auth-jwt/auth.go

package authjwt

import (
	"encoding/json"
	"net/http"
	"path"
	"strings"

	"github.com/golang-jwt/jwt/v5"

	"code.nochebuena.dev/einherjar/auth/authmw"
	"code.nochebuena.dev/einherjar/contracts/logging"
	"code.nochebuena.dev/einherjar/core/xerrors"
)

// AuthMiddleware verifies the Bearer access token and injects uid + claims into context
// via authmw.SetTokenData. Downstream authmw.EnrichmentMiddleware reads them transparently.
//
// Accepts a Verifier — pass a Signer when the service issues tokens, or a
// NewRSAPublicKeyVerifier/NewECPublicKeyVerifier when it only verifies.
//
// Requests to publicPaths are skipped without verification (path.Match wildcards supported).
// Returns 401 on missing, invalid, or expired tokens.
func AuthMiddleware(logger logging.Logger, verifier Verifier, publicPaths []string) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			for _, pattern := range publicPaths {
				if matched, _ := path.Match(pattern, r.URL.Path); matched {
					next.ServeHTTP(w, r)
					return
				}
			}

			authHeader := r.Header.Get("Authorization")
			if !strings.HasPrefix(authHeader, "Bearer ") {
				writeUnauthorized(logger, w, r)
				return
			}
			tokenStr := strings.TrimPrefix(authHeader, "Bearer ")

			token, err := verifier.Verify(tokenStr)
			if err != nil {
				writeUnauthorized(logger, w, r)
				return
			}

			claims, ok := token.Claims.(jwt.MapClaims)
			if !ok {
				writeUnauthorized(logger, w, r)
				return
			}

			uid, _ := claims["sub"].(string)
			if uid == "" {
				writeUnauthorized(logger, w, r)
				return
			}

			ctx := authmw.SetTokenData(r.Context(), uid, map[string]any(claims))
			next.ServeHTTP(w, r.WithContext(ctx))
		})
	}
}

func writeUnauthorized(logger logging.Logger, w http.ResponseWriter, r *http.Request) {
	logger.WithContext(r.Context()).Warn("auth-jwt: unauthorized",
		"error_code", string(xerrors.ErrUnauthorized),
		"status", http.StatusUnauthorized,
	)
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusUnauthorized)
	_ = json.NewEncoder(w).Encode(map[string]any{
		"code":    string(xerrors.ErrUnauthorized),
		"message": "unauthorized",
	})
}