crates/oxy-core/src/protocol.rs at 3526d339519f · andymccall/oxygen

# 3526d339519f oxygen / crates / oxy-core / src / protocol.rs
35.6 KiB · Rust · last changed Delegate rule on fetch and tags too 1 month ago source blame history raw
//! Transport-agnostic protocol (spec §16): what a client asks of a remote and
//! what a server does with a push. `LocalRemote` serves another repository
//! directory in-process, `HttpRemote` speaks to an `oxy-server` over HTTP(S),
//! and the server side reuses `Repo::receive_push` and friends unchanged.
//!
//! Wire messages are deterministic CBOR (`wire` module); over HTTP each is a
//! request or response body with content type `application/oxy-cbor`.

use crate::attest::Attest;
use crate::cbor::{self, Value};
use crate::hash::{ChangeHash, ObjectRef, ObjectType};
use crate::identity::Signature;
use crate::objects::{self as o, Change, ObjectError};
use crate::policy::Policy;
use crate::repo::{Repo, RepoError, Result};
use std::path::{Path, PathBuf};
use std::sync::Arc;

pub const CONTENT_TYPE: &str = "application/oxy-cbor";
pub const PROTOCOL_VERSION: u64 = 1;

/// An attestation together with the signatures over its ObjectRef.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct SignedAttest {
    pub attest: Attest,
    pub sigs: Vec<Signature>,
}

/// A policy together with the root signatures over its ObjectRef.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct SignedPolicy {
    pub policy: Policy,
    pub sigs: Vec<Signature>,
}

impl SignedPolicy {
    /// The proposal-file encoding (`wire::policy_value`).
    pub fn encode(&self) -> Vec<u8> {
        crate::cbor::encode(&wire::policy_value(self))
    }
    pub fn decode(b: &[u8]) -> Result<SignedPolicy> {
        wire::policy_from(
            &crate::cbor::decode(b).map_err(|e| RepoError::Object(ObjectError::from(e)))?,
        )
    }
}

/// What `refs` returns: every bookmark, every tag, and the current policy.
#[derive(Clone, Debug, Default)]
pub struct RefsResponse {
    pub refs: Vec<RemoteRef>,
    pub policy: Option<SignedPolicy>,
    pub tags: Vec<TagRef>,
    /// Earlier policies, ascending by serial, so a client behind by more
    /// than one update can verify each step (spec §14.5).
    pub history: Vec<SignedPolicy>,
}

/// A tag as a remote reports it (spec §10.1).
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct TagRef {
    pub name: String,
    pub state: ObjectRef,
    pub heads: Vec<ChangeHash>,
    pub attestation: Option<SignedAttest>,
}

/// One reference as a remote reports it.
#[derive(Clone, Debug)]
pub struct RemoteRef {
    pub name: String,
    pub state: ObjectRef,
    pub heads: Vec<ChangeHash>,
    pub attestation: Option<SignedAttest>,
}

/// Everything needed to add a set of changes to a repository.
#[derive(Clone, Debug, Default)]
pub struct Bundle {
    /// In dependency order, each with its individual signatures.
    pub changes: Vec<(Change, Vec<Signature>)>,
    /// Seals covering the changes.
    pub attests: Vec<SignedAttest>,
    /// Chunks, blobs, identities, and state objects referenced by the changes.
    pub objects: Vec<(ObjectType, Vec<u8>)>,
    /// Policies between the receiver's and the one sent with the push,
    /// ascending by serial (spec §14.5).
    pub policies: Vec<SignedPolicy>,
}

impl Bundle {
    pub fn is_empty(&self) -> bool {
        self.changes.is_empty() && self.attests.is_empty() && self.objects.is_empty()
    }
}

/// A requested bookmark move (spec §10.2, §16.3).
#[derive(Clone, Debug)]
pub struct RefUpdate {
    pub name: String,
    pub old_state: ObjectRef,
    pub new_state: ObjectRef,
    pub force: bool,
    pub attestation: Option<SignedAttest>,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct RefResult {
    pub name: String,
    pub ok: bool,
    pub reason: String,
}

