OXYGENHUB
# ee06a6c557b7 oxygen / crates / oxy-core / src / repo / policy.rs
15.3 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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//! Trust policy management and enforcement (spec §14.5).
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//!
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//! A repository with a policy verifies everything it receives: every change
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//! must be authenticated by a key the policy authorizes for the bookmark,
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//! every bookmark update must carry an attestation by such a key, and a new
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//! policy must be signed by a threshold of the roots of the policy it replaces.
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use super::*;
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use crate::identity::SecretKey;
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use crate::policy::{Policy, Require, Rule};
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use crate::protocol::SignedPolicy;
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/// One year, the default policy lifetime.
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const POLICY_LIFETIME_MS: u64 = 365 * 24 * 60 * 60 * 1000;
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/// A signed policy update: applied when it met the root threshold, else a
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/// proposal carrying the signatures gathered so far (spec §14.5).
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#[derive(Clone, Debug)]
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pub struct PolicyUpdate {
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    pub policy: Policy,
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    pub sigs: Vec<Signature>,
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    pub applied: bool,
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}
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impl PolicyUpdate {
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    pub fn signed(&self) -> SignedPolicy {
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        SignedPolicy { policy: self.policy.clone(), sigs: self.sigs.clone() }
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    }
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}
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impl Repo {
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    /// The current policy and its signatures, if the repository has one.
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    pub fn current_policy(&self) -> Result<Option<(ObjectRef, SignedPolicy)>> {
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        let Some(r) = self.view()?.policy else { return Ok(None) };
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        let policy = Policy::decode(&self.store.get_typed(&r, ObjectType::Policy)?)?;
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        Ok(Some((r, SignedPolicy { policy, sigs: self.store.signatures(&r)? })))
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    }
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    /// Store a policy with its signatures and point the `policy` reference at it.
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    pub(crate) fn set_policy(&self, sp: &SignedPolicy, command: &str) -> Result<ObjectRef> {
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        let r = self.store.put(ObjectType::Policy, &sp.policy.encode())?;
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        for sig in &sp.sigs {
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            self.store.put_signature(&r, sig)?;
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        }
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        for id in &sp.policy.identities {
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            self.store.put_identity(id)?;
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        }
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        let dir = self.oxy.join("policies");
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        fs::create_dir_all(&dir)?;
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        write_atomic(&dir.join(format!("{:020}", sp.policy.serial)), r.to_hex().as_bytes())?;
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        let (op_ref, op) = self.head_op()?;
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        if op.view.policy != Some(r) {
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            let mut view = op.view.clone();
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            view.policy = Some(r);
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            self.record_op(&[op_ref], command, view)?;
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        }
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        Ok(r)
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    }
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    /// Every policy this repository has applied, ascending by serial, with
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    /// its signatures. Policies applied before this index existed are
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    /// missing from it, except the current one.
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    pub fn policy_history(&self) -> Result<Vec<SignedPolicy>> {
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        let mut out: BTreeMap<u64, SignedPolicy> = BTreeMap::new();
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        if let Ok(rd) = fs::read_dir(self.oxy.join("policies")) {
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            for e in rd.flatten() {
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                let Ok(hex) = fs::read_to_string(e.path()) else { continue };
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                let Some(r) = ObjectRef::from_hex(hex.trim()) else { continue };
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                let Ok(bytes) = self.store.get_typed(&r, ObjectType::Policy) else { continue };
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                let policy = Policy::decode(&bytes)?;
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                out.insert(policy.serial, SignedPolicy { policy, sigs: self.store.signatures(&r)? });
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            }
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        }
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        if let Some((_, sp)) = self.current_policy()? {
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            out.insert(sp.policy.serial, sp);
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        }
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        Ok(out.into_values().collect())
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    }
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    /// Verify and apply a chain of policies ending in `newest`, each
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    /// against the one before it (spec §14.5). `chain` holds earlier
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    /// policies in any order; only those after the current serial are used.
