crates/oxy-core/src/cert.rs at 771661aa50f4 · andymccall/oxygen

# 771661aa50f4 oxygen / crates / oxy-core / src / cert.rs

18.5 KiB · Rust · last changed Grants let certified keys act for an author (keyless step 5a) 19 days ago source blame history raw

//! Certificates for short-lived keys (spec §14.7, oxygenhub#241,
//! oxygenhub docs/keyless.md). An issuer, a hub's key, binds a fresh key
//! to the identity that proved itself (an OIDC subject) for minutes: a Flow
//! job or an agent signs with that key and throws it away. The certificate
//! is signed with the issuer's composite key, so it is post-quantum like
//! every other signature in Oxygen.
//!
//! Whether to trust an issuer, and for which subjects, is the trust
//! policy's (§14.5); whether a signature was made inside the certificate's
//! window needs time the signer does not choose, which the caller passes
//! in (a host's acceptance now, the transparency log's later).

use crate::cbor::{self, Value};
use crate::hash::{hash_object, KeyId, ObjectRef, ObjectType};
use crate::identity::{verify, Domain, Identity, Scope, SecretKey, Signature};
use crate::objects::{array, bytes, check_version, field, map, oref, text, uint, ObjectError};

/// The longest a certificate may be valid. Jobs get ten minutes; an hour
/// leaves room for an issuer that rounds up, and no more.
pub const MAX_LIFETIME_MS: u64 = 60 * 60 * 1000;

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Certificate {
    /// The short-lived key's public identity.
    pub key: Identity,
    /// The issuer's KeyId (a hub's key).
    pub issuer: KeyId,
    /// Who proved it: `repo:OWNER/NAME:bookmark:B`, `agent:NAME@ACCOUNT`.
    pub subject: String,
    /// What else the proof said (environment, run, job), sorted by name.
    pub claims: Vec<(String, String)>,
    /// What the key may sign: changes, refs, seals.
    pub scope: Scope,
    /// Valid from and until, in wall milliseconds.
    pub not_before: u64,
    pub expires: u64,
    /// The grant that lets the subject act for an author, when an agent
    /// asked with one (field 8, only when present).
    pub grant: Option<SignedGrant>,
}

impl Certificate {
    pub fn to_value(&self) -> Value {
        let mut claims = self.claims.clone();
        claims.sort();
        let mut v = Value::map([
            (0, Value::Uint(1)),
            (1, Value::Bytes(self.key.encode())),
            (2, Value::Bytes(self.issuer.0.to_vec())),
            (3, Value::Text(self.subject.clone())),
            (
                4,
                Value::Array(
                    claims
                        .into_iter()
                        .map(|(k, v)| Value::Array(vec![Value::Text(k), Value::Text(v)]))
                        .collect(),
                ),
            ),
            (
                5,
                Value::Array(
                    self.scope
                        .names()
                        .into_iter()
                        .map(|n| Value::Text(n.to_string()))
                        .collect(),
                ),
            ),
            (6, Value::Uint(self.not_before)),
            (7, Value::Uint(self.expires)),
        ]);
        if let (Some(g), Value::Map(m)) = (&self.grant, &mut v) {
            m.insert(8, Value::Bytes(g.encode()));
        }
        v
    }

    pub fn encode(&self) -> Vec<u8> {
        cbor::encode(&self.to_value())
    }

    pub fn hash(&self) -> ObjectRef {
        hash_object(ObjectType::Certificate, &self.encode())
    }

    /// The short-lived key's KeyId: what its signatures name.
    pub fn key_id(&self) -> KeyId {
        self.key.hash()
    }

    pub fn decode(b: &[u8]) -> Result<Certificate, ObjectError> {
        let v = cbor::decode(b)?;
        let m = map(&v, "certificate")?;
        check_version(m)?;
        let key = Identity::decode(bytes(field(m, 1, "key")?, "key")?)?;
        let mut claims = Vec::new();
        for c in array(field(m, 4, "claims")?, "claims")? {
            let pair = array(c, "claim")?;
            if pair.len() != 2 {
                return Err(ObjectError::Schema("claim: expected [name, value]".into()));
            }
            claims.push((
                text(&pair[0], "claim name")?.to_owned(),
                text(&pair[1], "claim value")?.to_owned(),
            ));
        }
        let mut scope = Scope::NONE;
        for n in array(field(m, 5, "scope")?, "scope")? {
            let n = text(n, "scope")?;
            scope = scope
                | Scope::named(n).ok_or_else(|| {
                    ObjectError::Schema(format!("certificate: unknown scope {n:?}"))
                })?;
        }
        Ok(Certificate {
            key,
            issuer: oref(field(m, 2, "issuer")?, "issuer")?,
            subject: text(field(m, 3, "subject")?, "subject")?.to_owned(),
            claims,
            scope,
            not_before: uint(field(m, 6, "not_before")?, "not_before")?,
            expires: uint(field(m, 7, "expires")?, "expires")?,
            grant: match m.get(&8) {
                Some(g) => Some(
                    SignedGrant::decode(bytes(g, "grant")?)
                        .map_err(|e| ObjectError::Schema(format!("grant: {e}")))?,
                ),
                None => None,
            },
        })
    }

    /// Whether the key may sign within `scope` at `at_ms`, a time the
    /// signer did not choose.
    pub fn covers(&self, scope: Scope, at_ms: u64) -> bool {
        !scope.is_empty()
            && self.scope.has(scope)
            && self.not_before <= at_ms
            && at_ms <= self.expires
    }

