mirror of
https://github.com/PrivSec-dev/privsec.dev.git
synced 2024-12-15 10:44:48 -05:00
86 lines
3.3 KiB
Markdown
86 lines
3.3 KiB
Markdown
---
|
|
title: "Using Split GPG and Split SSH on Qubes OS"
|
|
date: 2022-08-13
|
|
tags: ['Operating Systems', 'Qubes OS', 'Security']
|
|
author: Tommy
|
|
---
|
|
|
|
|
|
|
|
This post will go over setting up Split GPG, then setting up Split SSH with the same PGP keys. Effectively, we are emulating what you can do with a PGP smartcard on Qubes OS.
|
|
|
|
## Split GPG
|
|
|
|
Follow the official Qubes OS [documentation](https://www.qubes-os.org/doc/split-gpg/) to set this up.
|
|
|
|
Note that if you already have a PGP key with a passphrase, you can remove it by installing `pinentry-gtk` to `vault`'s TemplateVM, then do `gpg2 --edit-key <key_id>` and `passwd` to set an empty passphrase. The default non-graphical pinentry will just make an infinite loop and will not allow you to set an empty passphrase.
|
|
|
|
## Split SSH
|
|
|
|
This part is based on the Qubes Community's [guide](https://github.com/Qubes-Community/Contents/blob/master/docs/configuration/split-ssh.md); however, I will deviate from it to use the PGP keys for SSH instead of generating a new key pair.
|
|
|
|
### In `dom0`
|
|
|
|
- Create `/etc/qubes-rpc/policy/qubes.SshAgent` with `@anyvm @anyvm ask,default_target=vault` as the content. Since the keys ar not passphrase protected, you should **not** set the policy to allow.
|
|
|
|
### In `vault` AppVM
|
|
- Add `enable-ssh-support` to the end of `~/.gnupg/gpg-agent.conf`
|
|
- Get your keygrip with `gpg --with-keygrip -k`
|
|
- Add your keygrip to the end of `~/.gnupg/sshcontrol`
|
|
|
|
|
|
|
|
### In `vault`'s TemplateVM
|
|
|
|
- Create `/etc/qubes-rpc/qubes.SshAgent` with the following content:
|
|
```bash
|
|
#!/bin/sh
|
|
# Qubes App Split SSH Script
|
|
|
|
# Activate GPG Agent and set the correct SSH socket
|
|
export SSH_AUTH_SOCK=$(gpgconf --list-dirs agent-ssh-socket)
|
|
gpgconf --launch gpg-agent
|
|
|
|
# safeguard - Qubes notification bubble for each ssh request
|
|
notify-send "[$(qubesdb-read /name)] SSH agent access from: $QREXEC_REMOTE_DOMAIN"
|
|
|
|
# SSH connection
|
|
socat - "UNIX-CONNECT:$SSH_AUTH_SOCK"
|
|
|
|
```
|
|
|
|
- Make it executable with `sudo chmod +x /etc/qubes-rpc/qubes.SshAgent`
|
|
- Turn off the templateVM. If the `vault` VM is running, turn it off, then start it to update the VM's configuration.
|
|
|
|
### In `ssh-client` AppVM
|
|
|
|
- Add the following to the end of `/rw/config/rc.local`:
|
|
```bash
|
|
# SPLIT SSH CONFIGURATION >>>
|
|
# replace "vault" with your AppVM name which stores the ssh private key(s)
|
|
SSH_VAULT_VM="vault"
|
|
|
|
if [ "$SSH_VAULT_VM" != "" ]; then
|
|
export SSH_SOCK="/home/user/.SSH_AGENT_$SSH_VAULT_VM"
|
|
rm -f "$SSH_SOCK"
|
|
sudo -u user /bin/sh -c "umask 177 && exec socat 'UNIX-LISTEN:$SSH_SOCK,fork' 'EXEC:qrexec-client-vm $SSH_VAULT_VM qubes.SshAgent'" &
|
|
fi
|
|
# <<< SPLIT SSH CONFIGURATION
|
|
```
|
|
|
|
- Add the following to the end of `~/bash.rc`:
|
|
```bash
|
|
# SPLIT SSH CONFIGURATION >>>
|
|
# replace "vault" with your AppVM name which stores the ssh private key(s)
|
|
SSH_VAULT_VM="vault"
|
|
|
|
if [ "$SSH_VAULT_VM" != "" ]; then
|
|
export SSH_AUTH_SOCK="/home/user/.SSH_AGENT_$SSH_VAULT_VM"
|
|
fi
|
|
# <<< SPLIT SSH CONFIGURATION
|
|
```
|
|
|
|
- Restart `ssh-client` and confirm if it's working with `ssh-add -L`.
|
|
|
|
### Limitations
|
|
A malicious `ssh-client` AppVM can hold onto the ssh-agent connection for more than one use until it is shut down. While your private key is protected, a malicious actor with access to the AppVM can still abuse the ssh-agent to log into your servers. |