px5g: support EC keys

This adds an 'eckey' command to generate an EC key, with an optional
curve name argument, with P-256 as default.

For the 'selfsigned' command, it adds an 'ec' algorithm argument to the
'-newkey' option, and a '-pkeyopt ec_paramgen_curve:<curvename>' option,
mirroring the way openssl specifies the curve name.

Notice that curve names are not necessarily the same in mbedtls and
openssl.  In particular, secp256r1 works for mbedtls, but openssl uses
prime256v1 instead. px5g uses mbedtls, but short NIST curve names P-256
and P-384 are specifically supported.

Package size increased by about 900 bytes (arm).

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>

2 files changed, 71 insertions, 19 deletions

diff --git a/package/utils/px5g/Makefile b/package/utils/px5g/Makefile
index 592d19663d..f4be6cb5ee 100644
--- a/package/utils/px5g/Makefile
+++ b/package/utils/px5g/Makefile
@@ -8,7 +8,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=px5g
-PKG_RELEASE:=8
+PKG_RELEASE:=9
 PKG_LICENSE:=LGPL-2.1
 
 PKG_USE_MIPS16:=0
@@ -52,7 +52,7 @@ ifeq ($(BUILD_VARIANT),standalone)
   TARGET_LDFLAGS := -Wl,-Bstatic $(TARGET_LDFLAGS) -Wl,-Bdynamic
 endif
 
-TARGET_CFLAGS += -Wl,--gc-sections
+TARGET_CFLAGS += -Wl,--gc-sections -Wall -Werror
 
 define Build/Compile
 	$(TARGET_CC) $(TARGET_CPPFLAGS) $(TARGET_CFLAGS) -o $(PKG_BUILD_DIR)/px5g px5g.c $(TARGET_LDFLAGS)
diff --git a/package/utils/px5g/px5g.c b/package/utils/px5g/px5g.c
index f0fe4dcfd3..0b72154509 100644
--- a/package/utils/px5g/px5g.c
+++ b/package/utils/px5g/px5g.c
@@ -32,6 +32,7 @@
 
 #include <mbedtls/bignum.h>
 #include <mbedtls/x509_crt.h>
+#include <mbedtls/ecp.h>
 #include <mbedtls/rsa.h>
 #include <mbedtls/pk.h>
 
@@ -73,6 +74,23 @@ static void write_file(const char *path, int len, bool pem)
 	fclose(f);
 }
 
+static mbedtls_ecp_group_id ecp_curve(const char *name)
+{
+	const mbedtls_ecp_curve_info *curve_info;
+
+	if (!strcmp(name, "P-256"))
+		return MBEDTLS_ECP_DP_SECP256R1;
+	else if (!strcmp(name, "P-384"))
+		return MBEDTLS_ECP_DP_SECP384R1;
+	else if (!strcmp(name, "P-521"))
+		return MBEDTLS_ECP_DP_SECP521R1;
+	curve_info = mbedtls_ecp_curve_info_from_name(name);
+	if (curve_info == NULL)
+		return MBEDTLS_ECP_DP_NONE;
+	else
+		return curve_info->grp_id;
+}
+
 static void write_key(mbedtls_pk_context *key, const char *path, bool pem)
 {
 	int len = 0;
@@ -89,24 +107,33 @@ static void write_key(mbedtls_pk_context *key, const char *path, bool pem)
 	write_file(path, len, pem);
 }
 
-static void gen_key(mbedtls_pk_context *key, int ksize, int exp, bool pem)
+static void gen_key(mbedtls_pk_context *key, bool rsa, int ksize, int exp,
+		    mbedtls_ecp_group_id curve, bool pem)
 {
 	mbedtls_pk_init(key);
-	fprintf(stderr, "Generating RSA private key, %i bit long modulus\n", ksize);
-	mbedtls_pk_setup(key, mbedtls_pk_info_from_type(MBEDTLS_PK_RSA));
-	if (mbedtls_rsa_gen_key(mbedtls_pk_rsa(*key), _urandom, NULL, ksize, exp)) {
-		fprintf(stderr, "error: key generation failed\n");
-		exit(1);
+	if (rsa) {
+		fprintf(stderr, "Generating RSA private key, %i bit long modulus\n", ksize);
+		mbedtls_pk_setup(key, mbedtls_pk_info_from_type(MBEDTLS_PK_RSA));
+		if (!mbedtls_rsa_gen_key(mbedtls_pk_rsa(*key), _urandom, NULL, ksize, exp))
+			return;
+	} else {
+		fprintf(stderr, "Generating EC private key\n");
+		mbedtls_pk_setup(key, mbedtls_pk_info_from_type(MBEDTLS_PK_ECKEY));
+		if (!mbedtls_ecp_gen_key(curve, mbedtls_pk_ec(*key), _urandom, NULL))
+			return;
 	}
+	fprintf(stderr, "error: key generation failed\n");
+	exit(1);
 }
 