    /// The claim called `name`, if the certificate has one.
    pub fn claim(&self, name: &str) -> Option<&str> {
        self.claims
            .iter()
            .find(|(k, _)| k == name)
            .map(|(_, v)| v.as_str())
    }
}

/// An author's grant (spec §14.7): it lets the keys an issuer certifies
/// for `subject` act for the author, as a delegate does, without a key of
/// their own. An agent's fresh keys then sign and seal changes in the
/// author's name while the grant lasts; the grant travels inside their
/// certificates, so a verifier needs nothing else. Signed by the author.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Grant {
    /// The author's KeyId, which signs the grant.
    pub grantor: KeyId,
    /// The subject whose certified keys act for it: `agent:NAME@ACCOUNT`.
    pub subject: String,
    /// The issuer whose certificates count.
    pub issuer: KeyId,
    /// What they may do for the author: changes, seal.
    pub scope: Scope,
    /// Valid from and until, in wall milliseconds.
    pub not_before: u64,
    pub expires: u64,
}

impl Grant {
    pub fn to_value(&self) -> Value {
        Value::map([
            (0, Value::Uint(1)),
            (1, Value::Bytes(self.grantor.0.to_vec())),
            (2, Value::Text(self.subject.clone())),
            (3, Value::Bytes(self.issuer.0.to_vec())),
            (
                4,
                Value::Array(
                    self.scope
                        .names()
                        .into_iter()
                        .map(|n| Value::Text(n.to_string()))
                        .collect(),
                ),
            ),
            (5, Value::Uint(self.not_before)),
            (6, Value::Uint(self.expires)),
        ])
    }

    pub fn encode(&self) -> Vec<u8> {
        cbor::encode(&self.to_value())
    }

    pub fn hash(&self) -> ObjectRef {
        hash_object(ObjectType::Grant, &self.encode())
    }

    pub fn decode(b: &[u8]) -> Result<Grant, ObjectError> {
        let v = cbor::decode(b)?;
        let m = map(&v, "grant")?;
        check_version(m)?;
        let mut scope = Scope::NONE;
        for n in array(field(m, 4, "scope")?, "scope")? {
            let n = text(n, "scope")?;
            scope = scope
                | Scope::named(n)
                    .ok_or_else(|| ObjectError::Schema(format!("grant: unknown scope {n:?}")))?;
        }
        Ok(Grant {
            grantor: oref(field(m, 1, "grantor")?, "grantor")?,
            subject: text(field(m, 2, "subject")?, "subject")?.to_owned(),
            issuer: oref(field(m, 3, "issuer")?, "issuer")?,
            scope,
            not_before: uint(field(m, 5, "not_before")?, "not_before")?,
            expires: uint(field(m, 6, "expires")?, "expires")?,
        })
    }

    /// Whether it lets its subject do `scope` for the author at `at_ms`
    /// (the change's own time, as for a delegation).
    pub fn covers(&self, scope: Scope, at_ms: u64) -> bool {
        !scope.is_empty()
            && self.scope.has(scope)
            && self.not_before <= at_ms
            && at_ms <= self.expires
    }
}

/// A grant with its author's signature over its ObjectRef.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct SignedGrant {
    pub grant: Grant,
    pub sig: Signature,
}

impl SignedGrant {
    /// Grant `grant`, signed by the author `grantor` holds the secret of.
    pub fn sign(grant: Grant, grantor: &Identity, sk: &SecretKey) -> SignedGrant {
        let sig = sk.sign(Domain::Grant, &grantor.hash(), &grant.hash());
        SignedGrant { grant, sig }
    }

    /// Signed by `grantor`, which it names, and well formed.
    pub fn verify(&self, grantor: &Identity) -> Result<(), CertError> {
        let g = &self.grant;
        if grantor.hash() != g.grantor || self.sig.key != g.grantor {
            return Err(CertError::WrongIssuer(g.grantor.short(12)));
        }
        verify(grantor, &self.sig, Domain::Grant, &g.hash())
            .map_err(|e| CertError::BadSignature(e.to_string()))?;
        if g.expires <= g.not_before {
            return Err(CertError::BadLifetime);
        }
        if g.scope.is_empty() {
            return Err(CertError::NoScope);
        }
        Ok(())
    }

    /// `[grant bytes, signature]`.
    pub fn encode(&self) -> Vec<u8> {
        cbor::encode(&Value::Array(vec![
            Value::Bytes(self.grant.encode()),
            self.sig.to_value(),
        ]))
    }

    pub fn decode(b: &[u8]) -> Result<SignedGrant, CertError> {
        let v = cbor::decode(b).map_err(ObjectError::from)?;
        let a = array(&v, "signed grant")?;
        if a.len() != 2 {
            return Err(CertError::Schema(
                "signed grant: expected [grant, signature]".into(),
            ));
        }
        Ok(SignedGrant {
            grant: Grant::decode(bytes(&a[0], "grant")?)?,
            sig: Signature::from_value(&a[1])?,
        })
    }
}

/// What a fresh key signs (a challenge, §14.3) to show its holder asks for
/// the certificate: bound to the credential it is asked with, so the
/// proof cannot be replayed with another.
pub fn certify_challenge(credential: &str) -> Vec<u8> {
    let mut c = b"oxy1 certify ".to_vec();
    c.extend_from_slice(blake3::hash(credential.as_bytes()).as_bytes());
    c
}

