Container Escape in Fiber with Dynamodb

A container escape in a Fiber service that uses DynamoDB typically arises when the application processes untrusted input and uses it to construct system commands, file paths, or environment variables that ultimately affect the container runtime. For example, if an endpoint accepts a user-controlled value and passes it to an OS command used to interact with DynamoDB (such as a custom wrapper or a debug script), an attacker may inject shell metacharacters to execute arbitrary processes inside the container. Because the container shares the host kernel, a successful escape can lead to host-level access, affecting not only the DynamoDB data plane but also other services running on the same node.

Consider a scenario where a Fiber route builds an AWS CLI command string to query DynamoDB based on user input without proper sanitization:

app.Get('/user/:table', func(c *fiber.Ctx) error {
	table := c.Params('table')
	cmd := exec.Command("aws", "dynamodb", "get-item", "--table-name", table, "--key", fmt.Sprintf(`{\"id\": {\"S\": \"%s\"}}`, c.Query("id")))
	out, _ := cmd.Output()
	return c.SendString(string(out))
})

If the table parameter is not validated, an attacker could supply a value such as users; cat /etc/passwd, leading to command injection and potential host access. Even when the DynamoDB client itself is used directly via an SDK, improper handling of configuration sources (e.g., reading endpoint URLs or credentials from environment variables that can be influenced by an attacker) can redirect SDK behavior to unintended hosts, effectively moving laterally within the container network or accessing credentials mounted for other containers.

The risk is compounded when the container runs with elevated privileges or mounts sensitive host paths. An attacker who achieves execution inside the container may attempt to read mounted AWS credentials, exploit shared namespaces, or access the DynamoDB endpoint via the container’s internal networking. This combination of a web framework with flexible routing, dynamic SDK configuration, and containerized deployment creates a chain where input handling flaws translate into host-level compromise.

To mitigate container escape risks specific to Fiber applications using DynamoDB, enforce strict input validation, avoid constructing shell commands, and use the AWS SDK for Go with explicit configuration instead of dynamic command assembly. The following example demonstrates a secure approach:

app.Get('/user/:table', func(c *fiber.Ctx) error {
	table := c.Params('table')
	// Validate table name against a strict allowlist
	validTables := map[string]bool{"users": true, "orders": true, "products": true}
	if !validTables[table] {
		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{"error": "invalid table name"})
	}
	// Use the SDK directly with explicit configuration
	sess := session.Must(session.NewSession(&aws.Config{
		Region:      aws.String("us-east-1"),
		Endpoint:    aws.String("https://dynamodb.us-east-1.amazonaws.com"),
		Credentials: credentials.NewStaticCredentials("AKI...", "secret...", ""), // Use IAM roles in production
	}))
	svc := dynamodb.New(sess)
	result, err := svc.GetItem(&dynamodb.GetItemInput{
		TableName: aws.String(table),
		Key: map[string]*dynamodb.AttributeValue{
			"id": {
				S: aws.String(c.Query("id")),
			},
		},
	})
	if err != nil {
		return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{"error": err.Error()})
	}
	return c.JSON(result)
})

Key remediation practices include:

Never concatenate user input into shell commands; use the SDK directly.
Validate table and parameter values against a strict allowlist rather than a blocklist.
Ensure container images run as non-root users and avoid mounting sensitive host paths.
Use IAM roles for service accounts instead of embedding credentials in environment variables that could be manipulated via injection.
Apply network policies to restrict the container’s ability to reach unexpected endpoints, reducing the impact of a potential escape.

These steps reduce the likelihood that input handling flaws in Fiber routes can influence the container runtime or DynamoDB interactions in unintended ways.