Missing Authentication in Axum with Dynamodb

When an Axum service exposes DynamoDB-backed endpoints without enforcing authentication, it creates a direct path for attackers to interact with your database using unauthenticated HTTP requests. Axum, a Rust web framework, does not inherently provide authentication; it relies on developer middleware to enforce access controls. If routes that forward requests to DynamoDB skip auth checks, the API surface becomes vulnerable.

Consider an endpoint like /users/{user_id} that queries DynamoDB using the user_id from the path. Without authentication, any caller can supply any user_id and retrieve or attempt to modify records. Because DynamoDB permissions are typically managed via IAM policies attached to credentials, missing application-layer authentication means requests reach DynamoDB without a verified identity. In a black-box scan, middleBrick tests this by sending requests without credentials and checking whether data is returned or actions are allowed, uncovering BOLA/IDOR risks tied to weak or missing ownership checks.

In a typical integration, an Axum handler might use the AWS SDK for Rust to call DynamoDB. If the SDK client is configured with broad IAM permissions (for example, to allow read/write on a table), and the handler does not validate the requester’s identity or authorization, the endpoint effectively becomes public. Attackers can probe numeric or UUID identifiers, enumerate records, and potentially exploit Insecure Direct Object References (IDOR). The scanner runs parallel checks for Authentication and BOLA/IDOR, mapping findings to OWASP API Top 10 A01:2019 and relevant compliance frameworks.

Real-world impact becomes clearer when DynamoDB streams or secondary indexes are involved: an unauthenticated handler might inadvertently expose sensitive attributes (email, role, PII) due to missing field-level authorization. middleBrick’s property authorization checks look for whether response filters or row-level conditions are applied; without them, data exposure risks increase. Because Axum leaves routing and middleware composition to the developer, missing authentication is a common root cause that enables BOLA, privilege escalation, and data exposure in DynamoDB-integrated services.

Remediation centers on enforcing authentication and fine-grained authorization before any DynamoDB interaction, and validating ownership or scope of the requested resource. Below are concrete Axum examples that integrate authentication and apply DynamoDB-specific guards.

1. Require authentication before routing

Use an extractor that validates a bearer token or session, and reject requests without valid credentials before they reach DynamoDB. For example, using tower-http for JWT validation:

use axum::{
    async_trait,
    extract::FromRequest,
    http::{Request, StatusCode},
};
use jsonwebtoken::{decode, Algorithm, DecodingKey, Validation};

pub async fn auth_handler(
    token: JwtToken,
    user_id: axum::extract::Path,
    dynamodb_client: aws_sdk_dynamodb::Client,
) -> Result<impl axum::response::IntoResponse, (StatusCode, String)> {
    // token validated by JwtToken extractor
    let user_id = user_id.into_inner();
    // Ensure the token subject matches the requested user_id to prevent BOLA
    if token.claims.sub != user_id {
        return Err((StatusCode::FORBIDDEN, "Unauthorized resource access".into()));
    }
    // Safe DynamoDB call with scoped permissions
    let item = dynamodb_client
        .get_item()
        .table_name("users")
        .key("user_id", aws_sdk_dynamodb::types::AttributeValue::S(user_id))
        .send()
        .await
        .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
    // handle item
    Ok(item)
}

#[derive(Debug, jsonwebtoken::DecodeToken)]
struct Claims {
    sub: String,
    // other claims
}

struct JwtToken(Claims);

#[async_trait]
impl FromRequest<S> for JwtToken {
    type Rejection = (StatusCode, String);
    async fn from_request(req: Request, _state: &S) -> Result {
        let auth = req.headers().get("Authorization").and_then(|v| v.to_str().ok()).ok_or((StatusCode::UNAUTHORIZED, "Missing header".into()))?;
        let token = auth.strip_prefix("Bearer ").ok_or((StatusCode::UNAUTHORIZED, "Invalid auth scheme".into()))?;
        let data = decode::(
            token,
            &DecodingKey::from_secret("secret".as_ref()),
            &Validation::new(Algorithm::HS256),
        ).map_err(|_| (StatusCode::UNAUTHORIZED, "Invalid token".into()))?;
        Ok(JwtToken(data.claims))
    }
}

2. Apply DynamoDB condition expressions for ownership

Even after authentication, use condition expressions to ensure that operations only affect items belonging to the requester. This reduces impact of misconfigured IAM policies:

use aws_sdk_dynamodb::types::AttributeValue;

async fn update_user_email(
    client: &aws_sdk_dynamodb::Client,
    user_id: String,
    email: String,
    caller_sub: String,
) -> Result<(), aws_sdk_dynamodb::Error> {
    client
        .update_item()
        .table_name("users")
        .key("user_id", AttributeValue::S(user_id))
        .update_expression("SET email = :e")
        .condition_expression("user_id = :uid AND sub = :sub")
        .expression_attribute_values(":e", AttributeValue::S(email))
        .expression_attribute_values(":uid", AttributeValue::S(user_id))
        .expression_attribute_values(":sub", AttributeValue::S(caller_sub))
        .send()
        .await?;
    Ok(())
}

3. Enforce field-level filtering on read paths

When returning DynamoDB items, filter sensitive fields unless required. Combine with attribute-level checks in your handler logic:

async fn get_user_profile(
    client: &aws_sdk_dynamodb::Client,
    user_id: String,
    caller_sub: String,
) -> Result<serde_json::Value, aws_sdk_dynamodb::Error> {
    let output = client
        .get_item()
        .table_name("users")
        .key("user_id", AttributeValue::S(user_id.clone()))
        .send()
        .await?;
    let item = output.item.ok_or_else(|| aws_sdk_dynamodb::error::SdkError::service_error(
        aws_sdk_dynamodb::error::ServiceError::new(
            "Item not found",
            aws_smithy_http::result::SdkError::construction_failure(Box::new(std::io::Error::new(std::io::ErrorKind::Other, "not found"))),
        ),
    ))?;
    // Ensure ownership
    if item.get("sub").and_then(|v| v.as_s().ok()) != Some(caller_sub.as_str()) {
        return Err(aws_sdk_dynamodb::error::SdkError::service_error(
            aws_sdk_dynamodb::error::ServiceError::new(
                "Forbidden",
                aws_smithy_http::result::SdkError::construction_failure(Box::new(std::io::Error::new(std::io::ErrorKind::Other, "forbidden"))),
            ),
        ));
    }
    // Return only safe fields
    let safe = serde_json::json!({
        "user_id": item.get("user_id").and_then(|v| v.as_s().ok()),
        "email": item.get("email").and_then(|v| v.as_s().ok()),
    });
    Ok(safe)
}

4. Use least-privilege IAM for the DynamoDB client

Configure the AWS SDK client in Axum with credentials scoped to the minimal required actions (e.g., dynamodb:GetItem for read-only endpoints) and scope down to table-level or conditionally with attributes. Avoid wide permissions in production environments.

By combining route-level authentication, ownership checks in condition expressions, and least-privilege IAM, you mitigate the risk of unauthenticated access to DynamoDB through Axum handlers. middleBrick can validate these controls by testing unauthenticated access and property authorization, ensuring your scans stay within the 5–15 seconds range while providing prioritized remediation guidance.