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Introduce a recursion limit for YAML documents #645

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3f5477d
Introduce a recursion limit for YAML documents
ppisar Sep 8, 2026
a9db6f9
Apply a recursion limit to mmd_parse_xmd()
ppisar Sep 11, 2026
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1 change: 1 addition & 0 deletions meson.build
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Original file line number Diff line number Diff line change
Expand Up @@ -228,5 +228,6 @@ summary({'Custom Python': get_option('python_name'),
'Python 3 Support': get_option('with_py3'),
'Skip Introspection': get_option('skip_introspection'),
'Accept overflowed buildorder': get_option('accept_overflowed_buildorder'),
'Recursion limit': get_option('recursion_limit'),
'Test Installed Library': get_option('test_installed_lib'),
}, section: 'Build Configuration')
3 changes: 3 additions & 0 deletions meson_options.txt
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Expand Up @@ -23,6 +23,9 @@ option('libmagic', type : 'feature', value : 'auto',
option('python_name', type : 'string',
description : 'The name of the Python 3 interpreter to use for generating Python bindings and running tests. If left blank, it defaults to the version of Python 3 being used to run meson.')

option('recursion_limit', type : 'integer', min : 16, value : 64,
description : 'Maximal depth of accepted recusive structures, like mappings in YAML documents.')

option('rpmio', type : 'feature', value : 'enabled',
description : 'Use the rpmio library to automatically decompress gzip, bzip2 and xz YAML streams.')

Expand Down
6 changes: 4 additions & 2 deletions modulemd/include/private/modulemd-yaml.h
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Expand Up @@ -913,6 +913,7 @@ mmd_variant_from_scalar (const gchar *scalar);
/**
* mmd_variant_from_mapping:
* @parser: (inout): A YAML parser positioned just after a `MAPPING_START`
* @depth: Current YAML depth in the XMD document
* @error: (out): A #GError that will return the reason for failing to parse.
*
* Returns: (transfer full): A new, floating #GVariant representing a hash
Expand All @@ -921,12 +922,13 @@ mmd_variant_from_scalar (const gchar *scalar);
* Since: 2.0
*/
GVariant *
mmd_variant_from_mapping (yaml_parser_t *parser, GError **error);
mmd_variant_from_mapping (yaml_parser_t *parser, int depth, GError **error);


/**
* mmd_variant_from_sequence:
* @parser: (inout): A YAML parser positioned just after a `SEQUENCE_START`
* @depth: Current YAML depth in the XMD document
* @error: (out): A #GError that will return the reason for failing to parse.
*
* Returns: (transfer full): A new, floating #GVariant representing a list of
Expand All @@ -935,7 +937,7 @@ mmd_variant_from_mapping (yaml_parser_t *parser, GError **error);
* Since: 2.0
*/
GVariant *
mmd_variant_from_sequence (yaml_parser_t *parser, GError **error);
mmd_variant_from_sequence (yaml_parser_t *parser, int depth, GError **error);


/**
Expand Down
3 changes: 3 additions & 0 deletions modulemd/meson.build
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Expand Up @@ -16,6 +16,7 @@ skip_introspection = get_option('skip_introspection')
verbose_tests = get_option('verbose_tests')
accept_overflowed_buildorder = get_option('accept_overflowed_buildorder')
clang_simple_version_script = find_program ('clang_simple_version.sh')
recursion_limit = get_option('recursion_limit')


# -- Library -- #
Expand Down Expand Up @@ -147,6 +148,7 @@ cdata.set('HAVE_EXTEND_AND_STEAL', has_extend_and_steal)
cdata.set('HAVE_G_SPAWN_CHECK_WAIT_STATUS', has_g_spawn_check_wait_status)
cdata.set('HAVE_G_TEST_SUBPROCESS_DEFAULT', has_g_test_subprocess_default)
cdata.set('HAVE_OVERFLOWED_BUILDORDER', accept_overflowed_buildorder)
cdata.set('LIBMODULEMD_RECURSION_LIMIT', recursion_limit)
configure_file(
output : 'config.h',
configuration : cdata
Expand Down Expand Up @@ -355,6 +357,7 @@ c_tests = {
'defaults' : [ 'tests/test-modulemd-defaults.c' ],
'defaultsv1' : [ 'tests/test-modulemd-defaults-v1.c' ],
'dependencies' : [ 'tests/test-modulemd-dependencies.c' ],
'limits' : [ 'tests/test-modulemd-limits.c' ],
'module' : [ 'tests/test-modulemd-module.c' ],
'module_index' : [ 'tests/test-modulemd-moduleindex.c' ],
'module_index_merger' : [ 'tests/test-modulemd-merger.c' ],
Expand Down
72 changes: 64 additions & 8 deletions modulemd/modulemd-yaml-util.c
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Expand Up @@ -19,6 +19,7 @@
#include <errno.h>
#include <glib.h>
#include <inttypes.h>
#include <limits.h>
#include <yaml.h>


Expand Down Expand Up @@ -1085,7 +1086,14 @@
{
return FALSE;
}
depth++;
if (depth == INT_MAX || ++depth > LIBMODULEMD_RECURSION_LIMIT)

Check failure on line 1089 in modulemd/modulemd-yaml-util.c

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SonarQubeCloud / SonarCloud Code Analysis

Remove any side effects from right hand operands of logical || operator. 


