From 25089c2c69028f0549facf93f7bdbf7344277f09 Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Sun, 19 May 2013 23:24:29 +0200
Subject: [PATCH] Curl_urldecode: no peeking beyond end of input buffer

Security problem: CVE-2013-2174

If a program would give a string like "%FF" to curl_easy_unescape() but
ask for it to decode only the first byte, it would still parse and
decode the full hex sequence. The function then not only read beyond the
allowed buffer but it would also deduct the *unsigned* counter variable
for how many more bytes there's left to read in the buffer by two,
making the counter wrap. Continuing this, the function would go on
reading beyond the buffer and soon writing beyond the allocated target
buffer...

Bug: http://curl.haxx.se/docs/adv_20130622.html
Reported-by: Timo Sirainen

[upstream commit 192c4f788d48f82c03e9cef40013f34370e90737]

Signed-off-by: Kamil Dudka <kdudka@redhat.com>
---
 lib/escape.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/lib/escape.c b/lib/escape.c
index 6a26cf8..a567edb 100644
--- a/lib/escape.c
+++ b/lib/escape.c
@@ -159,7 +159,8 @@ CURLcode Curl_urldecode(struct SessionHandle *data,
 
   while(--alloc > 0) {
     in = *string;
-    if(('%' == in) && ISXDIGIT(string[1]) && ISXDIGIT(string[2])) {
+    if(('%' == in) && (alloc > 2) &&
+       ISXDIGIT(string[1]) && ISXDIGIT(string[2])) {
       /* this is two hexadecimal digits following a '%' */
       char hexstr[3];
       char *ptr;
-- 
1.7.1