#[derive(Clone, Debug, PartialEq, Eq, thiserror::Error)]
pub enum CertError {
    #[error("the certificate names issuer {0}, not this one")]
    WrongIssuer(String),
    #[error("the issuer's signature does not verify: {0}")]
    BadSignature(String),
    #[error("the certificate is valid for no time, or for longer than an hour")]
    BadLifetime,
    #[error("the certificate gives no scope")]
    NoScope,
    #[error("{0}")]
    Schema(String),
}

impl From<ObjectError> for CertError {
    fn from(e: ObjectError) -> Self {
        CertError::Schema(e.to_string())
    }
}

/// A certificate with its issuer's signature over its ObjectRef.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct SignedCertificate {
    pub cert: Certificate,
    pub sig: Signature,
}

impl SignedCertificate {
    /// Issue `cert`, signed by the issuer `issuer` holds the secret of.
    pub fn sign(mut cert: Certificate, issuer: &Identity, sk: &SecretKey) -> SignedCertificate {
        // Claims in their canonical order, as encoded.
        cert.claims.sort();
        let sig = sk.sign(Domain::Certificate, &issuer.hash(), &cert.hash());
        SignedCertificate { cert, sig }
    }

    /// Signed by `issuer`, which it names, and well formed. Whether to
    /// trust the issuer for its subject is the policy's question.
    pub fn verify(&self, issuer: &Identity) -> Result<(), CertError> {
        let c = &self.cert;
        if issuer.hash() != c.issuer || self.sig.key != c.issuer {
            return Err(CertError::WrongIssuer(c.issuer.short(12)));
        }
        verify(issuer, &self.sig, Domain::Certificate, &c.hash())
            .map_err(|e| CertError::BadSignature(e.to_string()))?;
        if c.expires <= c.not_before || c.expires - c.not_before > MAX_LIFETIME_MS {
            return Err(CertError::BadLifetime);
        }
        if c.scope.is_empty() {
            return Err(CertError::NoScope);
        }
        Ok(())
    }

    /// `[certificate bytes, signature]`.
    pub fn encode(&self) -> Vec<u8> {
        cbor::encode(&Value::Array(vec![
            Value::Bytes(self.cert.encode()),
            self.sig.to_value(),
        ]))
    }

    pub fn decode(b: &[u8]) -> Result<SignedCertificate, CertError> {
        let v = cbor::decode(b).map_err(ObjectError::from)?;
        let a = array(&v, "signed certificate")?;
        if a.len() != 2 {
            return Err(CertError::Schema(
                "signed certificate: expected [certificate, signature]".into(),
            ));
        }
        Ok(SignedCertificate {
            cert: Certificate::decode(bytes(&a[0], "certificate")?)?,
            sig: Signature::from_value(&a[1])?,
        })
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn issue(
        issuer_sk: &SecretKey,
        issuer: &Identity,
        minutes: u64,
    ) -> (SecretKey, SignedCertificate) {
        let job_sk = SecretKey::generate();
        let cert = Certificate {
            key: job_sk.identity("job 12 build", "[email protected]", 1_000),
            issuer: issuer.hash(),
            subject: "repo:andy/demo:bookmark:main".into(),
            claims: vec![
                ("run".into(), "12".into()),
                ("environment".into(), "prod".into()),
            ],
            scope: Scope::CHANGES | Scope::REFS,
            not_before: 1_000,
            expires: 1_000 + minutes * 60_000,
            grant: None,
        };
        (job_sk, SignedCertificate::sign(cert, issuer, issuer_sk))
    }

    #[test]
    fn a_certificate_round_trips_and_verifies_with_its_issuer_only() {
        let hub_sk = SecretKey::generate();
        let hub = hub_sk.identity("oxygenhub.io", "[email protected]", 1);
        let (_, sc) = issue(&hub_sk, &hub, 10);
        let back = SignedCertificate::decode(&sc.encode()).unwrap();
        assert_eq!(back, sc);
        assert_eq!(back.cert.claims[0].0, "environment", "claims kept sorted");
        assert_eq!(back.cert.claim("run"), Some("12"));
        assert!(back.verify(&hub).is_ok());
        let other_sk = SecretKey::generate();
        let other = other_sk.identity("elsewhere", "[email protected]", 1);
        assert!(matches!(
            back.verify(&other),
            Err(CertError::WrongIssuer(_))
        ));
        // Changed after signing: the signature no longer covers it.
        let mut forged = back.clone();
        forged.cert.subject = "repo:andy/demo:bookmark:release".into();
        assert!(matches!(
            forged.verify(&hub),
            Err(CertError::BadSignature(_))
        ));
        // Signed by another key in the issuer's name.
        let mut stolen = back.clone();
        stolen.sig = other_sk.sign(Domain::Certificate, &hub.hash(), &back.cert.hash());
        assert!(matches!(
            stolen.verify(&hub),
            Err(CertError::BadSignature(_))
        ));
    }

