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LibTLS: Don't attempt to read past EOF when parsing TBSCertificate

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This allows the decoder to fail gracefully when reading a partial or
malformed TBSCertificate. We also now ensure that the certificate data
is valid before making a copy of it.
This commit is contained in:
Tim Ledbetter 2023-10-05 17:51:29 +01:00 committed by Andreas Kling
parent 65b50ecc1a
commit e6d9bb0774
4 changed files with 21 additions and 2 deletions
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1
Meta/Lagom/CMakeLists.txt
View file

@ -655,6 +655,7 @@ if (BUILD_LAGOM)
# LibTLS needs a special working directory to find cacert.pem
lagom_test(../../Tests/LibTLS/TestTLSHandshake.cpp LibTLS LIBS LibTLS LibCrypto)
lagom_test(../../Tests/LibTLS/TestTLSCertificateParser.cpp LibTLS LIBS LibTLS)
# The FLAC tests need a special working directory to find the test files
lagom_test(../../Tests/LibAudio/TestFLACSpec.cpp LIBS LibAudio WORKING_DIRECTORY "${FLAC_TEST_PATH}/..")

1
Tests/LibTLS/CMakeLists.txt
View file

@ -1,4 +1,5 @@
set(TEST_SOURCES
TestTLSCertificateParser.cpp
TestTLSHandshake.cpp
)

15
Tests/LibTLS/TestTLSCertificateParser.cpp Normal file
View file

@ -0,0 +1,15 @@
/*
* Copyright (c) 2023, Tim Ledbetter <timledbetter@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibTLS/Certificate.h>
#include <LibTest/TestCase.h>
TEST_CASE(certificate_with_malformed_tbscertificate_should_fail_gracefully)
{
Array<u8, 4> invalid_certificate_data { 0xB0, 0x02, 0x70, 0x00 };
auto parse_result = TLS::Certificate::parse_certificate(invalid_certificate_data);
EXPECT(parse_result.is_error());
}

6
Userland/Libraries/LibTLS/Certificate.cpp
View file

@ -691,10 +691,11 @@ static ErrorOr<Certificate> parse_tbs_certificate(Crypto::ASN1::Decoder& decoder
ENTER_TYPED_SCOPE(Sequence, "TBSCertificate"sv);
auto post_cert_buffer = TRY(decoder.peek_entry_bytes());
auto asn1_data = TRY(ByteBuffer::copy(pre_cert_buffer.slice(0, post_cert_buffer.size() + entry_length_byte_count)));
if (pre_cert_buffer.size() < post_cert_buffer.size() + entry_length_byte_count) {
ERROR_WITH_SCOPE("Unexpected end of file");
}
Certificate certificate;
certificate.tbs_asn1 = asn1_data;
certificate.version = TRY(parse_certificate_version(decoder, current_scope)).to_u64();
certificate.serial_number = TRY(parse_serial_number(decoder, current_scope));
certificate.algorithm = TRY(parse_algorithm_identifier(decoder, current_scope));
@ -702,6 +703,7 @@ static ErrorOr<Certificate> parse_tbs_certificate(Crypto::ASN1::Decoder& decoder
certificate.validity = TRY(parse_validity(decoder, current_scope));
certificate.subject = TRY(parse_name(decoder, current_scope));
certificate.public_key = TRY(parse_subject_public_key_info(decoder, current_scope));
certificate.tbs_asn1 = TRY(ByteBuffer::copy(pre_cert_buffer.slice(0, post_cert_buffer.size() + entry_length_byte_count)));
if (!decoder.eof()) {
auto tag = TRY(decoder.peek());