Integrity Failures in Buffalo with Basic Auth

Buffalo is a convention-over-configuration web framework for Go that encourages rapid development. When Basic Auth is used without additional integrity protections, the framework can expose endpoints to integrity failures, where an attacker can modify in-transit parameters or headers and the server may process the altered request as valid. This occurs because Basic Auth provides authentication (proof of identity) but not message integrity or origin authentication beyond the initial credentials.

In Buffalo, routes are typically registered in actions/app.go using the resources helper or explicit get/post calls. If a route relies solely on HTTP Basic Auth (e.g., via beforeAction with auth.Basic) and does not enforce additional checks such as CSRF tokens, strict content-type validation, or idempotency keys, an attacker who can observe or guess a valid credential can replay or tamper with requests.

Consider a PUT or PATCH endpoint that updates user profile data. With Basic Auth, the username and password are base64-encoded but not cryptographically protected against modification. An attacker who knows the endpoint and has a valid credential pair can intercept the request (e.g., on an unencrypted HTTP channel) and change the payload fields, such as changing role from user to admin, or altering financial transaction amounts. Because Buffalo does not implicitly sign or version requests, the server accepts the modified payload if the route logic does not validate each field against business rules or enforce strict parameter whitelisting.

This combination maps to OWASP API Top 10 controls: integrity failures often relate to API1:2023 – Broken Object Level Authorization and API5:2023 – Broken Function Level Authorization. In Buffalo, if a developer places a beforeAction that only verifies credentials and then proceeds to update records based on URL parameters (e.g., params.UserID) without re-verifying ownership or integrity, an attacker can change the ID in the URL and escalate privileges or access other users’ resources.

Additionally, Basic Auth over unencrypted channels enables credential exposure, but even over TLS, integrity failures arise when request bodies or headers are not validated for unexpected mutations. For example, an attacker might add or modify headers such as X-Requested-With or Content-Type to bypass expected content-type constraints in Buffalo’s parameter parsing. Without explicit schema validation (e.g., using a library that enforces strict struct binding and omits empty or extra fields), Buffalo’s default parameter binding may populate fields incorrectly, leading to logic bypasses or unsafe updates.

In an LLM/AI security context, integrity failures in Buffalo with Basic Auth can be probed by testing whether endpoints reflect tampered inputs in responses, or whether mutated requests produce unexpected state changes. During active testing, probes that modify request payloads or headers after successful authentication can reveal whether the application enforces integrity at the model or handler layer. Findings from such scans should highlight missing integrity controls and recommend server-side validation, cryptographic signing of critical operations, or use of middleware that ensures request consistency before invoking business logic.

Remediation centers on adding integrity checks around Basic Auth usage, ensuring that each request is validated for authenticity and correctness before performing state-changing operations.

1. Enforce HTTPS and reject cleartext Basic Auth

Always serve Basic Auth over TLS to prevent credential interception. In Buffalo, you can enforce this at the middleware or server level, but application code should also reject non-TLS requests when sensitive operations are performed.

2. Use strict parameter binding and validation

Do not rely on URL or query parameters for sensitive updates without validating them against the authenticated user’s context. Use Buffalo’s built-in binding with explicit structs and validate each field.

// actions/user_update.go
package actions

import (
	"net/http"

	"github.com/gobuffalo/buffalo"
	"github.com/gobuffalo/validate/v3"
)

type UserUpdateParams struct {
	Role  string `json:"role" validate:"omitempty,oneof=user admin"`
	Email string `json:"email" validate:"omitempty,email"`
}

func UserUpdate(c buffalo.Context) error {
	// Ensure the request uses HTTPS
	if c.Request().TLS == nil {
		return c.Render(403, r.Text("HTTPS required"))
	}

	// Authenticate via Basic Auth before binding
	user, pass, ok := c.Request().BasicAuth()
	if !ok || !validateBasicAuth(user, pass) {
		c.Response().Header().Set("WWW-Authenticate", `Basic realm="restricted"`)
		return c.Render(401, r.Text("Unauthorized"))
	}

	// Bind and validate the payload
	var params UserUpdateParams
	if err := c.Bind(¶ms); err != nil {
		return c.Render(400, r.JSON(map[string]string{"error": "invalid payload"}))
	}
	if err := validate.ValidateStruct(¶ms); err != nil {
		return c.Render(400, r.JSON(map[string]string{"error": err.Error()}))
	}

