fix(node): bound GraphQL query cost

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

@@ -3,7 +3,7 @@ pub mod query;
 pub mod subscription;
 pub mod types;
 
-use async_graphql::Schema;
+use async_graphql::{Schema, SchemaBuilder};
 use std::sync::Arc;
 
 use crate::db::Db;
@@ -14,6 +14,21 @@ use subscription::SubscriptionRoot;
 
 pub type GitlawbSchema = Schema<QueryRoot, MutationRoot, SubscriptionRoot>;
 
+// Keep ordinary schema discovery and application queries usable while
+// bounding validation work and the number of resolver selections per request.
+const GRAPHQL_MAX_COMPLEXITY: usize = 400;
+// The current public schema is shallow; this leaves headroom for composed
+// clients without allowing recursively nested documents to grow unchecked.
+const GRAPHQL_MAX_DEPTH: usize = 12;
+
+fn apply_query_limits<Query, Mutation, Subscription>(
+    builder: SchemaBuilder<Query, Mutation, Subscription>,
+) -> SchemaBuilder<Query, Mutation, Subscription> {
+    builder
+        .limit_complexity(GRAPHQL_MAX_COMPLEXITY)
+        .limit_depth(GRAPHQL_MAX_DEPTH)
+}
+
 /// Client-facing message for GraphQL resolver failures that wrap a real
 /// `sqlx::Error`. The real error is logged server-side; never put sqlx/Postgres
 /// detail in the GraphQL `errors` array (#250).
@@ -81,7 +96,7 @@ pub fn build_schema(
     ref_update_tx: tokio::sync::broadcast::Sender<RefUpdateBroadcast>,
     task_event_tx: tokio::sync::broadcast::Sender<TaskEventBroadcast>,
 ) -> GitlawbSchema {
-    Schema::build(QueryRoot, MutationRoot, SubscriptionRoot)
+    apply_query_limits(Schema::build(QueryRoot, MutationRoot, SubscriptionRoot))
         .data(db)
         .data(ref_update_tx)
         .data(task_event_tx)
@@ -91,6 +106,8 @@ pub fn build_schema(
 #[cfg(test)]
 mod tests {
     use super::*;
+    use async_graphql::{EmptyMutation, EmptySubscription, Object, Value};
+    use std::sync::atomic::{AtomicUsize, Ordering};
 
     #[test]
     fn graphql_db_err_opaques_sqlx_chain() {
@@ -160,6 +177,175 @@ mod tests {
         assert!(!err.message.contains("failed to open"));
     }
 
