From 1b8db6c27f2f3909b55fc2902d2fd0431b066058 Mon Sep 17 00:00:00 2001

From: Dan Winship <danw@gnome.org>

Date: Sun, 26 Oct 2014 12:25:15 -0400

Subject: [PATCH 1/2] gnutls: loosen the semantics of "use-ssl3"

If SSL 3.0 is disabled, then make "use-ssl3" mean "use the lowest

available TLS version" instead, so that, eg, TLS 1.2 -> TLS 1.0

fallback is still possible.

https://bugzilla.gnome.org/show_bug.cgi?id=738633

---

 tls/gnutls/gtlsconnection-gnutls.c | 55 +++++++++++++++++-------

 tls/tests/connection.c             | 88 ++++++++++++++++++++++++++++++++++++++

 2 files changed, 127 insertions(+), 16 deletions(-)

diff --git a/tls/gnutls/gtlsconnection-gnutls.c b/tls/gnutls/gtlsconnection-gnutls.c

index 7e63412..444ca36 100644

--- a/tls/gnutls/gtlsconnection-gnutls.c

+++ b/tls/gnutls/gtlsconnection-gnutls.c

@@ -194,15 +194,16 @@ g_tls_connection_gnutls_init (GTlsConnectionGnutls *gnutls)

   g_mutex_init (&gnutls->priv->op_mutex);

 }

-/* First field is "ssl3 only", second is "allow unsafe rehandshaking" */

+/* First field is "fallback", second is "allow unsafe rehandshaking" */

 static gnutls_priority_t priorities[2][2];

 static void

 g_tls_connection_gnutls_init_priorities (void)

 {

   const gchar *base_priority;

-  gchar *ssl3_priority, *unsafe_rehandshake_priority, *ssl3_unsafe_rehandshake_priority;

-  int ret;

+  gchar *fallback_priority, *unsafe_rehandshake_priority, *fallback_unsafe_rehandshake_priority;

+  const guint *protos;

+  int ret, i, nprotos, fallback_proto;

   base_priority = g_getenv ("G_TLS_GNUTLS_PRIORITY");

   if (!base_priority)

@@ -215,31 +216,53 @@ g_tls_connection_gnutls_init_priorities (void)

       gnutls_priority_init (&priorities[FALSE][FALSE], base_priority, NULL);

     }

-  ssl3_priority = g_strdup_printf ("%s:!VERS-TLS1.2:!VERS-TLS1.1:!VERS-TLS1.0", base_priority);

   unsafe_rehandshake_priority = g_strdup_printf ("%s:%%UNSAFE_RENEGOTIATION", base_priority);

-  ssl3_unsafe_rehandshake_priority = g_strdup_printf ("%s:!VERS-TLS1.2:!VERS-TLS1.1:!VERS-TLS1.0:%%UNSAFE_RENEGOTIATION", base_priority);

-

-  gnutls_priority_init (&priorities[TRUE][FALSE], ssl3_priority, NULL);

-  gnutls_priority_init (&priorities[FALSE][TRUE], unsafe_rehandshake_priority, NULL);

-  gnutls_priority_init (&priorities[TRUE][TRUE], ssl3_unsafe_rehandshake_priority, NULL);

-

-  g_free (ssl3_priority);

+  ret = gnutls_priority_init (&priorities[FALSE][TRUE], unsafe_rehandshake_priority, NULL);

+  g_warn_if_fail (ret == 0);

   g_free (unsafe_rehandshake_priority);

-  g_free (ssl3_unsafe_rehandshake_priority);

+

+  /* Figure out the lowest SSl/TLS version supported by base_priority */

+  nprotos = gnutls_priority_protocol_list (priorities[FALSE][FALSE], &protos);

+  fallback_proto = G_MAXUINT;

+  for (i = 0; i < nprotos; i++)

+    {

+      if (protos[i] < fallback_proto)

+	fallback_proto = protos[i];

+    }

+  if (fallback_proto == G_MAXUINT)

+    {

+      g_warning ("All GNUTLS protocol versions disabled?");

+      fallback_priority = g_strdup (base_priority);

+    }

+  else

+    {

+      fallback_priority = g_strdup_printf ("%s:!VERS-TLS-ALL:+VERS-%s",

+					   base_priority,

+					   gnutls_protocol_get_name (fallback_proto));

+    }

+  fallback_unsafe_rehandshake_priority = g_strdup_printf ("%s:%%UNSAFE_RENEGOTIATION",

+							  fallback_priority);

+

+  ret = gnutls_priority_init (&priorities[TRUE][FALSE], fallback_priority, NULL);

+  g_warn_if_fail (ret == 0);

+  ret = gnutls_priority_init (&priorities[TRUE][TRUE], fallback_unsafe_rehandshake_priority, NULL);

+  g_warn_if_fail (ret == 0);

+  g_free (fallback_priority);

+  g_free (fallback_unsafe_rehandshake_priority);

 }

 static void

 g_tls_connection_gnutls_set_handshake_priority (GTlsConnectionGnutls *gnutls)

 {

-  gboolean use_ssl3, unsafe_rehandshake;

+  gboolean fallback, unsafe_rehandshake;

   if (G_IS_TLS_CLIENT_CONNECTION (gnutls))

