An implementation of EAT Attestation Results token.

This crate provides an implementation of attestation results tokens that conforms to EAT Attestation Results draft-fv-rats-ear specification. This defines a token intended to communicate a set of appraisals of attested evidence produced by a verifier. Each appraisal is based around a set of trust claims defined by Attestation Results for Secure Interactions (AR4SI) draft-ietf-rats-ar4si.

The attestation result may be serialized as a signed JSON or CBOR token (using JWT and COSE, respectively).

Examples

Signing

use std::collections::BTreeMap;
use ear::{Ear, VerifierID, Algorithm, Appraisal, Extensions};

const SIGNING_KEY: &str = "-----BEGIN PRIVATE KEY-----
MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgPp4XZRnRHSMhGg0t
6yjQCRV35J4TUY4idLgiCu6EyLqhRANCAAQbx8C533c2AKDwL/RtjVipVnnM2WRv
5w2wZNCJrubSK0StYKJ71CikDgkhw8M90ojfRIowqpl0uLA3kW3PEZy9
-----END PRIVATE KEY-----
";

fn main() {
    let token = Ear{
        profile: "test".to_string(),
        iat: 1,
        vid: VerifierID {
            build: "vsts 0.0.1".to_string(),
            developer: "https://veraison-project.org".to_string(),
        },
        raw_evidence: None,
        nonce: None,
        submods: BTreeMap::from([("test".to_string(), Appraisal::new())]),
        extensions: Extensions::new(),
    };

    let signed = token.sign_jwt_pem(Algorithm::ES256, SIGNING_KEY.as_bytes()).unwrap();
}

Verification

use ear::{Ear, Algorithm};

const VERIF_KEY: &str = r#"
{
    "kty":"EC",
    "crv":"P-256",
    "x":"G8fAud93NgCg8C_0bY1YqVZ5zNlkb-cNsGTQia7m0is",
    "y":"RK1gonvUKKQOCSHDwz3SiN9EijCqmXS4sDeRbc8RnL0"
}
"#;

fn main() {
    let signed = "eyJ0eXAiOiJKV1QiLCJhbGciOiJFUzI1NiJ9.eyJlYXRfcHJvZmlsZSI6InRlc3QiLCJpYXQiOjEsImVhci52ZXJpZmllci1pZCI6eyJkZXZlbG9wZXIiOiJodHRwczovL3ZlcmFpc29uLXByb2plY3Qub3JnIiwiYnVpbGQiOiJ2c3RzIDAuMC4xIn0sInN1Ym1vZHMiOnsidGVzdCI6eyJlYXIuc3RhdHVzIjoibm9uZSJ9fX0.G25v0j0NDQhSOcK3Jtfq5vqVxnoWuWf-Q0DCNkCwpyB03DGr25ZDJ3IDSAHVPZrr6TVMwj8RcGEzQnCrucem4Q";

    let token = Ear::from_jwt_jwk(signed, Algorithm::ES256, VERIF_KEY.as_bytes()).unwrap();
    println!("EAR profiles: {}", token.profile);
}

Extensions and Profiles

EAR supports extension at top level (i.e. within the [Ear] struct), and also within [Appraisal]s. An extension is an additional field definition. Extensions can be defined by registering them with the extensions field of the corresponding struct. When registering an extension, you must provide a string name (used in JSON), an integer key (used in CBOR), and an [ExtensionKind] indicating which [ExtensionValue]s are valid.

