On Sat, Mar 30, 2024 at 1:08 PM Dave Ihnat <dihnat@dminet.com> wrote:
>
> Didn't see this go by, but it looks hot enough to risk a repeat posting.
> From a friend:
>
>   It appears there's been a very serious effort to backdoor sshd on
>   Linux via the xz compression/decompression system.
>
>   https://www.openwall.com/lists/oss-security/2024/03/29/4
>
>   If you have anything running very recent Linux, it's worth investigating
>   whether you're affected.
>
>   IBM Red Hat says, if you're running Fedora 40 or Fedora Rawhide:
>
>   > PLEASE IMMEDIATELY STOP USAGE OF ANY FEDORA
>   > RAWHIDE INSTANCES for work or personal activity.
>
>   The identity that did this got to the point of being not only an xz
>   maintainer but a Linux kernel contributor, and contributed to a number
>   of other Open Source projects as well over the course of years. The
>   identity may have been compromised to do this, or may have been created
>   to do this, and may have used other contributions to build rapport or
>   to compromise more projects as well.
>
> I looked at the detection script available at the URL in the posting. It's
> harmless at worst (don't know yet if it can detect anything).

It looks like more analysis has revealed this is a RCE with the
payload in the modulus of a public key: "The payload is extracted from
the N value (the public key) passed to RSA_public_decrypt, checked
against a simple fingerprint, and decrypted with a fixed ChaCha20 key
before the Ed448 signature verification..." Also see
<https://www.openwall.com/lists/oss-security/2024/03/30/36>.

Jeff
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