From 3604fde3d3c9b0d0e389e079aecf470d123ba180 Mon Sep 17 00:00:00 2001
From: YAMADA Yasuharu <yasuharu.yamada@access-company.com>
Date: Thu, 11 Apr 2013 00:17:15 +0200
Subject: [PATCH] cookie: fix tailmatching to prevent cross-domain leakage

Cookies set for 'example.com' could accidentaly also be sent by libcurl
to the 'bexample.com' (ie with a prefix to the first domain name).

This is a security vulnerabilty, CVE-2013-1944.

Bug: http://curl.haxx.se/docs/adv_20130412.html
---
diff -up ./lib/cookie.c.CVE-2013-1944 ./lib/cookie.c
--- a/lib/cookie.c
+++ b/lib/cookie.c
@@ -113,15 +113,29 @@ free_cookiemess(struct Cookie *co)
   free(co);
 }
 
-static bool tailmatch(const char *little, const char *bigone)
+static bool tailmatch(const char *cooke_domain, const char *hostname)
 {
-  size_t littlelen = strlen(little);
-  size_t biglen = strlen(bigone);
+  size_t cookie_domain_len = strlen(cooke_domain);
+  size_t hostname_len = strlen(hostname);
 
-  if(littlelen > biglen)
+  if(hostname_len < cookie_domain_len)
     return FALSE;
 
-  return (bool)strequal(little, bigone+biglen-littlelen);
+  if(!(bool)strequal(cooke_domain, hostname+hostname_len-cookie_domain_len))
+    return FALSE;
+
+  /* A lead char of cookie_domain is not '.'.
+     RFC6265 4.1.2.3. The Domain Attribute says:
+       For example, if the value of the Domain attribute is
+       "example.com", the user agent will include the cookie in the Cookie
+       header when making HTTP requests to example.com, www.example.com, and
+       www.corp.example.com.
+   */
+  if(hostname_len == cookie_domain_len)
+    return TRUE;
+  if('.' == *(hostname + hostname_len - cookie_domain_len - 1))
+    return TRUE;
+  return FALSE;
 }
 
 /****************************************************************************