Mitigate HMAC signature side-channel attack

Thanks to Erwan Legrand
babelouest · Feb 5, 2024 · f9fd9a1 · f9fd9a1
1 parent 1b899d1
commit f9fd9a1
Showing 1 changed file with 4 additions and 1 deletion.
diff --git a/src/jws.c b/src/jws.c
@@ -479,7 +479,10 @@ static int r_jws_verify_sig_hmac(jws_t * jws, jwk_t * jwk) {
   unsigned char * sig = r_jws_sign_hmac(jws, jwk);
   int ret;
 
-  if (sig != NULL && 0 == o_strcmp((const char *)jws->signature_b64url, (const char *)sig)) {
+  if (!o_strnullempty((const char *)jws->signature_b64url) &&
+      !o_strnullempty((const char *)sig) &&
+      o_strlen((const char *)sig) == o_strlen((const char *)jws->signature_b64url) &&
+      0 == gnutls_memcmp(jws->signature_b64url, sig, o_strlen((const char *)sig))) {
     ret = RHN_OK;
   } else {
     ret = RHN_ERROR_INVALID;