Registering individual extensions

Extensions can be registered directly with the corresponding struct's extensions field. Once they have been registered, their values can be set and queried

use ear::{Ear, Appraisal, ExtensionKind, ExtensionValue};

let mut ear = Ear::new();
ear.extensions.register("ext.company-name", -65537, ExtensionKind::String).unwrap();

let mut appraisal = Appraisal::new();
// extensions for Ear's and Appraisal's have their own namespaces, so it is
// to use the same key in both.
appraisal.extensions.register("ext.timestamp", -65537, ExtensionKind::Integer).unwrap();

ear.extensions.set_by_name(
    "ext.company-name",
    ExtensionValue::String("Acme Inc.".to_string()),
).unwrap();

appraisal.extensions.set_by_key(
    -65537,
    ExtensionValue::Integer(1723534859),
).unwrap();

ear.submods.insert("road-runner-trap".to_string(), appraisal);

assert_eq!(
   ear.extensions.get_by_key(&-65537).unwrap(),
   ExtensionValue::String("Acme Inc.".to_string()),
);

assert_eq!(
   ear.submods["road-runner-trap"].extensions.get_by_name("ext.timestamp").unwrap(),
   ExtensionValue::Integer(1723534859),
);

Note: if you've obtained the [Ear] by deserializing from CBOR/JSON, [Extensions] struct will cache any values for any unexpected fields, so that when you register extensions afterwards, the corresponding unmarshaled values will be accessible.

Using Profiles

Sets of extensions can be associated together within [Profile]s. A [Profile] can be registered, and can then be retrieved by its id when creating a new [Ear] or [Appraisal]

use ear::{Ear, Appraisal, ExtensionKind, ExtensionValue, Profile, register_profile};

fn init_profile() {
    let mut profile = Profile::new("tag:github.com,2023:veraison/ear#acme-profile");

    profile.register_ear_extension(
        "ext.company-name", -65537, ExtensionKind::String).unwrap();
    profile.register_appraisal_extension(
        "ext.timestamp", -65537, ExtensionKind::Integer).unwrap();

    register_profile(&profile);
}

fn main() {
    init_profile();

    let mut ear = Ear::new_with_profile(
        "tag:github.com,2023:veraison/ear#acme-profile").unwrap();
    // these will apply to all submods/appraisals within a profiled EAR
    let mut appraisal = Appraisal::new_with_profile(
        "tag:github.com,2023:veraison/ear#acme-profile").unwrap();

    ear.extensions.set_by_name(
        "ext.company-name",
        ExtensionValue::String("Acme Inc.".to_string()),
    ).unwrap();

    appraisal.extensions.set_by_key(
        -65537,
        ExtensionValue::Integer(1723534859),
    ).unwrap();

    ear.submods.insert("road-runner-trap".to_string(), appraisal);

    assert_eq!(
       ear.extensions.get_by_key(&-65537).unwrap(),
       ExtensionValue::String("Acme Inc.".to_string()),
    );

    assert_eq!(
       ear.submods["road-runner-trap"]
            .extensions.get_by_name("ext.timestamp").unwrap(),
       ExtensionValue::Integer(1723534859),
    );
}

When deserializing an [Ear], its profile field will automatically be used to look up a registred profile and add the associated extensions.

JWT/CWT common claims

The only common JWT/CWT claim specified by EAR spec is "iat" (issued at). Other claims (e.g. "iss" or "exp") are not expected to be present inside a valid EAR. It is, however, possible to define them for a particular profile and include them as extensions via mechanisms described above.

The following example shows how to include and then verify expiration time ("exp" JWT claim) inside an EAR.

use ear::{Ear, Algorithm, Appraisal, ExtensionKind, ExtensionValue};
use std::time::{SystemTime, Duration, UNIX_EPOCH};

const VERIF_KEY: &str = r#"
{
    "kty":"EC",
    "crv":"P-256",
    "x":"G8fAud93NgCg8C_0bY1YqVZ5zNlkb-cNsGTQia7m0is",
    "y":"RK1gonvUKKQOCSHDwz3SiN9EijCqmXS4sDeRbc8RnL0"
}
"#;

const SIGNING_KEY: &str = "-----BEGIN PRIVATE KEY-----
MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgPp4XZRnRHSMhGg0t
6yjQCRV35J4TUY4idLgiCu6EyLqhRANCAAQbx8C533c2AKDwL/RtjVipVnnM2WRv
5w2wZNCJrubSK0StYKJ71CikDgkhw8M90ojfRIowqpl0uLA3kW3PEZy9
-----END PRIVATE KEY-----
";

let mut ear = Ear::new();
ear.profile = "tag:github.com,2023:veraison/ear#acme-profile".to_string();
ear.vid.build = "vsts 0.0.1".to_string();
ear.vid.developer = "https://veraison-project.org".to_string();
ear.submods.insert("road-runner-trap".to_string(), Appraisal::new());
ear.extensions.register("exp", 4, ExtensionKind::Integer).unwrap();

