GHSA-3cv2-h65g-fgmm astral-tokio-tar has a PAX Header Desynchronization issue

Impact

Versions of astral-tokio-tar prior to 0.6.2 contain a PAX header interpretation bug that allows manipulated entries to be made selectively visible or invisible during extraction with astral-tokio-tar versus other tar implementations. An attacker could use this differential to smuggle unexpected files onto a victim's filesystem.

Details

When a tar stream contains multiple "header" entries prior to a file entry, astral-tokio-tar applies the PAX header (x) to the next entry in the stream, regardless of type. For example, a stream of x -> L -> file (PAX, GNU longname, file) would result in x's extensions being applied to L rather than to file.

Per POSIX pax, this is incorrect: a PAX header always applies to a file entry, not any intermediary entries. See the "pax Header Block" section for the specific prescription there.

As a result of this, an attacker can contrive a tar containing a sequence of tar headers such that astral-tokio-tar applies the PAX header's size extension to the next header in sequence, effectively desynchronizing the stream and enabling astral-tokio-tar specific skippage/extraction of members. In other words, a file can be contrived to extract differently on astral-tokio-tar than on other tar parsers.

Patches

Versions 0.6.2 and newer of astral-tokio-tar address this differential.

Workarounds

Users are advised to upgrade to version 0.6.1 or newer to address this advisory.

There is no workaround other than upgrading. Users should experience no breaking changes as a result of the upgrade.

Resources

• GHSA-j5gw-2vrg-8fgx is a similar PAX desynchronization bug
• GHSA-fp55-jw48-c537 is another similar PAX desynchronization bug