In case if someone finds it through a search:

README and INSTALL now suggest to to use a build directory.

@MathiasMagnus This change is to support Win32-OpenSSH by gpg-agent emulation of ssh-agent; You can use gpg-agent emulation of ssh-agent when you use Win32-OpenSSH. That is, you can use GPG auth subkey for Win32-OpenSSH.

@gniibe Am I misunderstanding something? I thought that with this change one is able to connect from a Windows box to a Linux box and have GPG agent forwarding work. I am still hitting pretty much the same issue described here: https://github.com/PowerShell/Win32-OpenSSH/issues/1564
On my Windows endpoint I'm running gpg.exe version 2.4.0.49237 and in C:\Users\mate\AppData\Roaming\gnupg\gpg-agent.conf I have a single line enable-win32-openssh-support. Running gpg-connect-agent.exe reloadagent /bye I have a gpg-agent running. Get-Process gpg-agent shows that it's running. In my Windows env I have SSH_AUTH_SOCK set to \\.\pipe\openssh-ssh-agent and my Linux endpoint is configured in SSH config with

ForwardAgent yes
AddKeysToAgent yes
RemoteForward /run/user/1015/gnupg/S.gpg-agent C\:/Users/mate/AppData/Local/gnupg/S.gpg-agent.extra

As the remote end reports /run/user/1015/gnupg/S.gpg-agent that socket for agent-socket when issuing gpgconf --list-dirs and my local gpgconfg.exe --list-dirs reports C%3a\Users\mate\AppData\Local\gnupg\S.gpg-agent.extra where I transform %3a to \: manually. SSH authentication works perfectly, when connecting pinentry-qt pops up to unlock my key and when connecting to yet another machine, my SSH agent is forwarded again. However, gpg fails to use my agent. Issuing gpg --list-secret-keys --verbose prints the following to the console:

gpg --list-secret-keys --verbose
gpg: using pgp trust model
getsockopt SO_ERROR failed
connect_to C:/Users/mate/AppData/Local/gnupg/S.gpg-agent.extra port -2: failed.
gpg: no running gpg-agent - starting '/usr/bin/gpg-agent'
getsockopt SO_ERROR failed
connect_to C:/Users/mate/AppData/Local/gnupg/S.gpg-agent.extra port -2: failed.
gpg: waiting for the agent to come up ... (5s)
getsockopt SO_ERROR failed
connect_to C:/Users/mate/AppData/Local/gnupg/S.gpg-agent.extra port -2: failed.
getsockopt SO_ERROR failed
connect_to C:/Users/mate/AppData/Local/gnupg/S.gpg-agent.extra port -2: failed.
getsockopt SO_ERROR failed
connect_to C:/Users/mate/AppData/Local/gnupg/S.gpg-agent.extra port -2: failed.
getsockopt SO_ERROR failed
connect_to C:/Users/mate/AppData/Local/gnupg/S.gpg-agent.extra port -2: failed.
getsockopt SO_ERROR failed
connect_to C:/Users/mate/AppData/Local/gnupg/S.gpg-agent.extra port -2: failed.
getsockopt SO_ERROR failed
connect_to C:/Users/mate/AppData/Local/gnupg/S.gpg-agent.extra port -2: failed.
gpg: waiting for the agent to come up ... (4s)
gpg: waiting for the agent to come up ... (3s)
gpg: waiting for the agent to come up ... (2s)
gpg: waiting for the agent to come up ... (1s)
gpg: can't connect to the agent: End of file

What is missing to tie the knot on both ends without having to resort to 3rd party tools like @rupor-github 's agent-gui? The remote gpg version is 2.2.19, is that the issue? Must that also be 2.3.9+?

Somehow I was waiting for such a comment ;-) Sure you are right and we will fix the README eventually.

This is probably not the right place, but considering you're telling people *here* that they should not build in the source tree, your README and INSTALL files do tell the users to do exactly that.

Pushed the change.

I will push this change:

commit e89d57a2cb10bd04d266165015f159be2ab48984
Author: NIIBE Yutaka <gniibe@fsij.org>
Date:   Wed Dec 21 10:52:24 2022 +0900

You should do it for all software ;-).

Sorry, one more thing: I should use out of source builds for all gnupg software (libgpg-error, libksba, etc)? It's fine if so, just want to check what the policy is.

Ah, thanks! I didn't know this was unsupported. I'll change what we're doing.

You are building in the source tree - not a good idea. This should be supported but we don't test this. Please make your life easier and don't do build this way. We try to fix this for the next release.

Thanks !

A real fix will be in the next gpgrt release

Implications are... you won't be possible to use new protocols introduced by newer OpenSSH:

Thanks. Adding 'PubkeyAuthentication unbound' to my ~/.ssh/config seems to workaround it for me on openssh-9.1p1-3 (arch). I don't quite follow what the implications of that setting are though.

In my cases (tested with 9.1), here are the length of data to be signed by ssh-agent (emulation by gpg-agent).

• 164 bytes: Both features disabled by: ssh -o KexAlgorithms=-sntrup761x25519-sha512@openssh.com -o PubkeyAuthentication=unbound
• 192 bytes: Unbound only by: ssh -o PubkeyAuthentication=unbound
• 298 bytes: No Post Quantum only by: ssh -o KexAlgorithms=-sntrup761x25519-sha512@openssh.com
• 330 bytes: Both features enabled (no options)

I tested with openssh 9.1. When I add -o PubkeyAuthentication=unbound, I can make the length of data smaller.

In T5931#165009, @alexk wrote:

A workaround you can add the following line to ~/.ssh/config or /etc/ssh/ssh_config:

KexAlgorithms -sntrup761x25519-sha512@openssh.com

For me ssh -o KexAlgorithms=-sntrup761x25519-sha512@openssh.com ... does work as well.

A workaround you can add the following line to ~/.ssh/config or /etc/ssh/ssh_config:

We should close this. The recent fix in 2.2 and the forthcoming 2.3 does everything we want. In the meantiime or if further problems turn up, --ignore-cert is a good workaround.

Small correction: We don't have replicas of our code signing key. I mistook this with out Authenticode signing key.

In general I use my standard ed25519 signing token for all software. However, GnuPG VS-Desktop is signed using a Brainpool key named GnuPG.com (stored on a smartcard with 2 replicas) for the simple reason that it does not raise questions when ppl update their GnuPG VS-Desktop and run into a non-compliant key.

In the situation of a certificate about to be expired in the cache:

Thanks, @gniibe -- i agree that this change to put_cert should be helpful, when encountering a certificate that is already invalid.

rejecting an intermediate certificate too.

Pushed the change of mine to master, since I can confirm that it results validate_cert_chain working better, because of put_cert's rejecting an intermediate certificate too.

I'm going to backport this to 2.2, as it found useful.

Forgot to mention one thing: after changing my user folder directory I lost all my Outlook contacts. I was able to recover them... make sure you have a backup before attempting this!

I just had the same issue as hurui200320. My user name contains a "ç" and Kleopatra did not start. The Windows event logger reported a crash in libstdc++-6.dll. This was with gpg4win-3.1.16. Installing gnupg 2.3.1 did not change anything.

gpg4win 3.1 has no full Unicode support. You may try to install the new GnuPG 2.3 version on top of gpg4win to fix this problem or wait until we have releases gpg4win 4 which will come with GnuPG 2.3.