Add any additional identities or email addresses you wish to associate using the `adduid` command.
**Optional** Verify with OpenPGP key checks, use the automated [key best practice checker](https://riseup.net/en/security/message-security/openpgp/best-practices#openpgp-key-checks):
**Tip** Verify with a OpenPGP [key best practice checker](https://riseup.net/en/security/message-security/openpgp/best-practices#openpgp-key-checks):
Once GPG keys are moved to YubiKey, they cannot be moved again! Create an **encrypted** backup of the keyring and consider using a [paper copy](https://www.jabberwocky.com/software/paperkey/) of the keys as an additional backup.
**Tip**: The ext2 filesystem (without encryption) can be mounted on both Linux and OpenBSD.
**Linux**
Attach another external storage device and check its label:
@ -1266,7 +1272,7 @@ gpg: Total number processed: 1
gpg: imported: 1
```
Edit the master key to assign it ultimate trust by selecting `trust`then option`5`:
Edit the master key to assign it ultimate trust by selecting `trust`and`5`:
```console
$ export KEYID=0xFF3E7D88647EBCDB
@ -1470,16 +1476,18 @@ Probably the biggest thing missing from `gpg-agent`'s ssh agent support is being
Create a hardened configuration for gpg-agent by downloading [drduh/config/gpg-agent.conf](https://github.com/drduh/config/blob/master/gpg-agent.conf):
**Note** To make multiple connections or securely transfer many files, consider using the [ControlMaster](https://en.wikibooks.org/wiki/OpenSSH/Cookbook/Multiplexing) ssh option. Also see [drduh/config/ssh_config](https://github.com/drduh/config/blob/master/ssh_config).
## Touch to authenticate
**Note** This is not possible on YubiKey NEO.
By default, YubiKey will perform key operations without requiring a touch from the user. To require a touch for every SSH authentication, use the [YubiKey Manager](https://developers.yubico.com/yubikey-manager/) and Admin PIN:
```console
$ ykman openpgp touch aut on
```
To require a touch for signing and encryption operations:
```console
$ ykman openpgp touch sig on
$ ykman openpgp touch enc on
```
The YubiKey will blink when it's waiting for touch.
## Import SSH keys
If there are existing SSH keys that you wish to make available via `gpg-agent`, you'll need to import them. You should then remove the original private keys. When importing the key, `gpg-agent` uses the key's filename as the key's label; this makes it easier to follow where the key originated from. In this example, we're starting with just the YubiKey's key in place and importing `~/.ssh/id_rsa`:
@ -1785,25 +1773,24 @@ StreamLocalBindUnlink yes
And reload the SSH daemon (e.g., `sudo service sshd reload`).
#### Final test
Unplug YubiKey, disconnect or reboot. Log back in to Windows, open a WSL console and enter `ssh-add -l` - you should see nothing.
Plug in YubiKey, enter the same command to display the ssh key.
- Unplug YubiKey, disconnect or reboot.
- Log back in to Windows, open a WSL console and enter `ssh-add -l` - you should see nothing.
- Plug in YubiKey, enter the same command to display the ssh key.
- Log in to the remote host, you should have the pinentry dialog asking for the YubiKey pin.
- On the remote host, type `ssh-add -l` - if you see the ssh key, that means forwarding works!
Log in to the remote host, you should have the pinentry dialog asking for the YubiKey pin.
On the remote host, type `ssh-add -l` - if you see the ssh key, that means forwarding works!
**Note** Agent forwarding may be chained through multiple hosts - just follow the same [protocol](#remote-host-configuration) to configure each host.
# Using multiple YubiKey with same GPG keys
# multiple keys
If you want to store your keys on multiple YubiKey, you will see that GnuPG doesn't store the serial number of the first key it has seen.
This is a know issue [#T2291](https://dev.gnupg.org/T2291). For now if you lost one of your keys and want to use another one the only workaround
is to delete GnuPG's shadowed key (this is where the serial number is stored).