pub trait Remote {
    fn repo_id(&self) -> Result<[u8; 16]>;
    fn refs(&self) -> Result<RefsResponse>;
    /// Changes in the closure of `want` but not of `have`, in dependency order.
    fn negotiate(&self, have: &[ChangeHash], want: &[ChangeHash]) -> Result<Vec<ChangeHash>>;
    /// The changes with their signatures, seals, identities, and blobs; blobs
    /// larger than `max_blob` bytes are left out for lazy fetching (spec §13.5).
    fn fetch(&self, changes: &[ChangeHash], max_blob: Option<u64>) -> Result<Bundle>;
    /// Individual objects by reference (spec §16.1 `objects`); a blob comes
    /// with its chunks.
    fn objects(&self, refs: &[ObjectRef]) -> Result<Vec<(ObjectType, Vec<u8>)>>;
    /// A checkpoint of exactly `heads` (spec §16.1 `checkpoint`): the
    /// checkpoint object, its payload blob, and the blob's chunks.
    fn checkpoint(&self, heads: &[ChangeHash]) -> Result<Bundle>;
    /// The changes within `depth` dependency steps of `heads` (spec §17).
    fn shallow(&self, heads: &[ChangeHash], depth: u32) -> Result<Vec<ChangeHash>>;
    /// Push changes, bookmark updates, new tags, and optionally a newer
    /// policy. The policy is applied first; a result named `policy` reports
    /// it, and each tag reports as `tags/<name>`.
    fn push(
        &self,
        bundle: Bundle,
        updates: Vec<RefUpdate>,
        policy: Option<SignedPolicy>,
        tags: Vec<TagRef>,
    ) -> Result<Vec<RefResult>>;
}

// ---------------------------------------------------------------- local

/// Another repository on this machine, served in-process.
pub struct LocalRemote {
    pub repo: Repo,
    /// The pushing repository's id, which binds an unbound target on the
    /// first push, as `Oxy-Repo-Id` does over HTTP.
    pub claimed_id: Option<[u8; 16]>,
}

impl LocalRemote {
    pub fn open(path: &Path) -> Result<LocalRemote> {
        Ok(LocalRemote {
            repo: Repo::open(path)?,
            claimed_id: None,
        })
    }
}

impl Remote for LocalRemote {
    fn repo_id(&self) -> Result<[u8; 16]> {
        self.repo.id()
    }
    fn refs(&self) -> Result<RefsResponse> {
        self.repo.remote_refs()
    }
    fn negotiate(&self, have: &[ChangeHash], want: &[ChangeHash]) -> Result<Vec<ChangeHash>> {
        self.repo.negotiate(have, want)
    }
    fn fetch(&self, changes: &[ChangeHash], max_blob: Option<u64>) -> Result<Bundle> {
        self.repo.bundle_for_filtered(changes, max_blob)
    }
    fn objects(&self, refs: &[ObjectRef]) -> Result<Vec<(ObjectType, Vec<u8>)>> {
        self.repo.objects_for(refs)
    }
    fn checkpoint(&self, heads: &[ChangeHash]) -> Result<Bundle> {
        self.repo.checkpoint_bundle_for(heads)
    }
    fn shallow(&self, heads: &[ChangeHash], depth: u32) -> Result<Vec<ChangeHash>> {
        self.repo.shallow_changes(heads, depth)
    }
    fn push(
        &self,
        bundle: Bundle,
        updates: Vec<RefUpdate>,
        policy: Option<SignedPolicy>,
        tags: Vec<TagRef>,
    ) -> Result<Vec<RefResult>> {
        if self.repo.is_unbound() {
            match self.claimed_id {
                Some(id) => self.repo.bind_id(id)?,
                None => {
                    return Err(RepoError::Msg(
                        "the remote is unbound and this client did not say which repository it is"
                            .into(),
                    ))
                }
            }
        }
        self.repo.receive_push(bundle, updates, policy, tags)
    }
}

// ---------------------------------------------------------------- http

/// How to reach a remote: credentials and trust.
#[derive(Clone, Debug, Default)]
pub struct RemoteOptions {
    /// Bearer token for pushes.
    pub token: Option<String>,
    /// PEM file with extra root certificates to trust for `https://` remotes
    /// (self-hosted servers); the system web roots are always trusted.
    pub ca: Option<PathBuf>,
    /// The local repository's id, sent as `Oxy-Repo-Id` so an unbound
    /// hosted repository can adopt it on the first push (spec §16.1).
    pub repo_id: Option<[u8; 16]>,
}

/// The request header carrying the client's repository id.
pub const REPO_ID_HEADER: &str = "Oxy-Repo-Id";

/// The id of a hosted repository that has not adopted one yet.
pub const UNBOUND_ID: [u8; 16] = [0; 16];

/// A remote served by `oxy-server` at `<base>/oxy/v1/...`.
pub struct HttpRemote {
    base: String,
    token: Option<String>,
    repo_id: Option<[u8; 16]>,
    agent: ureq::Agent,
}