+    fn production_test_schema() -> GitlawbSchema {
+        let pool = sqlx::postgres::PgPoolOptions::new()
+            .connect_lazy("postgres://localhost/unused")
+            .unwrap();
+        build_schema(
+            Arc::new(Db::for_testing(pool)),
+            tokio::sync::broadcast::channel(1).0,
+            tokio::sync::broadcast::channel(1).0,
+        )
+    }
+
+    #[tokio::test]
+    async fn production_limits_reject_mutation_aliases_and_large_lists() {
+        let schema = production_test_schema();
+        for field in [
+            "claimTask(id: \"missing\", assigneeDid: \"did:key:test\") { id }",
+            "refUpdates(limit: 200) { repo }",
+            "tasks(limit: 200) { id }",
+        ] {
+            let count = if field.starts_with("claim") { 8 } else { 2 };
+            let fields = (0..count)
+                .map(|n| format!("r{n}: {field}"))
+                .collect::<Vec<_>>()
+                .join(" ");
+            let prefix = if field.starts_with("claim") {
+                "mutation"
+            } else {
+                "query"
+            };
+            let response = schema.execute(format!("{prefix} {{ {fields} }}")).await;
+            assert_eq!(response.errors.len(), 1, "{:?}", response.errors);
+            assert_eq!(response.errors[0].message, "Query is too complex.");
+        }
+    }
+
+    #[tokio::test]
+    async fn seven_root_aliases_are_accepted() {
+        struct Root(Arc<AtomicUsize>);
+        #[Object]
+        impl Root {
+            #[graphql(complexity = "50 + child_complexity")]
+            async fn repos(&self) -> Vec<Nested> {
+                self.0.fetch_add(1, Ordering::Relaxed);
+                vec![Nested]
+            }
+        }
+        let calls = Arc::new(AtomicUsize::new(0));
+        let schema = apply_query_limits(Schema::build(
+            Root(calls.clone()),
+            EmptyMutation,
+            EmptySubscription,
+        ))
+        .finish();
+        let fields = (0..7)
+            .map(|n| format!("r{n}: repos {{ value }}"))
+            .collect::<Vec<_>>()
+            .join(" ");
+        let response = schema.execute(format!("{{ {fields} }}")).await;
+        assert!(response.errors.is_empty(), "{:?}", response.errors);
+        assert_eq!(calls.load(Ordering::Relaxed), 7);
+    }
+
+    #[tokio::test]
+    async fn expensive_root_aliases_are_rejected_before_database_access() {
+        // Use the production builder with a lazy pool: rejection must precede DB access.
+        let schema = production_test_schema();
+        let fields = (0..8)
+            .map(|n| format!("r{n}: repos {{ name }}"))
+            .collect::<Vec<_>>()
+            .join(" ");
+
+        let response = schema.execute(format!("{{ {fields} }}")).await;
+
+        assert_eq!(response.data, Value::Null);
+        assert_eq!(response.errors.len(), 1);
+        assert_eq!(response.errors[0].message, "Query is too complex.");
+    }
+
+    #[tokio::test]
+    async fn ordinary_schema_introspection_remains_available() {
+        let schema =
+            apply_query_limits(Schema::build(QueryRoot, EmptyMutation, EmptySubscription)).finish();
+        let response = schema
+            .execute(
+                r#"
+                query IntrospectionQuery {
+                    __schema {
+                        queryType {
+                            name
+                            fields {
+                                name
+                                type {
+                                    kind
+                                    name
+                                    ofType { kind name }
+                                }
+                            }
+                        }
+                    }
+                }
+                "#,
+            )
+            .await;
+
+        assert!(
+            response.errors.is_empty(),
+            "graphql errors: {:?}",
+            response.errors
+        );
+        assert_ne!(response.data, Value::Null);
+    }
+
+    #[derive(Clone, Copy)]
+    struct Nested;
+
+    #[Object]
+    impl Nested {
+        async fn child(&self) -> Nested {
+            Nested
+        }
+
+        async fn value(&self) -> i32 {
+            1
+        }
+    }
+
+    struct CountingQuery(Arc<AtomicUsize>);
+
+    #[Object]
+    impl CountingQuery {
+        async fn nested(&self) -> Nested {
+            self.0.fetch_add(1, Ordering::Relaxed);
+            Nested
+        }
+    }
+
+    #[tokio::test]
+    async fn query_depth_limit_accepts_twelve_and_rejects_thirteen() {
+        let calls = Arc::new(AtomicUsize::new(0));
+        let schema = apply_query_limits(Schema::build(
+            CountingQuery(Arc::clone(&calls)),
+            EmptyMutation,
+            EmptySubscription,
+        ))
+        .finish();
+        let query_at_depth = |depth: usize| {
+            let selection = (2..depth).fold("value".to_string(), |selection, _| {
+                format!("child {{ {selection} }}")
+            });
+            format!("{{ nested {{ {selection} }} }}")
+        };
+
+        let accepted = schema.execute(query_at_depth(GRAPHQL_MAX_DEPTH)).await;
+
+        assert!(
+            accepted.errors.is_empty(),
+            "depth {GRAPHQL_MAX_DEPTH} should be accepted: {:?}",
+            accepted.errors
+        );
+        assert_eq!(calls.swap(0, Ordering::Relaxed), 1);
+
+        let rejected = schema.execute(query_at_depth(GRAPHQL_MAX_DEPTH + 1)).await;
+
+        assert_eq!(rejected.data, Value::Null);
+        assert_eq!(rejected.errors.len(), 1);
+        assert_eq!(rejected.errors[0].message, "Query is nested too deep.");
+        assert_eq!(calls.load(Ordering::Relaxed), 0);
+    }
+
     /// Every `.map_err(` in the GraphQL query/mutation resolvers must route
     /// through the opaque helpers, or discard the error (`|_|`). Same source-
     /// scrape pattern as `api::authz_guard` (#255 review).

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

@@ -22,6 +22,7 @@ pub struct MutationRoot;
 
 #[Object]
 impl MutationRoot {
+    #[graphql(complexity = "50 + child_complexity")]
     async fn create_task(
         &self,
         ctx: &Context<'_>,
@@ -58,6 +59,7 @@ impl MutationRoot {
         Ok(AgentTaskType::from(task))
     }
 
+    #[graphql(complexity = "50 + child_complexity")]
     async fn claim_task(
         &self,
         ctx: &Context<'_>,
@@ -87,6 +89,7 @@ impl MutationRoot {
         Ok(AgentTaskType::from(task))
     }
 
+    #[graphql(complexity = "50 + child_complexity")]
     async fn complete_task(
         &self,
         ctx: &Context<'_>,
@@ -129,6 +132,7 @@ impl MutationRoot {
         Ok(AgentTaskType::from(task))
     }
 
+    #[graphql(complexity = "50 + child_complexity")]
     async fn fail_task(
         &self,
         ctx: &Context<'_>,

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

@@ -9,6 +9,9 @@ pub struct QueryRoot;
 
 #[Object]
 impl QueryRoot {
+    // DB-backed roots carry a base cost so aliases consume the request budget
+    // even when each alias selects only one inexpensive response field.
+    #[graphql(complexity = "50 + child_complexity")]
     async fn repos(&self, ctx: &Context<'_>) -> Result<Vec<RepoType>> {
         let db = ctx.data_unchecked::<Arc<Db>>();
         let repos = db
@@ -45,6 +48,7 @@ impl QueryRoot {
             .collect())
     }
 
+    #[graphql(complexity = "50 + (limit.clamp(0, 200) as usize) * child_complexity")]
     async fn ref_updates(
         &self,
         ctx: &Context<'_>,
@@ -105,6 +109,7 @@ impl QueryRoot {
         Ok(resolved)
     }
 
+    #[graphql(complexity = "50 + (limit.clamp(0, 200) as usize) * child_complexity")]
     async fn tasks(
         &self,
         ctx: &Context<'_>,
@@ -128,6 +133,7 @@ impl QueryRoot {
         Ok(tasks.into_iter().map(AgentTaskType::from).collect())
     }
 
+    #[graphql(complexity = "50 + child_complexity")]
     async fn task(&self, ctx: &Context<'_>, id: String) -> Result<Option<AgentTaskType>> {
         let db = ctx.data_unchecked::<Arc<Db>>();
         let t = db