OXYGENHUB
# 728da0f92161 oxygen / crates / oxy-core / src / policy.rs
14.3 KiB · Rust · last changed Identity lifecycle: rotate, renew, delegates, revoke; expiry checks; policy roots, thresholds, proposals and oxy policy sign; policy chains served on refs and carried in push bundles (spec 0.6n) 1 month ago source blame history raw
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//! The trust policy (spec §14.5): who may update which references, signed
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//! by a threshold of root keys. A repository without a policy is unverified.
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//!
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//! Encoding: `{0: version, 1: repo, 2: serial, 3: {0: root keys, 1: threshold},
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//! 4: [rule], 5: [identity bytes], 6: [revoked], 7: expires}`; a rule is
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//! `{0: pattern, 1: keys, 2: threshold, 3: require, 4: allow_conflicts}` with
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//! `require` 0 = signed, 1 = sealed, 2 = any.
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use crate::cbor::{self, Value};
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use crate::hash::{hash_object, KeyId, ObjectRef, ObjectType};
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use crate::identity::{self, Domain, Identity, Signature};
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use crate::objects::{array, bytes, check_version, field, map, oref, text, uint, ObjectError, FORMAT_VERSION};
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use std::collections::BTreeMap;
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#[derive(Clone, Copy, Debug, PartialEq, Eq)]
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pub enum Require {
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    Signed,
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    Sealed,
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    Any,
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}
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impl Require {
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    fn tag(self) -> u64 {
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        match self {
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            Require::Signed => 0,
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            Require::Sealed => 1,
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            Require::Any => 2,
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        }
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    }
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    fn from_tag(t: u64) -> Result<Require, ObjectError> {
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        Ok(match t {
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            0 => Require::Signed,
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            1 => Require::Sealed,
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            2 => Require::Any,
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            _ => return Err(ObjectError::Schema(format!("unknown require {t}"))),
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        })
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    }
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    pub fn name(self) -> &'static str {
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        match self {
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            Require::Signed => "signed",
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            Require::Sealed => "sealed",
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            Require::Any => "any",
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        }
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    }
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}
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#[derive(Clone, Debug, PartialEq, Eq)]
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pub struct Rule {
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    /// Glob over reference names; `*` matches any run of characters.
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    pub pattern: String,
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    pub keys: Vec<KeyId>,
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    pub threshold: u32,
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    pub require: Require,
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    pub allow_conflicts: bool,
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}
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#[derive(Clone, Debug, PartialEq, Eq)]
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pub struct Policy {
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    pub repo: [u8; 16],
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    pub serial: u64,
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    pub roots: Vec<KeyId>,
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    pub root_threshold: u32,
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    pub rules: Vec<Rule>,
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    /// Embedded so verification needs no fetch.
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    pub identities: Vec<Identity>,
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    pub revoked: Vec<KeyId>,
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    pub expires: u64,
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}
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/// `*` matches any run of characters (including `/`); everything else is literal.
