- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Polytechnic University ISIS Security Advisory PUISIS10212005 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - http://isis.poly.edu/ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~ Application: Electric Sheep v2.6.3 ~ Severity: Medium-High ~ Title: Multiple Network-related Vulnerabilities in Electric Sheep ~ Date: October 20, 2005 ~ ID: PUISIS10212005 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Summary ======== The lack of an authentication framework for downloaded sheep mpegs, as well as its dependence on and vulnerabilities in cURL allows an attacker to send and display arbitrary movie files in the Electric Sheep client and perform arbitrary local and remote code execution. Background ========== "Electric Sheep is a free, open source screen saver run by thousands of people all over the world. It can be installed on any ordinary PC or Mac. When these computers "sleep", the screen saver comes on and the computers communicate with each other by the internet to share the work of creating morphing abstract animations known as "sheep." http://electricsheep.org/ Description =========== By spoofing the DNS entry for sheepserver.net or otherwise redirecting the Electric Sheep client to a malicious sheep server, it is possible to force the Electric Sheep client to download and display arbitrary mpegs due to a lack of authentication of the sheep server and sheep mpegs. At minimum, a rogue sheep server would need to respond to the Electric Sheep client with list.gz, a list of sheep available for download, and the referenced mpegs. To properly display the mpegs, they need to contain special footer information which can be found at the bottom of any pre-existing Electric Sheep mpegs. Electric sheep uses cURL internally for interaction with the Electric Sheep server. Two recent vulnerabilities in cURL can be exploited through malicious interaction with the Electric Sheep client. As in the previous vulnerability, spoofing the DNS entry of sheepserver.net or otherwise redirecting the Electric Sheep client to a malicious sheep server and replacing it with an appropriate HTTP 30x response can allow remote code execution through cURL due to an NTLM buffer overflow vulnerability [1,2]. Calling the Electric Sheep client by command line, configuration file, or otherwise with a malicious sheep server URL allows local code execution through cURL due to a URL buffer overflow vulnerability. In addition, by redirecting the Electric Sheep client to a rogue sheep server and supplying a list of maliciously formatted URLs it is possible to exploit the same cURL URL buffer overflow vulnerability remotely. This is possible because the Electric Sheep client makes direct system calls to the vulnerable cURL application from network supplied input [3,4]. Impact ====== Spoofing the DNS entry for sheepserver.net or otherwise redirecting the Electric Sheep client to a rogue sheep server, it is possible to remotely control the video displayed or remotely execute code on all Electric Sheep clients affected by such a redirection. Local code execution is also possible due to a cURL vulnerability. Workaround ========== The vendor was notified on November 18, 2005. The vendor was extremely responsive and cooperative in regards to these security issues. All issues are fixed in the CVS HEAD of Electric Sheep client development and will be included in the next release. References ========== [ 1 ] libcurl NTLM Buffer Overflow Vulnerability http://curl.haxx.se/docs/adv_20051013.html [ 2 ] CVE-2005-3185 http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-3185 [ 3 ] libcurl URL Buffer Overflow Vulnerability http://curl.haxx.se/docs/adv_20051207.html [ 4 ] CVE-2005-4077 http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-4077 About ===== The Information Systems and Internet Security (ISIS) Laboratory is an NSF funded laboratory designed to facilitate hands-on experimentation and project work in issues related to information security. It provides the focus for multidisciplinary research and education in emerging areas of security. Polytechnic University, an NSA Center of Academic Excellence in Information Assurance Education, houses the lab. These vulnerabilities were discovered during coursework performed for "Penetration Testing & Vulnerability Analysis" offered at Polytechnic University (http://www.poly.edu) during the Fall 2005 semester. License ======= The contents of this document are licensed under the Creative Commons - Attribution / Share Alike license. http://creativecommons.org/licenses/by-sa/2.5 Authors ======= Daniel Guido dguido (at) gmail (dot) com [email concealed] Michael Aiello http://www.michaelaiello.com/