expanded comment, noting size types and API issue

[exim.git] / src / src / tls-gnu.c

diff --git a/src/src/tls-gnu.c b/src/src/tls-gnu.c
index 05a3e084c2d9e71a71069763beb60e34494cde9c..b2659d7a794c208f795ab7da15404c6a8978e57f 100644 (file)
--- a/src/src/tls-gnu.c
+++ b/src/src/tls-gnu.c
@@ -395,6 +395,15 @@ DEBUG(D_tls)
       dh_bits);
 #endif
 
+/* Some clients have hard-coded limits. */
+if (dh_bits > tls_dh_max_bits)
+  {
+  DEBUG(D_tls)
+    debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
+        tls_dh_max_bits);
+  dh_bits = tls_dh_max_bits;
+  }
+
 if (!string_format(filename, sizeof(filename),
       "%s/gnutls-params-%d", spool_directory, dh_bits))
   return tls_error(US"overlong filename", NULL, NULL);
@@ -503,8 +512,13 @@ if (rc < 0)
   m.data = malloc(m.size);
   if (m.data == NULL)
     return tls_error(US"memory allocation failed", strerror(errno), NULL);
+  /* this will return a size 1 less than the allocation size above; I
+  originally used sz so as to avoid type compatibility errors, as gnutls_datum
+  uses "unsigned int" for the size field, but this call takes separate data
+  and size fields, with the latter being a size_t*.  For now, we live with
+  the error as being safer than throwing away type information. */
   rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
-      m.data, &sz);
+      m.data, &m.size);
   if (rc != GNUTLS_E_SUCCESS)
     {
     free(m.data);
@@ -870,6 +884,7 @@ state->host = host;
 
 state->tls_certificate = certificate;
 state->tls_privatekey = privatekey;
+state->tls_require_ciphers = require_ciphers;
 state->tls_sni = sni;
 state->tls_verify_certificates = cas;
 state->tls_crl = crl;
@@ -1183,7 +1198,14 @@ return TRUE;
 static void
 exim_gnutls_logger_cb(int level, const char *message)
 {
-  DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s\n", level, message);
+  size_t len = strlen(message);
+  if (len < 1)
+    {
+    DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
+    return;
+    }
+  DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
+      message[len-1] == '\n' ? "" : "\n");
 }
 #endif
 
@@ -1821,6 +1843,64 @@ vaguely_random_number(int max)
 
 
 
+/*************************************************
+*  Let tls_require_ciphers be checked at startup *
+*************************************************/
+
+/* The tls_require_ciphers option, if set, must be something which the
+library can parse.
+
+Returns:     NULL on success, or error message
+*/
+
+uschar *
+tls_validate_require_cipher(void)
+{
+int rc;
+uschar *expciphers = NULL;
+gnutls_priority_t priority_cache;
+const char *errpos;
+
+#define validate_check_rc(Label) do { \
+  if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
+  return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
+#define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
+
+if (exim_gnutls_base_init_done)
+  log_write(0, LOG_MAIN|LOG_PANIC,
+      "already initialised GnuTLS, Exim developer bug");
+
+rc = gnutls_global_init();
+validate_check_rc(US"gnutls_global_init()");
+exim_gnutls_base_init_done = TRUE;
+
+if (!(tls_require_ciphers && *tls_require_ciphers))
+  return_deinit(NULL);
+
+if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
+  return_deinit(US"failed to expand tls_require_ciphers");
+
+if (!(expciphers && *expciphers))
+  return_deinit(NULL);
+
+DEBUG(D_tls)
+  debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
+
+rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
+validate_check_rc(string_sprintf(
+      "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
+      expciphers, errpos - CS expciphers, errpos));
+
+#undef return_deinit
+#undef validate_check_rc
+gnutls_global_deinit();
+
+return NULL;
+}
+
+
+
+
 /*************************************************
 *         Report the library versions.           *
 *************************************************/