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Merge pull request #550 from libexpat/prevent-getbuffer-overflow

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[CVE-2022-23852] Prevent XML_GetBuffer signed integer overflow
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Sebastian Pipping 2022-01-24 15:39:04 +01:00 • committed by GitHub
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12
expat/Changes
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@ -2,6 +2,18 @@ NOTE: We are looking for help with a few things:
https://github.com/libexpat/libexpat/labels/help%20wanted
If you can help, please get in touch. Thanks!
Release x.x.x xxx xxxxxxx xx xxxx
Security fixes:
#550 CVE-2022-23852 -- Fix signed integer overflow
(undefined behavior) in function XML_GetBuffer
(that is also called by function XML_Parse internally)
for when XML_CONTEXT_BYTES is defined to >0 (which is both
common and default).
Impact is denial of service or more.
Special thanks to:
Samanta Navarro
Release 2.4.3 Sun January 16 2022
Security fixes:
#531 #534 CVE-2021-45960 -- Fix issues with left shifts by >=29 places

5
expat/lib/xmlparse.c
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@ -2067,6 +2067,11 @@ XML_GetBuffer(XML_Parser parser, int len) {
keep = (int)EXPAT_SAFE_PTR_DIFF(parser->m_bufferPtr, parser->m_buffer);
if (keep > XML_CONTEXT_BYTES)
keep = XML_CONTEXT_BYTES;
/* Detect and prevent integer overflow */
if (keep > INT_MAX - neededSize) {
parser->m_errorCode = XML_ERROR_NO_MEMORY;
return NULL;
}
neededSize += keep;
#endif /* defined XML_CONTEXT_BYTES */
if (neededSize

27
expat/tests/runtests.c
View file

@ -3847,6 +3847,30 @@ START_TEST(test_get_buffer_2) {
}
END_TEST
/* Test for signed integer overflow CVE-2022-23852 */
#if defined(XML_CONTEXT_BYTES)
START_TEST(test_get_buffer_3_overflow) {
XML_Parser parser = XML_ParserCreate(NULL);
assert(parser != NULL);
const char *const text = "\n";
const int expectedKeepValue = (int)strlen(text);
// After this call, variable "keep" in XML_GetBuffer will
// have value expectedKeepValue
if (XML_Parse(parser, text, (int)strlen(text), XML_FALSE /* isFinal */)
== XML_STATUS_ERROR)
xml_failure(parser);
assert(expectedKeepValue > 0);
if (XML_GetBuffer(parser, INT_MAX - expectedKeepValue + 1) != NULL)
fail("enlarging buffer not failed");
XML_ParserFree(parser);
}
END_TEST
#endif // defined(XML_CONTEXT_BYTES)
/* Test position information macros */
START_TEST(test_byte_info_at_end) {
const char *text = "<doc></doc>";
@ -11731,6 +11755,9 @@ make_suite(void) {
tcase_add_test(tc_basic, test_empty_parse);
tcase_add_test(tc_basic, test_get_buffer_1);
tcase_add_test(tc_basic, test_get_buffer_2);
#if defined(XML_CONTEXT_BYTES)
tcase_add_test(tc_basic, test_get_buffer_3_overflow);
#endif
tcase_add_test(tc_basic, test_byte_info_at_end);
tcase_add_test(tc_basic, test_byte_info_at_error);
tcase_add_test(tc_basic, test_byte_info_at_cdata);