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pub fn glob_matches(pattern: &str, name: &str) -> bool {
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    fn rec(p: &[u8], n: &[u8]) -> bool {
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        match p.first() {
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            None => n.is_empty(),
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            Some(b'*') => (0..=n.len()).any(|i| rec(&p[1..], &n[i..])),
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            Some(c) => n.first() == Some(c) && rec(&p[1..], &n[1..]),
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        }
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    }
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    rec(pattern.as_bytes(), name.as_bytes())
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}
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impl Policy {
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    fn keys_value(keys: &[KeyId]) -> Value {
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        Value::Array(keys.iter().map(|k| Value::Bytes(k.0.to_vec())).collect())
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    }
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    fn keys_from(v: &Value, what: &str) -> Result<Vec<KeyId>, ObjectError> {
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        let mut ks = array(v, what)?.iter().map(|k| oref(k, what)).collect::<Result<Vec<_>, _>>()?;
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        ks.sort();
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        ks.dedup();
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        Ok(ks)
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    }
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    pub fn to_value(&self) -> Value {
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        Value::map([
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            (0, Value::Uint(FORMAT_VERSION)),
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            (1, Value::Bytes(self.repo.to_vec())),
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            (2, Value::Uint(self.serial)),
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            (3, Value::map([(0, Self::keys_value(&self.roots)), (1, Value::Uint(self.root_threshold as u64))])),
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            (
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                4,
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                Value::Array(
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                    self.rules
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                        .iter()
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                        .map(|r| {
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                            Value::map([
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                                (0, Value::Text(r.pattern.clone())),
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                                (1, Self::keys_value(&r.keys)),
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                                (2, Value::Uint(r.threshold as u64)),
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                                (3, Value::Uint(r.require.tag())),
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                                (4, Value::Bool(r.allow_conflicts)),
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                            ])
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                        })
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                        .collect(),
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                ),
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            ),
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            (5, Value::Array(self.identities.iter().map(|i| Value::Bytes(i.encode())).collect())),
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            (6, Self::keys_value(&self.revoked)),
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            (7, Value::Uint(self.expires)),
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        ])
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    }
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    pub fn encode(&self) -> Vec<u8> {
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        cbor::encode(&self.to_value())
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    }
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    pub fn hash(&self) -> ObjectRef {
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        hash_object(ObjectType::Policy, &self.encode())
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    }
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    pub fn decode(b: &[u8]) -> Result<Policy, ObjectError> {
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        let v = cbor::decode(b)?;
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        let m = map(&v, "policy")?;
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        check_version(m)?;
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        let roots = map(field(m, 3, "roots")?, "roots")?;
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        let mut rules = Vec::new();
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        for r in array(field(m, 4, "rules")?, "rules")? {
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            let rm = map(r, "rule")?;
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            rules.push(Rule {
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                pattern: text(field(rm, 0, "pattern")?, "pattern")?.to_owned(),
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                keys: Self::keys_from(field(rm, 1, "rule keys")?, "rule keys")?,
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                threshold: uint(field(rm, 2, "threshold")?, "threshold")? as u32,
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                require: Require::from_tag(uint(field(rm, 3, "require")?, "require")?)?,
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                allow_conflicts: field(rm, 4, "allow_conflicts")?.as_bool().ok_or_else(|| ObjectError::Schema("allow_conflicts: expected bool".into()))?,
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            });
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        }
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        let identities = array(field(m, 5, "identities")?, "identities")?
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            .iter()
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            .map(|i| Identity::decode(bytes(i, "identity")?))
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            .collect::<Result<Vec<_>, _>>()?;
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        let p = Policy {
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            repo: bytes(field(m, 1, "repo")?, "repo")?.try_into().map_err(|_| ObjectError::Schema("repo: expected 16 bytes".into()))?,
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            serial: uint(field(m, 2, "serial")?, "serial")?,
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            roots: Self::keys_from(field(roots, 0, "root keys")?, "root keys")?,
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            root_threshold: uint(field(roots, 1, "root threshold")?, "root threshold")? as u32,
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            rules,
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            identities,
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            revoked: Self::keys_from(field(m, 6, "revoked")?, "revoked")?,
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            expires: uint(field(m, 7, "expires")?, "expires")?,
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        };
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        if p.root_threshold == 0 || p.root_threshold as usize > p.roots.len() {
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            return Err(ObjectError::Schema("root threshold must be between 1 and the number of root keys".into()));
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        }
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        for r in &p.rules {
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            if r.threshold == 0 || r.threshold as usize > r.keys.len() {
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                return Err(ObjectError::Schema(format!("rule {:?}: threshold must be between 1 and the number of keys", r.pattern)));
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            }
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        }
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        Ok(p)
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    }
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    pub fn identity(&self, key: &KeyId) -> Option<&Identity> {
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        self.identities.iter().find(|i| i.hash() == *key)
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    }
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    pub fn is_revoked(&self, key: &KeyId) -> bool {
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        self.revoked.contains(key)
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    }
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    pub fn is_expired(&self, now_ms: u64) -> bool {
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        now_ms > self.expires
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    }
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    /// The first rule whose pattern matches `reference`.
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    pub fn rule_for(&self, reference: &str) -> Option<&Rule> {
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        self.rules.iter().find(|r| glob_matches(&r.pattern, reference))
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    }
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    /// Whether `key` may update `reference`: listed in the matching rule and not revoked.
