[gdal-dev] CVE-2024-3094 (aka "xz hackdoor") and GDAL

[Even Rouault]

Hi,

TLDR: no specific reason to worry.

My longer analysis:

Those following the recent security news have certainly come across 
https://lwn.net/Articles/967180 or similar articles, and if you don't 
have and have been running a cutting edge Linux distribution recently, 
you *should* follow related security alerts emitted by your vendor.

liblzma (the library part of the xz software distribution) is an 
optional libtiff dependency for the TIFF LZMA codec, and an optional 
direct GDAL dependency since GDAL 1.8.0. Initially only used when 
building GDAL with its internal libtiff, and since GDAL 3.4.0, directly 
too as a Zarr codec.

Beyond activity in liblzma / xz being potentially suspicious with at 
least 2 years of "contributions" by malicious actor 
https://github.com/JiaT75, which makes the current headlines, it has 
also been found that they contributed to libarchive too since 2021 
(https://github.com/libarchive/libarchive/commits?author=JiaT75), and 
their latest commit https://github.com/libarchive/libarchive/pull/1609 
is in particular pointed as suspicious. As far as I can see, this commit 
is present in libarchive >= 3.6. I mention libarchive because it is an 
optional GDAL dependency since GDAL 3.7.0 for the /vsi7z/ and /vsirar/ 
virtual file systems.

We don't have vendored copies of liblzma or libarchive in the GDAL 
source code repository.

Regarding GDAL Docker images, here's the status of versions they ship:

- ghcr.io/osgeo/gdal:alpine-small-3.8.4 and 
ghcr.io/osgeo/gdal:alpine-normal-3.8.4:
xz-libs-5.4.3-r0
libarchive-3.7.2-r0

- ghcr.io/osgeo/gdal:ubuntu-full-3.8.4:
liblzma5:amd64                5.2.5-2ubuntu1
libarchive13:amd64            3.6.0-1ubuntu1

- ghcr.io/osgeo/gdal:ubuntu-small-3.8.4:
liblzma5:amd64              5.2.5-2ubuntu1

So those liblzma versions are not currently considered as affected. 
Regarding libarchive status and the impact of JiaT75's activity there, 
it seems to me we are yet in undecided territory and it wouldn't be 
surprising to see update of those libraries in the coming weeks, as 
exploration of past activity from that compromising entity is performed.

It is a good time to recall usual general best-practices:

- avoid opening datasets coming from unknown or untrusted sources

- if you do so, prefer doing that on dedicated workstations that don't 
have access to sensitive information

- you may reduce your potential exposure by disabling at build time 
optional dependencies you don't need.

Even

-- 
http://www.spatialys.com
My software is free, but my time generally not.
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