docs: 新增移动端界面截图（响应式布局）

fix(security): 修复 P2 中危项（cookie/协议限速/路径遍历/默认口令/中继TLS/安全头/信息泄露）
- 会话 cookie 增加 Secure 标志；新增 [web].cookie_secure 配置（默认 true，仅本地 HTTP 调试关闭；缺失字段按安全默认处理） - SMTP/IMAP/POP3 认证接入封禁体系（store.RecordAuthFailure 与 Web 共用 ban_entries）：失败计数达 ban.max_fail_attempts 即封禁 IP，已封禁 IP 拒绝认证，堵住协议层暴力破解 - 附件存储路径遍历防护重写：FullPath 白名单校验（UUID 文件名格式） + baseDir 前缀兜底，非法路径返回错误；Save 扩展名白名单化 - 初始管理员不再使用 admin/admin：密码取 MAILGO_ADMIN_PASSWORD 或随机生成并打印一次；新增 MustChangePassword 首登强制改密（管理员重置密码同样触发） - 外发中继默认验证 TLS 证书（保护 AUTH 凭据，防 MITM），直投 MX 保持机会式 TLS；新增 outbound.relay_tls_insecure 开关（默认 false） - 新增安全响应头中间件：HSTS、X-Frame-Options DENY、nosniff、 Referrer-Policy、基础 CSP（frame-ancestors 'none' 防点击劫持， connect-src/form-action 'self' 防数据外泄） - LDAP/OAuth 登录错误统一为通用文案，原始错误只写日志，不再回显邮箱/内部细节（防用户枚举与信息泄露） - 新增 25 个回归测试：cookie 标志、封禁阈值、路径遍历用例、中继 TLS 验证（自签证书 STARTTLS 集成）、安全头、OAuth 文案部署注意：升级后所有会话失效需重新登录；若直接以 HTTP 提供服务需显式配置 cookie_secure = false。
2026-08-19 16:48:26 +08:00 · 2026-08-19 16:45:21 +08:00 · 2026-08-19 16:31:25 +08:00 · 2026-08-19 16:21:28 +08:00 · 2026-08-17 23:18:30 -04:00 · 2026-08-17 23:08:15 -04:00
40 changed files with 2106 additions and 327 deletions
@@ -82,6 +82,11 @@ attach_dir = "/srv/mail_go/attachments"     # 附件存储目录

 [web]
 addr = ":8080"                             # 监听地址，支持 TCP 端口或 Unix socket
+secret_key = ""                             # Web 会话签名密钥；留空时首次启动自动生成
+                                           # 随机密钥并写入本文件（请妥善备份，泄露/丢失
+                                           # 分别意味着会话可被伪造/所有登录态失效）
+cookie_secure = true                        # 会话 cookie 仅通过 HTTPS 传输（Secure 标志）；
+                                           # 仅本地 HTTP 调试时才改为 false

 [smtp]
 addr = ":25"                               # SMTP 明文端口
@@ -140,6 +145,9 @@ relay_port = 587                         # 465 = 隐式 TLS，其他端口按需
 relay_user = ""                          # 中继认证用户名（AUTH PLAIN）
 relay_password = ""                      # 中继认证密码
 relay_starttls = true                    # 非 465 端口是否使用 STARTTLS
+relay_tls_insecure = false                # 是否跳过中继服务器 TLS 证书验证；
+                                          # 默认验证证书（保护中继凭据），仅自签证书
+                                          # 内网中继且明确知晓风险时才改为 true
 ip_family = "ipv4"                       # 出站地址族：ipv4（默认）| ipv6 | auto
 source_ip = ""                           # 出站源地址绑定（如静态 IPv6 地址），留空由内核选择
 ```
@@ -175,6 +183,16 @@ addr = "/run/mail_go/web.sock"

 当 `addr` 以 `/` 开头时，Gin 自动以 Unix socket 方式监听。

+### 3. 指定会话密钥（容器/多实例部署）
+
+会话签名密钥可通过环境变量 `MAILGO_SECRET_KEY` 覆盖（优先于配置文件，且不会写入磁盘）：
+
+```bash
+MAILGO_SECRET_KEY="$(openssl rand -hex 32)" mail_go
+```
+
+要求：长度至少 16 字节；留空时由配置文件提供（首次启动自动生成）。更换密钥后所有已登录会话立即失效，用户需重新登录。
+
 Nginx 反向代理配置：

 ```nginx
@@ -1,7 +1,10 @@
 package config

 import (
+	"crypto/rand"
+	"encoding/hex"
 	"fmt"
+	"log"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -25,8 +28,29 @@ type StorageConfig struct {
 // WebConfig holds web server settings.
 type WebConfig struct {
 	Addr string `toml:"addr"`
+	// SecretKey 是 Web 会话 cookie 的签名密钥。留空时首次启动自动生成
+	// 随机密钥并持久化到配置文件；也可通过环境变量 MAILGO_SECRET_KEY
+	// 覆盖（覆盖值不落盘，适合容器部署）。
+	SecretKey string `toml:"secret_key"`
+	// CookieSecure 控制会话 cookie 是否仅通过 HTTPS 传输（Secure 标志）。
+	// 默认 true；仅当应用直接以 HTTP 提供服务（本地调试、内网明文）时
+	// 才应改为 false。
+	CookieSecure bool `toml:"cookie_secure"`
 }

+// SecretKeyEnvVar 是覆盖会话签名密钥的环境变量名。
+const SecretKeyEnvVar = "MAILGO_SECRET_KEY"
+
+// InsecureLegacySecretKey 是旧版本硬编码在源码中的会话签名密钥。
+// 源码公开意味着该密钥完全不可信，任何出现都必须替换。
+const InsecureLegacySecretKey = "mail-go-secret-key-change-in-production"
+
+// MinSecretKeyLen 是允许的最短会话密钥长度（字节）。
+const MinSecretKeyLen = 16
+
+// secretKeyRandomBytes 是自动生成密钥的随机字节数（hex 编码后 64 字符）。
+const secretKeyRandomBytes = 32
+
 // SMTPConfig holds SMTP server settings.
 type SMTPConfig struct {
 	Addr           string `toml:"addr"`
@@ -107,6 +131,10 @@ type OutboundConfig struct {
 	RelayUser     string `toml:"relay_user"`     // 中继认证用户名（AUTH PLAIN）
 	RelayPassword string `toml:"relay_password"` // 中继认证密码
 	RelayStartTLS bool   `toml:"relay_starttls"` // 非 465 端口是否使用 STARTTLS
+	// RelayTLSInsecure 是否跳过中继服务器的 TLS 证书验证。
+	// 默认 false（验证证书），避免凭据被中间人截获；仅当使用自签证书的
+	// 内网中继且明确知晓风险时才设为 true。
+	RelayTLSInsecure bool `toml:"relay_tls_insecure"`

 	// IP family and source address binding for outbound connections.
 	IPFamily string `toml:"ip_family"` // ipv4（默认，PTR/SPF 最可靠）| ipv6 | auto
@@ -169,7 +197,8 @@ func defaultConfig() *Config {
 			AttachDir: filepath.Join(bd, "attachments"),
 		},
 		Web: WebConfig{
-			Addr: DefaultWebPort,
+			Addr:         DefaultWebPort,
+			CookieSecure: true,
 		},
 		SMTP: SMTPConfig{
 			Addr:           fmt.Sprintf(":%d", DefaultSMTPPort),
@@ -298,6 +327,63 @@ func mergeDefaults(cfg *Config, defaults *Config) *Config {
 	return cfg
 }

+// generateSecretKey generates a cryptographically random session key,
+// hex-encoded (64 characters for 32 random bytes).
+func generateSecretKey() (string, error) {
+	buf := make([]byte, secretKeyRandomBytes)
+	if _, err := rand.Read(buf); err != nil {
+		return "", fmt.Errorf("生成随机会话密钥失败: %w", err)
+	}
+	return hex.EncodeToString(buf), nil
+}
+
+// ensureSecretKey guarantees that cfg holds a trustworthy session key:
+// an empty value or the known insecure legacy default is replaced with a
+// freshly generated random key. The caller is responsible for persisting
+// the updated config.
+func ensureSecretKey(cfg *Config) error {
+	if cfg.Web.SecretKey != "" && cfg.Web.SecretKey != InsecureLegacySecretKey {
+		return nil
+	}
+	key, err := generateSecretKey()
+	if err != nil {
+		return err
+	}
+	if cfg.Web.SecretKey == InsecureLegacySecretKey {
+		log.Printf("检测到不安全的旧默认会话密钥，已自动更换为随机密钥（所有已登录会话将失效）")
+	} else {
+		log.Printf("已生成随机会话密钥并写入配置文件（Web 会话签名密钥，请妥善备份）")
+	}
+	cfg.Web.SecretKey = key
+	return nil
+}
+
+// applySecretKeyEnv lets the MAILGO_SECRET_KEY environment variable
+// override the key loaded from the config file. The override value is
+// never persisted to disk.
+func applySecretKeyEnv(cfg *Config) *Config {
+	if env := os.Getenv(SecretKeyEnvVar); env != "" {
+		cfg.Web.SecretKey = env
+	}
+	return cfg
+}
+
+// ValidateSecretKey rejects session signing keys that are missing, too
+// short, or the known insecure legacy default hardcoded in old versions.
+func ValidateSecretKey(key string) error {
+	if key == "" {
+		return fmt.Errorf("Web 会话密钥为空，拒绝启动：请检查配置文件 [web].secret_key 或环境变量 %s", SecretKeyEnvVar)
+	}
+	if key == InsecureLegacySecretKey {
+		return fmt.Errorf("Web 会话密钥为已知不安全的旧默认值，拒绝启动：请删除配置文件 [web].secret_key 后重启以自动生成随机密钥")
+	}
+	if len(key) < MinSecretKeyLen {
+		return fmt.Errorf("Web 会话密钥过短（%d 字节，最少 %d）：请检查 %s 或 [web].secret_key",
+			len(key), MinSecretKeyLen, SecretKeyEnvVar)
+	}
+	return nil
+}
+
 // writeConfig writes the configuration to the given file path.
 // It creates the parent directories if they don't exist.
 func writeConfig(path string, cfg *Config) error {
@@ -316,6 +402,11 @@ func writeConfig(path string, cfg *Config) error {
 	if err := enc.Encode(cfg); err != nil {
 		return fmt.Errorf("写入配置文件失败: %w", err)
 	}
+
+	// 配置文件包含会话密钥、中继密码等敏感信息，收紧为仅属主可读写
+	if err := os.Chmod(path, 0600); err != nil {
+		return fmt.Errorf("设置配置文件权限失败 %s: %w", path, err)
+	}
 	return nil
 }

@@ -323,15 +414,23 @@ func writeConfig(path string, cfg *Config) error {
 // If the configuration file does not exist, it creates one with default values.
 // If the file exists but has missing fields, they are filled with defaults and the file is updated.
 func LoadConfig() (*Config, error) {
-	path := configFilePath()
+	return loadConfigFrom(configFilePath())
+}
+
+// loadConfigFrom implements LoadConfig against an explicit file path so it
+// can be unit-tested with temporary directories.
+func loadConfigFrom(path string) (*Config, error) {
 	defaults := defaultConfig()

 	// If config file doesn't exist, create it with defaults
 	if _, err := os.Stat(path); os.IsNotExist(err) {
+		if err := ensureSecretKey(defaults); err != nil {
+			return nil, err
+		}
 		if mkErr := writeConfig(path, defaults); mkErr != nil {
 			return nil, mkErr
 		}
-		return defaults, nil
+		return applySecretKeyEnv(defaults), nil
 	}

 	// Read existing config file
@@ -345,11 +444,20 @@ func LoadConfig() (*Config, error) {
 		return nil, fmt.Errorf("解析配置文件失败: %w", err)
 	}

-	// relay_starttls defaults to true for safety; the raw file is checked
-	// because TOML decoding cannot distinguish an absent bool from false.
+	// relay_starttls 与 web.cookie_secure 默认值为 true for safety;
+	// the raw file is checked because TOML decoding cannot distinguish
+	// an absent bool from false.
 	if !strings.Contains(string(data), "relay_starttls") {
 		cfg.Outbound.RelayStartTLS = defaults.Outbound.RelayStartTLS
 	}
+	if !strings.Contains(string(data), "cookie_secure") {
+		cfg.Web.CookieSecure = defaults.Web.CookieSecure
+	}
+
+	// 会话密钥缺失或不安全时补发随机密钥（随下面的写回一并落盘）
+	if err := ensureSecretKey(cfg); err != nil {
+		return nil, err
+	}

 	// Merge defaults for any missing fields
 	merged := mergeDefaults(cfg, defaults)
@@ -360,5 +468,5 @@ func LoadConfig() (*Config, error) {
 		return nil, writeErr
 	}

