allocate memory for the temporary buffer

Allocate memory for the temporary buffer when paring numbers.
This fixes CVE-2023-26819

Author: PeterAlfredLee

cJSON.c

@@ -308,9 +308,11 @@ static cJSON_bool parse_number(cJSON * const item, parse_buffer * const input_bu
 {
     double number = 0;
     unsigned char *after_end = NULL;
-    unsigned char number_c_string[64];
+    unsigned char *number_c_string;
     unsigned char decimal_point = get_decimal_point();
     size_t i = 0;
+    size_t number_string_length = 0;
+    cJSON_bool has_decimal_point = false;
 
     if ((input_buffer == NULL) || (input_buffer->content == NULL))
     {
@@ -320,7 +322,7 @@ static cJSON_bool parse_number(cJSON * const item, parse_buffer * const input_bu
     /* copy the number into a temporary buffer and replace '.' with the decimal point
      * of the current locale (for strtod)
      * This also takes care of '\0' not necessarily being available for marking the end of the input */
-    for (i = 0; (i < (sizeof(number_c_string) - 1)) && can_access_at_index(input_buffer, i); i++)
+    for (i = 0; can_access_at_index(input_buffer, i); i++)
     {
         switch (buffer_at_offset(input_buffer)[i])
         {
@@ -338,23 +340,46 @@ static cJSON_bool parse_number(cJSON * const item, parse_buffer * const input_bu
             case '-':
             case 'e':
             case 'E':
-                number_c_string[i] = buffer_at_offset(input_buffer)[i];
+                number_string_length++;
                 break;
 
             case '.':
-                number_c_string[i] = decimal_point;
+                number_string_length++;
+                has_decimal_point = true;
                 break;
 
             default:
                 goto loop_end;
         }
     }
 loop_end:
-    number_c_string[i] = '\0';
+    /* malloc for temporary buffer, add 1 for '\0' */
+    number_c_string = (unsigned char *) input_buffer->hooks.allocate(number_string_length + 1);
+    if (number_c_string == NULL)
+    {
+        return false; /* allocation failure */
+    }
+
+    memcpy(number_c_string, buffer_at_offset(input_buffer), number_string_length);
+    number_c_string[number_string_length] = '\0';
+
+    if (has_decimal_point)
+    {
+        for (i = 0; i < number_string_length; i++)
+        {
+            if (number_c_string[i] == '.')
+            {
+                /* replace '.' with the decimal point of the current locale (for strtod) */
+                number_c_string[i] = decimal_point;
+            }
+        }
+    }
 
     number = strtod((const char*)number_c_string, (char**)&after_end);
     if (number_c_string == after_end)
     {
+        /* free the temporary buffer */
+        input_buffer->hooks.deallocate(number_c_string);
         return false; /* parse_error */
     }
 
@@ -377,6 +402,8 @@ static cJSON_bool parse_number(cJSON * const item, parse_buffer * const input_bu
     item->type = cJSON_Number;
 
     input_buffer->offset += (size_t)(after_end - number_c_string);
+    /* free the temporary buffer */
+    input_buffer->hooks.deallocate(number_c_string);
     return true;
 }
 

tests/misc_tests.c

@@ -782,6 +782,22 @@ static void cjson_set_bool_value_must_not_break_objects(void)
     cJSON_Delete(sobj);
 }
 
+static void cjson_parse_big_numbers_should_not_report_error(void)
+{
+    cJSON *valid_big_number_json_object1 = cJSON_Parse("{\"a\": true, \"b\": [ null,9999999999999999999999999999999999999999999999912345678901234567]}");
+    cJSON *valid_big_number_json_object2 = cJSON_Parse("{\"a\": true, \"b\": [ null,999999999999999999999999999999999999999999999991234567890.1234567E3]}");
+    const char *invalid_big_number_json1 = "{\"a\": true, \"b\": [ null,99999999999999999999999999999999999999999999999.1234567890.1234567]}";
+    const char *invalid_big_number_json2 = "{\"a\": true, \"b\": [ null,99999999999999999999999999999999999999999999999E1234567890e1234567]}";
+
+    TEST_ASSERT_NOT_NULL(valid_big_number_json_object1);
+    TEST_ASSERT_NOT_NULL(valid_big_number_json_object2);
+    TEST_ASSERT_NULL_MESSAGE(cJSON_Parse(invalid_big_number_json1), "Invalid big number JSONs should not be parsed.");
+    TEST_ASSERT_NULL_MESSAGE(cJSON_Parse(invalid_big_number_json2), "Invalid big number JSONs should not be parsed.");
+
+    cJSON_Delete(valid_big_number_json_object1);
+    cJSON_Delete(valid_big_number_json_object2);
+}
+
 int CJSON_CDECL main(void)
 {
     UNITY_BEGIN();
@@ -815,6 +831,7 @@ int CJSON_CDECL main(void)
     RUN_TEST(cjson_delete_item_from_array_should_not_broken_list_structure);
     RUN_TEST(cjson_set_valuestring_to_object_should_not_leak_memory);
     RUN_TEST(cjson_set_bool_value_must_not_break_objects);
+    RUN_TEST(cjson_parse_big_numbers_should_not_report_error);
 
     return UNITY_END();
 }

tests/parse_number.c

@@ -48,13 +48,25 @@ static void assert_parse_number(const char *string, int integer, double real)
     parse_buffer buffer = { 0, 0, 0, 0, { 0, 0, 0 } };
     buffer.content = (const unsigned char*)string;
     buffer.length = strlen(string) + sizeof("");
+    buffer.hooks = global_hooks;
 
     TEST_ASSERT_TRUE(parse_number(item, &buffer));
     assert_is_number(item);
     TEST_ASSERT_EQUAL_INT(integer, item->valueint);
     TEST_ASSERT_EQUAL_DOUBLE(real, item->valuedouble);
 }
 
+static void assert_parse_big_number(const char *string)
+{
+    parse_buffer buffer = { 0, 0, 0, 0, { 0, 0, 0 } };
+    buffer.content = (const unsigned char*)string;
+    buffer.length = strlen(string) + sizeof("");
+    buffer.hooks = global_hooks;
+
+    TEST_ASSERT_TRUE(parse_number(item, &buffer));
+    assert_is_number(item);
+}
+
 static void parse_number_should_parse_zero(void)
 {
     assert_parse_number("0", 0, 0);
@@ -96,6 +108,13 @@ static void parse_number_should_parse_negative_reals(void)
     assert_parse_number("-123e-128", 0, -123e-128);
 }
 
+static void parse_number_should_parse_big_numbers(void)
+{
+    assert_parse_big_number("9999999999999999999999999999999999999999999999912345678901234567");
+    assert_parse_big_number("9999999999999999999999999999999999999999999999912345678901234567E10");
+    assert_parse_big_number("999999999999999999999999999999999999999999999991234567890.1234567");
+}
+
 int CJSON_CDECL main(void)
 {
     /* initialize cJSON item */
@@ -106,5 +125,6 @@ int CJSON_CDECL main(void)
     RUN_TEST(parse_number_should_parse_positive_integers);
     RUN_TEST(parse_number_should_parse_positive_reals);
     RUN_TEST(parse_number_should_parse_negative_reals);
+    RUN_TEST(parse_number_should_parse_big_numbers);
     return UNITY_END();
 }