Auth Bypass in Hanami with Dynamodb

An Auth Bypass in a Hanami application that uses DynamoDB typically arises from authorization logic that is implemented in application code rather than enforced by the data access layer. Hanami encourages explicit, domain-driven boundaries, but if route or action guards are incomplete, an attacker can invoke service objects that directly call DynamoDB operations without re-validating the current user’s rights for the targeted resource.

DynamoDB does not provide native row-level or attribute-level authorization; it enforces only AWS-level authentication (signature/permissions to call the API). Therefore, once an AWS credential with broad table access is embedded in the Hanami runtime, any bypass in Hanami’s authorization gates allows direct, unchecked requests to DynamoDB’s GetItem, Query, or Scan. Common root causes include missing role checks, incorrectly scoped IAM policies that are too permissive, and treating the presence of a user record as implicit read/write access to all items.

Consider an endpoint that loads a profile by ID. If Hanami infers access from the mere existence of a profile record and does not confirm that the requesting user owns that profile, an attacker can enumerate or manipulate IDs to access others’ data. This maps to the BOLA/IDOR category in middleBrick’s 12 checks and aligns with OWASP API Top 10 Broken Object Level Authorization. Even if the Hanami app authenticates users, without per-request ownership validation against DynamoDB request parameters, the API surface remains vulnerable.

In DynamoDB terms, the risk often maps to insufficient condition expressions or missing existence checks on ownership attributes (e.g., user_id). Without these, a crafted request can perform a Query with a global secondary index that returns items outside the caller’s scope. middleBrick’s BOLA/IDOR and Property Authorization checks are designed to surface these gaps by comparing spec definitions with runtime behavior, highlighting endpoints where authorization is implicit rather than enforced.

Additionally, if the Hanami service object reuses a single AWS credential context across calls, a bypass in one endpoint can have lateral impact across multiple resources. This is why runtime testing that cross-references spec definitions with actual DynamoDB request patterns is critical. middleBrick’s OpenAPI/Swagger spec analysis resolves $ref chains and validates that every data operation includes explicit ownership constraints, reducing the chance that a misconfigured route silently exposes DynamoDB operations.

To remediate Auth Bypass when using DynamoDB in Hanami, enforce ownership checks at the service-object level before every DynamoDB operation. Always include the user identifier in key condition expressions or filter expressions, and avoid relying on application-level shortcuts that assume a user can only access their own data.

Example: Safe Query with Ownership Enforcement

Below is a Hanami service class that queries a profiles table, ensuring the requesting user can only access their own items. It uses the AWS SDK for Ruby with explicit key conditions and a placeholder for the caller’s user ID.

require 'aws-sdk-dynamodb'

class ProfileRepository
  def initialize(table_name = 'profiles')
    @dynamodb = Aws::DynamoDB::Client.new
    @table = table_name
  end

  # Fetch a profile only if it belongs to the current user
  def find_by_id_for_user(profile_id, user_id)
    response = @dynamodb.query({
      table_name: @table,
      key_condition_expression: 'pk = :pk AND begins_with(sk, :sk)',
      expression_attribute_values: {
        ':pk' => "USER##{user_id}",
        ':sk' => "PROFILE##{profile_id}"
      },
      consistent_read: true
    })
    items = response.items
    raise 'Not found or unauthorized' if items.empty?
    items.first
  end
end

In this example, the partition key (pk) includes the user ID, so a query without the correct user_id cannot retrieve another user’s profile. This pattern enforces ownership at the database request level, which is the core defense against BOLA/IDOR.

Example: Conditional Write with Ownership Attribute

When updating an item, use a condition expression that verifies the user_id attribute matches the caller. This prevents unauthorized updates even if the item ID is known.

def update_email_for_profile(profile_id, user_id, new_email)
  @dynamodb.update_item({
    table_name: @table,
    key: {
      pk: { s: "USER##{user_id}" },
      sk: { s: "PROFILE##{profile_id}" }
    },
    update_expression: 'SET email = :email',
    condition_expression: 'user_id = :uid',
    expression_attribute_values: {
      ':email': { s: new_email },
      ':uid' => { s: user_id }
    }
  })
rescue Aws::DynamoDB::Errors::ConditionalCheckFailedException
  raise 'Update condition failed — possible race condition or unauthorized attempt'
end

The condition_expression ensures the item’s user_id attribute matches the caller’s ID, providing a second layer of enforcement that complements key design.

Remediation Checklist for Hanami + DynamoDB

• Include the user ID in DynamoDB key attributes (partition key or sort key) to leverage efficient, ownership-based queries.
• Use KeyConditionExpression for reads and ConditionExpression for writes to enforce ownership on every operation.
• Avoid scanning entire tables; prefer indexed queries with explicit key attributes.
• Scope IAM policies to least privilege and align them with Hanami service boundaries, but never rely on IAM alone for row-level security.
• Validate input IDs rigorously in Hanami operations to prevent injection or malformed key errors that could bypass intended constraints.

By integrating these patterns, Hanami applications reduce the attack surface exposed through DynamoDB and align with the principle that authorization must be explicit and verifiable at the point of data access.