-	return merged, nil
+	return applySecretKeyEnv(merged), nil
 }
@@ -0,0 +1,191 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+func TestGenerateSecretKey(t *testing.T) {
+	key, err := generateSecretKey()
+	if err != nil {
+		t.Fatalf("generateSecretKey() error: %v", err)
+	}
+	// 32 随机字节 hex 编码 = 64 字符
+	if len(key) != secretKeyRandomBytes*2 {
+		t.Fatalf("key length = %d, want %d", len(key), secretKeyRandomBytes*2)
+	}
+
+	// 两次生成必须不同
+	key2, err := generateSecretKey()
+	if err != nil {
+		t.Fatalf("generateSecretKey() error: %v", err)
+	}
+	if key == key2 {
+		t.Fatal("generated keys must be unique")
+	}
+
+	if key == InsecureLegacySecretKey {
+		t.Fatal("generated key must never equal the legacy insecure default")
+	}
+}
+
+func TestLoadConfigFirstBootGeneratesSecretKey(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "mail_go.toml")
+
+	cfg, err := loadConfigFrom(path)
+	if err != nil {
+		t.Fatalf("loadConfigFrom() error: %v", err)
+	}
+	if cfg.Web.SecretKey == "" {
+		t.Fatal("secret key should be generated on first boot")
+	}
+
+	// 密钥必须落盘，保证重启后会话不失效
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("read config file: %v", err)
+	}
+	if !strings.Contains(string(data), "secret_key = \""+cfg.Web.SecretKey+"\"") {
+		t.Fatalf("generated secret key should be persisted, file content:\n%s", data)
+	}
+
+	// 第二次加载返回相同密钥（会话保持）
+	cfg2, err := loadConfigFrom(path)
+	if err != nil {
+		t.Fatalf("second loadConfigFrom() error: %v", err)
+	}
+	if cfg2.Web.SecretKey != cfg.Web.SecretKey {
+		t.Fatalf("secret key must be stable across restarts: %q != %q", cfg2.Web.SecretKey, cfg.Web.SecretKey)
+	}
+
+	// 配置文件包含敏感信息，权限必须为 0600（Windows 无 POSIX 权限，跳过）
+	if runtime.GOOS != "windows" {
+		info, err := os.Stat(path)
+		if err != nil {
+			t.Fatalf("stat config file: %v", err)
+		}
+		if perm := info.Mode().Perm(); perm != 0600 {
+			t.Fatalf("config file mode = %o, want 0600", perm)
+		}
+	}
+}
+
+func TestLoadConfigBackfillsSecretKey(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "mail_go.toml")
+
+	// 模拟旧版本升级：配置文件中没有 secret_key 字段
+	old := "[web]\naddr = \":9090\"\n\n[smtp]\ndomain = \"example.com\"\n"
+	if err := os.WriteFile(path, []byte(old), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	cfg, err := loadConfigFrom(path)
+	if err != nil {
+		t.Fatalf("loadConfigFrom() error: %v", err)
+	}
+	if cfg.Web.SecretKey == "" {
+		t.Fatal("missing secret key should be backfilled")
+	}
+	// 原有字段保持不变
+	if cfg.Web.Addr != ":9090" {
+		t.Fatalf("existing field overwritten: addr = %q", cfg.Web.Addr)
+	}
+	if cfg.SMTP.Domain != "example.com" {
+		t.Fatalf("existing field overwritten: domain = %q", cfg.SMTP.Domain)
+	}
+}
+
+func TestLoadConfigReplacesLegacySecretKey(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "mail_go.toml")
+
+	content := "[web]\naddr = \":8080\"\nsecret_key = \"" + InsecureLegacySecretKey + "\"\n"
+	if err := os.WriteFile(path, []byte(content), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	cfg, err := loadConfigFrom(path)
+	if err != nil {
+		t.Fatalf("loadConfigFrom() error: %v", err)
+	}
+	if cfg.Web.SecretKey == InsecureLegacySecretKey {
+		t.Fatal("legacy insecure secret key must be replaced")
+	}
+	if cfg.Web.SecretKey == "" {
+		t.Fatal("replacement key must be non-empty")
+	}
+
+	// 替换后的密钥必须落盘
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(string(data), InsecureLegacySecretKey) {
+		t.Fatal("legacy key should be removed from the config file")
+	}
+	if !strings.Contains(string(data), cfg.Web.SecretKey) {
+		t.Fatal("replaced key should be persisted")
+	}
+}
+
+func TestSecretKeyEnvOverride(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "mail_go.toml")
+
+	// 先正常生成一个落盘密钥
+	cfg1, err := loadConfigFrom(path)
+	if err != nil {
+		t.Fatalf("first loadConfigFrom() error: %v", err)
+	}
+
+	// 环境变量覆盖运行时密钥
+	envKey := "env-override-secret-key-0123456789abcdef"
+	t.Setenv(SecretKeyEnvVar, envKey)
+
+	cfg2, err := loadConfigFrom(path)
+	if err != nil {
+		t.Fatalf("second loadConfigFrom() error: %v", err)
+	}
+	if cfg2.Web.SecretKey != envKey {
+		t.Fatalf("env var should override the file key: got %q", cfg2.Web.SecretKey)
+	}
+
+	// 环境变量的值不能落盘
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(string(data), envKey) {
+		t.Fatal("env-provided secret must not be persisted to disk")
+	}
+	// 落盘密钥保持原值
+	if !strings.Contains(string(data), cfg1.Web.SecretKey) {
+		t.Fatal("file key should remain unchanged when env override is active")
+	}
+}
+
+func TestValidateSecretKey(t *testing.T) {
+	cases := []struct {
+		name    string
+		key     string
+		wantErr bool
+	}{
+		{"empty", "", true},
+		{"legacy default", InsecureLegacySecretKey, true},
+		{"too short", "short", true},
+		{"valid hex key", "0123456789abcdef0123456789abcdef", false},
+		{"valid env style", "env-override-secret-key-0123456789abcdef", false},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			err := ValidateSecretKey(tc.key)
+			if tc.wantErr && err == nil {
+				t.Fatalf("expected error for key %q", tc.key)
+			}
+			if !tc.wantErr && err != nil {
+				t.Fatalf("unexpected error for key %q: %v", tc.key, err)
+			}
+		})
+	}
+}
@@ -13,6 +13,7 @@ require (
 	github.com/gin-gonic/gin v1.12.0
 	github.com/go-ldap/ldap/v3 v3.4.13
 	github.com/google/uuid v1.6.0
+	github.com/gorilla/securecookie v1.1.2
 	golang.org/x/crypto v0.48.0
 	golang.org/x/oauth2 v0.36.0
 	golang.org/x/text v0.35.0
@@ -38,7 +39,6 @@ require (
 	github.com/goccy/go-json v0.10.5 // indirect
 	github.com/goccy/go-yaml v1.19.2 // indirect
 	github.com/gorilla/context v1.1.2 // indirect
-	github.com/gorilla/securecookie v1.1.2 // indirect
 	github.com/gorilla/sessions v1.4.0 // indirect
 	github.com/jinzhu/inflection v1.0.0 // indirect
 	github.com/jinzhu/now v1.1.5 // indirect
@@ -15,8 +15,11 @@ type User struct {
 	UsedBytes    int64     `gorm:"default:0" json:"used_bytes"`
 	IsActive     bool      `gorm:"default:true" json:"is_active"`
 	IsAdmin      bool      `gorm:"default:false" json:"is_admin"`
-	CreatedAt    time.Time `json:"created_at"`
-	UpdatedAt    time.Time `json:"updated_at"`
+	// MustChangePassword 为 true 时该用户（通常是初始管理员或被重置密码的
+	// 用户）在首次登录后必须修改密码。
+	MustChangePassword bool      `gorm:"default:false" json:"-"`
+	CreatedAt          time.Time `json:"created_at"`
+	UpdatedAt          time.Time `json:"updated_at"`
 }

 // TableName specifies the table name for User.
@@ -10,6 +10,7 @@ import (
 	"strings"
 	"time"

+	"mail_go/config"
 	"mail_go/internal/db"
 	"mail_go/internal/mailutil"
 	"mail_go/internal/store"
@@ -26,12 +27,22 @@ import (
 // imapBackend implements backend.Backend.
 type imapBackend struct {
 	stores *store.Stores
+	banCfg config.BanConfig
 }

 // Login authenticates a user by email and password.
 func (b *imapBackend) Login(connInfo *imap.ConnInfo, username, password string) (backend.User, error) {
+	clientIP := store.ClientIPFromAddr(connInfo.RemoteAddr)
+
+	// 已封禁 IP 一律拒绝认证（防协议层暴力破解）
+	if banned, _ := b.stores.Bans.IsBanned(clientIP); banned {
+		return nil, backend.ErrInvalidCredentials
+	}
+
 	user, err := b.stores.Users.Authenticate(username, password)
 	if err != nil {
+		// 认证失败计数，达到阈值封禁（与 Web 登录共用 ban_entries）
+		b.stores.RecordAuthFailure(clientIP, b.banCfg.MaxFailAttempts, b.banCfg.BanDurationMin)
 		return nil, fmt.Errorf("invalid credentials: %w", err)
 	}

@@ -17,15 +17,17 @@ import (
 type IMAPServer struct {
 	stores    *store.Stores
 	cfg       config.IMAPConfig
+	banCfg    config.BanConfig
 	tlsLoader *tlsutil.Loader
 }

 // NewIMAPServer creates a new IMAP server instance. tlsLoader may be nil
 // when TLS is not configured.
-func NewIMAPServer(cfg config.IMAPConfig, stores *store.Stores, tlsLoader *tlsutil.Loader) *IMAPServer {
+func NewIMAPServer(cfg config.IMAPConfig, stores *store.Stores, tlsLoader *tlsutil.Loader, banCfg config.BanConfig) *IMAPServer {
 	return &IMAPServer{
 		stores:    stores,
 		cfg:       cfg,
+		banCfg:    banCfg,
 		tlsLoader: tlsLoader,
 	}
 }
@@ -40,7 +42,7 @@ func (s *IMAPServer) tlsConfig() (*tls.Config, error) {

 // newServer creates a configured imapserver.Server with the given address.
 func (s *IMAPServer) newServer(addr string, tlsConfig *tls.Config) *imapserver.Server {
-	be := &imapBackend{stores: s.stores}
+	be := &imapBackend{stores: s.stores, banCfg: s.banCfg}
 	srv := imapserver.New(be)
 	srv.Addr = addr
 	srv.TLSConfig = tlsConfig
@@ -49,11 +49,12 @@ func newPermError(format string, args ...interface{}) *DeliveryError {

 // RelayConfig describes a smarthost through which all external mail is sent.
 type RelayConfig struct {
-	Host     string
-	Port     int    // 465 = implicit TLS; other ports may use STARTTLS
-	Username string // AUTH PLAIN credentials (empty = no authentication)
-	Password string
-	StartTLS bool // use STARTTLS on non-465 ports
+	Host        string
+	Port        int    // 465 = implicit TLS; other ports may use STARTTLS
+	Username    string // AUTH PLAIN credentials (empty = no authentication)
+	Password    string
+	StartTLS    bool // use STARTTLS on non-465 ports
+	TLSInsecure bool // skip certificate verification (test-only, credentials leak risk)
 }

 // Mailer performs direct MX delivery (or smarthost relay) of a single message.
@@ -131,6 +132,8 @@ func (m *Mailer) Deliver(from, to string, data []byte) (string, error) {
 }

 // deliverViaRelay sends the message through the configured smarthost.
+// The relay carries AUTH credentials, so its TLS certificate is verified
+// unless RelayTLSInsecure is explicitly enabled.
 func (m *Mailer) deliverViaRelay(from, to string, data []byte) (string, error) {
 	port := m.Relay.Port
 	if port == 0 {
@@ -139,7 +142,8 @@ func (m *Mailer) deliverViaRelay(from, to string, data []byte) (string, error) {
 	implicitTLS := port == 465
 	return m.smtpTransaction(m.Relay.Host, port, implicitTLS,
 		m.Relay.StartTLS && !implicitTLS,
-		m.Relay.Username, m.Relay.Password, from, to, data)
+		m.Relay.Username, m.Relay.Password, from, to, data,
+		m.Relay.TLSInsecure)
 }

 // smtpClient wraps a textproto connection to a remote SMTP server.
@@ -240,13 +244,17 @@ func (c *smtpClient) authPlain(username, password string) error {
 }

 // deliverToHost performs a full SMTP transaction with a single MX host.
+// Direct MX delivery is opportunistic TLS: certificates are not verified
+// because most MX certificates cannot be validated over a cold connection.
 func (m *Mailer) deliverToHost(host, from, to string, data []byte) (string, error) {
-	return m.smtpTransaction(host, m.port(), false, false, "", "", from, to, data)
+	return m.smtpTransaction(host, m.port(), false, false, "", "", from, to, data, true)
 }

 // smtpTransaction performs one complete SMTP session: connect, greeting,
 // optional implicit TLS / STARTTLS, optional AUTH PLAIN, MAIL/RCPT/DATA/QUIT.
-func (m *Mailer) smtpTransaction(host string, port int, implicitTLS, startTLS bool, username, password, from, to string, data []byte) (string, error) {
+// tlsInsecure 控制 TLS 握手时是否跳过证书验证：直投 MX 用 true（机会式
+// TLS），relay 用配置值（默认 false，保护中继凭据）。
+func (m *Mailer) smtpTransaction(host string, port int, implicitTLS, startTLS bool, username, password, from, to string, data []byte, tlsInsecure bool) (string, error) {
 	addr := net.JoinHostPort(host, strconv.Itoa(port))

 	ctx, cancel := context.WithTimeout(context.Background(), m.ConnectTimeout)
@@ -267,11 +275,12 @@ func (m *Mailer) smtpTransaction(host string, port int, implicitTLS, startTLS bo

 	tlsServerName := host
 	if ip := net.ParseIP(host); ip != nil {
-		tlsServerName = "" // no SNI for IP literals
+		// IP literal 同样作为 ServerName：证书验证模式下校验其 IP SAN
+		tlsServerName = ip.String()
 	}

 	if implicitTLS {
-		tlsConn, err := tlsClientHandshake(ctx, conn, tlsServerName, host)
+		tlsConn, err := tlsClientHandshake(ctx, conn, tlsServerName, host, tlsInsecure)
 		if err != nil {
 			return "", err
 		}
@@ -294,7 +303,7 @@ func (m *Mailer) smtpTransaction(host string, port int, implicitTLS, startTLS bo
 			if _, _, err := c.cmd(220, "STARTTLS"); err != nil {
 				return "", err
 			}
-			tlsConn, err := tlsClientHandshake(ctx, conn, tlsServerName, host)
+			tlsConn, err := tlsClientHandshake(ctx, conn, tlsServerName, host, tlsInsecure)
 			if err != nil {
 				return "", err
 			}
@@ -354,10 +363,13 @@ func (m *Mailer) smtpTransaction(host string, port int, implicitTLS, startTLS bo
 }

