crates/oxy-core/src/cert.rs at 2aa1854b0d13 · andymccall/oxygen

# 2aa1854b0d13 oxygen / crates / oxy-core / src / cert.rs

18.5 KiB · Rust · last changed Trusted time: judge a fetched attestation at its integrated time 18 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 (the transparency log's integrated time, §14.8, else a host's
//! acceptance).

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());
    }
}

`/`	Search
`g` `c`	Code
`g` `h`	History
`g` `b`	Bookmarks
`g` `t`	Trust
`y`	Permalink to this state (files and trees)
`?`	This sheet

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
028545df Andy McCall 18 days ago ↶	11	//! in (the transparency log's integrated time, §14.8, else a host's
028545df Andy McCall 18 days ago ↶	12	//! acceptance).
02e69188 Andy McCall 19 days ago ↶	13
	14	use crate::cbor::{self, Value};
	15	use crate::hash::{hash_object, KeyId, ObjectRef, ObjectType};
	16	use crate::identity::{verify, Domain, Identity, Scope, SecretKey, Signature};
	17	use crate::objects::{array, bytes, check_version, field, map, oref, text, uint, ObjectError};
	18
	19	/// The longest a certificate may be valid. Jobs get ten minutes; an hour
	20	/// leaves room for an issuer that rounds up, and no more.
	21	pub const MAX_LIFETIME_MS: u64 = 60 * 60 * 1000;
	22
	23	#[derive(Clone, Debug, PartialEq, Eq)]
	24	pub struct Certificate {
	25	/// The short-lived key's public identity.
	26	pub key: Identity,
	27	/// The issuer's KeyId (a hub's key).
	28	pub issuer: KeyId,
	29	/// Who proved it: `repo:OWNER/NAME:bookmark:B`, `agent:NAME@ACCOUNT`.
	30	pub subject: String,
	31	/// What else the proof said (environment, run, job), sorted by name.
	32	pub claims: Vec<(String, String)>,
	33	/// What the key may sign: changes, refs, seals.
	34	pub scope: Scope,
	35	/// Valid from and until, in wall milliseconds.
	36	pub not_before: u64,
	37	pub expires: u64,
a2387d54 Andy McCall 19 days ago ↶	38	/// The grant that lets the subject act for an author, when an agent
	39	/// asked with one (field 8, only when present).
	40	pub grant: Option<SignedGrant>,
02e69188 Andy McCall 19 days ago ↶	41	}
	42
	43	impl Certificate {
	44	pub fn to_value(&self) -> Value {
	45	let mut claims = self.claims.clone();
	46	claims.sort();
a2387d54 Andy McCall 19 days ago ↶	47	let mut v = Value::map([
02e69188 Andy McCall 19 days ago ↶	48	(0, Value::Uint(1)),
	49	(1, Value::Bytes(self.key.encode())),
	50	(2, Value::Bytes(self.issuer.0.to_vec())),
	51	(3, Value::Text(self.subject.clone())),
	52	(
	53	4,
	54	Value::Array(
	55	claims
	56	.into_iter()
	57	.map(\|(k, v)\| Value::Array(vec![Value::Text(k), Value::Text(v)]))
	58	.collect(),
	59	),
	60	),
	61	(
	62	5,
	63	Value::Array(
	64	self.scope
	65	.names()
	66	.into_iter()
	67	.map(\|n\| Value::Text(n.to_string()))
	68	.collect(),
	69	),
	70	),
	71	(6, Value::Uint(self.not_before)),
	72	(7, Value::Uint(self.expires)),
a2387d54 Andy McCall 19 days ago ↶	73	]);
	74	if let (Some(g), Value::Map(m)) = (&self.grant, &mut v) {
	75	m.insert(8, Value::Bytes(g.encode()));
	76	}
	77	v
02e69188 Andy McCall 19 days ago ↶	78	}
	79
	80	pub fn encode(&self) -> Vec<u8> {
	81	cbor::encode(&self.to_value())
	82	}
	83
	84	pub fn hash(&self) -> ObjectRef {
	85	hash_object(ObjectType::Certificate, &self.encode())
	86	}
	87
	88	/// The short-lived key's KeyId: what its signatures name.
