fix(node): owner-gate create_task repo_id against hosted repos

crates/gitlawb-node/src/api/mod.rs

@@ -80,15 +80,20 @@ pub(crate) fn did_matches(a: &str, b: &str) -> bool {
     !ka.contains(':') && !kb.contains(':') && ka == kb
 }
 
+/// Client-facing denial shared by every repo-owner gate copy. `require_repo_owner`
+/// renders it as `AppError::Forbidden`; a handler that emits its own
+/// `(StatusCode, Json)` envelope instead of `AppError` (e.g.
+/// `api::tasks::create_task`) must use this constant too, so two copies of one
+/// gate cannot drift in observable output.
+pub(crate) const REPO_OWNER_ONLY_MESSAGE: &str = "only the repo owner can perform this action";
+
 /// 403 unless `caller` is the repo owner. Uses [`did_matches`] so the owner check
 /// and the author check (close policy) share one normalization.
 pub(crate) fn require_repo_owner(record: &RepoRecord, caller: &str) -> Result<()> {
     if did_matches(caller, &record.owner_did) {
         Ok(())
     } else {
-        Err(AppError::Forbidden(
-            "only the repo owner can perform this action".into(),
-        ))
+        Err(AppError::Forbidden(REPO_OWNER_ONLY_MESSAGE.into()))
     }
 }
 
@@ -223,6 +228,11 @@ mod authz_guard {
             (events, "list_repo_events", "authorize_repo_read("),
             // Bucket C — signer-self: the acting DID is matched/bound to auth.0
             (tasks, "create_task", "did_matches("),
+            // #496: create_task is signer-self AND owner-when-repo-scoped — a
+            // repo_id naming a hosted repo admits tasks only from its owner.
+            // Both halves are pinned: the did_matches row guards the signer
+            // binding, this one the repo-ownership gate.
+            (tasks, "create_task", "require_repo_owner("),
             (tasks, "claim_task", "did_matches("),
             (tasks, "complete_task", "did_matches("),
             (tasks, "fail_task", "did_matches("),

crates/gitlawb-node/src/api/tasks.rs

@@ -30,6 +30,20 @@ fn forbidden(msg: &str) -> (StatusCode, Json<Value>) {
     )
 }
 
+/// 500 in this module's error shape with an opaque body: the real error is
+/// logged server-side and never serialized (#250), matching the `db_error`
+/// envelope `AppError::Db` renders.
+fn db_error(e: anyhow::Error) -> (StatusCode, Json<Value>) {
+    tracing::error!(error = %format!("{e:#}"), "task repo gate database error");
+    (
+        StatusCode::INTERNAL_SERVER_ERROR,
+        Json(json!({
+            "error": "db_error",
+            "message": crate::error::DB_ERROR_MESSAGE,
+        })),
+    )
+}
+
 // ── Request / response types ──────────────────────────────────────────────────
 
 #[derive(Deserialize)]
@@ -101,6 +115,37 @@ pub async fn create_task(
     if !crate::api::did_matches(&auth.0, &body.delegator_did) {
         return Err(forbidden("delegator_did must be the authenticated signer"));
     }
+    // #496: a caller-supplied repo_id must name a repo the caller owns. Without
+    // this, any signed caller can plant a task — payload and UCAN included —
+    // under a foreign repo id, where the named assignee can claim it. Resolve
+    // the id against hosted repos: a hosted, non-quarantined repo admits tasks
+    // only from its owner (403 otherwise). An id naming no hosted repo
+    // (unknown, or quarantined — which is hidden as if it did not exist, so
+    // 403ing it would confirm a real id) is stored verbatim as an opaque
+    // label: this is a write gate and does not bind an unresolved id to a
+    // repo. Task reads are caller-independent on this base (the list endpoints
+    // are not repo-scoped), before and after this change. The 403-vs-201 split
+    // between a hosted repo id and an unknown one is itself a one-bit oracle —
+    // a stranger holding a private repo's id learns it is hosted here — but
+    // denying foreign repos requires drawing exactly that line, and repo ids
+    // already surface via the task list on this base. Repo-less tasks are
+    // unaffected.
+    if let Some(repo_id) = body.repo_id.as_deref() {
+        let record = state.db.get_repo_by_id(repo_id).await.map_err(db_error)?;
+        if let Some(record) = record {
+            let quarantined = state
+                .db
+                .is_repo_quarantined(&record.id)
+                .await
+                .map_err(db_error)?;
+            if !quarantined && crate::api::require_repo_owner(&record, &auth.0).is_err() {
+                // Same denial text the GraphQL copy relays from
+                // `require_repo_owner`, so the two copies of this gate do not
+                // disagree in observable output.
+                return Err(forbidden(crate::api::REPO_OWNER_ONLY_MESSAGE));
+            }
+        }
+    }
     let now = Utc::now().to_rfc3339();
     let task = AgentTask {
         id: Uuid::new_v4().to_string(),

