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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?

117

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.

11
  • 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
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    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
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    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 – Benjamin Abt Dec 17 '18 at 17:34
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    I think this should use "max-cache-ttl", since the "maximum-cache-ttl" option does not exists (in gnupg 2.1). I'd fix this as a typo, but I'm not sure if it maybe does exist in other versions? – Matthijs Kooijman Aug 30 '20 at 18:33
19

For Windows

The file you need to edit should be placed at: ~\.gnupg\

If you run that in a PowerShell window it will open: C:\Users\<UserName>\.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 ~\.gnupg\gpg-agent.conf -Value "default-cache-ttl 86400$([System.Environment]::NewLine)max-cache-ttl 86400"

Older Versions Of GPG

In older versions, the file was at: $env:AppData\gnupg (C:\Users\<UserName>\AppData\Roaming\gnupg)

So if you can't find it at ~\.gnupg\gpg-agent.conf look there.

4
  • 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
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    Thanks very much. In my case, I had to move this file to it ~/.gnupg/gpg-agent.conf only then it worked. I didn't have GnuPG folder inside AppData, might help someone else. – Saravanabalagi Ramachandran Apr 17 '20 at 21:44
  • Hmm, in looking at this, given that Windows has moved closer to the Linux model for this stuff, not even sure a second answer is needed. I'll leave it up to the community to decide to dump this one. – CubanX Jul 13 '20 at 15:13
13

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

2
  • 1
    I'm not sure if this is a comment or answer. Weird that it got upvote. It's not related to what the OP is asking. OP wants to have longer cache time for passphrase. – MaXi32 Sep 16 '20 at 15:39
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    It is more like a comment but I couldn't write those when I wrote this answer. Also no matter how you change your config, you need to reload the agent or nothing changes. – SuperSandro2000 Sep 18 '20 at 11:44
1

Since your problem is you need more or unlimited cache time for passphrase, then you can use gpg-preset-passphrase to cache your gpg password, and you will have unlimited cache time until the agent is restarted / reloaded. Read the documentation here:

gpg-preset-passphrase:

Passphrases set with this utility don’t expire unless the --forget option is used to explicitly clear them from the cache — or gpg-agent is either restarted or reloaded (by sending a SIGHUP to it). Note that the maximum cache time as set with --max-cache-ttl is still honored. It is necessary to allow this passphrase presetting by starting gpg-agent with the --allow-preset-passphrase.

Documentation

Example how to cache password using gpg-preset-passphrase utility in bash:

#!/bin/bash
GPG_PRESET_PASS="/usr/libexec/gpg-preset-passphrase"
KEY_GRIP=$(gpg --with-keygrip --list-secret-keys $KEY_ID | grep -Pom1 '^ *Keygrip += +\K.*')
read -s -p "[$script_name]: Enter passphrase to cache into gpg-agent: " PASSPHRASE; echo
$GPG_PRESET_PASS -c $KEY_GRIP <<< $PASSPHRASE
RETVAL=$?
if [ $RETVAL = 0 ]; then
    echo "OK"
else
    echo "NOT OK"
fi

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