From a801543f79a2161815bd98d6846fc1526e9cd612 Mon Sep 17 00:00:00 2001
From: Sean Bright <sean.bright@gmail.com>
Date: Thu, 16 Aug 2018 11:45:53 -0400
Subject: [PATCH] AST-2018-009: Fix crash processing websocket HTTP Upgrade
requests
The HTTP request processing in res_http_websocket allocates additional
space on the stack for various headers received during an Upgrade request.
An attacker could send a specially crafted request that causes this code
to overflow the stack, resulting in a crash.
* No longer allocate memory from the stack in a loop to parse the header
values. NOTE: There is a slight API change when using the passed in
strings as is. We now require the passed in strings to no longer have
leading or trailing whitespace. This isn't a problem as the only callers
have already done this before passing the strings to the affected
function.
ASTERISK-28013 #close
Change-Id: Ia564825a8a95e085fd17e658cb777fe1afa8091a
---
res/res_http_websocket.c | 25 ++++++++++++++-----------
1 file changed, 14 insertions(+), 11 deletions(-)
diff --git a/res/res_http_websocket.c b/res/res_http_websocket.c
index 9a32bf37cc..d64ecba7f7 100644
--- a/res/res_http_websocket.c
+++ b/res/res_http_websocket.c
@@ -751,7 +751,8 @@ static void websocket_bad_request(struct ast_tcptls_session_instance *ser)
int AST_OPTIONAL_API_NAME(ast_websocket_uri_cb)(struct ast_tcptls_session_instance *ser, const struct ast_http_uri *urih, const char *uri, enum ast_http_method method, struct ast_variable *get_vars, struct ast_variable *headers)
{
struct ast_variable *v;
- char *upgrade = NULL, *key = NULL, *key1 = NULL, *key2 = NULL, *protos = NULL, *requested_protocols = NULL, *protocol = NULL;
+ const char *upgrade = NULL, *key = NULL, *key1 = NULL, *key2 = NULL, *protos = NULL;
+ char *requested_protocols = NULL, *protocol = NULL;
int version = 0, flags = 1;
struct ast_websocket_protocol *protocol_handler = NULL;
struct ast_websocket *session;
@@ -770,16 +771,15 @@ int AST_OPTIONAL_API_NAME(ast_websocket_uri_cb)(struct ast_tcptls_session_instan
/* Get the minimum headers required to satisfy our needs */
for (v = headers; v; v = v->next) {
if (!strcasecmp(v->name, "Upgrade")) {
- upgrade = ast_strip(ast_strdupa(v->value));
+ upgrade = v->value;
} else if (!strcasecmp(v->name, "Sec-WebSocket-Key")) {
- key = ast_strip(ast_strdupa(v->value));
+ key = v->value;
} else if (!strcasecmp(v->name, "Sec-WebSocket-Key1")) {
- key1 = ast_strip(ast_strdupa(v->value));
+ key1 = v->value;
} else if (!strcasecmp(v->name, "Sec-WebSocket-Key2")) {
- key2 = ast_strip(ast_strdupa(v->value));
+ key2 = v->value;
} else if (!strcasecmp(v->name, "Sec-WebSocket-Protocol")) {
- requested_protocols = ast_strip(ast_strdupa(v->value));
- protos = ast_strdupa(requested_protocols);
+ protos = v->value;
} else if (!strcasecmp(v->name, "Sec-WebSocket-Version")) {
if (sscanf(v->value, "%30d", &version) != 1) {
version = 0;
@@ -793,7 +793,7 @@ int AST_OPTIONAL_API_NAME(ast_websocket_uri_cb)(struct ast_tcptls_session_instan
ast_sockaddr_stringify(&ser->remote_address));
ast_http_error(ser, 426, "Upgrade Required", NULL);
return 0;
- } else if (ast_strlen_zero(requested_protocols)) {
+ } else if (ast_strlen_zero(protos)) {
/* If there's only a single protocol registered, and the
* client doesn't specify what protocol it's using, go ahead
* and accept the connection */
@@ -814,9 +814,12 @@ int AST_OPTIONAL_API_NAME(ast_websocket_uri_cb)(struct ast_tcptls_session_instan
return 0;
}
- /* Iterate through the requested protocols trying to find one that we have a handler for */
- while (!protocol_handler && (protocol = strsep(&requested_protocols, ","))) {
- protocol_handler = ao2_find(server->protocols, ast_strip(protocol), OBJ_KEY);
+ if (!protocol_handler && protos) {
+ requested_protocols = ast_strdupa(protos);
+ /* Iterate through the requested protocols trying to find one that we have a handler for */
+ while (!protocol_handler && (protocol = strsep(&requested_protocols, ","))) {
+ protocol_handler = ao2_find(server->protocols, ast_strip(protocol), OBJ_KEY);
+ }
}
/* If no protocol handler exists bump this back to the requester */
--
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