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    pub(crate) fn adopt_policy_chain(&self, chain: &[SignedPolicy], newest: &SignedPolicy, command: &str) -> std::result::Result<(), String> {
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        let mut current = self.current_policy().map_err(|e| e.to_string())?.map(|(_, sp)| sp.policy);
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        let mut steps: Vec<&SignedPolicy> = chain
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            .iter()
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            .filter(|sp| current.as_ref().is_none_or(|c| sp.policy.serial > c.serial) && sp.policy.serial < newest.policy.serial)
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            .collect();
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        steps.sort_by_key(|sp| sp.policy.serial);
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        steps.push(newest);
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        for sp in steps {
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            self.check_policy(sp, current.as_ref())?;
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            self.set_policy(sp, &format!("{command} (policy serial {})", sp.policy.serial)).map_err(|e| e.to_string())?;
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            current = Some(sp.policy.clone());
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        }
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        Ok(())
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    }
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    /// Validate an incoming policy against the one we trust (`None` when
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    /// bootstrapping: the policy then vouches for itself).
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    pub fn check_policy(&self, sp: &SignedPolicy, trusted: Option<&Policy>) -> std::result::Result<(), String> {
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        if sp.policy.repo != self.id().map_err(|e| e.to_string())? {
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            return Err("policy is for a different repository".into());
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        }
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        if let Some(t) = trusted {
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            if sp.policy.serial <= t.serial {
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                return Err(format!("policy serial {} is not greater than the current {}", sp.policy.serial, t.serial));
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            }
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        }
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        match trusted {
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            Some(t) => sp.policy.verify_signatures(&sp.sigs, t)?,
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            None => vec![sp.policy.verify_bootstrap(&sp.sigs)?],
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        };
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        Ok(())
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    }
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    /// Sign `policy` with the configured key and apply it if the current
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    /// policy's root threshold is met; otherwise return it as a proposal.
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    fn sign_policy(&self, policy: Policy, command: &str) -> Result<PolicyUpdate> {
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        let Some((key, sk)) = self.secret_key()? else {
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            return fail("no secret key: run `oxy identity create` first");
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        };
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        self.sign_policy_with(policy, &[(key, &sk)], command)
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    }
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    /// Sign with every listed key; the first must be a root of the current
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    /// policy (the others may be roots of the new policy only, so that a
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    /// fresh clone can bootstrap from it).
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    pub(crate) fn sign_policy_with(&self, policy: Policy, signers: &[(KeyId, &SecretKey)], command: &str) -> Result<PolicyUpdate> {
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        let trusted = self.current_policy()?.map(|(_, sp)| sp.policy).unwrap_or_else(|| policy.clone());
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        if !signers.first().is_some_and(|(k, _)| trusted.roots.contains(k)) {
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            return fail("your key is not a root key of the current policy");
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        }
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        let target = policy.hash();
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        let sigs = signers.iter().map(|(k, sk)| sk.sign(Domain::Policy, k, &target)).collect();
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        self.gather(SignedPolicy { policy, sigs }, &trusted, command)
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    }
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    /// Apply `sp` when its signatures meet `trusted`'s threshold.
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    fn gather(&self, sp: SignedPolicy, trusted: &Policy, command: &str) -> Result<PolicyUpdate> {
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        let applied = sp.policy.verify_signatures(&sp.sigs, trusted).is_ok();
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        if applied {
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            self.set_policy(&sp, command)?;
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        }
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        Ok(PolicyUpdate { policy: sp.policy, sigs: sp.sigs, applied })
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    }
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    /// Add your signature to a proposal made by another root holder; the
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    /// policy is applied once the current root threshold is met.
