🛡️ Sentinel: [HIGH] Fix timing side-channel vulnerability in constant-time comparison#319
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Code Review
This pull request replaces a manual constant-time equality implementation with the subtle crate's ConstantTimeEq trait. Feedback suggests managing the new dependency via the workspace root for consistency and removing a now-redundant length check within the constant_time_eq function.
| [dependencies] | ||
| jsonwebtoken = { version = "10.2.0", features = ["rust_crypto"] } | ||
| serde.workspace = true | ||
| subtle = "2.6.1" |
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For consistency and better dependency management within the workspace, it's recommended to define this dependency in the root Cargo.toml and reference it here using subtle.workspace = true. This aligns with how other dependencies like serde and tracing are managed in this file.
| subtle = "2.6.1" | |
| subtle.workspace = true |
| } | ||
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| left.bytes().zip(right.bytes()).fold(0_u8, |acc, (x, y)| acc | (x ^ y)) == 0 | ||
| left.as_bytes().ct_eq(right.as_bytes()).into() |
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The ct_eq method on slices from the subtle crate already includes a length check. This makes the explicit length check on lines 93-95 redundant. Consider removing it to simplify the function.
Test Results283 tests 245 ✅ 11m 23s ⏱️ Results for commit f565d33. |
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🚨 Severity: HIGH
💡 Vulnerability: The
constant_time_eqimplementation manually iterated over bytes using a bitwisefold(^). Compilers (like LLVM) often recognize these patterns and aggressively optimize them into standard, short-circuiting sequence comparisons (or auto-vectorize them in ways that vary execution time). This optimization defeats the constant-time intent, re-introducing potential timing side-channels during token verification.🎯 Impact: Attackers could potentially use timing measurements to iteratively guess valid authentication tokens character by character.
🔧 Fix: Replaced the manual implementation with the industry-standard
subtlecrate'sConstantTimeEqtrait (ct_eq). Thesubtlecrate uses compiler black-boxes and inline assembly to guarantee constant-time evaluation and prevent dangerous compiler optimizations. Addedsubtleas a dependency inCargo.toml.✅ Verification: Ran
cargo fmt,cargo clippy, andcargo test -p http-auth-verifier. All 18 tests passed successfully.PR created automatically by Jules for task 2180715446142688830 started by @EffortlessSteven