/// A TLS client configuration trusting the web roots plus `ca`, if given.
fn tls_client_config(ca: Option<&Path>) -> Result<Arc<rustls::ClientConfig>> {
    let mut roots = rustls::RootCertStore::empty();
    roots.extend(webpki_roots::TLS_SERVER_ROOTS.iter().cloned());
    if let Some(path) = ca {
        let pem = std::fs::read(path)
            .map_err(|e| RepoError::Msg(format!("reading CA file {}: {e}", path.display())))?;
        let certs = rustls_pemfile::certs(&mut pem.as_slice())
            .collect::<std::result::Result<Vec<_>, _>>()
            .map_err(|e| RepoError::Msg(format!("parsing CA file {}: {e}", path.display())))?;
        if certs.is_empty() {
            return Err(RepoError::Msg(format!(
                "CA file {} holds no certificates",
                path.display()
            )));
        }
        for c in certs {
            roots
                .add(c)
                .map_err(|e| RepoError::Msg(format!("CA file {}: {e}", path.display())))?;
        }
    }
    let cfg = rustls::ClientConfig::builder_with_provider(Arc::new(
        rustls::crypto::ring::default_provider(),
    ))
    .with_safe_default_protocol_versions()
    .map_err(|e| RepoError::Msg(e.to_string()))?
    .with_root_certificates(roots)
    .with_no_client_auth();
    Ok(Arc::new(cfg))
}

impl HttpRemote {
    pub fn new(base: &str, options: &RemoteOptions) -> Result<HttpRemote> {
        let agent = ureq::AgentBuilder::new()
            .tls_config(tls_client_config(options.ca.as_deref())?)
            .build();
        Ok(HttpRemote {
            base: base.trim_end_matches('/').to_string(),
            token: options.token.clone(),
            repo_id: options.repo_id,
            agent,
        })
    }

    fn call(&self, post: bool, endpoint: &str, body: Option<&[u8]>) -> Result<Vec<u8>> {
        let url = format!("{}/oxy/v1/{endpoint}", self.base);
        let mut req = if post {
            self.agent.post(&url)
        } else {
            self.agent.get(&url)
        };
        req = req.set("Accept", CONTENT_TYPE);
        if let Some(t) = &self.token {
            req = req.set("Authorization", &format!("Bearer {t}"));
        }
        if let Some(id) = &self.repo_id {
            req = req.set(REPO_ID_HEADER, &hex::encode(id));
        }
        let resp = match body {
            Some(b) => req.set("Content-Type", CONTENT_TYPE).send_bytes(b),
            None => req.call(),
        };
        match resp {
            Ok(r) => {
                let mut out = Vec::new();
                r.into_reader()
                    .read_to_end(&mut out)
                    .map_err(|e| RepoError::Msg(format!("{url}: {e}")))?;
                Ok(out)
            }
            Err(ureq::Error::Status(code, r)) => {
                let text = r.into_string().unwrap_or_default();
                Err(RepoError::Msg(format!(
                    "{url}: HTTP {code}: {}",
                    text.trim()
                )))
            }
            Err(e) => Err(RepoError::Msg(format!("{url}: {e}"))),
        }
    }
}

/// An authenticated GET of any URL on a host, with the same TLS trust and
/// token as remotes use (for hub APIs: proposals). Returns the body.
pub fn http_get(url: &str, options: &RemoteOptions) -> Result<Vec<u8>> {
    let agent = ureq::AgentBuilder::new()
        .tls_config(tls_client_config(options.ca.as_deref())?)
        .build();
    let mut req = agent.get(url).set("Accept", "application/json");
    if let Some(t) = &options.token {
        req = req.set("Authorization", &format!("Bearer {t}"));
    }
    match req.call() {
        Ok(r) => {
            let mut out = Vec::new();
            r.into_reader()
                .read_to_end(&mut out)
                .map_err(|e| RepoError::Msg(format!("{url}: {e}")))?;
            Ok(out)
        }
        Err(ureq::Error::Status(code, r)) => {
            let text = r.into_string().unwrap_or_default();
            Err(RepoError::Msg(format!(
                "{url}: HTTP {code}: {}",
                text.trim()
            )))
        }
        Err(e) => Err(RepoError::Msg(format!("{url}: {e}"))),
    }
}

