rdist /tmp File Race Condition Vulnerability

rdist is a freely available, open source software package distributed with numerous variants of the Linux Operating System. It is designed to maintain identical copies of files on numerous different machines, preserving as many different attributes of the file as possible.

A problem in the program exists that could allow for a symbolic link attack. Under some circumstances, rdist will create files in the /tmp directory. However, the files created in the /tmp file system are created insecurely, as the name of future files created by rdist can be predicted, and the program does not check for the existance of files before attempting to create them. It is possible to create a range of symbolic links in the /tmp file system using forecasted names of files that could be created by the rdist process, and symbolically linked to files that are write-accessible to the UID of the rdist process. This makes it possible for a user with malicious intent to overwrite or append to and corrupt files owned by another user, and potentially system files.


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