Don't fail the connection in SSLv3 if server selects ECDHE

ECDHE is not properly defined for SSLv3. Commit fe55c4a prevented ECDHE
from being selected in that protocol. However, historically, servers do
still select ECDHE anyway so that commit causes interoperability problems.
Clients that previously worked when talking to an SSLv3 server could now
fail.

This commit introduces an exception which enables a client to continue in
SSLv3 if the server selected ECDHE.

(cherry picked from commit 8af91fd)

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from #3734)

ssl/ssl_lib.c

@@ -1944,7 +1944,7 @@ STACK_OF(SSL_CIPHER) *SSL_get1_supported_ciphers(SSL *s)
     ssl_set_client_disabled(s);
     for (i = 0; i < sk_SSL_CIPHER_num(ciphers); i++) {
         const SSL_CIPHER *c = sk_SSL_CIPHER_value(ciphers, i);
-        if (!ssl_cipher_disabled(s, c, SSL_SECOP_CIPHER_SUPPORTED)) {
+        if (!ssl_cipher_disabled(s, c, SSL_SECOP_CIPHER_SUPPORTED, 0)) {
             if (!sk)
                 sk = sk_SSL_CIPHER_new_null();
             if (!sk)

ssl/ssl_locl.h

@@ -2070,7 +2070,7 @@ __owur size_t tls12_get_psigalgs(SSL *s, int sent, const unsigned char **psigs);
 __owur int tls12_check_peer_sigalg(const EVP_MD **pmd, SSL *s,
                                    const unsigned char *sig, EVP_PKEY *pkey);
 void ssl_set_client_disabled(SSL *s);
-__owur int ssl_cipher_disabled(SSL *s, const SSL_CIPHER *c, int op);
+__owur int ssl_cipher_disabled(SSL *s, const SSL_CIPHER *c, int op, int echde);
 
 __owur int ssl_add_clienthello_use_srtp_ext(SSL *s, unsigned char *p, int *len,
                                             int maxlen);

ssl/statem/statem_clnt.c

@@ -1038,7 +1038,7 @@ MSG_PROCESS_RETURN tls_process_server_hello(SSL *s, PACKET *pkt)
      * If it is a disabled cipher we either didn't send it in client hello,
      * or it's not allowed for the selected protocol. So we return an error.
      */
-    if (ssl_cipher_disabled(s, c, SSL_SECOP_CIPHER_CHECK)) {
+    if (ssl_cipher_disabled(s, c, SSL_SECOP_CIPHER_CHECK, 1)) {
         al = SSL_AD_ILLEGAL_PARAMETER;
         SSLerr(SSL_F_TLS_PROCESS_SERVER_HELLO, SSL_R_WRONG_CIPHER_RETURNED);
         goto f_err;
@@ -2919,7 +2919,7 @@ int ssl_cipher_list_to_bytes(SSL *s, STACK_OF(SSL_CIPHER) *sk, unsigned char *p)
     for (i = 0; i < sk_SSL_CIPHER_num(sk); i++) {
         c = sk_SSL_CIPHER_value(sk, i);
         /* Skip disabled ciphers */
-        if (ssl_cipher_disabled(s, c, SSL_SECOP_CIPHER_SUPPORTED))
+        if (ssl_cipher_disabled(s, c, SSL_SECOP_CIPHER_SUPPORTED, 0))
             continue;
         j = s->method->put_cipher_by_char(c, p);
         p += j;

ssl/t1_lib.c

@@ -863,19 +863,31 @@ void ssl_set_client_disabled(SSL *s)
  * @s: SSL connection that you want to use the cipher on
  * @c: cipher to check
  * @op: Security check that you want to do
+ * @ecdhe: If set to 1 then TLSv1 ECDHE ciphers are also allowed in SSLv3
  *
  * Returns 1 when it's disabled, 0 when enabled.
  */
-int ssl_cipher_disabled(SSL *s, const SSL_CIPHER *c, int op)
+int ssl_cipher_disabled(SSL *s, const SSL_CIPHER *c, int op, int ecdhe)
 {
     if (c->algorithm_mkey & s->s3->tmp.mask_k
         || c->algorithm_auth & s->s3->tmp.mask_a)
         return 1;
     if (s->s3->tmp.max_ver == 0)
         return 1;
-    if (!SSL_IS_DTLS(s) && ((c->min_tls > s->s3->tmp.max_ver)
-                            || (c->max_tls < s->s3->tmp.min_ver)))
-        return 1;
+    if (!SSL_IS_DTLS(s)) {
+        int min_tls = c->min_tls;
+
+        /*
+         * For historical reasons we will allow ECHDE to be selected by a server
+         * in SSLv3 if we are a client
+         */
+        if (min_tls == TLS1_VERSION && ecdhe
+                && (c->algorithm_mkey & (SSL_kECDHE | SSL_kECDHEPSK)) != 0)
+            min_tls = SSL3_VERSION;
+
+        if ((min_tls > s->s3->tmp.max_ver) || (c->max_tls < s->s3->tmp.min_ver))
+            return 1;
+    }
     if (SSL_IS_DTLS(s) && (DTLS_VERSION_GT(c->min_dtls, s->s3->tmp.max_ver)
                            || DTLS_VERSION_LT(c->max_dtls, s->s3->tmp.min_ver)))
         return 1;