impl Remote for HttpRemote {
    fn repo_id(&self) -> Result<[u8; 16]> {
        wire::decode_capabilities(&self.call(false, "capabilities", None)?)
    }
    fn refs(&self) -> Result<RefsResponse> {
        Ok(wire::decode_refs(&self.call(false, "refs", None)?)?.1)
    }
    fn negotiate(&self, have: &[ChangeHash], want: &[ChangeHash]) -> Result<Vec<ChangeHash>> {
        wire::decode_hashes(&self.call(
            true,
            "negotiate",
            Some(&wire::encode_negotiate(have, want)),
        )?)
    }
    fn fetch(&self, changes: &[ChangeHash], max_blob: Option<u64>) -> Result<Bundle> {
        wire::decode_bundle(&self.call(
            true,
            "fetch",
            Some(&wire::encode_fetch(changes, max_blob)),
        )?)
    }
    fn objects(&self, refs: &[ObjectRef]) -> Result<Vec<(ObjectType, Vec<u8>)>> {
        Ok(
            wire::decode_bundle(&self.call(true, "objects", Some(&wire::encode_hashes(refs)))?)?
                .objects,
        )
    }
    fn checkpoint(&self, heads: &[ChangeHash]) -> Result<Bundle> {
        wire::decode_bundle(&self.call(true, "checkpoint", Some(&wire::encode_hashes(heads)))?)
    }
    fn shallow(&self, heads: &[ChangeHash], depth: u32) -> Result<Vec<ChangeHash>> {
        wire::decode_hashes(&self.call(
            true,
            "shallow",
            Some(&wire::encode_shallow(heads, depth)),
        )?)
    }
    fn push(
        &self,
        bundle: Bundle,
        updates: Vec<RefUpdate>,
        policy: Option<SignedPolicy>,
        tags: Vec<TagRef>,
    ) -> Result<Vec<RefResult>> {
        wire::decode_push_response(&self.call(
            true,
            "push",
            Some(&wire::encode_push(
                &bundle,
                &updates,
                policy.as_ref(),
                &tags,
            )),
        )?)
    }
}

/// Open a remote by URL: a local path (optionally `file://`), or `http(s)://`.
pub fn open_remote(url: &str, options: &RemoteOptions) -> Result<Box<dyn Remote>> {
    if url.starts_with("http://") || url.starts_with("https://") {
        return Ok(Box::new(HttpRemote::new(url, options)?));
    }
    let path = url.strip_prefix("file://").unwrap_or(url);
    if path.contains("://") {
        return Err(RepoError::Msg(format!("unsupported remote URL {url:?}")));
    }
    let mut local = LocalRemote::open(Path::new(path))?;
    local.claimed_id = options.repo_id;
    Ok(Box::new(local))
}

// ---------------------------------------------------------------- wire

/// CBOR encodings of the protocol messages (spec §16.1).
pub mod wire {
    use super::*;

    fn schema(msg: &str) -> RepoError {
        RepoError::Object(ObjectError::Schema(msg.into()))
    }
    fn sigs_value(sigs: &[Signature]) -> Value {
        Value::Array(sigs.iter().map(|s| s.to_value()).collect())
    }
    fn sigs_from(v: &Value) -> Result<Vec<Signature>> {
        Ok(o::array(v, "signatures")?
            .iter()
            .map(Signature::from_value)
            .collect::<std::result::Result<Vec<_>, _>>()?)
    }
    fn hashes_value(hs: &[ObjectRef]) -> Value {
        Value::Array(hs.iter().map(|h| Value::Bytes(h.0.to_vec())).collect())
    }
    fn hashes_from(v: &Value) -> Result<Vec<ObjectRef>> {
        Ok(o::array(v, "hashes")?
            .iter()
            .map(|h| o::oref(h, "hash"))
            .collect::<std::result::Result<Vec<_>, _>>()?)
    }
    fn attest_value(sa: &SignedAttest) -> Value {
        Value::Array(vec![Value::Bytes(sa.attest.encode()), sigs_value(&sa.sigs)])
    }
    fn attest_from(v: &Value) -> Result<SignedAttest> {
        let a = o::array(v, "signed attest")?;
        if a.len() != 2 {
            return Err(schema("signed attest: expected [attest, sigs]"));
        }
        Ok(SignedAttest {
            attest: Attest::decode(o::bytes(&a[0], "attest")?)?,
            sigs: sigs_from(&a[1])?,
        })
    }
    fn opt_attest_value(sa: &Option<SignedAttest>) -> Value {
        sa.as_ref().map(attest_value).unwrap_or(Value::Null)
    }
    fn opt_attest_from(v: &Value) -> Result<Option<SignedAttest>> {
        if v.is_null() {
            Ok(None)
        } else {
            attest_from(v).map(Some)
        }
    }
    /// `[policy bytes, [signature]]`: also the format of a policy proposal
    /// file exchanged between root holders (spec §14.5).
    pub fn policy_value(sp: &SignedPolicy) -> Value {
        Value::Array(vec![Value::Bytes(sp.policy.encode()), sigs_value(&sp.sigs)])
    }
    pub fn policy_from(v: &Value) -> Result<SignedPolicy> {
        let a = o::array(v, "signed policy")?;
        if a.len() != 2 {
            return Err(schema("signed policy: expected [policy, sigs]"));
        }
        Ok(SignedPolicy {
            policy: Policy::decode(o::bytes(&a[0], "policy")?)?,
            sigs: sigs_from(&a[1])?,
        })
    }
    fn opt_policy_value(sp: Option<&SignedPolicy>) -> Value {
        sp.map(policy_value).unwrap_or(Value::Null)
    }
    fn opt_policy_from(v: &Value) -> Result<Option<SignedPolicy>> {
        if v.is_null() {
            Ok(None)
        } else {
            policy_from(v).map(Some)
        }
    }
    fn map<'a>(v: &'a Value, what: &str) -> Result<&'a o::Map> {
        Ok(o::map(v, what)?)
    }
    fn field<'a>(m: &'a o::Map, k: u64, what: &str) -> Result<&'a Value> {
        Ok(o::field(m, k, what)?)
    }

