🛡️ Sentinel: [CRITICAL] Fix TOCTOU vulnerability in config permissions enforcement#278
🛡️ Sentinel: [CRITICAL] Fix TOCTOU vulnerability in config permissions enforcement#278acebytes wants to merge 1 commit into
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Co-authored-by: acebytes <2820910+acebytes@users.noreply.github.com>
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| let fd = open(path, O_RDONLY | O_NOFOLLOW) | ||
| if fd >= 0 { | ||
| fchmod(fd, 0o600) |
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Opening the config with open(..., O_RDONLY | O_NOFOLLOW) requires read permission before fchmod can run, so a config owned by the daemon but currently mode 0000/write-only can no longer be repaired to 0600. In that case open fails, permissions remain unchanged, and the subsequent read fails, which is a functional regression from the previous chmod(path, 0o600) behavior that could recover mis-mode files.
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| } else { | ||
| logger.error("Failed to safely open config for permissions check at \(path, privacy: .public)") | ||
| } | ||
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| // Read file |
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If open(..., O_NOFOLLOW) fails (notably on symlinks), this branch only logs an error and then continues to FileManager.default.contents(atPath:), which still reads the path target. That means the code proceeds with config loading even though the permission-enforcement step did not run, so symlinked or otherwise unfixable files bypass the intended 0600 enforcement path.
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| // Enforce 0600 permissions | ||
| chmod(path, 0o600) | ||
| // Enforce 0600 permissions safely to avoid TOCTOU symlink attacks | ||
| let fd = open(path, O_RDONLY | O_NOFOLLOW) |
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Using open(path, O_RDONLY | O_NOFOLLOW) can block indefinitely when the path is a FIFO with no writer, because read-only open() on FIFOs blocks unless O_NONBLOCK is set. Since fileExists(atPath:) is true for FIFOs, a malicious or accidental replacement of the config path with a named pipe can stall this reload path and prevent config processing.
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🚨 Severity: CRITICAL
💡 Vulnerability: Time-of-Check to Time-of-Use (TOCTOU) vulnerability where
chmod()is called directly on a file path, allowing an attacker to swap the file with a symlink beforechmod()executes, potentially altering permissions of arbitrary system files.🎯 Impact: High - allows unprivileged users to change permissions on any file on the system.
🔧 Fix: Replaced
chmod()withopen(O_NOFOLLOW)andfchmod()to securely enforce permissions without following symlinks.✅ Verification: Ran test suite and verified code builds.
PR created automatically by Jules for task 12808968433134621780 started by @acebytes