 // tlsClientHandshake upgrades a plain connection to TLS.
-func tlsClientHandshake(ctx context.Context, conn net.Conn, serverName, host string) (net.Conn, error) {
+// Direct MX delivery passes insecure=true (opportunistic TLS: remote MX
+// certificates often cannot be verified). Relays with AUTH credentials must
+// pass insecure=false so the connection cannot be MITM'd.
+func tlsClientHandshake(ctx context.Context, conn net.Conn, serverName, host string, insecure bool) (net.Conn, error) {
 	tlsConn := tls.Client(conn, &tls.Config{
 		ServerName:         serverName,
-		InsecureSkipVerify: true, // remote MX certificates often cannot be verified
+		InsecureSkipVerify: insecure,
 	})
 	if err := tlsConn.HandshakeContext(ctx); err != nil {
 		return nil, newTempError("TLS handshake with %s failed: %v", host, err)
@@ -2,8 +2,16 @@ package outbound

 import (
 	"bufio"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
 	"encoding/base64"
+	"encoding/pem"
+	"math/big"
 	"net"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -340,3 +348,172 @@ func TestMailerSmarthostRelay(t *testing.T) {
 		t.Fatalf("relay data mismatch.\ngot:  %q\nwant: %q", res.gotData, input)
 	}
 }
+
+// startTLSSMTPServer 起一个支持 STARTTLS 的 SMTP 服务器（自签证书），
+// 供 relay TLS 验证测试使用：未升级 TLS 时广告 STARTTLS 能力，
+// 收到 STARTTLS 后升级为 TLS 并重新 EHLO。
+func startTLSSMTPServer(t *testing.T) (addr string, cleanup func()) {
+	t.Helper()
+	cert, err := tls.X509KeyPair(makeSelfSignedCertPEM(t))
+	if err != nil {
+		t.Fatalf("load self-signed cert: %v", err)
+	}
+	tlsCfg := &tls.Config{Certificates: []tls.Certificate{cert}}
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+
+	go func() {
+		for {
+			conn, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			go func() {
+				defer conn.Close()
+				r := bufio.NewReader(conn)
+				w := bufio.NewWriter(conn)
+				_, _ = w.WriteString("220 relay.test ESMTP ready\r\n")
+				_ = w.Flush()
+				for {
+					line, err := r.ReadString('\n')
+					if err != nil {
+						return
+					}
+					up := strings.ToUpper(strings.TrimRight(line, "\r\n"))
+					switch {
+					case strings.HasPrefix(up, "STARTTLS"):
+						_, _ = w.WriteString("220 2.0.0 ready to start TLS\r\n")
+						_ = w.Flush()
+						tlsConn := tls.Server(conn, tlsCfg)
+						if err := tlsConn.Handshake(); err != nil {
+							return
+						}
+						conn = tlsConn
+						r = bufio.NewReader(conn)
+						w = bufio.NewWriter(conn)
+					case strings.HasPrefix(up, "EHLO"), strings.HasPrefix(up, "HELO"):
+						_, _ = w.WriteString("250-relay.test\r\n250-STARTTLS\r\n250 8BITMIME\r\n")
+						_ = w.Flush()
+					case strings.HasPrefix(up, "AUTH PLAIN"):
+						_, _ = w.WriteString("235 2.0.0 ok\r\n")
+						_ = w.Flush()
+					case strings.HasPrefix(up, "DATA"):
+						_, _ = w.WriteString("354 go ahead\r\n")
+						_ = w.Flush()
+						for {
+							dl, err := r.ReadString('\n')
+							if err != nil {
+								return
+							}
+							if strings.TrimRight(dl, "\r\n") == "." {
+								break
+							}
+						}
+						_, _ = w.WriteString("250 2.0.0 queued\r\n")
+						_ = w.Flush()
+					case strings.HasPrefix(up, "QUIT"):
+						_, _ = w.WriteString("221 bye\r\n")
+						_ = w.Flush()
+						return
+					default:
+						_, _ = w.WriteString("250 ok\r\n")
+						_ = w.Flush()
+					}
+				}
+			}()
+		}
+	}()
+
+	addr = ln.Addr().String()
+	return addr, func() { ln.Close() }
+}
+
+// makeSelfSignedCertPEM 生成一对自签证书（CN=relay.test）。
+func makeSelfSignedCertPEM(t *testing.T) (certPEM, keyPEM []byte) {
+	t.Helper()
+	key, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		t.Fatalf("generate key: %v", err)
+	}
+	tmpl := &x509.Certificate{
+		SerialNumber: big.NewInt(1),
+		Subject:      pkix.Name{CommonName: "relay.test"},
+		NotBefore:    time.Now().Add(-time.Hour),
+		NotAfter:     time.Now().Add(24 * time.Hour),
+		DNSNames:     []string{"relay.test"},
+		KeyUsage:     x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
+		ExtKeyUsage:  []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+	}
+	der, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, &key.PublicKey, key)
+	if err != nil {
+		t.Fatalf("create certificate: %v", err)
+	}
+	certPEM = pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: der})
+	keyPEM = pem.EncodeToMemory(&pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(key)})
+	return certPEM, keyPEM
+}
+
+// TestMailerRelayRejectsUntrustedCert 中继使用自签证书时默认必须拒绝
+// （证书验证开启，防止凭据被中间人截获）。
+func TestMailerRelayRejectsUntrustedCert(t *testing.T) {
+	addr, cleanup := startTLSSMTPServer(t)
+	defer cleanup()
+
+	m := NewMailer("mail.lmve.net", 5*time.Second)
+	m.Relay = &RelayConfig{
+		Host:        "127.0.0.1",
+		Port:        mustPort(t, addr),
+		Username:    "relay-user",
+		Password:    "relay-pass",
+		TLSInsecure: false,
+	}
+
+	input := []byte("From: a@lmve.net\r\nTo: b@bogus-domain.invalid\r\nSubject: relay\r\n\r\nbody\r\n")
+	_, err := m.Deliver("a@lmve.net", "b@bogus-domain.invalid", input)
+	if err == nil {
+		t.Fatal("relay with untrusted self-signed cert should be rejected")
+	}
+	if !strings.Contains(err.Error(), "certificate") {
+		t.Fatalf("expected certificate verification error, got: %v", err)
+	}
+}
+
+// TestMailerRelayInsecureSkipsVerification 显式开启 relay_tls_insecure
+// 后，自签证书的中继可以完成 TLS 握手并进入 SMTP 会话。
+func TestMailerRelayInsecureSkipsVerification(t *testing.T) {
+	addr, cleanup := startTLSSMTPServer(t)
+	defer cleanup()
+
+	m := NewMailer("mail.lmve.net", 5*time.Second)
+	m.Relay = &RelayConfig{
+		Host:        "127.0.0.1",
+		Port:        mustPort(t, addr),
+		Username:    "relay-user",
+		Password:    "relay-pass",
+		TLSInsecure: true,
+	}
+
+	input := []byte("From: a@lmve.net\r\nTo: b@bogus-domain.invalid\r\nSubject: relay\r\n\r\nbody\r\n")
+	resp, err := m.Deliver("a@lmve.net", "b@bogus-domain.invalid", input)
+	if err != nil {
+		t.Fatalf("relay with TLSInsecure should proceed: %v", err)
+	}
+	if !strings.HasPrefix(resp, "250") {
+		t.Fatalf("unexpected response: %q", resp)
+	}
+}
+
+func mustPort(t *testing.T, addr string) int {
+	t.Helper()
+	_, portStr, err := net.SplitHostPort(addr)
+	if err != nil {
+		t.Fatalf("split %q: %v", addr, err)
+	}
+	port, err := strconv.Atoi(portStr)
+	if err != nil {
+		t.Fatalf("port %q: %v", portStr, err)
+	}
+	return port
+}
@@ -64,11 +64,12 @@ func NewManager(cfg config.OutboundConfig, hostname string, stores *store.Stores

 	if cfg.RelayHost != "" {
 		m.mailer.Relay = &RelayConfig{
-			Host:     cfg.RelayHost,
-			Port:     cfg.RelayPort,
-			Username: cfg.RelayUser,
-			Password: cfg.RelayPassword,
-			StartTLS: cfg.RelayStartTLS,
+			Host:        cfg.RelayHost,
+			Port:        cfg.RelayPort,
+			Username:    cfg.RelayUser,
+			Password:    cfg.RelayPassword,
+			StartTLS:    cfg.RelayStartTLS,
+			TLSInsecure: cfg.RelayTLSInsecure,
 		}
 		log.Printf("outbound: using smarthost relay %s:%d", cfg.RelayHost, cfg.RelayPort)
 	}
@@ -22,14 +22,15 @@ type POP3Server struct {
 	listener  net.Listener
 	stores    *store.Stores
 	cfg       config.POP3Config
+	banCfg    config.BanConfig
 	tlsLoader *tlsutil.Loader
 	wg        sync.WaitGroup
 }

 // NewPOP3Server creates a new POP3 server instance. tlsLoader may be nil
 // when TLS is not configured.
-func NewPOP3Server(cfg config.POP3Config, stores *store.Stores, tlsLoader *tlsutil.Loader) *POP3Server {
-	return &POP3Server{stores: stores, cfg: cfg, tlsLoader: tlsLoader}
+func NewPOP3Server(cfg config.POP3Config, stores *store.Stores, tlsLoader *tlsutil.Loader, banCfg config.BanConfig) *POP3Server {
+	return &POP3Server{stores: stores, cfg: cfg, banCfg: banCfg, tlsLoader: tlsLoader}
 }

 func (s *POP3Server) tlsConfig() (*tls.Config, error) {
@@ -107,6 +108,14 @@ func (s *POP3Server) handleConn(conn net.Conn) {
 	defer conn.Close()
 	conn.SetDeadline(time.Now().Add(10 * time.Minute))

+	clientIP := store.ClientIPFromAddr(conn.RemoteAddr())
+
+	// 已封禁 IP 直接拒绝（防协议层暴力破解）
+	if banned, _ := s.stores.Bans.IsBanned(clientIP); banned {
+		sendResponse(conn, "-ERR access denied")
+		return
+	}
+
 	reader := bufio.NewReader(conn)
 	var user *db.User
 	var messages []pop3Message
@@ -272,8 +281,12 @@ func (s *POP3Server) handlePASS(conn net.Conn, password string, user *db.User) (
 		return nil, nil, nil
 	}

+	clientIP := store.ClientIPFromAddr(conn.RemoteAddr())
+
 	authUser, err := s.stores.Users.Authenticate(user.Username, password)
 	if err != nil {
+		// 认证失败计数，达到阈值封禁（与 Web 登录共用 ban_entries）
+		s.stores.RecordAuthFailure(clientIP, s.banCfg.MaxFailAttempts, s.banCfg.BanDurationMin)
 		sendResponse(conn, "-ERR authentication failed")
 		return nil, nil, nil
 	}
@@ -36,13 +36,14 @@ type SMTPServer struct {
 	storage   *storage.AttachmentStorage
 	outbound  *outbound.Manager
 	cfg       config.SMTPConfig
+	banCfg    config.BanConfig
 	tlsLoader *tlsutil.Loader
 }

 // NewSMTPServer creates a new SMTP server instance. tlsLoader may be nil
 // when TLS is not configured.
-func NewSMTPServer(cfg config.SMTPConfig, stores *store.Stores, attStorage *storage.AttachmentStorage, ob *outbound.Manager, tlsLoader *tlsutil.Loader) *SMTPServer {
-	return &SMTPServer{stores: stores, storage: attStorage, outbound: ob, cfg: cfg, tlsLoader: tlsLoader}
+func NewSMTPServer(cfg config.SMTPConfig, stores *store.Stores, attStorage *storage.AttachmentStorage, ob *outbound.Manager, tlsLoader *tlsutil.Loader, banCfg config.BanConfig) *SMTPServer {
+	return &SMTPServer{stores: stores, storage: attStorage, outbound: ob, cfg: cfg, banCfg: banCfg, tlsLoader: tlsLoader}
 }

 func (s *SMTPServer) tlsConfig() (*tls.Config, error) {
@@ -108,9 +109,10 @@ type smtpBackend struct {
 // NewSession creates a new SMTP session for the incoming connection.
 func (be *smtpBackend) NewSession(c *smtp.Conn) (smtp.Session, error) {
 	return &smtpSession{
-		backend: be,
-		mode:    be.mode,
-		rcpts:   make([]string, 0),
+		backend:   be,
+		mode:      be.mode,
+		rcpts:     make([]string, 0),
+		clientIP:  store.ClientIPFromAddr(c.Conn().RemoteAddr()),
 	}, nil
 }

@@ -126,6 +128,7 @@ type smtpSession struct {
 	userID        uint
 	email         string
 	user          *db.User
+	clientIP      string
 }

 // AuthMechanisms returns supported SMTP AUTH mechanisms.
@@ -139,8 +142,19 @@ func (s *smtpSession) Auth(mech string) (sasl.Server, error) {
 		return nil, smtp.ErrAuthUnknownMechanism
 	}
 	return sasl.NewPlainServer(func(identity, username, password string) error {
+		// 已封禁 IP 一律拒绝认证（防协议层暴力破解）
+		if banned, _ := s.backend.server.stores.Bans.IsBanned(s.clientIP); banned {
+			return smtp.ErrAuthFailed
+		}
+
 		user, err := s.backend.server.stores.Users.Authenticate(username, password)
 		if err != nil {
+			// 认证失败计数，达到阈值封禁（与 Web 登录共用 ban_entries）
+			s.backend.server.stores.RecordAuthFailure(
+				s.clientIP,
+				s.backend.server.banCfg.MaxFailAttempts,
+				s.backend.server.banCfg.BanDurationMin,
+			)
 			return smtp.ErrAuthFailed
 		}

@@ -4,11 +4,16 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strings"

 	"github.com/google/uuid"
 )

