Add ssl_set_arc4_support()

Rationale: if people want to disable RC4 but otherwise keep the default suite
list, it was cumbersome. Also, since it uses a global array,
ssl_list_ciphersuite() is not a convenient place. So the SSL modules look like
the best place, even if it means temporarily adding one SSL setting.

ChangeLog

@@ -4,6 +4,10 @@ PolarSSL ChangeLog (Sorted per branch, date)
 Changes
    * Example programs for SSL client and server now disable SSLv3 by default.
 
+Features
+   * Add ssl_set_arc4_support() to make it easier to diable RC4 at runtime
+     while using the default ciphersuite list.
+
 = PolarSSL 1.3.9 released 2014-10-20
 Security
    * Lowest common hash was selected from signature_algorithms extension in

include/polarssl/ssl.h

@@ -238,6 +238,9 @@
 #define SSL_SESSION_TICKETS_DISABLED     0
 #define SSL_SESSION_TICKETS_ENABLED      1
 
+#define SSL_ARC4_ENABLED                0
+#define SSL_ARC4_DISABLED               1
+
 /**
  * \name SECTION: Module settings
  *
@@ -697,6 +700,8 @@ struct _ssl_context
     int min_major_ver;          /*!< min. major version used          */
     int min_minor_ver;          /*!< min. minor version used          */
 
+    char arc4_disabled;         /*!< flag for disabling RC4           */
+
     /*
      * Callbacks (RNG, debug, I/O, verification)
      */
@@ -1385,6 +1390,21 @@ void ssl_set_max_version( ssl_context *ssl, int major, int minor );
  */
 void ssl_set_min_version( ssl_context *ssl, int major, int minor );
 
+/**
+ * \brief          Disable or enable support for RC4
+ *                 (Default: SSL_ARC4_ENABLED)
+ *
+ * \note           Though the default is RC4 for compatibility reasons in the
+ *                 1.3 branch, the recommended value is SSL_ARC4_DISABLED.
+ *
+ * \note           This function will likely be removed in future versions as
+ *                 RC4 will then be disabled by default at compile time.
+ *
+ * \param ssl      SSL context
+ * \param arc4     SSL_ARC4_ENABLED or SSL_ARC4_DISABLED
+ */
+void ssl_set_arc4_support( ssl_context *ssl, char arc4 );
+
 #if defined(POLARSSL_SSL_MAX_FRAGMENT_LENGTH)
 /**
  * \brief          Set the maximum fragment length to emit and/or negotiate

library/ssl_cli.c

@@ -588,6 +588,10 @@ static int ssl_write_client_hello( ssl_context *ssl )
             ciphersuite_info->max_minor_ver < ssl->min_minor_ver )
             continue;
 
+        if( ssl->arc4_disabled == SSL_ARC4_DISABLED &&
+            ciphersuite_info->cipher == POLARSSL_CIPHER_ARC4_128 )
+            continue;
+
         SSL_DEBUG_MSG( 3, ( "client hello, add ciphersuite: %2d",
                        ciphersuites[i] ) );
 
@@ -879,6 +883,7 @@ static int ssl_parse_server_hello( ssl_context *ssl )
     unsigned char *buf, *ext;
     int renegotiation_info_seen = 0;
     int handshake_failure = 0;
+    const ssl_ciphersuite_t *suite_info;
 #if defined(POLARSSL_DEBUG_C)
     uint32_t t;
 #endif
@@ -1059,6 +1064,16 @@ static int ssl_parse_server_hello( ssl_context *ssl )
     SSL_DEBUG_MSG( 3, ( "server hello, chosen ciphersuite: %d", i ) );
     SSL_DEBUG_MSG( 3, ( "server hello, compress alg.: %d", buf[41 + n] ) );
 
