates nQ where Q is the x-coordinate of a point on the curve
+- *
+- *   resultx/resultz: the x coordinate of the resulting curve point (short form)
+- *   n: a little endian, 32-byte number
+- *   q: a point of the curve (short form) */
+-static void
+-cmult(limb *resultx, limb *resultz, const u8 *n, const limb *q) {
+-  limb a[19] = {0}, b[19] = {1}, c[19] = {1}, d[19] = {0};
+-  limb *nqpqx = a, *nqpqz = b, *nqx = c, *nqz = d, *t;
+-  limb e[19] = {0}, f[19] = {1}, g[19] = {0}, h[19] = {1};
+-  limb *nqpqx2 = e, *nqpqz2 = f, *nqx2 = g, *nqz2 = h;
+-
+-  unsigned i, j;
+-
+-  memcpy(nqpqx, q, sizeof(limb) * 10);
+-
+-  for (i = 0; i < 32; ++i) {
+-    u8 byte = n[31 - i];
+-    for (j = 0; j < 8; ++j) {
+-      const limb bit = byte >> 7;
+-
+-      swap_conditional(nqx, nqpqx, bit);
+-      swap_conditional(nqz, nqpqz, bit);
+-      fmonty(nqx2, nqz2,
+-             nqpqx2, nqpqz2,
+-             nqx, nqz,
+-             nqpqx, nqpqz,
+-             q);
+-      swap_conditional(nqx2, nqpqx2, bit);
+-      swap_conditional(nqz2, nqpqz2, bit);
+-
+-      t = nqx;
+-      nqx = nqx2;
+-      nqx2 = t;
+-      t = nqz;
+-      nqz = nqz2;
+-      nqz2 = t;
+-      t = nqpqx;
+-      nqpqx = nqpqx2;
+-      nqpqx2 = t;
+-      t = nqpqz;
+-      nqpqz = nqpqz2;
+-      nqpqz2 = t;
+-
+-      byte <<= 1;
+-    }
+-  }
+-
+-  memcpy(resultx, nqx, sizeof(limb) * 10);
+-  memcpy(resultz, nqz, sizeof(limb) * 10);
+-}
+-
+-/* -----------------------------------------------------------------------------
+- * Shamelessly copied from djb's code
+- * ----------------------------------------------------------------------------- */
+-static void
+-crecip(limb *out, const limb *z) {
+-  limb z2[10];
+-  limb z9[10];
+-  limb z11[10];
+-  limb z2_5_0[10];
+-  limb z2_10_0[10];
+-  limb z2_20_0[10];
+-  limb z2_50_0[10];
+-  limb z2_100_0[10];
+-  limb t0[10];
+-  limb t1[10];
+-  int i;
+-
+-  /* 2 */ fsquare(z2,z);
+-  /* 4 */ fsquare(t1,z2);
+-  /* 8 */ fsquare(t0,t1);
+-  /* 9 */ fmul(z9,t0,z);
+-  /* 11 */ fmul(z11,z9,z2);
+-  /* 22 */ fsquare(t0,z11);
+-  /* 2^5 - 2^0 = 31 */ fmul(z2_5_0,t0,z9);
+-
+-  /* 2^6 - 2^1 */ fsquare(t0,z2_5_0);
+-  /* 2^7 - 2^2 */ fsquare(t1,t0);
+-  /* 2^8 - 2^3 */ fsquare(t0,t1);
+-  /* 2^9 - 2^4 */ fsquare(t1,t0);
+-  /* 2^10 - 2^5 */ fsquare(t0,t1);
+-  /* 2^10 - 2^0 */ fmul(z2_10_0,t0,z2_5_0);
+-
+-  /* 2^11 - 2^1 */ fsquare(t0,z2_10_0);
+-  /* 2^12 - 2^2 */ fsquare(t1,t0);
+-  /* 2^20 - 2^10 */ for (i = 2;i < 10;i += 2) { fsquare(t0,t1); fsquare(t1,t0); }
+-  /* 2^20 - 2^0 */ fmul(z2_20_0,t1,z2_10_0);
+-
+-  /* 2^21 - 2^1 */ fsquare(t0,z2_20_0);
+-  /* 2^22 - 2^2 */ fsquare(t1,t0);
+-  /* 2^40 - 2^20 */ for (i = 2;i < 20;i += 2) { fsquare(t0,t1); fsquare(t1,t0); }
+-  /* 2^40 - 2^0 */ fmul(t0,t1,z2_20_0);
+-
+-  /* 2^41 - 2^1 */ fsquare(t1,t0);
+-  /* 2^42 - 2^2 */ fsquare(t0,t1);
+-  /* 2^50 - 2^10 */ for (i = 2;i < 10;i += 2) { fsquare(t1,t0); fsquare(t0,t1); }
+-  /* 2^50 - 2^0 */ fmul(z2_50_0,t0,z2_10_0);
+-
+-  /* 2^51 - 2^1 */ fsquare(t0,z2_50_0);
+-  /* 2^52 - 2^2 */ fsquare(t1,t0);
+-  /* 2^100 - 2^50 */ for (i = 2;i < 50;i += 2) { fsquare(t0,t1); fsquare(t1,t0); }
+-  /* 2^100 - 2^0 */ fmul(z2_100_0,t1,z2_50_0);
+-
+-  /* 2^101 - 2^1 */ fsquare(t1,z2_100_0);
+-  /* 2^102 - 2^2 */ fsquare(t0,t1);
+-  /* 2^200 - 2^100 */ for (i = 2;i < 100;i += 2) { fsquare(t1,t0); fsquare(t0,t1); }
+-  /* 2^200 - 2^0 */ fmul(t1,t0,z2_100_0);
+-
+-  /* 2^201 - 2^1 */ fsquare(t0,t1);
+-  /* 2^202 - 2^2 */ fsquare(t1,t0);
+-  /* 2^250 - 2^50 */ for (i = 2;i < 50;i += 2) { fsquare(t0,t1); fsquare(t1,t0); }
+-  /* 2^250 - 2^0 */ fmul(t0,t1,z2_50_0);
+-
+-  /* 2^251 - 2^1 */ fsquare(t1,t0);
+-  /* 2^252 - 2^2 */ fsquare(t0,t1);
+-  /* 2^253 - 2^3 */ fsquare(t1,t0);
+-  /* 2^254 - 2^4 */ fsquare(t0,t1);
+-  /* 2^255 - 2^5 */ fsquare(t1,t0);
+-  /* 2^255 - 21 */ fmul(out,t1,z11);
+-}
+-
+-int
+-curve25519_donna(u8 *mypublic, const u8 *secret, const u8 *basepoint) {
+-  limb bp[10], x[10], z[11], zmone[10];
+-  uint8_t e[32];
+-  int i;
+-
+-  for (i = 0; i < 32; ++i) e[i] = secret[i];
+-  e[0] &= 248;
+-  e[31] &= 127;
+-  e[31] |= 64;
+-
+-  fexpand(bp, basepoint);
+-  cmult(x, z, e, bp);
+-  crecip(zmone, z);
+-  fmul(z, x, zmone);
+-  fcontract(mypublic, z);
+-  return 0;
+-}
+diff --git a/curve25519.c b/curve25519.c
+new file mode 100644
+index 0000000..4b83776
+--- /dev/null
++++ b/curve25519.c
+@@ -0,0 +1,502 @@
++/*
++ * Dropbear - a SSH2 server
++ * 
++ * Copyright (c) 2002,2003 Matt Johnston
++ * All rights reserved.
++ * 
++ * Permission is hereby granted, free of charge, to any person obtaining a copy
++ * of this software and associated documentation files (the "Software"), to deal
++ * in the Software without restriction, including without limitation the rights
++ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
++ * copies of the Software, and to permit persons to whom the Software is
++ * furnished to do so, subject to the following conditions:
++ * 
++ * The above copyright notice and this permission notice shall be included in
++ * all copies or substantial portions of the Software.
++ * 
++ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
++ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
++ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
++ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
++ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
++ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
++ * SOFTWARE. */
++
++#include "includes.h"
++#include "dbrandom.h"
++#include "curve25519.h"
++
++#if DROPBEAR_CURVE25519 || DROPBEAR_ED25519
++
++/* Modified TweetNaCl version 20140427, a self-contained public-domain C library.
++ * https://tweetnacl.cr.yp.to/ */
++
++#define FOR(i,n) for (i = 0;i < n;++i)
++#define sv static void
++
++typedef unsigned char u8;
++typedef unsigned long u32;
++typedef unsigned long long u64;
++typedef long long i64;
++typedef i64 gf[16];
++
++#if DROPBEAR_CURVE25519
++static const gf
++  _121665 = {0xDB41,1};
++#endif /* DROPBEAR_CURVE25519 */
++#if DROPBEAR_ED25519
++static const gf
++  gf0,
++  gf1 = {1},
++  D2 = {0xf159, 0x26b2, 0x9b94, 0xebd6, 0xb156, 0x8283, 0x149a, 0x00e0, 0xd130, 0xeef3, 0x80f2, 0x198e, 0xfce7, 0x56df, 0xd9dc, 0x2406},
++  X = {0xd51a, 0x8f25, 0x2d60, 0xc956, 0xa7b2, 0x9525, 0xc760, 0x692c, 0xdc5c, 0xfdd6, 0xe231, 0xc0a4, 0x53fe, 0xcd6e, 0x36d3, 0x2169},
++  Y = {0x6658, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666};
++#if DROPBEAR_SIGNKEY_VERIFY
++static const gf
++  D = {0x78a3, 0x1359, 0x4dca, 0x75eb, 0xd8ab, 0x4141, 0x0a4d, 0x0070, 0xe898, 0x7779, 0x4079, 0x8cc7, 0xfe73, 0x2b6f, 0x6cee, 0x5203},
++  I = {0xa0b0, 0x4a0e, 0x1b27, 0xc4ee, 0xe478, 0xad2f, 0x1806, 0x2f43, 0xd7a7, 0x3dfb, 0x0099, 0x2b4d, 0xdf0b, 0x4fc1, 0x2480, 0x2b83};
++#endif /* DROPBEAR_SIGNKEY_VERIFY */
++#endif /* DROPBEAR_ED25519 */
++
++#if DROPBEAR_ED25519
++#if DROPBEAR_SIGNKEY_VERIFY
++static int vn(const u8 *x,const u8 *y,u32 n)
++{
++  u32 i,d = 0;
++  FOR(i,n) d |= x[i]^y[i];
++  return (1 & ((d - 1) >> 8)) - 1;
++}
++
++static int crypto_verify_32(const u8 *x,const u8 *y)
++{
++  return vn(x,y,32);
++}
++#endif /* DROPBEAR_SIGNKEY_VERIFY */
++
++sv set25519(gf r, const gf a)
++{
++  int i;
++  FOR(i,16) r[i]=a[i];
++}
++#endif /* DROPBEAR_ED25519 */
++
++sv car25519(gf o)
++{
++  int i;
++  i64 c;
++  FOR(i,16) {
++    o[i]+=(1LL<<16);
++    c=o[i]>>16;
++    o[(i+1)*(i<15)]+=c-1+37*(c-1)*(i==15);
++    o[i]-=c<<16;
++  }
++}
++
++sv sel25519(gf p,gf q,int b)
++{
++  i64 t,i,c=~(b-1);
++  FOR(i,16) {
++    t= c&(p[i]^q[i]);
++    p[i]^=t;
++    q[i]^=t;
++  }
++}
++
++sv pack25519(u8 *o,const gf n)
++{
++  int i,j,b;
++  gf m,t;
++  FOR(i,16) t[i]=n[i];
++  car25519(t);
++  car25519(t);
++  car25519(t);
++  FOR(j,2) {
++    m[0]=t[0]-0xffed;
++    for(i=1;i<15;i++) {
++      m[i]=t[i]-0xffff-((m[i-1]>>16)&1);
++      m[i-1]&=0xffff;
++    }
++    m[15]=t[15]-0x7fff-((m[14]>>16)&1);
++    b=(m[15]>>16)&1;
++    m[14]&=0xffff;
++    sel25519(t,m,1-b);
++  }
++  FOR(i,16) {
++    o[2*i]=t[i]&0xff;
++    o[2*i+1]=t[i]>>8;
++  }
++}
++
++#if DROPBEAR_ED25519
++#if DROPBEAR_SIGNKEY_VERIFY
++static int neq25519(const gf a, const gf b)
++{
++  u8 c[32],d[32];
++  pack25519(c,a);
++  pack25519(d,b);
++  return crypto_verify_32(c,d);
++}
++#endif /* DROPBEAR_SIGNKEY_VERIFY */
++
++static u8 par25519(const gf a)
++{
++  u8 d[32];
++  pack25519(d,a);
++  return d[0]&1;
++}
++#endif /* DROPBEAR_ED25519 */
++
++sv unpack25519(gf o, const u8 *n)
++{
++  int i;
++  FOR(i,16) o[i]=n[2*i]+((i64)n[2*i+1]<<8);
++  o[15]&=0x7fff;
++}
++
++sv A(gf o,const gf a,const gf b)
++{
++  int i;
++  FOR(i,16) o[i]=a[i]+b[i];
++}
++
++sv Z(gf o,const gf a,const gf b)
++{
++  int i;
++  FOR(i,16) o[i]=a[i]-b[i];
++}
++
++sv M(gf o,const gf a,const gf b)
++{
++  i64 i,j,t[31];
++  FOR(i,31) t[i]=0;
++  FOR(i,16) FOR(j,16) t[i+j]+=a[i]*b[j];
++  FOR(i,15) t[i]+=38*t[i+16];
++  FOR(i,16) o[i]=t[i];
++  car25519(o);
++  car25519(o);
++}
++
++sv S(gf o,const gf a)
++{
++  M(o,a,a);
++}
++
++sv inv25519(gf o,const gf i)
++{
++  gf c;
++  int a;
++  FOR(a,16) c[a]=i[a];
