recovery: add O_NOFOLLOW|O_EXCL to prevent symlink-following in recovery file creation#448
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ebiggers merged 1 commit intogoogle:masterfrom Apr 15, 2026
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…ery file creation WriteRecoveryInstructions() opens the recovery README with os.OpenFile using O_WRONLY|O_CREATE without O_NOFOLLOW. When fscrypt encrypt runs as root, this allows a local attacker to place a symlink at the recovery file path, causing root to write through the symlink and then fchown the target file to the attacker. Adding O_EXCL|O_NOFOLLOW aligns with the existing security pattern in filesystem.go:608 and filesystem.go:747.
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ebiggers
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Apr 15, 2026
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Merged, thanks. |
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WriteRecoveryInstructions() at recovery.go:94 opens the recovery README
with os.O_WRONLY|os.O_CREATE without O_NOFOLLOW. When fscrypt encrypt
runs as root via sudo, a local attacker who controls the parent directory
can place a symlink at the recovery file path, causing root to write
through the symlink and fchown the target to the attacker.
The rest of the codebase uses O_NOFOLLOW consistently:
This change adds os.O_EXCL|unix.O_NOFOLLOW to align with the existing
security pattern.