Data Exposure in Echo Go with Dynamodb

Data exposure in an Echo Go service that uses DynamoDB typically occurs when responses include sensitive item attributes that should be filtered or redacted before leaving the application. Because DynamoDB is a low-level database, it returns the full item as stored; it does not automatically omit fields like passwords, tokens, or internal metadata. If the handler in Echo Go returns the raw DynamoDB attribute value map without selective projection or transformation, sensitive columns can be included in JSON responses sent to clients.

This becomes likely when the handler unmarshals DynamoDB output into a generic map or structs that mirror the database schema exactly, then serializes that structure back as JSON. For example, an item may contain user_id, email, password_hash, and internal_role. If the handler does not explicitly omit fields such as password_hash and internal_role, the API response exposes credentials and authorization context. In addition, exposure can stem from using inconsistent naming or tag settings between the DynamoDB attribute names and the JSON keys expected by clients, leading to accidental leakage when keys are passed through without aliasing or filtering.

Another vector specific to DynamoDB is the inclusion of metadata fields that AWS uses internally or that developers add for bookkeeping, such as aws:repodriverfields, version attributes, or timestamps that can aid an attacker in reconnaissance. Pagination setups that return full pages of items without trimming sensitive columns compound the issue. Because Echo Go routes are straightforward to wire to DynamoDB via the SDK, developers might skip a dedicated projection layer and inadvertently expose more data than intended. The result is a data exposure finding where sensitive attributes are present in API responses without proper access controls, masking, or field-level filtering.

Remediation focuses on ensuring only intended fields are serialized and returned from Echo Go handlers. Use explicit projection when retrieving items from DynamoDB and construct response objects that contain only necessary fields. Avoid returning the raw DynamoDB attribute map; instead, map to a tailored struct that excludes sensitive keys.

// Example: safe retrieval and response mapping in Echo Go
package main

import (
	"github.com/labstack/echo/v4"
	"github.com/aws/aws-sdk-go-v2/service/dynamodb"
	"github.com/aws/aws-sdk-go-v2/service/dynamodb/types"
)

type UserProfile struct {
	ID    string `json:"id"`
	Email string `json:"email"`
	Name  string `json:"name"`
}

func GetProfile(c echo.Context) error {
	userID := c.Param("id")
	out, err := dynamoClient.GetItem(c.Request().Context(), &dynamodb.GetItemInput{
		TableName: aws.String("Users"),
		Key: map[string]types.AttributeValue{
			"user_id": &types.AttributeValueMemberS{Value: userID},
		},
		// Use ProjectionExpression to limit returned attributes
		ProjectionExpression: aws.String("user_id,email,name"),
	})
	if err != nil {
		return echo.NewHTTPError(http.StatusInternalServerError, "failed to fetch")
	}
	if out.Item == nil {
		return echo.NewHTTPError(http.StatusNotFound, "not found")
	}

	// Map to a safe struct, omitting any sensitive or internal fields
	profile := UserProfile{
		ID:    *out.Item["user_id"].(*types.AttributeValueMemberS).Value,
		Email: *out.Item["email"].(*types.AttributeValueMemberS).Value,
		Name:  *out.Item["name"].(*types.AttributeValueMemberS).Value,
	}
	return c.JSON(http.StatusOK, profile)
}

For scans or queries that return multiple items, apply the same principle: use ProjectionExpression to reduce the data at the source, and map into filtered structs. Do not rely on omitting fields in JSON by using json:"-" tags on structs that are backed by a raw map; instead, construct a new struct or use selective copying. Additionally, enforce IAM policies that restrict the application’s DynamoDB permissions to only the attributes required for each operation, reducing the impact of any accidental exposure at the API layer.