++  for(a=253;a>=0;a--) {
++    S(c,c);
++    if(a!=2&&a!=4) M(c,c,i);
++  }
++  FOR(a,16) o[a]=c[a];
++}
++
++#if DROPBEAR_ED25519 && DROPBEAR_SIGNKEY_VERIFY
++sv pow2523(gf o,const gf i)
++{
++  gf c;
++  int a;
++  FOR(a,16) c[a]=i[a];
++  for(a=250;a>=0;a--) {
++    S(c,c);
++    if(a!=1) M(c,c,i);
++  }
++  FOR(a,16) o[a]=c[a];
++}
++#endif /* DROPBEAR_ED25519 && DROPBEAR_SIGNKEY_VERIFY */
++
++#if DROPBEAR_CURVE25519
++int dropbear_curve25519_scalarmult(u8 *q,const u8 *n,const u8 *p)
++{
++  u8 z[32];
++  i64 x[80],r,i;
++  gf a,b,c,d,e,f;
++  FOR(i,31) z[i]=n[i];
++  z[31]=(n[31]&127)|64;
++  z[0]&=248;
++  unpack25519(x,p);
++  FOR(i,16) {
++    b[i]=x[i];
++    d[i]=a[i]=c[i]=0;
++  }
++  a[0]=d[0]=1;
++  for(i=254;i>=0;--i) {
++    r=(z[i>>3]>>(i&7))&1;
++    sel25519(a,b,r);
++    sel25519(c,d,r);
++    A(e,a,c);
++    Z(a,a,c);
++    A(c,b,d);
++    Z(b,b,d);
++    S(d,e);
++    S(f,a);
++    M(a,c,a);
++    M(c,b,e);
++    A(e,a,c);
++    Z(a,a,c);
++    S(b,a);
++    Z(c,d,f);
++    M(a,c,_121665);
++    A(a,a,d);
++    M(c,c,a);
++    M(a,d,f);
++    M(d,b,x);
++    S(b,e);
++    sel25519(a,b,r);
++    sel25519(c,d,r);
++  }
++  FOR(i,16) {
++    x[i+16]=a[i];
++    x[i+32]=c[i];
++    x[i+48]=b[i];
++    x[i+64]=d[i];
++  }
++  inv25519(x+32,x+32);
++  M(x+16,x+16,x+32);
++  pack25519(q,x+16);
++  return 0;
++}
++#endif /* DROPBEAR_CURVE25519 */
++
++#if DROPBEAR_ED25519
++static int crypto_hash(u8 *out,const u8 *m,u64 n)
++{
++  hash_state hs;
++
++  sha512_init(&hs);
++  sha512_process(&hs, m, n);
++  return sha512_done(&hs, out);
++}
++
++sv add(gf p[4],gf q[4])
++{
++  gf a,b,c,d,t,e,f,g,h;
++  
++  Z(a, p[1], p[0]);
++  Z(t, q[1], q[0]);
++  M(a, a, t);
++  A(b, p[0], p[1]);
++  A(t, q[0], q[1]);
++  M(b, b, t);
++  M(c, p[3], q[3]);
++  M(c, c, D2);
++  M(d, p[2], q[2]);
++  A(d, d, d);
++  Z(e, b, a);
++  Z(f, d, c);
++  A(g, d, c);
++  A(h, b, a);
++
++  M(p[0], e, f);
++  M(p[1], h, g);
++  M(p[2], g, f);
++  M(p[3], e, h);
++}
++
++sv cswap(gf p[4],gf q[4],u8 b)
++{
++  int i;
++  FOR(i,4)
++    sel25519(p[i],q[i],b);
++}
++
++sv pack(u8 *r,gf p[4])
++{
++  gf tx, ty, zi;
++  inv25519(zi, p[2]); 
++  M(tx, p[0], zi);
++  M(ty, p[1], zi);
++  pack25519(r, ty);
++  r[31] ^= par25519(tx) << 7;
++}
++
++sv scalarmult(gf p[4],gf q[4],const u8 *s)
++{
++  int i;
++  set25519(p[0],gf0);
++  set25519(p[1],gf1);
++  set25519(p[2],gf1);
++  set25519(p[3],gf0);
++  for (i = 255;i >= 0;--i) {
++    u8 b = (s[i/8]>>(i&7))&1;
++    cswap(p,q,b);
++    add(q,p);
++    add(p,p);
++    cswap(p,q,b);
++  }
++}
++
++sv scalarbase(gf p[4],const u8 *s)
++{
++  gf q[4];
++  set25519(q[0],X);
++  set25519(q[1],Y);
++  set25519(q[2],gf1);
++  M(q[3],X,Y);
++  scalarmult(p,q,s);
++}
++
++int dropbear_ed25519_make_key(u8 *pk,u8 *sk)
++{
++  u8 d[64];
++  gf p[4];
++
++  genrandom(sk, 32);
++
++  crypto_hash(d, sk, 32);
++  d[0] &= 248;
++  d[31] &= 127;
++  d[31] |= 64;
++
++  scalarbase(p,d);
++  pack(pk,p);
++
++  return 0;
++}
++
++static const u64 L[32] = {0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58, 0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x10};
++
++sv modL(u8 *r,i64 x[64])
++{
++  i64 carry,i,j;
++  for (i = 63;i >= 32;--i) {
++    carry = 0;
++    for (j = i - 32;j < i - 12;++j) {
++      x[j] += carry - 16 * x[i] * L[j - (i - 32)];
++      carry = (x[j] + 128) >> 8;
++      x[j] -= carry << 8;
++    }
++    x[j] += carry;
++    x[i] = 0;
++  }
++  carry = 0;
++  FOR(j,32) {
++    x[j] += carry - (x[31] >> 4) * L[j];
++    carry = x[j] >> 8;
++    x[j] &= 255;
++  }
++  FOR(j,32) x[j] -= carry * L[j];
++  FOR(i,32) {
++    x[i+1] += x[i] >> 8;
++    r[i] = x[i] & 255;
++  }
++}
++
++sv reduce(u8 *r)
++{
++  i64 x[64],i;
++  FOR(i,64) x[i] = (u64) r[i];
++  FOR(i,64) r[i] = 0;
++  modL(r,x);
++}
++
++int dropbear_ed25519_sign(const u8 *m,u32 mlen,u8 *s,u32 *slen,const u8 *sk, const u8 *pk)
++{
++  hash_state hs;
++  u8 d[64],h[64],r[64];
++  i64 x[64];
++  gf p[4];
++  u32 i,j;
++
++  crypto_hash(d, sk, 32);
++  d[0] &= 248;
++  d[31] &= 127;
++  d[31] |= 64;
++
++  *slen = 64;
++
++  sha512_init(&hs);
++  sha512_process(&hs,d + 32,32);
++  sha512_process(&hs,m,mlen);
++  sha512_done(&hs,r);
++  reduce(r);
++  scalarbase(p,r);
++  pack(s,p);
++
++  sha512_init(&hs);
++  sha512_process(&hs,s,32);
++  sha512_process(&hs,pk,32);
++  sha512_process(&hs,m,mlen);
++  sha512_done(&hs,h);
++  reduce(h);
++
++  FOR(i,64) x[i] = 0;
++  FOR(i,32) x[i] = (u64) r[i];
++  FOR(i,32) FOR(j,32) x[i+j] += h[i] * (u64) d[j];
++  modL(s + 32,x);
++
++  return 0;
++}
++
++#if DROPBEAR_SIGNKEY_VERIFY
++static int unpackneg(gf r[4],const u8 p[32])
++{
++  gf t, chk, num, den, den2, den4, den6;
++  set25519(r[2],gf1);
++  unpack25519(r[1],p);
++  S(num,r[1]);
++  M(den,num,D);
++  Z(num,num,r[2]);
++  A(den,r[2],den);
++
++  S(den2,den);
++  S(den4,den2);
++  M(den6,den4,den2);
++  M(t,den6,num);
++  M(t,t,den);
++
++  pow2523(t,t);
++  M(t,t,num);
++  M(t,t,den);
++  M(t,t,den);
++  M(r[0],t,den);
++
++  S(chk,r[0]);
++  M(chk,chk,den);
++  if (neq25519(chk, num)) M(r[0],r[0],I);
++
++  S(chk,r[0]);
++  M(chk,chk,den);
++  if (neq25519(chk, num)) return -1;
++
++  if (par25519(r[0]) == (p[31]>>7)) Z(r[0],gf0,r[0]);
++
++  M(r[3],r[0],r[1]);
++  return 0;
++}
++
++int dropbear_ed25519_verify(const u8 *m,u32 mlen,const u8 *s,u32 slen,const u8 *pk)
++{
++  hash_state hs;
++  u8 t[32],h[64];
++  gf p[4],q[4];
++
++  if (slen < 64) return -1;
++
++  if (unpackneg(q,pk)) return -1;
++
++  sha512_init(&hs);
++  sha512_process(&hs,s,32);
++  sha512_process(&hs,pk,32);
++  sha512_process(&hs,m,mlen);
++  sha512_done(&hs,h);
++
++  reduce(h);
++  scalarmult(p,q,h);
++
++  scalarbase(q,s + 32);
++  add(p,q);
++  pack(t,p);
++
++  if (crypto_verify_32(s, t))
++    return -1;
++
++  return 0;
++}
++#endif /* DROPBEAR_SIGNKEY_VERIFY */
++
++#endif /* DROPBEAR_ED25519 */
++
++#endif /* DROPBEAR_CURVE25519 || DROPBEAR_ED25519 */
+diff --git a/curve25519.h b/curve25519.h
+new file mode 100644
+index 0000000..7f75aed
+--- /dev/null
++++ b/curve25519.h
+@@ -0,0 +1,37 @@
++/*
++ * Dropbear - a SSH2 server
++ * 
++ * Copyright (c) 2002,2003 Matt Johnston
++ * All rights reserved.
++ * 
++ * Permission is hereby granted, free of charge, to any person obtaining a copy
++ * of this software and associated documentation files (the "Software"), to deal
++ * in the Software without restriction, including without limitation the rights
++ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
++ * copies of the Software, and to permit persons to whom the Software is
++ * furnished to do so, subject to the following conditions:
++ * 
++ * The above copyright notice and this permission notice shall be included in
++ * all copies or substantial portions of the Software.
++ * 
++ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
++ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
++ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
++ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
++ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
++ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
++ * SOFTWARE. */
++
++#ifndef DROPBEAR_CURVE25519_H
++#define DROPBEAR_CURVE25519_H
++
++int dropbear_curve25519_scalarmult(unsigned char *q, const unsigned char *n, const unsigned char *p);
++int dropbear_ed25519_make_key(unsigned char *pk, unsigned char  *sk);
++int dropbear_ed25519_sign(const unsigned char *m, unsigned long mlen,
++			  unsigned char *s, unsigned long *slen,
++			  const unsigned char *sk, const unsigned char *pk);
++int dropbear_ed25519_verify(const unsigned char *m, unsigned long mlen,
++			    const unsigned char *s, unsigned long slen,
++			    const unsigned char *pk);
++
++#endif /* DROPBEAR_CURVE25519_H */
+diff --git a/default_options.h b/default_options.h
+index 9000fcc..5b232dd 100644
+--- a/default_options.h
++++ b/default_options.h
+@@ -22,6 +22,7 @@ IMPORTANT: Some options will require "make clean" after changes */
+ #define DSS_PRIV_FILENAME "/etc/dropbear/dropbear_dss_host_key"
+ #define RSA_PRIV_FILENAME "/etc/dropbear/dropbear_rsa_host_key"
+ #define ECDSA_PRIV_FILENAME "/etc/dropbear/dropbear_ecdsa_host_key"
++#define ED25519_PRIV_FILENAME "/etc/dropbear/dropbear_ed25519_host_key"
+ 
+ /* Set NON_INETD_MODE if you require daemon functionality (ie Dropbear listens
+  * on chosen ports and keeps accepting connections. This is the default.
+@@ -116,11 +117,15 @@ IMPORTANT: Some options will require "make clean" after changes */
+  * code (either ECDSA or ECDH) increases binary size - around 30kB
+  * on x86-64 */
+ #define DROPBEAR_ECDSA 1
++/* Ed25519 is faster than ECDSA. Compiling in Ed25519 code increases
++   binary size - around 7,5kB on x86-64 */
++#define DROPBEAR_ED25519 1
+ 
+ /* RSA must be >=1024 */
+ #define DROPBEAR_DEFAULT_RSA_SIZE 2048
+ /* DSS is always 1024 */
+ /* ECDSA defaults to largest size configured, usually 521 */
++/* Ed25519 is always 256 */
+ 
+ /* Add runtime flag "-R" to generate hostkeys as-needed when the first 
+    connection using that key type occurs.