GnuPG doesn't store the serial number of the first key it has seen - [#T2291](https://dev.gnupg.org/T2291).
To do so, first of all you need to find the `Keygrip` number of each key :
```
gpg2 --with-keygrip -k $KEYID
If a YubiKey is lost and replaced, delete GnuPG's shadowed key - where the serial number is stored. Find the `Keygrip` number of each key:
Insert the new YubiKey and re-generate shadow-keys by checking card status:
```console
$ gpg --card-status
```
cd .gnupg/private-keys-v1.d
rm 85D44BD52AD45C0852BD15BF41161EE9AE477398.key \
A0AA3D9F626BDEA3B833F290C7BCA79216C8A996.key \
7EF25A1115294342F451BC1CDD0FA94395F2D074.key
# Require touch
**Note** This is not possible on YubiKey NEO.
By default, YubiKey will perform encryption, signing and authentication operations without requiring any action from the user, after the key is plugged in and first unlocked with the PIN.
To require a touch for each key operation, install [YubiKey Manager](https://developers.yubico.com/yubikey-manager/) and recall the Admin PIN:
Authentication:
```console
$ ykman openpgp touch aut on
```
Insert the new YubiKey simply run a card-status this will re-generate the shadow-keys :
Signing:
```console
$ ykman openpgp touch sig on
```
gpg2 --card-status
Encryption:
```console
$ ykman openpgp touch enc on
```
Then try to use your key, it should work, without serial number error.
YubiKey will blink when it is waiting for a touch.
# Email
GPG keys on YubiKey can be used with ease to encrypt or sign email messages and attachments using [Thunderbird](https://www.thunderbird.net/) and [Enigmail](https://www.enigmail.net). Thunderbird supports OAuth 2 authentication and can be used with Gmail. See [this guide](https://ssd.eff.org/en/module/how-use-pgp-linux) from EFF for detailed instructions.
# Reset
If PIN attempts are exceeded, the card is locked and must be [reset](https://developers.yubico.com/ykneo-openpgp/ResetApplet.html) and set up again using the encrypted backup.
Copy the following script to a file and run `gpg-connect-agent -R $file` to lock and terminate the card. Then re-insert YubiKey to reset.
```console
/hex
scd serialno
scd apdu 00 20 00 81 08 40 40 40 40 40 40 40 40
scd apdu 00 20 00 81 08 40 40 40 40 40 40 40 40
scd apdu 00 20 00 81 08 40 40 40 40 40 40 40 40
scd apdu 00 20 00 81 08 40 40 40 40 40 40 40 40
scd apdu 00 20 00 83 08 40 40 40 40 40 40 40 40
scd apdu 00 20 00 83 08 40 40 40 40 40 40 40 40
scd apdu 00 20 00 83 08 40 40 40 40 40 40 40 40
scd apdu 00 20 00 83 08 40 40 40 40 40 40 40 40
scd apdu 00 e6 00 00
scd apdu 00 44 00 00
/echo Card has been successfully reset.
```
# Notes
1. YubiKey has two configurations: one invoked with a short press, and the other with a long press. By default, the short-press mode is configured for HID OTP - a brief touch will emit an OTP string starting with `cccccccc`. If you rarely use the OTP mode, you can swap it to the second configuration via the YubiKey Personalization tool. If you *never* use OTP, you can disable it entirely using the [YubiKey Manager](https://developers.yubico.com/yubikey-manager) application (note, this not the similarly named YubiKey NEO Manager).
@ -1870,8 +1909,6 @@ GPG keys on YubiKey can be used with ease to encrypt or sign email messages and
- If SSH authentication stil fails - add up to 3 `-v` flags to increase verbosity.
- If you totally screw up, you can [reset the card](https://developers.yubico.com/ykneo-openpgp/ResetApplet.html).
drduh
5 years ago