crates/gitlawb-node/src/graphql/mutation.rs

@@ -36,6 +36,33 @@ impl MutationRoot {
         }
         let delegator_did = caller.to_string();
         let db = ctx.data_unchecked::<Arc<Db>>();
+        // #496: same write gate as the REST handler — a repo_id naming a
+        // hosted, non-quarantined repo admits tasks only from its owner, so a
+        // stranger cannot file under a foreign repo id. An id naming no hosted
+        // repo (unknown, or quarantined — hidden as if it did not exist) is
+        // stored verbatim as an opaque label; the gate does not bind an
+        // unresolved id to a repo. Task reads are caller-independent on this
+        // base (the tasks resolver is not repo-scoped), before and after this
+        // change. As in tasks.rs, the success-vs-denial split between a hosted
+        // repo id and an unknown one is itself a one-bit oracle — a stranger
+        // holding a private repo's id learns it is hosted here — but denying
+        // foreign repos requires drawing exactly that line.
+        if let Some(repo_id) = input.repo_id.as_deref() {
+            let record = db
+                .get_repo_by_id(repo_id)
+                .await
+                .map_err(crate::graphql::graphql_db_err)?;
+            if let Some(record) = record {
+                let quarantined = db
+                    .is_repo_quarantined(&record.id)
+                    .await
+                    .map_err(crate::graphql::graphql_db_err)?;
+                if !quarantined {
+                    crate::api::require_repo_owner(&record, caller)
+                        .map_err(crate::graphql::graphql_app_err)?;
+                }
+            }
+        }
         let now = Utc::now().to_rfc3339();
         let task = AgentTask {
             id: Uuid::new_v4().to_string(),
@@ -332,4 +359,158 @@ mod tests {
             errors(&resp)
         );
     }
+
+    /// #496 (GraphQL): createTask applies the same repo-ownership gate as the
+    /// REST handler — a stranger naming a hosted repo is rejected without
+    /// persisting anything, while the owner files. The quarantined and
+    /// unknown-id arms are pinned here too, so this copy of the gate cannot
+    /// regress silently.
+    #[sqlx::test]
+    async fn create_task_rejects_foreign_repo_id(pool: PgPool) {
+        let state = crate::test_support::test_state(pool).await;
+        let owner = "did:key:zGQLTASKOWNERAAAAAAAAAAAAAAAAAAAAAAAAAA";
+        let stranger = "did:key:zGQLTASKSTRANGERBBBBBBBBBBBBBBBBBBBBBB";
+        let now = chrono::Utc::now();
+        let repo = crate::db::RepoRecord {
+            id: uuid::Uuid::new_v4().to_string(),
+            name: "gql-task-gate-repo".to_string(),
+            owner_did: owner.to_string(),
+            description: None,
+            is_public: true,
+            default_branch: "main".to_string(),
+            created_at: now,
+            updated_at: now,
+            disk_path: "/tmp/gql-task-gate-repo".to_string(),
+            forked_from: None,
+            machine_id: None,
+        };
+        state.db.create_repo(&repo).await.expect("seed repo");
+        let schema = state.graphql_schema.as_ref();
+
+        let q = |actor: &str| {
+            format!(
+                r#"mutation {{ createTask(delegatorDid: "{actor}", input: {{ kind: "build", capability: "repo:write", repoId: "{}" }}) {{ id }} }}"#,
+                repo.id
+            )
+        };
+
+        // Stranger signs as themselves (so the signer binding passes) but
+        // names the victim's repo → rejected by the ownership gate, leaking
+        // nothing about the repo.
+        let resp = schema
+            .execute(Request::new(q(stranger)).data(AuthenticatedDid(stranger.into())))
+            .await;
+        let errs = errors(&resp);
+        assert!(
+            errs.contains(crate::api::REPO_OWNER_ONLY_MESSAGE),
+            "a non-owner must not file under a foreign repo id (shared denial text): {errs}"
+        );
+        assert!(
+            !errs.contains(&repo.id) && !errs.contains(owner),
+            "denial must leak nothing about the repo: {errs}"