    #[test]
    fn a_grant_rides_in_its_certificate_and_verifies_with_its_author_only() {
        let hub_sk = SecretKey::generate();
        let hub = hub_sk.identity("oxygenhub.io", "[email protected]", 1);
        let ada_sk = SecretKey::generate();
        let ada = ada_sk.identity("Ada", "[email protected]", 1);
        let g = SignedGrant::sign(
            Grant {
                grantor: ada.hash(),
                subject: "agent:claude@ada".into(),
                issuer: hub.hash(),
                scope: Scope::CHANGES | Scope::SEAL,
                not_before: 1_000,
                expires: 2_000,
            },
            &ada,
            &ada_sk,
        );
        assert!(g.verify(&ada).is_ok());
        assert!(g.verify(&hub).is_err(), "only its author's");
        assert!(g.grant.covers(Scope::SEAL, 1_500));
        assert!(!g.grant.covers(Scope::REFS, 1_500));
        assert!(!g.grant.covers(Scope::SEAL, 2_001));
        let (_, plain) = issue(&hub_sk, &hub, 10);
        assert!(
            !matches!(cbor::decode(&plain.cert.encode()).unwrap(), Value::Map(m) if m.contains_key(&8)),
            "no grant, no field 8"
        );
        let mut with = plain.cert.clone();
        with.grant = Some(g.clone());
        let sc = SignedCertificate::sign(with, &hub, &hub_sk);
        let back = SignedCertificate::decode(&sc.encode()).unwrap();
        assert_eq!(back.cert.grant, Some(g));
        assert!(back.verify(&hub).is_ok());
        assert_ne!(back.cert.hash(), plain.cert.hash());
    }

    #[test]
    fn it_covers_its_scope_and_window_only() {
        let hub_sk = SecretKey::generate();
        let hub = hub_sk.identity("oxygenhub.io", "[email protected]", 1);
        let (_, sc) = issue(&hub_sk, &hub, 10);
        let c = &sc.cert;
        assert!(c.covers(Scope::CHANGES, 1_000) && c.covers(Scope::REFS, 1_000 + 10 * 60_000));
        assert!(!c.covers(Scope::SEAL, 2_000), "not a scope it gives");
        assert!(!c.covers(Scope::CHANGES, 999), "before it");
        assert!(
            !c.covers(Scope::CHANGES, 1_000 + 10 * 60_000 + 1),
            "after it"
        );
        assert!(!c.covers(Scope::NONE, 2_000));
        let (_, long) = issue(&hub_sk, &hub, 61);
        assert_eq!(long.verify(&hub), Err(CertError::BadLifetime));
    }

    #[test]
    fn the_proof_of_possession_is_bound_to_its_credential() {
        let sk = SecretKey::generate();
        let id = sk.identity("job", "[email protected]", 1);
        let proof = sk
            .sign_challenge(&id.hash(), &certify_challenge("flowjob_aaa"))
            .unwrap();
        assert!(
            crate::identity::verify_challenge(&id, &proof, &certify_challenge("flowjob_aaa"))
                .is_ok()
        );
        assert!(
            crate::identity::verify_challenge(&id, &proof, &certify_challenge("flowjob_bbb"))
                .is_err()
        );
    }

    #[test]
    fn a_signature_by_the_short_lived_key_names_it() {
        let hub_sk = SecretKey::generate();
        let hub = hub_sk.identity("oxygenhub.io", "[email protected]", 1);
        let (job_sk, sc) = issue(&hub_sk, &hub, 10);
        let target = ObjectRef([5; 32]);
        let sig = job_sk.sign(Domain::Change, &sc.cert.key_id(), &target);
        assert_eq!(sig.key, sc.cert.key_id());
        assert!(verify(&sc.cert.key, &sig, Domain::Change, &target).is_ok());
    }
}

