Ssrf in Gin with Dynamodb

Server-Side Request Forgery (SSRF) in a Gin application that interacts with Amazon DynamoDB can occur when user-supplied input is used to construct HTTP requests or to form DynamoDB endpoint configurations without proper validation. In this context, the SSRF risk is not inherent to DynamoDB itself, but arises when the application uses attacker-controlled data to influence network destinations, such as when building SDK client configurations or when relaying URLs within DynamoDB item attributes.

Consider a scenario where an API endpoint accepts a URL parameter that specifies a DynamoDB table endpoint or a custom AWS service endpoint. If the Gin handler passes this value directly into an HTTP client or AWS SDK configuration, an attacker can direct internal AWS metadata service requests (e.g., http://169.254.169.254/latest/meta-data/iam/security-credentials/) or reach internal services not exposed to the public internet. Because middleBrick tests unauthenticated attack surfaces, it can detect such endpoints by probing for SSRF indicators like unexpected redirects or metadata responses, even when the scan focuses on API behaviors mapped to DynamoDB interactions.

With DynamoDB, SSRF can also manifest through item attributes that store URLs used later in application logic. For example, if a table includes an attribute webhook_url that the application reads and subsequently uses to make outbound HTTP requests, an attacker who can write a malicious URL into that attribute can leverage the application as a proxy. middleBrick’s checks for SSRF include detecting patterns where external inputs influence outbound calls, and it correlates these runtime behaviors with the API specification to highlight risky endpoints in the context of DynamoDB-driven workflows.

In a Gin-based service, common triggers include using http.Client with a URL derived from request parameters or from DynamoDB item fields without sanitization. Because DynamoDB does not initiate outbound HTTP requests on its own, the vulnerability lies in the application code that combines user input, AWS SDK usage, and network calls. middleBrick’s 12 parallel security checks, including Input Validation and SSRF, are designed to uncover these chains by analyzing the API surface and runtime behaviors without requiring authentication.

To mitigate SSRF in a Gin application using DynamoDB, validate and sanitize all inputs that influence network destinations, and avoid using untrusted data to configure AWS service endpoints or HTTP clients. Use allowlists for protocols and hosts, and prefer environment variables or secure configuration for endpoint overrides. The following examples illustrate secure patterns when working with DynamoDB in Go with Gin.

1. Safe DynamoDB client configuration

Do not allow user input to override the AWS endpoint. Instead, configure the client with a fixed endpoint or use AWS SDK’s standard credential chain.

import (
	"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, error) {
	sess, err := session.NewSession(&aws.Config{
		Region:      aws.String("us-west-2"),
		Endpoint:    aws.String(""), // Leave empty to use AWS default endpoint resolution
		Credentials: credentials.NewSharedCredentials("", "default"),
	})
	if err != nil {
		return nil, err
	}
	return dynamodb.New(sess), nil
}

2. Validate user-supplied URLs before use

If your API accepts a URL that will be stored in DynamoDB or used later, enforce strict validation and avoid using the value in outbound requests without additional controls.

import (
	"net/url"
	"strings"
)

func isValidWebhook(input string) bool {
	parsed, err := url.Parse(input)
	if err != nil {
		return false
	}
	if parsed.Scheme != "https" {
		return false
	}
	// Allowlist specific domains
	allowedHosts := []string{"example.com", "api.example.com"}
	for _, h := range allowedHosts {
		if parsed.Host == h {
			return true
		}
	}
	return false
}

func storeWebhook(c *gin.Context) {
	var req struct {
		WebhookURL string `json:"webhook_url"`
	}
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(400, gin.H{"error": "invalid request"})
		return
	}
	if !isValidWebhook(req.WebhookURL) {
		c.JSON(400, gin.H{"error": "webhook URL not allowed"})
		return
	}
	// Store validated URL in DynamoDB item
	svc := newDynamoDB()
	_, err := svc.PutItem(&dynamodb.PutItemInput{
		TableName: aws.String("Settings"),
		Item: map[string]*dynamodb.AttributeValue{
			"webhook_url": {S: aws.String(req.WebhookURL)},
		},
	})
	if err != nil {
		c.JSON(500, gin.H{"error": "failed to store"})
		return
	}
	c.JSON(200, gin.H{"status": "ok"})
}

3. Avoid using DynamoDB item attributes as direct request targets

If you must use data from DynamoDB to make outbound calls, treat it as untrusted and apply the same validation as any external input.

func processWebhookFromItem(c *gin.Context) {
	item := fetchItemFromDynamoDB(c.Param("id"))
	rawURL, ok := item["callback_url"].(*string)
	if !ok {
		c.JSON(400, gin.H{"error": "missing callback"})
		return
	}
	if !isValidWebhook(*rawURL) {
		c.JSON(400, gin.H{"error": "invalid callback URL"})
		return
	}
	// Proceed with outbound request using validated URL
}

By combining strict input validation, restricted endpoint configuration, and careful handling of data retrieved from DynamoDB, you reduce the attack surface for SSRF. middleBrick’s continuous monitoring and input validation checks can help ensure these practices remain effective across API changes.