+// savedFileRe 匹配 Save 生成的文件名：UUID（小写十六进制）+ 可选白名单扩展名。
+// 只允许这种格式的路径进入文件系统，杜绝路径遍历（../）、绝对路径等。
+var savedFileRe = regexp.MustCompile(`^[a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{12}(\.[A-Za-z0-9._-]{1,32})?$`)
+
 // AttachmentStorage handles file operations for email attachments on disk.
 type AttachmentStorage struct {
 	baseDir string // cfg.Storage.AttachDir
@@ -19,6 +24,24 @@ func NewAttachmentStorage(baseDir string) *AttachmentStorage {
 	return &AttachmentStorage{baseDir: baseDir}
 }

+// safeExt 提取并白名单化文件扩展名：只保留字母数字与 ._-，最长 32 字符。
+// 非法字符（含 CR/LF、路径分隔符）直接丢弃扩展名。
+func safeExt(filename string) string {
+	ext := filepath.Ext(filename)
+	if len(ext) > 33 {
+		return ""
+	}
+	for _, r := range ext {
+		switch {
+		case r >= 'a' && r <= 'z', r >= 'A' && r <= 'Z', r >= '0' && r <= '9':
+		case r == '.', r == '_', r == '-':
+		default:
+			return ""
+		}
+	}
+	return ext
+}
+
 // Save writes attachment data to disk and returns the relative file path.
 // The filename is generated as {uuid}{ext} to avoid collisions.
 func (s *AttachmentStorage) Save(filename string, data []byte) (string, error) {
@@ -27,8 +50,8 @@ func (s *AttachmentStorage) Save(filename string, data []byte) (string, error) {
 		return "", fmt.Errorf("创建附件目录失败: %w", err)
 	}

-	// Generate a unique filename with the original extension
-	ext := filepath.Ext(filename)
+	// Generate a unique filename with a sanitized extension
+	ext := safeExt(filename)
 	uniqueName := uuid.New().String() + ext

 	fullPath := filepath.Join(s.baseDir, uniqueName)
@@ -41,7 +64,10 @@ func (s *AttachmentStorage) Save(filename string, data []byte) (string, error) {

 // Read reads attachment data from disk given a relative path.
 func (s *AttachmentStorage) Read(relPath string) ([]byte, error) {
-	fullPath := s.FullPath(relPath)
+	fullPath, err := s.FullPath(relPath)
+	if err != nil {
+		return nil, err
+	}
 	data, err := os.ReadFile(fullPath)
 	if err != nil {
 		return nil, fmt.Errorf("读取附件文件失败: %w", err)
@@ -51,19 +77,29 @@ func (s *AttachmentStorage) Read(relPath string) ([]byte, error) {

 // Delete removes an attachment file from disk given a relative path.
 func (s *AttachmentStorage) Delete(relPath string) error {
-	fullPath := s.FullPath(relPath)
+	fullPath, err := s.FullPath(relPath)
+	if err != nil {
+		return err
+	}
 	if err := os.Remove(fullPath); err != nil && !os.IsNotExist(err) {
 		return fmt.Errorf("删除附件文件失败: %w", err)
 	}
 	return nil
 }

-// FullPath returns the absolute path for a given relative path.
-func (s *AttachmentStorage) FullPath(relPath string) string {
-	// Prevent directory traversal attacks
-	cleanRel := filepath.Clean(relPath)
-	if strings.HasPrefix(cleanRel, "..") {
-		cleanRel = strings.TrimPrefix(cleanRel, "../")
+// FullPath returns the absolute path for a relative path produced by Save.
+// Paths that do not match the saved-file format (traversal attempts,
+// absolute paths, unrelated names) are rejected with an error so they can
+// never escape baseDir.
+func (s *AttachmentStorage) FullPath(relPath string) (string, error) {
+	if !savedFileRe.MatchString(relPath) {
+		return "", fmt.Errorf("非法的附件路径: %q", relPath)
 	}
-	return filepath.Join(s.baseDir, cleanRel)
+
+	// 兜底校验：解析后的路径必须仍在 baseDir 内
+	fullPath := filepath.Join(s.baseDir, relPath)
+	if !strings.HasPrefix(fullPath, filepath.Clean(s.baseDir)+string(os.PathSeparator)) {
+		return "", fmt.Errorf("附件路径越界: %q", relPath)
+	}
+	return fullPath, nil
 }
@@ -0,0 +1,97 @@
+package storage
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/google/uuid"
+)
+
+// TestFullPathRejectsTraversal 验证路径遍历/绝对路径等恶意输入被拒绝。
+func TestFullPathRejectsTraversal(t *testing.T) {
+	s := NewAttachmentStorage(filepath.Join(t.TempDir(), "attachments"))
+
+	valid := uuid.New().String() + ".pdf"
+	bad := []string{
+		"../secret.txt",
+		"../../etc/passwd",
+		"..",
+		"....//x",
+		"/etc/passwd",
+		"a/../b.txt",
+		"sub/file.png",
+		"",
+		".", "..\\..\\x", // windows style
+		"00000000-0000-0000-0000-000000000000.exe\r\nBcc: x@y.com",
+		"garbage",
+		"00000000-0000-0000-0000-000000000000.%2e%2e",
+	}
+	for _, p := range bad {
+		if _, err := s.FullPath(p); err == nil {
+			t.Errorf("FullPath(%q) should be rejected", p)
+		}
+	}
+
+	// 合法文件名必须通过
+	full, err := s.FullPath(valid)
+	if err != nil {
+		t.Fatalf("FullPath(%q) rejected: %v", valid, err)
+	}
+	if !strings.HasPrefix(full, s.baseDir+string(os.PathSeparator)) {
+		t.Fatalf("FullPath(%q) = %q escapes baseDir", valid, full)
+	}
+}
+
+// TestSaveSanitizesExtension 验证恶意扩展名不会进入文件名。
+func TestSaveSanitizesExtension(t *testing.T) {
+	s := NewAttachmentStorage(filepath.Join(t.TempDir(), "attachments"))
+
+	// 换行/路径分隔符等非法字符的扩展名应被丢弃
+	rel, err := s.Save("evil.pdf\r\nBcc: x@y.com", []byte("data"))
+	if err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+	if strings.ContainsAny(rel, "\r\n/\\") {
+		t.Fatalf("saved name contains dangerous chars: %q", rel)
+	}
+	if !savedFileRe.MatchString(rel) {
+		t.Fatalf("saved name %q does not match allowed pattern", rel)
+	}
+	// 后续 Read 应能按返回的路径读取
+	if _, err := s.Read(rel); err != nil {
+		t.Fatalf("Read after Save: %v", err)
+	}
+
+	// 正常扩展名保留
+	rel2, err := s.Save("report.pdf", []byte("data"))
+	if err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+	if !strings.HasSuffix(rel2, ".pdf") {
+		t.Fatalf("extension lost: %q", rel2)
+	}
+}
+
+// TestReadDeleteRoundTrip 正常读写删流程。
+func TestReadDeleteRoundTrip(t *testing.T) {
+	dir := t.TempDir()
+	s := NewAttachmentStorage(filepath.Join(dir, "attachments"))
+
+	rel, err := s.Save("a.txt", []byte("hello"))
+	if err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+	data, err := s.Read(rel)
+	if err != nil || string(data) != "hello" {
+		t.Fatalf("Read = %q, %v", data, err)
+	}
+	if err := s.Delete(rel); err != nil {
+		t.Fatalf("Delete: %v", err)
+	}
+	// 删除后路径仍然合法（删除不存在文件不算错误）
+	if err := s.Delete(rel); err != nil {
+		t.Fatalf("Delete again: %v", err)
+	}
+}
@@ -0,0 +1,43 @@
+package store
+
+import (
+	"fmt"
+	"net"
+	"time"
+
+	"mail_go/internal/db"
+)
+
+// ClientIPFromAddr 从 net.Addr 提取客户端 IP 字符串（去掉端口）。
+// 解析失败返回空字符串，调用方应据此跳过封禁逻辑（不误封）。
+func ClientIPFromAddr(addr net.Addr) string {
+	if addr == nil {
+		return ""
+	}
+	host, _, err := net.SplitHostPort(addr.String())
+	if err != nil {
+		return addr.String()
+	}
+	return host
+}
+
+// RecordAuthFailure 记录一次协议层（SMTP/IMAP/POP3）认证失败：
+// 失败计数累加，达到 maxFail 阈值时封禁该 IP（封禁时长 minutes 分钟）。
+// 返回 (是否触发封禁, 当前失败计数)。Web 登录的封禁逻辑在
+// handlers.AuthHandler 中，与这里独立。
+func (s *Stores) RecordAuthFailure(ip string, maxFail int, minutes int) (banned bool, failCount int) {
+	if ip == "" || maxFail <= 0 {
+		return false, 0
+	}
+	failCount, _ = s.Bans.IncrementFail(ip)
+	if failCount >= maxFail {
+		_ = s.Bans.Create(&db.BanEntry{
+			IPAddress: ip,
+			Reason:    fmt.Sprintf("邮件协议认证失败次数过多 (%d次)", failCount),
+			FailCount: failCount,
+			ExpiresAt: time.Now().Add(time.Duration(minutes) * time.Minute),
+		})
+		return true, failCount
+	}
+	return false, failCount
+}
@@ -0,0 +1,113 @@
+package store
+
+import (
+	"net"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"mail_go/internal/db"
+
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+)
+
+func newTestStores(t *testing.T) *Stores {
+	t.Helper()
+	gdb, err := gorm.Open(sqlite.Open(filepath.Join(t.TempDir(), "test.db")), &gorm.Config{})
+	if err != nil {
+		t.Fatalf("open sqlite: %v", err)
+	}
+	if err := gdb.AutoMigrate(&db.User{}, &db.Domain{}, &db.Message{}, &db.Attachment{}, &db.BanEntry{}, &db.OutboundMessage{}); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+	return NewStores(gdb)
+}
+
+// TestRecordAuthFailureBansAfterThreshold 验证连续认证失败达到阈值后封禁。
+func TestRecordAuthFailureBansAfterThreshold(t *testing.T) {
+	s := newTestStores(t)
+	const ip = "203.0.113.10"
+	const maxFail = 3
+
+	// 前两次失败不封禁
+	for i := 1; i < maxFail; i++ {
+		banned, count := s.RecordAuthFailure(ip, maxFail, 30)
+		if banned {
+			t.Fatalf("attempt %d should not be banned yet", i)
+		}
+		if count != i {
+			t.Fatalf("attempt %d: fail count = %d, want %d", i, count, i)
+		}
+	}
+
+	// 第三次失败触发封禁
+	banned, count := s.RecordAuthFailure(ip, maxFail, 30)
+	if !banned {
+		t.Fatal("attempt reaching threshold should ban the IP")
+	}
+	if count != maxFail {
+		t.Fatalf("fail count = %d, want %d", count, maxFail)
+	}
+
+	// IP 现在处于封禁状态
+	banned, entry := s.Bans.IsBanned(ip)
+	if !banned {
+		t.Fatal("IP should be banned")
+	}
+	if entry.ExpiresAt.Before(time.Now().Add(29 * time.Minute)) {
+		t.Fatalf("ban expiry too short: %v", entry.ExpiresAt)
+	}
+}
+
+// TestRecordAuthFailureEmptyIPSafe 空 IP 不应产生副作用。
+func TestRecordAuthFailureEmptyIPSafe(t *testing.T) {
+	s := newTestStores(t)
+	banned, count := s.RecordAuthFailure("", 3, 30)
+	if banned || count != 0 {
+		t.Fatalf("empty IP must be a no-op: banned=%v count=%d", banned, count)
+	}
+	if _, err := s.Bans.GetByIP(""); err == nil {
+		t.Fatal("empty IP should not be recorded")
+	}
+}
+
+// TestRecordAuthFailureWebAndProtocolShared 协议层与 Web 层共用封禁记录。
+func TestRecordAuthFailureWebAndProtocolShared(t *testing.T) {
+	s := newTestStores(t)
+	const ip = "198.51.100.20"
+
+	// Web 层已封禁（直接建记录模拟），协议层认证必须被拒绝
+	s.Bans.Create(&db.BanEntry{
+		IPAddress: ip,
+		Reason:    "web login failures",
+		FailCount: 5,
+		ExpiresAt: time.Now().Add(30 * time.Minute),
+	})
+	if banned, _ := s.Bans.IsBanned(ip); !banned {
+		t.Fatal("IP should be banned for both web and protocol auth")
+	}
+}
+
+func TestClientIPFromAddr(t *testing.T) {
+	cases := []struct {
+		addr net.Addr
+		want string
+	}{
+		{nil, ""},
+		{addrMock("203.0.113.5:12345"), "203.0.113.5"},
+		{addrMock("[2001:db8::1]:993"), "2001:db8::1"},
+		{addrMock("bad-format"), "bad-format"},
+	}
+	for _, tc := range cases {
+		if got := ClientIPFromAddr(tc.addr); got != tc.want {
+			t.Errorf("ClientIPFromAddr(%v) = %q, want %q", tc.addr, got, tc.want)
+		}
+	}
+}
+
+// addrMock 实现 net.Addr 的最小桩。
+type addrMock string
+
+func (a addrMock) Network() string { return "tcp" }
+func (a addrMock) String() string  { return string(a) }
@@ -124,9 +124,14 @@ func (s *userStoreGorm) UpdateUsedBytes(id uint, delta int64) error {
 		Update("used_bytes", gorm.Expr("used_bytes + ?", delta)).Error
 }

-// UpdatePassword updates the password hash for a user.
+// UpdatePassword updates the password hash for a user and clears the
+// must-change-password flag (the user has now set their own password).
 func (s *userStoreGorm) UpdatePassword(userID uint, hashedPassword string) error {
-	return s.db.Model(&db.User{}).Where("id = ?", userID).Update("password_hash", hashedPassword).Error
+	return s.db.Model(&db.User{}).Where("id = ?", userID).
+		Updates(map[string]interface{}{
+			"password_hash":         hashedPassword,
+			"must_change_password": false,
+		}).Error
 }

