dsse

DSSE, the Dead Simple Signing Envelope that in-toto and Sigstore sign inside, as a Rust crate on its own: no in-toto dependency and no Sigstore dependency.

It's for Rust code that signs or verifies in-toto attestations and other DSSE envelopes and wants the envelope without taking a whole attestation stack along with it.

Quick start

Add it as a pinned dependency of a new project:

cargo new dsse-demo && cd dsse-demo
cargo add dsse@=0.1.5

Then put this in src/main.rs to sign an envelope and verify it:

use dsse::{sign, verify, Ed25519Signer};

fn main() -> Result<(), dsse::Error> {
    // A demo key; load yours from a secret store.
    let signer = Ed25519Signer::from_bytes(&[7u8; 32])?.with_key_id("demo");
    let envelope = sign("application/vnd.in-toto+json", br#"{"a":1}"#, &signer)?;

    // Verify, then read: the payload comes back only from a verified envelope.
    let verified = verify(&envelope, &[&signer.verifier()], 1)?;
    assert_eq!(verified.payload, br#"{"a":1}"#);

    println!("verified {} bytes of {}", verified.payload.len(), verified.payload_type);
    Ok(())
}

cargo run prints verified 7 bytes of application/vnd.in-toto+json.

The signature covers the payload type as well as the payload, so a signature made over one payload type can't be replayed under another.

What it refuses

Six things a permissive implementation accepts: a length prefix that counts characters where DSSE counts bytes, non-canonical base64, an envelope with no signatures, a threshold of zero, a threshold met by one key's signature copied several times, and a key hint used to exclude a key rather than to order the attempts. DSSE's own reference implementation allows four of the six; PROVENANCE.md names the four.

To use a key other than ed25519, such as ECDSA, a KMS or a Sigstore signer, turn off the default ed25519 feature and implement the Signer and Verifier traits.

Status

Version 0.1.5 on crates.io. The rules come from DSSE's specification text at version 1.0.2, and the tests load cross-language fixtures built by the DSSE reference Go implementation, recorded in PROVENANCE.md.

Version 0.1.3 adds optional error serialization. The npm package described in the JavaScript guide has its own version, 0.1.0, and is not yet on the npm registry.

Documentation

License

Apache-2.0.