Missing Authentication in Fiber with Dynamodb

Missing Authentication in a Fiber application that uses DynamoDB can expose data and operations to unauthorized users. When routes are not protected and the application directly maps user-supplied identifiers to DynamoDB requests, attackers can manipulate parameters to access or modify data belonging to other users.

In this scenario, an endpoint such as /users/:userID may retrieve a user profile from a DynamoDB table without verifying that the authenticated caller owns the requested userID. Because the request is unauthenticated, there is no identity context to enforce ownership. An attacker can iterate over numeric or predictable IDs and read any record stored in the table, leading to mass information disclosure. This pattern is commonly categorized under BOLA (Broken Object Level Authorization) and IDOR (Insecure Direct Object Reference).

DynamoDB-specific risks arise from how queries and scans are constructed. If the application builds a GetItem or Query using a user ID from the request without validating scope, the service will return the requested item if the primary key matches. Unlike relational databases, DynamoDB does not perform authorization; it only enforces permissions attached to the credentials used by the backend. If those credentials have broad read access, any valid primary key can be retrieved, and there are no native row-level guards to prevent it.

Consider a vulnerable Fiber handler that retrieves a user profile by ID:

app.Get("/users/:userID", func(c *fiber.Ctx) error {
    userID := c.Params("userID")
    params := &dynamodb.GetItemInput{
        TableName: aws.String("Users"),
        Key: map[string]types.AttributeValue{
            "PK": &types.AttributeValueMemberS{Value: "USER#" + userID},
        },
    }
    out, err := svc.GetItem(context.TODO(), params)
    if err != nil {
        return c.Status(fiber.StatusInternalServerError).SendString(err.Error())
    }
    if out.Item == nil {
        return c.SendStatus(fiber.StatusNotFound)
    }
    return c.JSON(out.Item)
})

In this example, there is no check that the caller is allowed to access the requested userID. The middleware stack does not enforce authentication, and the DynamoDB call trusts the client-supplied identifier. An attacker can use tools like curl or a REST client to iterate over IDs such as USER#1001, USER#1002, and so on, retrieving sensitive profile data, email addresses, or other personal information stored in the table.

LLM/AI Security checks provided by middleBrick can detect whether endpoints handling DynamoDB resources expose unauthenticated data access patterns. These scans test for missing authentication controls and highlight findings that align with OWASP API Top 10 A01:2023 — Broken Object Level Authorization, helping teams identify gaps before attackers do.

Remediation focuses on ensuring that every request to DynamoDB is scoped to the authenticated caller and that missing authentication is treated as an error. You should enforce authentication before processing requests and bind the authenticated identity to the DynamoDB key, rather than relying on client-supplied identifiers.

Use middleware to validate credentials and extract a subject or tenant context, then construct DynamoDB keys that include this trusted identity. For example, after confirming a valid session or token, derive the primary key from the authenticated subject instead of the URL parameter.

Here is a revised version of the previous handler that incorporates authentication and proper key scoping:

app.Get("/users/me", func(c *fiber.Ctx) error {
    // Assume an authenticated user context set by prior middleware
    userSubject := c.Locals("auth_subject").(string) // e.g., "alice@example.com"
    if userSubject == "" {
        return c.SendStatus(fiber.StatusUnauthorized)
    }
    pk := &types.AttributeValueMemberS{Value: "USER#" + userSubject}
    params := &dynamodb.GetItemInput{
        TableName: aws.String("Users"),
        Key: map[string]types.AttributeValue{
            "PK": pk,
        },
    }
    out, err := svc.GetItem(context.TODO(), params)
    if err != nil {
        return c.Status(fiber.StatusInternalServerError).SendString(err.Error())
    }
    if out.Item == nil {
        return c.SendStatus(fiber.StatusNotFound)
    }
    return c.JSON(out.Item)
})

This pattern removes the userID parameter from the route and derives the DynamoDB key from authenticated context. It prevents horizontal privilege escalation because users can only retrieve their own record, and there is no direct object ID supplied by the client.

For broader queries, such as listing user-specific items, apply the same scoping to the partition key and, where applicable, the sort key. For example:

params := &dynamodb.QueryInput{
    TableName: aws.String("UserData"),
    KeyConditionExpression: aws.String("PK = :pk"),
    ExpressionAttributeValues: map[string]types.AttributeValue{
        ":pk": &types.AttributeValueMemberS{Value: "USER#" + userSubject},
    },
}

By binding the partition key to the authenticated subject, you ensure that a compromised request cannot pivot to another user’s data. middleBrick’s Pro plan supports continuous monitoring for misconfigurations like missing authentication on DynamoDB endpoints, and the GitHub Action can fail builds when such patterns are detected in OpenAPI specs or runtime scans.

In summary, address Missing Authentication in Fiber with DynamoDB by enforcing authentication, removing direct client-controlled identifiers from data access, and constructing DynamoDB keys from trusted identity context. This combination reduces the risk of IDOR and BOLA attacks against your table and aligns findings with remediation guidance available in security reports and compliance mappings.