 // ListAll retrieves a paginated list of all users across all domains.
@@ -696,6 +696,8 @@ func (h *AdminHandler) UpdateUser(c *gin.Context) {
 			return
 		}
 		user.PasswordHash = string(hashedPassword)
+		// 管理员重置的密码必须由用户本人修改后才能正常使用
+		user.MustChangePassword = true
 	}

 	if err := h.stores.Users.Update(user); err != nil {
@@ -860,7 +862,7 @@ func (h *AdminHandler) AdminDownloadAttachment(c *gin.Context) {
 		return
 	}

-	c.Header("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", att.FileName))
+	c.Header("Content-Disposition", formatContentDisposition(att.FileName))
 	c.Data(http.StatusOK, att.ContentType, data)
 }

@@ -1,6 +1,9 @@
 package handlers

 import (
+	"crypto/rand"
+	"crypto/subtle"
+	"encoding/hex"
 	"fmt"
 	"log"
 	"net/http"
@@ -167,7 +170,7 @@ func (h *AuthHandler) LDAPLogin(c *gin.Context) {

 		remaining := h.banCfg.MaxFailAttempts - failCount
 		c.HTML(200, "login", gin.H{
-			"error":          fmt.Sprintf("LDAP 认证失败，还剩 %d 次尝试机会: %v", remaining, err),
+			"error":          fmt.Sprintf("LDAP 认证失败，还剩 %d 次尝试机会", remaining),
 			"oauth2Enabled":  h.authCfg.OAuth2Enabled,
 			"ldapEnabled":    h.authCfg.LDAPEnabled,
 			"oauth2Provider": h.authCfg.OAuth2Provider,
@@ -179,7 +182,7 @@ func (h *AuthHandler) LDAPLogin(c *gin.Context) {
 	user, err := h.stores.Users.GetByEmail(email)
 	if err != nil {
 		c.HTML(200, "login", gin.H{
-			"error":          fmt.Sprintf("LDAP 用户 %s 在系统中不存在", email),
+			"error":          "LDAP 账号未接入本系统，请联系管理员",
 			"oauth2Enabled":  h.authCfg.OAuth2Enabled,
 			"ldapEnabled":    h.authCfg.LDAPEnabled,
 			"oauth2Provider": h.authCfg.OAuth2Provider,
@@ -218,6 +221,36 @@ func (h *AuthHandler) LDAPLogin(c *gin.Context) {
 	c.Redirect(302, "/inbox")
 }

+// OAuth2 state cookie 配置。state 用于防止登录 CSRF / 授权码注入：
+// 发起授权时下发随机值，回调时必须原样带回。
+//
+// 注意 state 不能放进主会话 cookie：主会话是 SameSite=Strict，
+// OAuth2 回调是从 IdP 发起的跨站顶级导航，浏览器不会携带 Strict
+// cookie，因此使用独立的短期 SameSite=Lax cookie。
+const (
+	oauth2StateCookie  = "mail_go_oauth2_state"
+	oauth2StateMaxAge  = 600 // 秒，10 分钟内完成授权流程
+	oauth2StateRandLen = 16  // 随机字节数（hex 编码后 32 字符）
+)
+
+// randomOAuth2State generates a hex-encoded cryptographically random state.
+func randomOAuth2State() (string, error) {
+	buf := make([]byte, oauth2StateRandLen)
+	if _, err := rand.Read(buf); err != nil {
+		return "", fmt.Errorf("生成 OAuth2 state 失败: %w", err)
+	}
+	return hex.EncodeToString(buf), nil
+}
+
+// oauth2LoginVars 是登录模板所需的公共变量。
+func (h *AuthHandler) oauth2LoginVars() gin.H {
+	return gin.H{
+		"oauth2Enabled":  h.authCfg.OAuth2Enabled,
+		"ldapEnabled":    h.authCfg.LDAPEnabled,
+		"oauth2Provider": h.authCfg.OAuth2Provider,
+	}
+}
+
 // OAuth2Start redirects to the OAuth2 provider's authorization page.
 func (h *AuthHandler) OAuth2Start(c *gin.Context) {
 	if !h.authCfg.OAuth2Enabled {
@@ -226,8 +259,13 @@ func (h *AuthHandler) OAuth2Start(c *gin.Context) {
 	}

 	provider := auth.NewOAuth2Provider(h.authCfg)
-	// Use a simple state for CSRF protection (in production, use a random token)
-	state := "mailgo_oauth2_state"
+	state, err := randomOAuth2State()
+	if err != nil {
+		log.Printf("生成 OAuth2 state 失败: %v", err)
+		c.String(http.StatusInternalServerError, "OAuth2 登录暂不可用，请稍后重试")
+		return
+	}
+	c.SetCookie(oauth2StateCookie, state, oauth2StateMaxAge, "/auth/oauth2", "", true, true)
 	c.Redirect(http.StatusFound, provider.GetAuthURL(state))
 }

@@ -238,6 +276,22 @@ func (h *AuthHandler) OAuth2Callback(c *gin.Context) {
 		return
 	}

+	// 校验 state：必须与发起授权时下发的随机值一致（常量时间比较）。
+	// 缺失或不匹配视为登录 CSRF / 授权码注入，直接拒绝。
+	cookieState, cookieErr := c.Cookie(oauth2StateCookie)
+	reqState := c.Query("state")
+	if cookieErr != nil || reqState == "" ||
+		subtle.ConstantTimeCompare([]byte(cookieState), []byte(reqState)) != 1 {
+		c.HTML(http.StatusForbidden, "login", func() gin.H {
+			v := h.oauth2LoginVars()
+			v["error"] = "OAuth2 state 校验失败，请重新发起登录"
+			return v
+		}())
+		return
+	}
+	// state 一次性使用：无论后续成败都立即失效
+	c.SetCookie(oauth2StateCookie, "", -1, "/auth/oauth2", "", true, true)
+
 	code := c.Query("code")
 	if code == "" {
 		c.HTML(200, "login", gin.H{
@@ -254,7 +308,7 @@ func (h *AuthHandler) OAuth2Callback(c *gin.Context) {
 	if err != nil {
 		log.Printf("OAuth2 回调失败: %v", err)
 		c.HTML(200, "login", gin.H{
-			"error":          fmt.Sprintf("OAuth2 认证失败: %v", err),
+			"error":          "OAuth2 认证失败，请重试或联系管理员",
 			"oauth2Enabled":  h.authCfg.OAuth2Enabled,
 			"ldapEnabled":    h.authCfg.LDAPEnabled,
 			"oauth2Provider": h.authCfg.OAuth2Provider,
@@ -266,7 +320,7 @@ func (h *AuthHandler) OAuth2Callback(c *gin.Context) {
 	user, err := h.stores.Users.GetByEmail(email)
 	if err != nil {
 		c.HTML(200, "login", gin.H{
-			"error":          fmt.Sprintf("OAuth2 用户 %s 在系统中不存在", email),
+			"error":          "OAuth2 账号未接入本系统，请联系管理员",
 			"oauth2Enabled":  h.authCfg.OAuth2Enabled,
 			"ldapEnabled":    h.authCfg.LDAPEnabled,
 			"oauth2Provider": h.authCfg.OAuth2Provider,
@@ -4,6 +4,7 @@ import (
 	"encoding/base64"
 	"fmt"
 	"io"
+	"mime"
 	"net/http"
 	"path/filepath"
 	"strconv"
@@ -264,62 +265,8 @@ func (h *MailHandler) DoSend(c *gin.Context) {

 	// Build the email content
 	fromAddr := fmt.Sprintf("%s@%s", currentUser.Username, currentUser.Domain.Name)
+	messageID, rawMessage := buildOutgoingMessage(fromAddr, to, cc, subject, body, htmlBody, attachments)
 	now := time.Now()
-	messageID := fmt.Sprintf("<%s@mail_go>", uuid.New().String())
-
-	// Construct the raw email message
-	var sb strings.Builder
-	sb.WriteString(fmt.Sprintf("From: %s\r\n", fromAddr))
-	sb.WriteString(fmt.Sprintf("To: %s\r\n", to))
-	if cc != "" {
-		sb.WriteString(fmt.Sprintf("Cc: %s\r\n", cc))
-	}
-	sb.WriteString(fmt.Sprintf("Subject: %s\r\n", subject))
-	sb.WriteString(fmt.Sprintf("Message-ID: %s\r\n", messageID))
-	sb.WriteString(fmt.Sprintf("Date: %s\r\n", now.Format(time.RFC1123Z)))
-	sb.WriteString("MIME-Version: 1.0\r\n")
-
-	// Attachments are wrapped in an outer multipart/mixed container.
-	outerBoundary := ""
-	hasAttachments := len(attachments) > 0
-	if hasAttachments {
-		outerBoundary = fmt.Sprintf("----=_Mixed_%s", uuid.New().String())
-		sb.WriteString(fmt.Sprintf("Content-Type: multipart/mixed; boundary=\"%s\"\r\n", outerBoundary))
-		sb.WriteString("\r\n")
-		sb.WriteString(fmt.Sprintf("--%s\r\n", outerBoundary))
-	}
-
-	// Build message body with multipart/alternative if HTML is present
-	if htmlBody != "" {
-		boundary := fmt.Sprintf("----=_Part_%s", uuid.New().String())
-		sb.WriteString(fmt.Sprintf("Content-Type: multipart/alternative; boundary=\"%s\"\r\n", boundary))
-		sb.WriteString("\r\n")
-		sb.WriteString(fmt.Sprintf("--%s\r\n", boundary))
-		sb.WriteString("Content-Type: text/plain; charset=utf-8\r\n\r\n")
-		sb.WriteString(body)
-		sb.WriteString(fmt.Sprintf("\r\n--%s\r\n", boundary))
-		sb.WriteString("Content-Type: text/html; charset=utf-8\r\n\r\n")
-		sb.WriteString(htmlBody)
-		sb.WriteString(fmt.Sprintf("\r\n--%s--\r\n", boundary))
-	} else {
-		sb.WriteString("Content-Type: text/plain; charset=utf-8\r\n")
-		sb.WriteString("\r\n")
-		sb.WriteString(body)
-		sb.WriteString("\r\n")
-	}
-
-	// Append attachment parts to the multipart/mixed container.
-	for _, att := range attachments {
-		sb.WriteString(fmt.Sprintf("--%s\r\n", outerBoundary))
-		sb.WriteString(fmt.Sprintf("Content-Type: %s; name=\"%s\"\r\n", att.contentType, att.filename))
-		sb.WriteString("Content-Transfer-Encoding: base64\r\n")
-		sb.WriteString(fmt.Sprintf("Content-Disposition: attachment; filename=\"%s\"\r\n\r\n", att.filename))
-		sb.WriteString(base64LineWrap(att.data))
-		sb.WriteString("\r\n")
-	}
-	if hasAttachments {
-		sb.WriteString(fmt.Sprintf("--%s--\r\n", outerBoundary))
-	}

 	allRecipients := append(parseAddressInput(to), parseAddressInput(cc)...)
 	localUsers := make([]*db.User, 0, len(allRecipients))
@@ -367,7 +314,7 @@ func (h *MailHandler) DoSend(c *gin.Context) {
 			return
 		}
 		for _, rcpt := range externalRecipients {
-			if _, err := ob.Enqueue(currentUser, fromAddr, rcpt, []byte(sb.String())); err != nil {
+			if _, err := ob.Enqueue(currentUser, fromAddr, rcpt, []byte(rawMessage)); err != nil {
 				c.HTML(http.StatusBadRequest, "compose", gin.H{
 					"currentUser":  currentUser,
 					"activeFolder": "compose",
@@ -395,7 +342,7 @@ func (h *MailHandler) DoSend(c *gin.Context) {
 			Subject:   subject,
 			TextBody:  body,
 			HtmlBody:  htmlBody,
-			RawData:   sb.String(),
+			RawData:   rawMessage,
 			Date:      now,
 			IsRead:    false,
 		}
@@ -426,7 +373,7 @@ func (h *MailHandler) DoSend(c *gin.Context) {
 		Subject:   subject,
 		TextBody:  body,
 		HtmlBody:  htmlBody,
-		RawData:   sb.String(),
+		RawData:   rawMessage,
 		Date:      now,
 		IsRead:    true,
 	}
@@ -483,6 +430,94 @@ func parseAddressInput(input string) []string {
 	return addresses
 }

