Generate and verify HMAC-based authentication tokens.

Originally designed for use within OpenStack clusters, Fernet is intended to be fast and light-weight, with non-persistent tokens. Fernet tokens are signed with a SHA256 HMAC and their contents encrypted with AES128 in CBC mode.

Fernet Haskell Implementation

Fernet generates and verifies HMAC-based authentication tokens.

Originally designed for use within OpenStack clusters, it was intended to be fast and light-weight, with non-persistent tokens. Integrity and confidentiality of the token contents are implemented with HMAC SHA256 and AES128 CBC.

See the Fernet Spec for a little more information.

Usage

To encrypt a token:

>>> import Network.Fernet
>>> k <- generateKey
>>> keyToBase64 k
"JQAeL3iFN9wIW_hMKiIzA1EiG_EZNivnMPBOOJn2wZc="
>>> token <- encrypt k "secret text"
>>> print token
"gAAAAABY0H9kx7ihkcj6ZF_bQ73Lvc7aG-ZlEtjx24io-DQy5tCjLbq1JvVY27uAe6BuwG8css-4LDIywOJRyY_zetq7aLPPag=="

The resulting token can be distributed to clients. To check and decrypt the token, use the same key:

>>> decrypt k 60 token
Right "secret text"

Do read the Network.Fernet module documentation for further information.

Command-line tool

This package also includes a command-line tool for encrypting and decrypting tokens.

Fernet Utility

Usage: fernet (((-k|--key STRING) | --key-file FILENAME) ([-e|--encrypt] |
              [-d|--decrypt]) [--ttl SECONDS] | (-g|--gen-key))
  Encrypts/decrypts Fernet tokens. One token written to stdout for each line
  read from stdin. Use --gen-key to make a key.

Available options:
  -h,--help                Show this help text
  -k,--key STRING          Base64-urlsafe-encoded 32 byte encryption key
  --key-file FILENAME      File containing the encryption key
  -e,--encrypt             Encryption mode (default: autodetect)
  -d,--decrypt             Decryption mode (default: autodetect)
  --ttl SECONDS            Token lifetime in seconds (default: 1 minute)
  -g,--gen-key             Generate a key from the password on standard input

Development

Building with Stack

stack build

Building with Nix

nix-shell -p cabal2nix --command "cabal2nix --shell . > default.nix"
nix-shell --command "cabal configure"
cabal build

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