    pub fn bundle_value(b: &Bundle) -> Value {
        Value::map([
            (
                0,
                Value::Array(
                    b.changes
                        .iter()
                        .map(|(c, s)| Value::Array(vec![Value::Bytes(c.encode()), sigs_value(s)]))
                        .collect(),
                ),
            ),
            (
                1,
                Value::Array(b.attests.iter().map(attest_value).collect()),
            ),
            (
                2,
                Value::Array(
                    b.objects
                        .iter()
                        .map(|(t, body)| {
                            Value::Array(vec![
                                Value::Text(t.name().into()),
                                Value::Bytes(body.clone()),
                            ])
                        })
                        .collect(),
                ),
            ),
            (
                3,
                Value::Array(b.policies.iter().map(policy_value).collect()),
            ),
        ])
    }

    pub fn bundle_from_value(v: &Value) -> Result<Bundle> {
        let m = map(v, "bundle")?;
        let mut b = Bundle::default();
        for c in o::array(field(m, 0, "changes")?, "changes")? {
            let pair = o::array(c, "change entry")?;
            if pair.len() != 2 {
                return Err(schema("change entry: expected [change, sigs]"));
            }
            b.changes.push((
                Change::decode(o::bytes(&pair[0], "change")?)?,
                sigs_from(&pair[1])?,
            ));
        }
        for a in o::array(field(m, 1, "attests")?, "attests")? {
            b.attests.push(attest_from(a)?);
        }
        for ob in o::array(field(m, 2, "objects")?, "objects")? {
            let pair = o::array(ob, "object")?;
            if pair.len() != 2 {
                return Err(schema("object: expected [type, body]"));
            }
            let ty = ObjectType::from_name(o::text(&pair[0], "object type")?)
                .ok_or_else(|| schema("unknown object type"))?;
            b.objects
                .push((ty, o::bytes(&pair[1], "object body")?.to_vec()));
        }
        if let Some(ps) = m.get(&3) {
            for p in o::array(ps, "policies")? {
                b.policies.push(policy_from(p)?);
            }
        }
        Ok(b)
    }

    pub fn encode_bundle(b: &Bundle) -> Vec<u8> {
        cbor::encode(&bundle_value(b))
    }
    pub fn decode_bundle(bytes: &[u8]) -> Result<Bundle> {
        bundle_from_value(&cbor::decode(bytes).map_err(ObjectError::from)?)
    }

    pub fn encode_capabilities(id: [u8; 16]) -> Vec<u8> {
        cbor::encode(&Value::map([
            (0, Value::Array(vec![Value::Uint(PROTOCOL_VERSION)])),
            (1, Value::Bytes(id.to_vec())),
            (2, Value::Array(vec![Value::Text("seal".into())])),
        ]))
    }
    pub fn decode_capabilities(bytes: &[u8]) -> Result<[u8; 16]> {
        let v = cbor::decode(bytes).map_err(ObjectError::from)?;
        let m = map(&v, "capabilities")?;
        let versions = o::array(field(m, 0, "versions")?, "versions")?;
        if !versions
            .iter()
            .any(|x| x.as_uint() == Some(PROTOCOL_VERSION))
        {
            return Err(RepoError::Msg(
                "remote does not speak protocol version 1".into(),
            ));
        }
        o::bytes(field(m, 1, "repo id")?, "repo id")?
            .try_into()
            .map_err(|_| schema("repo id: expected 16 bytes"))
    }

    fn tags_value(tags: &[TagRef]) -> Value {
        Value::Array(
            tags.iter()
                .map(|t| {
                    Value::map([
                        (0, Value::Text(t.name.clone())),
                        (1, Value::Bytes(t.state.0.to_vec())),
                        (2, hashes_value(&t.heads)),
                        (3, opt_attest_value(&t.attestation)),
                    ])
                })
                .collect(),
        )
    }
    fn tags_from(v: &Value) -> Result<Vec<TagRef>> {
        let mut out = Vec::new();
        for t in o::array(v, "tags")? {
            let tm = map(t, "tag")?;
            out.push(TagRef {
                name: o::text(field(tm, 0, "name")?, "name")?.to_owned(),
                state: o::oref(field(tm, 1, "state")?, "state")?,
                heads: hashes_from(field(tm, 2, "heads")?)?,
                attestation: opt_attest_from(field(tm, 3, "attestation")?)?,
            });
        }
        Ok(out)
    }

