ed25519 support (#4114)

* ed25519 support

* review feedback

1 files changed, 154 insertions, 0 deletions

diff --git a/src/cryptography/hazmat/backends/openssl/ed25519.py b/src/cryptography/hazmat/backends/openssl/ed25519.py
new file mode 100644
index 00000000..15c1b1ec
--- /dev/null
+++ b/src/cryptography/hazmat/backends/openssl/ed25519.py
@@ -0,0 +1,154 @@
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
+
+from __future__ import absolute_import, division, print_function
+
+from cryptography import exceptions, utils
+from cryptography.hazmat.primitives import serialization
+from cryptography.hazmat.primitives.asymmetric.ed25519 import (
+    Ed25519PrivateKey, Ed25519PublicKey
+)
+
+_ED25519_KEY_SIZE = 32
+_ED25519_SIG_SIZE = 64
+
+
+@utils.register_interface(Ed25519PublicKey)
+class _Ed25519PublicKey(object):
+    def __init__(self, backend, evp_pkey):
+        self._backend = backend
+        self._evp_pkey = evp_pkey
+
+    def public_bytes(self, encoding, format):
+        if (
+            encoding is serialization.Encoding.Raw or
+            format is serialization.PublicFormat.Raw
+        ):
+            if (
+                encoding is not serialization.Encoding.Raw or
+                format is not serialization.PublicFormat.Raw
+            ):
+                raise ValueError(
+                    "When using Raw both encoding and format must be Raw"
+                )
+
+            return self._raw_public_bytes()
+
+        if (
+            encoding in serialization._PEM_DER and
+            format is not serialization.PublicFormat.SubjectPublicKeyInfo
+        ):
+            raise ValueError(
+                "format must be SubjectPublicKeyInfo when encoding is PEM or "
+                "DER"
+            )
+
+        return self._backend._public_key_bytes(
+            encoding, format, self, self._evp_pkey, None
+        )
+
+    def _raw_public_bytes(self):
+        buf = self._backend._ffi.new("unsigned char []", _ED25519_KEY_SIZE)
+        buflen = self._backend._ffi.new("size_t *", _ED25519_KEY_SIZE)
+        res = self._backend._lib.EVP_PKEY_get_raw_public_key(
+            self._evp_pkey, buf, buflen
+        )
+        self._backend.openssl_assert(res == 1)
+        self._backend.openssl_assert(buflen[0] == _ED25519_KEY_SIZE)
+        return self._backend._ffi.buffer(buf, _ED25519_KEY_SIZE)[:]
+
+    def verify(self, signature, data):
+        evp_md_ctx = self._backend._lib.Cryptography_EVP_MD_CTX_new()
+        self._backend.openssl_assert(evp_md_ctx != self._backend._ffi.NULL)
+        evp_md_ctx = self._backend._ffi.gc(
+            evp_md_ctx, self._backend._lib.Cryptography_EVP_MD_CTX_free
+        )
+        res = self._backend._lib.EVP_DigestVerifyInit(
+            evp_md_ctx, self._backend._ffi.NULL, self._backend._ffi.NULL,
+            self._backend._ffi.NULL, self._evp_pkey
+        )
+        self._backend.openssl_assert(res == 1)
+        res = self._backend._lib.EVP_DigestVerify(
+            evp_md_ctx, signature, len(signature), data, len(data)
+        )
+        if res != 1:
+            self._backend._consume_errors()
+            raise exceptions.InvalidSignature
+
+
+@utils.register_interface(Ed25519PrivateKey)
+class _Ed25519PrivateKey(object):
+    def __init__(self, backend, evp_pkey):
+        self._backend = backend
+        self._evp_pkey = evp_pkey
+
+    def public_key(self):
+        buf = self._backend._ffi.new("unsigned char []", _ED25519_KEY_SIZE)
+        buflen = self._backend._ffi.new("size_t *", _ED25519_KEY_SIZE)
+        res = self._backend._lib.EVP_PKEY_get_raw_public_key(
+            self._evp_pkey, buf, buflen
+        )
+        self._backend.openssl_assert(res == 1)
+        self._backend.openssl_assert(buflen[0] == _ED25519_KEY_SIZE)
+        public_bytes = self._backend._ffi.buffer(buf)[:]
+        return self._backend.ed25519_load_public_bytes(public_bytes)
+
+    def sign(self, data):
+        evp_md_ctx = self._backend._lib.Cryptography_EVP_MD_CTX_new()
+        self._backend.openssl_assert(evp_md_ctx != self._backend._ffi.NULL)
+        evp_md_ctx = self._backend._ffi.gc(
+            evp_md_ctx, self._backend._lib.Cryptography_EVP_MD_CTX_free
+        )
+        res = self._backend._lib.EVP_DigestSignInit(
+            evp_md_ctx, self._backend._ffi.NULL, self._backend._ffi.NULL,
+            self._backend._ffi.NULL, self._evp_pkey
+        )
+        self._backend.openssl_assert(res == 1)
+        buf = self._backend._ffi.new("unsigned char[]", _ED25519_SIG_SIZE)
+        buflen = self._backend._ffi.new("size_t *", len(buf))
+        res = self._backend._lib.EVP_DigestSign(
+            evp_md_ctx, buf, buflen, data, len(data)
+        )
+        self._backend.openssl_assert(res == 1)
+        self._backend.openssl_assert(buflen[0] == _ED25519_SIG_SIZE)
+        return self._backend._ffi.buffer(buf, buflen[0])[:]
+
+    def private_bytes(self, encoding, format, encryption_algorithm):
+        if (
+            encoding is serialization.Encoding.Raw or
+            format is serialization.PublicFormat.Raw
+        ):
+            if (
+                format is not serialization.PrivateFormat.Raw or
+                encoding is not serialization.Encoding.Raw or not
+                isinstance(encryption_algorithm, serialization.NoEncryption)
+            ):
+                raise ValueError(
+                    "When using Raw both encoding and format must be Raw "
+                    "and encryption_algorithm must be NoEncryption"
+                )
+
+            return self._raw_private_bytes()
+
+        if (
+            encoding in serialization._PEM_DER and
+            format is not serialization.PrivateFormat.PKCS8
+        ):
+            raise ValueError(
+                "format must be PKCS8 when encoding is PEM or DER"
+            )
+
+        return self._backend._private_key_bytes(
+            encoding, format, encryption_algorithm, self._evp_pkey, None
+        )
+
+    def _raw_private_bytes(self):
+        buf = self._backend._ffi.new("unsigned char []", _ED25519_KEY_SIZE)
+        buflen = self._backend._ffi.new("size_t *", _ED25519_KEY_SIZE)
+        res = self._backend._lib.EVP_PKEY_get_raw_private_key(
+            self._evp_pkey, buf, buflen
+        )
+        self._backend.openssl_assert(res == 1)
+        self._backend.openssl_assert(buflen[0] == _ED25519_KEY_SIZE)
+        return self._backend._ffi.buffer(buf, _ED25519_KEY_SIZE)[:]