[Full-disclosure] Crash in LIVE555 Media Server 2007.11.01

2007-11-1900:00:00

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                         Luigi Auriemma

Application: LIVE555 Media Server
http://www.live555.com/mediaServer/
Versions: <= 2007.11.01
Platforms: *nix, Windows, Mac and others
Bug: crash caused by access to unallocated memory
Exploitation: remote, versus server
Date: 18 Nov 2007
Author: Luigi Auriemma
e-mail: [email protected]
web: aluigi.org

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1) Introduction
2) Bug
3) The Code
4) Fix

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===============
1) Introduction

LIVE555 Media Server is an open source RTSP server application released
under LGPL.

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======
2) Bug

The function which handles the incoming queries from the clients is
affected by a vulnerability which allows an attacker to crash the
server remotely using the smallest RTSP query possible to use.

This problem is caused by the absence of an instruction for checking if
the amount of client's data (reqStrSize) is longer or equal than 8
bytes because the function makes use of unsigned numbers, so "7 - 8" is
not -1 but 4294967295, resulting in a crash caused by the reaching of
the end of the allocated memory.

>From liveMedia/RTSPCommon:

Boolean parseRTSPRequestString(char const* reqStr,
unsigned reqStrSize,
…
unsigned i;
for (i = 0; i < resultCmdNameMaxSize-1 && i < reqStrSize; ++i) {

...

// Skip over the prefix of any "rtsp://" or "rtsp:/" URL that follows:
unsigned j = i+1;
while (j < reqStrSize && (reqStr[j] == ' ' || reqStr[j] == '\t')) ++j;
for (j = i+1; j < reqStrSize-8; ++j) {
…

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