192 lines
5.8 KiB
Markdown
192 lines
5.8 KiB
Markdown
# YubiKey plugin for age clients
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`age-plugin-yubikey` is a plugin for [age](https://age-encryption.org/v1) clients
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like [`age`](https://age-encryption.org) and [`rage`](https://str4d.xyz/rage),
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which enables files to be encrypted to age identities stored on YubiKeys.
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## Installation
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On Windows, Linux, and macOS, you can use the
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[pre-built binaries](https://github.com/str4d/age-plugin-yubikey/releases).
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If your system has Rust 1.60+ installed (either via `rustup` or a system
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package), you can build directly from source:
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```
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cargo install age-plugin-yubikey
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```
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Help from new packagers is very welcome.
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### macOS
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You can install using Homebrew:
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```
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brew install age-plugin-yubikey
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```
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### Linux, BSD, etc.
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On non-Windows, non-macOS systems, you need to ensure that the `pcscd` service
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is installed and running.
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#### Debian or Ubuntu
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```
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$ sudo apt-get install pcscd
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```
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#### OpenBSD
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As ```root``` do:
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```
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$ pkg_add pcsc-lite
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$ rcctl enable pcscd
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$ rcctl start pcscd
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```
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#### FreeBSD
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As ```root``` do:
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```
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$ pkg install pcsc-lite
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$ service pcscd enable
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$ service pcscd start
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```
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### Windows Subsystem for Linux (WSL)
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WSL does not currently provide native support for USB devices. However, Windows
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binaries installed on the host can be run from inside a WSL environment. This
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means that you can encrypt or decrypt files inside a WSL environment with a
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YubiKey:
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1. Install `age-plugin-yubikey` on the Windows host.
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2. Install an age client inside the WSL environment.
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3. Ensure that `age-plugin-yubikey.exe` is available in the WSL environment's
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`PATH`. For default WSL setups, the Windows host's `PATH` is automatically
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added to the WSL environment's `PATH` (see
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[this Microsoft blog post](https://devblogs.microsoft.com/commandline/share-environment-vars-between-wsl-and-windows/)
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for more details).
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## Configuration
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There are two ways to configure a YubiKey as an `age` identity. You can run the
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plugin binary directly to use a simple text interface, which will create an age
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identity file:
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```
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$ age-plugin-yubikey
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```
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Or you can use command-line flags to programmatically generate an identity and
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print it to standard output:
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```
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$ age-plugin-yubikey --generate \
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[--serial SERIAL] \
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[--slot SLOT] \
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[--name NAME] \
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[--pin-policy PIN-POLICY] \
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[--touch-policy TOUCH-POLICY]
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```
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Once an identity has been created, you can regenerate it later:
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```
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$ age-plugin-yubikey --identity [--serial SERIAL] --slot SLOT
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```
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## Usage
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The age recipients contained in all connected YubiKeys can be printed on
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standard output:
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```
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$ age-plugin-yubikey --list
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```
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To encrypt files to these YubiKey recipients, ensure that `age-plugin-yubikey`
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is accessible in your `PATH`, and then use the recipients with an age client as
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normal (e.g. `rage -r age1yubikey1...`).
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The output of the `--list` command can also be used directly to encrypt files to
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all recipients (e.g. `age -R filename.txt`).
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To decrypt files encrypted to a YubiKey identity, pass the identity file to the
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age client as normal (e.g. `rage -d -i yubikey-identity.txt`).
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## Advanced topics
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### Agent support
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`age-plugin-yubikey` does not provide or interact with an agent for decryption.
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It does however attempt to preserve the PIN cache by not soft-resetting the
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YubiKey after a decryption or read-only operation, which enables YubiKey
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identities configured with a PIN policy of `once` to not prompt for the PIN on
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every decryption. **This does not work for YubiKey 4 series.**
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The session that corresponds to the `once` policy can be ended in several ways,
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not all of which are necessarily intuitive:
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- Unplugging the YubiKey (the obvious way).
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- Using a different applet (e.g. FIDO2). This causes the PIV applet to be closed
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which clears its state.
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- This is why the YubiKey 4 series does not support PIN cache preservation:
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their serial can only be obtained by switching to the OTP applet.
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- Generating a new age identity via `age-plugin-yubikey --generate` or the CLI
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interface. This is to avoid leaving the YubiKey authenticated with the
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management key.
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If the current PIN UX proves to be insufficient, a decryption agent will most
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likely be implemented as a separate age plugin that interacts with
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[`yubikey-agent`](https://github.com/FiloSottile/yubikey-agent), enabling
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YubiKeys to be used simultaneously with age and SSH.
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### Manual setup and technical details
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`age-plugin-yubikey` only officially supports the following YubiKey variants,
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set up either via the text interface or the `--generate` flag:
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- YubiKey 4 series
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- YubiKey 5 series
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NOTE: Nano and USB-C variants of the above are also supported. The pre-YK4
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YubiKey NEO series is **NOT** supported. The blue "Security Key by Yubico" will
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also not work (as it doesn't support PIV).
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In practice, any PIV token with an ECDSA P-256 key and certificate in one of the
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20 "retired" slots should work. You can list all age-compatible keys with:
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```
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$ age-plugin-yubikey --list-all
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```
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`age-plugin-yubikey` implements several automatic security management features:
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- If it detects that the default PIN is being used, it will prompt the user to
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change the PIN. The PUK is then set to the same value as the PIN.
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- If it detects that the default management key is being used, it generates a
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random management key and stores it in PIN-protected metadata.
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`age-plugin-yubikey` does not support custom management keys.
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## License
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Licensed under either of
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* Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
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http://www.apache.org/licenses/LICENSE-2.0)
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* MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
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at your option.
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### Contribution
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Unless you explicitly state otherwise, any contribution intentionally
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submitted for inclusion in the work by you, as defined in the Apache-2.0
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license, shall be dual licensed as above, without any additional terms or
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conditions.
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