Add support for automatic ephemeral EC keys.

This allows an SSL server to enable ECDHE ciphers with a single setting,
which results in an EC key being generated using the first preference
shared curve.

Based on OpenSSL with inspiration from boringssl.

ok miod@

1 files changed, 11 insertions, 3 deletions

diff --git a/src/lib/libssl/s3_srvr.c b/src/lib/libssl/s3_srvr.c
index cba875a3e6..c4a8442a3e 100644
--- a/src/lib/libssl/s3_srvr.c
+++ b/src/lib/libssl/s3_srvr.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: s3_srvr.c,v 1.85 2014/09/27 11:03:43 jsing Exp $ */
+/* $OpenBSD: s3_srvr.c,v 1.86 2014/10/03 13:58:18 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1465,9 +1465,15 @@ ssl3_send_server_key_exchange(SSL *s)
                         const EC_GROUP *group;
 
                         ecdhp = cert->ecdh_tmp;
-                        if (ecdhp == NULL && s->cert->ecdh_tmp_cb != NULL)
+                        if (s->cert->ecdh_tmp_auto != 0) {
+                                int nid = tls1_get_shared_curve(s);
+                                if (nid != NID_undef)
+                                        ecdhp = EC_KEY_new_by_curve_name(nid);
+                        } else if (ecdhp == NULL &&
+                            s->cert->ecdh_tmp_cb != NULL) {
                                 ecdhp = s->cert->ecdh_tmp_cb(s, 0,
                                     SSL_C_PKEYLENGTH(s->s3->tmp.new_cipher));
+                        }
                         if (ecdhp == NULL) {
                                 al = SSL_AD_HANDSHAKE_FAILURE;
                                 SSLerr(SSL_F_SSL3_SEND_SERVER_KEY_EXCHANGE,
@@ -1482,7 +1488,9 @@ ssl3_send_server_key_exchange(SSL *s)
                         }
 
                         /* Duplicate the ECDH structure. */
-                        if ((ecdh = EC_KEY_dup(ecdhp)) == NULL) {
+                        if (s->cert->ecdh_tmp_auto != 0) {
+                                ecdh = ecdhp;
+                        } else if ((ecdh = EC_KEY_dup(ecdhp)) == NULL) {
                                 SSLerr(SSL_F_SSL3_SEND_SERVER_KEY_EXCHANGE,
                                     ERR_R_ECDH_LIB);
                                 goto err;