+@@ -143,7 +148,7 @@ IMPORTANT: Some options will require "make clean" after changes */
+  * group14 is supported by most implementations.
+  * group16 provides a greater strength level but is slower and increases binary size
+  * curve25519 and ecdh algorithms are faster than non-elliptic curve methods
+- * curve25519 increases binary size by ~8kB on x86-64
++ * curve25519 increases binary size by ~2,5kB on x86-64
+  * including either ECDH or ECDSA increases binary size by ~30kB on x86-64
+ 
+  * Small systems should generally include either curve25519 or ecdh for performance.
+diff --git a/dropbear.8 b/dropbear.8
+index 71c955a..345954f 100644
+--- a/dropbear.8
++++ b/dropbear.8
+@@ -107,7 +107,7 @@ Print the version
+ Authorized Keys
+ 
+ ~/.ssh/authorized_keys can be set up to allow remote login with a RSA,
+-ECDSA, or DSS
++ECDSA, Ed25519 or DSS
+ key. Each line is of the form
+ .TP
+ [restrictions] ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIgAsp... [comment]
+@@ -146,8 +146,8 @@ key authentication.
+ Host Key Files
+ 
+ Host key files are read at startup from a standard location, by default
+-/etc/dropbear/dropbear_dss_host_key, /etc/dropbear/dropbear_rsa_host_key, and 
+-/etc/dropbear/dropbear_ecdsa_host_key
++/etc/dropbear/dropbear_dss_host_key, /etc/dropbear/dropbear_rsa_host_key,
++/etc/dropbear/dropbear_ecdsa_host_key and /etc/dropbear/dropbear_ed25519_host_key
+ 
+ If the -r command line option is specified the default files are not loaded.
+ Host key files are of the form generated by dropbearkey. 
+diff --git a/dropbearkey.c b/dropbearkey.c
+index dd0e697..f881855 100644
+--- a/dropbearkey.c
++++ b/dropbearkey.c
+@@ -43,6 +43,10 @@
+  * mp_int	y
+  * mp_int	x
+  *
++ * Ed25519:
++ * string	"ssh-ed25519"
++ * string	k (32 bytes) + A (32 bytes)
++ *
+  */
+ #include "includes.h"
+ #include "signkey.h"
+@@ -51,6 +55,7 @@
+ 
+ #include "genrsa.h"
+ #include "gendss.h"
++#include "gened25519.h"
+ #include "ecdsa.h"
+ #include "crypto_desc.h"
+ #include "dbrandom.h"
+@@ -75,6 +80,9 @@ static void printhelp(char * progname) {
+ #endif
+ #if DROPBEAR_ECDSA
+ 					"		ecdsa\n"
++#endif
++#if DROPBEAR_ED25519
++					"		ed25519\n"
+ #endif
+ 					"-f filename    Use filename for the secret key.\n"
+ 					"               ~/.ssh/id_dropbear is recommended for client keys.\n"
+@@ -94,6 +102,9 @@ static void printhelp(char * progname) {
+ 					"521 "
+ #endif
+ 					"\n"
++#endif
++#if DROPBEAR_ED25519
++					"           Ed25519 has a fixed size of 256 bits\n"
+ #endif
+ 					"-y		Just print the publickey and fingerprint for the\n		private key in <filename>.\n"
+ #if DEBUG_TRACE
+@@ -106,6 +117,14 @@ static void printhelp(char * progname) {
+ static void check_signkey_bits(enum signkey_type type, int bits)
+ {
+ 	switch (type) {
++#if DROPBEAR_ED25519
++		case DROPBEAR_SIGNKEY_ED25519:
++			if (bits != 256) {
++				dropbear_exit("Ed25519 keys have a fixed size of 256 bits\n");
++				exit(EXIT_FAILURE);
++			}
++			break;
++#endif
+ #if DROPBEAR_RSA
+ 		case DROPBEAR_SIGNKEY_RSA:
+ 			if (bits < 512 || bits > 4096 || (bits % 8 != 0)) {
+@@ -224,6 +243,12 @@ int main(int argc, char ** argv) {
+ 		keytype = DROPBEAR_SIGNKEY_ECDSA_KEYGEN;
+ 	}
+ #endif
++#if DROPBEAR_ED25519
++	if (strcmp(typetext, "ed25519") == 0)
++	{
++		keytype = DROPBEAR_SIGNKEY_ED25519;
++	}
++#endif
+ 
+ 	if (keytype == DROPBEAR_SIGNKEY_NONE) {
+ 		fprintf(stderr, "Unknown key type '%s'\n", typetext);
+diff --git a/ed25519.c b/ed25519.c
+new file mode 100644
+index 0000000..3fb544c
+--- /dev/null
++++ b/ed25519.c
+@@ -0,0 +1,184 @@
++/*
++ * Dropbear - a SSH2 server
++ * 
++ * Copyright (c) 2002,2003 Matt Johnston
++ * All rights reserved.
++ * 
++ * Permission is hereby granted, free of charge, to any person obtaining a copy
++ * of this software and associated documentation files (the "Software"), to deal
++ * in the Software without restriction, including without limitation the rights
++ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
++ * copies of the Software, and to permit persons to whom the Software is
++ * furnished to do so, subject to the following conditions:
++ * 
++ * The above copyright notice and this permission notice shall be included in
++ * all copies or substantial portions of the Software.
++ * 
++ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
++ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
++ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
++ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
++ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
++ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
++ * SOFTWARE. */
++
++/* Perform Ed25519 operations on data, including reading keys, signing and
++ * verification. */
++
++#include "includes.h"
++#include "dbutil.h"
++#include "buffer.h"
++#include "ssh.h"
++#include "curve25519.h"
++#include "ed25519.h"
++
++#if DROPBEAR_ED25519
++
++/* Load a public ed25519 key from a buffer, initialising the values.
++ * The key will have the same format as buf_put_ed25519_key.
++ * These should be freed with ed25519_key_free.
++ * Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
++int buf_get_ed25519_pub_key(buffer *buf, dropbear_ed25519_key *key) {
++
++	unsigned int len;
++
++	TRACE(("enter buf_get_ed25519_pub_key"))
++	dropbear_assert(key != NULL);
++
++	buf_incrpos(buf, 4+SSH_SIGNKEY_ED25519_LEN); /* int + "ssh-ed25519" */
++
++	len = buf_getint(buf);
++	if (len != CURVE25519_LEN || buf->len - buf->pos < len) {
++		TRACE(("leave buf_get_ed25519_pub_key: failure"))
++		return DROPBEAR_FAILURE;
++	}
++
++	m_burn(key->priv, CURVE25519_LEN);
++	memcpy(key->pub, buf_getptr(buf, CURVE25519_LEN), CURVE25519_LEN);
++	buf_incrpos(buf, CURVE25519_LEN);
++
++	TRACE(("leave buf_get_ed25519_pub_key: success"))
++	return DROPBEAR_SUCCESS;
++}
++
++/* Same as buf_get_ed25519_pub_key, but reads private key at the end.
++ * Loads a public and private ed25519 key from a buffer
++ * Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
++int buf_get_ed25519_priv_key(buffer *buf, dropbear_ed25519_key *key) {
++
++	unsigned int len;
++
++	TRACE(("enter buf_get_ed25519_priv_key"))
++	dropbear_assert(key != NULL);
++
++	buf_incrpos(buf, 4+SSH_SIGNKEY_ED25519_LEN); /* int + "ssh-ed25519" */
++
++	len = buf_getint(buf);
++	if (len != CURVE25519_LEN*2 || buf->len - buf->pos < len) {
++		TRACE(("leave buf_get_ed25519_priv_key: failure"))
++		return DROPBEAR_FAILURE;
++	}
++
++	memcpy(key->priv, buf_getptr(buf, CURVE25519_LEN), CURVE25519_LEN);
++	buf_incrpos(buf, CURVE25519_LEN);
++	memcpy(key->pub, buf_getptr(buf, CURVE25519_LEN), CURVE25519_LEN);
++	buf_incrpos(buf, CURVE25519_LEN);
++
++	TRACE(("leave buf_get_ed25519_pub_key: success"))
++	return DROPBEAR_SUCCESS;
++}
++
++/* Clear and free the memory used by a public or private key */
++void ed25519_key_free(dropbear_ed25519_key *key) {
++
++	TRACE2(("enter ed25519_key_free"))
++
++	if (key == NULL) {
++		TRACE2(("leave ed25519_key_free: key == NULL"))
++		return;
++	}
++	m_burn(key->priv, CURVE25519_LEN);
++	m_free(key);
++
++	TRACE2(("leave rsa_key_free"))
++}
++
++/* Put the public ed25519 key into the buffer in the required format */
++void buf_put_ed25519_pub_key(buffer *buf, const dropbear_ed25519_key *key) {
++
++	TRACE(("enter buf_put_ed25519_pub_key"))
++	dropbear_assert(key != NULL);
++
++	buf_putstring(buf, SSH_SIGNKEY_ED25519, SSH_SIGNKEY_ED25519_LEN);
++	buf_putstring(buf, key->pub, CURVE25519_LEN);
++
++	TRACE(("leave buf_put_ed25519_pub_key"))
++}
++
++/* Put the public and private ed25519 key into the buffer in the required format */
++void buf_put_ed25519_priv_key(buffer *buf, const dropbear_ed25519_key *key) {
++
++	TRACE(("enter buf_put_ed25519_priv_key"))
++	dropbear_assert(key != NULL);
++
++	buf_putstring(buf, SSH_SIGNKEY_ED25519, SSH_SIGNKEY_ED25519_LEN);
++	buf_putint(buf, CURVE25519_LEN*2);
++	buf_putbytes(buf, key->priv, CURVE25519_LEN);
++	buf_putbytes(buf, key->pub, CURVE25519_LEN);
++
++	TRACE(("leave buf_put_ed25519_priv_key"))
++}
++
++/* Sign the data presented with key, writing the signature contents
++ * to the buffer */
++void buf_put_ed25519_sign(buffer* buf, const dropbear_ed25519_key *key, const buffer *data_buf) {
++
++	unsigned char s[64];
++	unsigned long slen = sizeof(s);
++
++	TRACE(("enter buf_put_ed25519_sign"))
++	dropbear_assert(key != NULL);
++
++	if (dropbear_ed25519_sign(data_buf->data, data_buf->len,
++				  s, &slen, key->priv, key->pub) == 0) {
++		buf_putstring(buf, SSH_SIGNKEY_ED25519, SSH_SIGNKEY_ED25519_LEN);
++		buf_putstring(buf, s, slen);
++	}
++
++	TRACE(("leave buf_put_ed25519_sign"))
++}
++
++#if DROPBEAR_SIGNKEY_VERIFY
++/* Verify a signature in buf, made on data by the key given.
++ * Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
++int buf_ed25519_verify(buffer *buf, const dropbear_ed25519_key *key, const buffer *data_buf) {
++
++	int ret = DROPBEAR_FAILURE;
++	unsigned char *s;
++	unsigned long slen;
++
++	TRACE(("enter buf_ed25519_verify"))
++	dropbear_assert(key != NULL);
++
++	slen = buf_getint(buf);
++	if (slen != 64 || buf->len - buf->pos < slen) {
++		TRACE(("bad size"))
++		goto out;
++	}
++	s = buf_getptr(buf, slen);
++
++	if (dropbear_ed25519_verify(data_buf->data, data_buf->len,
++				    s, slen, key->pub) == 0) {
++		/* signature is valid */
++		TRACE(("success!"))
++		ret = DROPBEAR_SUCCESS;
++	}
++
++out:
++	TRACE(("leave buf_ed25519_verify: ret %d", ret))
++	return ret;
++}
++
++#endif /* DROPBEAR_SIGNKEY_VERIFY */
++
++#endif /* DROPBEAR_ED25519 */
+diff --git a/ed25519.h b/ed25519.h
+new file mode 100644
+index 0000000..16c0d7b
+--- /dev/null
++++ b/ed25519.h
+@@ -0,0 +1,54 @@
++/*
++ * Dropbear - a SSH2 server
++ * 
++ * Copyright (c) 2002,2003 Matt Johnston
++ * All rights reserved.
++ * 
++ * Permission is hereby granted, free of charge, to any person obtaining a copy
++ * of this software and associated documentation files (the "Software"), to deal
++ * in the Software without restriction, including without limitation the rights
++ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
++ * copies of the Software, and to permit persons to whom the Software is
++ * furnished to do so, subject to the following conditions:
++ * 
++ * The above copyright notice and this permission notice shall be included in
++ * all copies or substantial portions of the Software.
