From 59b81d73b4aae1a2f4414cf2a3457a788fb138df Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Manuel=20P=C3=A9gouri=C3=A9-Gonnard?= <mpg@elzevir.fr>
Date: Sat, 30 Nov 2013 17:46:04 +0100
Subject: [PATCH] Refactor ciphersuite selection for version > 2

---
 library/ssl_srv.c | 101 +++++++++++++++++++++++++++-------------------
 1 file changed, 59 insertions(+), 42 deletions(-)

diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 530c86653..ffd73e2fc 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -974,6 +974,59 @@ static int ssl_pick_cert( ssl_context *ssl,
 }
 #endif /* POLARSSL_X509_CRT_PARSE_C */
 
+/*
+ * Check if a given ciphersuite is suitable for use with our config/keys/etc
+ * Sets ciphersuite_info only if the suite matches.
+ */
+static int ssl_ciphersuite_match( ssl_context *ssl, int suite_id,
+                                  const ssl_ciphersuite_t **ciphersuite_info )
+{
+    const ssl_ciphersuite_t *suite_info;
+
+    suite_info = ssl_ciphersuite_from_id( suite_id );
+    if( suite_info == NULL )
+    {
+        SSL_DEBUG_MSG( 1, ( "ciphersuite info for %04x not found", suite_id ) );
+        return( POLARSSL_ERR_SSL_BAD_INPUT_DATA );
+    }
+
+    if( suite_info->min_minor_ver > ssl->minor_ver ||
+        suite_info->max_minor_ver < ssl->minor_ver )
+        return( 0 );
+
+#if defined(POLARSSL_ECDH_C) || defined(POLARSSL_ECDSA_C)
+    if( ssl_ciphersuite_uses_ec( suite_info ) &&
+        ( ssl->handshake->curves == NULL ||
+          ssl->handshake->curves[0] == NULL ) )
+        return( 0 );
+#endif
+
+#if defined(POLARSSL_KEY_EXCHANGE__SOME__PSK_ENABLED)
+    /* If the ciphersuite requires a pre-shared key and we don't
+     * have one, skip it now rather than failing later */
+    if( ssl_ciphersuite_uses_psk( suite_info ) &&
+        ssl->f_psk == NULL &&
+        ( ssl->psk == NULL || ssl->psk_identity == NULL ||
+          ssl->psk_identity_len == 0 || ssl->psk_len == 0 ) )
+        return( 0 );
+#endif
+
+#if defined(POLARSSL_X509_CRT_PARSE_C)
+    /*
+     * Final check: if ciphersuite requires us to have a
+     * certificate/key of a particular type:
+     * - select the appropriate certificate if we have one, or
+     * - try the next ciphersuite if we don't
+     * This must be done last since we modify the key_cert list.
+     */
+    if( ssl_pick_cert( ssl, suite_info ) != 0 )
+        return( 0 );
+#endif
+
+    *ciphersuite_info = suite_info;
+    return( 0 );
+}
+
 static int ssl_parse_client_hello( ssl_context *ssl )
 {
     int ret;
@@ -1372,6 +1425,7 @@ static int ssl_parse_client_hello( ssl_context *ssl )
      * and certificate from the SNI callback triggered by the SNI extension.)
      */
     ciphersuites = ssl->ciphersuite_list[ssl->minor_ver];
+    ciphersuite_info = NULL;
     for( i = 0; ciphersuites[i] != 0; i++ )
     {
         for( j = 0, p = buf + 41 + sess_len; j < ciph_len;
@@ -1380,49 +1434,12 @@ static int ssl_parse_client_hello( ssl_context *ssl )
             if( p[0] == ( ( ciphersuites[i] >> 8 ) & 0xFF ) &&
                 p[1] == ( ( ciphersuites[i]      ) & 0xFF ) )
             {
-                ciphersuite_info = ssl_ciphersuite_from_id( ciphersuites[i] );
+                if( ( ret = ssl_ciphersuite_match( ssl, ciphersuites[i],
+                                                   &ciphersuite_info ) ) != 0 )
+                    return( ret );
 
-                if( ciphersuite_info == NULL )
-                {
-                    SSL_DEBUG_MSG( 1, ( "ciphersuite info for %04x not found",
-                                   ciphersuites[i] ) );
-                    return( POLARSSL_ERR_SSL_BAD_INPUT_DATA );
-                }
-
-                if( ciphersuite_info->min_minor_ver > ssl->minor_ver ||
-                    ciphersuite_info->max_minor_ver < ssl->minor_ver )
-                    continue;
-
-#if defined(POLARSSL_ECDH_C) || defined(POLARSSL_ECDSA_C)
-                if( ssl_ciphersuite_uses_ec( ciphersuite_info ) &&
-                    ( ssl->handshake->curves == NULL ||
-                      ssl->handshake->curves[0] == NULL ) )
-                    continue;
-#endif
-
-#if defined(POLARSSL_KEY_EXCHANGE__SOME__PSK_ENABLED)
-                /* If the ciphersuite requires a pre-shared key and we don't
-                 * have one, skip it now rather than failing later */
-                if( ssl_ciphersuite_uses_psk( ciphersuite_info ) &&
-                    ssl->f_psk == NULL &&
-                    ( ssl->psk == NULL || ssl->psk_identity == NULL ||
-                      ssl->psk_identity_len == 0 || ssl->psk_len == 0 ) )
-                    continue;
-#endif
-
-#if defined(POLARSSL_X509_CRT_PARSE_C)
-                /*
-                 * Final check: if ciphersuite requires us to have a
-                 * certificate/key of a particular type:
-                 * - select the appropriate certificate if we have one, or
-                 * - try the next ciphersuite if we don't
-                 * This must be done last since we modify the key_cert list.
-                 */
-                if( ssl_pick_cert( ssl, ciphersuite_info ) != 0 )
-                    continue;
-#endif
-
-                goto have_ciphersuite;
+                if( ciphersuite_info != NULL )
+                    goto have_ciphersuite;
             }
         }
     }