Re: Backdoor in upstream xz-utils

[Rostislav Svoboda <rostislav.svoboda@gmail.com>]

> >> Is there a way we can blacklist known bad versions?
>
> I'm not sure what you mean, but I don't think so.

For beginning, what about adding a short comment:

diff --git a/gnu/packages/compression.scm b/gnu/packages/compression.scm
index 5de17b6b51..fd5ab7ba00 100644
--- a/gnu/packages/compression.scm
+++ b/gnu/packages/compression.scm
@@ -493,6 +493,8 @@ (define-public pbzip2
 (define-public xz
   (package
    (name "xz")
+;;; Be reminded of the xz/liblzma backdoor in the versions 5.6.0 and 5.6.1!
+;;; See https://www.openwall.com/lists/oss-security/2024/03/29/4
    (version "5.2.8")
    (source (origin
             (method url-fetch)

as a single commit, with an appropriate commit message. That's a bang
for pretty much no money.

> The main danger is in guix time-machine to the past

Good point. So then a little note here, too:

diff --git a/doc/guix.texi b/doc/guix.texi
index 69a904473c..60909adf5f 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -5012,10 +5012,13 @@ Invoking guix time-machine
 @quotation Note
 The history of Guix is immutable and @command{guix time-machine}
 provides the exact same software as they are in a specific Guix
-revision.  Naturally, no security fixes are provided for old versions
-of Guix or its channels.  A careless use of @command{guix time-machine}
-opens the door to security vulnerabilities.  @xref{Invoking guix pull,
-@option{--allow-downgrades}}.
+revision.  Naturally, no security fixes are provided for old versions of
+Guix or its channels.  A careless use of @command{guix time-machine}
+opens the door to security vulnerabilities, or potentially even
+backdoors. (Do you remember the
+@uref{https://www.openwall.com/lists/oss-security/2024/03/29/4, backdoor
+in upstream xz/liblzma leading to ssh server compromise}?)
+@xref{Invoking guix pull, @option{--allow-downgrades}}.
 @end quotation

Cheers Bost