I can use the ssh configuration file to enable the forwarding of ssh keys added to ssh-agent. How can I do the same with gpg keys?

  • 3
    Both answers suggest running socat to expose the GPG agent unix socket on a tcp port. However, unlike unix sockets, TCP ports do not have the same level on access control. In particular, every user on the same host can now connect to your GPG agent. This is probably ok if you have a single-user laptop, but if any other users can also log into the same system (the system where the GPG agent is running), they can also access your GPG agent, posing a significant security problem. Letting socat directly start SSH using the EXEC address type is probably the best way to fix this. Commented Aug 4, 2014 at 10:02
  • For another presentation of the openssh 6.7+ solution, see 2015.rmll.info/IMG/pdf/an-advanced-introduction-to-gnupg.pdf
    – phs
    Commented Oct 5, 2016 at 21:21
  • This was useful to me.
    – phs
    Commented Dec 5, 2016 at 18:54

6 Answers 6


EDIT: This answer is obsolete now that proper support has been implemented in OpenSSH, see Brian Minton's answer.

SSH is only capable of forwarding tcp connections within the tunnel.

You can, however, use a program like socat to relay the unix socket over TCP, with something like that (you will need socat both on the client and the server hosts):

# Get the path of gpg-agent socket:
GPG_SOCK=$(echo "$GPG_AGENT_INFO" | cut -d: -f1)

# Forward some local tcp socket to the agent
(while true; do
    socat TCP-LISTEN:12345,bind= UNIX-CONNECT:$GPG_SOCK;
done) &

# Connect to the remote host via ssh, forwarding the TCP port
ssh -R12345:localhost:12345 host.example.com

# (On the remote host)
(while true; do
    socat UNIX-LISTEN:$HOME/.gnupg/S.gpg-agent,unlink-close,unlink-early TCP4:localhost:12345;
done) &

Test if it works out with gpg-connect-agent. Make sure that GPG_AGENT_INFO is undefined on the remote host, so that it falls back to the $HOME/.gnupg/S.gpg-agent socket.

Now hopefully all you need is a way to run all this automatically!

  • Well the ssh agent keys are forwarded automatically when the forwarding is set in the configuration file. I will try this out.
    – txwikinger
    Commented Jul 19, 2010 at 14:18
  • You're right, ssh-agent uses a unix socket too, but has special support for it (little bit tired here :) Nevertheless, the solution should still work.
    – b0fh
    Commented Jul 19, 2010 at 14:32
  • 1
    For this solution, my gpg-agent would be publicy accessible via port 12345 if I was not behind a firewall/NAT. This should be mentioned in the answer please. Commented Apr 30, 2012 at 14:46
  • I'm guessing your last edit fixed that issue, Jonas? it's only binding to localhost now.
    – jmtd
    Commented May 1, 2012 at 8:19
  • This fails for me with the following argument from the remote host's gpg-connect-agent: can't connect to server: ec=31.16383 gpg-connect-agent: error sending RESET command: Invalid value passed to IPC. The remote socat then dies. The local socat dies and utters socat[24692] E connect(3, AF=1 "", 2): Invalid argument. This page leads me to believe that this will never work, because the agent doesn't store the key (just the passphrase). Has this been confirmed to work by anyone?
    – jmtd
    Commented May 1, 2012 at 8:24

OpenSSH's new Unix Domain Socket Forwarding can do this directly starting with version 6.7.

