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wg-quick linux: Add strip-and-eval cmd to extract keys from PostUp #3

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@ypid ypid commented Oct 4, 2020

I will also submit this to the mailing list. I just open a PR here because I find it easier to get an overview what has been merged and what not.

Note that the patchset is incomplete (currently only for Linux). I don’t have all the other OSes laying around.

The manpage mentions the trick to use PostUp to read the PrivateKey (or PresharedKey) from a command (or file). However, when you actually use that you notice that this is currently not fully supported. The issue is that

wg syncconf wgnet0 <(wg-quick strip wgnet0)

from the manpage now breaks the VPN because it removes the private key from the WireGuard interface. The reason is that strip removes PostUp of course.

This patch tries to add full support to read WireGuard keys from files or command outputs by evaluating PostUp using a best effort approach (using regex). It will not work for everything but when you follow the manpage closely, it will work.

I also propose to update the systemd template to make seamless use of this. This is not a must because the sysadmin can easily change the ExecReload using systemd drop-in files.

Example use of this patch: https://github.com/ypid/ansible-wireguard/tree/prepare-for-debops

@ypid ypid force-pushed the feature/wg-quick/strip-and-eval branch from 6714da3 to 9762a0b Compare October 4, 2020 21:12
The manpage mentions the trick to use PostUp to read the PrivateKey (or
PresharedKey) from a command (or file). However, when you actually use
that you notice that this is currently not fully supported. The issue is
that

```Shell
wg syncconf wgnet0 <(wg-quick strip wgnet0)
```

from the manpage now breaks the VPN because it *removes* the private key
from the WireGuard interface. The reason is that `strip` removes PostUp
of course.

This patch tries to add full support to read WireGuard keys from files
or command outputs by evaluating PostUp using a best effort approach
(using regex). It will not work for everything but when you follow the
manpage closely, it will work.

I also propose to update the systemd template to make seamless use of
this. This is not a must because the sysadmin can easily change the
ExecReload using systemd drop-in files.

Note that the patchset is incomplete (currently only for Linux).
I don’t have all the other OSes laying around. When the patch looks ok,
I can apply it to the other versions also.

Example use of this patch:
https://github.com/ypid/ansible-wireguard/tree/prepare-for-debops

Signed-off-by: Robin Schneider <[email protected]>
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