+// sanitizeHeaderField removes CR/LF/NUL from a value destined for an RFC 5322
+// message header, preventing header injection (e.g. smuggling a Bcc or
+// Reply-To header via a crafted subject or address list).
+func sanitizeHeaderField(s string) string {
+	s = strings.ReplaceAll(s, "\r", "")
+	s = strings.ReplaceAll(s, "\n", "")
+	s = strings.ReplaceAll(s, "\x00", "")
+	return s
+}
+
+// encodeSubject prepares a subject for safe inclusion as a message header:
+// header injection characters are stripped and non-ASCII content is encoded
+// per RFC 2047.
+func encodeSubject(s string) string {
+	return mime.QEncoding.Encode("utf-8", sanitizeHeaderField(s))
+}
+
+// formatContentDisposition builds a Content-Disposition header value for the
+// given filename, quoting/encoding it per RFC 2183/2231 (also neutralizes
+// CR/LF injection through crafted filenames).
+func formatContentDisposition(filename string) string {
+	return mime.FormatMediaType("attachment", map[string]string{"filename": filename})
+}
+
+// buildOutgoingMessage constructs the raw RFC 5322 message for the web
+// compose form and returns its Message-ID. All header values derived from
+// user input are sanitized to prevent CRLF header injection.
+func buildOutgoingMessage(from, to, cc, subject, body, htmlBody string, attachments []pendingAttachment) (messageID, raw string) {
+	now := time.Now()
+	messageID = fmt.Sprintf("<%s@mail_go>", uuid.New().String())
+
+	var sb strings.Builder
+	sb.WriteString(fmt.Sprintf("From: %s\r\n", sanitizeHeaderField(from)))
+	sb.WriteString(fmt.Sprintf("To: %s\r\n", sanitizeHeaderField(to)))
+	if cc != "" {
+		sb.WriteString(fmt.Sprintf("Cc: %s\r\n", sanitizeHeaderField(cc)))
+	}
+	sb.WriteString(fmt.Sprintf("Subject: %s\r\n", encodeSubject(subject)))
+	sb.WriteString(fmt.Sprintf("Message-ID: %s\r\n", messageID))
+	sb.WriteString(fmt.Sprintf("Date: %s\r\n", now.Format(time.RFC1123Z)))
+	sb.WriteString("MIME-Version: 1.0\r\n")
+
+	// Attachments are wrapped in an outer multipart/mixed container.
+	outerBoundary := ""
+	hasAttachments := len(attachments) > 0
+	if hasAttachments {
+		outerBoundary = fmt.Sprintf("----=_Mixed_%s", uuid.New().String())
+		sb.WriteString(fmt.Sprintf("Content-Type: multipart/mixed; boundary=\"%s\"\r\n", outerBoundary))
+		sb.WriteString("\r\n")
+		sb.WriteString(fmt.Sprintf("--%s\r\n", outerBoundary))
+	}
+
+	// Build message body with multipart/alternative if HTML is present
+	if htmlBody != "" {
+		boundary := fmt.Sprintf("----=_Part_%s", uuid.New().String())
+		sb.WriteString(fmt.Sprintf("Content-Type: multipart/alternative; boundary=\"%s\"\r\n", boundary))
+		sb.WriteString("\r\n")
+		sb.WriteString(fmt.Sprintf("--%s\r\n", boundary))
+		sb.WriteString("Content-Type: text/plain; charset=utf-8\r\n\r\n")
+		sb.WriteString(body)
+		sb.WriteString(fmt.Sprintf("\r\n--%s\r\n", boundary))
+		sb.WriteString("Content-Type: text/html; charset=utf-8\r\n\r\n")
+		sb.WriteString(htmlBody)
+		sb.WriteString(fmt.Sprintf("\r\n--%s--\r\n", boundary))
+	} else {
+		sb.WriteString("Content-Type: text/plain; charset=utf-8\r\n")
+		sb.WriteString("\r\n")
+		sb.WriteString(body)
+		sb.WriteString("\r\n")
+	}
+
+	// Append attachment parts to the multipart/mixed container.
+	for _, att := range attachments {
+		contentType := mime.FormatMediaType(att.contentType, map[string]string{"name": att.filename})
+		sb.WriteString(fmt.Sprintf("--%s\r\n", outerBoundary))
+		sb.WriteString(fmt.Sprintf("Content-Type: %s\r\n", contentType))
+		sb.WriteString("Content-Transfer-Encoding: base64\r\n")
+		sb.WriteString(fmt.Sprintf("Content-Disposition: %s\r\n\r\n", formatContentDisposition(att.filename)))
+		sb.WriteString(base64LineWrap(att.data))
+		sb.WriteString("\r\n")
+	}
+	if hasAttachments {
+		sb.WriteString(fmt.Sprintf("--%s--\r\n", outerBoundary))
+	}
+
+	return messageID, sb.String()
+}
+
 // mimeTypes maps common file extensions to MIME types.
 var mimeTypes = map[string]string{
 	".txt":  "text/plain",
@@ -623,7 +658,7 @@ func (h *MailHandler) DownloadAttachment(c *gin.Context) {
 		return
 	}

-	c.Header("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", att.FileName))
+	c.Header("Content-Disposition", formatContentDisposition(att.FileName))
 	c.Data(http.StatusOK, att.ContentType, data)
 }

@@ -688,6 +723,7 @@ func (h *MailHandler) Settings(c *gin.Context) {
 		"activeFolder": "settings",
 		"error":        "",
 		"success":      "",
+		"mustChange":   c.Query("force") == "1",
 		"inboxUnread":  inboxUnread,
 		"draftsTotal":  draftsTotal,
 		"sentTotal":    sentTotal,
@@ -0,0 +1,106 @@
+package handlers
+
+// P1 #4 回归测试：Web 写信的邮件头不可被 CRLF 注入。
+// 旧实现把 to/cc/subject/附件名原样拼进 MIME 头，攻击者可通过
+// subject 注入 Reply-To/Bcc 等任意头用于钓鱼。
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestSanitizeHeaderField(t *testing.T) {
+	cases := []struct {
+		in, want string
+	}{
+		{"normal value", "normal value"},
+		{"with\r\ninjected: header", "withinjected: header"},
+		{"lf\nonly", "lfonly"},
+		{"cr\ronly", "cronly"},
+		{"nul\x00byte", "nulbyte"},
+		{"mixed\r\n\x00all", "mixedall"},
+		{"中文主题", "中文主题"},
+	}
+	for _, tc := range cases {
+		if got := sanitizeHeaderField(tc.in); got != tc.want {
+			t.Errorf("sanitizeHeaderField(%q) = %q, want %q", tc.in, got, tc.want)
+		}
+	}
+}
+
+func TestBuildOutgoingMessageBlocksHeaderInjection(t *testing.T) {
+	_, raw := buildOutgoingMessage(
+		"alice@example.com",
+		"bob@example.com\r\nBcc: victim@evil.com",
+		"carol@example.com\r\nReply-To: attacker@evil.com",
+		"Hi\r\nBcc: victim@evil.com\r\nReply-To: attacker@evil.com",
+		"body",
+		"",
+		nil,
+	)
+
+	// 注入的头不允许以独立头形式出现
+	for _, injected := range []string{
+		"Bcc:", "Reply-To:",
+	} {
+		if strings.Contains(raw, "\r\n"+injected) || strings.HasPrefix(raw, injected) {
+			t.Fatalf("injected header %q found in message:\n%s", injected, raw)
+		}
+	}
+
+	// 注入的邮箱地址本身允许以折叠形式残留在原头值中，
+	// 但绝不能成为独立的一行头。
+	lines := strings.Split(raw, "\r\n")
+	for _, line := range lines[1:] { // 跳过 From
+		trimmed := strings.TrimSpace(line)
+		if strings.HasPrefix(trimmed, "Bcc:") || strings.HasPrefix(trimmed, "Reply-To:") {
+			t.Fatalf("injected header line %q found in message:\n%s", line, raw)
+		}
+	}
+}
+
+func TestBuildOutgoingMessageAttFilenameInjection(t *testing.T) {
+	atts := []pendingAttachment{
+		{filename: "evil.png\r\nBcc: victim@evil.com", contentType: "image/png", data: []byte("x")},
+		{filename: `quote".png`, contentType: "image/png", data: []byte("x")},
+	}
+	_, raw := buildOutgoingMessage("a@b.com", "c@d.com", "", "t", "body", "", atts)
+
+	lines := strings.Split(raw, "\r\n")
+	for _, line := range lines {
+		trimmed := strings.TrimSpace(line)
+		if strings.HasPrefix(trimmed, "Bcc:") {
+			t.Fatalf("filename header injection found: %q\nmessage:\n%s", line, raw)
+		}
+	}
+
+	// 含引号/换行的文件名必须被正确编码，不能破坏头结构
+	if !strings.Contains(raw, "Content-Disposition: attachment;") {
+		t.Fatalf("Content-Disposition missing in message:\n%s", raw)
+	}
+}
+
+func TestBuildOutgoingMessageEncodesNonASCIISubject(t *testing.T) {
+	_, raw := buildOutgoingMessage("a@b.com", "c@d.com", "", "中文主题测试", "body", "", nil)
+	// 非 ASCII 主题应按 RFC 2047 编码为 =?utf-8?...?= 形式
+	if !strings.Contains(raw, "Subject: =?utf-8?") && !strings.Contains(raw, "Subject: =?UTF-8?") {
+		t.Fatalf("non-ASCII subject should be RFC 2047 encoded, got:\n%s", raw)
+	}
+	// 头部不应再包含裸中文（应被编码）
+	for _, line := range strings.Split(raw, "\r\n") {
+		if strings.HasPrefix(line, "Subject:") && strings.ContainsAny(line, "中文测试") {
+			t.Fatalf("raw non-ASCII in Subject header: %q", line)
+		}
+	}
+}
+
+func TestFormatContentDisposition(t *testing.T) {
+	if got := formatContentDisposition("report.pdf"); got != "attachment; filename=report.pdf" {
+		t.Fatalf("simple filename: got %q", got)
+	}
+	// 特殊字符需要安全编码而不是原样嵌入
+	got := formatContentDisposition("a\"b\\c\r\nd.png")
+	if strings.ContainsAny(got, "\r\n") {
+		t.Fatalf("CRLF leaked into Content-Disposition: %q", got)
+	}
+}
@@ -0,0 +1,208 @@
+package handlers
+
+// P1 #2 回归测试：OAuth2 state 必须随机、回调必须校验。
+// 旧实现 state 为硬编码常量且回调完全不校验（登录 CSRF / 授权码注入）。
+
+import (
+	"html/template"
+	"math"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"mail_go/config"
+	"mail_go/internal/mailutil"
+
+	"github.com/gin-gonic/gin"
+)
+
+// testTemplateFuncs 提供模板解析所需的自定义函数（与 web 包的
+// templateFuncs 等价，但 handlers 包无法反向依赖 web 包）。
+func testTemplateFuncs() template.FuncMap {
+	return template.FuncMap{
+		"add":        func(a, b int) int { return a + b },
+		"sub":        func(a, b int) int { return a - b },
+		"mul":        func(a, b int) int { return a * b },
+		"div":        func(a, b int) int { return a / b },
+		"mod":        func(a, b int) int { return a % b },
+		"ceilDiv":    func(a, b int) int { return int(math.Ceil(float64(a) / float64(b))) },
+		"seq":        func(n int) []int { r := make([]int, n); for i := range r { r[i] = i + 1 }; return r },
+		"domainName": func(domainID uint, domains []interface{}) string { return "Domain #1" },
+		"safeHTML":   func(s string) template.HTML { return template.HTML(s) },
+		"safeJS":     func(s string) template.JS { return template.JS(s) },
+		"formatBytes": func(b int64) string {
+			return "1 KB"
+		},
+		"decodeHeader": mailutil.DecodeRFC2047,
+		"mailName":     func(s string) string { return s },
+		"mailEmail":    func(s string) string { return s },
+		"initial":      func(s string) string { return "?" },
+		"truncate":     func(s string, n int) string { return s },
+		"shortDate":    func(t time.Time) string { return t.Format("2006-01-02") },
+		"avatarStyle":  func(s string) string { return "background:#eee;color:#333" },
+	}
+}
+
+func newOAuth2TestContext(t *testing.T) (*gin.Context, *AuthHandler, *httptest.ResponseRecorder) {
+	t.Helper()
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, engine := gin.CreateTestContext(w)
+	// 回调的错误分支渲染 login 模板，需要加载模板及自定义函数
+	tmpl := template.Must(template.New("").Funcs(testTemplateFuncs()).ParseGlob(filepath.Join("..", "templates", "*.html")))
+	engine.SetHTMLTemplate(tmpl)
+	c.Request = httptest.NewRequest(http.MethodGet, "/auth/oauth2", nil)
+
+	authCfg := config.AuthConfig{
+		OAuth2Enabled:      true,
+		// 使用本地拒绝连接的地址作为 provider，token 交换快速失败，
+		// 测试不依赖外部网络。
+		OAuth2Provider:     "127.0.0.1:1",
+		OAuth2ClientID:     "test-client-id",
+		OAuth2ClientSecret: "test-client-secret",
+		OAuth2RedirectURL:  "https://mail.example.com/auth/oauth2/callback",
+	}
+	h := NewAuthHandler(nil, authCfg, config.BanConfig{MaxFailAttempts: 100})
+	return c, h, w
+}
+
+func TestRandomOAuth2State(t *testing.T) {
+	s1, err := randomOAuth2State()
+	if err != nil {
+		t.Fatalf("randomOAuth2State() error: %v", err)
+	}
+	if len(s1) != oauth2StateRandLen*2 {
+		t.Fatalf("state length = %d, want %d (hex)", len(s1), oauth2StateRandLen*2)
+	}
+	s2, _ := randomOAuth2State()
+	if s1 == s2 {
+		t.Fatal("state must be unique per request")
+	}
+	if s1 == "mailgo_oauth2_state" {
+		t.Fatal("state must not be the old hardcoded constant")
+	}
+}
+
+func TestOAuth2StartSetsRandomStateCookie(t *testing.T) {
+	c, h, w := newOAuth2TestContext(t)
+	h.OAuth2Start(c)
+
+	if w.Code != http.StatusFound {
+		t.Fatalf("status = %d, want 302", w.Code)
+	}
+	loc := w.Header().Get("Location")
+	if !strings.Contains(loc, "state=") {
+		t.Fatalf("redirect URL should carry state: %s", loc)
+	}
+
+	// state cookie 必须存在且与 URL 中的一致
+	cookies := w.Result().Cookies()
+	var stateVal string
+	found := false
+	for _, ck := range cookies {
+		if ck.Name == oauth2StateCookie {
+			found = true
+			stateVal = ck.Value
+			if !ck.HttpOnly {
+				t.Error("state cookie must be HttpOnly")
+			}
+			if !ck.Secure {
+				t.Error("state cookie must be Secure")
+			}
+			if ck.MaxAge <= 0 || ck.MaxAge > oauth2StateMaxAge {
+				t.Errorf("state cookie MaxAge = %d, want in (0, %d]", ck.MaxAge, oauth2StateMaxAge)
+			}
+		}
+	}
+	if !found {
+		t.Fatal("OAuth2Start should set state cookie")
+	}
+
+	u, err := url.Parse(loc)
+	if err != nil {
+		t.Fatalf("parse location: %v", err)
+	}
+	if u.Query().Get("state") != stateVal {
+		t.Fatalf("cookie state %q != URL state %q", stateVal, u.Query().Get("state"))
+	}
+
+	// 两次发起的 state 不同
+	c2, h2, w2 := newOAuth2TestContext(t)
+	h2.OAuth2Start(c2)
+	u2, _ := url.Parse(w2.Header().Get("Location"))
+	if u2.Query().Get("state") == stateVal {
+		t.Fatal("state must differ between sessions")
+	}
+}
+
+func TestOAuth2CallbackRejectsMissingOrMismatchedState(t *testing.T) {
+	cases := []struct {
+		name        string
+		cookieState string
+		queryState  string
+	}{
+		{"no cookie", "", "abc"},
+		{"no query state", "abc", ""},
+		{"mismatch", "abc", "xyz"},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			c, h, w := newOAuth2TestContext(t)
+			q := url.Values{}
+			q.Set("code", "test-code")
+			if tc.queryState != "" {
+				q.Set("state", tc.queryState)
+			}
+			c.Request = httptest.NewRequest(http.MethodGet, "/auth/oauth2/callback?"+q.Encode(), nil)
+			if tc.cookieState != "" {
+				c.Request.AddCookie(&http.Cookie{Name: oauth2StateCookie, Value: tc.cookieState})
+			}
+			h.OAuth2Callback(c)
+			if w.Code != http.StatusForbidden {
+				t.Fatalf("status = %d, want 403", w.Code)
+			}
+		})
+	}
+}
+
+func TestOAuth2CallbackAcceptsValidState(t *testing.T) {
+	// 模拟完整流程：Start 下发 state -> Callback 带回同一 state。
+	// state 校验通过后应进入后续流程（本测试无真实 IdP，
+	// code 交换会失败并渲染登录错误页，但这证明 state 关卡已通过）。
+	c, h, w := newOAuth2TestContext(t)
+	h.OAuth2Start(c)
+	var stateVal string
+	for _, ck := range w.Result().Cookies() {
+		if ck.Name == oauth2StateCookie {
+			stateVal = ck.Value
+		}
+	}
+
+	w2 := httptest.NewRecorder()
+	c2, engine2 := gin.CreateTestContext(w2)
+	tmpl2 := template.Must(template.New("").Funcs(testTemplateFuncs()).ParseGlob(filepath.Join("..", "templates", "*.html")))
+	engine2.SetHTMLTemplate(tmpl2)
+	q := url.Values{}
+	q.Set("code", "test-code")
+	q.Set("state", stateVal)
+	c2.Request = httptest.NewRequest(http.MethodGet, "/auth/oauth2/callback?"+q.Encode(), nil)
+	c2.Request.AddCookie(&http.Cookie{Name: oauth2StateCookie, Value: stateVal})
+
+	h.OAuth2Callback(c2)
+
+	// state 校验失败返回 403；此处应为非 403（进入 token 交换失败分支）
+	if w2.Code == http.StatusForbidden {
+		t.Fatalf("valid state was rejected")
+	}
+	if !strings.Contains(w2.Body.String(), "OAuth2") {
+		body := w2.Body.String()
+		if len(body) > 200 {
+			body = body[:200]
+		}
+		t.Fatalf("expected OAuth2 error page after state check passed, body: %s", body)
+	}
+}
@@ -48,6 +48,13 @@ func AuthMiddleware(stores *store.Stores) gin.HandlerFunc {
 			return
 		}