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    pub fn policy_sign(&self, proposal: SignedPolicy) -> Result<PolicyUpdate> {
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        let Some((key, sk)) = self.secret_key()? else {
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            return fail("no secret key: run `oxy identity create` first");
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        };
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        let Some((_, current)) = self.current_policy()? else {
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            return fail("this repository has no policy; run `oxy policy init` or fetch one");
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        };
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        if proposal.policy.repo != self.id()? {
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            return fail("the proposal is for a different repository");
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        }
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        if proposal.policy.serial <= current.policy.serial {
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            return fail(format!("the proposal's serial {} is not greater than the current {}", proposal.policy.serial, current.policy.serial));
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        }
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        if !current.policy.roots.contains(&key) {
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            return fail("your key is not a root key of the current policy");
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        }
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        let mut sigs: Vec<Signature> = proposal.sigs.into_iter().filter(|s| s.key != key).collect();
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        sigs.push(sk.sign(Domain::Policy, &key, &proposal.policy.hash()));
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        self.gather(SignedPolicy { policy: proposal.policy, sigs }, &current.policy, "oxy policy sign")
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    }
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    /// Create the initial policy with the configured identity as sole root.
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    pub fn policy_init(&self) -> Result<PolicyUpdate> {
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        if self.current_policy()?.is_some() {
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            return fail("this repository already has a policy");
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        }
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        let Some((key, _)) = self.secret_key()? else {
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            return fail("no secret key: run `oxy identity create` first");
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        };
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        let identity = self.identity(&key)?;
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        let policy = Policy::single_root(self.id()?, identity, Hlc::now().wall_ms + POLICY_LIFETIME_MS);
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        self.sign_policy(policy, "oxy policy init")
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    }
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    /// Make `identity` a root key.
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    pub fn policy_root_add(&self, identity: Identity) -> Result<PolicyUpdate> {
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        let mut p = self.next_policy()?;
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        let key = identity.hash();
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        if p.roots.contains(&key) {
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            return fail(format!("{} is already a root", key.short(12)));
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        }
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        p.roots.push(key);
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        p.roots.sort();
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        p.revoked.retain(|k| k != &key);
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        if p.identity(&key).is_none() {
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            p.identities.push(identity);
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        }
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        self.sign_policy(p, &format!("oxy policy root add {}", key.short(12)))
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    }
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    /// Drop a root key; the remaining roots must still meet the threshold.
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    pub fn policy_root_remove(&self, key: &KeyId) -> Result<PolicyUpdate> {
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        let mut p = self.next_policy()?;
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        if !p.roots.contains(key) {
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            return fail(format!("{} is not a root", key.short(12)));
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        }
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        p.roots.retain(|k| k != key);
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        if (p.roots.len() as u32) < p.root_threshold {
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            return fail(format!("removing it would leave {} root(s) for a threshold of {}", p.roots.len(), p.root_threshold));
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        }
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        self.sign_policy(p, &format!("oxy policy root remove {}", key.short(12)))
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    }
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    /// Require `n` root signatures on future policy updates.
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    pub fn policy_set_threshold(&self, n: u32) -> Result<PolicyUpdate> {
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        let mut p = self.next_policy()?;
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        if n == 0 || n as usize > p.roots.len() {
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            return fail(format!("the threshold must be between 1 and the number of roots ({})", p.roots.len()));
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        }
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        p.root_threshold = n;
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        self.sign_policy(p, &format!("oxy policy root threshold {n}"))
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    }
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    pub(crate) fn next_policy(&self) -> Result<Policy> {
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        let Some((_, sp)) = self.current_policy()? else {
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            return fail("this repository has no policy; run `oxy policy init`");
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        };
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        let mut p = sp.policy;
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        p.serial += 1;
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        p.expires = Hlc::now().wall_ms + POLICY_LIFETIME_MS;
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        Ok(p)
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    }
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    /// Let `identity` update references matching `pattern` (default every reference).
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    pub fn policy_grant(&self, identity: Identity, pattern: Option<&str>) -> Result<PolicyUpdate> {
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        let mut p = self.next_policy()?;
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        let key = identity.hash();
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        let pattern = pattern.unwrap_or("*");
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        p.revoked.retain(|k| k != &key);
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        match p.rules.iter_mut().find(|r| r.pattern == pattern) {
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            Some(rule) => {
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                if !rule.keys.contains(&key) {
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                    rule.keys.push(key);
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                    rule.keys.sort();
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                }
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            }
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            None => p.rules.push(Rule { pattern: pattern.into(), keys: vec![key], threshold: 1, require: Require::Any, allow_conflicts: true }),
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        }
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        if p.identity(&key).is_none() {
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            p.identities.push(identity);
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        }
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        self.sign_policy(p, &format!("oxy policy grant {}", key.short(12)))
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    }
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    /// Revoke `key`: it may no longer update anything, and existing rules
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    /// drop it. A root key can be revoked by another root as long as the
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    /// remaining roots still meet the threshold.
