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Fix: add depth check to prevent stack overflow in cJSON_Utils (#995) #1064

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Fix: add depth check to prevent stack overflow in cJSON_Utils (#995) #1064

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50 changes: 37 additions & 13 deletions cJSON_Utils.c
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Original file line number Diff line number Diff line change
Expand Up @@ -601,8 +601,13 @@ static void sort_object(cJSON * const object, const cJSON_bool case_sensitive)
object->child = sort_list(object->child, case_sensitive);
}

static cJSON_bool compare_json(cJSON *a, cJSON *b, const cJSON_bool case_sensitive)
static cJSON_bool compare_json(cJSON *a, cJSON *b, size_t depth, const cJSON_bool case_sensitive)
{
/* Prevent stack overflow from deeply nested JSON comparison (#995) */
if (depth >= CJSON_NESTING_LIMIT)
{
return false;
}
if ((a == NULL) || (b == NULL) || ((a->type & 0xFF) != (b->type & 0xFF)))
{
/* mismatched type. */
Expand Down Expand Up @@ -635,7 +640,7 @@ static cJSON_bool compare_json(cJSON *a, cJSON *b, const cJSON_bool case_sensiti
case cJSON_Array:
for ((void)(a = a->child), b = b->child; (a != NULL) && (b != NULL); (void)(a = a->next), b = b->next)
{
cJSON_bool identical = compare_json(a, b, case_sensitive);
cJSON_bool identical = compare_json(a, b, depth + 1, case_sensitive);
if (!identical)
{
return false;
Expand Down Expand Up @@ -664,7 +669,7 @@ static cJSON_bool compare_json(cJSON *a, cJSON *b, const cJSON_bool case_sensiti
/* missing member */
return false;
}
identical = compare_json(a, b, case_sensitive);
identical = compare_json(a, b, depth + 1, case_sensitive);
if (!identical)
{
return false;
Expand Down Expand Up @@ -831,7 +836,7 @@ static int apply_patch(cJSON *object, const cJSON *patch, const cJSON_bool case_
else if (opcode == TEST)
{
/* compare value: {...} with the given path */
status = !compare_json(get_item_from_pointer(object, path->valuestring, case_sensitive), get_object_item(patch, "value", case_sensitive), case_sensitive);
status = !compare_json(get_item_from_pointer(object, path->valuestring, case_sensitive), get_object_item(patch, "value", case_sensitive), 0, case_sensitive);
goto cleanup;
}

Expand Down Expand Up @@ -1318,10 +1323,17 @@ CJSON_PUBLIC(void) cJSONUtils_SortObjectCaseSensitive(cJSON * const object)
sort_object(object, true);
}

static cJSON *merge_patch(cJSON *target, const cJSON * const patch, const cJSON_bool case_sensitive)
static cJSON *merge_patch(cJSON *target, const cJSON * const patch, size_t depth, const cJSON_bool case_sensitive)
{
cJSON *patch_child = NULL;

/* Prevent stack overflow from deeply nested JSON merge patch (#995) */
if (depth >= CJSON_NESTING_LIMIT)
{
cJSON_Delete(target);
return NULL;
}

if (!cJSON_IsObject(patch))
{
/* scalar value, array or NULL, just duplicate */
Expand Down Expand Up @@ -1364,7 +1376,7 @@ static cJSON *merge_patch(cJSON *target, const cJSON * const patch, const cJSON_
replace_me = cJSON_DetachItemFromObject(target, patch_child->string);
}

replacement = merge_patch(replace_me, patch_child, case_sensitive);
replacement = merge_patch(replace_me, patch_child, depth + 1, case_sensitive);
if (replacement == NULL)
{
cJSON_Delete(target);
Expand All @@ -1380,19 +1392,25 @@ static cJSON *merge_patch(cJSON *target, const cJSON * const patch, const cJSON_

CJSON_PUBLIC(cJSON *) cJSONUtils_MergePatch(cJSON *target, const cJSON * const patch)
{
return merge_patch(target, patch, false);
return merge_patch(target, patch, 0, false);
}