+		// 首次登录/密码被重置的用户必须先修改密码才能使用其他功能
+		if user.MustChangePassword && c.Request.URL.Path != "/settings" && c.Request.URL.Path != "/logout" {
+			c.Redirect(302, "/settings?force=1")
+			c.Abort()
+			return
+		}
+
 		c.Set("currentUser", user)
 		c.Set("userID", id)
 		c.Next()
@@ -0,0 +1,36 @@
+package middleware
+
+import (
+	"github.com/gin-gonic/gin"
+)
+
+// securityCSP 是本应用的基础 CSP。
+//
+// 说明：
+//   - 模板大量使用内联脚本/样式（Quill 初始化、行内事件处理、
+//     avatarStyle 内联 CSS），故 script-src / style-src 需要
+//     'unsafe-inline'；
+//   - 邮件正文在 srcdoc iframe 中渲染，可能引用远程图片（https:），
+//     因此 img-src 放行 https，同时仍阻止 data: 以外的自定义协议；
+//   - frame-ancestors 'none' 与 X-Frame-Options 共同防护点击劫持；
+//   - connect-src 'self' / form-action 'self' 阻止页面数据外泄到
+//     外部域名。
+const securityCSP = "default-src 'self'; " +
+	"script-src 'self' 'unsafe-inline'; " +
+	"style-src 'self' 'unsafe-inline'; " +
+	"img-src 'self' data: https:; " +
+	"connect-src 'self'; object-src 'none'; base-uri 'self'; " +
+	"form-action 'self'; frame-ancestors 'none'"
+
+// SecurityHeaders 为所有响应设置基础安全头：HSTS、点击劫持防护、
+// MIME 嗅探防护、Referrer 策略与基础 CSP。
+func SecurityHeaders() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		c.Header("Strict-Transport-Security", "max-age=31536000; includeSubDomains")
+		c.Header("X-Frame-Options", "DENY")
+		c.Header("X-Content-Type-Options", "nosniff")
+		c.Header("Referrer-Policy", "strict-origin-when-cross-origin")
+		c.Header("Content-Security-Policy", securityCSP)
+		c.Next()
+	}
+}
@@ -0,0 +1,45 @@
+package middleware
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+)
+
+// TestSecurityHeaders 验证所有基础安全响应头都存在。
+func TestSecurityHeaders(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	r := gin.New()
+	r.Use(SecurityHeaders())
+	r.GET("/", func(c *gin.Context) { c.String(http.StatusOK, "ok") })
+
+	w := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	r.ServeHTTP(w, req)
+
+	for _, h := range []string{
+		"Strict-Transport-Security",
+		"X-Frame-Options",
+		"X-Content-Type-Options",
+		"Referrer-Policy",
+		"Content-Security-Policy",
+	} {
+		if v := w.Header().Get(h); v == "" {
+			t.Errorf("missing security header %q", h)
+		}
+	}
+
+	// 关键头内容抽查
+	if got := w.Header().Get("X-Frame-Options"); got != "DENY" {
+		t.Errorf("X-Frame-Options = %q, want DENY", got)
+	}
+	if got := w.Header().Get("Content-Security-Policy"); !strings.Contains(got, "frame-ancestors 'none'") {
+		t.Errorf("CSP should include frame-ancestors 'none', got %q", got)
+	}
+	if got := w.Header().Get("Content-Security-Policy"); !strings.Contains(got, "connect-src 'self'") {
+		t.Errorf("CSP should include connect-src 'self', got %q", got)
+	}
+}
@@ -5,6 +5,7 @@ import (
 	"html/template"
 	"math"
 	"net"
+	"net/http"
 	"os"
 	"path/filepath"
 	"strings"
@@ -166,17 +167,31 @@ func avatarStyle(s string) string {

 // NewWebServer creates a new WebServer, initializes the Gin engine,
 // configures sessions, middleware, and registers all routes.
-func NewWebServer(cfg config.WebConfig, stores *store.Stores, attStorage *storage.AttachmentStorage, storageCfg config.StorageConfig, authCfg config.AuthConfig, banCfg config.BanConfig, caddyCfg config.CaddyConfig, ob *outbound.Manager) *WebServer {
+func NewWebServer(cfg config.WebConfig, stores *store.Stores, attStorage *storage.AttachmentStorage, storageCfg config.StorageConfig, authCfg config.AuthConfig, banCfg config.BanConfig, caddyCfg config.CaddyConfig, ob *outbound.Manager) (*WebServer, error) {
+	if err := config.ValidateSecretKey(cfg.SecretKey); err != nil {
+		return nil, err
+	}
+
 	gin.SetMode(gin.ReleaseMode)
 	engine := gin.New()
 	engine.Use(gin.Logger())
 	engine.Use(gin.Recovery())

-	// Session store (cookie-based)
-	cookieStore := cookie.NewStore([]byte("mail-go-secret-key-change-in-production"))
+	// 仅信任本机回环上的反向代理（Caddy/Nginx）。外部直连时
+	// X-Forwarded-For 不可信，防止伪造客户端 IP 绕过登录封禁或
+	// 恶意封禁他人 IP。gin 对 Unix socket 监听无条件信任转发头，
+	// 因此 socket 必须保持仅本机可达。
+	if err := engine.SetTrustedProxies([]string{"127.0.0.1", "::1"}); err != nil {
+		return nil, fmt.Errorf("设置可信代理失败: %w", err)
+	}
+
+	// Session store (cookie-based). The signing key comes from the config
+	// file (auto-generated random key) or the MAILGO_SECRET_KEY env var.
+	cookieStore := cookie.NewStore([]byte(cfg.SecretKey))
 	cookieStore.Options(sessions.Options{
 		HttpOnly: true,
-		SameSite: 3, // SameSiteLaxMode
+		SameSite: 3, // SameSiteStrictMode（比 Lax 更严格）
+		Secure:   cfg.CookieSecure,
 		MaxAge:   86400,
 		Path:     "/",
 	})
@@ -201,7 +216,7 @@ func NewWebServer(cfg config.WebConfig, stores *store.Stores, attStorage *storag
 	}

 	ws.registerRoutes()
-	return ws
+	return ws, nil
 }

 // registerRoutes sets up all HTTP routes with their handlers and middleware.
@@ -212,6 +227,8 @@ func (ws *WebServer) registerRoutes() {

 	// Apply BanMiddleware globally before public routes
 	ws.engine.Use(middleware.BanMiddleware(ws.stores))
+	// Security headers on every response
+	ws.engine.Use(middleware.SecurityHeaders())

 	// Public routes (no auth required)
 	ws.engine.GET("/login", authHandler.ShowLogin)
@@ -278,6 +295,12 @@ func (ws *WebServer) registerRoutes() {
 	}
 }