See more on https://sonarcloud.io/project/issues?id=fedora-modularity_libmodulemd&issues=AaGh6PY-Wx9ajDfpIAzi&open=AaGh6PY-Wx9ajDfpIAzi&pullRequest=645
{
MMD_YAML_ERROR_EVENT_EXIT_BOOL (
error,
event,
"YAML document depth limit %d exceeded.",
LIBMODULEMD_RECURSION_LIMIT);
}
break;

case YAML_SCALAR_EVENT:
Expand Down Expand Up @@ -1488,7 +1496,7 @@


GVariant *
mmd_variant_from_mapping (yaml_parser_t *parser, GError **error)
mmd_variant_from_mapping (yaml_parser_t *parser, int depth, GError **error)

Check failure on line 1499 in modulemd/modulemd-yaml-util.c

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SonarQubeCloud / SonarCloud Code Analysis

Refactor this function to reduce its Cognitive Complexity from 28 to the 25 allowed. 


See more on https://sonarcloud.io/project/issues?id=fedora-modularity_libmodulemd&issues=AaGh6PY-Wx9ajDfpIAzj&open=AaGh6PY-Wx9ajDfpIAzj&pullRequest=645
{
MODULEMD_INIT_TRACE ();
gboolean done = FALSE;
Expand Down Expand Up @@ -1532,7 +1540,16 @@
break;

case YAML_MAPPING_START_EVENT:
value = mmd_variant_from_mapping (parser, &nested_error);
if (depth == INT_MAX || depth + 1 > LIBMODULEMD_RECURSION_LIMIT)

Check failure on line 1543 in modulemd/modulemd-yaml-util.c

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SonarQubeCloud / SonarCloud Code Analysis

Refactor this code to not nest more than 3 if|for|do|while|switch statements. 


See more on https://sonarcloud.io/project/issues?id=fedora-modularity_libmodulemd&issues=AaGh6PY-Wx9ajDfpIAzk&open=AaGh6PY-Wx9ajDfpIAzk&pullRequest=645
{
MMD_YAML_ERROR_EVENT_EXIT (
error,
event,
"XMD YAML document depth limit %d exceeded.",
LIBMODULEMD_RECURSION_LIMIT);
}
value =
mmd_variant_from_mapping (parser, depth + 1, &nested_error);
if (!value)
{
g_propagate_error (error, g_steal_pointer (&nested_error));
Expand All @@ -1541,7 +1558,16 @@
break;

case YAML_SEQUENCE_START_EVENT:
value = mmd_variant_from_sequence (parser, &nested_error);
if (depth == INT_MAX || depth + 1 > LIBMODULEMD_RECURSION_LIMIT)

Check failure on line 1561 in modulemd/modulemd-yaml-util.c

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SonarQubeCloud / SonarCloud Code Analysis

Refactor this code to not nest more than 3 if|for|do|while|switch statements. 


See more on https://sonarcloud.io/project/issues?id=fedora-modularity_libmodulemd&issues=AaGh6PY-Wx9ajDfpIAzl&open=AaGh6PY-Wx9ajDfpIAzl&pullRequest=645
{
MMD_YAML_ERROR_EVENT_EXIT (
error,
event,
"XMD YAML document depth limit %d exceeded.",
LIBMODULEMD_RECURSION_LIMIT);
}
value =
mmd_variant_from_sequence (parser, depth + 1, &nested_error);
if (!value)
{
g_propagate_error (error, g_steal_pointer (&nested_error));
Expand Down Expand Up @@ -1582,7 +1608,7 @@


GVariant *
mmd_variant_from_sequence (yaml_parser_t *parser, GError **error)
mmd_variant_from_sequence (yaml_parser_t *parser, int depth, GError **error)
{
MODULEMD_INIT_TRACE ();
gboolean done = FALSE;
Expand Down Expand Up @@ -1617,7 +1643,15 @@
break;

case YAML_MAPPING_START_EVENT:
value = mmd_variant_from_mapping (parser, &nested_error);
if (depth == INT_MAX || depth + 1 > LIBMODULEMD_RECURSION_LIMIT)
{
MMD_YAML_ERROR_EVENT_EXIT (
error,
event,
"XMD YAML document depth limit %d exceeded.",
LIBMODULEMD_RECURSION_LIMIT);
}
value = mmd_variant_from_mapping (parser, depth + 1, &nested_error);
if (!value)
{
g_propagate_error (error, g_steal_pointer (&nested_error));
Expand All @@ -1626,7 +1660,15 @@
break;

case YAML_SEQUENCE_START_EVENT:
value = mmd_variant_from_sequence (parser, &nested_error);
if (depth == INT_MAX || depth + 1 > LIBMODULEMD_RECURSION_LIMIT)
{
MMD_YAML_ERROR_EVENT_EXIT (
error,
event,
"XMD YAML document depth limit %d exceeded.",
LIBMODULEMD_RECURSION_LIMIT);
}
value = mmd_variant_from_sequence (parser, depth + 1, &nested_error);
if (!value)
{
g_propagate_error (error, g_steal_pointer (&nested_error));
Expand Down Expand Up @@ -1677,6 +1719,7 @@
MMD_INIT_YAML_EVENT (event);
GVariant *variant = NULL;
g_autoptr (GError) nested_error = NULL;
int depth = 0;

g_return_val_if_fail (error == NULL || *error == NULL, FALSE);

Expand All @@ -1694,7 +1737,20 @@
break;

case YAML_MAPPING_START_EVENT:
variant = mmd_variant_from_mapping (parser, &nested_error);
if (depth == INT_MAX || depth + 1 > LIBMODULEMD_RECURSION_LIMIT)
{
MMD_YAML_ERROR_EVENT_EXIT (
error,
event,
"XMD YAML document depth limit %d exceeded.",
LIBMODULEMD_RECURSION_LIMIT);
}
variant = mmd_variant_from_mapping (parser, depth + 1, &nested_error);
if (!variant)
{
g_propagate_error (error, g_steal_pointer (&nested_error));
return NULL;
}
break;

default:
Expand Down
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