December 1, 2000

Debian security advisory

Author: JT Smith

Help Net Security tells us that Colin Phipps found an interesting symlink attack problem in fsh (a tool to quickly run remote commands
over rsh/ssh/lsh). When fshd starts it creates a directory in /tmp to hold its sockets. It tries to do that
securely by checking of it can chown that directory if it already exists to check if it is owner by the user
invoking it. However an attacker can circumvent this check by inserting a symlink to a file that is owner
by the user who runs fhsd and replacing that with a directory just before fshd creates the socket.


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