Man In The Middle in Buffalo with Dynamodb

A Man In The Middle (MitM) scenario in a Buffalo application that uses DynamoDB can arise when TLS is not enforced for every endpoint in the request path. If your Buffalo app accepts both HTTP and HTTPS, or if you terminate TLS at a load balancer without enforcing it on the loopback interface between Buffalo and DynamoDB clients, an attacker on the same network can intercept traffic. This includes AWS SDK calls that embed access keys, secret keys, session tokens, or the constructed JSON payload intended for DynamoDB.

DynamoDB itself does not introduce MitM, but the way a Buffalo service talks to it can. For example, if the AWS SDK is configured without a custom HTTP client that forces TLS, or if you use HTTP endpoints for DynamoDB in non-production environments, credentials and data can be exposed. In Buffalo, this often surfaces during local development when the app uses an HTTP proxy or when environment variables override the default AWS SDK endpoint to a non-HTTPS URL. Sensitive data can then be read or altered in transit before reaching DynamoDB.

Consider a Buffalo handler that retrieves a user profile directly from DynamoDB without validating server identity or enforcing strict transport security:

app.Get("/profiles/:id", func(c buffalo.Context) error {
    svc := dynamodb.New(session.Must(session.NewSession()))
    input := &dynamodb.GetItemInput{
        TableName: aws.String("Profiles"),
        Key: map[string]*dynamodb.AttributeValue{
            "user_id": {S: aws.String(c.Param("id"))},
        },
    }
    result, err := svc.GetItem(input)
    if err != nil {
        return c.Error(500, err)
    }
    return c.Render(200, r.JSON(result.Item))
})

If the AWS SDK resolves the DynamoDB endpoint over HTTP, the access credentials and the user_id used as a key can be intercepted. An attacker could then map valid user IDs and observe responses, leading to unauthorized data access. This becomes especially critical when the Buffalo app is deployed in environments where network segmentation is weak or where development configurations accidentally carry over to staging or production.

Another vector is insecure service discovery or misconfigured VPC endpoints that redirect DynamoDB traffic through a malicious node. Because Buffalo does not inherently validate the TLS certificate chain for AWS endpoints beyond what the underlying HTTP client provides, developers must ensure that the SDK is configured to use HTTPS and that certificate verification is not disabled.

To prevent MitM when Buffalo interacts with DynamoDB, enforce HTTPS programmatically and avoid any configuration that allows plaintext HTTP. This means customizing the AWS SDK HTTP client in Buffalo to require TLS and to verify server certificates. You should also avoid overriding endpoints with non-HTTPS URLs unless absolutely necessary and fully secured.

Use a custom HTTP client that enforces TLS and disables insecure skip verify. In Buffalo, you can build the DynamoDB client once during application initialization and inject it where needed:

import (
    "crypto/tls"
    "net/http"
    "github.com/aws/aws-sdk-go/aws"
    "github.com/aws/aws-sdk-go/aws/session"
    "github.com/aws/aws-sdk-go/service/dynamodb"
)

func NewDynamoDBClient() *dynamodb.DynamoDB {
    // Force TLS and enforce certificate validation
    httpClient := &http.Client{
        Transport: &http.Transport{
            TLSClientConfig: &tls.Config{
                InsecureSkipVerify: false,
            },
        },
    }

    sess := session.Must(session.NewSession(&aws.Config{
        HTTPClient: httpClient,
        // Ensure the SDK uses HTTPS endpoints
        Endpoint:       aws.String("https://dynamodb.us-east-1.amazonaws.com"),
        Region:         aws.String("us-east-1"),
        DisableSSL:     aws.Bool(false),
        S3ForcePathStyle: aws.Bool(false),
    }))

    return dynamodb.New(sess)
}

Then in your Buffalo handlers, use this client instead of creating a new session each time:

var dbClient = NewDynamoDBClient()

app.Get("/profiles/:id", func(c buffalo.Context) error {
    input := &dynamodb.GetItemInput{
        TableName: aws.String("Profiles"),
        Key: map[string]*dynamodb.AttributeValue{
            "user_id": {S: aws.String(c.Param("id"))},
        },
    }
    result, err := dbClient.GetItem(input)
    if err != nil {
        return c.Error(500, err)
    }
    return c.Render(200, r.JSON(result.Item))
})

Additionally, in production, ensure that your AWS SDK environment variables (e.g., AWS_EC2_METADATA_SERVICE_ENDPOINT) do not redirect SDK behavior to insecure endpoints. In Buffalo, you can also integrate middleware that validates outbound requests if you are using an HTTP client that inspects requests, but the primary defense is to configure the DynamoDB client to disable SSL only for local testing and to always use verified certificates in staging and production.

For local development, you may use a local DynamoDB mock with HTTP, but ensure that this is never enabled in builds that handle real data. The Pro plan of middleBrick can support continuous monitoring for such misconfigurations by scanning your API surface and flagging endpoints that do not enforce encryption, helping you catch risky patterns before they reach production.