h-gpgme: High Level Haskell Bindings for GnuPG Made Easy

h-gpgme wraps gpgme, the library GnuPG offers to programs that want OpenPGP without shelling out to gpg. The API stays close to the C one, but the memory management, error handling and resource cleanup a C API leaves to the caller become ordinary Haskell values and bracket-style functions.

The crypto itself comes from the GnuPG installation already on the machine: the same keyrings, the same gpg-agent, the same trust database.

Features

• Encryption and decryption — to one or more recipients (encrypt, decrypt), symmetrically when you name no recipient at all, and on file descriptors (encryptFd, decryptFd) for data you would rather not hold in memory.
• Signing and verification — normal, detached and cleartext signatures (sign with SignMode), verification of attached and detached signatures (verify, verifyDetached), and the combined encryptSign / decryptVerify.
• Key lookup — by fingerprint (getKey), across a keyring (listKeys), or by user id (searchKeys), down to the user ids, subkeys, algorithms and validity of what comes back.
• Key import, export and removal — importKeyFromFile, importKeyFromBytes; exportKey, exportSecretKey and exportKeys with ExportMode, armored if the context has setArmor; removeKey.
• Key generation — Crypto.Gpgme.Key.Gen builds the parameter list gpgme expects (key type, length, usage, expiry, passphrase) out of types rather than hand-written strings.
• Callbacks — answer a passphrase request from your own code instead of a pinentry prompt (setPassphraseCallback), and follow slow operations with setProgressCallback.

Every operation runs in a Ctx, a gpgme context bound to a GnuPG home directory. Use withCtx and it is freed for you.

Requirements

The gpgme C library with its headers, and a GnuPG installation:

apt install libgpgme-dev      # Debian, Ubuntu
brew install gpgme            # macOS

Both the gpgme 1.x and 2.x series work. gpgme 2.x additionally needs bindings-gpgme >= 0.2, since gpgme 2.0 dropped the trust item API that older bindings referenced.

Getting started

{-# LANGUAGE OverloadedStrings #-}

import Crypto.Gpgme

main :: IO ()
main = do
    let alicePubFpr = "EAACEB8A"

    -- encrypt for alice, out of bob's keyring
    Just enc <- withCtx "test/bob" "C" OpenPGP $ \bCtx -> do
        Just aPubKey <- getKey bCtx alicePubFpr NoSecret
        either (const Nothing) Just <$> encrypt bCtx [aPubKey] NoFlag "hello"

    -- decrypt as alice, answering the passphrase request in-process rather than
    -- at a pinentry prompt (needs allow-loopback-pinentry in gpg-agent.conf)
    dec <- withCtx "test/alice" "C" OpenPGP $ \aCtx -> do
        setPassphraseCallback aCtx (Just (\_ _ _ -> return (Just "alice123")))
        decrypt aCtx enc

    print dec

withCtx takes the home directory, the locale and the protocol. For one-shot use there are shorthands that build their own context, like encrypt' "test/bob" alicePubFpr "hello".

The test suite doubles as the fullest set of examples: it exercises every operation above against the keyrings in test/.

Documentation

The API docs live on Hackage. For what each underlying call really does, the gpgme manual is the authority — h-gpgme's names follow it closely.

Contributing

Issues and pull requests are welcome. cabal test runs the suite; tests marked NoCi are skipped in CI with --test-options='--pattern=!/NoCi/'. test/README.md describes the test keyrings, and RELEASE.md how a release is cut.

Changelog · License (MIT)