Api Key Exposure in Echo Go with Mongodb

When an Echo Go service stores and uses MongoDB connection strings or API keys, several patterns common in Go web services can unintentionally expose those credentials. The risk typically arises when environment variables or configuration values are passed into MongoDB client options without proper sanitization or are included in logs, error messages, and HTTP responses.

In Echo Go, developers often initialize the MongoDB client in main.go or an init function by reading configuration from the environment. If the connection string contains the API key and that string is later used to construct client options or is echoed for debugging, the key can leak through logs, panic traces, or verbose error pages served to API consumers.

Consider an endpoint that accepts a request ID and returns internal processing details. If the handler retrieves a MongoDB collection and performs an operation that fails, a poorly written error handler might include the full MongoDB URI from the client object in the HTTP response body or server logs. Because the scan tests unauthenticated attack surfaces, an endpoint that returns stack traces or configuration snippets can reveal the API key to anyone who triggers the error path.

Additionally, when using the MongoDB Go driver, developers sometimes pass context derived from request headers directly into operations like Collection.Find. If the request includes sensitive metadata that is forwarded into logging or monitoring without redaction, and the logging configuration accidentally prints the MongoDB client’s connection details, the API key becomes part of the observable output. This is especially risky when the Echo Go service is deployed in environments where log aggregation tools have broader access than intended.

Another common exposure vector is reflection-based configuration loading. If the Echo Go application uses a library that maps environment variables to struct fields and then feeds those fields into the MongoDB driver, a mismatch between expected and provided values can cause the driver to log its configuration state. Since middleBrick checks authentication and data exposure across unauthenticated endpoints, any route that returns server or driver configuration details should be treated as a potential leak channel.

To detect this pattern, middleBrick’s Data Exposure and Authentication checks look for indicators such as credentials in error payloads, verbose stack traces, or missing controls around configuration visibility. The LLM/AI Security module further examines whether prompts or system messages could coax the service into revealing internal configuration, including database connection strings.

Remediation focuses on ensuring MongoDB connection details never propagate into HTTP responses, logs, or error payloads, and that the driver is configured with secure defaults. Always load the connection string from environment variables at startup and keep it confined to the initialization code.

Secure MongoDB connection initialization

Initialize the MongoDB client once, using options that avoid embedding the URI in logs. Use options.Client().ApplyURI with a URI read from environment variables, and avoid constructing client instances per request.

// main.go
package main

import (
	"context"
	"log"
	"os"

	"go.mongodb.org/mongo-driver/mongo"
	"go.mongodb.org/mongo-driver/mongo/options"
)

var client *mongo.Client

func initClient() error {
	uri := os.Getenv("MONGODB_URI")
	if uri == "" {
		return fmt.Errorf("MONGODB_URI environment variable is not set")
	}
	var err error
	client, err = mongo.Connect(context.TODO(), options.Client().ApplyURI(uri))
	if err != nil {
		return err
	}
	// Ping to verify connectivity without exposing details
	if err = client.Ping(context.TODO(), nil); err != nil {
		return err
	}
	return nil
}

Safe handler implementation

Handlers should use the shared client and avoid passing configuration into responses. Ensure errors are sanitized and do not include the MongoDB URI or driver internals.

// handlers.go
package main

import (
	"context"
	"net/http"

	"github.com/labstack/echo/v4"
	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/mongo"
)

func getData(c echo.Context) error {
	collection := client.Database("appdb").Collection("records")
	cursor, err := collection.Find(c.Request().Context(), bson.M{})
	if err != nil {
		// Do not include err.Error() if it might contain sensitive context
		return c.JSON(http.StatusInternalServerError, map[string]string{"error": "internal server error"})
	}
	defer cursor.Close(c.Request().Context())
	var results []bson.M
	if err = cursor.All(c.Request().Context(), &results); err != nil {
		return c.JSON(http.StatusInternalServerError, map[string]string{"error": "internal server error"})
	}
	return c.JSON(http.StatusOK, results)
}

Log and error handling hygiene

Configure logging to exclude sensitive fields and ensure that any use of log.Println or structured log fields does not include the connection string or database name if it could be considered sensitive. Use standard library log configuration or a third-party logger with field filtering.

// Example of safe logging without connection details
log.Printf("request_id=%s method=%s path=%s", c.Request().Header.Get("X-Request-ID"), c.Request().Method, c.Request().URL.Path)

Environment and deployment practices

Use container secrets or platform-managed environment variables to inject MONGODB_URI at runtime rather than baking it into images or source code. Restrict filesystem permissions for configuration files and avoid printing environment contents in debug endpoints.

middleBrick’s Continuous Monitoring can help detect regressions by scanning on a schedule; if you promote the service through CI/CD, the GitHub Action can gate merges when new endpoints introduce insecure patterns. For rapid verification, run the CLI scan middlebrick scan <url> against your staging environment to confirm that no credentials appear in observable outputs.