You should be able to something like:

ssh -R /home/bminton/.gnupg/S.gpg-agent:/home/bminton/.gnupg/S-gpg-agent -o "StreamLocalBindUnlink=yes" -l bminton
  • @DrewR. Glad to hear that. Commented Jun 1, 2015 at 19:58
  • 5
    I found a required critical detail: on the remote (private key-less) machine, the public key of the signing identity must be present. Local gpg version 2.1.15 OS X, remote 2.1.11 linux.
    – phs
    Commented Oct 6, 2016 at 4:06
  • 1
    If you have your pyblic keys published on the keyservers, you can setup the remote keyring with something like gpg -K --keyid-format long | grep '\[SC\]' | grep -v expired | sed 's#sec \+[^/]\+/\([0-9A-F]\+\).*#\1#' | ssh user@target 'xargs -n 1 gpg --recv-key'. We can figure out the socket names automatically: ssh -A user@target -R "$(ssh user@target 'gpgconf --list-dirs agent-socket')":"$(gpgconf --list-dirs agent-extra-socket)" 'gpg -K'
    – pkoch
    Commented Mar 21, 2020 at 20:56
  • This does not work with OpenSSH 8.1 client (mac) and OpenSSH server 7.6 (ubuntu), even after exporting and importing the public key. Maybe I'm doing something wrong, but passwordstore decryption fails with gpg: decryption failed: No secret key. Is it intentional that the remote gpg agent file has the dot replaced by a hyphen?
    – oarfish
    Commented Mar 11, 2021 at 13:04
  • 2
    It seems that on Ubuntu 18.04, systemd owns the file with the host's extra socket, and the ssh deamon cannot bind to it (joutnalctl tells me address already in use and ` error: unix_listener: cannot bind to path: /run/user/1001/gnupg/S.gpg-agent.extra`). Is this answer still current?
    – oarfish
    Commented Mar 11, 2021 at 13:41

In new versions of GnuPG or Linux distributions the paths of the sockets can change. These can be found out via

$ gpgconf --list-dirs agent-extra-socket


$ gpgconf --list-dirs agent-socket

Then add these paths to your SSH configuration:

Host remote
  RemoteForward <remote socket> <local socket>

Quick solution for copying the public keys:

scp .gnupg/pubring.kbx remote:~/.gnupg/

On the remote machine, activate GPG agent:

echo use-agent >> ~/.gnupg/gpg.conf

On the remote machine, also modify the SSH server configuration and add this parameter (/etc/ssh/sshd_config):

StreamLocalBindUnlink yes

Restart SSH server, reconnect to the remote machine - then it should work.

  • A more detailed tutorial including some troubleshooting can be found here: mlohr.com/gpg-agent-forwarding
    – MaLo
    Commented Jun 7, 2018 at 7:39
  • 2
    In case the remote host runs a current version of Debian, it seems running systemctl --global mask --now gpg-agent.service gpg-agent.socket gpg-agent-ssh.socket gpg-agent-extra.socket gpg-agent-browser.socket is required to prevent systemd from launching a socket stealing remote gpg-agent. According to bugs.debian.org/850982 this is the intended behavior.
    – sampi
    Commented Jul 16, 2018 at 10:13
  • 3
    You might need to prevent the remote gpg-agent from starting and removing the forwarded socket. This is also described in the gpg wiki. What they don't say is how to do that. echo no-autostart >> ~/.ssh/gpg-agent.conf on the remote machine worked for me.
    – magiconair
    Commented Mar 16, 2020 at 15:14
  • 2
    Test whether it works with echo test | gpg --clearsign
    – magiconair
    Commented Mar 16, 2020 at 15:14
  • 1
    use-agent is no longer necessary, nowadays it is a dummy option gnupg.org/documentation/manuals/gnupg/… Commented Aug 29, 2022 at 12:06

I had to do the same, and based my script on the solution by b0fh, with a few tiny modifications: It traps exits and kills background processes, and it uses the "fork" and "reuseaddr" options to socat, which saves you the loop (and makes the background socat cleanly kill-able).

The whole thing sets up all forwards in one go, so it probably comes closer to an automated setup.

Note that on the remote host, you will need:

  1. The keyrings you intend to use to sign/en/decrypt stuff.
  2. Depending on the version of gpg on the remote, a fake GPG_AGENT_INFO variable. I prefill mine with ~/.gnupg/S.gpg-agent:1:1 - the first 1 is a PID for the gpg agent (I fake it as "init"'s, which is always running), the second is the agent protocol version number. This should match the one running on your local machine.

