feat(backend): bcrypt+jwt auth package and admin seeding

backend/internal/auth/auth.go

@@ -0,0 +1,54 @@
+package auth
+
+import (
+	"crypto/subtle"
+	"errors"
+	"time"
+
+	"github.com/golang-jwt/jwt/v5"
+	"golang.org/x/crypto/bcrypt"
+)
+
+var ErrToken = errors.New("invalid token")
+
+func HashPassword(plain string) (string, error) {
+	b, err := bcrypt.GenerateFromPassword([]byte(plain), 12)
+	return string(b), err
+}
+
+func CheckPassword(hash, plain string) bool {
+	return bcrypt.CompareHashAndPassword([]byte(hash), []byte(plain)) == nil
+}
+
+type Claims struct {
+	UID  int64  `json:"uid"`
+	Role string `json:"role"`
+	jwt.RegisteredClaims
+}
+
+func Sign(secret []byte, uid int64, role string) (string, error) {
+	return SignWithTTL(secret, uid, role, 72*time.Hour)
+}
+
+func SignWithTTL(secret []byte, uid int64, role string, ttl time.Duration) (string, error) {
+	t := jwt.NewWithClaims(jwt.SigningMethodHS256, Claims{
+		UID: uid, Role: role,
+		RegisteredClaims: jwt.RegisteredClaims{ExpiresAt: jwt.NewNumericDate(time.Now().Add(ttl))},
+	})
+	return t.SignedString(secret)
+}
+
+func Parse(secret []byte, token string) (*Claims, error) {
+	c := &Claims{}
+	parsed, err := jwt.ParseWithClaims(token, c, func(t *jwt.Token) (any, error) {
+		m, ok := t.Method.(*jwt.SigningMethodHMAC)
+		if !ok || subtle.ConstantTimeCompare([]byte(m.Alg()), []byte("HS256")) != 1 {
+			return nil, ErrToken
+		}
+		return secret, nil
+	}, jwt.WithValidMethods([]string{"HS256"}))
+	if err != nil || !parsed.Valid {
+		return nil, ErrToken
+	}
+	return c, nil
+}

backend/internal/auth/auth_test.go

@@ -0,0 +1,40 @@
+package auth
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestHashCheck(t *testing.T) {
+	h, err := HashPassword("hunter2")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasPrefix(h, "$2a$") || !CheckPassword(h, "hunter2") || CheckPassword(h, "wrong") {
+		t.Fatal("bcrypt wrong")
+	}
+}
+
+func TestSignParse(t *testing.T) {
+	secret := []byte("k")
+	tok, err := Sign(secret, 7, "admin")
+	if err != nil {
+		t.Fatal(err)
+	}
+	c, err := Parse(secret, tok)
+	if err != nil || c.UID != 7 || c.Role != "admin" {
+		t.Fatalf("parse: %v %+v", err, c)
+	}
+	if _, err := Parse([]byte("other"), tok); err == nil {
+		t.Fatal("must reject wrong secret")
+	}
+	expired, _ := SignWithTTL(secret, 1, "member", -time.Hour)
+	if _, err := Parse(secret, expired); err == nil {
+		t.Fatal("must reject expired")
+	}
+	// alg 混淆攻击:none 必须拒
+	if _, err := Parse(secret, "eyJhbGciOiJub25lIiwidHlwIjoiSldUIn0.eyJ1aWQiOjF9."); err == nil {
+		t.Fatal("must reject alg=none")
+	}
+}

backend/internal/seed/seed.go

@@ -0,0 +1,29 @@
+package seed
+
+import (
+	"context"
+	"log"
+
+	"booklib/internal/auth"
+	"booklib/internal/store"
+)
+
+func Admin(ctx context.Context, s *store.Store, user, pass string) error {
+	if user == "" || pass == "" {
+		return nil
+	}
+	n, err := s.CountUsers(ctx)
+	if err != nil || n > 0 {
+		return err
+	}
+	h, err := auth.HashPassword(pass)
+	if err != nil {
+		return err
+	}
+	if _, err := s.CreateUser(ctx, user, h, "admin"); err != nil {
+		log.Printf("seed admin %q may already exist: %v", user, err)
+		return nil
+	}
+	log.Printf("seeded initial admin user %q", user)
+	return nil
+}

backend/internal/seed/seed_test.go

@@ -0,0 +1,41 @@
+package seed
+
+import (
+	"context"
+	"os"
+	"testing"
+
+	"booklib/internal/db"
+	"booklib/internal/store"
+)
+
+func TestSeedOnlyWhenEmpty(t *testing.T) {
+	url := os.Getenv("DATABASE_URL")
+	if url == "" {
+		t.Skip("DATABASE_URL not set")
+	}
+	ctx := context.Background()
+	p, _ := db.Connect(ctx, url)
+	if err := db.Migrate(ctx, p); err != nil {
+		t.Fatal(err)
+	}
+	s := store.New(p)
+	p.Exec(ctx, "DELETE FROM reading_progress; DELETE FROM books; DELETE FROM libraries; DELETE FROM users")
+	if err := Admin(ctx, s, "admin", "pw12345"); err != nil {
+		t.Fatal(err)
+	}
+	if err := Admin(ctx, s, "admin2", "pw12345"); err != nil { // 已有用户 → no-op
+		t.Fatal(err)
+	}
+	n, _ := s.CountUsers(ctx)
+	if n != 1 {
+		t.Fatalf("want 1 user got %d", n)
+	}
+	u, err := s.GetUserByName(ctx, "admin")
+	if err != nil || u.Role != "admin" {
+		t.Fatalf("bad admin: %+v %v", u, err)
+	}
+	if err := Admin(ctx, s, "", ""); err != nil {
+		t.Fatal("empty creds must no-op, got", err)
+	}
+}