++ * 
++ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
++ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
++ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
++ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
++ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
++ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
++ * SOFTWARE. */
++
++#ifndef DROPBEAR_ED25519_H_
++#define DROPBEAR_ED25519_H_
++
++#include "includes.h"
++#include "buffer.h"
++
++#if DROPBEAR_ED25519 
++
++#define CURVE25519_LEN 32
++
++typedef struct {
++
++	unsigned char priv[CURVE25519_LEN];
++	unsigned char pub[CURVE25519_LEN];
++
++} dropbear_ed25519_key;
++
++void buf_put_ed25519_sign(buffer* buf, const dropbear_ed25519_key *key, const buffer *data_buf);
++#if DROPBEAR_SIGNKEY_VERIFY
++int buf_ed25519_verify(buffer * buf, const dropbear_ed25519_key *key, const buffer *data_buf);
++#endif
++int buf_get_ed25519_pub_key(buffer* buf, dropbear_ed25519_key *key);
++int buf_get_ed25519_priv_key(buffer* buf, dropbear_ed25519_key *key);
++void buf_put_ed25519_pub_key(buffer* buf, const dropbear_ed25519_key *key);
++void buf_put_ed25519_priv_key(buffer* buf, const dropbear_ed25519_key *key);
++void ed25519_key_free(dropbear_ed25519_key *key);
++
++#endif /* DROPBEAR_ED25519 */
++
++#endif /* DROPBEAR_ED25519_H_ */
+diff --git a/filelist.txt b/filelist.txt
+index 8281c14..3b9bb67 100644
+--- a/filelist.txt
++++ b/filelist.txt
+@@ -99,6 +99,10 @@ rsa.c			RSA asymmetric crypto routines
+ 
+ dss.c			DSS asymmetric crypto routines
+ 
++ed25519.c		Ed25519 asymmetric crypto routines
++
++gened25519.c		Ed25519 key generation
++
+ gendss.c		DSS key generation
+ 
+ genrsa.c		RSA key generation
+diff --git a/fuzz-common.c b/fuzz-common.c
+index 5c90c45..b1b00f6 100644
+--- a/fuzz-common.c
++++ b/fuzz-common.c
+@@ -112,6 +112,14 @@ static void load_fixed_hostkeys(void) {
+         dropbear_exit("failed fixed ecdsa hostkey");
+     }
+ 
++    buf_setlen(b, 0);
++    buf_putbytes(b, keyed25519, keyed25519_len);
++    buf_setpos(b, 0);
++    type = DROPBEAR_SIGNKEY_ED25519;
++    if (buf_get_priv_key(b, svr_opts.hostkey, &type) == DROPBEAR_FAILURE) {
++        dropbear_exit("failed fixed ed25519 hostkey");
++    }
++
+     buf_free(b);
+ }
+ 
+diff --git a/fuzz-hostkeys.c b/fuzz-hostkeys.c
+index dc1615d..3fff5cb 100644
+--- a/fuzz-hostkeys.c
++++ b/fuzz-hostkeys.c
+@@ -127,3 +127,13 @@ unsigned char keyd[] = {
+   0xf9, 0x39
+ };
+ unsigned int keyd_len = 458;
++unsigned char keyed25519[] = {
++  0x00, 0x00, 0x00, 0x0b, 0x73, 0x73, 0x68, 0x2d, 0x65, 0x64, 0x32, 0x35,
++  0x35, 0x31, 0x39, 0x00, 0x00, 0x00, 0x40, 0x10, 0xb3, 0x79, 0x06, 0xe5,
++  0x9b, 0xe7, 0xe4, 0x6e, 0xec, 0xfe, 0xa5, 0x39, 0x21, 0x7c, 0xf6, 0x66,
++  0x8c, 0x0b, 0x6a, 0x01, 0x09, 0x05, 0xc7, 0x4f, 0x64, 0xa8, 0x24, 0xd2,
++  0x8d, 0xbd, 0xdd, 0xc6, 0x3c, 0x99, 0x1b, 0x2d, 0x3e, 0x33, 0x90, 0x19,
++  0xa4, 0xd5, 0xe9, 0x23, 0xfe, 0x8e, 0xd6, 0xd4, 0xf9, 0xb1, 0x11, 0x69,
++  0x7c, 0x57, 0x52, 0x0e, 0x41, 0xdb, 0x1b, 0x12, 0x87, 0xfa, 0xc9
++};
++unsigned int keyed25519_len = 83;
+diff --git a/fuzzer-kexcurve25519.c b/fuzzer-kexcurve25519.c
+new file mode 100644
+index 0000000..f2eab14
+--- /dev/null
++++ b/fuzzer-kexcurve25519.c
+@@ -0,0 +1,72 @@
++#include "fuzz.h"
++#include "session.h"
++#include "fuzz-wrapfd.h"
++#include "debug.h"
++#include "runopts.h"
++#include "algo.h"
++#include "bignum.h"
++
++int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
++	static int once = 0;
++	static struct key_context* keep_newkeys = NULL;
++	/* number of generated parameters is limited by the timeout for the first run.
++	   TODO move this to the libfuzzer initialiser function instead if the timeout
++	   doesn't apply there */
++	#define NUM_PARAMS 20
++	static struct kex_curve25519_param *curve25519_params[NUM_PARAMS];
++
++	if (!once) {
++		fuzz_common_setup();
++		fuzz_svr_setup();
++
++		keep_newkeys = (struct key_context*)m_malloc(sizeof(struct key_context));
++		keep_newkeys->algo_kex = fuzz_get_algo(sshkex, "curve25519-sha256");
++		keep_newkeys->algo_hostkey = DROPBEAR_SIGNKEY_ED25519;
++		ses.newkeys = keep_newkeys;
++
++		/* Pre-generate parameters */
++		int i;
++		for (i = 0; i < NUM_PARAMS; i++) {
++			curve25519_params[i] = gen_kexcurve25519_param();
++		}
++
++		once = 1;
++	}
++
++	if (fuzz_set_input(Data, Size) == DROPBEAR_FAILURE) {
++		return 0;
++	}
++
++	m_malloc_set_epoch(1);
++
++	if (setjmp(fuzz.jmp) == 0) {
++		/* Based on recv_msg_kexdh_init()/send_msg_kexdh_reply() 
++		with DROPBEAR_KEX_CURVE25519 */
++		ses.newkeys = keep_newkeys;
++
++		/* Choose from the collection of curve25519 params */
++		unsigned int e = buf_getint(fuzz.input);
++		struct kex_curve25519_param *curve25519_param = curve25519_params[e % NUM_PARAMS];
++
++		buffer * ecdh_qs = buf_getstringbuf(fuzz.input);
++
++		ses.kexhashbuf = buf_new(KEXHASHBUF_MAX_INTS);
++		kexcurve25519_comb_key(curve25519_param, ecdh_qs, svr_opts.hostkey);
++
++		mp_clear(ses.dh_K);
++		m_free(ses.dh_K);
++		buf_free(ecdh_qs);
++
++		buf_free(ses.hash);
++		buf_free(ses.session_id);
++		/* kexhashbuf is freed in kexdh_comb_key */
++
++		m_malloc_free_epoch(1, 0);
++	} else {
++		m_malloc_free_epoch(1, 1);
++		TRACE(("dropbear_exit longjmped"))
++		/* dropbear_exit jumped here */
++	}
++
++	return 0;
++}
+diff --git a/gened25519.c b/gened25519.c
+new file mode 100644
+index 0000000..a027914
+--- /dev/null
++++ b/gened25519.c
+@@ -0,0 +1,47 @@
++/*
++ * Dropbear - a SSH2 server
++ * 
++ * Copyright (c) 2002,2003 Matt Johnston
++ * All rights reserved.
++ * 
++ * Permission is hereby granted, free of charge, to any person obtaining a copy
++ * of this software and associated documentation files (the "Software"), to deal
++ * in the Software without restriction, including without limitation the rights
++ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
++ * copies of the Software, and to permit persons to whom the Software is
++ * furnished to do so, subject to the following conditions:
++ * 
++ * The above copyright notice and this permission notice shall be included in
++ * all copies or substantial portions of the Software.
++ * 
++ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
++ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
++ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
++ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
++ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
++ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
++ * SOFTWARE. */
++
++#include "includes.h"
++#include "dbutil.h"
++#include "dbrandom.h"
++#include "curve25519.h"
++#include "gened25519.h"
++
++#if DROPBEAR_ED25519
++
++dropbear_ed25519_key * gen_ed25519_priv_key(unsigned int size) {
++
++	dropbear_ed25519_key *key;
++
++	if (size != 256) {
++		dropbear_exit("Ed25519 keys have a fixed size of 256 bits");
++	}
++
++	key = m_malloc(sizeof(*key));
++	dropbear_ed25519_make_key(key->pub, key->priv);
++
++	return key;
++}
++
++#endif /* DROPBEAR_ED25519 */
+diff --git a/gened25519.h b/gened25519.h
+new file mode 100644
+index 0000000..8058310
+--- /dev/null
++++ b/gened25519.h
+@@ -0,0 +1,36 @@
++/*
++ * Dropbear - a SSH2 server
++ * 
++ * Copyright (c) 2002,2003 Matt Johnston
++ * All rights reserved.
++ * 
++ * Permission is hereby granted, free of charge, to any person obtaining a copy
++ * of this software and associated documentation files (the "Software"), to deal
++ * in the Software without restriction, including without limitation the rights
++ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
++ * copies of the Software, and to permit persons to whom the Software is
++ * furnished to do so, subject to the following conditions:
++ * 
++ * The above copyright notice and this permission notice shall be included in
++ * all copies or substantial portions of the Software.
++ * 
++ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
++ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
++ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
++ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
++ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
++ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
++ * SOFTWARE. */
++
++#ifndef DROPBEAR_GENED25519_H_
++#define DROPBEAR_GENED25519_H_
++
++#include "ed25519.h"
++
++#if DROPBEAR_ED25519
++
++dropbear_ed25519_key * gen_ed25519_priv_key(unsigned int size);
++
++#endif /* DROPBEAR_ED25519 */
++
++#endif /* DROPBEAR_GENED25519_H_ */
+diff --git a/gensignkey.c b/gensignkey.c
+index 34b6f5a..674d81f 100644
+--- a/gensignkey.c
++++ b/gensignkey.c
+@@ -4,6 +4,7 @@
+ #include "ecdsa.h"
+ #include "genrsa.h"
+ #include "gendss.h"
++#include "gened25519.h"
+ #include "signkey.h"
+ #include "dbrandom.h"
+ 
+@@ -68,6 +69,10 @@ static int get_default_bits(enum signkey_type keytype)
+ 			return 384;
+ 		case DROPBEAR_SIGNKEY_ECDSA_NISTP256:
+ 			return 256;
++#endif
++#if DROPBEAR_ED25519
++		case DROPBEAR_SIGNKEY_ED25519:
++			return 256;
+ #endif
+ 		default:
+ 			return 0;
+@@ -118,6 +123,11 @@ int signkey_generate(enum signkey_type keytype, int bits, const char* filename,
+ 				*signkey_key_ptr(key, keytype) = ecckey;
+ 			}
+ 			break;
++#endif
++#if DROPBEAR_ED25519
++		case DROPBEAR_SIGNKEY_ED25519:
++			key->ed25519key = gen_ed25519_priv_key(bits);
++			break;
+ #endif
+ 		default:
+ 			dropbear_exit("Internal error");
+diff --git a/keyimport.c b/keyimport.c
+index 7304e58..ad0c530 100644
+--- a/keyimport.c
++++ b/keyimport.c
+@@ -35,6 +35,15 @@
+ #include "buffer.h"
+ #include "dbutil.h"
+ #include "ecc.h"
++#include "ssh.h"
++
++static const unsigned char OSSH_PKEY_BLOB[] =
++	"openssh-key-v1\0"			/* AUTH_MAGIC */
++	"\0\0\0\4none"				/* cipher name*/
++	"\0\0\0\4none"				/* kdf name */
++	"\0\0\0\0"				/* kdf */
++	"\0\0\0\1";				/* key num */
++#define OSSH_PKEY_BLOBLEN (sizeof(OSSH_PKEY_BLOB) - 1)
+ 
+ #if DROPBEAR_ECDSA
+ static const unsigned char OID_SEC256R1_BLOB[] = {0x2a, 0x86, 0x48, 0xce, 0x3d, 0x03, 0x01, 0x07};
+@@ -352,7 +361,7 @@ struct mpint_pos { void *start; int bytes; };
+  * Code to read and write OpenSSH private keys.
