refactor(proto): consolidate tests

crates/irtt-proto/tests/hmac.rs

@@ -0,0 +1,61 @@
+use irtt_proto::{compute_hmac, compute_hmac_in_place, verify_hmac, ProtoError};
+
+fn captured_open() -> Vec<u8> {
+    // Captured vector 6; provenance and independently checked digest are in
+    // docs/protocol/test-vectors/README.md. This is an oracle for the primitive.
+    "14 a7 5b 09 ff 90 16 a7 aa 53 78 16 9e c3 a2 d5 54 dc 30 36
+     01 02 02 80 d0 ac f3 0e 03 80 a8 d6 b9 07 05 06 06 06 07 06"
+        .split_whitespace()
+        .map(|byte| u8::from_str_radix(byte, 16).unwrap())
+        .collect()
+}
+
+#[test]
+fn computing_hmac_ignores_existing_digest_and_only_replaces_its_field() {
+    let expected = captured_open();
+    let mut packet = expected.clone();
+    packet[4..20].fill(0xa5);
+    let before = packet.clone();
+    assert_eq!(
+        compute_hmac(b"testkey", &packet, 4).unwrap().as_slice(),
+        &expected[4..20]
+    );
+    assert_eq!(packet, before);
+    compute_hmac_in_place(b"testkey", &mut packet, 4).unwrap();
+    assert_eq!(packet, expected);
+}
+
+#[test]
+fn verification_rejects_wrong_key_and_modified_authenticated_bytes() {
+    let packet = captured_open();
+    verify_hmac(b"testkey", &packet, 4).unwrap();
+    assert_eq!(verify_hmac(b"wrong", &packet, 4), Err(ProtoError::BadHmac));
+    for offset in [0, 4, 21, packet.len() - 1] {
+        let mut modified = packet.clone();
+        modified[offset] ^= 1;
+        assert_eq!(
+            verify_hmac(b"testkey", &modified, 4),
+            Err(ProtoError::BadHmac)
+        );
+    }
+}
+
+#[test]
+fn incomplete_or_out_of_bounds_digest_fields_are_rejected_without_mutation() {
+    for offset in [5, 20, 21, usize::MAX] {
+        let mut packet = vec![0xa5; 20];
+        assert_eq!(
+            compute_hmac(b"key", &packet, offset),
+            Err(ProtoError::InvalidHmacOffset)
+        );
+        assert_eq!(
+            verify_hmac(b"key", &packet, offset),
+            Err(ProtoError::InvalidHmacOffset)
+        );
+        assert_eq!(
+            compute_hmac_in_place(b"key", &mut packet, offset),
+            Err(ProtoError::InvalidHmacOffset)
+        );
+        assert_eq!(packet, [0xa5; 20]);
+    }
+}