+    suite_info = ssl_ciphersuite_from_id( ssl->session_negotiate->ciphersuite );
+    if( suite_info == NULL ||
+        ( ssl->arc4_disabled &&
+          suite_info->cipher == POLARSSL_CIPHER_ARC4_128 ) )
+    {
+        SSL_DEBUG_MSG( 1, ( "bad server hello message" ) );
+        return( POLARSSL_ERR_SSL_BAD_HS_SERVER_HELLO );
+    }
+
+
     i = 0;
     while( 1 )
     {

library/ssl_srv.c

@@ -847,6 +847,10 @@ static int ssl_ciphersuite_match( ssl_context *ssl, int suite_id,
         suite_info->max_minor_ver < ssl->minor_ver )
         return( 0 );
 
+    if( ssl->arc4_disabled == SSL_ARC4_DISABLED &&
+            suite_info->cipher == POLARSSL_CIPHER_ARC4_128 )
+        return( 0 );
+
 #if defined(POLARSSL_ECDH_C) || defined(POLARSSL_ECDSA_C)
     if( ssl_ciphersuite_uses_ec( suite_info ) &&
         ( ssl->handshake->curves == NULL ||

library/ssl_tls.c

@@ -3977,6 +3977,11 @@ void ssl_set_min_version( ssl_context *ssl, int major, int minor )
     }
 }
 
+void ssl_set_arc4_support( ssl_context *ssl, char arc4 )
+{
+    ssl->arc4_disabled = arc4;
+}
+
 #if defined(POLARSSL_SSL_MAX_FRAGMENT_LENGTH)
 int ssl_set_max_frag_len( ssl_context *ssl, unsigned char mfl_code )
 {

programs/ssl/ssl_client2.c

@@ -88,6 +88,7 @@ int main( int argc, char *argv[] )
 #define DFL_EXCHANGES           1
 #define DFL_MIN_VERSION         SSL_MINOR_VERSION_1
 #define DFL_MAX_VERSION         -1
+#define DFL_ARC4                SSL_ARC4_DISABLED
 #define DFL_AUTH_MODE           SSL_VERIFY_REQUIRED
 #define DFL_MFL_CODE            SSL_MAX_FRAG_LEN_NONE
 #define DFL_TRUNC_HMAC          0
@@ -125,6 +126,7 @@ struct options
     int exchanges;              /* number of data exchanges                 */
     int min_version;            /* minimum protocol version accepted        */
     int max_version;            /* maximum protocol version accepted        */
+    int arc4;                   /* flag for arc4 suites support             */
     int auth_mode;              /* verify mode for connection               */
     unsigned char mfl_code;     /* code for maximum fragment length         */
     int trunc_hmac;             /* negotiate truncated hmac or not          */
@@ -316,6 +318,7 @@ static int my_verify( void *data, x509_crt *crt, int depth, int *flags )
     "\n"                                                    \
     "    min_version=%%s      default: \"\" (ssl3)\n"       \
     "    max_version=%%s      default: \"\" (tls1_2)\n"     \
+    "    arc4=%%d             default: 0 (disabled)\n"      \
     "    force_version=%%s    default: \"\" (none)\n"       \
     "                        options: ssl3, tls1, tls1_1, tls1_2\n" \
     "    auth_mode=%%s        default: \"required\"\n"      \
@@ -406,6 +409,7 @@ int main( int argc, char *argv[] )
     opt.exchanges           = DFL_EXCHANGES;
     opt.min_version         = DFL_MIN_VERSION;
     opt.max_version         = DFL_MAX_VERSION;
+    opt.arc4                = DFL_ARC4;
     opt.auth_mode           = DFL_AUTH_MODE;
     opt.mfl_code            = DFL_MFL_CODE;
     opt.trunc_hmac          = DFL_TRUNC_HMAC;
@@ -545,6 +549,15 @@ int main( int argc, char *argv[] )
             else
                 goto usage;
         }
+        else if( strcmp( p, "arc4" ) == 0 )
+        {
+            switch( atoi( q ) )
+            {
+                case 0:     opt.arc4 = SSL_ARC4_DISABLED;   break;
+                case 1:     opt.arc4 = SSL_ARC4_ENABLED;    break;
+                default:    goto usage;
+            }
+        }
         else if( strcmp( p, "force_version" ) == 0 )
         {
             if( strcmp( q, "ssl3" ) == 0 )
@@ -907,8 +920,11 @@ int main( int argc, char *argv[] )
     }
 #endif
 