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    pub fn policy_revoke(&self, key: &KeyId) -> Result<PolicyUpdate> {
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        let mut p = self.next_policy()?;
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        if p.roots.contains(key) {
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            let own = self.secret_key()?.map(|(k, _)| k);
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            if own == Some(*key) {
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                return fail("a root cannot revoke itself; have another root revoke it, or remove it with `oxy policy root remove` first");
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            }
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            p.roots.retain(|k| k != key);
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            if (p.roots.len() as u32) < p.root_threshold {
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                return fail(format!("revoking it would leave {} root(s) for a threshold of {}", p.roots.len(), p.root_threshold));
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            }
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        }
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        for r in &mut p.rules {
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            r.keys.retain(|k| k != key);
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        }
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        p.rules.retain(|r| !r.keys.is_empty());
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        if !p.revoked.contains(key) {
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            p.revoked.push(*key);
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            p.revoked.sort();
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        }
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        self.sign_policy(p, &format!("oxy policy revoke {}", key.short(12)))
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    }
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    /// Whether `change` may be part of `reference` under `policy`: it must be
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    /// authenticated (by its author or a delegate) with a key the matching
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    /// rule lists, using the authenticator kind the rule requires. A rule key
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    /// covers its rotation predecessors, and a delegate's signature counts
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    /// for the author it acts for.
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    pub fn change_allowed(&self, hash: &ChangeHash, policy: &Policy, reference: &str) -> std::result::Result<(), String> {
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        let rule = policy.rule_for(reference).ok_or_else(|| format!("no policy rule matches {reference:?}"))?;
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        match self.authenticate_change(hash).map_err(|e| e.to_string())? {
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            SignatureStatus::Valid { key, sealed, .. } => {
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                if policy.is_revoked(&key) {
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                    return Err(format!("change {} is signed by revoked key {}", hash.short(12), key.short(12)));
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                }
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                let author = self.store.get_change(hash).map(|c| c.author).map_err(|e| e.to_string())?;
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                let principal = if author.is_zero() { key } else { author };
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                let covered = rule.keys.iter().any(|k| policy.succeeds(k, &key) || policy.succeeds(k, &principal));
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                if !covered {
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                    return Err(format!("change {} is signed by {}, which may not update {reference:?}", hash.short(12), key.short(12)));
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                }
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                match (rule.require, sealed) {
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                    (Require::Signed, true) => Err(format!("{reference:?} requires individually signed changes; {} is only sealed", hash.short(12))),
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                    (Require::Sealed, false) => Err(format!("{reference:?} requires sealed changes; {} is individually signed", hash.short(12))),
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                    _ => Ok(()),
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                }
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            }
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            SignatureStatus::Unsigned => Err(format!("change {} is not signed or sealed", hash.short(12))),
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            SignatureStatus::Invalid(e) => Err(format!("change {}: {e}", hash.short(12))),
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        }
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    }
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    /// Check every change that `new` adds over `old` for `reference`.
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    pub(crate) fn state_allowed(&self, old_heads: &[ChangeHash], new_heads: &[ChangeHash], policy: &Policy, reference: &str) -> std::result::Result<(), String> {
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        let added = self.negotiate(old_heads, new_heads).map_err(|e| e.to_string())?;
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        for h in &added {
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            self.change_allowed(h, policy, reference)?;
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        }
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        if let Some(rule) = policy.rule_for(reference) {
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            if !rule.allow_conflicts && !added.is_empty() {
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                let st = self.load_state(new_heads).map_err(|e| e.to_string())?;
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                if st.materialize().is_conflicted() {
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                    return Err(format!("{reference:?} does not allow conflicted states"));
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                }
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            }
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        }
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        Ok(())
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    }
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}