Add SSL_get_client_ciphers() to return ciphers from ClientHello

On the server side, if you want to know which ciphers the client
offered, you had to use session->ciphers.  But that field is no
longer visible, so we need a method to get at it.
Signed-off-by: NNick Mathewson <nickm@torproject.org>
Signed-off-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NTim Hudson <tjh@openssl.org>

doc/ssl/SSL_get_ciphers.pod

@@ -9,6 +9,7 @@ SSL_get_ciphers, SSL_get_cipher_list - get list of available SSL_CIPHERs
  #include <openssl/ssl.h>
 
  STACK_OF(SSL_CIPHER) *SSL_get_ciphers(const SSL *ssl);
+ STACK_OF(SSL_CIPHER) *SSL_get_client_ciphers(const SSL *ssl);
  const char *SSL_get_cipher_list(const SSL *ssl, int priority);
 
 =head1 DESCRIPTION
@@ -17,6 +18,10 @@ SSL_get_ciphers() returns the stack of available SSL_CIPHERs for B<ssl>,
 sorted by preference. If B<ssl> is NULL or no ciphers are available, NULL
 is returned.
 
+SSL_get_client_ciphers() returns the stack of available SSL_CIPHERS matching the
+list sent by the client for B<ssl>. If B<ssl> is NULL, no ciphers are
+available, or B<ssl> is not operating in server mode, NULL is returned.
+
 SSL_get_cipher_list() returns a pointer to the name of the SSL_CIPHER
 listed for B<ssl> with B<priority>. If B<ssl> is NULL, no ciphers are
 available, or there are less ciphers than B<priority> available, NULL

include/openssl/ssl.h

@@ -1583,6 +1583,7 @@ __owur const SSL_METHOD *DTLS_server_method(void); /* DTLS 1.0 and 1.2 */
 __owur const SSL_METHOD *DTLS_client_method(void); /* DTLS 1.0 and 1.2 */
 
 __owur STACK_OF(SSL_CIPHER) *SSL_get_ciphers(const SSL *s);
+__owur STACK_OF(SSL_CIPHER) *SSL_get_client_ciphers(const SSL *s);
 __owur STACK_OF(SSL_CIPHER) *SSL_get1_supported_ciphers(SSL *s);
 
 __owur int SSL_do_handshake(SSL *s);

ssl/ssl_lib.c

@@ -1258,6 +1258,13 @@ STACK_OF(SSL_CIPHER) *SSL_get_ciphers(const SSL *s)
     return (NULL);
 }
 
+STACK_OF(SSL_CIPHER) *SSL_get_client_ciphers(const SSL *s)
+{
+    if ((s == NULL) || (s->session == NULL) || !s->server)
+        return NULL;
+    return s->session->ciphers;
+}
+
 STACK_OF(SSL_CIPHER) *SSL_get1_supported_ciphers(SSL *s)
 {
     STACK_OF(SSL_CIPHER) *sk = NULL, *ciphers;