Fix metadata validation

src/core/lib/surface/validate_metadata.c

@@ -73,8 +73,11 @@ grpc_error *grpc_validate_header_key_is_legal(grpc_slice slice) {
       0x00, 0x00, 0x00, 0x00, 0x00, 0x60, 0xff, 0x03, 0x00, 0x00, 0x00,
       0x80, 0xfe, 0xff, 0xff, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
-  if (GRPC_SLICE_LENGTH(slice) == 0 || GRPC_SLICE_START_PTR(slice)[0] == ':') {
+  if (GRPC_SLICE_LENGTH(slice) == 0) {
-    return 0;
+    return GRPC_ERROR_CREATE("Metadata keys cannot be zero length");
+  }
+  if (GRPC_SLICE_START_PTR(slice)[0] == ':') {
+    return GRPC_ERROR_CREATE("Metadata keys cannot start with :");
   }
   return conforms_to(slice, legal_header_bits, "Illegal header key");
 }

test/core/end2end/invalid_call_argument_test.c

@@ -597,6 +597,7 @@ static void test_invalid_initial_metadata_reserved_key() {
 int main(int argc, char **argv) {
   grpc_test_init(argc, argv);
   grpc_init();
+  test_invalid_initial_metadata_reserved_key();
   test_non_null_reserved_on_start_batch();
   test_non_null_reserved_on_op();
   test_send_initial_metadata_more_than_once();
@@ -616,7 +617,6 @@ int main(int argc, char **argv) {
   test_send_server_status_twice();
   test_recv_close_on_server_with_invalid_flags();
   test_recv_close_on_server_twice();
-  test_invalid_initial_metadata_reserved_key();
   grpc_shutdown();
 
   return 0;