crates/oxy-core/src/cert.rs at paths-for-resolutions-and-amend · andymccall/oxygen

◆ paths-for-resolutions-and-amend oxygen / crates / oxy-core / src / cert.rs

18.5 KiB · Rust · last changed Grants let certified keys act for an author (keyless step 5a) 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 (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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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,
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>,
40	}
41
42	impl Certificate {
43	pub fn to_value(&self) -> Value {
44	let mut claims = self.claims.clone();
45	claims.sort();
46	let mut v = Value::map([
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)),
72	]);
73	if let (Some(g), Value::Map(m)) = (&self.grant, &mut v) {
74	m.insert(8, Value::Bytes(g.encode()));
75	}
76	v
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")?,
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	},
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	}
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,
170	}
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	}
201
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
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
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,
394	grant: None,
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	));
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());
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));
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	);
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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