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

1 files changed, 59 insertions, 1 deletions

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"))
 
@@ -303,6 +332,11 @@ void buf_put_pub_key(buffer* buf, sign_key *key, enum signkey_type type) {
 		}
 	}
 #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");
 	}
@@ -342,6 +376,13 @@ void buf_put_priv_key(buffer* buf, sign_key *key, enum signkey_type type) {
 		}
 	}
 #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");
 }
 
@@ -380,6 +421,10 @@ void sign_key_free(sign_key *key) {
 	}
 #endif
 #endif
+#if DROPBEAR_ED25519
+	ed25519_key_free(key->ed25519key);
+	key->ed25519key = NULL;
+#endif
 
 	m_free(key->filename);
 
@@ -504,6 +549,11 @@ void buf_put_sign(buffer* buf, sign_key *key, enum signkey_type type,
 		}
 	}
 #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;