Linux Zip Long Path Buffer Overflow Vulnerability

[Mobo]

Overview:
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Zip console application by Info-Zip (http://www.info-zip.org) is an open-source software and part of many Linux distributions. A buffer overflow condition can be triggered and exploited during recursive compression operation.

Affected products:
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HexView tested the issue using Zip 2.3 which comes as "zip" package with Debian Linux. Possibly all earlier Info-Zip versions are vulnerable. Info-Zip applications for other operating systems are also vulnerable, but depending on operating system and file system restrictions, the vulnerability may or may not be triggered or exploited.

Cause and Effect:
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When zip performs recursive folder compression, it does not check for the length of resulting path. If the path is too long, a buffer overflow occurs leading to stack corruption and segmentation fault. It is possible to exploit this vulnerability by embedding a shellcode in directory or file name. While the issue is not of primary concern for regular users, it can be critical for environments where zip archives are re-compressed automatically using Info-Zip application.

Demonstration:
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The issue can be reproduced by following these steps:
1. Create an 8-level directory structure, where each directory name is 256 characters long (we used 256 'a' characters).
2. run "zip -r file.zip *". The application will crash with "segmentation fault"
3. run "gdb -core core `which zip`" (assuming core drop is enabled)
4. type "where" and hit Enter. Here is what you'll see:

Program terminated with signal 11, Segmentation fault.
[garbage truncated]
#0 0x0805108e in error ()
#1 0x61616161 in ?? ()
#2 0x61616161 in ?? ()
#3 0x61616161 in ?? ()