F-2381 - https://fenrir.wolfssl.com/finding/2381 - Add test for HMAC truncated signature rejection

Author: aidangarske

tests/pkcs11test.c

@@ -13490,6 +13490,78 @@ static CK_RV test_hmac_sha256_fail(void* args)
 
     return ret;
 }
+
+static CK_RV test_hmac_sha256_truncated_sig(void* args)
+{
+    CK_SESSION_HANDLE session = *(CK_SESSION_HANDLE*)args;
+    CK_RV ret;
+    CK_OBJECT_HANDLE key;
+    byte data[32], sig[32];
+    CK_ULONG dataSz = sizeof(data), sigSz = sizeof(sig);
+    CK_MECHANISM mech;
+    static unsigned char keyData[] = {
+        0x74, 0x9A, 0xBD, 0xAA, 0x2A, 0x52, 0x07, 0x47,
+        0xD6, 0xA6, 0x36, 0xB2, 0x07, 0x32, 0x8E, 0xD0,
+        0xBA, 0x69, 0x7B, 0xC6, 0xC3, 0x44, 0x9E, 0xD4,
+        0x81, 0x48, 0xFD, 0x2D, 0x68, 0xA2, 0x8B, 0x67,
+    };
+
+    memset(data, 9, sizeof(data));
+    mech.mechanism      = CKM_SHA256_HMAC;
+    mech.ulParameterLen = 0;
+    mech.pParameter     = NULL;
+
+    ret = get_generic_key(session, keyData, sizeof(keyData), CK_FALSE, &key);
+
+    /* Sign to get a valid signature */
+    if (ret == CKR_OK) {
+        ret = funcList->C_SignInit(session, &mech, key);
+        CHECK_CKR(ret, "HMAC Sign Init for truncation test");
+    }
+    if (ret == CKR_OK) {
+        ret = funcList->C_Sign(session, data, dataSz, sig, &sigSz);
+        CHECK_CKR(ret, "HMAC Sign for truncation test");
+    }
+
+    /* Verify with truncated signature (1 byte) — must fail */
+    if (ret == CKR_OK) {
+        ret = funcList->C_VerifyInit(session, &mech, key);
+        CHECK_CKR(ret, "HMAC Verify Init truncated");
+    }
+    if (ret == CKR_OK) {
+        ret = funcList->C_Verify(session, data, dataSz, sig, 1);
+        CHECK_CKR_FAIL(ret, CKR_SIGNATURE_INVALID,
+                        "Verify with 1-byte truncated HMAC should fail");
+    }
+
+    /* Verify with truncated signature (sigSz - 1) — must fail */
+    if (ret == CKR_OK) {
+        ret = funcList->C_VerifyInit(session, &mech, key);
+        CHECK_CKR(ret, "HMAC Verify Init truncated-1");
+    }
+    if (ret == CKR_OK) {
+        ret = funcList->C_Verify(session, data, dataSz, sig, sigSz - 1);
+        CHECK_CKR_FAIL(ret, CKR_SIGNATURE_INVALID,
+                        "Verify with sigSz-1 truncated HMAC should fail");
+    }
+
+    /* Verify multi-part with truncated signature */
+    if (ret == CKR_OK) {
+        ret = funcList->C_VerifyInit(session, &mech, key);
+        CHECK_CKR(ret, "HMAC Verify Init for multi-part truncated");
+    }
+    if (ret == CKR_OK) {
+        ret = funcList->C_VerifyUpdate(session, data, dataSz);
+        CHECK_CKR(ret, "HMAC Verify Update for truncated");
+    }
+    if (ret == CKR_OK) {
+        ret = funcList->C_VerifyFinal(session, sig, 1);
+        CHECK_CKR_FAIL(ret, CKR_SIGNATURE_INVALID,
+                        "VerifyFinal with 1-byte truncated HMAC should fail");
+    }
+
+    return ret;
+}
 #endif
 #ifdef WOLFSSL_SHA384
 static CK_RV test_hmac_sha384(void* args)
@@ -17230,6 +17302,7 @@ static TEST_FUNC testFunc[] = {
 #ifndef NO_SHA256
     PKCS11TEST_FUNC_SESS_DECL(test_hmac_sha256),
     PKCS11TEST_FUNC_SESS_DECL(test_hmac_sha256_fail),
+    PKCS11TEST_FUNC_SESS_DECL(test_hmac_sha256_truncated_sig),
 #endif
 #ifdef WOLFSSL_SHA384
     PKCS11TEST_FUNC_SESS_DECL(test_hmac_sha384),