Auth Bypass in Echo Go with Dynamodb

An Auth Bypass in an Echo Go service that uses DynamoDB typically occurs when authorization checks are missing, incomplete, or incorrectly applied before DynamoDB operations. Because Echo routes HTTP requests to handlers and DynamoDB is often used as a persistence layer, gaps between authentication and data access create conditions where an authenticated identity can operate outside intended permissions.

For example, an endpoint like /users/{userID}/profile may validate that a JWT is present but fail to ensure the requesting user can only access their own userID. If the handler builds a DynamoDB query using a raw path parameter without verifying ownership, an attacker can modify the userID to access or modify another user’s data. This is a Broken Object Level Authorization (BOLA) pattern, commonly described in the OWASP API Top 10 as IDOR when object references are predictable.

DynamoDB itself does not enforce application-level permissions; it enforces identity-based IAM policies at the AWS account level. If the Go service uses a shared credential or an over-permissive IAM role, any compromised or malicious request that reaches the service can perform broad operations such as GetItem, UpdateItem, or Scan. Without explicit per-request ownership checks in Go code and without scoped credentials (for example via temporary credentials scoped to user ID), the risk of Auth Bypass is elevated.

Real-world attack patterns include changing numeric or UUID identifiers in query parameters, manipulating URL paths, or injecting unexpected headers to trigger different routing behavior in Echo. Since DynamoDB queries in Go are constructed programmatically, missing validation or incorrect key construction leads to unintended access. The service appears to enforce authentication, but the authorization boundary is porous because the handler does not re-validate scope against the data model before issuing DynamoDB operations.

middleBrick detects this category through unauthenticated and authenticated-style scans that test IDOR and BOLA checks across endpoints, comparing spec definitions to runtime behavior. It flags missing ownership enforcement and highlights risks such as sensitive data exposure or unauthorized updates. Findings align with frameworks like OWASP API Top 10 and can be tracked over time using the Dashboard or Pro plan continuous monitoring.

Remediation centers on enforcing ownership and scope checks in Go before any DynamoDB request, and ensuring that IAM policies follow least privilege. Below are concrete, working examples using the AWS SDK for Go v2.

1. Validate ownership before querying DynamoDB

Always extract the identity of the requester (from JWT or session) and use it to constrain the key condition. Never trust path parameters alone.

// Assuming you have parsed claims into a struct with a UserID field
type Claims struct {
    UserID string `json:"sub"`
}

func getUserProfile(c echo.Context) error {
    // Extract authenticated user identity
    claims := c.Get("claims").(*Claims)
    requestedUserID := c.Param("userID")

    // Enforce ownership: do not proceed if IDs differ
    if claims.UserID != requestedUserID {
        return c.JSON(http.StatusForbidden, map[string]string{"error": "access denied"})
    }

    // Build DynamoDB query using the verified identity
    out, err := svc.GetItem(c.Context(), &dynamodb.GetItemInput{
        TableName: aws.String("Users"),
        Key: map[string]types.AttributeValue{
            "PK": &types.AttributeValueMemberS{Value: "USER#" + claims.UserID},
        },
    })
    if err != nil {
        return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
    }
    if out.Item == nil {
        return c.JSON(http.StatusNotFound, map[string]string{"error": "not found"})
    }
    // marshal out.Item into your response DTO
    return c.JSON(http.StatusOK, out.Item)
}

2. Apply least-privilege IAM via SDK configuration

Configure the DynamoDB client with credentials that restrict operations by partition key where possible, and avoid broad permissions in production.

// Example of creating a client with restricted credentials
// In practice, use IAM roles or scoped credentials instead of hardcoded values
cfg, err := config.LoadDefaultConfig(context.TODO(),
    config.WithRegion("us-east-1"),
)
if err != nil {
    log.Fatalf("unable to load SDK config, %v", err)
}

// Use condition keys in your policies to constrain access by user attribute
svc := dynamodb.NewFromConfig(cfg, func(o *dynamodb.Options) {
    // Customizations such as retry options can go here
})

3. Use expression attribute values to avoid injection and enforce filters

When querying or scanning, prefer key conditions and filter expressions that incorporate the authenticated user ID, avoiding string concatenation that could be abused.

params := &dynamodb.QueryInput{
    TableName:              aws.String("Messages"),
    KeyConditionExpression: aws.String("PK = :pk AND begins_with(SK, :sk)"),
    ExpressionAttributeValues: map[string]types.AttributeValue{
        ":pk": &types.AttributeValueMemberS{Value: "USER#" + claims.UserID},
        ":sk": &types.AttributeValueMemberS{Value: "MSG#"},
    },
}
resp, err := svc.Query(c.Context(), params)
if err != nil {
    return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
}

4. Avoid Scan; prefer Query with owner key

Scanning entire tables is risky and expensive. Ensure your data model allows key-based retrieval so you never need to scan across all items for a user-specific query.

5. Middleware enforcement in Echo

Use Echo middleware to centralize ownership validation so handlers remain clean and consistent.

func AuthMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
    return func(c echo.Context) error {
        claims := c.Get("claims").(*Claims)
        requestedID := c.Param("userID")
        if claims.UserID != requestedID {
            return c.JSON(http.StatusForbidden, map[string]string{"error": "forbidden"})
        }
        return next(c)
    }
}

// Register routes
echo.GET("/users/:userID/profile", getUserProfile, AuthMiddleware)

By combining strict per-request ownership checks in Go with least-privilege IAM policies, you significantly reduce the likelihood of Auth Bypass when using Echo and DynamoDB. Regular scans with tools like middleBrick can help verify that these controls are present at runtime.