@@ -0,0 +1,4 @@
+Fix a crash on DEBUG builds when the HACL* routine used by
+:meth:`hmac.HMAC.update` fails. This only happens for messages larger
+than 4 GiB once the maximum input length of the underlying hash function
+is exceeded. Patch by Bénédikt Tran.
@@ -451,18 +451,18 @@ _hacl_hmac_state_free(HACL_HMAC_state *state)
  *
  * On DEBUG builds, the update() call is verified.
  *
- * Return 0 on success; otherwise, set an exception and return -1 on failure.
+ * Return the HACL* exit code. No exception is set, so that this
+ * can be called without an attached thread state or with a lock held.
 */
-static int
+static hacl_errno_t
 _hacl_hmac_state_update_once(HACL_HMAC_state *state,
                              uint8_t *buf, uint32_t len)
 {
 #ifndef NDEBUG
-    hacl_errno_t code = Hacl_Streaming_HMAC_update(state, buf, len);
-    return _hacl_convert_errno(code);
+    return Hacl_Streaming_HMAC_update(state, buf, len);
 #else
     (void)Hacl_Streaming_HMAC_update(state, buf, len);
-    return 0;
+    return Hacl_Streaming_Types_Success;
 #endif
 }
 
@@ -471,17 +471,20 @@ _hacl_hmac_state_update_once(HACL_HMAC_state *state,
  *
  * On DEBUG builds, each update() call is verified.
  *
- * Return 0 on success; otherwise, set an exception and return -1 on failure.
+ * Return the HACL* exit code. No exception is set, so that this
+ * can be called without an attached thread state or with a lock held.
+ * Use _hacl_convert_errno() afterwards to set an appropriate exception.
  */
-static int
+static hacl_errno_t
 _hacl_hmac_state_update(HACL_HMAC_state *state, uint8_t *buf, Py_ssize_t len)
 {
     assert(len >= 0);
 #ifdef Py_HMAC_SSIZE_LARGER_THAN_UINT32
     while (len > UINT32_MAX_AS_SSIZE_T) {
-        if (_hacl_hmac_state_update_once(state, buf, UINT32_MAX) < 0) {
-            assert(PyErr_Occurred());
-            return -1;
+        hacl_errno_t code = _hacl_hmac_state_update_once(state, buf,
+                                                         UINT32_MAX);
+        if (code != Hacl_Streaming_Types_Success) {
+            return code;
         }
         buf += UINT32_MAX;
         len -= UINT32_MAX;
@@ -786,18 +789,16 @@ _hmac_new_impl(PyObject *module, PyObject *keyobj, PyObject *msgobj,
         GET_BUFFER_VIEW_OR_ERROR(msgobj, &msg, goto error);
         /* Do not use self->mutex here as this is the constructor
          * where it is not yet possible to have concurrent access. */
+        hacl_errno_t code;
         HASHLIB_EXTERNAL_INSTRUCTIONS_UNLOCKED(
             msg.len,
-            rc = _hacl_hmac_state_update(self->state, msg.buf, msg.len)
+            code = _hacl_hmac_state_update(self->state, msg.buf, msg.len)
         );
         PyBuffer_Release(&msg);
-#ifndef NDEBUG
+        rc = _hacl_convert_errno(code);
         if (rc < 0) {
             goto error;
         }
-#else
-        (void)rc;
-#endif
     }
     assert(rc == 0);
     return (PyObject *)self;
@@ -889,15 +890,15 @@ static PyObject *
 _hmac_HMAC_update_impl(HMACObject *self, PyObject *msgobj)
 /*[clinic end generated code: output=962134ada5e55985 input=7c0ea830efb03367]*/
 {
-    int rc = 0;
+    hacl_errno_t code;
     Py_buffer msg;
     GET_BUFFER_VIEW_OR_ERROUT(msgobj, &msg);
     HASHLIB_EXTERNAL_INSTRUCTIONS_LOCKED(
         self, msg.len,
-        rc = _hacl_hmac_state_update(self->state, msg.buf, msg.len)
+        code = _hacl_hmac_state_update(self->state, msg.buf, msg.len)
     );
     PyBuffer_Release(&msg);
-    return rc < 0 ? NULL : Py_None;
+    return _hacl_convert_errno(code) < 0 ? NULL : Py_None;
 }
 
 /*