-int rsakey(char **arg)
+int dokey(bool rsa, char **arg)
 {
 	mbedtls_pk_context key;
 	unsigned int ksize = 512;
 	int exp = 65537;
 	char *path = NULL;
 	bool pem = true;
+	mbedtls_ecp_group_id curve = MBEDTLS_ECP_DP_SECP256R1;
 
 	while (*arg && **arg == '-') {
 		if (!strcmp(*arg, "-out") && arg[1]) {
@@ -120,10 +147,17 @@ int rsakey(char **arg)
 		arg++;
 	}
 
-	if (*arg)
+	if (*arg && rsa) {
 		ksize = (unsigned int)atoi(*arg);
+	} else if (*arg) {
+		curve = ecp_curve((const char *)*arg);
+		if (curve == MBEDTLS_ECP_DP_NONE) {
+			fprintf(stderr, "error: invalid curve name: %s\n", *arg);
+			return 1;
+		}
+	}
 
-	gen_key(&key, ksize, exp, pem);
+	gen_key(&key, rsa, ksize, exp, curve, pem);
 	write_key(&key, path, pem);
 
 	mbedtls_pk_free(&key);
@@ -146,20 +180,37 @@ int selfsigned(char **arg)
 	time_t from = time(NULL), to;
 	char fstr[20], tstr[20], sstr[17];
 	int len;
+	bool rsa = true;
+	mbedtls_ecp_group_id curve = MBEDTLS_ECP_DP_SECP256R1;
 
 	while (*arg && **arg == '-') {
 		if (!strcmp(*arg, "-der")) {
 			pem = false;
 		} else if (!strcmp(*arg, "-newkey") && arg[1]) {
-			if (strncmp(arg[1], "rsa:", 4)) {
-				fprintf(stderr, "error: invalid algorithm");
+			if (!strncmp(arg[1], "rsa:", 4)) {
+				rsa = true;
+				ksize = (unsigned int)atoi(arg[1] + 4);
+			} else if (!strcmp(arg[1], "ec")) {
+				rsa = false;
+			} else {
+				fprintf(stderr, "error: invalid algorithm\n");
 				return 1;
 			}
-			ksize = (unsigned int)atoi(arg[1] + 4);
 			arg++;
 		} else if (!strcmp(*arg, "-days") && arg[1]) {
 			days = (unsigned int)atoi(arg[1]);
 			arg++;
+		} else if (!strcmp(*arg, "-pkeyopt") && arg[1]) {
+			if (strncmp(arg[1], "ec_paramgen_curve:", 18)) {
+				fprintf(stderr, "error: invalid pkey option: %s\n", arg[1]);
+				return 1;
+			}
+			curve = ecp_curve((const char *)(arg[1] + 18));
+			if (curve == MBEDTLS_ECP_DP_NONE) {
+				fprintf(stderr, "error: invalid curve name: %s\n", arg[1] + 18);
+				return 1;
+			}
+			arg++;
 		} else if (!strcmp(*arg, "-keyout") && arg[1]) {
 			keypath = arg[1];
 			arg++;
@@ -196,8 +247,7 @@ int selfsigned(char **arg)
 		}
 		arg++;
 	}
-
-	gen_key(&key, ksize, exp, pem);
+	gen_key(&key, rsa, ksize, exp, curve, pem);
 
 	if (keypath)
 		write_key(&key, keypath, pem);
@@ -223,7 +273,7 @@ int selfsigned(char **arg)
 	mbedtls_x509write_crt_set_subject_key_identifier(&cert);
 	mbedtls_x509write_crt_set_authority_key_identifier(&cert);
 
-	_urandom(NULL, buf, 8);
+	_urandom(NULL, (void *) buf, 8);
 	for (len = 0; len < 8; len++)
 		sprintf(sstr + len*2, "%02x", (unsigned char) buf[len]);
 
@@ -260,8 +310,10 @@ int main(int argc, char *argv[])
 
 	if (!argv[1]) {
 		//Usage
+	} else if (!strcmp(argv[1], "eckey")) {
+		return dokey(false, argv+2);
 	} else if (!strcmp(argv[1], "rsakey")) {
-		return rsakey(argv+2);
+		return dokey(true, argv+2);
 	} else if (!strcmp(argv[1], "selfsigned")) {
 		return selfsigned(argv+2);
 	}
@@ -269,6 +321,6 @@ int main(int argc, char *argv[])
 	fprintf(stderr,
 		"PX5G X.509 Certificate Generator Utility v" PX5G_VERSION "\n" PX5G_COPY
 		"\nbased on PolarSSL by Christophe Devine and Paul Bakker\n\n");
-	fprintf(stderr, "Usage: %s [rsakey|selfsigned]\n", *argv);
+	fprintf(stderr, "Usage: %s [eckey|rsakey|selfsigned]\n", *argv);
 	return 1;
 }