Remove the backdoor found in 5.6.0 and 5.6.1 (CVE-2024-3094).

While the backdoor was inactive (and thus harmless) without inserting
a small trigger code into the build system when the source package was
created, it's good to remove this anyway:

  - The executable payloads were embedded as binary blobs in
    the test files. This was a blatant violation of the
    Debian Free Software Guidelines.

  - On machines that see lots bots poking at the SSH port, the backdoor
    noticeably increased CPU load, resulting in degraded user experience
    and thus overwhelmingly negative user feedback.

  - The maintainer who added the backdoor has disappeared.

  - Backdoors are bad for security.

This reverts the following without making any other changes:

6e636819 Tests: Update two test files.
a3a29bbd Tests: Test --single-stream can decompress bad-3-corrupt_lzma2.xz.
0b4ccc91 Tests: Update RISC-V test files.
8c9b8b20 liblzma: Fix typos in crc32_fast.c and crc64_fast.c.
82ecc538 liblzma: Fix false Valgrind error report with GCC.
cf44e4b7 Tests: Add a few test files.
3060e107 Tests: Use smaller dictionary size in RISC-V test files.
e2870db5 Tests: Add two RISC-V Filter test files.

The RISC-V test files also have real content that tests the filter
but the real content would fit into much smaller files. A generator
program would need to be available as well.

Thanks to Andres Freund for finding and reporting it and making
it public quickly so others could act without a delay.
See: https://www.openwall.com/lists/oss-security/2024/03/29/4
This commit is contained in:
Lasse Collin 2024-04-08 15:32:58 +03:00
parent fd1b975b78
commit 1107712e37
12 changed files with 8 additions and 66 deletions

View File

@ -135,8 +135,11 @@ typedef uint32_t (*crc32_func_type)(
// This resolver is shared between all three dispatch methods. It serves as
// the ifunc resolver if ifunc is supported, otherwise it is called as a
// regular function by the constructor or first call resolution methods.
// The function attributes are needed for safe IFUNC resolver usage with GCC.
lzma_resolver_attributes
// The __no_profile_instrument_function__ attribute support is checked when
// determining if ifunc can be used, so it is safe to use here.
#ifdef CRC_USE_IFUNC
__attribute__((__no_profile_instrument_function__))
#endif
static crc32_func_type
crc32_resolve(void)
{

View File

@ -98,7 +98,9 @@ typedef uint64_t (*crc64_func_type)(
# pragma GCC diagnostic ignored "-Wunused-function"
#endif
lzma_resolver_attributes
#ifdef CRC_USE_IFUNC
__attribute__((__no_profile_instrument_function__))
#endif
static crc64_func_type
crc64_resolve(void)
{

View File

@ -128,31 +128,6 @@
# endif
#endif
#ifdef CRC_USE_IFUNC
// Two function attributes are needed to make IFUNC safe with GCC.
//
// no-omit-frame-pointer prevents false Valgrind issues when combined with
// a few other compiler flags. The optimize attribute is supported on
// GCC >= 4.4 and is not supported with Clang.
# if TUKLIB_GNUC_REQ(4,4) && !defined(__clang__)
# define no_omit_frame_pointer \
__attribute__((optimize("no-omit-frame-pointer")))
# else
# define no_omit_frame_pointer
# endif
// The __no_profile_instrument_function__ attribute support is checked when
// determining if ifunc can be used, so it is safe to use unconditionally.
// This attribute is needed because GCC can add profiling to the IFUNC
// resolver, which calls functions that have not yet been relocated leading
// to a crash on liblzma start up.
# define lzma_resolver_attributes \
__attribute__((__no_profile_instrument_function__)) \
no_omit_frame_pointer
#else
# define lzma_resolver_attributes
#endif
// For CRC32 use the generic slice-by-eight implementation if no optimized
// version is available.
#if !defined(CRC32_ARCH_OPTIMIZED) && !defined(CRC32_GENERIC)

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@ -41,8 +41,6 @@
good-0catpad-empty.xz has two zero-Block Streams concatenated with
four-byte Stream Padding between the Streams.
good-2cat.xz has two Streams with one Block each.
good-1-check-none.xz has one Stream with one Block with two
uncompressed LZMA2 chunks and no integrity check.
@ -83,14 +81,6 @@
good-1-arm64-lzma2-2.xz is like good-1-arm64-lzma2-1.xz but with
non-zero start offset. XZ Embedded doesn't support this file.
good-1-riscv-lzma2-1.xz uses the RISC-V filter and LZMA2. The
uncompressed data is constructed so it tests all of the instructions
that should be encoded and a few that should not. Additionally, the
file contains random bytes to help test unforeseen corner cases.
good-1-riscv-lzma2-2.xz is like good-1-riscv-lzma2-1.xz but with
non-zero start offset. XZ Embedded doesn't support this file.
good-1-lzma2-1.xz has two LZMA2 chunks, of which the second sets
new properties.
@ -294,11 +284,6 @@
Uncompressed Size bytes of output will have been produced but
the LZMA2 decoder doesn't indicate end of stream.
bad-3-corrupt_lzma2.xz has three Streams in it. The first and third
streams are valid xz Streams. The middle Stream has a correct Stream
Header, Block Header, Index and Stream Footer. Only the LZMA2 data
is corrupt. This file should decompress if --single-stream is used.
3. Descriptions of Individual .lzma Files
@ -315,14 +300,6 @@
will give an error at the end of the file after producing the
correct uncompressed output.
good-small_compressed.lzma was created with a small dictionary (2^16).
It contains the string "Hello World" repeated 100,000 times. This tests
match decoding and wrapping the dictionary.
good-large_compressed.lzma was created with a mix of repeated
characters and random data to test a data stream containing many
matches and many literals.
3.2. Bad Files
@ -344,10 +321,6 @@
bad-too_small_size-without_eopm-3.lzma is like -1 above but instead
of a literal the problem occurs in the middle of a match.
bad-dict_size.lzma has a valid dictionary size according to the .lzma
File Format, but will be rejected by XZ Utils because it is not 2^n or
2^n + 2^(n-1).
4. Descriptions of Individual .lz (lzip) Files

Binary file not shown.

Binary file not shown.

Binary file not shown.

Binary file not shown.

Binary file not shown.

View File

@ -149,17 +149,6 @@ else
exit 1
fi
# Test that --single-stream can decompress bad-3-corrupt_lzma2.xz.
# The first Stream in this file should decompress without errors.
# This file cannot be decompressed with xzdec.
I="$srcdir/files/bad-3-corrupt_lzma2.xz"
if test -z "$XZ" || "$XZ" -dc --single-stream $NO_WARN "$I" > /dev/null; then
:
else
echo "Good first Stream failed xz with --single-stream: $I"
exit 1
fi
#########
# .lzma #