+        );
+
+        // The denial must not persist: no task row may carry the victim's
+        // repo id afterwards.
+        let stored = state
+            .db
+            .list_tasks(None, None, 50)
+            .await
+            .expect("list tasks");
+        assert!(
+            stored
+                .iter()
+                .all(|t| t.repo_id.as_deref() != Some(repo.id.as_str())),
+            "a denied write must not leave a task under the foreign repo id"
+        );
+
+        // The owner files under their own repo id.
+        let resp = schema
+            .execute(Request::new(q(owner)).data(AuthenticatedDid(owner.into())))
+            .await;
+        assert!(
+            errors(&resp).is_empty(),
+            "the owner should file against their repo: {}",
+            errors(&resp)
+        );
+
+        // Unknown repo ids stay accepted as opaque labels.
+        let q_unknown = format!(
+            r#"mutation {{ createTask(delegatorDid: "{stranger}", input: {{ kind: "build", capability: "repo:write", repoId: "no-such-repo-id" }}) {{ id }} }}"#
+        );
+        let resp = schema
+            .execute(Request::new(q_unknown).data(AuthenticatedDid(stranger.into())))
+            .await;
+        assert!(
+            errors(&resp).is_empty(),
+            "an id naming no hosted repo stays an opaque label: {}",
+            errors(&resp)
+        );
+
+        // A quarantined repo id is treated as unknown (accepted, never a 403
+        // that would confirm the id names a real repo). This pins the
+        // `!quarantined` arm on this copy of the gate.
+        state
+            .db
+            .set_repo_quarantine(&repo.id, true)
+            .await
+            .expect("quarantine");
+        let resp = schema
+            .execute(Request::new(q(stranger)).data(AuthenticatedDid(stranger.into())))
+            .await;
+        assert!(
+            errors(&resp).is_empty(),
+            "a quarantined repo id must not 403 (existence oracle): {}",
+            errors(&resp)
+        );
+    }
+
+    /// #496 (GraphQL): a repo-lookup fault in createTask's gate must stay
+    /// opaque. Dropping a column `get_repo_by_id` selects faults that lookup;
+    /// the resolver must return the fixed DB message and leak no schema text
+    /// (#250), as `create_task_db_error_message_is_opaque` pins for the
+    /// agent_tasks fault.
+    #[sqlx::test]
+    async fn create_task_gate_repo_lookup_fault_is_opaque(pool: PgPool) {
+        let state = crate::test_support::test_state(pool.clone()).await;
+        let owner = "did:key:zGQLTASKFAULTOWNERAAAAAAAAAAAAAAAAAAAAAAAA";
+        let now = chrono::Utc::now();
+        let repo = crate::db::RepoRecord {
+            id: uuid::Uuid::new_v4().to_string(),
+            name: "gql-task-gate-fault-repo".to_string(),
+            owner_did: owner.to_string(),
+            description: None,
+            is_public: true,
+            default_branch: "main".to_string(),
+            created_at: now,
+            updated_at: now,
+            disk_path: "/tmp/gql-task-gate-fault-repo".to_string(),
+            forked_from: None,
+            machine_id: None,
+        };
+        state.db.create_repo(&repo).await.expect("seed repo");
+
+        sqlx::query("ALTER TABLE repos DROP COLUMN machine_id")
+            .execute(&pool)
+            .await
+            .expect("drop machine_id");
+
+        let q = format!(
+            r#"mutation {{ createTask(delegatorDid: "{owner}", input: {{ kind: "build", capability: "repo:write", repoId: "{}" }}) {{ id }} }}"#,
+            repo.id
+        );
+        let resp = state
+            .graphql_schema
+            .execute(Request::new(&q).data(AuthenticatedDid(owner.into())))
+            .await;
+        let errs = errors(&resp);
+        assert!(
+            errs.contains(crate::graphql::GRAPHQL_DB_ERROR_MESSAGE),
+            "gate sqlx fault must be opaque: {errs}"
+        );
+        assert!(
+            !errs.contains("machine_id") && !errs.contains("column"),
+            "schema text leaked through the gate: {errs}"
+        );
+    }
 }