+  */
+ 
+-enum { OSSH_DSA, OSSH_RSA, OSSH_EC };
++enum { OSSH_DSA, OSSH_RSA, OSSH_EC, OSSH_PKEY };
+ struct openssh_key {
+ 	int type;
+ 	int encrypted;
+@@ -364,11 +373,12 @@ struct openssh_key {
+ static struct openssh_key *load_openssh_key(const char *filename)
+ {
+ 	struct openssh_key *ret;
++	buffer *buf = NULL;
+ 	FILE *fp = NULL;
+ 	char buffer[256];
+ 	char *errmsg = NULL, *p = NULL;
+ 	int headers_done;
+-	unsigned long len, outlen;
++	unsigned long len;
+ 
+ 	ret = (struct openssh_key*)m_malloc(sizeof(struct openssh_key));
+ 	ret->keyblob = NULL;
+@@ -397,12 +407,15 @@ static struct openssh_key *load_openssh_key(const char *filename)
+ 		ret->type = OSSH_DSA;
+ 	else if (!strcmp(buffer, "-----BEGIN EC PRIVATE KEY-----\n"))
+ 		ret->type = OSSH_EC;
++	else if (!strcmp(buffer, "-----BEGIN OPENSSH PRIVATE KEY-----\n"))
++		ret->type = OSSH_PKEY;
+ 	else {
+ 		errmsg = "Unrecognised key type";
+ 		goto error;
+ 	}
+ 
+ 	headers_done = 0;
++	buf = buf_new(0);
+ 	while (1) {
+ 		if (!fgets(buffer, sizeof(buffer), fp)) {
+ 			errmsg = "Unexpected end of file";
+@@ -448,20 +461,31 @@ static struct openssh_key *load_openssh_key(const char *filename)
+ 		} else {
+ 			headers_done = 1;
+ 			len = strlen(buffer);
+-			outlen = len*4/3;
+-			if (ret->keyblob_len + outlen > ret->keyblob_size) {
+-				ret->keyblob_size = ret->keyblob_len + outlen + 256;
+-				ret->keyblob = (unsigned char*)m_realloc(ret->keyblob,
+-						ret->keyblob_size);
+-			}
+-			outlen = ret->keyblob_size - ret->keyblob_len;
+-			if (base64_decode((const unsigned char *)buffer, len,
+-						ret->keyblob + ret->keyblob_len, &outlen) != CRYPT_OK){
+-				errmsg = "Error decoding base64";
+-				goto error;
+-			}
+-			ret->keyblob_len += outlen;
++			buf = buf_resize(buf, buf->size + len);
++			buf_putbytes(buf, buffer, len);
++		}
++	}
++
++	if (buf && buf->len) {
++		ret->keyblob_size = ret->keyblob_len + buf->len*4/3 + 256;
++		ret->keyblob = (unsigned char*)m_realloc(ret->keyblob, ret->keyblob_size);
++		len = ret->keyblob_size;
++		if (base64_decode((const unsigned char *)buf->data, buf->len,
++					ret->keyblob, &len) != CRYPT_OK){
++			errmsg = "Error decoding base64";
++			goto error;
++		}
++		ret->keyblob_len = len;
++	}
++
++	if (ret->type == OSSH_PKEY) {
++		if (ret->keyblob_len < OSSH_PKEY_BLOBLEN ||
++				memcmp(ret->keyblob, OSSH_PKEY_BLOB, OSSH_PKEY_BLOBLEN)) {
++			errmsg = "Error decoding OpenSSH key";
++			goto error;
+ 		}
++		ret->keyblob_len -= OSSH_PKEY_BLOBLEN;
++		memmove(ret->keyblob, ret->keyblob + OSSH_PKEY_BLOBLEN, ret->keyblob_len);
+ 	}
+ 
+ 	if (ret->keyblob_len == 0 || !ret->keyblob) {
+@@ -474,10 +498,18 @@ static struct openssh_key *load_openssh_key(const char *filename)
+ 		goto error;
+ 	}
+ 
++	if (buf) {
++		buf_burn(buf);
++		buf_free(buf);
++	}
+ 	m_burn(buffer, sizeof(buffer));
+ 	return ret;
+ 
+ error:
++	if (buf) {
++		buf_burn(buf);
++		buf_free(buf);
++	}
+ 	m_burn(buffer, sizeof(buffer));
+ 	if (ret) {
+ 		if (ret->keyblob) {
+@@ -569,6 +601,57 @@ static sign_key *openssh_read(const char *filename, const char * UNUSED(passphra
+ #endif 
+ 	}
+ 
++	/*
++	 * Now we have a decrypted key blob, which contains OpenSSH
++	 * encoded private key. We must now untangle the OpenSSH format.
++	 */
++	if (key->type == OSSH_PKEY) {
++		blobbuf = buf_new(key->keyblob_len);
++		buf_putbytes(blobbuf, key->keyblob, key->keyblob_len);
++		buf_setpos(blobbuf, 0);
++
++		/* limit length of private key blob */
++		len = buf_getint(blobbuf);
++		buf_setlen(blobbuf, blobbuf->pos + len);
++
++		type = DROPBEAR_SIGNKEY_ANY;
++		if (buf_get_pub_key(blobbuf, retkey, &type)
++				!= DROPBEAR_SUCCESS) {
++			errmsg = "Error parsing OpenSSH key";
++			goto ossh_error;
++		}
++
++		/* restore full length */
++		buf_setlen(blobbuf, key->keyblob_len);
++
++		if (type != DROPBEAR_SIGNKEY_NONE) {
++			retkey->type = type;
++			/* limit length of private key blob */
++			len = buf_getint(blobbuf);
++			buf_setlen(blobbuf, blobbuf->pos + len);
++#if DROPBEAR_ED25519
++			if (type == DROPBEAR_SIGNKEY_ED25519) {
++				buf_incrpos(blobbuf, 8);
++				buf_eatstring(blobbuf);
++				buf_eatstring(blobbuf);
++				buf_incrpos(blobbuf, -SSH_SIGNKEY_ED25519_LEN-4);
++				if (buf_get_ed25519_priv_key(blobbuf, retkey->ed25519key)
++						== DROPBEAR_SUCCESS) {
++					errmsg = NULL;
++					retval = retkey;
++					goto error;
++				}
++			}
++#endif
++		}
++
++		errmsg = "Unsupported OpenSSH key type";
++		ossh_error:
++		sign_key_free(retkey);
++		retkey = NULL;
++		goto error;
++	}
++
+ 	/*
+ 	 * Now we have a decrypted key blob, which contains an ASN.1
+ 	 * encoded private key. We must now untangle the ASN.1.
+@@ -1129,6 +1212,51 @@ static int openssh_write(const char *filename, sign_key *key,
+ 	}
+ #endif
+ 
++#if DROPBEAR_ED25519
++	if (key->type == DROPBEAR_SIGNKEY_ED25519) {
++		buffer *buf = buf_new(300);
++		keyblob = buf_new(100);
++		extrablob = buf_new(200);
++
++		/* private key blob w/o header */
++		buf_put_priv_key(keyblob, key, key->type);
++		buf_setpos(keyblob, 0);
++		buf_incrpos(keyblob, buf_getint(keyblob));
++		len = buf_getint(keyblob);
++
++		/* header */
++		buf_putbytes(buf, OSSH_PKEY_BLOB, OSSH_PKEY_BLOBLEN);
++
++		/* public key */
++		buf_put_pub_key(buf, key, key->type);
++
++		/* private key */
++		buf_incrwritepos(extrablob, 4);
++		buf_put_pub_key(extrablob, key, key->type);
++		buf_putstring(extrablob, buf_getptr(keyblob, len), len);
++		/* comment */
++		buf_putstring(extrablob, "", 0);
++		/* padding to cipher block length */
++		len = (extrablob->len+8) & ~7;
++		for (i = 1; len - extrablob->len > 0; i++)
++			buf_putbyte(extrablob, i);
++		buf_setpos(extrablob, 0);
++		buf_putbytes(extrablob, "\0\0\0\0\0\0\0\0", 8);
++		buf_putbufstring(buf, extrablob);
++
++		outlen = len = pos = buf->len;
++		outblob = (unsigned char*)m_malloc(outlen);
++		memcpy(outblob, buf->data, buf->len);
++
++		buf_burn(buf);
++		buf_free(buf);
++		buf = NULL;
++
++		header = "-----BEGIN OPENSSH PRIVATE KEY-----\n";
++		footer = "-----END OPENSSH PRIVATE KEY-----\n";
++	}
++#endif
++
+ 	/*
+ 	 * Padding on OpenSSH keys is deterministic. The number of
+ 	 * padding bytes is always more than zero, and always at most
+diff --git a/signkey.c b/signkey.c
+index 88f06c7..a0af44a 100644
+--- a/signkey.c
++++ b/signkey.c
+@@ -39,8 +39,11 @@ static const char * const signkey_names[DROPBEAR_SIGNKEY_NUM_NAMED] = {
+ #if DROPBEAR_ECDSA
+ 	"ecdsa-sha2-nistp256",
+ 	"ecdsa-sha2-nistp384",
+-	"ecdsa-sha2-nistp521"
++	"ecdsa-sha2-nistp521",
+ #endif /* DROPBEAR_ECDSA */
++#if DROPBEAR_ED25519
++	"ssh-ed25519",
++#endif /* DROPBEAR_ED25519 */
+ };
+ 
+ /* malloc a new sign_key and set the dss and rsa keys to NULL */
+@@ -107,6 +110,10 @@ Be sure to check both (ret != NULL) and (*ret != NULL) */
+ void **
+ signkey_key_ptr(sign_key *key, enum signkey_type type) {
+ 	switch (type) {
++#if DROPBEAR_ED25519
++		case DROPBEAR_SIGNKEY_ED25519:
++			return (void**)&key->ed25519key;
++#endif
+ #if DROPBEAR_ECDSA
+ #if DROPBEAR_ECC_256
+ 		case DROPBEAR_SIGNKEY_ECDSA_NISTP256:
+@@ -200,6 +207,17 @@ int buf_get_pub_key(buffer *buf, sign_key *key, enum signkey_type *type) {
+ 		}
+ 	}
+ #endif
++#if DROPBEAR_ED25519
++	if (keytype == DROPBEAR_SIGNKEY_ED25519) {
++		ed25519_key_free(key->ed25519key);
++		key->ed25519key = m_malloc(sizeof(*key->ed25519key));
++		ret = buf_get_ed25519_pub_key(buf, key->ed25519key);
++		if (ret == DROPBEAR_FAILURE) {
++			m_free(key->ed25519key);
++			key->ed25519key = NULL;
++		}
++	}
++#endif
+ 
+ 	TRACE2(("leave buf_get_pub_key"))
+ 
+@@ -270,6 +288,17 @@ int buf_get_priv_key(buffer *buf, sign_key *key, enum signkey_type *type) {
+ 		}
+ 	}
+ #endif
++#if DROPBEAR_ED25519
++	if (keytype == DROPBEAR_SIGNKEY_ED25519) {
++		ed25519_key_free(key->ed25519key);
++		key->ed25519key = m_malloc(sizeof(*key->ed25519key));
++		ret = buf_get_ed25519_priv_key(buf, key->ed25519key);
++		if (ret == DROPBEAR_FAILURE) {
++			m_free(key->ed25519key);
++			key->ed25519key = NULL;
++		}
++	}
++#endif
+ 
+ 	TRACE2(("leave buf_get_priv_key"))
+ 
+@@ -302,6 +331,11 @@ void buf_put_pub_key(buffer* buf, sign_key *key, enum signkey_type type) {
+ 			buf_put_ecdsa_pub_key(pubkeys, *eck);
+ 		}
+ 	}
++#endif
++#if DROPBEAR_ED25519
++	if (type == DROPBEAR_SIGNKEY_ED25519) {
++		buf_put_ed25519_pub_key(pubkeys, key->ed25519key);
++	}
+ #endif
+ 	if (pubkeys->len == 0) {
+ 		dropbear_exit("Bad key types in buf_put_pub_key");
+@@ -341,6 +375,13 @@ void buf_put_priv_key(buffer* buf, sign_key *key, enum signkey_type type) {
+ 			return;
+ 		}
+ 	}
++#endif
++#if DROPBEAR_ED25519
++	if (type == DROPBEAR_SIGNKEY_ED25519) {
++		buf_put_ed25519_priv_key(buf, key->ed25519key);
++		TRACE(("leave buf_put_priv_key: ed25519 done"))
++		return;
++	}
+ #endif
+ 	dropbear_exit("Bad key types in put pub key");
+ }
+@@ -379,6 +420,10 @@ void sign_key_free(sign_key *key) {
+ 		key->ecckey521 = NULL;
+ 	}
+ #endif
++#endif
++#if DROPBEAR_ED25519
++	ed25519_key_free(key->ed25519key);
++	key->ed25519key = NULL;
+ #endif
+ 
+ 	m_free(key->filename);
+@@ -503,6 +548,11 @@ void buf_put_sign(buffer* buf, sign_key *key, enum signkey_type type,
+ 			buf_put_ecdsa_sign(sigblob, *eck, data_buf);
+ 		}
+ 	}
++#endif
++#if DROPBEAR_ED25519
++	if (type == DROPBEAR_SIGNKEY_ED25519) {
++		buf_put_ed25519_sign(sigblob, key->ed25519key, data_buf);
