feat: mvp auth protocol

crates/distribution/src/auth.rs

@@ -0,0 +1,145 @@
+use std::collections::HashSet;
+use std::fmt;
+
+use serde::{Deserialize, Serialize};
+
+use crate::types::{NodeId, Signature};
+
+// ─── ContentHash ────────────────────────────────────────────────────────────
+
+/// A 32-byte blake3 digest used as content address for chunks and manifests.
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
+pub struct ContentHash(pub [u8; 32]);
+
+impl fmt::Debug for ContentHash {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "ContentHash(")?;
+        for b in &self.0[..4] {
+            write!(f, "{:02x}", b)?;
+        }
+        write!(f, "\u{2026})")
+    }
+}
+
+// ─── DatastoreAction ────────────────────────────────────────────────────────
+
+/// An action a client wants to perform on the datastore.
+///
+/// Carried inside a `SignedRequestPayload` for browser-relay auth (Auth Path 2).
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum DatastoreAction {
+    Put {
+        path: String,
+        content_hash: ContentHash,
+        size_bytes: u64,
+        tags: std::collections::BTreeMap<String, String>,
+    },
+    Get {
+        path: String,
+    },
+    Delete {
+        path: String,
+    },
+    List {
+        prefix: Option<String>,
+    },
+}
+
+// ─── SignedRequestPayload ───────────────────────────────────────────────────
+
+/// The signable payload of a client request.
+///
+/// Serialized canonically (serde_json) and signed by the client's ed25519 key.
+/// Includes timestamp and nonce for replay protection.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct SignedRequestPayload {
+    pub action: DatastoreAction,
+    /// Unix timestamp in seconds.
+    pub timestamp: u64,
+    /// 16 random bytes — prevents replay within the timestamp window.
+    pub nonce: [u8; 16],
+}
+
+// ─── SignedRequest ──────────────────────────────────────────────────────────
+
+/// A signed request envelope for browser-relay auth (Auth Path 2).
+///
+/// The relay forwards this opaquely — it cannot forge, modify, or replay it.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct SignedRequest {
+    pub payload: SignedRequestPayload,
+    /// The client's ed25519 public key.
+    pub public_key: NodeId,
+    /// ed25519 signature over the canonical serialization of `payload`.
+    pub signature: Signature,
+}
+
+// ─── AccessControlList ──────────────────────────────────────────────────────
+
+/// The datastore's access control list.
+///
+/// Persisted as `acl.json` alongside the datastore's `storage_path`.
+/// The owner always has implicit full access.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct AccessControlList {
+    /// The datastore owner's public key — always has full access.
+    pub owner: NodeId,
+    /// Explicitly authorized client keys.
+    pub authorized_keys: HashSet<NodeId>,
+}
+
+// ─── AuthzResult ────────────────────────────────────────────────────────────
+
+/// The outcome of an authorization check.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum AuthzResult {
+    Allowed,
+    Denied(DeniedReason),
+}
+
+/// Why a request was denied.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub enum DeniedReason {
+    /// The key is not in the ACL.
+    NotAuthorized,
+    /// The ed25519 signature is invalid.
+    InvalidSignature,
+    /// The request timestamp is outside the ±300s window.
+    RequestExpired,
+    /// The nonce has already been seen within the time window.
+    ReplayDetected,
+}
+
+// ─── AuthzEngine ────────────────────────────────────────────────────────────
+
+/// Authorization engine — checks requests against the ACL and replay state.
+///
+/// Sits at the edge of the actor system (Auth Gate) and decides whether
+/// to accept or reject external requests before they reach the actors.
+#[derive(Debug)]
+pub struct AuthzEngine {
+    pub acl: AccessControlList,
+    // Nonce tracking and other runtime state will be added during implementation.
+}
+
+impl AuthzEngine {
+    /// Check whether a `NodeId` is authorized (connection-level, Auth Path 1).
+    pub fn check_node(&self, _node_id: &NodeId) -> AuthzResult {
+        todo!()
+    }
+
+    /// Verify and authorize a signed request (Auth Path 2).
+    pub fn check_signed_request(&self, _request: &SignedRequest) -> AuthzResult {
+        todo!()
+    }
+
+    /// Grant access to a `NodeId`. Owner-only operation.
+    pub fn grant(&mut self, _requester: &NodeId, _key: NodeId) -> Result<(), DeniedReason> {
+        todo!()
+    }
+
+    /// Revoke access from a `NodeId`. Owner-only operation.
+    pub fn revoke(&mut self, _requester: &NodeId, _key: NodeId) -> Result<(), DeniedReason> {
+        todo!()
+    }
+}

crates/distribution/src/crypto.rs

@@ -1,5 +1,6 @@
 use ed25519_dalek::{Signer, Verifier};
 
+use crate::auth::{SignedRequest, SignedRequestPayload};
 use crate::types::{DirectoryEntry, DirectoryEntryPayload, NodeId, Signature};
 
 // ─── Keypair ────────────────────────────────────────────────────────────────
@@ -41,6 +42,13 @@ impl Keypair {
         Signature(sig.to_bytes())
     }
 
+    /// Sign a request payload, returning a complete `SignedRequest` envelope.
+    ///
+    /// Used by clients for Auth Path 2 (browser relay).
+    pub fn sign_request(&self, _payload: &SignedRequestPayload) -> SignedRequest {
+        todo!()
+    }
+
     /// Sign a directory entry payload, returning a complete `DirectoryEntry`.
     pub fn sign_directory_entry(
         &self,
@@ -74,6 +82,14 @@ pub fn verify(node_id: &NodeId, msg: &[u8], sig: &Signature) -> bool {
     vk.verify(msg, &signature).is_ok()
 }
 
+/// Verify a `SignedRequest`'s signature against its embedded `public_key`.
+///
+/// Checks only signature validity — does NOT check timestamp, nonce, or ACL.
+/// Use `AuthzEngine::check_signed_request` for full verification.
+pub fn verify_signed_request(_request: &SignedRequest) -> bool {
+    todo!()
+}
+
 /// Verify a `DirectoryEntry`'s signature against its embedded `node_id`.
 pub fn verify_directory_entry(entry: &DirectoryEntry) -> bool {
     let payload = entry.payload();

crates/distribution/src/lib.rs

@@ -14,3 +14,4 @@ pub mod snapshot;
 pub mod driver;
 #[cfg(feature = "iroh")]
 pub mod iroh_driver;
+pub mod auth;