+    /* RC4 setting is redundant if we use only one ciphersuite */
     if( opt.force_ciphersuite[0] != DFL_FORCE_CIPHER )
         ssl_set_ciphersuites( &ssl, opt.force_ciphersuite );
+    else
+        ssl_set_arc4_support( &ssl, opt.arc4 );
 
     ssl_set_renegotiation( &ssl, opt.renegotiation );
     ssl_legacy_renegotiation( &ssl, opt.allow_legacy );

programs/ssl/ssl_server2.c

@@ -107,6 +107,7 @@ int main( int argc, char *argv[] )
 #define DFL_EXCHANGES           1
 #define DFL_MIN_VERSION         SSL_MINOR_VERSION_1
 #define DFL_MAX_VERSION         -1
+#define DFL_ARC4                SSL_ARC4_DISABLED
 #define DFL_AUTH_MODE           SSL_VERIFY_OPTIONAL
 #define DFL_MFL_CODE            SSL_MAX_FRAG_LEN_NONE
 #define DFL_TICKETS             SSL_SESSION_TICKETS_ENABLED
@@ -167,6 +168,7 @@ struct options
     int exchanges;              /* number of data exchanges                 */
     int min_version;            /* minimum protocol version accepted        */
     int max_version;            /* maximum protocol version accepted        */
+    int arc4;                   /* flag for arc4 suites support             */
     int auth_mode;              /* verify mode for connection               */
     unsigned char mfl_code;     /* code for maximum fragment length         */
     int tickets;                /* enable / disable session tickets         */
@@ -327,6 +329,7 @@ static int my_send( void *ctx, const unsigned char *buf, size_t len )
     "\n"                                                    \
     "    min_version=%%s      default: \"ssl3\"\n"          \
     "    max_version=%%s      default: \"tls1_2\"\n"        \
+    "    arc4=%%d             default: 0 (disabled)\n"      \
     "    force_version=%%s    default: \"\" (none)\n"       \
     "                        options: ssl3, tls1, tls1_1, tls1_2\n"     \
     "\n"                                                                \
@@ -704,6 +707,7 @@ int main( int argc, char *argv[] )
     opt.exchanges           = DFL_EXCHANGES;
     opt.min_version         = DFL_MIN_VERSION;
     opt.max_version         = DFL_MAX_VERSION;
+    opt.arc4                = DFL_ARC4;
     opt.auth_mode           = DFL_AUTH_MODE;
     opt.mfl_code            = DFL_MFL_CODE;
     opt.tickets             = DFL_TICKETS;
@@ -827,6 +831,15 @@ int main( int argc, char *argv[] )
             else
                 goto usage;
         }
+        else if( strcmp( p, "arc4" ) == 0 )
+        {
+            switch( atoi( q ) )
+            {
+                case 0:     opt.arc4 = SSL_ARC4_DISABLED;   break;
+                case 1:     opt.arc4 = SSL_ARC4_ENABLED;    break;
+                default:    goto usage;
+            }
+        }
         else if( strcmp( p, "force_version" ) == 0 )
         {
             if( strcmp( q, "ssl3" ) == 0 )
@@ -1293,6 +1306,8 @@ int main( int argc, char *argv[] )
 
     if( opt.force_ciphersuite[0] != DFL_FORCE_CIPHER )
         ssl_set_ciphersuites( &ssl, opt.force_ciphersuite );
+    else
+        ssl_set_arc4_support( &ssl, opt.arc4 );
 
