openpgp-card/tools/README.md

OpenPGP card tools

This crate contains two tools for inspecting, configuring and using OpenPGP cards: opgpcard and opgpcard-pin.

Install

One easy way to install this crate is via the "cargo" tool.

The following build dependencies are needed for current Debian:

# apt install rustc cargo clang pkg-config nettle-dev libpcsclite-dev

And for current Fedora:

# dnf install rustc cargo clang nettle-devel pcsc-lite-devel

Afterwards, you can install this crate by running:

$ cargo install openpgp-card-tools

Finally, add $HOME/.cargo/bin to your PATH to be able to run the installed binaries.

opgpcard

A tool to inspect, configure and use OpenPGP cards. All calls of this tool are non-interactive (this tool is designed to be easily usable from shell-scripts).

List and inspect cards

List idents of all currently connected cards:

$ opgpcard list
Available OpenPGP cards:
 ABCD:01234567
 ABCD:87654321

Print status information about a card. The card is implicitly selected. However, this only works if exactly one card is connected:

$ opgpcard status
OpenPGP card ABCD:01234567 (card version 2.0)

Cardholder: Foo Bar

Signature key
  fingerprint: 1FE2 E8F1 9FE8 7D0D 8AAF  5579 8CB7 58BA 502F 2458
  created: 2022-03-25 20:15:49
  algorithm: Ed25519 (EdDSA)

Decryption key
  fingerprint: 68CB 4EDD 4D49 90B8 2CEC  2D22 EF7E 5B6A 2012 694C
  created: 2022-03-25 20:15:49
  algorithm: Cv25519 (ECDH)

Authentication key
  fingerprint: 59A5 CD3E A88F 8707 D887  EAAE 1354 5F40 4E11 BE1C
  created: 2022-03-25 20:15:49
  algorithm: Ed25519 (EdDSA)

Signature counter: 3
Signature pin only valid once: true
Password validation retry count:
  user pw: 3, reset: 3, admin pw: 3

Explicitly print the status information for a specific card (this command syntax is needed, when more than one card is plugged in):

$ opgpcard status --card ABCD:01234567

Add -v for more verbose card status (including the list of supported algorithms, if the card returns an algorithm list):

$ opgpcard status -c ABCD:01234567 -v
OpenPGP card ABCD:01234567 (card version 2.0)

Cardholder: Foo Bar

Signature key
  fingerprint: 1FE2 E8F1 9FE8 7D0D 8AAF  5579 8CB7 58BA 502F 2458
  created: 2022-03-25 20:15:49
  algorithm: Ed25519 (EdDSA)
  public key material: ECC, data: 4C6364692AA4212AA95CF25FF31FD5F94CCAC173BFD77C918E443F09FAAFE3F5

Decryption key
  fingerprint: 68CB 4EDD 4D49 90B8 2CEC  2D22 EF7E 5B6A 2012 694C
  created: 2022-03-25 20:15:49
  algorithm: Cv25519 (ECDH)
  public key material: ECC, data: B99202743227D87D5F24639937DF75C936AC7933CE3328F5BF6AFA174A4A8745

Authentication key
  fingerprint: 59A5 CD3E A88F 8707 D887  EAAE 1354 5F40 4E11 BE1C
  created: 2022-03-25 20:15:49
  algorithm: Ed25519 (EdDSA)
  public key material: ECC, data: BFE1E5EB31032E0F4320E163082BEDBAD2A6318EC368375F7A65D22AC7AB7444

Signature counter: 3
Signature pin only valid once: true
Password validation retry count:
  user pw: 3, reset: 3, admin pw: 3

Supported algorithms:
SIG: RSA 2048 [e 32]
SIG: RSA 4096 [e 32]
SIG: Secp256k1 (ECDSA)
SIG: Ed25519 (EdDSA)
SIG: Ed448 (EdDSA)
DEC: RSA 2048 [e 32]
DEC: RSA 4096 [e 32]
DEC: Secp256k1 (ECDSA)
DEC: Cv25519 (ECDH)
DEC: X448 (ECDH)
AUT: RSA 2048 [e 32]
AUT: RSA 4096 [e 32]
AUT: Secp256k1 (ECDSA)
AUT: Ed25519 (EdDSA)
AUT: Ed448 (EdDSA)

Using a card for ssh auth

To use an OpenPGP card for ssh login authentication, a PGP authentication key needs to exist on the card.

opgpcard ssh then shows the ssh public key string representation of the PGP authentication key on the card, like this:

$ opgpcard ssh
OpenPGP card ABCD:01234567

Authentication key fingerprint:
BEC2E8D8AD9C54A6AEDE71CCA1CE6FAC5ABF0BE4

Authentication key as ssh public key:
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAII2dcYBqMCamidT5MpE3Cl3MIKcYMBekGXbK2aaN6JaH opgpcard:ABCD:01234567

To allow login to a remote machine, that ssh public key can be added to .ssh/authorized_keys on that remote machine.

