Identification Failures in Axum

Identification failures in Axum applications occur when the framework fails to properly verify the identity of users or services before granting access to resources. In Axum's async/await architecture, these failures often manifest through improper middleware chaining, missing authorization checks, or inadequate request context propagation.

A common vulnerability pattern emerges when developers rely solely on Axum's built-in TypedHeader extraction without validating the authenticity of authentication tokens. Consider an endpoint that extracts a JWT from the Authorization header:

async fn protected_endpoint(
    TypedHeader(Authorization(JwtToken(token))): TypedHeader<Authorization<JwtToken>>
) -> Result<impl Reply> {
    // Missing token validation!
    Ok("Authenticated response")
}

This code extracts the token but never validates its signature, expiration, or claims. An attacker can craft any token and gain access.

Another Axum-specific manifestation occurs with improper middleware ordering. Axum processes extractors and middleware sequentially, so placing authorization middleware after business logic creates timing windows:

async fn business_logic(extractors) -> Result<impl Reply> {
    // Business logic executes first
    Ok("Data processed")
}

async fn check_auth(extractors) -> Result<impl Reply> {
    // Authorization runs AFTER business logic
    Ok("Authorized")
}

The correct pattern requires authorization to wrap business logic:

async fn protected_endpoint(extractors) -> Result<impl Reply> {
    // Authorization runs BEFORE business logic
    Ok("Authorized and processing")
}

Identification failures also appear in Axum's state management. When using State<T> for shared resources, improper initialization can lead to predictable identifiers:

let state = State::new(PredictableCounter::new(0)); // Predictable initial state
app.route("/counter", get(counter_handler).with_state(state));

An attacker can exploit this predictability to guess resource identifiers or session tokens.

Service identification failures occur when Axum applications accept requests from any origin without validating service identity:

async fn open_service_endpoint(extractors) -> Result<impl Reply> {
 // No service identity verification
    Ok("Service data")
}

This allows any service to impersonate legitimate clients, leading to data exposure or unauthorized operations.

Detecting identification failures in Axum requires both static code analysis and runtime scanning. middleBrick's black-box scanning approach is particularly effective for Axum applications since it tests the actual HTTP endpoints without requiring source code access.

middleBrick scans Axum APIs for identification failures by testing unauthenticated endpoints, attempting parameter manipulation, and verifying proper authentication enforcement. The scanner sends requests with various authentication headers, including malformed tokens, expired credentials, and missing authentication to identify endpoints that should be protected but aren't.

For OpenAPI spec analysis, middleBrick resolves Axum's #[derive(Extract)] patterns and #[handler] attributes to understand the intended authentication requirements, then compares these specifications against actual runtime behavior. This cross-referencing identifies endpoints where the specification claims authentication is required but the implementation allows unauthenticated access.

#[get("/api/users/{id}")]
async fn get_user(State<AppState> state, Path<UserId> id) -> Result<Json<User>> {
    // Missing authentication check
    let user = state.db.get_user(id).await?;
    Ok(Json(user))
}

middleBrick would flag this endpoint as vulnerable because it allows IDOR (Insecure Direct Object Reference) attacks—any user can access any other user's data by manipulating the ID parameter.

The scanner also tests for Axum's common middleware bypass patterns. Since Axum processes extractors in declaration order, middleBrick attempts to craft requests that exploit this ordering:

#[get("/api/data")]
async fn data_endpoint(extractors) -> Result<impl Reply> {
    // Business logic first, auth later
    Ok("Sensitive data")
}

middleBrick's LLM/AI security checks are particularly relevant for Axum applications using AI features. The scanner tests for system prompt leakage and prompt injection vulnerabilities that could allow attackers to extract sensitive identification information from AI-powered endpoints.

middleBrick's inventory management check identifies all API endpoints, including those that may have been accidentally exposed through Axum's modular routing system. This comprehensive inventory helps security teams understand their complete attack surface.

Remediating identification failures in Axum requires implementing proper authentication and authorization patterns using Axum's native features. The most effective approach is to use Axum's middleware system to enforce authentication before any business logic executes.

First, implement a centralized authentication middleware:

use axum::middleware::Next;
use axum::extract::{Request, Extension};
use axum::http::StatusCode;
use jsonwebtoken::{decode, Validation};

async fn auth_middleware(
    mut req: Request<B>,
    next: Next<"middlebrick">,
) -> Result<impl Reply, (StatusCode, &'static str)> {
    let auth_header = match req.headers().get("Authorization") {
        Some(header) => header,
        None => return Err((StatusCode::UNAUTHORIZED, "Missing token")),
    };

    let token = auth_header.to_str().map_err(|_| (StatusCode::BAD_REQUEST, "Invalid header"))?;
    let token = token.strip_prefix("Bearer ").ok_or((StatusCode::BAD_REQUEST, "Invalid format"))?;

    let decoded = decode::
        Claims,
        _,
        &[u8],
        Validation,
    >(token, &SECRET_KEY, &Validation::new(Algorithm::HS256))
    .map_err(|_| (StatusCode::UNAUTHORIZED, "Invalid token"))?;

    // Attach user info to request context
    req.extensions_mut().insert(decoded.claims);

    let res = next.run(req).await;
    Ok(res)
}

#[derive(Debug, serde::Deserialize)]
struct Claims {
    sub: String,
    role: String,
    exp: usize,
}

Apply this middleware to routes that require authentication:

let app = Router::new()
    .route("/public", get(public_handler))
    .route("/protected", get(protected_handler).layer(Extension(auth_middleware)));

For role-based access control in Axum, use the Extension extractor to access authenticated user information:

async fn admin_only_endpoint(
    Extension(user): Extension<Claims>,
) -> Result<impl Reply> {
    if user.role != "admin" {
        return Err((StatusCode::FORBIDDEN, "Insufficient privileges"));
    }
    Ok("Admin data")
}

Implement proper state management to avoid predictable identifiers:

use rand::Rng;

struct SecureState {
    counter: u64,
    secret: [u8; 32],
}

impl SecureState {
    fn new() -> Self {
        let mut rng = rand::thread_rng();
        let secret = rng.gen::
            [u8; 32],
        >();
        Self { counter: 0, secret }
    }
}

For service identification, implement mutual TLS or API key validation:

async fn service_endpoint(
    TypedHeader(ApiKey(key)): TypedHeader<ApiKey>,
) -> Result<impl Reply> {
    if !validate_service_key(&key) {
        return Err((StatusCode::UNAUTHORIZED, "Invalid service key"));
    }
    Ok("Service data")
}

Finally, use Axum's error handling to provide consistent authentication failure responses:

use axum::response::IntoResponse;
use axum::http::StatusCode;

#[derive(Debug)]
enum AuthError {
    MissingToken,
    InvalidToken,
    InsufficientPermissions,
}

impl IntoResponse for AuthError {
    fn into_response(self) -> axum::response::Response {
        let (status, message) = match self {
            AuthError::MissingToken => (StatusCode::UNAUTHORIZED, "Missing authentication token"),
            AuthError::InvalidToken => (StatusCode::UNAUTHORIZED, "Invalid authentication token"),
            AuthError::InsufficientPermissions => (StatusCode::FORBIDDEN, "Insufficient permissions"),
        };
        (status, message).into_response()
    }
}

These patterns ensure that Axum applications properly identify and authenticate all requests before processing sensitive operations.