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    pub fn authorizes(&self, key: &KeyId, reference: &str) -> bool {
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        !self.is_revoked(key) && self.rule_for(reference).is_some_and(|r| r.keys.contains(key))
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    }
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    /// Verify that `sigs` over this policy's hash meet `trusted`'s root
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    /// threshold (`trusted` is the previous policy, or this one when
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    /// bootstrapping). Returns the signing root keys.
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    pub fn verify_signatures(&self, sigs: &[Signature], trusted: &Policy) -> Result<Vec<KeyId>, String> {
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        let target = self.hash();
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        let mut signers = Vec::new();
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        for sig in sigs {
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            if !trusted.roots.contains(&sig.key) || trusted.is_revoked(&sig.key) {
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                continue;
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            }
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            let Some(id) = trusted.identity(&sig.key).or_else(|| self.identity(&sig.key)) else { continue };
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            if identity::verify(id, sig, Domain::Policy, &target).is_ok() && !signers.contains(&sig.key) {
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                signers.push(sig.key);
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            }
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        }
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        if (signers.len() as u32) < trusted.root_threshold {
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            return Err(format!("policy needs {} root signature(s), has {}", trusted.root_threshold, signers.len()));
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        }
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        Ok(signers)
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    }
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    /// Bootstrap check for the first policy a repository sees (trust on
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    /// first use): at least one valid signature by one of its own roots.
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    /// The full threshold applies only to updates from a trusted policy,
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    /// whose signers are the previous roots and need not be the new ones.
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    pub fn verify_bootstrap(&self, sigs: &[Signature]) -> Result<KeyId, String> {
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        let target = self.hash();
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        for sig in sigs {
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            if !self.roots.contains(&sig.key) || self.is_revoked(&sig.key) {
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                continue;
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            }
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            if let Some(id) = self.identity(&sig.key) {
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                if identity::verify(id, sig, Domain::Policy, &target).is_ok() {
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                    return Ok(sig.key);
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                }
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            }
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        }
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        Err("policy carries no valid signature by one of its own root keys".into())
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    }
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    /// A single-root policy letting `root` do everything on every reference.
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    pub fn single_root(repo: [u8; 16], root: Identity, expires: u64) -> Policy {
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        let key = root.hash();
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        Policy {
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            repo,
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            serial: 1,
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            roots: vec![key],
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            root_threshold: 1,
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            rules: vec![Rule { pattern: "*".into(), keys: vec![key], threshold: 1, require: Require::Any, allow_conflicts: true }],
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            identities: vec![root],
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            revoked: vec![],
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            expires,
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        }
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    }
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    /// Whether `key` appears anywhere in the policy (roots, rules, identities).
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    pub fn mentions(&self, key: &KeyId) -> bool {
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        self.roots.contains(key) || self.rules.iter().any(|r| r.keys.contains(key)) || self.identity(key).is_some()
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    }
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    /// Whether `key` is `rule_key` or one of its predecessors in the
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    /// rotation chain (`previous` links, spec §14.2), so that changes signed
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    /// before a rotation remain authorized. Revoked keys never qualify.
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    pub fn succeeds(&self, rule_key: &KeyId, key: &KeyId) -> bool {
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        if self.is_revoked(key) {
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            return false;
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        }
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        let mut cur = Some(*rule_key);
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        for _ in 0..32 {
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            match cur {
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                Some(k) if k == *key => return true,
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                Some(k) => cur = self.identity(&k).and_then(|i| i.previous),
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                None => return false,
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            }
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        }
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        false
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    }
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    /// Replace `old` by `new` in the roots and every rule and embed `new`'s
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    /// identity (a rotation, spec §14.2). The old identity stays embedded so
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    /// signatures made before the rotation still verify; it is superseded,
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    /// not revoked.
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    pub fn substitute_key(&mut self, old: &KeyId, new: Identity) {
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        let nk = new.hash();
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        for k in self.roots.iter_mut().chain(self.rules.iter_mut().flat_map(|r| r.keys.iter_mut())) {
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            if k == old {
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                *k = nk;
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            }
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        }
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        for r in &mut self.rules {
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            r.keys.sort();
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            r.keys.dedup();
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        }
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        self.roots.sort();
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        self.roots.dedup();
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        if self.identity(&nk).is_none() {
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            self.identities.push(new);
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        }
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    }
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    /// Identities keyed by KeyId.