In the example output above, this string is the ssh public key:

ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAII2dcYBqMCamidT5MpE3Cl3MIKcYMBekGXbK2aaN6JaH opgpcard:ABCD:01234567

Set card metadata

Set cardholder name:

$ opgpcard admin -c ABCD:01234567 -P <admin-pin-file> name "Foo Bar"

Set cardholder URL:

$ opgpcard admin -c ABCD:01234567 -P <admin-pin-file> url "https://key.url.example"

Import keys

Import private key onto a card. This works if at most one (sub)key per role (sign, decrypt, auth) exists in key.priv:

$ opgpcard admin -c ABCD:01234567 -P <admin-pin-file> import key.priv

Import private key onto a card while explicitly selecting subkeys. Explicitly specified fingerprints are necessary if more than one subkey exists in key.priv for any role (note: spaces in fingerprints are ignored).

$ opgpcard admin -c ABCD:01234567 -P <admin-pin-file> import key.priv \
 --sig-fp "F290 DBBF 21DB 8634 3C96  157B 87BE 15B7 F548 D97C" \
 --dec-fp "3C6E 08F6 7613 8935 8B8D  7666 73C7 F1A9 EEDA C360" \
 --auth-fp "D6AA 48EF 39A2 6F26 C42D  5BCB AAD2 14D5 5332 C838"

When fingerprints are only specified for a subset of the roles, no keys will be imported for the other roles.

Generate Keys on the card

$ opgpcard admin -c ABCD:01234567 -P <admin-pin-file> generate -p <user-pin-file> -o <output-cert-file> 25519
 Generate subkey for Signing
 Generate subkey for Decryption
 Generate subkey for Authentication
-----BEGIN PGP PUBLIC KEY BLOCK-----
Comment: 1FE2 E8F1 9FE8 7D0D 8AAF  5579 8CB7 58BA 502F 2458
Comment: Foo Bar
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=v95a
-----END PGP PUBLIC KEY BLOCK-----

Signing

For now, this tool only supports creating detached signatures, like this (if no input file is set, stdin is read):

$ opgpcard sign --detached -c ABCD:01234567 -p <user-pin-file> -s <cert-file> <input-file>

Decrypting

Decryption using a card (if no input file is set, stdin is read):

$ opgpcard decrypt -c ABCD:01234567 -p <user-pin-file> -r <cert-file> <input-file>

Factory reset

Factory reset:

$ opgpcard factory-reset -c ABCD:01234567

NOTE: you do not need a PIN to reset a card!

Using file-descriptors for PINs

When using a shell like bash , you can pass user and/or admin PINs via file-descriptors:

$ opgpcard sign --detached -c ABCD:01234567 -p /dev/fd/3 -s <cert-file> 3<<<123456

$ opgpcard admin -c ABCD:01234567 -P /dev/fd/3 generate -p /dev/fd/4 -o <output-cert-file> 25519 3<<<12345678 4<<<123456

Directly entering PINs on card readers with pinpad

If your OpenPGP card is inserted in a card reader with a pinpad, this tool offers you the option to use the pinpad to enter the user- or admin-PINs. To do this, you can omit the -p and/or '-P' parameters - then you will be prompted to enter the user or admin PINs where needed.

opgpcard-pin

An interactive tool to set the admin and user PINs, and to reset the user PIN on OpenPGP cards.

Set a new user PIN

Setting a new user PIN requires the admin PIN:

opgpcard-pin -c ABCD:01234567 set-user-pin

(The default admin PIN on unconfigured cards is typically 12345678)

Set new admin PIN

This requires the (previous) admin PIN.

opgpcard-pin -c ABCD:01234567 set-admin-pin

(The default admin PIN on unconfigured cards is typically 12345678)

Recover from blocked user PIN (using the admin PIN)

When a user has entered a wrong user PIN too often, the card goes into a blocked state, in which presenting the user PIN is not possible anymore. The purpose of this is to prevent attackers from trying all possible PINs (e.g. after stealing a card).

To be able to use the card again, the user PIN must be "reset".

Reset user PIN after it has been blocked (requires admin PIN):

opgpcard-pin -c ABCD:01234567 reset-user-pin -a

Recover from blocked user PIN (using the resetting code)

The resetting code is an optional/alternative method to recover from a blocked user PIN.

Context: in some (e.g. corporate) settings, users might not be given the admin PIN for their cards. Instead, an admin may define a resetting code and give that code to the user.

Set resetting code (requires admin PIN):

opgpcard-pin -c ABCD:01234567 set-reset-code

Once a reset code has been defined, the user can reset the blocked user PIN, using the resetting code:

opgpcard-pin -c ABCD:01234567 reset-user-pin

Directly entering PINs on card readers with pinpad

If your OpenPGP card is inserted in a card reader with a pinpad, this tool assumes you will want to enter all PINs via that pinpad. It will prompt you to enter PINs accordingly.