	89	pub fn key_id(&self) -> KeyId {
	90	self.key.hash()
	91	}
	92
	93	pub fn decode(b: &[u8]) -> Result<Certificate, ObjectError> {
	94	let v = cbor::decode(b)?;
	95	let m = map(&v, "certificate")?;
	96	check_version(m)?;
	97	let key = Identity::decode(bytes(field(m, 1, "key")?, "key")?)?;
	98	let mut claims = Vec::new();
	99	for c in array(field(m, 4, "claims")?, "claims")? {
	100	let pair = array(c, "claim")?;
	101	if pair.len() != 2 {
	102	return Err(ObjectError::Schema("claim: expected [name, value]".into()));
	103	}
	104	claims.push((
	105	text(&pair[0], "claim name")?.to_owned(),
	106	text(&pair[1], "claim value")?.to_owned(),
	107	));
	108	}
	109	let mut scope = Scope::NONE;
	110	for n in array(field(m, 5, "scope")?, "scope")? {
	111	let n = text(n, "scope")?;
	112	scope = scope
	113	\| Scope::named(n).ok_or_else(\|\| {
	114	ObjectError::Schema(format!("certificate: unknown scope {n:?}"))
	115	})?;
	116	}
	117	Ok(Certificate {
	118	key,
	119	issuer: oref(field(m, 2, "issuer")?, "issuer")?,
	120	subject: text(field(m, 3, "subject")?, "subject")?.to_owned(),
	121	claims,
	122	scope,
	123	not_before: uint(field(m, 6, "not_before")?, "not_before")?,
	124	expires: uint(field(m, 7, "expires")?, "expires")?,
a2387d54 Andy McCall 19 days ago ↶	125	grant: match m.get(&8) {
	126	Some(g) => Some(
	127	SignedGrant::decode(bytes(g, "grant")?)
	128	.map_err(\|e\| ObjectError::Schema(format!("grant: {e}")))?,
	129	),
	130	None => None,
	131	},
02e69188 Andy McCall 19 days ago ↶	132	})
	133	}
	134
	135	/// Whether the key may sign within `scope` at `at_ms`, a time the
	136	/// signer did not choose.
	137	pub fn covers(&self, scope: Scope, at_ms: u64) -> bool {
	138	!scope.is_empty()
	139	&& self.scope.has(scope)
	140	&& self.not_before <= at_ms
	141	&& at_ms <= self.expires
	142	}
	143
	144	/// The claim called `name`, if the certificate has one.
	145	pub fn claim(&self, name: &str) -> Option<&str> {
	146	self.claims
	147	.iter()
	148	.find(\|(k, _)\| k == name)
	149	.map(\|(_, v)\| v.as_str())
	150	}
a2387d54 Andy McCall 19 days ago ↶	151	}
	152
	153	/// An author's grant (spec §14.7): it lets the keys an issuer certifies
	154	/// for `subject` act for the author, as a delegate does, without a key of
	155	/// their own. An agent's fresh keys then sign and seal changes in the
	156	/// author's name while the grant lasts; the grant travels inside their
	157	/// certificates, so a verifier needs nothing else. Signed by the author.
	158	#[derive(Clone, Debug, PartialEq, Eq)]
	159	pub struct Grant {
	160	/// The author's KeyId, which signs the grant.
	161	pub grantor: KeyId,
	162	/// The subject whose certified keys act for it: `agent:NAME@ACCOUNT`.
	163	pub subject: String,
	164	/// The issuer whose certificates count.
	165	pub issuer: KeyId,
	166	/// What they may do for the author: changes, seal.
	167	pub scope: Scope,
	168	/// Valid from and until, in wall milliseconds.