     if( opt.version_suites != NULL )
     {

tests/compat.sh

@@ -667,7 +667,7 @@ setup_arguments()
             exit 1;
     esac
 
-    P_SERVER_ARGS="server_port=$PORT server_addr=0.0.0.0 force_version=$MODE"
+    P_SERVER_ARGS="server_port=$PORT server_addr=0.0.0.0 force_version=$MODE arc4=1"
     O_SERVER_ARGS="-accept $PORT -www -cipher NULL,ALL -$MODE"
     G_SERVER_ARGS="-p $PORT --http"
     G_SERVER_PRIO="EXPORT:+NULL:+MD5:+PSK:+DHE-PSK:+ECDHE-PSK:+RSA-PSK:-VERS-TLS-ALL:$G_PRIO_MODE"

tests/ssl-opt.sh

@@ -393,6 +393,26 @@ run_test    "Default" \
             -S "error" \
             -C "error"
 
+# Tests for rc4 option
+
+run_test    "RC4: server disabled, client enabled" \
+            "$P_SRV" \
+            "$P_CLI force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA" \
+            1 \
+            -s "SSL - The server has no ciphersuites in common"
+
+run_test    "RC4: server enabled, client disabled" \
+            "$P_SRV force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA" \
+            "$P_CLI" \
+            1 \
+            -s "SSL - The server has no ciphersuites in common"
+
+run_test    "RC4: both enabled" \
+            "$P_SRV arc4=1" \
+            "$P_CLI force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA" \
+            0 \
+            -S "SSL - The server has no ciphersuites in common"
+
 # Test for SSLv2 ClientHello
 
 requires_openssl_with_sslv2
@@ -1575,8 +1595,8 @@ run_test    "Per-version suites: SSL3" \
             -c "Ciphersuite is TLS-RSA-WITH-3DES-EDE-CBC-SHA"
 
 run_test    "Per-version suites: TLS 1.0" \
-            "$P_SRV version_suites=TLS-RSA-WITH-3DES-EDE-CBC-SHA,TLS-RSA-WITH-RC4-128-SHA,TLS-RSA-WITH-AES-128-CBC-SHA,TLS-RSA-WITH-AES-128-GCM-SHA256" \
+            "$P_SRV arc4=1 version_suites=TLS-RSA-WITH-3DES-EDE-CBC-SHA,TLS-RSA-WITH-RC4-128-SHA,TLS-RSA-WITH-AES-128-CBC-SHA,TLS-RSA-WITH-AES-128-GCM-SHA256" \
-            "$P_CLI force_version=tls1" \
+            "$P_CLI force_version=tls1 arc4=1" \
             0 \
             -c "Ciphersuite is TLS-RSA-WITH-RC4-128-SHA"
 
@@ -1616,7 +1636,7 @@ run_test    "Small packet SSLv3 BlockCipher" \
             -s "Read from client: 1 bytes read"
 
 run_test    "Small packet SSLv3 StreamCipher" \
-            "$P_SRV min_version=ssl3" \
+            "$P_SRV min_version=ssl3 arc4=1" \
             "$P_CLI request_size=1 force_version=ssl3 \
              force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA" \
             0 \
@@ -1638,7 +1658,7 @@ run_test    "Small packet TLS 1.0 BlockCipher truncated MAC" \
             -s "Read from client: 1 bytes read"
 
 run_test    "Small packet TLS 1.0 StreamCipher truncated MAC" \
-            "$P_SRV" \
+            "$P_SRV arc4=1" \
             "$P_CLI request_size=1 force_version=tls1 \
              force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA \
              trunc_hmac=1" \
@@ -1653,7 +1673,7 @@ run_test    "Small packet TLS 1.1 BlockCipher" \
             -s "Read from client: 1 bytes read"
 
