first commit

apps/backend/internal/auth/neon.go

@@ -0,0 +1,82 @@
+package auth
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/url"
+	"strings"
+	"time"
+
+	"github.com/MicahParks/keyfunc/v3"
+	"github.com/golang-jwt/jwt/v5"
+)
+
+type Verifier struct {
+	jwks           keyfunc.Keyfunc
+	expectedIssuer string
+	enabled        bool
+	cancel         context.CancelFunc
+}
+
+func NewVerifier(neonAuthURL string) (*Verifier, error) {
+	trimmed := strings.TrimSpace(neonAuthURL)
+	if trimmed == "" {
+		return &Verifier{enabled: false}, nil
+	}
+
+	parsed, err := url.Parse(trimmed)
+	if err != nil {
+		return nil, fmt.Errorf("parse neon auth url: %w", err)
+	}
+
+	expectedIssuer := fmt.Sprintf("%s://%s", parsed.Scheme, parsed.Host)
+	jwksURL := fmt.Sprintf("%s/.well-known/jwks.json", trimmed)
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	jwks, err := keyfunc.NewDefaultCtx(ctx, []string{jwksURL})
+	if err != nil {
+		cancel()
+		return nil, fmt.Errorf("create jwks: %w", err)
+	}
+
+	return &Verifier{
+		jwks:           jwks,
+		expectedIssuer: expectedIssuer,
+		enabled:        true,
+		cancel:         cancel,
+	}, nil
+}
+
+func (v *Verifier) Enabled() bool {
+	return v.enabled
+}
+
+func (v *Verifier) Close() {
+	if v.cancel != nil {
+		v.cancel()
+	}
+}
+
+func (v *Verifier) Verify(tokenString string) (jwt.MapClaims, error) {
+	if !v.enabled {
+		return nil, errors.New("neon auth verifier is disabled")
+	}
+
+	token, err := jwt.Parse(tokenString, v.jwks.Keyfunc,
+		jwt.WithIssuer(v.expectedIssuer),
+		jwt.WithValidMethods([]string{"EdDSA"}),
+		jwt.WithAudience(v.expectedIssuer),
+		jwt.WithLeeway(15*time.Second),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	claims, ok := token.Claims.(jwt.MapClaims)
+	if !ok || !token.Valid {
+		return nil, errors.New("invalid token claims")
+	}
+	return claims, nil
+}