Collect GnuTLS extensions and use them to set %DUMBFW if supported

* lisp/net/gnutls.el (gnutls-boot-parameters): Use it to set %DUMBFW
only when it's supported as "ClientHello Padding" (Bug#25061).

* src/gnutls.c (Fgnutls_available_p): Get extension names and
put them in the GnuTLS capabilities, using a hard-coded limit
of 100 since GnuTLS MAX_EXT_TYPES is not exported.

1 files changed, 13 insertions, 1 deletions

diff --git a/src/gnutls.c b/src/gnutls.c
index 4622011bc10..8db201ae834 100644
--- a/src/gnutls.c
+++ b/src/gnutls.c
@@ -2415,7 +2415,10 @@ GnuTLS 3 or higher      : the list will contain `gnutls3'.
 GnuTLS MACs             : the list will contain `macs'.
 GnuTLS digests          : the list will contain `digests'.
 GnuTLS symmetric ciphers: the list will contain `ciphers'.
-GnuTLS AEAD ciphers     : the list will contain `AEAD-ciphers'.  */)
+GnuTLS AEAD ciphers     : the list will contain `AEAD-ciphers'.
+%DUMBFW                 : the list will contain `ClientHello\ Padding'.
+Any GnuTLS extension with ID up to 100
+                        : the list will contain its name.  */)
   (void)
 {
   Lisp_Object capabilities = Qnil;
@@ -2436,6 +2439,15 @@ GnuTLS AEAD ciphers     : the list will contain `AEAD-ciphers'.  */)
   capabilities = Fcons (intern("macs"), capabilities);
 # endif   /* HAVE_GNUTLS3 */
 
+  for (unsigned int ext=0; ext < 100; ext++)
+    {
+      const char* name = gnutls_ext_get_name(ext);
+      if (name != NULL)
+        {
+          capabilities = Fcons (intern(name), capabilities);
+        }
+    }
+
 # ifdef WINDOWSNT
   Lisp_Object found = Fassq (Qgnutls, Vlibrary_cache);
   if (CONSP (found))