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authorJason A. Donenfeld <Jason@zx2c4.com>2013-05-25 19:47:15 +0200
committerJason A. Donenfeld <Jason@zx2c4.com>2013-05-25 20:33:28 +0200
commitfe36f84d843cd755c6dab629a0758264de5bcc00 (patch)
treefee8af2ed0f3df2fa9015453ce3e8d721df6a0cd /cache.c
parentcgitrc.5: information on directory traversal and multiple readme files (diff)
downloadcgit-pink-fe36f84d843cd755c6dab629a0758264de5bcc00.tar.gz
cgit-pink-fe36f84d843cd755c6dab629a0758264de5bcc00.zip
ui-summary: Disallow directory traversal
Using the url= query string, it was possible request arbitrary files
from the filesystem if the readme for a given page was set to a
filesystem file. The following request would return my /etc/passwd file:

http://git.zx2c4.com/?url=/somerepo/about/../../../../etc/passwd
http://data.zx2c4.com/cgit-directory-traversal.png

This fix uses realpath(3) to canonicalize all paths, and then compares
the base components.

This fix introduces a subtle timing attack, whereby a client can check
whether or not strstr is called using timing measurements in order
to determine if a given file exists on the filesystem.

This fix also does not account for filesystem race conditions (TOCTOU)
in resolving symlinks.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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