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gvariant-parser: Reject deeply-nested typedecls in text form variants

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Return `G_VARIANT_PARSE_ERROR_RECURSION` from `g_variant_parse()` if a
typedecl is found within a text-form variant which would cause any part
of the variant to exceed the maximum allowed recursion/nesting depth.

This fixes an oversight when `G_VARIANT_MAX_RECURSION_DEPTH` was
implemented, which allowed typedecls to effectively multiply the size of
an array if `g_variant_parse()` was parsing a text-form variant without
a top-level concrete type specified.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

Fixes: #2782
oss-fuzz#49462
This commit is contained in:
Philip Withnall 2022-10-18 12:43:22 +01:00
parent 9164fdcbbb
commit 3e313438f1
2 changed files with 41 additions and 0 deletions
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10
glib/gvariant-parser.c
View File

@ -2231,6 +2231,16 @@ typedecl_parse (TokenStream *stream,
return NULL;
}
if (g_variant_type_string_get_depth_ (token + 1) > max_depth)
{
token_stream_set_error (stream, error, TRUE,
G_VARIANT_PARSE_ERROR_RECURSION,
"type declaration recurses too deeply");
g_free (token);
return NULL;
}
type = g_variant_type_new (token + 1);
if (!g_variant_type_is_definite (type))

31
glib/tests/gvariant.c
View File

@ -4189,6 +4189,36 @@ test_parser_recursion (void)
g_free (silly_dict);
}
/* Test that #GVariants which recurse too deeply through use of typedecls are
* rejected. This is a sneaky way to multiply the number of objects in a text
* representation of a #GVariant without making the text-form proportionately
* long. It uses a typedecl to nest one of the elements deeply within nested
* maybes, while keeping all the other elements un-nested in the text form. It
* relies on g_variant_parse() not being provided with a concrete type for the
* top-level #GVariant. */
static void
test_parser_recursion_typedecls (void)
{
GVariant *value = NULL;
GError *local_error = NULL;
const guint recursion_depth = G_VARIANT_MAX_RECURSION_DEPTH - 1;
gchar *silly_type = g_malloc0 (recursion_depth + 2 /* trailing `u` and then nul */);
gchar *silly_array = NULL;
gsize i;
for (i = 0; i < recursion_depth; i++)
silly_type[i] = 'm';
silly_type[recursion_depth] = 'u';
silly_array = g_strdup_printf ("[1,2,3,@%s 0]", silly_type);
value = g_variant_parse (NULL, silly_array, NULL, NULL, &local_error);
g_assert_error (local_error, G_VARIANT_PARSE_ERROR, G_VARIANT_PARSE_ERROR_RECURSION);
g_assert_null (value);
g_error_free (local_error);
g_free (silly_array);
}
static void
test_parse_bad_format_char (void)
{
@ -5163,6 +5193,7 @@ main (int argc, char **argv)
g_test_add_func ("/gvariant/parser", test_parses);
g_test_add_func ("/gvariant/parser/integer-bounds", test_parser_integer_bounds);
g_test_add_func ("/gvariant/parser/recursion", test_parser_recursion);
g_test_add_func ("/gvariant/parser/recursion/typedecls", test_parser_recursion_typedecls);
g_test_add_func ("/gvariant/parse-failures", test_parse_failures);
g_test_add_func ("/gvariant/parse-positional", test_parse_positional);
g_test_add_func ("/gvariant/parse/subprocess/bad-format-char", test_parse_bad_format_char);