++	}
+ #endif
+ 	if (sigblob->len == 0) {
+ 		dropbear_exit("Non-matching signing type");
+@@ -555,6 +605,14 @@ int buf_verify(buffer * buf, sign_key *key, const buffer *data_buf) {
+ 		}
+ 	}
+ #endif
++#if DROPBEAR_ED25519
++	if (type == DROPBEAR_SIGNKEY_ED25519) {
++		if (key->ed25519key == NULL) {
++			dropbear_exit("No Ed25519 key to verify signature");
++		}
++		return buf_ed25519_verify(buf, key->ed25519key, data_buf);
++	}
++#endif
+ 
+ 	dropbear_exit("Non-matching signing type");
+ 	return DROPBEAR_FAILURE;
+diff --git a/signkey.h b/signkey.h
+index 59df3ee..fa39a02 100644
+--- a/signkey.h
++++ b/signkey.h
+@@ -28,6 +28,7 @@
+ #include "buffer.h"
+ #include "dss.h"
+ #include "rsa.h"
++#include "ed25519.h"
+ 
+ enum signkey_type {
+ #if DROPBEAR_RSA
+@@ -41,6 +42,9 @@ enum signkey_type {
+ 	DROPBEAR_SIGNKEY_ECDSA_NISTP384,
+ 	DROPBEAR_SIGNKEY_ECDSA_NISTP521,
+ #endif /* DROPBEAR_ECDSA */
++#if DROPBEAR_ED25519
++	DROPBEAR_SIGNKEY_ED25519,
++#endif
+ 	DROPBEAR_SIGNKEY_NUM_NAMED,
+ 	DROPBEAR_SIGNKEY_ECDSA_KEYGEN = 70, /* just "ecdsa" for keygen */
+ 	DROPBEAR_SIGNKEY_ANY = 80,
+@@ -78,6 +82,9 @@ struct SIGN_key {
+ 	ecc_key * ecckey521;
+ #endif
+ #endif
++#if DROPBEAR_ED25519
++	dropbear_ed25519_key * ed25519key;
++#endif
+ };
+ 
+ typedef struct SIGN_key sign_key;
+diff --git a/ssh.h b/ssh.h
+index f40b65a..db723b8 100644
+--- a/ssh.h
++++ b/ssh.h
+@@ -105,6 +105,8 @@
+ #define SSH_SIGNKEY_DSS_LEN 7
+ #define SSH_SIGNKEY_RSA "ssh-rsa"
+ #define SSH_SIGNKEY_RSA_LEN 7
++#define SSH_SIGNKEY_ED25519 "ssh-ed25519"
++#define SSH_SIGNKEY_ED25519_LEN 11
+ 
+ /* Agent commands. These aren't part of the spec, and are defined
+  * only on the openssh implementation. */
+diff --git a/svr-kex.c b/svr-kex.c
+index 406ad97..af16d2f 100644
+--- a/svr-kex.c
++++ b/svr-kex.c
+@@ -122,6 +122,11 @@ static void svr_ensure_hostkey() {
+ 		case DROPBEAR_SIGNKEY_ECDSA_NISTP521:
+ 			fn = ECDSA_PRIV_FILENAME;
+ 			break;
++#endif
++#if DROPBEAR_ED25519
++		case DROPBEAR_SIGNKEY_ED25519:
++			fn = ED25519_PRIV_FILENAME;
++			break;
+ #endif
+ 		default:
+ 			dropbear_assert(0);
+@@ -219,7 +224,8 @@ static void send_msg_kexdh_reply(mp_int *dh_e, buffer *ecdh_qs) {
+ 			{
+ 			struct kex_curve25519_param *param = gen_kexcurve25519_param();
+ 			kexcurve25519_comb_key(param, ecdh_qs, svr_opts.hostkey);
+-			buf_putstring(ses.writepayload, (const char*)param->pub, CURVE25519_LEN);
++
++			buf_putstring(ses.writepayload, param->pub, CURVE25519_LEN);
+ 			free_kexcurve25519_param(param);
+ 			}
+ 			break;
+diff --git a/svr-runopts.c b/svr-runopts.c
+index d7a0d5a..d430825 100644
+--- a/svr-runopts.c
++++ b/svr-runopts.c
+@@ -57,6 +57,9 @@ static void printhelp(const char * progname) {
+ #if DROPBEAR_ECDSA
+ 					"		ecdsa %s\n"
+ #endif
++#if DROPBEAR_ED25519
++					"		ed25519 %s\n"
++#endif
+ #if DROPBEAR_DELAY_HOSTKEY
+ 					"-R		Create hostkeys as required\n" 
+ #endif
+@@ -116,6 +119,9 @@ static void printhelp(const char * progname) {
+ #endif
+ #if DROPBEAR_ECDSA
+ 					ECDSA_PRIV_FILENAME,
++#endif
++#if DROPBEAR_ED25519
++					ED25519_PRIV_FILENAME,
+ #endif
+ 					MAX_AUTH_TRIES,
+ 					DROPBEAR_MAX_PORTS, DROPBEAR_DEFPORT, DROPBEAR_PIDFILE,
+@@ -538,6 +544,13 @@ static void loadhostkey(const char *keyfile, int fatal_duplicate) {
+ 	}
+ #endif
+ #endif /* DROPBEAR_ECDSA */
++
++#if DROPBEAR_ED25519
++	if (type == DROPBEAR_SIGNKEY_ED25519) {
++		loadhostkey_helper("ed25519", (void**)&read_key->ed25519key, (void**)&svr_opts.hostkey->ed25519key, fatal_duplicate);
++	}
++#endif
++
+ 	sign_key_free(read_key);
+ 	TRACE(("leave loadhostkey"))
+ }
+@@ -578,6 +591,9 @@ void load_all_hostkeys() {
+ 
+ #if DROPBEAR_ECDSA
+ 		loadhostkey(ECDSA_PRIV_FILENAME, 0);
++#endif
++#if DROPBEAR_ED25519
++		loadhostkey(ED25519_PRIV_FILENAME, 0);
+ #endif
+ 	}
+ 
+@@ -642,6 +658,14 @@ void load_all_hostkeys() {
+ #endif
+ #endif /* DROPBEAR_ECDSA */
+ 
++#if DROPBEAR_ED25519
++	if (!svr_opts.delay_hostkey && !svr_opts.hostkey->ed25519key) {
++		disablekey(DROPBEAR_SIGNKEY_ED25519);
++	} else {
++		any_keys = 1;
++	}
++#endif
++
+ 	if (!any_keys) {
+ 		dropbear_exit("No hostkeys available. 'dropbear -R' may be useful or run dropbearkey.");
+ 	}
+diff --git a/sysoptions.h b/sysoptions.h
+index cfd5469..2c27caf 100644
+--- a/sysoptions.h
++++ b/sysoptions.h
+@@ -145,7 +145,8 @@ If you test it please contact the Dropbear author */
+ #define DROPBEAR_SHA384 (DROPBEAR_ECC_384)
+ /* LTC SHA384 depends on SHA512 */
+ #define DROPBEAR_SHA512 ((DROPBEAR_SHA2_512_HMAC) || (DROPBEAR_ECC_521) \
+-			|| (DROPBEAR_SHA384) || (DROPBEAR_DH_GROUP16))
++			|| (DROPBEAR_SHA384) || (DROPBEAR_DH_GROUP16) \
++			|| (DROPBEAR_ED25519))
+ #define DROPBEAR_MD5 (DROPBEAR_MD5_HMAC)
+ 
+ #define DROPBEAR_DH_GROUP14 ((DROPBEAR_DH_GROUP14_SHA256) || (DROPBEAR_DH_GROUP14_SHA1))
+@@ -186,7 +187,7 @@ If you test it please contact the Dropbear author */
+ /* For a 4096 bit DSS key, empirically determined */
+ #define MAX_PRIVKEY_SIZE 1700
+ 
+-#define MAX_HOSTKEYS 3
++#define MAX_HOSTKEYS 4
+ 
+ /* The maximum size of the bignum portion of the kexhash buffer */
+ /* Sect. 8 of the transport rfc 4253, K_S + e + f + K */
+@@ -252,7 +253,7 @@ If you test it please contact the Dropbear author */
+ 	#error "At least one encryption algorithm must be enabled. AES128 is recommended."
+ #endif
+ 
+-#if !(DROPBEAR_RSA || DROPBEAR_DSS || DROPBEAR_ECDSA)
++#if !(DROPBEAR_RSA || DROPBEAR_DSS || DROPBEAR_ECDSA || DROPBEAR_ED25519)
+ 	#error "At least one hostkey or public-key algorithm must be enabled; RSA is recommended."
+ #endif
+ 
+-- 
+2.17.1
+
diff --git a/package/network/services/dropbear/patches/021-backport-chacha20-poly1305-support.patch b/package/network/services/dropbear/patches/021-backport-chacha20-poly1305-support.patch
new file mode 100644
index 0000000000..2120b4593e
--- /dev/null
+++ b/package/network/services/dropbear/patches/021-backport-chacha20-poly1305-support.patch
@@ -0,0 +1,693 @@
+From 3cdf9ec918b37c17e12b33e4c244944d1ee836ca Mon Sep 17 00:00:00 2001
+From: Vladislav Grishenko <themiron@mail.ru>
+Date: Mon, 6 Apr 2020 23:28:09 +0500
+Subject: [PATCH] Add Chacha20-Poly1305 authenticated encryption
+
+* Add general AEAD approach.
+* Add chacha20-poly1305@openssh.com algo using LibTomCrypt chacha and
+  poly1305 routines.
+
+Chacha20-Poly1305 is generally faster than AES256 on CPU w/o dedicated
+AES instructions, having the same key size.
+Compiling in will add ~5,5kB to binary size on x86-64.
+---
+ Makefile.in                                 |   2 +-
+ algo.h                                      |   8 ++
+ chachapoly.c                                | 148 ++++++++++++++++++++
+ chachapoly.h                                |  44 ++++++
+ common-algo.c                               |  11 +-
+ common-kex.c                                |  44 ++++--
+ default_options.h                           |   6 +
+ libtomcrypt/src/headers/tomcrypt_dropbear.h |   4 +
+ packet.c                                    | 145 +++++++++++++------
+ session.h                                   |   4 +
+ sysoptions.h                                |   8 +-
+ 11 files changed, 368 insertions(+), 56 deletions(-)
+ create mode 100644 chachapoly.c
+ create mode 100644 chachapoly.h
+
+diff --git a/Makefile.in b/Makefile.in
+index aaf7b3b..3437cb2 100644
+--- a/Makefile.in
++++ b/Makefile.in
+@@ -53,7 +53,7 @@ CLIOBJS=cli-main.o cli-auth.o cli-authpasswd.o cli-kex.o \
+ CLISVROBJS=common-session.o packet.o common-algo.o common-kex.o \
+ 			common-channel.o common-chansession.o termcodes.o loginrec.o \
+ 			tcp-accept.o listener.o process-packet.o dh_groups.o \
+-			common-runopts.o circbuffer.o list.o netio.o
++			common-runopts.o circbuffer.o list.o netio.o chachapoly.o
+ 
+ KEYOBJS=dropbearkey.o
+ 
+diff --git a/algo.h b/algo.h
+index b12fb94..efd0d73 100644
+--- a/algo.h
++++ b/algo.h
+@@ -72,6 +72,14 @@ struct dropbear_cipher_mode {
+ 			unsigned long len, void *cipher_state);
+ 	int (*decrypt)(const unsigned char *ct, unsigned char *pt, 
+ 			unsigned long len, void *cipher_state);
++	int (*aead_crypt)(unsigned int seq,
++			const unsigned char *in, unsigned char *out,
++			unsigned long len, unsigned long taglen,
++			void *cipher_state, int direction);
++	int (*aead_getlength)(unsigned int seq,
++			const unsigned char *in, unsigned int *outlen,
++			unsigned long len, void *cipher_state);
++	const struct dropbear_hash *aead_mac;
+ };
+ 
+ struct dropbear_hash {
+diff --git a/chachapoly.c b/chachapoly.c
+new file mode 100644
+index 0000000..8fb06c5
+--- /dev/null
++++ b/chachapoly.c
+@@ -0,0 +1,148 @@
++/*
++ * Dropbear SSH
++ * 
++ * Copyright (c) 2002,2003 Matt Johnston
++ * Copyright (c) 2020 by Vladislav Grishenko
++ * All rights reserved.
++ * 
++ * Permission is hereby granted, free of charge, to any person obtaining a copy
++ * of this software and associated documentation files (the "Software"), to deal
++ * in the Software without restriction, including without limitation the rights
++ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
++ * copies of the Software, and to permit persons to whom the Software is
++ * furnished to do so, subject to the following conditions:
++ * 
++ * The above copyright notice and this permission notice shall be included in
++ * all copies or substantial portions of the Software.