    pub fn encode_refs(id: [u8; 16], resp: &RefsResponse) -> Vec<u8> {
        cbor::encode(&Value::map([
            (
                0,
                Value::Array(
                    resp.refs
                        .iter()
                        .map(|r| {
                            Value::map([
                                (0, Value::Text(r.name.clone())),
                                (1, Value::Bytes(r.state.0.to_vec())),
                                (2, hashes_value(&r.heads)),
                                (3, opt_attest_value(&r.attestation)),
                                (4, r.last_serial.map(Value::Uint).unwrap_or(Value::Null)),
                            ])
                        })
                        .collect(),
                ),
            ),
            (1, Value::Bytes(id.to_vec())),
            (2, opt_policy_value(resp.policy.as_ref())),
            (3, tags_value(&resp.tags)),
            (
                4,
                Value::Array(resp.history.iter().map(policy_value).collect()),
            ),
        ]))
    }
    pub fn decode_refs(bytes: &[u8]) -> Result<([u8; 16], RefsResponse)> {
        let v = cbor::decode(bytes).map_err(ObjectError::from)?;
        let m = map(&v, "refs")?;
        let id: [u8; 16] = o::bytes(field(m, 1, "repo id")?, "repo id")?
            .try_into()
            .map_err(|_| schema("repo id: expected 16 bytes"))?;
        let mut refs = Vec::new();
        for r in o::array(field(m, 0, "refs")?, "refs")? {
            let rm = map(r, "ref")?;
            let ls = field(rm, 4, "last serial")?;
            refs.push(RemoteRef {
                name: o::text(field(rm, 0, "name")?, "name")?.to_owned(),
                state: o::oref(field(rm, 1, "state")?, "state")?,
                heads: hashes_from(field(rm, 2, "heads")?)?,
                attestation: opt_attest_from(field(rm, 3, "attestation")?)?,
                last_serial: if ls.is_null() {
                    None
                } else {
                    Some(o::uint(ls, "last serial")?)
                },
            });
        }
        let policy = match m.get(&2) {
            Some(p) => opt_policy_from(p)?,
            None => None,
        };
        let tags = match m.get(&3) {
            Some(t) => tags_from(t)?,
            None => Vec::new(),
        };
        let mut history = Vec::new();
        if let Some(h) = m.get(&4) {
            for p in o::array(h, "history")? {
                history.push(policy_from(p)?);
            }
        }
        Ok((
            id,
            RefsResponse {
                refs,
                policy,
                tags,
                history,
            },
        ))
    }

    pub fn encode_negotiate(have: &[ChangeHash], want: &[ChangeHash]) -> Vec<u8> {
        cbor::encode(&Value::map([
            (0, hashes_value(have)),
            (1, hashes_value(want)),
        ]))
    }
    pub fn decode_negotiate(bytes: &[u8]) -> Result<(Vec<ChangeHash>, Vec<ChangeHash>)> {
        let v = cbor::decode(bytes).map_err(ObjectError::from)?;
        let m = map(&v, "negotiate")?;
        Ok((
            hashes_from(field(m, 0, "have")?)?,
            hashes_from(field(m, 1, "want")?)?,
        ))
    }

    /// `fetch` request: `{0: [changes], 1: max blob size or null}`.
    pub fn encode_fetch(hs: &[ChangeHash], max_blob: Option<u64>) -> Vec<u8> {
        cbor::encode(&Value::map([
            (0, hashes_value(hs)),
            (1, max_blob.map(Value::Uint).unwrap_or(Value::Null)),
        ]))
    }
    pub fn decode_fetch(bytes: &[u8]) -> Result<(Vec<ChangeHash>, Option<u64>)> {
        let v = cbor::decode(bytes).map_err(ObjectError::from)?;
        let m = map(&v, "fetch")?;
        let max = match m.get(&1) {
            Some(x) if !x.is_null() => Some(o::uint(x, "max blob")?),
            _ => None,
        };
        Ok((hashes_from(field(m, 0, "changes")?)?, max))
    }

    /// `shallow` request: `{0: [heads], 1: depth}`.
    pub fn encode_shallow(hs: &[ChangeHash], depth: u32) -> Vec<u8> {
        cbor::encode(&Value::map([
            (0, hashes_value(hs)),
            (1, Value::Uint(depth as u64)),
        ]))
    }
    pub fn decode_shallow(bytes: &[u8]) -> Result<(Vec<ChangeHash>, u32)> {
        let v = cbor::decode(bytes).map_err(ObjectError::from)?;
        let m = map(&v, "shallow")?;
        Ok((
            hashes_from(field(m, 0, "heads")?)?,
            o::u32_(field(m, 1, "depth")?, "depth")?,
        ))
    }