 run_test    "Small packet TLS 1.1 StreamCipher" \
-            "$P_SRV" \
+            "$P_SRV arc4=1" \
             "$P_CLI request_size=1 force_version=tls1_1 \
              force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA" \
             0 \
@@ -1668,7 +1688,7 @@ run_test    "Small packet TLS 1.1 BlockCipher truncated MAC" \
             -s "Read from client: 1 bytes read"
 
 run_test    "Small packet TLS 1.1 StreamCipher truncated MAC" \
-            "$P_SRV" \
+            "$P_SRV arc4=1" \
             "$P_CLI request_size=1 force_version=tls1_1 \
              force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA \
              trunc_hmac=1" \
@@ -1697,14 +1717,14 @@ run_test    "Small packet TLS 1.2 BlockCipher truncated MAC" \
             -s "Read from client: 1 bytes read"
 
 run_test    "Small packet TLS 1.2 StreamCipher" \
-            "$P_SRV" \
+            "$P_SRV arc4=1" \
             "$P_CLI request_size=1 force_version=tls1_2 \
              force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA" \
             0 \
             -s "Read from client: 1 bytes read"
 
 run_test    "Small packet TLS 1.2 StreamCipher truncated MAC" \
-            "$P_SRV" \
+            "$P_SRV arc4=1" \
             "$P_CLI request_size=1 force_version=tls1_2 \
              force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA \
              trunc_hmac=1" \
@@ -1735,7 +1755,7 @@ run_test    "Large packet SSLv3 BlockCipher" \
             -s "Read from client: 16384 bytes read"
 
 run_test    "Large packet SSLv3 StreamCipher" \
-            "$P_SRV min_version=ssl3" \
+            "$P_SRV min_version=ssl3 arc4=1" \
             "$P_CLI request_size=16384 force_version=ssl3 \
              force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA" \
             0 \
@@ -1757,7 +1777,7 @@ run_test    "Large packet TLS 1.0 BlockCipher truncated MAC" \
             -s "Read from client: 16384 bytes read"
 
 run_test    "Large packet TLS 1.0 StreamCipher truncated MAC" \
-            "$P_SRV" \
+            "$P_SRV arc4=1" \
             "$P_CLI request_size=16384 force_version=tls1 \
              force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA \
              trunc_hmac=1" \
@@ -1772,7 +1792,7 @@ run_test    "Large packet TLS 1.1 BlockCipher" \
             -s "Read from client: 16384 bytes read"
 
 run_test    "Large packet TLS 1.1 StreamCipher" \
-            "$P_SRV" \
+            "$P_SRV arc4=1" \
             "$P_CLI request_size=16384 force_version=tls1_1 \
              force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA" \
             0 \
@@ -1787,7 +1807,7 @@ run_test    "Large packet TLS 1.1 BlockCipher truncated MAC" \
             -s "Read from client: 16384 bytes read"
 
 run_test    "Large packet TLS 1.1 StreamCipher truncated MAC" \
-            "$P_SRV" \
+            "$P_SRV arc4=1" \
             "$P_CLI request_size=16384 force_version=tls1_1 \
              force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA \
              trunc_hmac=1" \
@@ -1816,14 +1836,14 @@ run_test    "Large packet TLS 1.2 BlockCipher truncated MAC" \
             -s "Read from client: 16384 bytes read"
 
 run_test    "Large packet TLS 1.2 StreamCipher" \
-            "$P_SRV" \
+            "$P_SRV arc4=1" \
             "$P_CLI request_size=16384 force_version=tls1_2 \
              force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA" \
             0 \
             -s "Read from client: 16384 bytes read"
 
 run_test    "Large packet TLS 1.2 StreamCipher truncated MAC" \
-            "$P_SRV" \
+            "$P_SRV arc4=1" \
             "$P_CLI request_size=16384 force_version=tls1_2 \
              force_ciphersuite=TLS-RSA-WITH-RC4-128-SHA \
              trunc_hmac=1" \