Clean up server key exchange EC point handling. Encode the point directly

into the CBB memory, rather than mallocing and memcpying, which also makes
makes the code more consistent with the client. Add a missing check for the
first EC_POINT_point2oct() call.

ok beck@

1 files changed, 15 insertions, 27 deletions

diff --git a/lib/libssl/ssl_srvr.c b/lib/libssl/ssl_srvr.c
index d98a76f8f0a..aae72759981 100644
--- a/lib/libssl/ssl_srvr.c
+++ b/lib/libssl/ssl_srvr.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_srvr.c,v 1.11 2017/03/10 16:03:27 jsing Exp $ */
+/* $OpenBSD: ssl_srvr.c,v 1.12 2017/04/14 15:19:39 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1271,8 +1271,7 @@ ssl3_send_server_kex_ecdhe_ecp(SSL *s, int nid, CBB *cbb)
 	unsigned char *data;
 	EC_KEY *ecdh = NULL, *ecdhp;
 	const EC_GROUP *group;
-	unsigned char *encodedPoint = NULL;
-	int encodedlen = 0;
+	int encoded_len = 0;
 	int curve_id = 0;
 	BN_CTX *bn_ctx = NULL;
 	int al;
@@ -1335,28 +1334,17 @@ ssl3_send_server_kex_ecdhe_ecp(SSL *s, int nid, CBB *cbb)
 	 * Encode the public key. First check the size of encoding and
 	 * allocate memory accordingly.
 	 */
-	encodedlen = EC_POINT_point2oct(group, EC_KEY_get0_public_key(ecdh),
+	encoded_len = EC_POINT_point2oct(group, EC_KEY_get0_public_key(ecdh),
 	    POINT_CONVERSION_UNCOMPRESSED, NULL, 0, NULL);
-
-	encodedPoint = malloc(encodedlen);
-
-	bn_ctx = BN_CTX_new();
-	if ((encodedPoint == NULL) || (bn_ctx == NULL)) {
-		SSLerror(s, ERR_R_MALLOC_FAILURE);
+	if (encoded_len == 0) {
+		SSLerror(s, ERR_R_ECDH_LIB);
 		goto err;
 	}
-
-	encodedlen = EC_POINT_point2oct(group, EC_KEY_get0_public_key(ecdh),
-	    POINT_CONVERSION_UNCOMPRESSED, encodedPoint, encodedlen, bn_ctx);
-
-	if (encodedlen == 0) {
-		SSLerror(s, ERR_R_ECDH_LIB);
+	if ((bn_ctx = BN_CTX_new()) == NULL) {
+		SSLerror(s, ERR_R_MALLOC_FAILURE);
 		goto err;
 	}
 
-	BN_CTX_free(bn_ctx);
-	bn_ctx = NULL;
-
 	/*
 	 * Only named curves are supported in ECDH ephemeral key exchanges.
 	 * In this case the ServerKeyExchange message has:
@@ -1370,23 +1358,23 @@ ssl3_send_server_kex_ecdhe_ecp(SSL *s, int nid, CBB *cbb)
 		goto err;
 	if (!CBB_add_u8_length_prefixed(cbb, &ecpoint))
 		goto err;
-	if (!CBB_add_space(&ecpoint, &data, encodedlen))
+	if (!CBB_add_space(&ecpoint, &data, encoded_len))
 		goto err;
-
-	memcpy(data, encodedPoint, encodedlen);
-
-	free(encodedPoint);
-	encodedPoint = NULL;
-
+	if (EC_POINT_point2oct(group, EC_KEY_get0_public_key(ecdh),
+	    POINT_CONVERSION_UNCOMPRESSED, data, encoded_len, bn_ctx) == 0) {
+		SSLerror(s, ERR_R_ECDH_LIB);
+		goto err;
+	}
 	if (!CBB_flush(cbb))
 		goto err;
 
+	BN_CTX_free(bn_ctx);
+
 	return (1);
 	
  f_err:
 	ssl3_send_alert(s, SSL3_AL_FATAL, al);
  err:
-	free(encodedPoint);
 	BN_CTX_free(bn_ctx);
 
 	return (-1);