++ * 
++ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
++ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
++ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
++ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
++ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
++ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
++ * SOFTWARE. */
++
++#include "includes.h"
++#include "algo.h"
++#include "dbutil.h"
++#include "chachapoly.h"
++
++#if DROPBEAR_CHACHA20POLY1305
++
++#define CHACHA20_KEY_LEN 32
++#define CHACHA20_BLOCKSIZE 8
++#define POLY1305_KEY_LEN 32
++#define POLY1305_TAG_LEN 16
++
++static const struct ltc_cipher_descriptor dummy = {.name = NULL};
++
++static const struct dropbear_hash dropbear_chachapoly_mac =
++	{NULL, POLY1305_KEY_LEN, POLY1305_TAG_LEN};
++
++const struct dropbear_cipher dropbear_chachapoly =
++	{&dummy, CHACHA20_KEY_LEN*2, CHACHA20_BLOCKSIZE};
++
++static int dropbear_chachapoly_start(int UNUSED(cipher), const unsigned char* UNUSED(IV),
++			const unsigned char *key, int keylen,
++			int UNUSED(num_rounds), dropbear_chachapoly_state *state) {
++	int err;
++
++	TRACE2(("enter dropbear_chachapoly_start"))
++
++	if (keylen != CHACHA20_KEY_LEN*2) {
++		return CRYPT_ERROR;
++	}
++
++	if ((err = chacha_setup(&state->chacha, key,
++				CHACHA20_KEY_LEN, 20)) != CRYPT_OK) {
++		return err;
++	}
++
++	if ((err = chacha_setup(&state->header, key + CHACHA20_KEY_LEN,
++				CHACHA20_KEY_LEN, 20) != CRYPT_OK)) {
++		return err;
++	}
++
++	TRACE2(("leave dropbear_chachapoly_start"))
++	return CRYPT_OK;
++}
++
++static int dropbear_chachapoly_crypt(unsigned int seq,
++			const unsigned char *in, unsigned char *out,
++			unsigned long len, unsigned long taglen,
++			dropbear_chachapoly_state *state, int direction) {
++	poly1305_state poly;
++	unsigned char seqbuf[8], key[POLY1305_KEY_LEN], tag[POLY1305_TAG_LEN];
++	int err;
++
++	TRACE2(("enter dropbear_chachapoly_crypt"))
++
++	if (len < 4 || taglen != POLY1305_TAG_LEN) {
++		return CRYPT_ERROR;
++	}
++
++	STORE64H((uint64_t)seq, seqbuf);
++	chacha_ivctr64(&state->chacha, seqbuf, sizeof(seqbuf), 0);
++	if ((err = chacha_keystream(&state->chacha, key, sizeof(key))) != CRYPT_OK) {
++		return err;
++	}
++
++	poly1305_init(&poly, key, sizeof(key));
++	if (direction == LTC_DECRYPT) {
++		poly1305_process(&poly, in, len);
++		poly1305_done(&poly, tag, &taglen);
++		if (constant_time_memcmp(in + len, tag, taglen) != 0) {
++			return CRYPT_ERROR;
++		}
++	}
++
++	chacha_ivctr64(&state->header, seqbuf, sizeof(seqbuf), 0);
++	if ((err = chacha_crypt(&state->header, in, 4, out)) != CRYPT_OK) {
++		return err;
++	}
++
++	chacha_ivctr64(&state->chacha, seqbuf, sizeof(seqbuf), 1);
++	if ((err = chacha_crypt(&state->chacha, in + 4, len - 4, out + 4)) != CRYPT_OK) {
++		return err;
++	}
++
++	if (direction == LTC_ENCRYPT) {
++		poly1305_process(&poly, out, len);
++		poly1305_done(&poly, out + len, &taglen);
++	}
++
++	TRACE2(("leave dropbear_chachapoly_crypt"))
++	return CRYPT_OK;
++}
++
++static int dropbear_chachapoly_getlength(unsigned int seq,
++			const unsigned char *in, unsigned int *outlen,
++			unsigned long len, dropbear_chachapoly_state *state) {
++	unsigned char seqbuf[8], buf[4];
++	int err;
++
++	TRACE2(("enter dropbear_chachapoly_getlength"))
++
++	if (len < sizeof(buf)) {
++		return CRYPT_ERROR;
++	}
++
++	STORE64H((uint64_t)seq, seqbuf);
++	chacha_ivctr64(&state->header, seqbuf, sizeof(seqbuf), 0);
++	if ((err = chacha_crypt(&state->header, in, sizeof(buf), buf)) != CRYPT_OK) {
++		return err;
++	}
++
++	LOAD32H(*outlen, buf);
++
++	TRACE2(("leave dropbear_chachapoly_getlength"))
++	return CRYPT_OK;
++}
++
++const struct dropbear_cipher_mode dropbear_mode_chachapoly =
++	{(void *)dropbear_chachapoly_start, NULL, NULL,
++	 (void *)dropbear_chachapoly_crypt,
++	 (void *)dropbear_chachapoly_getlength, &dropbear_chachapoly_mac};
++
++#endif /* DROPBEAR_CHACHA20POLY1305 */
+diff --git a/chachapoly.h b/chachapoly.h
+new file mode 100644
+index 0000000..5a7c5b2
+--- /dev/null
++++ b/chachapoly.h
+@@ -0,0 +1,44 @@
++/*
++ * Dropbear SSH
++ * 
++ * Copyright (c) 2002,2003 Matt Johnston
++ * Copyright (c) 2020 by Vladislav Grishenko
++ * All rights reserved.
++ * 
++ * Permission is hereby granted, free of charge, to any person obtaining a copy
++ * of this software and associated documentation files (the "Software"), to deal
++ * in the Software without restriction, including without limitation the rights
++ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
++ * copies of the Software, and to permit persons to whom the Software is
++ * furnished to do so, subject to the following conditions:
++ * 
++ * The above copyright notice and this permission notice shall be included in
++ * all copies or substantial portions of the Software.
++ * 
++ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
++ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
++ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
++ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
++ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
++ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
++ * SOFTWARE. */
++
++#ifndef DROPBEAR_DROPBEAR_CHACHAPOLY_H_
++#define DROPBEAR_DROPBEAR_CHACHAPOLY_H_
++
++#include "includes.h"
++#include "algo.h"
++
++#if DROPBEAR_CHACHA20POLY1305
++
++typedef struct {
++	chacha_state chacha;
++	chacha_state header;
++} dropbear_chachapoly_state;
++
++extern const struct dropbear_cipher dropbear_chachapoly;
++extern const struct dropbear_cipher_mode dropbear_mode_chachapoly;
++
++#endif /* DROPBEAR_CHACHA20POLY1305 */
++
++#endif /* DROPBEAR_DROPBEAR_CHACHAPOLY_H_ */
+diff --git a/common-algo.c b/common-algo.c
+index 558aad2..1436456 100644
+--- a/common-algo.c
++++ b/common-algo.c
+@@ -30,6 +30,7 @@
+ #include "dh_groups.h"
+ #include "ltc_prng.h"
+ #include "ecc.h"
++#include "chachapoly.h"
+ 
+ /* This file (algo.c) organises the ciphers which can be used, and is used to
+  * decide which ciphers/hashes/compression/signing to use during key exchange*/
+@@ -86,11 +87,11 @@ const struct dropbear_cipher dropbear_nocipher =
+  * about the symmetric_CBC vs symmetric_CTR cipher_state pointer */
+ #if DROPBEAR_ENABLE_CBC_MODE
+ const struct dropbear_cipher_mode dropbear_mode_cbc =
+-	{(void*)cbc_start, (void*)cbc_encrypt, (void*)cbc_decrypt};
++	{(void*)cbc_start, (void*)cbc_encrypt, (void*)cbc_decrypt, NULL, NULL, NULL};
+ #endif /* DROPBEAR_ENABLE_CBC_MODE */
+ 
+ const struct dropbear_cipher_mode dropbear_mode_none =
+-	{void_start, void_cipher, void_cipher};
++	{void_start, void_cipher, void_cipher, NULL, NULL, NULL};
+ 
+ #if DROPBEAR_ENABLE_CTR_MODE
+ /* a wrapper to make ctr_start and cbc_start look the same */
+@@ -101,7 +102,7 @@ static int dropbear_big_endian_ctr_start(int cipher,
+ 	return ctr_start(cipher, IV, key, keylen, num_rounds, CTR_COUNTER_BIG_ENDIAN, ctr);
+ }
+ const struct dropbear_cipher_mode dropbear_mode_ctr =
+-	{(void*)dropbear_big_endian_ctr_start, (void*)ctr_encrypt, (void*)ctr_decrypt};
++	{(void*)dropbear_big_endian_ctr_start, (void*)ctr_encrypt, (void*)ctr_decrypt, NULL, NULL, NULL};
+ #endif /* DROPBEAR_ENABLE_CTR_MODE */
+ 
+ /* Mapping of ssh hashes to libtomcrypt hashes, including keysize etc.
+@@ -137,6 +138,10 @@ const struct dropbear_hash dropbear_nohash =
+  * that is also supported by the server will get used. */
+ 
+ algo_type sshciphers[] = {
++#if DROPBEAR_CHACHA20POLY1305
++	{"chacha20-poly1305@openssh.com", 0, &dropbear_chachapoly, 1, &dropbear_mode_chachapoly},
++#endif
++
+ #if DROPBEAR_ENABLE_CTR_MODE
+ #if DROPBEAR_AES128
+ 	{"aes128-ctr", 0, &dropbear_aes128, 1, &dropbear_mode_ctr},
+diff --git a/common-kex.c b/common-kex.c
+index 16b7e27..5e2923f 100644
+--- a/common-kex.c
++++ b/common-kex.c
+@@ -329,9 +329,12 @@ static void gen_new_keys() {
+ 	hashkeys(S2C_key, sizeof(S2C_key), &hs, 'D');
+ 
+ 	if (ses.newkeys->recv.algo_crypt->cipherdesc != NULL) {
+-		int recv_cipher = find_cipher(ses.newkeys->recv.algo_crypt->cipherdesc->name);
+-		if (recv_cipher < 0)
+-			dropbear_exit("Crypto error");
++		int recv_cipher = -1;
++		if (ses.newkeys->recv.algo_crypt->cipherdesc->name != NULL) {
++			recv_cipher = find_cipher(ses.newkeys->recv.algo_crypt->cipherdesc->name);
++			if (recv_cipher < 0)
++				dropbear_exit("Crypto error");
++		}
+ 		if (ses.newkeys->recv.crypt_mode->start(recv_cipher, 
+ 				recv_IV, recv_key, 
+ 				ses.newkeys->recv.algo_crypt->keysize, 0, 
+@@ -341,9 +344,12 @@ static void gen_new_keys() {
+ 	}
+ 
+ 	if (ses.newkeys->trans.algo_crypt->cipherdesc != NULL) {
+-		int trans_cipher = find_cipher(ses.newkeys->trans.algo_crypt->cipherdesc->name);
+-		if (trans_cipher < 0)
+-			dropbear_exit("Crypto error");
++		int trans_cipher = -1;
++		if (ses.newkeys->trans.algo_crypt->cipherdesc->name != NULL) {
++			trans_cipher = find_cipher(ses.newkeys->trans.algo_crypt->cipherdesc->name);
++			if (trans_cipher < 0)
++				dropbear_exit("Crypto error");
++		}
+ 		if (ses.newkeys->trans.crypt_mode->start(trans_cipher, 
+ 				trans_IV, trans_key, 
+ 				ses.newkeys->trans.algo_crypt->keysize, 0, 
+@@ -868,19 +874,29 @@ static void read_kex_algos() {
+ 
+ 	/* mac_algorithms_client_to_server */
+ 	c2s_hash_algo = buf_match_algo(ses.payload, sshhashes, NULL, NULL);
++#if DROPBEAR_AEAD_MODE
++	if (((struct dropbear_cipher_mode*)c2s_cipher_algo->mode)->aead_crypt != NULL) {
++		c2s_hash_algo = NULL;
++	} else
++#endif
+ 	if (c2s_hash_algo == NULL) {
+ 		erralgo = "mac c->s";
+ 		goto error;
+ 	}
+-	TRACE(("hash c2s is  %s", c2s_hash_algo->name))
++	TRACE(("hash c2s is  %s", c2s_hash_algo ? c2s_hash_algo->name : "<implicit>"))
+ 
+ 	/* mac_algorithms_server_to_client */
+ 	s2c_hash_algo = buf_match_algo(ses.payload, sshhashes, NULL, NULL);
++#if DROPBEAR_AEAD_MODE
++	if (((struct dropbear_cipher_mode*)s2c_cipher_algo->mode)->aead_crypt != NULL) {
++		s2c_hash_algo = NULL;
++	} else
++#endif
+ 	if (s2c_hash_algo == NULL) {
+ 		erralgo = "mac s->c";
+ 		goto error;
+ 	}
+-	TRACE(("hash s2c is  %s", s2c_hash_algo->name))
++	TRACE(("hash s2c is  %s", s2c_hash_algo ? s2c_hash_algo->name : "<implicit>"))
+ 
+ 	/* compression_algorithms_client_to_server */
+ 	c2s_comp_algo = buf_match_algo(ses.payload, ses.compress_algos, NULL, NULL);
+@@ -925,8 +941,14 @@ static void read_kex_algos() {
+ 		ses.newkeys->trans.crypt_mode =
+ 			(struct dropbear_cipher_mode*)c2s_cipher_algo->mode;
+ 		ses.newkeys->recv.algo_mac = 
++#if DROPBEAR_AEAD_MODE
++			s2c_hash_algo == NULL ? ses.newkeys->recv.crypt_mode->aead_mac :
++#endif
+ 			(struct dropbear_hash*)s2c_hash_algo->data;
+ 		ses.newkeys->trans.algo_mac = 
++#if DROPBEAR_AEAD_MODE
++			c2s_hash_algo == NULL ? ses.newkeys->trans.crypt_mode->aead_mac :
++#endif
+ 			(struct dropbear_hash*)c2s_hash_algo->data;
+ 		ses.newkeys->recv.algo_comp = s2c_comp_algo->val;
+ 		ses.newkeys->trans.algo_comp = c2s_comp_algo->val;
+@@ -941,8 +963,14 @@ static void read_kex_algos() {
+ 		ses.newkeys->trans.crypt_mode =
+ 			(struct dropbear_cipher_mode*)s2c_cipher_algo->mode;
+ 		ses.newkeys->recv.algo_mac = 
++#if DROPBEAR_AEAD_MODE
++			c2s_hash_algo == NULL ? ses.newkeys->recv.crypt_mode->aead_mac :
++#endif
+ 			(struct dropbear_hash*)c2s_hash_algo->data;
+ 		ses.newkeys->trans.algo_mac = 
++#if DROPBEAR_AEAD_MODE
++			s2c_hash_algo == NULL ? ses.newkeys->trans.crypt_mode->aead_mac :
++#endif
+ 			(struct dropbear_hash*)s2c_hash_algo->data;
+ 		ses.newkeys->recv.algo_comp = c2s_comp_algo->val;
+ 		ses.newkeys->trans.algo_comp = s2c_comp_algo->val;
+diff --git a/default_options.h b/default_options.h
+index bafbb07..1a2ab10 100644
+--- a/default_options.h
++++ b/default_options.h
+@@ -99,6 +99,12 @@ IMPORTANT: Some options will require "make clean" after changes */
+  * and forwards compatibility */
+ #define DROPBEAR_ENABLE_CTR_MODE 1
+ 
++/* Enable Chacha20-Poly1305 authenticated encryption mode. This is
++ * generally faster than AES256 on CPU w/o dedicated AES instructions,
++ * having the same key size.