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02e69188 Andy McCall 19 days ago ↶	1	//! Certificates for short-lived keys (spec §14.7, oxygenhub#241,
	2	//! oxygenhub docs/keyless.md). An issuer, a hub's key, binds a fresh key
	3	//! to the identity that proved itself (an OIDC subject) for minutes: a Flow
	4	//! job or an agent signs with that key and throws it away. The certificate
	5	//! is signed with the issuer's composite key, so it is post-quantum like
	6	//! every other signature in Oxygen.
	7	//!
	8	//! Whether to trust an issuer, and for which subjects, is the trust
	9	//! policy's (§14.5); whether a signature was made inside the certificate's
	10	//! window needs time the signer does not choose, which the caller passes
	11	//! in (a host's acceptance now, the transparency log's later).
	12
	13	use crate::cbor::{self, Value};
	14	use crate::hash::{hash_object, KeyId, ObjectRef, ObjectType};
	15	use crate::identity::{verify, Domain, Identity, Scope, SecretKey, Signature};
	16	use crate::objects::{array, bytes, check_version, field, map, oref, text, uint, ObjectError};
	17
	18	/// The longest a certificate may be valid. Jobs get ten minutes; an hour
	19	/// leaves room for an issuer that rounds up, and no more.
	20	pub const MAX_LIFETIME_MS: u64 = 60 * 60 * 1000;
	21
	22	#[derive(Clone, Debug, PartialEq, Eq)]
	23	pub struct Certificate {
	24	/// The short-lived key's public identity.
	25	pub key: Identity,
	26	/// The issuer's KeyId (a hub's key).
	27	pub issuer: KeyId,
	28	/// Who proved it: `repo:OWNER/NAME:bookmark:B`, `agent:NAME@ACCOUNT`.
	29	pub subject: String,
	30	/// What else the proof said (environment, run, job), sorted by name.
	31	pub claims: Vec<(String, String)>,
	32	/// What the key may sign: changes, refs, seals.
	33	pub scope: Scope,
	34	/// Valid from and until, in wall milliseconds.
	35	pub not_before: u64,
	36	pub expires: u64,
a2387d54 Andy McCall 19 days ago ↶	37	/// The grant that lets the subject act for an author, when an agent
	38	/// asked with one (field 8, only when present).
	39	pub grant: Option<SignedGrant>,
02e69188 Andy McCall 19 days ago ↶	40	}
	41
	42	impl Certificate {
	43	pub fn to_value(&self) -> Value {
	44	let mut claims = self.claims.clone();
	45	claims.sort();
a2387d54 Andy McCall 19 days ago ↶	46	let mut v = Value::map([
02e69188 Andy McCall 19 days ago ↶	47	(0, Value::Uint(1)),
	48	(1, Value::Bytes(self.key.encode())),
	49	(2, Value::Bytes(self.issuer.0.to_vec())),
	50	(3, Value::Text(self.subject.clone())),
	51	(
	52	4,
	53	Value::Array(
	54	claims
	55	.into_iter()
	56	.map(\|(k, v)\| Value::Array(vec![Value::Text(k), Value::Text(v)]))
	57	.collect(),
	58	),
	59	),
	60	(
	61	5,
	62	Value::Array(
	63	self.scope
	64	.names()
	65	.into_iter()
	66	.map(\|n\| Value::Text(n.to_string()))
	67	.collect(),
	68	),
	69	),
	70	(6, Value::Uint(self.not_before)),
	71	(7, Value::Uint(self.expires)),
a2387d54 Andy McCall 19 days ago ↶	72	]);
	73	if let (Some(g), Value::Map(m)) = (&self.grant, &mut v) {
	74	m.insert(8, Value::Bytes(g.encode()));
	75	}
	76	v
02e69188 Andy McCall 19 days ago ↶	77	}
	78
	79	pub fn encode(&self) -> Vec<u8> {
	80	cbor::encode(&self.to_value())
	81	}
	82
	83	pub fn hash(&self) -> ObjectRef {
	84	hash_object(ObjectType::Certificate, &self.encode())
	85	}
	86
	87	/// The short-lived key's KeyId: what its signatures name.
	88	pub fn key_id(&self) -> KeyId {
	89	self.key.hash()
	90	}
	91
	92	pub fn decode(b: &[u8]) -> Result<Certificate, ObjectError> {
	93	let v = cbor::decode(b)?;
	94	let m = map(&v, "certificate")?;
	95	check_version(m)?;
	96	let key = Identity::decode(bytes(field(m, 1, "key")?, "key")?)?;
	97	let mut claims = Vec::new();
	98	for c in array(field(m, 4, "claims")?, "claims")? {
	99	let pair = array(c, "claim")?;
	100	if pair.len() != 2 {
	101	return Err(ObjectError::Schema("claim: expected [name, value]".into()));
	102	}
	103	claims.push((
	104	text(&pair[0], "claim name")?.to_owned(),
	105	text(&pair[1], "claim value")?.to_owned(),
	106	));
	107	}
	108	let mut scope = Scope::NONE;
	109	for n in array(field(m, 5, "scope")?, "scope")? {
	110	let n = text(n, "scope")?;
	111	scope = scope
	112	\| Scope::named(n).ok_or_else(\|\| {
	113	ObjectError::Schema(format!("certificate: unknown scope {n:?}"))
	114	})?;
	115	}
	116	Ok(Certificate {
	117	key,
	118	issuer: oref(field(m, 2, "issuer")?, "issuer")?,
	119	subject: text(field(m, 3, "subject")?, "subject")?.to_owned(),
	120	claims,
	121	scope,
	122	not_before: uint(field(m, 6, "not_before")?, "not_before")?,
	123	expires: uint(field(m, 7, "expires")?, "expires")?,
