max / makenotwork

1.6 KB · 44 lines History Blame Raw

1	//! Shared HTTP-daemon helpers for the operator tools (Sando, Bento).
2	//!
3	//! Both daemons expose a small axum service guarded by a single bearer token,
4	//! and both compared that token the same way — a constant-time byte compare, to
5	//! the byte, test included. That one belongs here so there is exactly one copy.
6	//!
7	//! Not everything the two daemons appear to share actually is: `require_bearer`
8	//! diverged (Sando attributes each authenticated POST to its peer; Bento leaves
9	//! reads open and logs nothing), and the `Error` → response mappers carry
10	//! different variants and leak postures (Bento answers a leak-safe JSON
11	//! envelope; Sando returns `to_string()` text). Folding those is a behavior
12	//! change, not a mechanical dedup, so each daemon keeps its own — only the
13	//! genuinely identical primitive lives here.
14
15	/// Constant-time string compare for bearer tokens. The length may leak (a
16	/// token's length is not the secret); the byte comparison does not
17	/// short-circuit, so a matching prefix is not distinguishable by timing.
18	#[must_use]
19	pub fn ct_eq(a: &str, b: &str) -> bool {
20	let (a, b) = (a.as_bytes(), b.as_bytes());
21	if a.len() != b.len() {
22	return false;
23	}
24	let mut diff = 0u8;
25	for (x, y) in a.iter().zip(b) {
26	diff \|= x ^ y;
27	}
28	diff == 0
29	}
30
31	#[cfg(test)]
32	mod tests {
33	use super::*;
34
35	#[test]
36	fn ct_eq_matches_only_identical_strings() {
37	assert!(ct_eq("abc", "abc"));
38	assert!(!ct_eq("abc", "abd"));
39	assert!(!ct_eq("abc", "ab"));
40	assert!(!ct_eq("", "x"));
41	assert!(ct_eq("", ""));
42	}
43	}
44