	// Re-verify that the authenticated user is allowed to update the target user
	// (Assume user context is available via c.Values()["current_user"])
	currentUser := c.Values()["current_user"].(User)
	if params.Role == "admin" && currentUser.Role != "admin" {
		return c.Render(403, r.Text("Insufficient permissions"))
	}

	// Proceed with update using params.Email, params.Role, etc.
	// Ensure updates are performed with parameterized queries or ORM safeguards
	return c.Render(200, r.JSON(map[string]string{"status": "updated"}))
}

func validateBasicAuth(user, pass string) bool {
	// Replace with secure credential store lookup
	return user == "alice" && pass == "s3cr3t"
}

3. Add idempotency or request signing for state-changing operations

For critical endpoints, require an idempotency key or a signed request header that the server can verify. This prevents replay and tampering even if credentials are compromised.

// actions/transfer.go
package actions

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"net/http"
	"time"

	"github.com/gobuffalo/buffalo"
)

func TransferFunds(c buffalo.Context) error {
	authUser, authPass, _ := c.Request().BasicAuth()
	if !isValidAuth(authUser, authPass) {
		return c.Render(401, r.Text("Unauthorized"))
	}

	// Expect headers: X-Request-Timestamp, X-Request-Signature
	timestamp := c.Request().Header.Get("X-Request-Timestamp")	signature := c.Request().Header.Get("X-Request-Signature")
	if timestamp == "" || signature == "" {
		return c.Render(400, r.Text("Missing security headers"))
	}

	// Reject stale requests (replay protection)
	reqTime, err := time.Parse(time.RFC3339, timestamp)
	if err != nil || time.Since(reqTime) > 5*time.Minute {
		return c.Render(400, r.Text("Request expired"))
	}

	// Verify HMAC signature over the request body + timestamp
	secret := []byte("shared-secret-key")
	h := hmac.New(sha256.New, secret)
	h.Write([]byte(timestamp))
	h.Write(c.Request().Body) // Note: in production, read a copy of the body
	expected := hex.EncodeToString(h.Sum(nil))

	if !hmac.Equal([]byte(expected), []byte(signature)) {
		return c.Render(403, r.Text("Invalid signature"))
	}

	// Parse and validate payload
	var tx struct {
		To   string `json:"to" validate:"required,uuid"`
		Amount int   `json:"amount" validate:"required,min=1"`
	}
	if err := c.Bind(&tx); err != nil {
		return c.Render(400, r.JSON(map[string]string{"error": "invalid body"}))
	}
	if err := validate.ValidateStruct(&tx); err != nil {
		return c.Render(400, r.JSON(map[string]string{"error": err.Error()}))
	}

	// Execute transfer ensuring user can modify the target account
	// ...
	return c.Render(200, r.JSON(map[string]string{"status": "ok"}))
}

func isValidAuth(user, pass string) bool {
	return user == "bob" && pass == "secret123"
}

4. Apply per-route beforeAction with integrity-aware handlers

Use Buffalo’s beforeAction to enforce authentication and then additional checks within handlers, rather than relying on Basic Auth alone to gate logic.

// actions/app.go
package actions

import (
	"github.com/gobuffalo/buffalo"
)

func App() *buffalo.App {
	app := buffalo.New(buffalo.Options{
		// ...
	})

	// Example: require auth for sensitive collections
	app.GET("/admin/users", AdminUsers, requireAuth, requireAdminIntegrity)
	app.PUT("/admin/users/{userID}", UpdateUser, requireAuth, requireIntegrity)
	return app
}

func requireAuth(c buffalo.Context) error {
	_, _, ok := c.Request().BasicAuth()
	if !ok {
		c.Response().Header().Set("WWW-Authenticate", `Basic realm="api"`)
		return c.Render(401, r.Text("Unauthorized"))
	}
	return nil
}

// Additional integrity checks: ensure the authenticated user has rights over the resource
func requireIntegrity(c buffalo.Context) error {
	// e.g., check that userID in URL matches the user derived from credentials or session
	userID := c.Params()["userID"]
	// perform lookup and ownership validation
	return nil
}

By combining HTTPS, strict parameter binding, per-handler authorization, and optional request signing, you mitigate integrity failures in Buffalo applications that use Basic Auth.