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Fix #881, check overlap before calling strcpy in cJSON_SetValuestring #885

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merged 4 commits into from
Aug 30, 2024
Merged

Fix #881, check overlap before calling strcpy in cJSON_SetValuestring #885

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d3b2452
fix #881, check overlap before calling strcpy in cJSON_SetValuestring
vwvw Aug 23, 2024
193cd6a
CJSON_SetValuestring: add test for overlapping string
vwvw Aug 25, 2024
f0c6455
CJSON_SetValuestring: better test for overlapping string
vwvw Aug 25, 2024
3f09bd6
Free mem in cjson_set_valuestring_should_return_null_if_strings_overlap
vwvw Aug 26, 2024
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13 changes: 12 additions & 1 deletion cJSON.c
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Original file line number Diff line number Diff line change
Expand Up @@ -403,6 +403,8 @@ CJSON_PUBLIC(double) cJSON_SetNumberHelper(cJSON *object, double number)
CJSON_PUBLIC(char*) cJSON_SetValuestring(cJSON *object, const char *valuestring)
{
char *copy = NULL;
size_t v1_len;
size_t v2_len;
/* if object's type is not cJSON_String or is cJSON_IsReference, it should not set valuestring */
if ((object == NULL) || !(object->type & cJSON_String) || (object->type & cJSON_IsReference))
{
Expand All @@ -413,8 +415,17 @@ CJSON_PUBLIC(char*) cJSON_SetValuestring(cJSON *object, const char *valuestring)
{
return NULL;
}
if (strlen(valuestring) <= strlen(object->valuestring))

v1_len = strlen(valuestring);
v2_len = strlen(object->valuestring);

if (v1_len <= v2_len)
{
/* strcpy does not handle overlapping string: [X1, X2] [Y1, Y2] => X2 < Y1 or Y2 < X1 */
if (!( valuestring + v1_len < object->valuestring || object->valuestring + v2_len < valuestring ))
{
return NULL;
}
strcpy(object->valuestring, valuestring);
return object->valuestring;
}
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19 changes: 19 additions & 0 deletions tests/misc_tests.c
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Original file line number Diff line number Diff line change
Expand Up @@ -456,6 +456,24 @@ static void cjson_functions_should_not_crash_with_null_pointers(void)
cJSON_Delete(item);
}

static void cjson_set_valuestring_should_return_null_if_strings_overlap(void)
{
cJSON *obj;
char* str;
char* str2;

obj = cJSON_Parse("\"foo0z\"");

str = cJSON_SetValuestring(obj, "abcde");
str += 1;
/* The string passed to strcpy overlap which is not allowed.*/
str2 = cJSON_SetValuestring(obj, str);
/* If it overlaps, the string will be messed up.*/
TEST_ASSERT_TRUE(strcmp(str, "bcde") == 0);
TEST_ASSERT_NULL(str2);
cJSON_Delete(obj);
}

static void *CJSON_CDECL failing_realloc(void *pointer, size_t size)
{
(void)size;
Expand Down Expand Up @@ -749,6 +767,7 @@ int CJSON_CDECL main(void)
RUN_TEST(cjson_replace_item_via_pointer_should_replace_items);
RUN_TEST(cjson_replace_item_in_object_should_preserve_name);
RUN_TEST(cjson_functions_should_not_crash_with_null_pointers);
RUN_TEST(cjson_set_valuestring_should_return_null_if_strings_overlap);
RUN_TEST(ensure_should_fail_on_failed_realloc);
RUN_TEST(skip_utf8_bom_should_skip_bom);
RUN_TEST(skip_utf8_bom_should_not_skip_bom_if_not_at_beginning);
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