Graphql Introspection Abuse in Axum (Rust)

GraphQL introspection is a standard query capability that returns the schema of a GraphQL service. In Axum applications written in Rust, introspection is often enabled during development to aid tooling, but it can remain exposed in production. When introspection is reachable without authentication, an attacker can programmatically discover types, queries, and mutations, which exposes implementation details useful for crafting further attacks such as BOLA/IDOR or Property Authorization abuse.

In Axum, GraphQL endpoints are typically implemented using libraries such as async-graphql or juniper. If the schema is served at a route like /graphql and introspection is enabled, an unauthenticated HTTP POST with a query like { __schema { queryType { name } } } will return the schema. This becomes a risk when combined with other issues such as weak input validation or missing rate limiting, because exposed schema information lowers the effort required for those attacks.

The risk is not only informational. For example, knowing the exact names of queries and objects can help an attacker refine BOLA/IDOR probes by targeting specific identifiers or relationships. In Rust services, the presence of debug features or conditional schema builds can unintentionally keep introspection enabled in release builds. MiddleBrick’s checks for GraphQL endpoints include active introspection probing and cross-referencing findings with the OpenAPI/Swagger spec when available, ensuring that this vector is surfaced alongside other security checks.

Remediation focuses on access control and build configuration. Introspection should be restricted to trusted internal tooling and never exposed broadly on public endpoints. In Axum, this means explicitly enabling introspection only in development profiles and enforcing authentication or IP controls before the GraphQL handler is invoked. The following Rust code examples show how to configure introspection conditionally and how to disable it in production builds.

// src/main.rs
use axum::routing::post;
use axum::Router;
use async_graphql::{Schema, EmptySubscription, http::GraphiQL};
use async_graphql::http::GraphQLPlaygroundSource;
use std::net::SocketAddr;

// Define your data context and schema as usual.
struct QueryRoot;

#[async_graphql::Object]
impl QueryRoot {
    async fn hello(&self) -> &str {
        "world"
    }
}

// Build schema with introspection allowed based on feature flags or environment.
fn build_schema(enable_introspection: bool) -> Schema {
    let schema = async_graphql::Schema::build(
        QueryRoot,
        EmptySubscription,
    )
    // Conditional introspection: only enable when explicitly requested.
    .enable_introspection(enable_introspection)
    .finish();
    schema
}

#[tokio::main]
async fn main() {
    // In production, read from environment and default to disabled.
    let introspection_enabled = std::env::var("ENABLE_GRAPHQL_INTROSPECTION")
        .map(|v| v == "true")
        .unwrap_or(false);

    let schema = build_schema(introspection_enabled);

    let app = Router::new()
        .route("/graphql", post(schema.clone().into_make_service()))
        // Serve GraphiQL only when introspection is enabled and in a safe context.
        .route("/graphiql", get(|| async { GraphiQL::new("/graphql", None) }));

    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    axum::Server::bind(&addr)
        .serve(app.into_make_service())
        .await
        .unwrap();
}

For services using the Juniper crate, the approach is similar by controlling the GraphQL playground and introspection settings at runtime:

// src/main.rs
use axum::{routing::get, Router};
use juniper_axum::{graphql, GraphQLRequest, GraphQLResponse};
use std::net::SocketAddr;

struct QueryRoot;

juniper::graphql_object!(impl QueryRoot {
    fn hello(&self) -> &str {
        "world"
    }
});

fn build_schema(enable_introspection: bool) -> impl juniper::MetaObject {
    // Juniper allows specifying introspection via the GraphQLContext configuration.
    struct Context(bool);
    juniper::EmptyMutation::new().into_object().with_field(
        juniper::Field::new(
            "hello",
            vec![],
            juniper::ID, // simplified example
            move |&Context(enabled), &(), &(), _| {
                if enabled {
                    Ok("world")
                } else {
                    Err(juniper::FieldError::new(
                        "Introspection or query blocked",
                        juniper::FieldErrorType::Authentication,
                    ))
                }
            },
        ),
    )
}

#[tokio::main]
async fn main() {
    let introspection_enabled = std::env::var("ENABLE_INTROSPECTION")
        .map(|v| v == "true")
        .unwrap_or(false);

    let schema = build_schema(introspection_enabled);
    let graphql_endpoint = graphql(schema);

    let app = Router::new()
        .route("/graphql", get(graphql_endpoint).post(graphql_endpoint));

    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    axum::Server::bind(&addr)
        .serve(app.into_make_service())
        .await
        .unwrap();
}

These examples illustrate how to align Rust build-time flags and runtime environment variables with introspection settings. By defaulting to disabled and requiring explicit opt-in, you reduce the attack surface while preserving developer ergonomics in trusted contexts. MiddleBrick’s scans will detect reachable introspection and map findings to relevant framework-specific guidance and compliance mappings such as OWASP API Top 10.

Remediation for GraphQL introspection abuse in Axum-based Rust services centers on three controls: schema construction, runtime configuration, and transport-level protections. The primary goal is to ensure introspection is disabled in production unless required for internal tooling, and that its presence does not amplify other vulnerabilities.

First, prefer compile-time or environment-driven schema building. In async-graphql, use .enable_introspection(true) only when a feature flag or environment variable permits it. Avoid leaving introspection enabled by default in library or application code that may be promoted to production without review.

Second, apply route-level guards. Even when introspection is technically enabled, require authentication or authorization before allowing the GraphQL handler to execute. In Axum, this can be achieved with middleware or extractors that validate tokens or session state. The following example shows how to conditionally enable introspection and enforce a simple allowlist check before the handler runs.

// src/main.rs
use axum::{
    async_trait,
    extract::FromRef,
    routing::post,
    Router,
    http::StatusCode,
    response::IntoResponse,
};
use async_graphql::{Schema, EmptySubscription};
use std::sync::Arc;

struct AppState {
    schema: Schema,
    enable_introspection: bool,
    allowed_networks: Vec,
}

#[derive(FromRef)]
struct AuthContext {
    state: Arc,
}

#[async_trait]
impl IntoMakeService for Router {
    type Service = axum::service::ServiceFn _>;
    fn into_make_service(self, _: S) -> Self::Service {
        // Implementation omitted for brevity; in practice, wrap handler with state.
        unimplemented!()
    }
}

async fn graphql_handler(
    AuthContext { state }: AuthContext,
    body: String,
) -> Result {
    if !state.enable_introspection {
        return Err((StatusCode::FORBIDDEN, "GraphQL introspection is disabled".to_string()));
    }
    // Further validation and execution would occur here.
    Ok("(handled)")
}

#[tokio::main]
async fn main() {
    let introspection_enabled = std::env::var("ENABLE_INTROSPECTION")
        .map(|v| v == "true")
        .unwrap_or(false);

    let app_state = Arc::new(AppState {
        schema: build_schema(introspection_enabled),
        enable_introspection: introspection_enabled,
        allowed_networks: vec!["127.0.0.1".parse().unwrap()],
    });

    let app = Router::new()
        .route("/graphql", post(graphql_handler))
        .with_state(app_state);

    let addr = std::net::SocketAddr::from(([127, 0, 0, 1], 3000));
    axum::Server::bind(&addr)
        .serve(app.into_make_service())
        .await
        .unwrap();
}