Openssl: disable session-tickets by default and session-cache always

(cherry picked from commit 7006ee24ecfd9d8f405f70d38cc36bdd91f8de87)

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index afd690ab8531a95379f80c6e3236c3e60d255403..5900b9c9e081dedfbb81702f7e0be4c7708d7849 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -15676,7 +15676,7 @@ harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
 transport driver.
 
 
-.option openssl_options main "string list" "+no_sslv2 +single_dh_use"
+.option openssl_options main "string list" "+no_sslv2 +single_dh_use +no_ticket"
 .cindex "OpenSSL "compatibility options"
 This option allows an administrator to adjust the SSL options applied
 by OpenSSL to connections.  It is given as a space-separated list of items,

diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog
index 74414039f22872645de12f6267cfbbdac8ffec8a..8035ec4a580c0ed0ccbf70be15b451a113b512b6 100644 (file)
--- a/doc/doc-txt/ChangeLog
+++ b/doc/doc-txt/ChangeLog
@@ -12,6 +12,15 @@ Cherry-Picked from the master development branch
 
 HS/01 Cleanup, prevent repeated use of -p/-oMr (CVE-2017-1000369)
 
+JH/06 Default openssl_options to include +no_ticket, to reduce load on peers.
+      Disable the session-cache too, which might reduce our load.  Since we
+      currrectly use a new context for every connection, both as server and
+      client, there is no benefit for these.
+      GnuTLS appears to not support tickets server-side by default (we don't
+      call gnutls_session_ticket_enable_server()) but client side is enabled
+      by default on recent versions (3.1.3 +) unless the PFS priority string
+      is used (3.2.4 +).
+
 
 Exim version 4.89
 -----------------

diff --git a/src/src/readconf.c b/src/src/readconf.c
index 790f073174846d8aa192167a7b59c2452aeea355..6a59dda710cfc16b5452013ce859aed98d13ab72 100644 (file)
--- a/src/src/readconf.c
+++ b/src/src/readconf.c
@@ -3787,14 +3787,14 @@ if (tls_dh_max_bits < 1024)
       "tls_dh_max_bits is too small, must be at least 1024 for interop");
 
 /* If openssl_options is set, validate it */
-if (openssl_options != NULL)
+if (openssl_options)
   {
 # ifdef USE_GNUTLS
   log_write(0, LOG_PANIC_DIE|LOG_CONFIG,
     "openssl_options is set but we're using GnuTLS");
 # else
   long dummy;
-  if (!(tls_openssl_options_parse(openssl_options, &dummy)))
+  if (!tls_openssl_options_parse(openssl_options, &dummy))
     log_write(0, LOG_PANIC_DIE|LOG_CONFIG,
       "openssl_options parse error: %s", openssl_options);
 # endif

diff --git a/src/src/tls-openssl.c b/src/src/tls-openssl.c
index 392d59dd5ac28223a9475203963a3a5473795ff4..60c07402b6cdc494d0d97222cb27a1c728f7c695 100644 (file)
--- a/src/src/tls-openssl.c
+++ b/src/src/tls-openssl.c
@@ -1426,9 +1426,9 @@ tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
 #endif
   address_item *addr, tls_ext_ctx_cb ** cbp)
 {
+SSL_CTX * ctx;
 long init_options;
 int rc;
-BOOL okay;
 tls_ext_ctx_cb * cbinfo;
 
 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
@@ -1499,10 +1499,10 @@ if (!RAND_status())
 /* Set up the information callback, which outputs if debugging is at a suitable
 level. */
 
-DEBUG(D_tls) SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
+DEBUG(D_tls) SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
 
 /* Automatically re-try reads/writes after renegotiation. */
-(void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
+(void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
 
 /* Apply administrator-supplied work-arounds.
 Historically we applied just one requested option,
@@ -1513,20 +1513,23 @@ grandfathered in the first one as the default value for "openssl_options".
 No OpenSSL version number checks: the options we accept depend upon the
 availability of the option value macros from OpenSSL.  */
 
-okay = tls_openssl_options_parse(openssl_options, &init_options);
-if (!okay)
+if (!tls_openssl_options_parse(openssl_options, &init_options))
   return tls_error(US"openssl_options parsing failed", host, NULL);
 
 if (init_options)
   {
   DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
-  if (!(SSL_CTX_set_options(*ctxp, init_options)))
+  if (!(SSL_CTX_set_options(ctx, init_options)))
     return tls_error(string_sprintf(
           "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
   }
 else
   DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
 
+/* Disable session cache unconditionally */
+
+(void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
+
 /* Initialize with DH parameters if supplied */
 /* Initialize ECDH temp key parameter selection */
 
@@ -1560,14 +1563,14 @@ if (host == NULL)               /* server */
   callback is invoked. */
   if (cbinfo->u_ocsp.server.file)
     {
-    SSL_CTX_set_tlsext_status_cb(server_ctx, tls_server_stapling_cb);
-    SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
+    SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
+    SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
     }
 # endif
   /* We always do this, so that $tls_sni is available even if not used in
   tls_certificate */
-  SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
-  SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
+  SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
+  SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
   }
 # ifndef DISABLE_OCSP
 else                   /* client */
@@ -1578,8 +1581,8 @@ else                      /* client */
       DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
       return FAIL;
       }
-    SSL_CTX_set_tlsext_status_cb(*ctxp, tls_client_stapling_cb);
-    SSL_CTX_set_tlsext_status_arg(*ctxp, cbinfo);
+    SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
+    SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
     }
 # endif
 #endif
@@ -1588,15 +1591,16 @@ cbinfo->verify_cert_hostnames = NULL;
 
 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
 /* Set up the RSA callback */
-SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
+SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
 #endif
 
 /* Finally, set the timeout, and we are done */
 
-SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
+SSL_CTX_set_timeout(ctx, ssl_session_timeout);
 DEBUG(D_tls) debug_printf("Initialized TLS\n");
 
 *cbp = cbinfo;
+*ctxp = ctx;
 
 return OK;
 }
@@ -2955,7 +2959,7 @@ uschar *s, *end;
 uschar keep_c;
 BOOL adding, item_parsed;
 
-result = 0L;
+result = SSL_OP_NO_TICKET;
 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
  * from default because it increases BEAST susceptibility. */
 #ifdef SSL_OP_NO_SSLv2
@@ -2965,7 +2969,7 @@ result |= SSL_OP_NO_SSLv2;
 result |= SSL_OP_SINGLE_DH_USE;
 #endif
 
-if (option_spec == NULL)
+if (!option_spec)
   {
   *results = result;
   return TRUE;