NEXUS-1: Initial commit of Nexus

internal/auth/jwt.go

@@ -0,0 +1,126 @@
+package auth
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"time"
+
+	"git.arcline.it/ArclineIT/nexus/internal/config"
+	"github.com/golang-jwt/jwt/v5"
+	"github.com/google/uuid"
+)
+
+// Claims represents the custom JWT claims for Nexus.
+type Claims struct {
+	jwt.RegisteredClaims
+	Email     string `json:"email"`
+	TokenType string `json:"token_type"` // "access" or "refresh"
+}
+
+// TokenPair holds both access and refresh tokens.
+type TokenPair struct {
+	AccessToken  string `json:"access_token"`
+	RefreshToken string `json:"refresh_token"`
+	ExpiresIn    int64  `json:"expires_in"` // seconds until access token expires
+	TokenType    string `json:"token_type"` // always "Bearer"
+}
+
+// GenerateTokenPair creates a new access + refresh token pair for a user.
+func GenerateTokenPair(cfg *config.Config, userID uuid.UUID, email string) (*TokenPair, error) {
+	now := time.Now()
+
+	accessClaims := Claims{
+		RegisteredClaims: jwt.RegisteredClaims{
+			Issuer:    cfg.Auth.Issuer,
+			Subject:   userID.String(),
+			Audience:  jwt.ClaimStrings{cfg.Auth.Audience},
+			ExpiresAt: jwt.NewNumericDate(now.Add(cfg.Auth.AccessTokenDuration)),
+			IssuedAt:  jwt.NewNumericDate(now),
+			NotBefore: jwt.NewNumericDate(now),
+			ID:        uuid.New().String(),
+		},
+		Email:     email,
+		TokenType: "access",
+	}
+
+	accessToken, err := signToken(cfg, accessClaims)
+	if err != nil {
+		return nil, fmt.Errorf("signing access token: %w", err)
+	}
+
+	refreshClaims := Claims{
+		RegisteredClaims: jwt.RegisteredClaims{
+			Issuer:    cfg.Auth.Issuer,
+			Subject:   userID.String(),
+			Audience:  jwt.ClaimStrings{cfg.Auth.Audience},
+			ExpiresAt: jwt.NewNumericDate(now.Add(cfg.Auth.RefreshTokenDuration)),
+			IssuedAt:  jwt.NewNumericDate(now),
+			NotBefore: jwt.NewNumericDate(now),
+			ID:        uuid.New().String(),
+		},
+		Email:     email,
+		TokenType: "refresh",
+	}
+
+	refreshToken, err := signToken(cfg, refreshClaims)
+	if err != nil {
+		return nil, fmt.Errorf("signing refresh token: %w", err)
+	}
+
+	return &TokenPair{
+		AccessToken:  accessToken,
+		RefreshToken: refreshToken,
+		ExpiresIn:    int64(cfg.Auth.AccessTokenDuration.Seconds()),
+		TokenType:    "Bearer",
+	}, nil
+}
+
+// ValidateToken parses and validates a JWT token string.
+func ValidateToken(cfg *config.Config, tokenString string) (*Claims, error) {
+	token, err := jwt.ParseWithClaims(
+		tokenString,
+		&Claims{},
+		func(t *jwt.Token) (interface{}, error) {
+			if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
+				return nil, fmt.Errorf("unexpected signing method: %v", t.Header["alg"])
+			}
+			return []byte(cfg.Auth.JWTSecret), nil
+		},
+	)
+	if err != nil {
+		return nil, fmt.Errorf("parsing token: %w", err)
+	}
+
+	claims, ok := token.Claims.(*Claims)
+	if !ok || !token.Valid {
+		return nil, fmt.Errorf("invalid token")
+	}
+
+	return claims, nil
+}
+
+// HashToken returns the SHA-256 hash of a token string (for storage).
+func HashToken(token string) string {
+	hash := sha256.Sum256([]byte(token))
+	return hex.EncodeToString(hash[:])
+}
+
+// GenerateSecureToken creates a cryptographically random token.
+func GenerateSecureToken(length int) (string, error) {
+	bytes := make([]byte, length)
+	if _, err := rand.Read(bytes); err != nil {
+		return "", fmt.Errorf("generating random bytes: %w", err)
+	}
+	return hex.EncodeToString(bytes), nil
+}
+
+func signToken(cfg *config.Config, claims Claims) (string, error) {
+	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
+	signed, err := token.SignedString([]byte(cfg.Auth.JWTSecret))
+	if err != nil {
+		return "", fmt.Errorf("signing token: %w", err)
+	}
+	return signed, nil
+}