a2387d54 Andy McCall 19 days ago ↶	124	grant: match m.get(&8) {
	125	Some(g) => Some(
	126	SignedGrant::decode(bytes(g, "grant")?)
	127	.map_err(\|e\| ObjectError::Schema(format!("grant: {e}")))?,
	128	),
	129	None => None,
	130	},
02e69188 Andy McCall 19 days ago ↶	131	})
	132	}
	133
	134	/// Whether the key may sign within `scope` at `at_ms`, a time the
	135	/// signer did not choose.
	136	pub fn covers(&self, scope: Scope, at_ms: u64) -> bool {
	137	!scope.is_empty()
	138	&& self.scope.has(scope)
	139	&& self.not_before <= at_ms
	140	&& at_ms <= self.expires
	141	}
	142
	143	/// The claim called `name`, if the certificate has one.
	144	pub fn claim(&self, name: &str) -> Option<&str> {
	145	self.claims
	146	.iter()
	147	.find(\|(k, _)\| k == name)
	148	.map(\|(_, v)\| v.as_str())
	149	}
a2387d54 Andy McCall 19 days ago ↶	150	}
	151
	152	/// An author's grant (spec §14.7): it lets the keys an issuer certifies
	153	/// for `subject` act for the author, as a delegate does, without a key of
	154	/// their own. An agent's fresh keys then sign and seal changes in the
	155	/// author's name while the grant lasts; the grant travels inside their
	156	/// certificates, so a verifier needs nothing else. Signed by the author.
	157	#[derive(Clone, Debug, PartialEq, Eq)]
	158	pub struct Grant {
	159	/// The author's KeyId, which signs the grant.
	160	pub grantor: KeyId,
	161	/// The subject whose certified keys act for it: `agent:NAME@ACCOUNT`.
	162	pub subject: String,
	163	/// The issuer whose certificates count.
	164	pub issuer: KeyId,
	165	/// What they may do for the author: changes, seal.
	166	pub scope: Scope,
	167	/// Valid from and until, in wall milliseconds.
	168	pub not_before: u64,
	169	pub expires: u64,
02e69188 Andy McCall 19 days ago ↶	170	}
a2387d54 Andy McCall 19 days ago ↶	171
	172	impl Grant {
	173	pub fn to_value(&self) -> Value {
	174	Value::map([
	175	(0, Value::Uint(1)),
	176	(1, Value::Bytes(self.grantor.0.to_vec())),
	177	(2, Value::Text(self.subject.clone())),
	178	(3, Value::Bytes(self.issuer.0.to_vec())),
	179	(
	180	4,
	181	Value::Array(
	182	self.scope
	183	.names()
	184	.into_iter()
	185	.map(\|n\| Value::Text(n.to_string()))
	186	.collect(),
	187	),
	188	),
	189	(5, Value::Uint(self.not_before)),
	190	(6, Value::Uint(self.expires)),
	191	])
	192	}
	193
	194	pub fn encode(&self) -> Vec<u8> {
	195	cbor::encode(&self.to_value())
	196	}
	197
	198	pub fn hash(&self) -> ObjectRef {
	199	hash_object(ObjectType::Grant, &self.encode())
	200	}
02e69188 Andy McCall 19 days ago ↶	201
a2387d54 Andy McCall 19 days ago ↶	202	pub fn decode(b: &[u8]) -> Result<Grant, ObjectError> {
	203	let v = cbor::decode(b)?;
	204	let m = map(&v, "grant")?;
	205	check_version(m)?;
	206	let mut scope = Scope::NONE;
	207	for n in array(field(m, 4, "scope")?, "scope")? {
	208	let n = text(n, "scope")?;
	209	scope = scope
	210	\| Scope::named(n)
	211	.ok_or_else(\|\| ObjectError::Schema(format!("grant: unknown scope {n:?}")))?;
	212	}
	213	Ok(Grant {
	214	grantor: oref(field(m, 1, "grantor")?, "grantor")?,
	215	subject: text(field(m, 2, "subject")?, "subject")?.to_owned(),
	216	issuer: oref(field(m, 3, "issuer")?, "issuer")?,
	217	scope,
	218	not_before: uint(field(m, 5, "not_before")?, "not_before")?,
	219	expires: uint(field(m, 6, "expires")?, "expires")?,
	220	})
	221	}
	222
	223	/// Whether it lets its subject do `scope` for the author at `at_ms`
	224	/// (the change's own time, as for a delegation).
	225	pub fn covers(&self, scope: Scope, at_ms: u64) -> bool {
	226	!scope.is_empty()
	227	&& self.scope.has(scope)
	228	&& self.not_before <= at_ms
	229	&& at_ms <= self.expires
	230	}
	231	}
	232
	233	/// A grant with its author's signature over its ObjectRef.
	234	#[derive(Clone, Debug, PartialEq, Eq)]
	235	pub struct SignedGrant {
	236	pub grant: Grant,
	237	pub sig: Signature,
	238	}
	239
	240	impl SignedGrant {
	241	/// Grant `grant`, signed by the author `grantor` holds the secret of.
	242	pub fn sign(grant: Grant, grantor: &Identity, sk: &SecretKey) -> SignedGrant {
	243	let sig = sk.sign(Domain::Grant, &grantor.hash(), &grant.hash());
	244	SignedGrant { grant, sig }
	245	}
	246
	247	/// Signed by `grantor`, which it names, and well formed.
	248	pub fn verify(&self, grantor: &Identity) -> Result<(), CertError> {
	249	let g = &self.grant;
	250	if grantor.hash() != g.grantor \|\| self.sig.key != g.grantor {
	251	return Err(CertError::WrongIssuer(g.grantor.short(12)));
	252	}
	253	verify(grantor, &self.sig, Domain::Grant, &g.hash())
	254	.map_err(\|e\| CertError::BadSignature(e.to_string()))?;
	255	if g.expires <= g.not_before {
