gpg module fix: already running

[Vonfry]

Fixes #1681, #1164

Proposed Changes

• gpg module: Use gpgconf to get gpg-agent path instead of using environment variables and a fixed path by default, which is more compatible. For example: gpg has been started by systemd, and the sockets is set by sockets.target which is different from the default path ~/.gnugp/S.gpg-agent and no environment variable is set for current shell, but gpgconf can find the correct socket file and using it to check whether gpg-agent is already run. Otherwise, prezto will prompt gpg-agent: a gpg-agent is already running - not starting a new one at startup and it don't pick up the correct gpg-agent socket.
• ssh module: remove re-export SSH_AUTH_SOCK in ssh module. Becasue some tools such as pam ssh auth will check socket file's permission. A link to this socket is useful but re-export the variable will break some tools.

This pr is the same as #1682 but switching into a new branch(not master).

[belak]

Can you give me an example of tools that are broken? Isn't SSH_AUTH_SOCK needed for things like ssh-add?

[Vonfry]

@belak On my system, prezto will print gpg-agent: a gpg-agent is already running - not starting a new one. without this pr, which I don't see on other system.

SSH_AUTH_SOCK is used by many tools, but it is export by ssh automatically. In the old prezto ssh module, this variable is exported with a fixed path like ${TMPDIR:-/tmp}/ssh-agent.sock.$UID which doesn't exist on some system, such as NixOS (this system uses /var/run/$UID/xxx). I removed the repeated assignment in prezto ssh module.

[andrei-pavel]

Potential alternative fix

[mvcouwen]

Any progress on this PR? I seem to have the same issue when ssh-ing into a ubuntu server.

[1wilkens]

I described the problem and potential solutions in #1164
EDIT: Sorry I didn't even look at the PR. It looks reasonable, however I don't know what gpgconf --list-dir agent-sock returns if no agent is running

[Vonfry]

@1wilkens gpgconf always returns the path whether gpg-agent starts or not. When not starting, it returns the path which agent creates by default.

[1wilkens]

But in that case it would return ${GPG_HOME}/.gnupg/S.gpg-agent wouldn't it? The docs seem to suggest that this is the default and systemd overrides that.
So in our case that would be wrong. Not pointing fingers here, just not sure, what the "correct" solution is..

[Vonfry]

@1wilkens IMO, the one who uses prezto to startup a gpg-agent, may not want to use systemd to start it again. If systemd has started gpg-agent, gpg module in prezto will check it, and won't start again.

In the first scenario, gpgconf returns the default path which is used by prezto to create sockets.
In the secound scenario, gpgconf can find the socket created by systemd instead of a default value.

[Vonfry]

@belak Could this pr be merged? I edit the description and make it compatible on some system.

Proposed Changes:

• gpg module: Use gpgconf to get gpg-agent path instead of using environment variables and a fixed path by default, which is more compatible. For example: gpg has been started by systemd, and the sockets is set by sockets.target which is different from the default path ~/.gnugp/S.gpg-agent and no environment variable is set for current shell, but gpgconf can find the correct socket file and use it to check whether gpg-agent is already run. Otherwise, prezto will prompt gpg-agent: a gpg-agent is already running - not starting a new one at startup and it don't pick up the correct gpg-agent socket.
• ssh module: remove re-export SSH_AUTH_SOCK in ssh module. Becasue some tools such as pam ssh auth will check socket file's permission. A link to this socket is useful but re-export the variable will break some tools.

[tigerkzr]

I found the fix on another users fork but I did not see a pull request for it and they have one syntax error. What's the protocol for this? I'm new to this kind of thing, but I would like to get the fix into the system.

Edit: Never mind, it's already in this pull request. Guess it just never got merged into master