    pub fn encode_hashes(hs: &[ChangeHash]) -> Vec<u8> {
        cbor::encode(&Value::map([(0, hashes_value(hs))]))
    }
    pub fn decode_hashes(bytes: &[u8]) -> Result<Vec<ChangeHash>> {
        let v = cbor::decode(bytes).map_err(ObjectError::from)?;
        hashes_from(field(map(&v, "hashes")?, 0, "hashes")?)
    }

    pub fn encode_push(
        bundle: &Bundle,
        updates: &[RefUpdate],
        policy: Option<&SignedPolicy>,
        tags: &[TagRef],
    ) -> Vec<u8> {
        cbor::encode(&Value::map([
            (0, bundle_value(bundle)),
            (2, opt_policy_value(policy)),
            (3, tags_value(tags)),
            (
                1,
                Value::Array(
                    updates
                        .iter()
                        .map(|u| {
                            Value::map([
                                (0, Value::Text(u.name.clone())),
                                (1, Value::Bytes(u.old_state.0.to_vec())),
                                (2, Value::Bytes(u.new_state.0.to_vec())),
                                (3, Value::Bool(u.force)),
                                (4, opt_attest_value(&u.attestation)),
                            ])
                        })
                        .collect(),
                ),
            ),
        ]))
    }
    /// A decoded push: bundle, bookmark updates, policy, tags.
    pub type PushParts = (Bundle, Vec<RefUpdate>, Option<SignedPolicy>, Vec<TagRef>);

    pub fn decode_push(bytes: &[u8]) -> Result<PushParts> {
        let v = cbor::decode(bytes).map_err(ObjectError::from)?;
        let m = map(&v, "push")?;
        let bundle = bundle_from_value(field(m, 0, "bundle")?)?;
        let mut updates = Vec::new();
        for u in o::array(field(m, 1, "updates")?, "updates")? {
            let um = map(u, "update")?;
            updates.push(RefUpdate {
                name: o::text(field(um, 0, "name")?, "name")?.to_owned(),
                old_state: o::oref(field(um, 1, "old_state")?, "old_state")?,
                new_state: o::oref(field(um, 2, "new_state")?, "new_state")?,
                force: field(um, 3, "force")?
                    .as_bool()
                    .ok_or_else(|| schema("force: expected bool"))?,
                attestation: opt_attest_from(field(um, 4, "attestation")?)?,
            });
        }
        let policy = match m.get(&2) {
            Some(p) => opt_policy_from(p)?,
            None => None,
        };
        let tags = match m.get(&3) {
            Some(t) => tags_from(t)?,
            None => Vec::new(),
        };
        Ok((bundle, updates, policy, tags))
    }

    pub fn encode_push_response(results: &[RefResult]) -> Vec<u8> {
        cbor::encode(&Value::map([(
            0,
            Value::Array(
                results
                    .iter()
                    .map(|r| {
                        Value::map([
                            (0, Value::Text(r.name.clone())),
                            (1, Value::Bool(r.ok)),
                            (2, Value::Text(r.reason.clone())),
                        ])
                    })
                    .collect(),
            ),
        )]))
    }
    pub fn decode_push_response(bytes: &[u8]) -> Result<Vec<RefResult>> {
        let v = cbor::decode(bytes).map_err(ObjectError::from)?;
        let m = map(&v, "push response")?;
        let mut out = Vec::new();
        for r in o::array(field(m, 0, "results")?, "results")? {
            let rm = map(r, "result")?;
            out.push(RefResult {
                name: o::text(field(rm, 0, "name")?, "name")?.to_owned(),
                ok: field(rm, 1, "ok")?
                    .as_bool()
                    .ok_or_else(|| schema("ok: expected bool"))?,
                reason: o::text(field(rm, 2, "reason")?, "reason")?.to_owned(),
            });
        }
        Ok(out)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::attest::AttestBody;
    use crate::objects::Hlc;

    #[test]
    fn wire_round_trips() {
        let c = crate::objects::tests::sample_change();
        let sk = crate::identity::SecretKey {
            ed_seed: [1; 32],
            ml_seed: [2; 32],
        };
        let id = sk.identity("a", "b", 0);
        let key = id.hash();
        let sig = sk.sign(crate::identity::Domain::Change, &key, &c.hash());
        let seal = Attest::seal([3; 16], vec![c.hash()]);
        let seal_sig = sk.sign(crate::identity::Domain::Attest, &key, &seal.hash());
        let policy = Policy::single_root([3; 16], id.clone(), 99);
        let psig = sk.sign(crate::identity::Domain::Policy, &key, &policy.hash());
        let bundle = Bundle {
            changes: vec![(c.clone(), vec![sig.clone()])],
            attests: vec![SignedAttest {
                attest: seal.clone(),
                sigs: vec![seal_sig],
            }],
            objects: vec![
                (ObjectType::Identity, id.encode()),
                (ObjectType::Chunk, b"xyz".to_vec()),
            ],
            policies: vec![SignedPolicy {
                policy: policy.clone(),
                sigs: vec![psig.clone()],
            }],
        };
        let d = wire::decode_bundle(&wire::encode_bundle(&bundle)).unwrap();
        assert_eq!(d.changes, bundle.changes);
        assert_eq!(d.attests, bundle.attests);
        assert_eq!(d.objects, bundle.objects);
        assert_eq!(d.policies, bundle.policies);