	256	return Err(CertError::BadLifetime);
	257	}
	258	if g.scope.is_empty() {
	259	return Err(CertError::NoScope);
	260	}
	261	Ok(())
	262	}
	263
	264	/// `[grant bytes, signature]`.
	265	pub fn encode(&self) -> Vec<u8> {
266	cbor::encode(&Value::Array(vec![
267	Value::Bytes(self.grant.encode()),
268	self.sig.to_value(),
269	]))
270	}
271
272	pub fn decode(b: &[u8]) -> Result<SignedGrant, CertError> {
273	let v = cbor::decode(b).map_err(ObjectError::from)?;
274	let a = array(&v, "signed grant")?;
275	if a.len() != 2 {
276	return Err(CertError::Schema(
277	"signed grant: expected [grant, signature]".into(),
278	));
279	}
280	Ok(SignedGrant {
281	grant: Grant::decode(bytes(&a[0], "grant")?)?,
282	sig: Signature::from_value(&a[1])?,
283	})
284	}
285	}
286
098227d4 Andy McCall 19 days ago ↶	287	/// What a fresh key signs (a challenge, §14.3) to show its holder asks for
	288	/// the certificate: bound to the credential it is asked with, so the
	289	/// proof cannot be replayed with another.
	290	pub fn certify_challenge(credential: &str) -> Vec<u8> {
	291	let mut c = b"oxy1 certify ".to_vec();
	292	c.extend_from_slice(blake3::hash(credential.as_bytes()).as_bytes());
	293	c
	294	}
	295
02e69188 Andy McCall 19 days ago ↶	296	#[derive(Clone, Debug, PartialEq, Eq, thiserror::Error)]
	297	pub enum CertError {
	298	#[error("the certificate names issuer {0}, not this one")]
	299	WrongIssuer(String),
	300	#[error("the issuer's signature does not verify: {0}")]
	301	BadSignature(String),
	302	#[error("the certificate is valid for no time, or for longer than an hour")]
	303	BadLifetime,
	304	#[error("the certificate gives no scope")]
	305	NoScope,
	306	#[error("{0}")]
	307	Schema(String),
	308	}
	309
	310	impl From<ObjectError> for CertError {
	311	fn from(e: ObjectError) -> Self {
	312	CertError::Schema(e.to_string())
	313	}
	314	}
	315
	316	/// A certificate with its issuer's signature over its ObjectRef.
	317	#[derive(Clone, Debug, PartialEq, Eq)]
	318	pub struct SignedCertificate {
	319	pub cert: Certificate,
	320	pub sig: Signature,
	321	}
	322
	323	impl SignedCertificate {
	324	/// Issue `cert`, signed by the issuer `issuer` holds the secret of.
	325	pub fn sign(mut cert: Certificate, issuer: &Identity, sk: &SecretKey) -> SignedCertificate {
	326	// Claims in their canonical order, as encoded.
	327	cert.claims.sort();
	328	let sig = sk.sign(Domain::Certificate, &issuer.hash(), &cert.hash());
	329	SignedCertificate { cert, sig }
	330	}
	331
	332	/// Signed by `issuer`, which it names, and well formed. Whether to
	333	/// trust the issuer for its subject is the policy's question.
	334	pub fn verify(&self, issuer: &Identity) -> Result<(), CertError> {
	335	let c = &self.cert;
	336	if issuer.hash() != c.issuer \|\| self.sig.key != c.issuer {
	337	return Err(CertError::WrongIssuer(c.issuer.short(12)));
	338	}
	339	verify(issuer, &self.sig, Domain::Certificate, &c.hash())
	340	.map_err(\|e\| CertError::BadSignature(e.to_string()))?;
	341	if c.expires <= c.not_before \|\| c.expires - c.not_before > MAX_LIFETIME_MS {
	342	return Err(CertError::BadLifetime);
	343	}
	344	if c.scope.is_empty() {
	345	return Err(CertError::NoScope);
	346	}
	347	Ok(())
	348	}
	349
	350	/// `[certificate bytes, signature]`.
	351	pub fn encode(&self) -> Vec<u8> {
	352	cbor::encode(&Value::Array(vec![
	353	Value::Bytes(self.cert.encode()),
	354	self.sig.to_value(),
	355	]))
	356	}
	357
	358	pub fn decode(b: &[u8]) -> Result<SignedCertificate, CertError> {
	359	let v = cbor::decode(b).map_err(ObjectError::from)?;
360	let a = array(&v, "signed certificate")?;
361	if a.len() != 2 {
362	return Err(CertError::Schema(
363	"signed certificate: expected [certificate, signature]".into(),
364	));
365	}
366	Ok(SignedCertificate {
367	cert: Certificate::decode(bytes(&a[0], "certificate")?)?,
368	sig: Signature::from_value(&a[1])?,
369	})
370	}
371	}
372
373	#[cfg(test)]
374	mod tests {
375	use super::*;
376
377	fn issue(
378	issuer_sk: &SecretKey,
379	issuer: &Identity,
380	minutes: u64,
381	) -> (SecretKey, SignedCertificate) {
382	let job_sk = SecretKey::generate();
383	let cert = Certificate {
384	key: job_sk.identity("job 12 build", "[email protected]", 1_000),
385	issuer: issuer.hash(),
386	subject: "repo:andy/demo:bookmark:main".into(),
387	claims: vec![
388	("run".into(), "12".into()),
389	("environment".into(), "prod".into()),
390	],
391	scope: Scope::CHANGES \| Scope::REFS,
392	not_before: 1_000,
393	expires: 1_000 + minutes * 60_000,
a2387d54 Andy McCall 19 days ago ↶	394	grant: None,
02e69188 Andy McCall 19 days ago ↶	395	};
	396	(job_sk, SignedCertificate::sign(cert, issuer, issuer_sk))
