OXYGENHUB
# 7a716eb94dee oxygen / crates / oxy-core / src / repo / policy.rs
7.9 KiB · Rust · last changed Trust policy: policy objects, init/grant/revoke, enforcement on push and fetch, propagation with downgrade protection (spec 0.6) 1 month ago source blame history raw
83e0677b Andy McCall ↶ 1 
//! 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::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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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 (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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    /// 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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        sp.policy.verify_signatures(&sp.sigs, trusted.unwrap_or(&sp.policy))?;
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        Ok(())
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    }
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    fn sign_policy(&self, policy: Policy) -> Result<SignedPolicy> {
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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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        if !policy.roots.contains(&key) {
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            return fail("your key is not a root key of this policy");
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        }
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        if policy.root_threshold > 1 {
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            return fail(format!("this policy needs {} root signatures; multi-signer updates are not implemented yet", policy.root_threshold));
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        }
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        let sig = sk.sign(Domain::Policy, &key, &policy.hash());
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        Ok(SignedPolicy { policy, sigs: vec![sig] })
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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<SignedPolicy> {
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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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        let sp = self.sign_policy(policy)?;
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        self.set_policy(&sp, "oxy policy init")?;
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        Ok(sp)
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    }
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    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<SignedPolicy> {
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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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        let sp = self.sign_policy(p)?;
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        self.set_policy(&sp, &format!("oxy policy grant {}", key.short(12)))?;
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        Ok(sp)
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    }
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    /// Revoke `key`: it may no longer update anything, and existing rules drop it.
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    pub fn policy_revoke(&self, key: &KeyId) -> Result<SignedPolicy> {
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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("cannot revoke a root key");
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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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        let sp = self.sign_policy(p)?;
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        self.set_policy(&sp, &format!("oxy policy revoke {}", key.short(12)))?;
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        Ok(sp)
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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.
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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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                if !rule.keys.contains(&key) {
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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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}