Hello!

One of our servers got its strongswan-charon package upgraded from
6.0.1-5 to 6.0.1-6 last night. It has ipsec connections to another
trixie machine that's still using 6.0.1-5 and to a bookworm machine
that's using 5.9.8-5+deb12u1

No changes to the configuration happened for a while. Since the upgrade
happened, the host with 6.0.1-6 can't establish connection to the other
two hosts anymore. If I start the connection manually I can see the
followup output (peer IP replaced by 1.2.3.4; local IP replaced by 1.2.1.2):

ipsec up connection-name
initiating IKE_SA connection-name[6] to 1.2.3.4
generating IKE_SA_INIT request 0 [ SA KE No N(NATD_S_IP) N(NATD_D_IP)
N(FRAG_SUP) N(HASH_ALG) N(REDIR_SUP) ]
sending packet: from 1.2.1.2[500] to 1.2.3.4[500] (972 bytes)
received packet: from 1.2.3.4[500] to 1.2.1.2[500] (280 bytes)
parsed IKE_SA_INIT response 0 [ SA KE No N(NATD_S_IP) N(NATD_D_IP)
N(FRAG_SUP) N(HASH_ALG) N(CHDLESS_SUP) N(MULT_AUTH) ]
selected proposal:
IKE:AES_CBC_128/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/ECP_256
KDF_PRF with PRF_HMAC_SHA2_256 not supported
key derivation failed
establishing connection 'connection-name' failed


Is this an expected compatibility break or is that an unexpected regression?

Very weird..

downgrading to 6.0.1-5 did not fix the issue.

I've compared the configuration files with the other servers and I'm not
seeing any difference.

So I don't actually have a good understanding of what happened on the
host that got the upgrade to 6.0.1-6 this morning :\

Hi Gabriel,

If you have OpenSSL 3.5.1 installed, then this is unfortunately
expected.  It requires the patches at [1] and [2], which were released
with 6.0.2.

Regards,
Tobias

[1]
https://github.com/strongswan/strongswan/commit/2dbeecfc029ba26647c756b0882bc6e85e2e6b64
[2]
https://github.com/strongswan/strongswan/commit/43b805b2daed48bdf835ca8eeb87b9b71a42781f

Hi Gabriel,

If you have OpenSSL 3.5.1 installed, then this is unfortunately
expected.  It requires the patches at [1] and [2], which were released
with 6.0.2.

Regards,
Tobias

[1]
https://github.com/strongswan/strongswan/commit/2dbeecfc029ba26647c756b0882bc6e85e2e6b64
[2]
https://github.com/strongswan/strongswan/commit/43b805b2daed48bdf835ca8eeb87b9b71a42781f

We ended up figuring out that the problem was on our side. I'm not sure
what actually caused this situation, but a reboot fixed the problem.

So there was actually no issue with the contents of the strongswan
package. sorry for the noise!

FTR, the workaround is to install the libstrongswan-extra-plugins
package, including the kdf plugin.

Regards
Harri

Dear Maintainers,

It might be a good idea to apply these two patches to 6.0.1 in trixie,
in order to avoid that everybody has to install
libstrongswan-extra-plugins just for the kdf plugin.

Also, the problem could technically also occur on bookworm as the
OpenSSL guys have backported their "fix" to 3.0.17 for some reason.  The
difference there is that the kdf plugin is installed by default via
libstrongswan package, while the openssl plugin is shipped separately in
libstrongswan-standard-plugins.  So it will only be a problem if the kdf
plugin is explicitly disabled in the config.

Regards,
Tobias

Dear Maintainers,

It might be a good idea to apply these two patches to 6.0.1 in trixie,
in order to avoid that everybody has to install
libstrongswan-extra-plugins just for the kdf plugin.

Also, the problem could technically also occur on bookworm as the
OpenSSL guys have backported their "fix" to 3.0.17 for some reason.  The
difference there is that the kdf plugin is installed by default via
libstrongswan package, while the openssl plugin is shipped separately in
libstrongswan-standard-plugins.  So it will only be a problem if the kdf
plugin is explicitly disabled in the config.

Regards,
Tobias

Thanks for the heads up Tobias, I'll try to prepare updated packages for
Trixie in the following weeks.

Regards,

We believe that the bug you reported is fixed in the latest version of
strongswan, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1109942@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Yves-Alexis Perez <corsac@debian.org> (supplier of updated strongswan package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Fri, 22 Aug 2025 10:45:05 +0200
Source: strongswan
Architecture: source
Version: 6.0.2-1
Distribution: unstable
Urgency: medium
Maintainer: strongSwan Maintainers <pkg-swan-devel@lists.alioth.debian.org>
Changed-By: Yves-Alexis Perez <corsac@debian.org>
Closes: 1109942
Changes:
 strongswan (6.0.2-1) unstable; urgency=medium
 .
   * New upstream version 6.0.2
     - Fix support with OpenSSL 3.5.1+ (Closes: #1109942)
   * install iptfs configuration in libstrongswan
   * d/copyright updated with decopy
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We believe that the bug you reported is fixed in the latest version of
strongswan, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1109942@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Yves-Alexis Perez <corsac@debian.org> (supplier of updated strongswan package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Fri, 22 Aug 2025 09:58:42 +0200
Source: strongswan
Architecture: source
Version: 6.0.1-6+deb13u1
Distribution: trixie
Urgency: medium
Maintainer: strongSwan Maintainers <pkg-swan-devel@lists.alioth.debian.org>
Changed-By: Yves-Alexis Perez <corsac@debian.org>
Closes: 1109942
Changes:
 strongswan (6.0.1-6+deb13u1) trixie; urgency=medium
 .
   * d/patches: add patches to fix OpenSSL 3.5.1 support (Closes: #1109942)
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