	169	pub not_before: u64,
	170	pub expires: u64,
02e69188 Andy McCall 19 days ago ↶	171	}
a2387d54 Andy McCall 19 days ago ↶	172
	173	impl Grant {
	174	pub fn to_value(&self) -> Value {
	175	Value::map([
	176	(0, Value::Uint(1)),
	177	(1, Value::Bytes(self.grantor.0.to_vec())),
	178	(2, Value::Text(self.subject.clone())),
	179	(3, Value::Bytes(self.issuer.0.to_vec())),
	180	(
	181	4,
	182	Value::Array(
	183	self.scope
	184	.names()
	185	.into_iter()
	186	.map(\|n\| Value::Text(n.to_string()))
	187	.collect(),
	188	),
	189	),
	190	(5, Value::Uint(self.not_before)),
	191	(6, Value::Uint(self.expires)),
	192	])
	193	}
	194
	195	pub fn encode(&self) -> Vec<u8> {
	196	cbor::encode(&self.to_value())
	197	}
	198
	199	pub fn hash(&self) -> ObjectRef {
	200	hash_object(ObjectType::Grant, &self.encode())
	201	}
02e69188 Andy McCall 19 days ago ↶	202
a2387d54 Andy McCall 19 days ago ↶	203	pub fn decode(b: &[u8]) -> Result<Grant, ObjectError> {
	204	let v = cbor::decode(b)?;
	205	let m = map(&v, "grant")?;
	206	check_version(m)?;
	207	let mut scope = Scope::NONE;
	208	for n in array(field(m, 4, "scope")?, "scope")? {
	209	let n = text(n, "scope")?;
	210	scope = scope
	211	\| Scope::named(n)
	212	.ok_or_else(\|\| ObjectError::Schema(format!("grant: unknown scope {n:?}")))?;
	213	}
	214	Ok(Grant {
	215	grantor: oref(field(m, 1, "grantor")?, "grantor")?,
	216	subject: text(field(m, 2, "subject")?, "subject")?.to_owned(),
	217	issuer: oref(field(m, 3, "issuer")?, "issuer")?,
	218	scope,
	219	not_before: uint(field(m, 5, "not_before")?, "not_before")?,
	220	expires: uint(field(m, 6, "expires")?, "expires")?,
	221	})
	222	}
	223
	224	/// Whether it lets its subject do `scope` for the author at `at_ms`
	225	/// (the change's own time, as for a delegation).
	226	pub fn covers(&self, scope: Scope, at_ms: u64) -> bool {
	227	!scope.is_empty()
	228	&& self.scope.has(scope)
	229	&& self.not_before <= at_ms
	230	&& at_ms <= self.expires
	231	}
	232	}
	233
	234	/// A grant with its author's signature over its ObjectRef.
	235	#[derive(Clone, Debug, PartialEq, Eq)]
	236	pub struct SignedGrant {
	237	pub grant: Grant,
	238	pub sig: Signature,
	239	}
	240
	241	impl SignedGrant {
	242	/// Grant `grant`, signed by the author `grantor` holds the secret of.
	243	pub fn sign(grant: Grant, grantor: &Identity, sk: &SecretKey) -> SignedGrant {
	244	let sig = sk.sign(Domain::Grant, &grantor.hash(), &grant.hash());
	245	SignedGrant { grant, sig }
	246	}
	247
	248	/// Signed by `grantor`, which it names, and well formed.
	249	pub fn verify(&self, grantor: &Identity) -> Result<(), CertError> {
	250	let g = &self.grant;
	251	if grantor.hash() != g.grantor \|\| self.sig.key != g.grantor {
	252	return Err(CertError::WrongIssuer(g.grantor.short(12)));
	253	}
	254	verify(grantor, &self.sig, Domain::Grant, &g.hash())
	255	.map_err(\|e\| CertError::BadSignature(e.to_string()))?;
	256	if g.expires <= g.not_before {
	257	return Err(CertError::BadLifetime);
	258	}
	259	if g.scope.is_empty() {
	260	return Err(CertError::NoScope);
	261	}
	262	Ok(())
	263	}
	264
	265	/// `[grant bytes, signature]`.
