Backport

[citadel.git] / citadel / modules / xmpp / serv_xmpp.c

diff --git a/citadel/modules/xmpp/serv_xmpp.c b/citadel/modules/xmpp/serv_xmpp.c
index 31656c18b7c3b9f7a1ae91733c89f34ca370a3a9..b84634eb2e360c9bde01f74d750a3da3336aef34 100644 (file)
--- a/citadel/modules/xmpp/serv_xmpp.c
+++ b/citadel/modules/xmpp/serv_xmpp.c
@@ -1,10 +1,8 @@
 /*
- * $Id$ 
- *
  * XMPP (Jabber) service for the Citadel system
- * Copyright (c) 2007-2010 by Art Cancro
+ * Copyright (c) 2007-2011 by Art Cancro
  *
- * This program is free software; you can redistribute it and/or modify
+ * This program is open source software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 3 of the License, or
  * (at your option) any later version.
@@ -59,8 +57,30 @@
 #include "ctdl_module.h"
 #include "serv_xmpp.h"
 
+#if XML_MAJOR_VERSION > 0
+/* XML_StopParser is present in expat 2.x */
+#define HAVE_XML_STOPPARSER
+#endif
+
 struct xmpp_event *xmpp_queue = NULL;
 
+
+
+#ifdef HAVE_XML_STOPPARSER
+/* Stop the parser if an entity declaration is hit. */
+static void xmpp_entity_declaration(void *userData, const XML_Char *entityName,
+                               int is_parameter_entity, const XML_Char *value,
+                               int value_length, const XML_Char *base,
+                               const XML_Char *systemId, const XML_Char *publicId,
+                               const XML_Char *notationName
+) {
+       syslog(CTDL_WARNING, "Illegal entity declaration encountered; stopping parser.");
+       XML_StopParser(XMPP->xp, XML_FALSE);
+}
+#endif
+
+
+
 /*
  * Given a source string and a target buffer, returns the string
  * properly escaped for insertion into an XML stream.  Returns a
@@ -144,7 +164,7 @@ void xmpp_stream_start(void *data, const char *supplied_el, const char **attr)
        /* The features of this stream are... */
        cprintf("<stream:features>");
 
-#ifdef HAVE_OPENSSL_XXXX_COMMENTED_OUT
+#ifdef HAVE_OPENSSL
        /* TLS encryption (but only if it isn't already active) */
        if (!CC->redirect_ssl) {
                cprintf("<starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'></starttls>");
@@ -513,6 +533,7 @@ void xmpp_cleanup_function(void) {
  * Here's where our XMPP session begins its happy day.
  */
 void xmpp_greeting(void) {
+       client_set_inbound_buf(4);
        strcpy(CC->cs_clientname, "XMPP session");
        CC->session_specific_data = malloc(sizeof(citxmpp));
        memset(XMPP, 0, sizeof(citxmpp));
@@ -531,6 +552,17 @@ void xmpp_greeting(void) {
        XML_SetCharacterDataHandler(XMPP->xp, xmpp_xml_chardata);
        // XML_SetUserData(XMPP->xp, something...);
 
+       /* Prevent the "billion laughs" attack against expat by disabling
+        * internal entity expansion.  With 2.x, forcibly stop the parser
+        * if an entity is declared - this is safer and a more obvious
+        * failure mode.  With older versions, simply prevent expansion
+        * of such entities. */
+#ifdef HAVE_XML_STOPPARSER
+       XML_SetEntityDeclHandler(XMPP->xp, xmpp_entity_declaration);
+#else
+       XML_SetDefaultHandler(XMPP->xp, NULL);
+#endif
+
        CC->can_receive_im = 1;         /* This protocol is capable of receiving instant messages */
 }