From 33b9338fb03ff58960f4a2df339314846a3ae6e5 Mon Sep 17 00:00:00 2001
From: Benjamin Otte <otte.benjamin@googlemail.com>
Date: Sat, 16 Nov 2024 07:46:24 +0000
Subject: [PATCH] converteroutputstream: Raise error for data at end

When a conversion is finished, the code would return 0 from its write
vfunc. This is disallowed by the API of g_output_stream_write() and
causes g_output_stream_splice() as used by g_converter_convert_bytes()
to turn into an infinite loop.

Instead, raise a G_IO_ERROR_MESSAGE_TOO_LARGE error so that the calling
code can decide how to deal with it.

Testcase included.

Closes #3532
---
 gio/gconverteroutputstream.c |  6 +++++-
 gio/tests/converter.c        | 41 ++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/gio/gconverteroutputstream.c b/gio/gconverteroutputstream.c
index 1877b0e4e..37dbadee4 100644
--- a/gio/gconverteroutputstream.c
+++ b/gio/gconverteroutputstream.c
@@ -422,7 +422,11 @@ write_internal (GOutputStream  *stream,
     return -1;
 
   if (priv->finished)
-    return 0;
+    {
+      g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_MESSAGE_TOO_LARGE,
+                           _("Unexpected data after end of conversion"));
+      return -1;
+    }
 
   /* Convert as much as possible */
   if (buffer_data_size (&priv->output_buffer) > 0)
diff --git a/gio/tests/converter.c b/gio/tests/converter.c
index 3795a5d09..db7e0c3af 100644
--- a/gio/tests/converter.c
+++ b/gio/tests/converter.c
@@ -23,6 +23,46 @@
 #include <stdlib.h>
 #include <string.h>
 
+static void
+test_extra_bytes_at_end (void)
+{
+  char data[1024];
+  gsize size;
+  GBytes *bytes;
+  GConverter *converter;
+  GError *error = NULL;
+  GBytes *result;
+
+  /* Create some simple data to encode */
+  data[0] = 0;
+  bytes = g_bytes_new_static (data, 1);
+
+  /* encode the data */
+  converter = G_CONVERTER (g_zlib_compressor_new (G_ZLIB_COMPRESSOR_FORMAT_GZIP, 9));
+  result = g_converter_convert_bytes (converter, bytes, &error);
+  g_assert_no_error (error);
+  g_assert_nonnull (result);
+  g_bytes_unref (bytes);
+  g_clear_object (&converter);
+
+  /* Append a 0 byte to the encoded data */
+  size = g_bytes_get_size (result);
+  g_assert_cmpuint (size, <, G_N_ELEMENTS (data)); /* just to be very sure */
+  memcpy (data, g_bytes_get_data (result, NULL), size);
+  data[size] = 0;
+  bytes = g_bytes_new_static (data, size + 1);
+  g_bytes_unref (result);
+
+  /* Decompress the just compressed bytes with the extra 0 */
+  converter = G_CONVERTER (g_zlib_decompressor_new (G_ZLIB_COMPRESSOR_FORMAT_GZIP));
+  result = g_converter_convert_bytes (converter, bytes, &error);
+  g_assert_error (error, G_IO_ERROR, G_IO_ERROR_MESSAGE_TOO_LARGE);
+  g_assert_null (result);
+  g_clear_error (&error);
+
+  g_object_unref (converter);
+  g_bytes_unref (bytes);
+}
 
 static void
 test_convert_bytes (void)
@@ -63,6 +103,7 @@ main (int   argc,
   g_test_init (&argc, &argv, NULL);
 
   g_test_add_func ("/converter/bytes", test_convert_bytes);
+  g_test_add_func ("/converter/extra-bytes-at-end", test_extra_bytes_at_end);
 
   return g_test_run();
 }