++ * Compiling in will add ~5,5kB to binary size on x86-64 */
++#define DROPBEAR_CHACHA20POLY1305 1
++
+ /* Message integrity. sha2-256 is recommended as a default, 
+    sha1 for compatibility */
+ #define DROPBEAR_SHA1_HMAC 1
+diff --git a/libtomcrypt/src/headers/tomcrypt_dropbear.h b/libtomcrypt/src/headers/tomcrypt_dropbear.h
+index b0ce45b..59960e5 100644
+--- a/libtomcrypt/src/headers/tomcrypt_dropbear.h
++++ b/libtomcrypt/src/headers/tomcrypt_dropbear.h
+@@ -35,6 +35,10 @@
+ #define LTC_CTR_MODE
+ #endif
+ 
++#if DROPBEAR_CHACHA20POLY1305
++#define LTC_CHACHA
++#define LTC_POLY1305
++#endif
+ 
+ #if DROPBEAR_SHA512
+ #define LTC_SHA512
+diff --git a/packet.c b/packet.c
+index 9fda0d6..0454726 100644
+--- a/packet.c
++++ b/packet.c
+@@ -215,7 +215,7 @@ static int read_packet_init() {
+ 
+ 	unsigned int maxlen;
+ 	int slen;
+-	unsigned int len;
++	unsigned int len, plen;
+ 	unsigned int blocksize;
+ 	unsigned int macsize;
+ 
+@@ -254,21 +254,35 @@ static int read_packet_init() {
+ 	/* now we have the first block, need to get packet length, so we decrypt
+ 	 * the first block (only need first 4 bytes) */
+ 	buf_setpos(ses.readbuf, 0);
+-	if (ses.keys->recv.crypt_mode->decrypt(buf_getptr(ses.readbuf, blocksize), 
+-				buf_getwriteptr(ses.readbuf, blocksize),
+-				blocksize,
+-				&ses.keys->recv.cipher_state) != CRYPT_OK) {
+-		dropbear_exit("Error decrypting");
++#if DROPBEAR_AEAD_MODE
++	if (ses.keys->recv.crypt_mode->aead_crypt) {
++		if (ses.keys->recv.crypt_mode->aead_getlength(ses.recvseq,
++					buf_getptr(ses.readbuf, blocksize), &plen,
++					blocksize,
++					&ses.keys->recv.cipher_state) != CRYPT_OK) {
++			dropbear_exit("Error decrypting");
++		}
++		len = plen + 4 + macsize;
++	} else
++#endif
++	{
++		if (ses.keys->recv.crypt_mode->decrypt(buf_getptr(ses.readbuf, blocksize), 
++					buf_getwriteptr(ses.readbuf, blocksize),
++					blocksize,
++					&ses.keys->recv.cipher_state) != CRYPT_OK) {
++			dropbear_exit("Error decrypting");
++		}
++		plen = buf_getint(ses.readbuf) + 4;
++		len = plen + macsize;
+ 	}
+-	len = buf_getint(ses.readbuf) + 4 + macsize;
+ 
+ 	TRACE2(("packet size is %u, block %u mac %u", len, blocksize, macsize))
+ 
+ 
+ 	/* check packet length */
+ 	if ((len > RECV_MAX_PACKET_LEN) ||
+-		(len < MIN_PACKET_LEN + macsize) ||
+-		((len - macsize) % blocksize != 0)) {
++		(plen < blocksize) ||
++		(plen % blocksize != 0)) {
+ 		dropbear_exit("Integrity error (bad packet size %u)", len);
+ 	}
+ 
+@@ -294,23 +308,42 @@ void decrypt_packet() {
+ 
+ 	ses.kexstate.datarecv += ses.readbuf->len;
+ 
+-	/* we've already decrypted the first blocksize in read_packet_init */
+-	buf_setpos(ses.readbuf, blocksize);
+-
+-	/* decrypt it in-place */
+-	len = ses.readbuf->len - macsize - ses.readbuf->pos;
+-	if (ses.keys->recv.crypt_mode->decrypt(
+-				buf_getptr(ses.readbuf, len), 
+-				buf_getwriteptr(ses.readbuf, len),
+-				len,
+-				&ses.keys->recv.cipher_state) != CRYPT_OK) {
+-		dropbear_exit("Error decrypting");
+-	}
+-	buf_incrpos(ses.readbuf, len);
++#if DROPBEAR_AEAD_MODE
++	if (ses.keys->recv.crypt_mode->aead_crypt) {
++		/* first blocksize is not decrypted yet */
++		buf_setpos(ses.readbuf, 0);
++
++		/* decrypt it in-place */
++		len = ses.readbuf->len - macsize - ses.readbuf->pos;
++		if (ses.keys->recv.crypt_mode->aead_crypt(ses.recvseq,
++					buf_getptr(ses.readbuf, len + macsize),
++					buf_getwriteptr(ses.readbuf, len),
++					len, macsize,
++					&ses.keys->recv.cipher_state, LTC_DECRYPT) != CRYPT_OK) {
++			dropbear_exit("Error decrypting");
++		}
++		buf_incrpos(ses.readbuf, len);
++	} else
++#endif
++	{
++		/* we've already decrypted the first blocksize in read_packet_init */
++		buf_setpos(ses.readbuf, blocksize);
++
++		/* decrypt it in-place */
++		len = ses.readbuf->len - macsize - ses.readbuf->pos;
++		if (ses.keys->recv.crypt_mode->decrypt(
++					buf_getptr(ses.readbuf, len), 
++					buf_getwriteptr(ses.readbuf, len),
++					len,
++					&ses.keys->recv.cipher_state) != CRYPT_OK) {
++			dropbear_exit("Error decrypting");
++		}
++		buf_incrpos(ses.readbuf, len);
+ 
+-	/* check the hmac */
+-	if (checkmac() != DROPBEAR_SUCCESS) {
+-		dropbear_exit("Integrity error");
++		/* check the hmac */
++		if (checkmac() != DROPBEAR_SUCCESS) {
++			dropbear_exit("Integrity error");
++		}
+ 	}
+ 
+ 	/* get padding length */
+@@ -557,9 +590,16 @@ void encrypt_packet() {
+ 	buf_setpos(ses.writepayload, 0);
+ 	buf_setlen(ses.writepayload, 0);
+ 
+-	/* length of padding - packet length must be a multiple of blocksize,
+-	 * with a minimum of 4 bytes of padding */
+-	padlen = blocksize - (writebuf->len) % blocksize;
++	/* length of padding - packet length excluding the packetlength uint32
++	 * field in aead mode must be a multiple of blocksize, with a minimum of
++	 * 4 bytes of padding */
++	len = writebuf->len;
++#if DROPBEAR_AEAD_MODE
++	if (ses.keys->trans.crypt_mode->aead_crypt) {
++		len -= 4;
++	}
++#endif
++	padlen = blocksize - len % blocksize;
+ 	if (padlen < 4) {
+ 		padlen += blocksize;
+ 	}
+@@ -579,23 +619,42 @@ void encrypt_packet() {
+ 	buf_incrlen(writebuf, padlen);
+ 	genrandom(buf_getptr(writebuf, padlen), padlen);
+ 
+-	make_mac(ses.transseq, &ses.keys->trans, writebuf, writebuf->len, mac_bytes);
++#if DROPBEAR_AEAD_MODE
++	if (ses.keys->trans.crypt_mode->aead_crypt) {
++		/* do the actual encryption, in-place */
++		buf_setpos(writebuf, 0);
++		/* encrypt it in-place*/
++		len = writebuf->len;
++		buf_incrlen(writebuf, mac_size);
++		if (ses.keys->trans.crypt_mode->aead_crypt(ses.transseq,
++					buf_getptr(writebuf, len),
++					buf_getwriteptr(writebuf, len + mac_size),
++					len, mac_size,
++					&ses.keys->trans.cipher_state, LTC_ENCRYPT) != CRYPT_OK) {
++			dropbear_exit("Error encrypting");
++		}
++		buf_incrpos(writebuf, len + mac_size);
++	} else
++#endif
++	{
++		make_mac(ses.transseq, &ses.keys->trans, writebuf, writebuf->len, mac_bytes);
++
++		/* do the actual encryption, in-place */
++		buf_setpos(writebuf, 0);
++		/* encrypt it in-place*/
++		len = writebuf->len;
++		if (ses.keys->trans.crypt_mode->encrypt(
++					buf_getptr(writebuf, len),
++					buf_getwriteptr(writebuf, len),
++					len,
++					&ses.keys->trans.cipher_state) != CRYPT_OK) {
++			dropbear_exit("Error encrypting");
++		}
++		buf_incrpos(writebuf, len);
+ 
+-	/* do the actual encryption, in-place */
+-	buf_setpos(writebuf, 0);
+-	/* encrypt it in-place*/
+-	len = writebuf->len;
+-	if (ses.keys->trans.crypt_mode->encrypt(
+-				buf_getptr(writebuf, len),
+-				buf_getwriteptr(writebuf, len),
+-				len,
+-				&ses.keys->trans.cipher_state) != CRYPT_OK) {
+-		dropbear_exit("Error encrypting");
++		/* stick the MAC on it */
++		buf_putbytes(writebuf, mac_bytes, mac_size);
+ 	}
+-	buf_incrpos(writebuf, len);
+-
+-	/* stick the MAC on it */
+-	buf_putbytes(writebuf, mac_bytes, mac_size);
+ 
+ 	/* Update counts */
+ 	ses.kexstate.datatrans += writebuf->len;
+diff --git a/session.h b/session.h
+index e436882..a8f8914 100644
+--- a/session.h
++++ b/session.h
+@@ -41,6 +41,7 @@
+ #include "chansession.h"
+ #include "dbutil.h"
+ #include "netio.h"
++#include "chachapoly.h"
+ 
+ void common_session_init(int sock_in, int sock_out);
+ void session_loop(void(*loophandler)(void)) ATTRIB_NORETURN;
+@@ -80,6 +81,9 @@ struct key_context_directional {
+ 		symmetric_CBC cbc;
+ #if DROPBEAR_ENABLE_CTR_MODE
+ 		symmetric_CTR ctr;
++#endif
++#if DROPBEAR_CHACHA20POLY1305
++		dropbear_chachapoly_state chachapoly;
+ #endif
+ 	} cipher_state;
+ 	unsigned char mackey[MAX_MAC_LEN];
+diff --git a/sysoptions.h b/sysoptions.h
+index 2c27caf..2432779 100644
+--- a/sysoptions.h
++++ b/sysoptions.h
+@@ -92,7 +92,11 @@
+ #define MD5_HASH_SIZE 16
+ #define MAX_HASH_SIZE 64 /* sha512 */
+ 
++#if DROPBEAR_CHACHA20POLY1305
++#define MAX_KEY_LEN 64 /* 2 x 256 bits for chacha20 */
++#else
+ #define MAX_KEY_LEN 32 /* 256 bits for aes256 etc */
++#endif
+ #define MAX_IV_LEN 20 /* must be same as max blocksize,  */
+ 
+ #if DROPBEAR_SHA2_512_HMAC
+@@ -207,6 +211,8 @@ If you test it please contact the Dropbear author */
+ 
+ #define DROPBEAR_TWOFISH ((DROPBEAR_TWOFISH256) || (DROPBEAR_TWOFISH128))
+ 
++#define DROPBEAR_AEAD_MODE ((DROPBEAR_CHACHA20POLY1305))
++
+ #define DROPBEAR_CLI_ANYTCPFWD ((DROPBEAR_CLI_REMOTETCPFWD) || (DROPBEAR_CLI_LOCALTCPFWD))
+ 
+ #define DROPBEAR_TCP_ACCEPT ((DROPBEAR_CLI_LOCALTCPFWD) || (DROPBEAR_SVR_REMOTETCPFWD))
+@@ -249,7 +255,7 @@ If you test it please contact the Dropbear author */
+ #endif
+ 
+ #if !(DROPBEAR_AES128 || DROPBEAR_3DES || DROPBEAR_AES256 || DROPBEAR_BLOWFISH \
+-      || DROPBEAR_TWOFISH256 || DROPBEAR_TWOFISH128)
++      || DROPBEAR_TWOFISH256 || DROPBEAR_TWOFISH128 || DROPBEAR_CHACHA20POLY1305)
+ 	#error "At least one encryption algorithm must be enabled. AES128 is recommended."
+ #endif
+ 
+-- 
+2.17.1
+
author	Vladislav Grishenko <themiron@mail.ru>	2020-04-13 03:24:28 +0500
committer	Hans Dedecker <dedeckeh@gmail.com>	2020-05-30 21:27:10 +0200
commit	f166cf9ca07ceb023db356532cf4154ef433322a (patch)
tree	dbc22710b222fb4e437a3d581fa085c8e423033d /package/network/services
parent	02f08056bcbc5f014894b7edcea43f2ff822fd90 (diff)
download	upstream-f166cf9ca07ceb023db356532cf4154ef433322a.tar.gz upstream-f166cf9ca07ceb023db356532cf4154ef433322a.tar.bz2 upstream-f166cf9ca07ceb023db356532cf4154ef433322a.zip