-    use_ssl3 = g_tls_client_connection_get_use_ssl3 (G_TLS_CLIENT_CONNECTION (gnutls));

+    fallback = g_tls_client_connection_get_use_ssl3 (G_TLS_CLIENT_CONNECTION (gnutls));

   else

-    use_ssl3 = FALSE;

+    fallback = FALSE;

   unsafe_rehandshake = (gnutls->priv->rehandshake_mode == G_TLS_REHANDSHAKE_UNSAFELY);

   gnutls_priority_set (gnutls->priv->session,

-		       priorities[use_ssl3][unsafe_rehandshake]);

+		       priorities[fallback][unsafe_rehandshake]);

 }

 static gboolean

diff --git a/tls/tests/connection.c b/tls/tests/connection.c

index 0df8bb1..0e7b706 100644

--- a/tls/tests/connection.c

+++ b/tls/tests/connection.c

@@ -1377,11 +1377,90 @@ test_async_implicit_handshake (TestConnection *test, gconstpointer   data)

   test->client_connection = NULL;

 }

+static void

+quit_on_handshake_complete (GObject      *object,

+			    GAsyncResult *result,

+			    gpointer      user_data)

+{

+  TestConnection *test = user_data;

+  GError *error = NULL;

+

+  g_tls_connection_handshake_finish (G_TLS_CONNECTION (object), result, &error);

+  g_assert_no_error (error);

+

+  g_main_loop_quit (test->loop);

+  return;

+}

+

+#define PRIORITY_SSL_FALLBACK "NORMAL:+VERS-SSL3.0"

+#define PRIORITY_TLS_FALLBACK "NORMAL:+VERS-TLS-ALL:-VERS-SSL3.0"

+

+static void

+test_fallback (gconstpointer data)

+{

+  const char *priority_string = (const char *) data;

+  char *test_name;

+

+  test_name = g_strdup_printf ("/tls/connection/fallback/subprocess/%s", priority_string);

+  g_test_trap_subprocess (test_name, 0, 0);

+  g_test_trap_assert_passed ();

+  g_free (test_name);

+}

+

+static void

+test_fallback_subprocess (TestConnection *test,

+			  gconstpointer   data)

+{

+  GIOStream *connection;

+  GTlsConnection *tlsconn;

+  GError *error = NULL;

+

+  connection = start_echo_server_and_connect_to_it (test);

+  test->client_connection = g_tls_client_connection_new (connection, NULL, &error);

+  g_assert_no_error (error);

+  tlsconn = G_TLS_CONNECTION (test->client_connection);

+  g_object_unref (connection);

+

+  g_tls_client_connection_set_validation_flags (G_TLS_CLIENT_CONNECTION (test->client_connection),

+                                                0);

+  g_tls_client_connection_set_use_ssl3 (G_TLS_CLIENT_CONNECTION (test->client_connection),

+					TRUE);

+  g_tls_connection_handshake_async (tlsconn, G_PRIORITY_DEFAULT, NULL,

+				    quit_on_handshake_complete, test);

+  g_main_loop_run (test->loop);

+

+  /* In 2.42 we don't have the API to test that the correct version was negotiated,

+   * so we merely test that the connection succeeded at all.

+   */

+

+  g_io_stream_close (test->client_connection, NULL, &error);

+  g_assert_no_error (error);

+}

+

 int

 main (int   argc,

       char *argv[])

 {

   int ret;

+  int i;

+

+  /* Check if this is a subprocess, and set G_TLS_GNUTLS_PRIORITY

+   * appropriately if so.

+   */

+  for (i = 1; i < argc - 1; i++)

+    {

+      if (!strcmp (argv[i], "-p"))

+	{

+	  const char *priority = argv[i + 1];

+

+	  priority = strrchr (priority, '/');

+	  if (priority++ &&

+	      (g_str_has_prefix (priority, "NORMAL:") ||

+	       g_str_has_prefix (priority, "NONE:")))

+	    g_setenv ("G_TLS_GNUTLS_PRIORITY", priority, TRUE);

+	  break;

+	}

+    }

   g_test_init (&argc, &argv, NULL);

   g_test_bug_base ("http://bugzilla.gnome.org/");

@@ -1431,6 +1510,15 @@ main (int   argc,

   g_test_add ("/tls/connection/async-implicit-handshake", TestConnection, NULL,

               setup_connection, test_async_implicit_handshake, teardown_connection);

+  g_test_add_data_func ("/tls/connection/fallback/SSL", PRIORITY_SSL_FALLBACK, test_fallback);

+  g_test_add ("/tls/connection/fallback/subprocess/" PRIORITY_SSL_FALLBACK,

+	      TestConnection, NULL,

+              setup_connection, test_fallback_subprocess, teardown_connection);

+  g_test_add_data_func ("/tls/connection/fallback/TLS", PRIORITY_TLS_FALLBACK, test_fallback);

+  g_test_add ("/tls/connection/fallback/subprocess/" PRIORITY_TLS_FALLBACK,

+	      TestConnection, NULL,

+              setup_connection, test_fallback_subprocess, teardown_connection);

+

   ret = g_test_run();

   /* for valgrinding */

-- 

2.1.0