Broken Authentication in Actix with Dynamodb

When building an Actix-web service that uses Amazon DynamoDB as the user store, broken authentication typically arises from a mismatch between session management in Actix and how credentials or tokens are validated against DynamoDB. If the application stores only a user identifier in a client-side cookie or JWT, and retrieves sensitive account data from DynamoDB on each request without re-verifying a server-side session or cryptographic proof, an attacker can manipulate the identifier to assume another user’s identity.

DynamoDB itself does not cause authentication broken, but its role as the source of truth can amplify risk when access patterns do not enforce ownership checks. For example, an endpoint like /api/users/{user_id} might accept a path parameter, query DynamoDB for that user_id, and return profile information. If the API does not ensure that the authenticated principal matches the requested user_id, an unauthenticated or low-privilege actor can enumerate or modify other users’ data by changing the identifier.

This situation is common when JWTs or session tokens lack a binding to a server-side context or when the token payload includes the user identifier but the server does not verify that the requester’s credentials align with the item being fetched from DynamoDB. Attack patterns such as IDOR (Insecure Direct Object References) or BOLA (Broken Object Level Authorization) map directly onto this design: the API trusts client-supplied identifiers and uses them as primary keys in DynamoDB without an additional authorization layer. Because DynamoDB supports fine-grained access control via IAM policies, misconfigured policies that grant broad read access to user tables can further enable horizontal privilege escalation across accounts.

The use of unauthenticated or improperly authenticated endpoints in Actix exacerbates the issue. If health checks or public routes accidentally expose user lookup functionality without verifying a session or token, an attacker can probe for valid user IDs and harvest PII stored in DynamoDB. MiddleBrick’s LLM/AI Security checks highlight system prompt leakage and unauthorized LLM endpoint usage, but in this context, the concern is that poorly guarded authentication paths can leak DynamoDB-stored data through indirect channels.

Real-world parallels include findings mapped to OWASP API Top 10 2023:1 — Broken Object Level Authorization, where API identifiers are trusted without verifying the requesting user’s right to access that object. PCI-DSS and SOC2 controls also require strict session validation and data segregation, which are undermined when DynamoDB queries rely solely on client-supplied keys without server-side ownership verification.

To fix authentication issues when using Actix with DynamoDB, enforce server-side session validation and ensure every DynamoDB request includes explicit ownership checks. Avoid trusting path parameters or JWT subject claims alone; instead, bind the authenticated principal to the DynamoDB request using IAM conditions or application-level filters.

Example: Secure user profile retrieval

Assume a DynamoDB table users with a primary key user_id. The authenticated identity is stored in Actix request extensions after a verified login. The handler should retrieve the authenticated user ID from the session, then fetch exactly that item from DynamoDB rather than using a user-provided ID.

use actix_web::{web, HttpResponse, Result};
use aws_sdk_dynamodb::Client;
use serde::{Deserialize, Serialize};

#[derive(Debug, Serialize, Deserialize)]
struct User {
    user_id: String,
    email: String,
    // other fields
}

async fn get_profile(
    session: actix_session::Session,
    client: web::Data,
) -> Result<HttpResponse> {
    // 1) Obtain authenticated identity from server-side session
    let authenticated_user_id = session.get::

async fn update_settings(
    client: web::Data<Client>,
    user_id: web::Path<String>,
    settings: web::Json<Settings>,
    session: actix_session::Session,
) -> Result<HttpResponse> {
    let authenticated_user_id = session.get::