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GnuPG can, with gpg-agent, cache access to a private key. How can I keep that cache active for the entire user session?

When I unlock the key for gpg-agent, it only stays cached for a limited time. With SSH's agent, I enter the passphrase one time and it stays cached for the whole session. I want the same behaviour from gpg-agent.

So, ssh-agent doesn't suffer from a limited cache lifetime. But gpg-agent limits the cache lifetime, at least by default. How can I eliminate the limit on cache time from gpg-agent?

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79

Up to GnuPG 2

The user configuration (in ~/.gnupg/gpg-agent.conf) can only define the default and maximum caching duration; it can't be disabled.

The default-cache-ttl option sets the timeout (in seconds) after the last GnuPG activity (so it resets if you use it), the maximum-cache-ttl option set the timespan (in seconds) it caches after entering your password. The default value is 600 seconds (10 minutes) for default-cache-ttl and 7200 seconds (2 hours) for maximum-cache-ttl.

Set it to a year or so – say, 34560000 seconds (400 days) – and you should be fine:

default-cache-ttl 34560000
maximum-cache-ttl 34560000

But for this change to take effect, you need to end the session by restarting gpg-agent.

If you want to limit to your session length, you'd need to kill the daemon at logout. This is very different between operating systems, so I'm referring to another question/answer containing hints for different systems.

You could also restart the gpg-agent during login, but this does not limit caching time to the session length, but logins of a user. Decide yourself if this is a problem in your case.

GnuPG 2.1 and above

In GnuPG 2.1 and above, the maximum-cache-ttl option was renamed to max-cache-ttl without further changes.

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  • Is this a “you can't do what you're asking” response? It's not clear, since you're talking about limiting the session length or limiting caching time. I want exactly the opposite of that: no arbitrary limit on the cache time or session length. – bignose Jul 29 '13 at 0:58
  • Kind of that, you can only workaround by setting a rather huge ttl. Set it to a year or so and you should be fine - but need to end the session by restarting gpg-agent. – Jens Erat Jul 29 '13 at 8:12
  • Please note that in latests versions (at least gnupg 2.1), the maximum-cache-ttl option doesn't exist. To see the correct options, see the official documentation: gnupg.org/documentation/manuals/gnupg/… – Pablo Olmos de Aguilera C. Dec 27 '14 at 19:12
  • 4
    At least in GnuPG 2.1 the default for default-cache-ttl is 600 seconds (10 minutes), not two hours. – jlh Oct 3 '17 at 9:30
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    What can the reason be that my GPG4Win asks every 10 minutes even that my settings are set to the samples above? max-cache-ttl 34560000 – Ben Dec 17 '18 at 17:34
7

For Windows

The file you need to edit should be placed at: $env:AppData\gnupg

If you run that in a PowerShell window it will open: C:\Users\<UserName>\AppData\Roaming\gnupg

Just put the gpg-agent.conf file there with whatever values you like.

You can verify it took by running:

  1. gpgconf.exe --reload gpg-agent
  2. gpgconf.exe --list-options gpg-agent

You can also use this one liner: Set-Content -Path $env:AppData\gnupg\gpg-agent.conf -Value "default-cache-ttl 86400$([System.Environment]::NewLine)max-cache-ttl 86400"

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  • If a second answer here isn't appropriate we can move this to it's own question, tagged with Windows. Not sure what's right :) – CubanX Apr 23 '19 at 14:12
  • Thanks and keep it here - good to have all info in one place. 👍 – barfuin Jun 13 '19 at 16:57
7

Make sure to reload your gpg agent with gpg-connect-agent reloadagent /bye after changing the config.

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