gpgrv is a Rust library for verifying some types of GPG signatures.

use std::io::{stdin, stdout, BufReader, Cursor, Seek, SeekFrom};
fn main() {
    // load a keyring from some file(s)
    // for example, we use the linux distribution keyring
    let mut keyring = gpgrv::Keyring::new();
    let keyring_file = Cursor::new(distro_keyring::supported_keys());
    keyring.append_keys_from(keyring_file).unwrap();

    // read stdin, verify, and write the output to a temporary file
    let mut temp = tempfile::tempfile().unwrap();
    gpgrv::verify_message(BufReader::new(stdin()), &mut temp, &keyring).expect("verification");

    // if we succeeded, print the temporary file to stdout
    temp.seek(SeekFrom::Start(0)).unwrap();
    std::io::copy(&mut temp, &mut stdout()).unwrap();
}

• Verifying signatures:
  • RSA
  • SHA1 and SHA2 (SHA-256, SHA-512).
• Signed "inline" messages, and detached signatures.
• Armoured and unarmoured/binary.
• Compression wrappers (added by gpg for most messages)
• Loading old-style keyrings (i.e. not keybox files)

• Entirely safe Rust, no native code. Easy to build and portable.
• MIT (or Apache2, or whatever!) licensed, not LGPL.
• Simple, Rust-style API on streams (Read/Write).

• A tiny amount of custom, low-risk crypto code. However, any crypto code can be wrong.
• Limited, but growing, support for key and data formats.
• (Intentionally) not constant time: Cannot be used for certain crypto applications. This is less important for signature verification with public keys.

• gpgme (LGPL) - bindings for native code, verbose API
• rpgp (MIT/Apache2) - serious implementation of plenty of pgp
• sequoia-openpgp (GPLv3) - serious implementation of plenty of pgp

I was using the the gpgme API, which works, but the API is painful, and the linking/requirements are complicated.

sequoia's license is wrong.

rpgp has too many features, although it does seem to be nicely split into crates.

Licensed under either of

• Apache License, Version 2.0
• MIT license

at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.