[glib-networking/wip/danw/poodle: 2/2] gnutls: update default priority string and fallback rules

[Dan Winship <danw src gnome org>]

commit 5f00871566b342293a418624f81663559ed1088a
Author: Dan Winship <danw gnome org>
Date:   Thu Nov 13 22:30:13 2014 -0500

    gnutls: update default priority string and fallback rules
    
    Change the default "priority" string from "NORMAL:%COMPAT" to
    "NORMAL:%COMPAT:%LATEST_RECORD_VERSION". (Correctly-implemented
    servers won't care either way, but apparently some servers have been
    incorrectly updated for POODLE-safeness by rejecting all handshakes
    with SSL 3.0 in the version field [which had long been recommended for
    compatibility reasons], even if the handshake offered to negotiate TLS
    versions too.)
    
    Change the fallback/"ssl3" priority code so that it never includes
    %LATEST_RECORD_VERSION, but does include %COMPAT even if the default
    priority doesn't (eg, because it was overridden with
    G_TLS_GNUTLS_PRIORITY).
    
    https://bugzilla.gnome.org/show_bug.cgi?id=738633
    https://bugzilla.gnome.org/show_bug.cgi?id=740087

 tls/gnutls/gtlsconnection-gnutls.c |   23 +++++++++++++++++++----
 1 files changed, 19 insertions(+), 4 deletions(-)
---
diff --git a/tls/gnutls/gtlsconnection-gnutls.c b/tls/gnutls/gtlsconnection-gnutls.c
index 444ca36..7436451 100644
--- a/tls/gnutls/gtlsconnection-gnutls.c
+++ b/tls/gnutls/gtlsconnection-gnutls.c
@@ -197,6 +197,8 @@ g_tls_connection_gnutls_init (GTlsConnectionGnutls *gnutls)
 /* First field is "fallback", second is "allow unsafe rehandshaking" */
 static gnutls_priority_t priorities[2][2];
 
+#define DEFAULT_BASE_PRIORITY "NORMAL:%COMPAT:%LATEST_RECORD_VERSION"
+
 static void
 g_tls_connection_gnutls_init_priorities (void)
 {
@@ -207,12 +209,12 @@ g_tls_connection_gnutls_init_priorities (void)
 
   base_priority = g_getenv ("G_TLS_GNUTLS_PRIORITY");
   if (!base_priority)
-    base_priority = "NORMAL:%COMPAT";
+    base_priority = DEFAULT_BASE_PRIORITY;
   ret = gnutls_priority_init (&priorities[FALSE][FALSE], base_priority, NULL);
   if (ret == GNUTLS_E_INVALID_REQUEST)
     {
       g_warning ("G_TLS_GNUTLS_PRIORITY is invalid; ignoring!");
-      base_priority = "NORMAL:%COMPAT";
+      base_priority = DEFAULT_BASE_PRIORITY;
       gnutls_priority_init (&priorities[FALSE][FALSE], base_priority, NULL);
     }
 
@@ -236,8 +238,21 @@ g_tls_connection_gnutls_init_priorities (void)
     }
   else
     {
-      fallback_priority = g_strdup_printf ("%s:!VERS-TLS-ALL:+VERS-%s",
-                                          base_priority,
+      gchar *cleaned_base, *p, *rest;
+
+      /* fallback_priority should be based on base_priority, except
+       * that we don't want %LATEST_RECORD_VERSION in it.
+       */
+      cleaned_base = g_strdup (base_priority);
+      p = strstr (cleaned_base, ":%LATEST_RECORD_VERSION");
+      if (p)
+       {
+         rest = p + strlen (":%LATEST_RECORD_VERSION");
+         memmove (p, rest, strlen (rest) + 1);
+       }
+
+      fallback_priority = g_strdup_printf ("%s:%%COMPAT:!VERS-TLS-ALL:+VERS-%s",
+                                          cleaned_base,
                                           gnutls_protocol_get_name (fallback_proto));
     }
   fallback_unsafe_rehandshake_priority = g_strdup_printf ("%s:%%UNSAFE_RENEGOTIATION",