Re: [Full-disclosure] FYI: Apache httpd NoFollowSymLink follows symlinks feature



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Christian Sciberras wrote:
I think you meant "apache follows symlinks even when -FollowSymLinks
is *not* set". Otherwise it doesn't seem to make sense?

No. Unless I made a mistake while testing AND misunderstood the
documentation, even with -FollowSymLinks set, apache will follow
symlinks (see POC). You might want to read the last line in section
"FollowSymlink" in

http://httpd.apache.org/docs/2.2/mod/core.html#options

I, for myself, made the same assumption about -FollowSymLink, but the
specification states, that the symlink-check is not race-free.

On Fri, Jun 24, 2011 at 5:14 PM, halfdog <me@xxxxxxxxxxx
<mailto:me@xxxxxxxxxxx>> wrote:

For those, who did not already know:

Due to specification, apache follows symlinks even when
-FollowSymLinks is set, when the data is modified concurrently. This
can be trivially shown as demonstrated in
http://www.halfdog.net/Security/2011/ApacheNoFollowSymlinkTimerace/ .
When performing host hardening, do not think, the -FollowSymLinks
option alone will prevent you from symlink attacks.


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