alanyeung-s3/aws/internal/middleware/auth.go

package middleware

import (
	"context"
	"log"
	"net/http"

	"aws-sts-mock/internal/kvdb"
	"aws-sts-mock/pkg/sigv4"
)

// UserValidationMiddleware creates a middleware that validates users against the KV database
func UserValidationMiddleware(db kvdb.KVDB) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			// Extract credentials from context (set by SigV4 middleware)
			creds, ok := r.Context().Value(sigv4.CredentialsContextKey).(sigv4.AWSCredentials)
			if !ok {
				http.Error(w, "Unauthorized", http.StatusUnauthorized)
				return
			}

			// Validate user exists in database
			user, err := db.GetUser(creds.AccessKeyID)
			if err != nil {
				if err == kvdb.ErrUserNotFound {
					log.Printf("User not found: %s", creds.AccessKeyID)
					http.Error(w, "Access Denied: User not found", http.StatusForbidden)
					return
				}
				log.Printf("Error validating user: %v", err)
				http.Error(w, "Internal Server Error", http.StatusInternalServerError)
				return
			}

			// Validate secret key matches
			if user.SecretAccessKey != creds.SecretAccessKey {
				log.Printf("Invalid credentials for user: %s", creds.AccessKeyID)
				http.Error(w, "Access Denied: Invalid credentials", http.StatusForbidden)
				return
			}

			// Update context with validated user information
			ctx := context.WithValue(r.Context(), sigv4.CredentialsContextKey, sigv4.AWSCredentials{
				AccessKeyID:     user.AccessKeyID,
				SecretAccessKey: user.SecretAccessKey,
				AccountID:       user.AccountID,
			})

			log.Printf("User validated: %s (Account: %s)", user.Username, user.AccountID)

			// Continue to next handler
			next.ServeHTTP(w, r.WithContext(ctx))
		})
	}
}

// ChainMiddleware chains multiple middleware functions
func ChainMiddleware(middlewares ...func(http.Handler) http.Handler) func(http.Handler) http.Handler {
	return func(final http.Handler) http.Handler {
		for i := len(middlewares) - 1; i >= 0; i-- {
			final = middlewares[i](final)
		}
		return final
	}
}