// expire 10 days from now
let exp = SystemTime::now().checked_add(Duration::from_secs(60*60*24*10)).unwrap()
                        .duration_since(UNIX_EPOCH).unwrap().as_secs() as i64;

ear.extensions.set_by_name("exp", ExtensionValue::Integer(exp)).unwrap();


let signed = ear
    .sign_jwt_pem(Algorithm::ES256, SIGNING_KEY.as_bytes())
    .unwrap();

let mut ear2 =
    Ear::from_jwt_jwk(signed.as_str(), Algorithm::ES256, VERIF_KEY.as_bytes()).unwrap();

ear2.extensions.register("exp", 4, ExtensionKind::Integer).unwrap();

// Verify the token has not expired.
let exp2 = match ear2.extensions.get_by_name("exp").unwrap() {
    ExtensionValue::Integer(v) => Duration::from_secs(v as u64),
    _ => panic!(),
};
assert!(SystemTime::now().duration_since(UNIX_EPOCH).unwrap() < exp2);

JWT/CWT headers

When signing with sign_jwt_pem/sign_jwk_der, only the alg header is set in the resulting JWT based on the the specified algorithm. If other headers need to be specified, then sign_jwt_pem_with_header and sign_jwk_der_with_header can be used instead; these take a jwt::Header instead of an algorithm. A new header can be created from an algorithm using new_jwt_header.

The same goes when signing as COSE_Sign1Message. Only alg header is set by default, however, _with_header signing methods can be used to specify a custom cose::headers::CoseHeader, which can be reating from an algorithm using new_cwt_header.

use std::collections::BTreeMap;
use ear::{Ear, VerifierID, Algorithm, Appraisal, Extensions, new_jwt_header, new_cose_header};

const SIGNING_KEY: &str = "-----BEGIN PRIVATE KEY-----
MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgPp4XZRnRHSMhGg0t
6yjQCRV35J4TUY4idLgiCu6EyLqhRANCAAQbx8C533c2AKDwL/RtjVipVnnM2WRv
5w2wZNCJrubSK0StYKJ71CikDgkhw8M90ojfRIowqpl0uLA3kW3PEZy9
-----END PRIVATE KEY-----
";

fn main() {
    let token = Ear{
        profile: "test".to_string(),
        iat: 1,
        vid: VerifierID {
            build: "vsts 0.0.1".to_string(),
            developer: "https://veraison-project.org".to_string(),
        },
        raw_evidence: None,
        nonce: None,
        submods: BTreeMap::from([("test".to_string(), Appraisal::new())]),
        extensions: Extensions::new(),
    };

    // JWT

    let mut jwt_header = new_jwt_header(&Algorithm::ES256).unwrap();
    // set additional header(s)
    jwt_header.kid = Some("key-ident".to_string());

    let signed_jwt = token.sign_jwt_pem_with_header(&jwt_header, SIGNING_KEY.as_bytes()).unwrap();
    // CWT

    let mut cwt_header = new_cose_header(&Algorithm::ES256).unwrap();
    // set additional header(s)
    cwt_header.kid("key-ident".as_bytes().to_vec(), true, false);

    let signed_cwt = token.sign_cose_pem_with_header(cwt_header, SIGNING_KEY.as_bytes()).unwrap();
}

Limitations

• Signing supports PEM and DER keys; verification currently only supports JWK keys.
• JWT signing currently only supports ES256, ES384, EdDSA, PS256, PS384, and PS512.
• COSE signing currently only supports ES256, ES384, ES512, and EdDSA.