[glib/glib-2-32] GVariant: fix string validation

[Matthias Clasen <matthiasc src gnome org>]

commit 3f0ed5c26b6adbda0d5384c897a3b3d6e9858536
Author: Ryan Lortie <desrt desrt ca>
Date:   Mon Jul 9 12:43:50 2012 -0400

    GVariant: fix string validation
    
    String validation was done by checking if the string was valid utf8 and
    ensuring that the first non-utf8 character was the last character (ie:
    the nul terminator).
    
    No check was actually done to make sure that this byte actually
    contained a nul, however, so it was possible that you could have a
    string like "hello\xff" with length 6 that would correctly validate.
    
    Fix that, and test it.

 glib/gvariant-serialiser.c |   11 ++++++++++-
 glib/tests/gvariant.c      |    1 +
 2 files changed, 11 insertions(+), 1 deletions(-)
---
diff --git a/glib/gvariant-serialiser.c b/glib/gvariant-serialiser.c
index d4b668b..4ee6c72 100644
--- a/glib/gvariant-serialiser.c
+++ b/glib/gvariant-serialiser.c
@@ -1593,11 +1593,20 @@ gboolean
 g_variant_serialiser_is_string (gconstpointer data,
                                 gsize         size)
 {
+  const gchar *expected_end;
   const gchar *end;
 
+  if (size == 0)
+    return FALSE;
+
+  expected_end = ((gchar *) data) + size - 1;
+
+  if (*expected_end != '\0')
+    return FALSE;
+
   g_utf8_validate (data, size, &end);
 
-  return data == end - (size - 1);
+  return end == expected_end;
 }
 
 /* < private >
diff --git a/glib/tests/gvariant.c b/glib/tests/gvariant.c
index d3d8aa2..a6bef23 100644
--- a/glib/tests/gvariant.c
+++ b/glib/tests/gvariant.c
@@ -1821,6 +1821,7 @@ test_strings (void)
     { is_nval,     13, "hello world\0" },
     { is_nval,     13, "hello\0world!" },
     { is_nval,     12, "hello world!" },
+    { is_nval,     13, "hello world!\xff" },
 
     { is_objpath,   2, "/" },
     { is_objpath,   3, "/a" },