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latchset / tang

Tang binding daemon
GNU General Public License v3.0
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Fix race condition when creating/rotating keys #123

Closed sergio-correia closed 1 year ago

sergio-correia commented 1 year ago

When we create/rotate keys using either the tangd-keygen and tangd-rotate-keys helpers, there is a small window between the keys being created and then the proper ownership permissions being set. This also happens when there are no keys and tang creates a pair of keys itself.

In certain situations, such as the keys directory having wide open permissions, a user with local access could exploit this race condition and read the keys before they are set to more restrictive permissions.

To prevent this issue, we now set the default umask to 0337 before creating the files, so that they are already created with restrictive permissions; afterwards, we set the proper ownership as usual.

Issue reported by Brian McDermott of CENSUS labs.

Fixes CVE-2023-1672

Reviewed-by: Sergio Arroutbi sarroutb@redhat.com

bmcdermott-census commented 1 year ago

Thanks Sergio, having tested this patch, I can confirm it fixed the issue