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    pub fn identity_map(&self) -> BTreeMap<KeyId, &Identity> {
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        self.identities.iter().map(|i| (i.hash(), i)).collect()
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    }
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}
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#[cfg(test)]
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mod tests {
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    use super::*;
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    use crate::identity::SecretKey;
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    fn sk(n: u8) -> SecretKey {
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        SecretKey { ed_seed: [n; 32], ml_seed: [n + 100; 32] }
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    }
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    #[test]
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    fn globs() {
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        assert!(glob_matches("*", "main"));
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        assert!(glob_matches("release/*", "release/1.0"));
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        assert!(!glob_matches("release/*", "main"));
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        assert!(glob_matches("main", "main"));
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        assert!(!glob_matches("main", "main2"));
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        assert!(glob_matches("*-rc*", "1.0-rc2"));
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        assert!(glob_matches("", ""));
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    }
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    #[test]
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    fn round_trip_and_rules() {
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        let root = sk(1).identity("Root", "r@x", 0);
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        let dev = sk(2).identity("Dev", "d@x", 0);
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        let mut p = Policy::single_root([9; 16], root.clone(), 10);
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        p.rules.insert(0, Rule { pattern: "release/*".into(), keys: vec![root.hash()], threshold: 1, require: Require::Signed, allow_conflicts: false });
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        p.rules[1].keys.push(dev.hash());
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        p.identities.push(dev.clone());
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        p.revoked.push(ObjectRef([7; 32]));
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        let d = Policy::decode(&p.encode()).unwrap();
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        assert_eq!(d.rules.len(), 2);
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        assert_eq!(d.rules[0].require, Require::Signed);
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        assert_eq!(d.identity(&dev.hash()), Some(&dev));
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        assert!(d.authorizes(&dev.hash(), "main"));
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        assert!(!d.authorizes(&dev.hash(), "release/1"));
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        assert!(d.authorizes(&root.hash(), "release/1"));
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        assert!(d.is_expired(11) && !d.is_expired(10));
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        assert_eq!(d.hash(), p.hash());
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        let mut bad = p.clone();
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        bad.root_threshold = 5;
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        assert!(Policy::decode(&bad.encode()).is_err());
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    }
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    #[test]
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    fn signatures_need_root_threshold() {
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        let r1 = sk(1);
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        let r2 = sk(2);
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        let i1 = r1.identity("a", "a", 0);
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        let i2 = r2.identity("b", "b", 0);
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        let mut p = Policy::single_root([1; 16], i1.clone(), 100);
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        p.roots.push(i2.hash());
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        p.roots.sort();
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        p.root_threshold = 2;
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        p.identities.push(i2.clone());
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        let h = p.hash();
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        let s1 = r1.sign(Domain::Policy, &i1.hash(), &h);
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        let s2 = r2.sign(Domain::Policy, &i2.hash(), &h);
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        assert!(p.verify_signatures(&[s1.clone()], &p).is_err());
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        assert_eq!(p.verify_signatures(&[s1.clone(), s2.clone()], &p).unwrap().len(), 2);
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        // Duplicates do not count twice; a non-root signer does not count.
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        assert!(p.verify_signatures(&[s1.clone(), s1.clone()], &p).is_err());
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        let stranger = sk(3);
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        let si = stranger.identity("s", "s", 0);
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        let s3 = stranger.sign(Domain::Policy, &si.hash(), &h);
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        assert!(p.verify_signatures(&[s1.clone(), s3], &p).is_err());
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        // A successor policy is verified against the previous roots.
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        let mut next = p.clone();
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        next.serial = 2;
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        next.revoked.push(i2.hash());
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        let nh = next.hash();
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        let n1 = r1.sign(Domain::Policy, &i1.hash(), &nh);
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        let n2 = r2.sign(Domain::Policy, &i2.hash(), &nh);
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        assert_eq!(next.verify_signatures(&[n1, n2], &p).unwrap().len(), 2);
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    }
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}