GNU tar 1.34: 10.2.4 Security Rules of Thumb
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10.2.4 Security Rules of Thumb
This section briefly summarizes rules of thumb for avoiding security pitfalls.
- Protect archives at least as much as you protect any of the files being archived.
- Extract from an untrusted archive only into an otherwise-empty directory. This directory and its parent should be accessible only to trusted users. For example: $ chmod go-rwx . $ mkdir -m go-rwx dir $ cd dir $ tar -xvf /archives/got-it-off-the-net.tar.gz As a corollary, do not do an incremental restore from an untrusted archive.
- Do not let untrusted users access files extracted from untrusted archives without checking first for problems such as setuid programs.
- Do not let untrusted users modify directories that are ancestors of top-level arguments of
tar. For example, while you are executing ‘tar -cf /archive/u-home.tar /u/home’, do not let an untrusted user modify ‘/’, ‘/archive’, or ‘/u’. - Pay attention to the diagnostics and exit status of
tar. - When archiving live file systems, monitor running instances of
tarto detect denial-of-service attacks. - Avoid unusual options such as ‘
--absolute-names’ (‘-P’), ‘--dereference’ (‘-h’), ‘--overwrite’, ‘--recursive-unlink’, and ‘--remove-files’ unless you understand their security implications.
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