	397	}
	398
	399	#[test]
	400	fn a_certificate_round_trips_and_verifies_with_its_issuer_only() {
	401	let hub_sk = SecretKey::generate();
	402	let hub = hub_sk.identity("oxygenhub.io", "[email protected]", 1);
	403	let (_, sc) = issue(&hub_sk, &hub, 10);
	404	let back = SignedCertificate::decode(&sc.encode()).unwrap();
	405	assert_eq!(back, sc);
	406	assert_eq!(back.cert.claims[0].0, "environment", "claims kept sorted");
	407	assert_eq!(back.cert.claim("run"), Some("12"));
	408	assert!(back.verify(&hub).is_ok());
	409	let other_sk = SecretKey::generate();
	410	let other = other_sk.identity("elsewhere", "[email protected]", 1);
	411	assert!(matches!(
	412	back.verify(&other),
	413	Err(CertError::WrongIssuer(_))
	414	));
	415	// Changed after signing: the signature no longer covers it.
	416	let mut forged = back.clone();
	417	forged.cert.subject = "repo:andy/demo:bookmark:release".into();
	418	assert!(matches!(
	419	forged.verify(&hub),
	420	Err(CertError::BadSignature(_))
	421	));
	422	// Signed by another key in the issuer's name.
	423	let mut stolen = back.clone();
	424	stolen.sig = other_sk.sign(Domain::Certificate, &hub.hash(), &back.cert.hash());
	425	assert!(matches!(
	426	stolen.verify(&hub),
	427	Err(CertError::BadSignature(_))
	428	));
a2387d54 Andy McCall 19 days ago ↶	429	}
	430
	431	#[test]
	432	fn a_grant_rides_in_its_certificate_and_verifies_with_its_author_only() {
	433	let hub_sk = SecretKey::generate();
	434	let hub = hub_sk.identity("oxygenhub.io", "[email protected]", 1);
	435	let ada_sk = SecretKey::generate();
	436	let ada = ada_sk.identity("Ada", "[email protected]", 1);
	437	let g = SignedGrant::sign(
	438	Grant {
	439	grantor: ada.hash(),
	440	subject: "agent:claude@ada".into(),
	441	issuer: hub.hash(),
	442	scope: Scope::CHANGES \| Scope::SEAL,
	443	not_before: 1_000,
	444	expires: 2_000,
	445	},
	446	&ada,
	447	&ada_sk,
	448	);
	449	assert!(g.verify(&ada).is_ok());
	450	assert!(g.verify(&hub).is_err(), "only its author's");
	451	assert!(g.grant.covers(Scope::SEAL, 1_500));
	452	assert!(!g.grant.covers(Scope::REFS, 1_500));
	453	assert!(!g.grant.covers(Scope::SEAL, 2_001));
	454	let (_, plain) = issue(&hub_sk, &hub, 10);
	455	assert!(
	456	!matches!(cbor::decode(&plain.cert.encode()).unwrap(), Value::Map(m) if m.contains_key(&8)),
	457	"no grant, no field 8"
	458	);
	459	let mut with = plain.cert.clone();
	460	with.grant = Some(g.clone());
	461	let sc = SignedCertificate::sign(with, &hub, &hub_sk);
	462	let back = SignedCertificate::decode(&sc.encode()).unwrap();
	463	assert_eq!(back.cert.grant, Some(g));
	464	assert!(back.verify(&hub).is_ok());
	465	assert_ne!(back.cert.hash(), plain.cert.hash());
02e69188 Andy McCall 19 days ago ↶	466	}
	467
	468	#[test]
	469	fn it_covers_its_scope_and_window_only() {
	470	let hub_sk = SecretKey::generate();
	471	let hub = hub_sk.identity("oxygenhub.io", "[email protected]", 1);
	472	let (_, sc) = issue(&hub_sk, &hub, 10);
	473	let c = &sc.cert;
	474	assert!(c.covers(Scope::CHANGES, 1_000) && c.covers(Scope::REFS, 1_000 + 10 * 60_000));
	475	assert!(!c.covers(Scope::SEAL, 2_000), "not a scope it gives");
	476	assert!(!c.covers(Scope::CHANGES, 999), "before it");
	477	assert!(
	478	!c.covers(Scope::CHANGES, 1_000 + 10 * 60_000 + 1),
	479	"after it"
	480	);
	481	assert!(!c.covers(Scope::NONE, 2_000));
	482	let (_, long) = issue(&hub_sk, &hub, 61);
	483	assert_eq!(long.verify(&hub), Err(CertError::BadLifetime));
098227d4 Andy McCall 19 days ago ↶	484	}
	485
	486	#[test]
	487	fn the_proof_of_possession_is_bound_to_its_credential() {
	488	let sk = SecretKey::generate();
	489	let id = sk.identity("job", "[email protected]", 1);
	490	let proof = sk
	491	.sign_challenge(&id.hash(), &certify_challenge("flowjob_aaa"))
	492	.unwrap();
	493	assert!(
	494	crate::identity::verify_challenge(&id, &proof, &certify_challenge("flowjob_aaa"))
	495	.is_ok()
	496	);
	497	assert!(
	498	crate::identity::verify_challenge(&id, &proof, &certify_challenge("flowjob_bbb"))
	499	.is_err()
	500	);
02e69188 Andy McCall 19 days ago ↶	501	}
	502
	503	#[test]
	504	fn a_signature_by_the_short_lived_key_names_it() {
	505	let hub_sk = SecretKey::generate();
	506	let hub = hub_sk.identity("oxygenhub.io", "[email protected]", 1);
	507	let (job_sk, sc) = issue(&hub_sk, &hub, 10);
	508	let target = ObjectRef([5; 32]);
	509	let sig = job_sk.sign(Domain::Change, &sc.cert.key_id(), &target);
	510	assert_eq!(sig.key, sc.cert.key_id());
	511	assert!(verify(&sc.cert.key, &sig, Domain::Change, &target).is_ok());
	512	}
	513	}

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