usbredirparser: Fix unserialize on pristine check

As mentioned in the bug below, the user is trying to migrate QEMU and
it is failing on the unserialization of usbredirparser at the target
host. The user does not have USB attached to the VM at all.

I've added a test that shows that serialization is currently broken.
It fails at the 'pristine' check in usbredirparser_unserialize().

This check was added with e37d86c "Skip empty write buffers when
unserializing parser" and restricted further with 186c4c7 "Avoid
memory leak from ill-formatted serialization data"

The issue here is that usbredirparser's initialization sets some
fields and thus it isn't guaranteed to be pristine.

The parser's basic data is:

  | write_buf_count ... : 1
  | write_buf  ........ : 0xbc03e0
  | write_buf_total_size: 80
  | data  ............. : (nil)
  | header_read: ...... : 0
  | type_header_read .. : 0
  | data_read: ........ : 0

The current fix is to to ignore write_buf checks as, again, they are
not guaranteed to be pristine. usbredirparser library should properly
overwrite them when unserializing the data and if there were pending
buffers, they should be freed.

Related: https://bugzilla.redhat.com/show_bug.cgi?id=2096008

Signed-off-by: Victor Toso <victortoso@redhat.com>

3 files changed, 115 insertions, 3 deletions

diff --git a/tests/meson.build b/tests/meson.build
index 0d4397b..2a179c9 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -1,5 +1,6 @@
 tests = [
     'filter',
+    'serializer',
 ]
 
 deps = dependency('glib-2.0')
diff --git a/tests/serializer.c b/tests/serializer.c
new file mode 100644
index 0000000..4bd669e
--- /dev/null
+++ b/tests/serializer.c
@@ -0,0 +1,113 @@
+/*
+ * Copyright 2022 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+*/
+#include "config.h"
+
+#define G_LOG_DOMAIN "serializer"
+#define G_LOG_USE_STRUCTURED
+
+#include "usbredirparser.h"
+
+#include <errno.h>
+#include <locale.h>
+#include <glib.h>
+#include <stdlib.h>
+
+
+static void
+log_cb(void *priv, int level, const char *msg)
+{
+    GLogLevelFlags glog_level;
+
+    switch(level) {
+    case usbredirparser_error:
+        glog_level = G_LOG_LEVEL_ERROR;
+        break;
+    case usbredirparser_warning:
+        glog_level = G_LOG_LEVEL_WARNING;
+        break;
+    case usbredirparser_info:
+        glog_level = G_LOG_LEVEL_INFO;
+        break;
+    case usbredirparser_debug:
+    case usbredirparser_debug_data:
+        glog_level = G_LOG_LEVEL_DEBUG;
+        break;
+    default:
+        g_warn_if_reached();
+        return;
+    }
+    g_log_structured(G_LOG_DOMAIN, glog_level, "MESSAGE", msg);
+}
+
+static struct usbredirparser *
+get_usbredirparser(void)
+{
+    struct usbredirparser *parser = usbredirparser_create();
+    g_assert_nonnull(parser);
+
+    uint32_t caps[USB_REDIR_CAPS_SIZE] = { 0, };
+    /* Typical caps set by usbredirhost */
+    usbredirparser_caps_set_cap(caps, usb_redir_cap_connect_device_version);
+    usbredirparser_caps_set_cap(caps, usb_redir_cap_filter);
+    usbredirparser_caps_set_cap(caps, usb_redir_cap_device_disconnect_ack);
+    usbredirparser_caps_set_cap(caps, usb_redir_cap_ep_info_max_packet_size);
+    usbredirparser_caps_set_cap(caps, usb_redir_cap_64bits_ids);
+    usbredirparser_caps_set_cap(caps, usb_redir_cap_32bits_bulk_length);
+    usbredirparser_caps_set_cap(caps, usb_redir_cap_bulk_receiving);
+#if LIBUSBX_API_VERSION >= 0x01000103
+    usbredirparser_caps_set_cap(caps, usb_redir_cap_bulk_streams);
+#endif
+    int parser_flags = usbredirparser_fl_usb_host;
+
+    parser->log_func = log_cb;
+    usbredirparser_init(parser,
+                        PACKAGE_STRING,
+                        caps,
+                        USB_REDIR_CAPS_SIZE,
+                        parser_flags);
+    return parser;
+}
+
+static void
+simple (gconstpointer user_data)
+{
+    uint8_t *state = NULL;
+    int ret, len = -1;
+
+    struct usbredirparser *source = get_usbredirparser();
+    ret = usbredirparser_serialize(source, &state, &len);
+    g_assert_cmpint(ret, ==, 0);
+
+    struct usbredirparser *target = get_usbredirparser();
+    ret = usbredirparser_unserialize(target, state, len);
+    g_assert_cmpint(ret, ==, 0);
+
+    g_clear_pointer(&state, free);
+    usbredirparser_destroy(source);
+    usbredirparser_destroy(target);
+}
+
+int
+main(int argc, char **argv)
+{
+    setlocale(LC_ALL, "");
+    g_test_init(&argc, &argv, NULL);
+
+    g_test_add_data_func("/serializer/serialize-and-unserialize", NULL, simple);
+
+    return g_test_run();
+}
diff --git a/usbredirparser/usbredirparser.c b/usbredirparser/usbredirparser.c
index cd1136b..a5dd0e7 100644
--- a/usbredirparser/usbredirparser.c
+++ b/usbredirparser/usbredirparser.c
@@ -1816,9 +1816,7 @@ int usbredirparser_unserialize(struct usbredirparser *parser_pub,
         return -1;
     }
 
-    if (!(parser->write_buf_count == 0 && parser->write_buf == NULL &&
-          parser->write_buf_total_size == 0 &&
-          parser->data == NULL && parser->header_read == 0 &&
+    if (!(parser->data == NULL && parser->header_read == 0 &&
           parser->type_header_read == 0 && parser->data_read == 0)) {
         ERROR("unserialization must use a pristine parser");
         usbredirparser_assert_invariants(parser);