#!/bin/bash -e


trap '[ -z "$LOCAL_SOCAT" ] || kill -TERM $LOCAL_SOCAT' EXIT

GPG_SOCK=$(echo "$GPG_AGENT_INFO" | cut -d: -f1)
if [ -z "$GPG_SOCK" ] ; then
    echo "No GPG agent configured - this won't work out." >&2
    exit 1

socat TCP-LISTEN:$FORWARD_PORT,bind=,reuseaddr,fork UNIX-CONNECT:$GPG_SOCK &

ssh -R $FORWARD_PORT:$FORWARD_PORT socat 'UNIX-LISTEN:$HOME/.gnupg/S.gpg-agent,unlink-close,unlink-early,fork,reuseaddr TCP4:localhost:$FORWARD_PORT'

I believe there's also a solution that involves just one SSH command invocation (connecting back from the remote host to the local one) using -o LocalCommand, but I couldn't quite figure out how to conveniently kill that upon exit.

  • Aren't you missing some 'user@host' argument before socat, in the last command? Anyhow even after fixing that, this fails for me with "socat[6788] E connect(3, AF=2, 16): Connection refused" popping up locally, when trying gpg-connect-agent remotely. Commented Aug 7, 2016 at 18:56

As an alternative to modifying /etc/ssh/sshd_config with StreamLocalBindUnlink yes, you can instead prevent the creation of the socket files that need replacing:

systemctl --global mask --now \
  gpg-agent.service \
  gpg-agent.socket \
  gpg-agent-ssh.socket \
  gpg-agent-extra.socket \

Note that this affects all users on the host.

Bonus: How to test GPG agent forwarding is working:

  • Local: ssh -v -o RemoteForward=${remote_sock}:${local_sock} ${REMOTE}
  • Check that ${remote_sock} is shown in the verbose output from ssh
  • Remote: ls -l ${remote_sock}
  • Remote: gpg --list-secret-keys
    • You should see lots of debug1 messages from ssh showing the forwarded traffic

If that doesn't work (as it didn't for me) you can trace which socket GPG is accessing:

strace -econnect gpg --list-secret-keys

Sample output:

connect(5, {sa_family=AF_UNIX, sun_path="/run/user/14781/gnupg/S.gpg-agent"}, 35) = 0

In my case the path being accessed perfectly matched ${remote_sock}, but that socket was not created by sshd when I logged in, despite adding StreamLocalBindUnlink yes to my /etc/ssh/sshd_config. I was created by systemd upon login.

(Note I was too cowardly to restart sshd, since I've no physical access to the host right now. service reload sshd clearly wasn't sufficient...)

Tested on Ubuntu 16.04


According to GnuPG Wiki, you have to forward the remote socket S.gpg-agent.extra to local socket S.gpg-agent. Furthermore you need to enable StreamLocalBindUnlink on the server.
Keep in mind that you also need the public part of your key available on remote GnuPG.

Use gpgconf --list-dir agent-socket respectively gpgconf --list-dir agent-extra-socket on the remote to get the actual paths.


  1. Addded configuration on remote /etc/sshd_config:

    StreamLocalBindUnlink yes
  2. Import your public key on remote:

    gpg --export <your-key> >/tmp/public
    scp /tmp/public <remote-host>:/tmp/public
    ssh <remote-host> gpg --import /tmp/public
  3. Command to connect through SSH with gpg-agent forwarding enabled: (paths for my Debian)

    ssh -R /run/user/1000/gnupg/S.gpg-agent:/run/user/1000/gnupg/S.gpg-agent.extra <remote-host>
  • @brian minton: It does not work for me if not forwarding to the extra socket.
    – doak
    Commented Jun 6, 2018 at 12:48

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