CJSON_PUBLIC(cJSON *) cJSONUtils_MergePatchCaseSensitive(cJSON *target, const cJSON * const patch)
{
return merge_patch(target, patch, true);
return merge_patch(target, patch, 0, true);
}

static cJSON *generate_merge_patch(cJSON * const from, cJSON * const to, const cJSON_bool case_sensitive)
static cJSON *generate_merge_patch(cJSON * const from, cJSON * const to, size_t depth, const cJSON_bool case_sensitive)
{
cJSON *from_child = NULL;
cJSON *to_child = NULL;
cJSON *patch = NULL;
cJSON *sub_patch = NULL;
/* Prevent stack overflow from deeply nested JSON generate merge patch (#995) */
if (depth >= CJSON_NESTING_LIMIT)
{
return NULL;
}
if (to == NULL)
{
/* patch to delete everything */
Expand Down Expand Up @@ -1449,10 +1467,16 @@ static cJSON *generate_merge_patch(cJSON * const from, cJSON * const to, const c
else
{
/* object key exists in both objects */
if (!compare_json(from_child, to_child, case_sensitive))
if (!compare_json(from_child, to_child, 0, case_sensitive))
{
sub_patch = generate_merge_patch(from_child, to_child, depth + 1, case_sensitive);
if (sub_patch == NULL)
{
cJSON_Delete(patch);
return NULL;
}
/* not identical --> generate a patch */
cJSON_AddItemToObject(patch, to_child->string, cJSONUtils_GenerateMergePatch(from_child, to_child));
cJSON_AddItemToObject(patch, to_child->string, sub_patch);
}

/* next key in the object */
Expand All @@ -1472,10 +1496,10 @@ static cJSON *generate_merge_patch(cJSON * const from, cJSON * const to, const c

CJSON_PUBLIC(cJSON *) cJSONUtils_GenerateMergePatch(cJSON * const from, cJSON * const to)
{
return generate_merge_patch(from, to, false);
return generate_merge_patch(from, to, 0, false);
}

CJSON_PUBLIC(cJSON *) cJSONUtils_GenerateMergePatchCaseSensitive(cJSON * const from, cJSON * const to)
{
return generate_merge_patch(from, to, true);
return generate_merge_patch(from, to, 0, true);
}
50 changes: 50 additions & 0 deletions tests/misc_utils_tests.c
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,25 @@
#include "common.h"
#include "../cJSON_Utils.h"

#define TEST_NESTING_LIMIT 2000

static cJSON *create_deeply_nested_object(size_t depth)
{
cJSON *root = cJSON_CreateObject();
cJSON *curr = root;
cJSON *next = NULL;
size_t i = 0;

for (i = 0; (i < depth) && (curr != NULL); ++i)
{
next = cJSON_CreateObject();
cJSON_AddItemToObject(curr, "a", next);
curr = next;
}

return root;
}

static void cjson_utils_functions_shouldnt_crash_with_null_pointers(void)
{
cJSON *item = cJSON_CreateString("item");
Expand Down Expand Up @@ -70,11 +89,42 @@ static void cjson_utils_functions_shouldnt_crash_with_null_pointers(void)
cJSON_Delete(item);
}

static void cjson_utils_merge_patch_should_not_overflow_stack_on_deep_nesting(void)
{
cJSON *target = cJSON_CreateObject();
cJSON *patch = create_deeply_nested_object(TEST_NESTING_LIMIT);

TEST_ASSERT_NOT_NULL(target);
TEST_ASSERT_NOT_NULL(patch);

TEST_ASSERT_NULL(cJSONUtils_MergePatch(target, patch));

cJSON_Delete(patch);
}

static void cjson_utils_generate_merge_patch_should_not_overflow_stack_on_deep_nesting(void)
{
cJSON *from = create_deeply_nested_object(TEST_NESTING_LIMIT);
cJSON *to = create_deeply_nested_object(TEST_NESTING_LIMIT);

TEST_ASSERT_NOT_NULL(from);
TEST_ASSERT_NOT_NULL(to);

cJSON_AddNumberToObject(to, "diff", 123);

TEST_ASSERT_NULL(cJSONUtils_GenerateMergePatch(from, to));

cJSON_Delete(from);
cJSON_Delete(to);
}

int main(void)
{
UNITY_BEGIN();

RUN_TEST(cjson_utils_functions_shouldnt_crash_with_null_pointers);
RUN_TEST(cjson_utils_merge_patch_should_not_overflow_stack_on_deep_nesting);
RUN_TEST(cjson_utils_generate_merge_patch_should_not_overflow_stack_on_deep_nesting);

return UNITY_END();
}