	266	pub fn encode(&self) -> Vec<u8> {
267	cbor::encode(&Value::Array(vec![
268	Value::Bytes(self.grant.encode()),
269	self.sig.to_value(),
270	]))
271	}
272
273	pub fn decode(b: &[u8]) -> Result<SignedGrant, CertError> {
274	let v = cbor::decode(b).map_err(ObjectError::from)?;
275	let a = array(&v, "signed grant")?;
276	if a.len() != 2 {
277	return Err(CertError::Schema(
278	"signed grant: expected [grant, signature]".into(),
279	));
280	}
281	Ok(SignedGrant {
282	grant: Grant::decode(bytes(&a[0], "grant")?)?,
283	sig: Signature::from_value(&a[1])?,
284	})
285	}
286	}
287
098227d4 Andy McCall 19 days ago ↶	288	/// What a fresh key signs (a challenge, §14.3) to show its holder asks for
	289	/// the certificate: bound to the credential it is asked with, so the
	290	/// proof cannot be replayed with another.
	291	pub fn certify_challenge(credential: &str) -> Vec<u8> {
	292	let mut c = b"oxy1 certify ".to_vec();
	293	c.extend_from_slice(blake3::hash(credential.as_bytes()).as_bytes());
	294	c
	295	}
	296
02e69188 Andy McCall 19 days ago ↶	297	#[derive(Clone, Debug, PartialEq, Eq, thiserror::Error)]
	298	pub enum CertError {
	299	#[error("the certificate names issuer {0}, not this one")]
	300	WrongIssuer(String),
	301	#[error("the issuer's signature does not verify: {0}")]
	302	BadSignature(String),
	303	#[error("the certificate is valid for no time, or for longer than an hour")]
	304	BadLifetime,
	305	#[error("the certificate gives no scope")]
	306	NoScope,
	307	#[error("{0}")]
	308	Schema(String),
	309	}
	310
	311	impl From<ObjectError> for CertError {
	312	fn from(e: ObjectError) -> Self {
	313	CertError::Schema(e.to_string())
	314	}
	315	}
	316
	317	/// A certificate with its issuer's signature over its ObjectRef.
	318	#[derive(Clone, Debug, PartialEq, Eq)]
	319	pub struct SignedCertificate {
	320	pub cert: Certificate,
	321	pub sig: Signature,
	322	}
	323
	324	impl SignedCertificate {
	325	/// Issue `cert`, signed by the issuer `issuer` holds the secret of.
	326	pub fn sign(mut cert: Certificate, issuer: &Identity, sk: &SecretKey) -> SignedCertificate {
	327	// Claims in their canonical order, as encoded.
	328	cert.claims.sort();
	329	let sig = sk.sign(Domain::Certificate, &issuer.hash(), &cert.hash());
	330	SignedCertificate { cert, sig }
	331	}
	332
	333	/// Signed by `issuer`, which it names, and well formed. Whether to
	334	/// trust the issuer for its subject is the policy's question.
	335	pub fn verify(&self, issuer: &Identity) -> Result<(), CertError> {
	336	let c = &self.cert;
	337	if issuer.hash() != c.issuer \|\| self.sig.key != c.issuer {
	338	return Err(CertError::WrongIssuer(c.issuer.short(12)));
	339	}
	340	verify(issuer, &self.sig, Domain::Certificate, &c.hash())
	341	.map_err(\|e\| CertError::BadSignature(e.to_string()))?;
	342	if c.expires <= c.not_before \|\| c.expires - c.not_before > MAX_LIFETIME_MS {
	343	return Err(CertError::BadLifetime);
	344	}
	345	if c.scope.is_empty() {
	346	return Err(CertError::NoScope);
	347	}
	348	Ok(())
	349	}
	350
	351	/// `[certificate bytes, signature]`.
