Announce: OpenSSH 9.3p2 released

[Damien Miller]

OpenSSH 9.3p2 has just been released. It will be available from the
mirrors listed at https://www.openssh.com/ shortly.

OpenSSH is a 100% complete SSH protocol 2.0 implementation and
includes sftp client and server support.

Once again, we would like to thank the OpenSSH community for their
continued support of the project, especially those who contributed
code or patches, reported bugs, tested snapshots or donated to the
project. More information on donations may be found at:
https://www.openssh.com/donations.html

Changes since OpenSSH 9.3
=========================

This release fixes a security bug.

Security
========

Fix CVE-2023-38408 - a condition where specific libaries loaded via
ssh-agent(1)'s PKCS#11 support could be abused to achieve remote
code execution via a forwarded agent socket if the following
conditions are met:

* Exploitation requires the presence of specific libraries on
  the victim system.
* Remote exploitation requires that the agent was forwarded
  to an attacker-controlled system.

Exploitation can also be prevented by starting ssh-agent(1) with an
empty PKCS#11/FIDO allowlist (ssh-agent -P '') or by configuring
an allowlist that contains only specific provider libraries.

This vulnerability was discovered and demonstrated to be exploitable
by the Qualys Security Advisory team.

In addition to removing the main precondition for exploitation,
this release removes the ability for remote ssh-agent(1) clients
to load PKCS#11 modules by default (see below).

Potentially-incompatible changes
--------------------------------

* ssh-agent(8): the agent will now refuse requests to load PKCS#11
modules issued by remote clients by default. A flag has been added
to restore the previous behaviour "-Oallow-remote-pkcs11".

Note that ssh-agent(8) depends on the SSH client to identify
requests that are remote. The OpenSSH >=8.9 ssh(1) client does
this, but forwarding access to an agent socket using other tools
may circumvent this restriction.

Checksums:
==========

- SHA1 (openssh-9.3p2.tar.gz) = 219cf700c317f400bb20b001c0406056f7188ea4
- SHA256 (openssh-9.3p2.tar.gz) = IA6+FH9ss/EB/QzfngJEKvfdyimN/9n0VoeOfMrGdug=

Please note that the SHA256 signatures are base64 encoded and not
hexadecimal (which is the default for most checksum tools). The PGP
key used to sign the releases is available from the mirror sites:
https://cdn.openbsd.org/pub/OpenBSD/OpenSSH/RELEASE_KEY.asc

Reporting Bugs:
===============

- Please read https://www.openssh.com/report.html
Security bugs should be reported directly to ope...@openssh.com

[Dmitry Belyavskiy]

Dear Damien,

Could you please clarify which versions are vulnerable?

> _______________________________________________
> openssh-unix-dev mailing list
> openssh-...@mindrot.org
> https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev

--
Dmitry Belyavskiy

_______________________________________________
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[Christoph Anton Mitterer]

Hey.

On Wed, 2023-07-19 at 08:40 -0600, Damien Miller wrote:
> via a forwarded agent socket if the following
> conditions are met:

I assume this also means that when:
ForwardAgent=no
respectively:
-a
is used, one is not vulnerable?

Thanks,
Chris.

[Damien Miller]

On Wed, 19 Jul 2023, Dmitry Belyavskiy wrote:

> Dear Damien,
>
> Could you please clarify which versions are vulnerable?

OpenSSH 5.5 through 9.3p1 inclusive

[Damien Miller]

On Wed, 19 Jul 2023, Christoph Anton Mitterer wrote:

> Hey.
>
> On Wed, 2023-07-19 at 08:40 -0600, Damien Miller wrote:
> > via a forwarded agent socket if the following
> > conditions are met:
>
> I assume this also means that when:
> ForwardAgent=no
> respectively:
> -a
> is used, one is not vulnerable?

You'd still be vulnerable to a local attack if they could get past the
filesystem permissions, however this is highly unlikely.

I'd recommend the workaround in the release notes though.

[Nico Kadel-Garcia]

On Wed, Jul 19, 2023 at 10:07 PM Damien Miller <d...@mindrot.org> wrote:
>
> On Wed, 19 Jul 2023, Christoph Anton Mitterer wrote:
>
> > Hey.
> >
> > On Wed, 2023-07-19 at 08:40 -0600, Damien Miller wrote:
> > > via a forwarded agent socket if the following
> > > conditions are met:
> >
> > I assume this also means that when:
> > ForwardAgent=no
> > respectively:
> > -a
> > is used, one is not vulnerable?
>
> You'd still be vulnerable to a local attack if they could get past the
> filesystem permissions, however this is highly unlikely.
>
> I'd recommend the workaround in the release notes though.

Disabling agent forwarding is recommended on a lot of systems.
Permitting agent forwarding is *extremely* useful for jump points,
intermediate exposed systems where you might want to use one
credential to log into the jump point, and another private key to
connect to another system, but don't want to install your private key
on the jump point myself.

[Stuart Henderson]

On 2023/07/19 22:14, Nico Kadel-Garcia wrote:
> Disabling agent forwarding is recommended on a lot of systems.
> Permitting agent forwarding is *extremely* useful for jump points,
> intermediate exposed systems where you might want to use one
> credential to log into the jump point, and another private key to
> connect to another system, but don't want to install your private key
> on the jump point myself.

This is probably a good time to consider whether old agent-forwarding
configurations can be replaced with ProxyJump / ssh -J.

[Corinna Vinschen]

Hi Damien,

Can you please add a V_9_3_P2 tag?

Thanks,
Corinna

> _______________________________________________

[Damien Miller]

done (I did tag, just forgot to push it)

On Thu, 20 Jul 2023, Corinna Vinschen wrote:

> Hi Damien,
>
> Can you please add a V_9_3_P2 tag?

[Corinna Vinschen]

On Jul 21 09:04, Damien Miller wrote:
> done (I did tag, just forgot to push it)

Great, thanks!


Corinna

[Dmitry Belyavskiy]

On Thu, Jul 20, 2023 at 3:53 AM Damien Miller <d...@mindrot.org> wrote:
>
>
>
> On Wed, 19 Jul 2023, Dmitry Belyavskiy wrote:
>
> > Dear Damien,
> >
> > Could you please clarify which versions are vulnerable?
>
> OpenSSH 5.5 through 9.3p1 inclusive

Many thanks for the clarification!

--
Dmitry Belyavskiy

[Nico Kadel-Garcia]

On Fri, Jul 21, 2023 at 4:37 AM Dmitry Belyavskiy <dbel...@redhat.com> wrote:
>
> On Thu, Jul 20, 2023 at 3:53 AM Damien Miller <d...@mindrot.org> wrote:
> >
> >
> >
> > On Wed, 19 Jul 2023, Dmitry Belyavskiy wrote:
> >
> > > Dear Damien,
> > >
> > > Could you please clarify which versions are vulnerable?
> >
> > OpenSSH 5.5 through 9.3p1 inclusive
>
> Many thanks for the clarification!

I took a shot at it for RHEL 9. Red Hat and Fedora apply dozens of
tuning patches on top of OpenSSH. I think I'll wait for Fedora to have
a working version to try to port it to RHEL.

[Dmitry Belyavskiy]

Dear Nico,

> I took a shot at it for RHEL 9. Red Hat and Fedora apply dozens of
> tuning patches on top of OpenSSH. I think I'll wait for Fedora to have
> a working version to try to port it to RHEL.

The fix should already land in F38 and rawhide and is in testing in F37

--
Dmitry Belyavskiy