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/tmp symlink file clobbering with Solaris Update Manager
From: bugs <bugs () fbi dhs org>
Date: Wed, 24 Mar 2010 12:39:44 -0400




Symlink attack with Solaris Update manager and Sun Patch Cluster
Larry W. Cashdollar
Vapid Labs http://vapid.dhs.org
1/24/2009


Many patches use insecure file creation in /tmp to store data during
installation.  The easiest one to exploit is /tmp/CLEANUP which is used in
a handful of package installation scripts:

script code is typically:

CLEANUP_FILE=/tmp/CLEANUP
 echo "EXISTING_FILE_PRESERVED: ${dest} ${dest}.${TAG}" \
                        >> ${CLEANUP_FILE}
Similar code is found in:

./118833-36/SUNWcsr/install/i.renamenew
./118833-36/SUNWcsr/install/u.initd
./118833-36/SUNWcsr/install/i.initd
./118833-36/SUNWcsr/install/preinstall
./118833-36/SUNWintgige/install/i.renamenew
./118833-36/SUNWvolr/install/u.initd
./118833-36/SUNWvolr/install/i.initd
./118833-36/SUNWsndmu/install/postinstall
./118833-36/SUNWsacom/install/i.initd
./118833-36/SUNWsacom/install/u.initd
./118833-36/SUNWsndmr/install/postinstall
./118833-36/SUNWsndmr/install/i.renameold
./120272-26/SUNWsmmgr/install/u.initd
./120272-26/SUNWsmmgr/install/i.initd
./137093-01/SUNWcsr/install/i.renameold
./137137-09/SUNWnxge.u/install/i.renameold
./137137-09/SUNWcsr/install/i.renamenew
./137137-09/SUNWcsr/install/i.renameold
./137137-09/SUNWckr/install/i.renameold
./137137-09/SUNWnxge.v/install/i.renameold
./141444-09/SUNWixgbe/install/i.renamenew
./141444-09/SUNWnxge.u/install/i.renamenew
./141444-09/SUNWnxge.v/install/i.renamenew
./127127-11/SUNWtsg/install/preinstall
./127127-11/SUNWtsg/install/i.renamenew
./127127-11/SUNWtsu/install/i.renamenew
./127127-11/SUNWypr/install/i.renameold
./127127-11/SUNWcsr/install/i.group
./127127-11/SUNWcsr/install/i.pamconf
./127127-11/SUNWcsr/install/i.passwd
./127127-11/SUNWcsr/install/i.renamenew
./125555-06/SUNWcsu/reloc/usr/lib/patch/patch_override_dir/137137_SUNWnxge_i.renameold
./122660-10/SUNWcsr/install/preinstall
./119313-29/SUNWwbcor/install/i.initd
./119313-29/README.119313-29
./120011-14/SUNWckr/install/i.renameold
./120011-14/SUNWcsr/install/i.renamenew
./120011-14/SUNWcsr/install/i.renameold
./120011-14/SUNWcsr/install/preinstall
./120011-14/SUNWsndmu/install/postinstall
./120011-14/SUNWsndmr/install/i.renameold
./121453-02/undo_pkgs.pkg
./121453-02/payload.pkg
./121453-02/SUNWppror/install/i.initd
./122911-19/README.122911-19
./122911-19/SUNWapchr/install/i.initd
./122911-19/SUNWapchr/install/i.renamenew
./122911-19/SUNWapchr/install/u.initd
./122911-19/SUNWtcatr/install/i.renamenew
./139555-08/SUNWcsr/install/i.renamenew
./120543-15/SUNWapch2r/install/i.renamenew
./125215-03/SUNWwgetr/install/i.renamenew



If a user creates a symlink to a root owned file, /etc/shadow for example
it will be clobbered by the patch installation process if that patch
application applies to the system.

$ cd /tmp
$ ln -s /etc/shadow CLEANUP

I was able to append the contents of CLEANUP to /etc/shadow.

With the GUI Sun Update Manager being used to install patches on a system
local users can easily run scripts and create symlinks in an attempt to
clobber files and potentially escalate priviledges as this application is
typically run in multi user mode.

There are other attackable files that are created as well. I have only
investigated the easiest one however.

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