	352	pub fn encode(&self) -> Vec<u8> {
	353	cbor::encode(&Value::Array(vec![
	354	Value::Bytes(self.cert.encode()),
	355	self.sig.to_value(),
	356	]))
	357	}
	358
	359	pub fn decode(b: &[u8]) -> Result<SignedCertificate, CertError> {
	360	let v = cbor::decode(b).map_err(ObjectError::from)?;
361	let a = array(&v, "signed certificate")?;
362	if a.len() != 2 {
363	return Err(CertError::Schema(
364	"signed certificate: expected [certificate, signature]".into(),
365	));
366	}
367	Ok(SignedCertificate {
368	cert: Certificate::decode(bytes(&a[0], "certificate")?)?,
369	sig: Signature::from_value(&a[1])?,
370	})
371	}
372	}
373
374	#[cfg(test)]
375	mod tests {
376	use super::*;
377
378	fn issue(
379	issuer_sk: &SecretKey,
380	issuer: &Identity,
381	minutes: u64,
382	) -> (SecretKey, SignedCertificate) {
383	let job_sk = SecretKey::generate();
384	let cert = Certificate {
385	key: job_sk.identity("job 12 build", "[email protected]", 1_000),
386	issuer: issuer.hash(),
387	subject: "repo:andy/demo:bookmark:main".into(),
388	claims: vec![
389	("run".into(), "12".into()),
390	("environment".into(), "prod".into()),
391	],
392	scope: Scope::CHANGES \| Scope::REFS,
393	not_before: 1_000,
394	expires: 1_000 + minutes * 60_000,
a2387d54 Andy McCall 19 days ago ↶	395	grant: None,
02e69188 Andy McCall 19 days ago ↶	396	};
	397	(job_sk, SignedCertificate::sign(cert, issuer, issuer_sk))
	398	}
	399
	400	#[test]
	401	fn a_certificate_round_trips_and_verifies_with_its_issuer_only() {
	402	let hub_sk = SecretKey::generate();
	403	let hub = hub_sk.identity("oxygenhub.io", "[email protected]", 1);
	404	let (_, sc) = issue(&hub_sk, &hub, 10);
	405	let back = SignedCertificate::decode(&sc.encode()).unwrap();
	406	assert_eq!(back, sc);
	407	assert_eq!(back.cert.claims[0].0, "environment", "claims kept sorted");
	408	assert_eq!(back.cert.claim("run"), Some("12"));
	409	assert!(back.verify(&hub).is_ok());
	410	let other_sk = SecretKey::generate();
	411	let other = other_sk.identity("elsewhere", "[email protected]", 1);
	412	assert!(matches!(
	413	back.verify(&other),
	414	Err(CertError::WrongIssuer(_))
	415	));
	416	// Changed after signing: the signature no longer covers it.
	417	let mut forged = back.clone();
	418	forged.cert.subject = "repo:andy/demo:bookmark:release".into();
	419	assert!(matches!(
	420	forged.verify(&hub),
	421	Err(CertError::BadSignature(_))
	422	));
	423	// Signed by another key in the issuer's name.
