feat: 实现 TokenManager（JWT 签发/校验/哈希）

backend/go.mod

@@ -28,6 +28,7 @@ require (
 	github.com/go-playground/validator/v10 v10.20.0 // indirect
 	github.com/go-viper/mapstructure/v2 v2.4.0 // indirect
 	github.com/goccy/go-json v0.10.2 // indirect
+	github.com/golang-jwt/jwt/v5 v5.3.1 // indirect
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
 	github.com/jackc/puddle/v2 v2.2.2 // indirect

backend/go.sum

@@ -37,6 +37,8 @@ github.com/go-viper/mapstructure/v2 v2.4.0 h1:EBsztssimR/CONLSZZ04E8qAkxNYq4Qp9L
 github.com/go-viper/mapstructure/v2 v2.4.0/go.mod h1:oJDH3BJKyqBA2TXFhDsKDGDTlndYOZ6rGS0BRZIxGhM=
 github.com/goccy/go-json v0.10.2 h1:CrxCmQqYDkv1z7lO7Wbh2HN93uovUHgrECaO5ZrCXAU=
 github.com/goccy/go-json v0.10.2/go.mod h1:6MelG93GURQebXPDq3khkgXZkazVtN9CRI+MGFi0w8I=
+github.com/golang-jwt/jwt/v5 v5.3.1 h1:kYf81DTWFe7t+1VvL7eS+jKFVWaUnK9cB1qbwn63YCY=
+github.com/golang-jwt/jwt/v5 v5.3.1/go.mod h1:fxCRLWMO43lRc8nhHWY6LGqRcf+1gQWArsqaEUEa5bE=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=

backend/internal/auth/jwt.go

@@ -0,0 +1,111 @@
+package auth
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"time"
+
+	"github.com/golang-jwt/jwt/v5"
+	"github.com/google/uuid"
+)
+
+// 自定义错误。
+var (
+	ErrInvalidToken = errors.New("invalid or expired token")
+)
+
+// Claims JWT 声明。
+type Claims struct {
+	UserID   string `json:"user_id"`
+	Username string `json:"username"`
+	jwt.RegisteredClaims
+}
+
+// TokenManager JWT 令牌管理器。
+type TokenManager struct {
+	secret     []byte
+	accessTTL  time.Duration
+	refreshTTL time.Duration
+}
+
+// NewTokenManager 创建 TokenManager。
+// secret: JWT 签名密钥；accessTTL/refreshTTL: 令牌有效期。
+func NewTokenManager(secret string, accessTTL, refreshTTL time.Duration) *TokenManager {
+	return &TokenManager{
+		secret:     []byte(secret),
+		accessTTL:  accessTTL,
+		refreshTTL: refreshTTL,
+	}
+}
+
+// GeneratePair 生成 access + refresh 令牌对。
+func (tm *TokenManager) GeneratePair(userID, username string) (access, refresh string, err error) {
+	now := time.Now()
+
+	// access token
+	accessClaims := &Claims{
+		UserID:   userID,
+		Username: username,
+		RegisteredClaims: jwt.RegisteredClaims{
+			ExpiresAt: jwt.NewNumericDate(now.Add(tm.accessTTL)),
+			IssuedAt:  jwt.NewNumericDate(now),
+			Issuer:    "camtalk",
+		},
+	}
+	accessTkn := jwt.NewWithClaims(jwt.SigningMethodHS256, accessClaims)
+	access, err = accessTkn.SignedString(tm.secret)
+	if err != nil {
+		return "", "", err
+	}
+
+	// refresh token（含唯一 token_id 用于 DB 关联）
+	tokenID := uuid.New().String()
+	refreshClaims := &Claims{
+		UserID:   userID,
+		Username: username,
+		RegisteredClaims: jwt.RegisteredClaims{
+			ID:        tokenID,
+			ExpiresAt: jwt.NewNumericDate(now.Add(tm.refreshTTL)),
+			IssuedAt:  jwt.NewNumericDate(now),
+			Issuer:    "camtalk",
+		},
+	}
+	refreshTkn := jwt.NewWithClaims(jwt.SigningMethodHS256, refreshClaims)
+	refresh, err = refreshTkn.SignedString(tm.secret)
+	return
+}
+
+// ValidateAccess 校验 access token 并返回 Claims。
+func (tm *TokenManager) ValidateAccess(tokenStr string) (*Claims, error) {
+	return tm.validate(tokenStr)
+}
+
+// ValidateRefresh 校验 refresh token 并返回 Claims。
+func (tm *TokenManager) ValidateRefresh(tokenStr string) (*Claims, error) {
+	return tm.validate(tokenStr)
+}
+
+// validate 解析并校验 JWT。
+func (tm *TokenManager) validate(tokenStr string) (*Claims, error) {
+	token, err := jwt.ParseWithClaims(tokenStr, &Claims{}, func(t *jwt.Token) (interface{}, error) {
+		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
+			return nil, ErrInvalidToken
+		}
+		return tm.secret, nil
+	})
+	if err != nil {
+		return nil, ErrInvalidToken
+	}
+	claims, ok := token.Claims.(*Claims)
+	if !ok || !token.Valid {
+		return nil, ErrInvalidToken
+	}
+	return claims, nil
+}
+
+// HashToken 对 token 做 SHA256 哈希，用于 DB 存储。
+func HashToken(token string) string {
+	h := sha256.Sum256([]byte(token))
+	return hex.EncodeToString(h[:])
+}