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From 25089c2c69028f0549facf93f7bdbf7344277f09 Mon Sep 17 00:00:00 2001
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From: Daniel Stenberg <daniel@haxx.se>
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Date: Sun, 19 May 2013 23:24:29 +0200
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Subject: [PATCH] Curl_urldecode: no peeking beyond end of input buffer
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Security problem: CVE-2013-2174
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If a program would give a string like "%FF" to curl_easy_unescape() but
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ask for it to decode only the first byte, it would still parse and
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decode the full hex sequence. The function then not only read beyond the
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allowed buffer but it would also deduct the *unsigned* counter variable
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for how many more bytes there's left to read in the buffer by two,
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making the counter wrap. Continuing this, the function would go on
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reading beyond the buffer and soon writing beyond the allocated target
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buffer...
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Bug: http://curl.haxx.se/docs/adv_20130622.html
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Reported-by: Timo Sirainen
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[upstream commit 192c4f788d48f82c03e9cef40013f34370e90737]
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Signed-off-by: Kamil Dudka <kdudka@redhat.com>
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---
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lib/escape.c | 3 ++-
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1 files changed, 2 insertions(+), 1 deletions(-)
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diff --git a/lib/escape.c b/lib/escape.c
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index 6a26cf8..a567edb 100644
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--- a/lib/escape.c
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+++ b/lib/escape.c
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@@ -159,7 +159,8 @@ CURLcode Curl_urldecode(struct SessionHandle *data,
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while(--alloc > 0) {
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in = *string;
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- if(('%' == in) && ISXDIGIT(string[1]) && ISXDIGIT(string[2])) {
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+ if(('%' == in) && (alloc > 2) &&
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+ ISXDIGIT(string[1]) && ISXDIGIT(string[2])) {
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/* this is two hexadecimal digits following a '%' */
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char hexstr[3];
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char *ptr;
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--
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1.7.1
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