	424	let mut stolen = back.clone();
	425	stolen.sig = other_sk.sign(Domain::Certificate, &hub.hash(), &back.cert.hash());
	426	assert!(matches!(
	427	stolen.verify(&hub),
	428	Err(CertError::BadSignature(_))
	429	));
a2387d54 Andy McCall 19 days ago ↶	430	}
	431
	432	#[test]
	433	fn a_grant_rides_in_its_certificate_and_verifies_with_its_author_only() {
	434	let hub_sk = SecretKey::generate();
	435	let hub = hub_sk.identity("oxygenhub.io", "[email protected]", 1);
	436	let ada_sk = SecretKey::generate();
	437	let ada = ada_sk.identity("Ada", "[email protected]", 1);
	438	let g = SignedGrant::sign(
	439	Grant {
	440	grantor: ada.hash(),
	441	subject: "agent:claude@ada".into(),
	442	issuer: hub.hash(),
	443	scope: Scope::CHANGES \| Scope::SEAL,
	444	not_before: 1_000,
	445	expires: 2_000,
	446	},
	447	&ada,
	448	&ada_sk,
	449	);
	450	assert!(g.verify(&ada).is_ok());
	451	assert!(g.verify(&hub).is_err(), "only its author's");
	452	assert!(g.grant.covers(Scope::SEAL, 1_500));
	453	assert!(!g.grant.covers(Scope::REFS, 1_500));
	454	assert!(!g.grant.covers(Scope::SEAL, 2_001));
	455	let (_, plain) = issue(&hub_sk, &hub, 10);
	456	assert!(
	457	!matches!(cbor::decode(&plain.cert.encode()).unwrap(), Value::Map(m) if m.contains_key(&8)),
	458	"no grant, no field 8"
	459	);
	460	let mut with = plain.cert.clone();
	461	with.grant = Some(g.clone());
	462	let sc = SignedCertificate::sign(with, &hub, &hub_sk);
	463	let back = SignedCertificate::decode(&sc.encode()).unwrap();
	464	assert_eq!(back.cert.grant, Some(g));
	465	assert!(back.verify(&hub).is_ok());
	466	assert_ne!(back.cert.hash(), plain.cert.hash());
02e69188 Andy McCall 19 days ago ↶	467	}
	468
	469	#[test]
	470	fn it_covers_its_scope_and_window_only() {
	471	let hub_sk = SecretKey::generate();
	472	let hub = hub_sk.identity("oxygenhub.io", "[email protected]", 1);
	473	let (_, sc) = issue(&hub_sk, &hub, 10);
	474	let c = &sc.cert;
	475	assert!(c.covers(Scope::CHANGES, 1_000) && c.covers(Scope::REFS, 1_000 + 10 * 60_000));
	476	assert!(!c.covers(Scope::SEAL, 2_000), "not a scope it gives");
	477	assert!(!c.covers(Scope::CHANGES, 999), "before it");
	478	assert!(
	479	!c.covers(Scope::CHANGES, 1_000 + 10 * 60_000 + 1),
	480	"after it"
	481	);
	482	assert!(!c.covers(Scope::NONE, 2_000));
	483	let (_, long) = issue(&hub_sk, &hub, 61);
	484	assert_eq!(long.verify(&hub), Err(CertError::BadLifetime));
098227d4 Andy McCall 19 days ago ↶	485	}
	486
	487	#[test]
	488	fn the_proof_of_possession_is_bound_to_its_credential() {
	489	let sk = SecretKey::generate();
	490	let id = sk.identity("job", "[email protected]", 1);
	491	let proof = sk
	492	.sign_challenge(&id.hash(), &certify_challenge("flowjob_aaa"))
	493	.unwrap();
	494	assert!(
	495	crate::identity::verify_challenge(&id, &proof, &certify_challenge("flowjob_aaa"))
	496	.is_ok()
	497	);
	498	assert!(
	499	crate::identity::verify_challenge(&id, &proof, &certify_challenge("flowjob_bbb"))
	500	.is_err()
	501	);
02e69188 Andy McCall 19 days ago ↶	502	}
	503
	504	#[test]
	505	fn a_signature_by_the_short_lived_key_names_it() {
	506	let hub_sk = SecretKey::generate();
	507	let hub = hub_sk.identity("oxygenhub.io", "[email protected]", 1);
	508	let (job_sk, sc) = issue(&hub_sk, &hub, 10);
	509	let target = ObjectRef([5; 32]);
	510	let sig = job_sk.sign(Domain::Change, &sc.cert.key_id(), &target);
	511	assert_eq!(sig.key, sc.cert.key_id());
	512	assert!(verify(&sc.cert.key, &sig, Domain::Change, &target).is_ok());
	513	}
	514	}

Keyboard