        let att = Attest {
            repo: [3; 16],
            hlc: Hlc::default(),
            body: AttestBody::Ref {
                name: "main".into(),
                old_state: ObjectRef([1; 32]),
                new_state: ObjectRef([2; 32]),
                serial: 4,
            },
        };
        let refs = vec![
            RemoteRef {
                name: "main".into(),
                state: ObjectRef([2; 32]),
                heads: vec![c.hash()],
                attestation: Some(SignedAttest {
                    attest: att.clone(),
                    sigs: vec![sig.clone()],
                }),
                last_serial: Some(4),
            },
            RemoteRef {
                name: "dev".into(),
                state: ObjectRef([5; 32]),
                heads: vec![],
                attestation: None,
                last_serial: None,
            },
        ];
        let tag = TagRef {
            name: "v1".into(),
            state: ObjectRef([2; 32]),
            heads: vec![c.hash()],
            attestation: None,
        };
        let resp = RefsResponse {
            refs,
            policy: Some(SignedPolicy {
                policy: policy.clone(),
                sigs: vec![psig.clone()],
            }),
            tags: vec![tag.clone()],
            history: vec![SignedPolicy {
                policy: policy.clone(),
                sigs: vec![],
            }],
        };
        let (id_back, back) = wire::decode_refs(&wire::encode_refs([3; 16], &resp)).unwrap();
        assert_eq!(id_back, [3; 16]);
        assert_eq!(back.refs.len(), 2);
        assert_eq!(back.refs[0].attestation.as_ref().unwrap().attest, att);
        assert_eq!(back.refs[1].last_serial, None);
        assert_eq!(back.policy.as_ref().unwrap().policy, policy);
        assert_eq!(back.history, resp.history);
        assert_eq!(back.tags, vec![tag.clone()]);

        let (h, w) = wire::decode_negotiate(&wire::encode_negotiate(
            &[ObjectRef([1; 32])],
            &[ObjectRef([2; 32])],
        ))
        .unwrap();
        assert_eq!((h, w), (vec![ObjectRef([1; 32])], vec![ObjectRef([2; 32])]));
        assert_eq!(
            wire::decode_hashes(&wire::encode_hashes(&[c.hash()])).unwrap(),
            vec![c.hash()]
        );
        assert_eq!(
            wire::decode_fetch(&wire::encode_fetch(&[c.hash()], Some(4096))).unwrap(),
            (vec![c.hash()], Some(4096))
        );
        assert_eq!(
            wire::decode_fetch(&wire::encode_fetch(&[], None)).unwrap(),
            (vec![], None)
        );
        assert_eq!(
            wire::decode_shallow(&wire::encode_shallow(&[c.hash()], 3)).unwrap(),
            (vec![c.hash()], 3)
        );
        // An old-style fetch request without the filter field still decodes.
        assert_eq!(
            wire::decode_fetch(&wire::encode_hashes(&[c.hash()])).unwrap(),
            (vec![c.hash()], None)
        );

        let up = RefUpdate {
            name: "main".into(),
            old_state: ObjectRef([1; 32]),
            new_state: ObjectRef([2; 32]),
            force: true,
            attestation: Some(SignedAttest {
                attest: att,
                sigs: vec![sig],
            }),
        };
        let sp = SignedPolicy {
            policy,
            sigs: vec![psig],
        };
        let (b2, ups, pol, tags) = wire::decode_push(&wire::encode_push(
            &bundle,
            std::slice::from_ref(&up),
            Some(&sp),
            std::slice::from_ref(&tag),
        ))
        .unwrap();
        assert_eq!(pol, Some(sp));
        assert_eq!(tags, vec![tag]);
        assert_eq!(b2.changes.len(), 1);
        assert_eq!(ups[0].name, "main");
        assert!(ups[0].force);
        assert_eq!(ups[0].attestation, up.attestation);
        let res = vec![RefResult {
            name: "main".into(),
            ok: false,
            reason: "stale".into(),
        }];
        assert_eq!(
            wire::decode_push_response(&wire::encode_push_response(&res)).unwrap(),
            res
        );
        assert_eq!(
            wire::decode_capabilities(&wire::encode_capabilities([7; 16])).unwrap(),
            [7; 16]
        );
    }
}
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