+// Handler returns the underlying Gin engine as an http.Handler, useful for
+// integration tests and for embedding behind a reverse proxy.
+func (ws *WebServer) Handler() http.Handler {
+	return ws.engine
+}
+
 // Start launches the HTTP server on the configured address.
 // Supports both TCP (e.g. ":8080") and Unix socket (e.g. "/run/mail_go/web.sock").
 func (ws *WebServer) Start() error {
@@ -0,0 +1,196 @@
+package web
+
+// P0 回归测试：验证会话 cookie 由配置中的 secret_key 签名，
+// 且旧版硬编码密钥（源码公开，视为已泄露）无法再伪造有效会话。
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"mail_go/config"
+	"mail_go/internal/db"
+	"mail_go/internal/storage"
+	"mail_go/internal/store"
+
+	"github.com/gorilla/securecookie"
+	"golang.org/x/crypto/bcrypt"
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+)
+
+func chdirRepoRoot(t *testing.T) {
+	t.Helper()
+	// NewWebServer 以相对路径加载 internal/web/templates/，
+	// 测试进程的 CWD 是 internal/web，需要切到仓库根目录。
+	if err := os.Chdir(filepath.Join("..", "..")); err != nil {
+		t.Fatalf("chdir to repo root: %v", err)
+	}
+	t.Cleanup(func() { _ = os.Chdir(filepath.Join("internal", "web")) })
+}
+
+func newTestStores(t *testing.T) *store.Stores {
+	t.Helper()
+	gdb, err := gorm.Open(sqlite.Open(filepath.Join(t.TempDir(), "test.db")), &gorm.Config{})
+	if err != nil {
+		t.Fatalf("open sqlite: %v", err)
+	}
+	if err := gdb.AutoMigrate(&db.User{}, &db.Domain{}, &db.Message{}, &db.Attachment{}, &db.BanEntry{}, &db.OutboundMessage{}); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+	return store.NewStores(gdb)
+}
+
+func newTestWebServer(t *testing.T, secretKey string) (*WebServer, *store.Stores) {
+	t.Helper()
+	chdirRepoRoot(t)
+
+	stores := newTestStores(t)
+
+	domain := &db.Domain{Name: "example.com", SmtpPort: 25, ImapPort: 143, Pop3Port: 110}
+	if err := stores.Domains.Create(domain); err != nil {
+		t.Fatalf("create domain: %v", err)
+	}
+	hash, err := bcrypt.GenerateFromPassword([]byte("test-password-123"), bcrypt.MinCost)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := stores.Users.Create(&db.User{
+		Username:     "alice",
+		PasswordHash: string(hash),
+		DomainID:     domain.ID,
+		IsActive:     true,
+	}); err != nil {
+		t.Fatalf("create user: %v", err)
+	}
+
+	baseDir := t.TempDir()
+	attStorage := storage.NewAttachmentStorage(filepath.Join(baseDir, "attachments"))
+	cfg := config.WebConfig{Addr: "127.0.0.1:0", SecretKey: secretKey, CookieSecure: true}
+
+	ws, err := NewWebServer(cfg, stores, attStorage, config.StorageConfig{BaseDir: baseDir},
+		config.AuthConfig{}, config.BanConfig{MaxFailAttempts: 100}, config.CaddyConfig{}, nil)
+	if err != nil {
+		t.Fatalf("NewWebServer: %v", err)
+	}
+	return ws, stores
+}
+
+func TestSessionSignedWithConfiguredSecretKey(t *testing.T) {
+	ws, _ := newTestWebServer(t, "0123456789abcdef0123456789abcdef")
+	srv := httptest.NewServer(ws.Handler())
+	defer srv.Close()
+
+	// 登录成功 -> 返回会话 cookie（禁用自动重定向以获取原始 302 响应）
+	form := url.Values{"email": {"alice@example.com"}, "password": {"test-password-123"}}
+	loginReq, _ := http.NewRequest(http.MethodPost, srv.URL+"/login", strings.NewReader(form.Encode()))
+	loginReq.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	client := &http.Client{CheckRedirect: func(req *http.Request, via []*http.Request) error {
+		return http.ErrUseLastResponse
+	}}
+	resp, err := client.Do(loginReq)
+	if err != nil {
+		t.Fatalf("login request: %v", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusFound {
+		t.Fatalf("login status = %d, want 302", resp.StatusCode)
+	}
+	var sessionCookie string
+	for _, c := range resp.Cookies() {
+		if c.Name == "mail_go_session" {
+			sessionCookie = c.Value
+			if !c.HttpOnly {
+				t.Error("session cookie must be HttpOnly")
+			}
+			if !c.Secure {
+				t.Error("session cookie must be Secure")
+			}
+			if c.SameSite != http.SameSiteStrictMode {
+				t.Errorf("session cookie SameSite = %v, want Strict", c.SameSite)
+			}
+		}
+	}
+	if sessionCookie == "" {
+		t.Fatal("login should set mail_go_session cookie")
+	}
+
+	// 合法会话可以访问收件箱
+	req, _ := http.NewRequest(http.MethodGet, srv.URL+"/inbox", nil)
+	req.AddCookie(&http.Cookie{Name: "mail_go_session", Value: sessionCookie})
+	resp2, err := client.Do(req)
+	if err != nil {
+		t.Fatalf("inbox request: %v", err)
+	}
+	defer resp2.Body.Close()
+	if resp2.StatusCode != http.StatusOK {
+		t.Fatalf("inbox with valid session: status = %d, want 200", resp2.StatusCode)
+	}
+}
+
+func TestLegacyHardcodedKeyCannotForgeSession(t *testing.T) {
+	// 服务端使用随机生成的新密钥
+	ws, _ := newTestWebServer(t, "9f8e7d6c5b4a39281706f5e4d3c2b1a09f8e7d6c5b4a39281706f5e4d3c2b1a0")
+	srv := httptest.NewServer(ws.Handler())
+	defer srv.Close()
+
+	// 攻击者用旧硬编码密钥（源码中公开）伪造管理员会话
+	forger := securecookie.New([]byte(config.InsecureLegacySecretKey), nil)
+	forged, err := forger.Encode("mail_go_session", map[interface{}]interface{}{
+		"userID":    uint(1),
+		"userEmail": "admin@example.com",
+		"isAdmin":   true,
+	})
+	if err != nil {
+		t.Fatalf("forge cookie: %v", err)
+	}
+
+	req, _ := http.NewRequest(http.MethodGet, srv.URL+"/inbox", nil)
+	req.AddCookie(&http.Cookie{Name: "mail_go_session", Value: forged})
+	client := &http.Client{CheckRedirect: func(req *http.Request, via []*http.Request) error {
+		return http.ErrUseLastResponse
+	}}
+	resp, err := client.Do(req)
+	if err != nil {
+		t.Fatalf("request with forged cookie: %v", err)
+	}
+	defer resp.Body.Close()
+
+	// 签名校验失败 -> 未认证，必须被重定向到登录页
+	if resp.StatusCode != http.StatusFound {
+		t.Fatalf("forged legacy-key session must be rejected: status = %d, want 302 redirect to /login", resp.StatusCode)
+	}
+	if loc := resp.Header.Get("Location"); !strings.HasPrefix(loc, "/login") {
+		t.Fatalf("forged session should redirect to /login, got Location: %q", loc)
+	}
+}
+
+func TestNewWebServerRejectsBadSecretKeys(t *testing.T) {
+	chdirRepoRoot(t)
+	stores := newTestStores(t)
+	baseDir := t.TempDir()
+	attStorage := storage.NewAttachmentStorage(filepath.Join(baseDir, "attachments"))
+
+	cases := []struct {
+		name string
+		key  string
+	}{
+		{"empty", ""},
+		{"legacy default", config.InsecureLegacySecretKey},
+		{"too short", "short-key"},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := NewWebServer(config.WebConfig{Addr: "127.0.0.1:0", SecretKey: tc.key},
+				stores, attStorage, config.StorageConfig{BaseDir: baseDir},
+				config.AuthConfig{}, config.BanConfig{}, config.CaddyConfig{}, nil)
+			if err == nil {
+				t.Fatalf("NewWebServer should reject secret key %q", tc.key)
+			}
+		})
+	}
+}
@@ -489,3 +489,127 @@
    </div>
 </aside>
 {{end}}
+
+{{define "listjs"}}
+<script>
+(function () {
+    var searchInput = document.getElementById('mail-search');
+    var rows = Array.prototype.slice.call(document.querySelectorAll('.mail-row'));
+    var selectAll = document.getElementById('select-all');
+    var btnDelete = document.getElementById('btn-delete');
+
+    // 行点击跳转（复选框 / 行内删除按钮除外）
+    rows.forEach(function (row) {
+        row.addEventListener('click', function (e) {
+            if (e.target.closest('.cell-check') || e.target.closest('.row-del')) return;
+            var link = row.querySelector('.cell-subject');
+            if (link) window.location.href = link.getAttribute('href');
+        });
+    });
+
+    // 全选
+    selectAll && selectAll.addEventListener('change', function () {
+        rows.forEach(function (row) {
+            var cb = row.querySelector('.row-check');
+            cb.checked = selectAll.checked;
+            row.classList.toggle('selected', cb.checked);
+        });
+        updateDeleteState();
+    });
+    rows.forEach(function (row) {
+        var cb = row.querySelector('.row-check');
+        cb.addEventListener('change', function () {
+            row.classList.toggle('selected', cb.checked);
+            if (!cb.checked && selectAll) selectAll.checked = false;
+            updateDeleteState();
+        });
+    });
+
+    function updateDeleteState() {
+        if (!btnDelete) return;
+        var n = rows.filter(function (r) { return r.isConnected && r.querySelector('.row-check').checked; }).length;
+        btnDelete.disabled = n === 0;
+    }
+
+    // 批量删除
+    btnDelete && btnDelete.addEventListener('click', function () {
+        var ids = rows.filter(function (r) { return r.isConnected && r.querySelector('.row-check').checked; })
+                      .map(function (r) { return r.dataset.id; });
+        if (!ids.length) return;
+        if (!confirm('确定要删除选中的 ' + ids.length + ' 封邮件吗？')) return;
+        var done = 0;
+        ids.forEach(function (id) {
+            fetch('/mail/delete/' + id, { method: 'POST', body: new FormData() })
+                .then(function () { if (++done === ids.length) window.location.reload(); })
+                .catch(function () { if (++done === ids.length) window.location.reload(); });
+        });
+    });
+
+    // 刷新
+    var btnRefresh = document.getElementById('btn-refresh');
+    btnRefresh && btnRefresh.addEventListener('click', function () { window.location.reload(); });
+
+    // 搜索过滤（发件人 / 主题 / 摘要）
+    searchInput && searchInput.addEventListener('input', function () {
+        var q = searchInput.value.trim().toLowerCase();
+        rows.forEach(function (row) {
+            if (!row.isConnected) return;
+            var text = row.textContent.toLowerCase();
+            row.style.display = (!q || text.indexOf(q) !== -1) ? '' : 'none';
+        });
+    });
+
+    // 从 BFCache（往返缓存）恢复时静默同步最新列表状态：
+    // 阅读页已把邮件标记为已读/删除，恢复的旧 DOM 需要与服务端对齐，
+    // 避免“返回后仍是未读/已删邮件仍显示”。
+    // 真实浏览器在 BFCache 恢复时会触发 pageshow(persisted=true)；
+    // visibilitychange 作为兜底（页面重新可见时也同步一次）。
+    var syncing = false;
+    function syncFromServer(forceReloadOnError) {
+        if (syncing) return;
+        syncing = true;
+        fetch(window.location.href, { headers: { 'Accept': 'text/html' }, credentials: 'same-origin' })
+            .then(function (r) { return r.text(); })
+            .then(function (html) {
+                var doc = new DOMParser().parseFromString(html, 'text/html');
+                var fresh = {};
+                doc.querySelectorAll('.mail-row').forEach(function (r) { fresh[r.dataset.id] = r.classList.contains('unread'); });
+                rows.forEach(function (row) {
+                    var id = row.dataset.id;
+                    if (!(id in fresh)) { row.remove(); return; } // 已被删除
+                    row.classList.toggle('unread', fresh[id]);
+                    var wrap = row.querySelector('.cell-subject-wrap');
+                    var dot = row.querySelector('.unread-dot');
+                    if (fresh[id] && !dot && wrap) {
+                        var s = document.createElement('span');
+                        s.className = 'unread-dot';
+                        wrap.insertBefore(s, wrap.firstChild);
+                    } else if (!fresh[id] && dot) {
+                        dot.remove();
+                    }
+                });
+                // 同步“共 N 封”与侧栏未读角标
+                var total = doc.querySelector('.page-info');
+                var curTotal = document.querySelector('.page-info');
+                if (total && curTotal) curTotal.textContent = total.textContent;
+                var badge = doc.querySelector('.folder.active .badge');
+                var curBadge = document.querySelector('.folder.active .badge');
+                if (badge && curBadge) curBadge.textContent = badge.textContent;
+                else if (!badge && curBadge) curBadge.remove();
+            })
+            .catch(function () {
+                // BFCache 恢复时 DOM 是旧的，同步失败只能整页刷新兜底；
+                // 标签页切回触发的同步失败则静默忽略（可能只是离线）。
+                if (forceReloadOnError) window.location.reload();
+            })
+            .then(function () { syncing = false; });
+    }
+    window.addEventListener('pageshow', function (e) {
+        if (e.persisted) syncFromServer(true);
+    });
+    document.addEventListener('visibilitychange', function () {
+        if (document.visibilityState === 'visible') syncFromServer(false);
+    });
+})();
+</script>
+{{end}}
@@ -87,68 +87,7 @@
            </div>
        </main>
    </div>
-    <script>
-    (function () {
-        var searchInput = document.getElementById('mail-search');
-        var rows = Array.prototype.slice.call(document.querySelectorAll('.mail-row'));
-        var selectAll = document.getElementById('select-all');
-        var btnDelete = document.getElementById('btn-delete');
-
-        rows.forEach(function (row) {
-            row.addEventListener('click', function (e) {
-                if (e.target.closest('.cell-check') || e.target.closest('.row-del')) return;
-                window.location.href = row.querySelector('.cell-subject').getAttribute('href');
-            });
-        });
-
-        selectAll && selectAll.addEventListener('change', function () {
-            rows.forEach(function (row) {
-                var cb = row.querySelector('.row-check');
-                cb.checked = selectAll.checked;
-                row.classList.toggle('selected', cb.checked);
-            });
-            updateDeleteState();
-        });
-        rows.forEach(function (row) {
-            var cb = row.querySelector('.row-check');
-            cb.addEventListener('change', function () {
-                row.classList.toggle('selected', cb.checked);
-                if (!cb.checked && selectAll) selectAll.checked = false;
-                updateDeleteState();
-            });
-        });
-
-        function updateDeleteState() {
-            if (!btnDelete) return;
-            var n = rows.filter(function (r) { return r.querySelector('.row-check').checked; }).length;
-            btnDelete.disabled = n === 0;
-        }
-
-        btnDelete && btnDelete.addEventListener('click', function () {
-            var ids = rows.filter(function (r) { return r.querySelector('.row-check').checked; })
-                          .map(function (r) { return r.dataset.id; });
-            if (!ids.length) return;
-            if (!confirm('确定要删除选中的 ' + ids.length + ' 封邮件吗？')) return;
-            var done = 0;
-            ids.forEach(function (id) {
-                fetch('/mail/delete/' + id, { method: 'POST', body: new FormData() })
-                    .then(function () { if (++done === ids.length) window.location.reload(); })
-                    .catch(function () { if (++done === ids.length) window.location.reload(); });
-            });
-        });
-
-        var btnRefresh = document.getElementById('btn-refresh');
-        btnRefresh && btnRefresh.addEventListener('click', function () { window.location.reload(); });
-
-        searchInput && searchInput.addEventListener('input', function () {
-            var q = searchInput.value.trim().toLowerCase();
-            rows.forEach(function (row) {
-                var text = row.textContent.toLowerCase();
-                row.style.display = (!q || text.indexOf(q) !== -1) ? '' : 'none';
-            });
-        });
-    })();
-    </script>
+    {{template "listjs" .}}
 </body>
 </html>
 {{end}}
@@ -82,75 +82,7 @@
            </div>
        </main>
    </div>
-    <script>
-    (function () {
-        var searchInput = document.getElementById('mail-search');
-        var rows = Array.prototype.slice.call(document.querySelectorAll('.mail-row'));
-        var selectAll = document.getElementById('select-all');
-        var btnDelete = document.getElementById('btn-delete');
-
-        // 行点击跳转（复选框除外）
-        rows.forEach(function (row) {
-            row.addEventListener('click', function (e) {
-                if (e.target.closest('.cell-check')) return;
-                window.location.href = row.querySelector('.cell-subject').getAttribute('href');
-            });
-        });
-
-        // 全选
-        selectAll && selectAll.addEventListener('change', function () {
-            rows.forEach(function (row) {
-                var cb = row.querySelector('.row-check');
-                cb.checked = selectAll.checked;
-                row.classList.toggle('selected', cb.checked);
-            });
-            updateDeleteState();
-        });
-        rows.forEach(function (row) {
-            var cb = row.querySelector('.row-check');
-            cb.addEventListener('change', function () {
-                row.classList.toggle('selected', cb.checked);
-                if (!cb.checked && selectAll) selectAll.checked = false;
-                updateDeleteState();
-            });
-        });
-
-        function updateDeleteState() {
-            if (!btnDelete) return;
-            var n = rows.filter(function (r) { return r.querySelector('.row-check').checked; }).length;
-            btnDelete.disabled = n === 0;
-        }
-
-        // 批量删除
-        btnDelete && btnDelete.addEventListener('click', function () {
-            var ids = rows.filter(function (r) { return r.querySelector('.row-check').checked; })
-                          .map(function (r) { return r.dataset.id; });
-            if (!ids.length) return;
-            if (!confirm('确定要删除选中的 ' + ids.length + ' 封邮件吗？')) return;
-            var done = 0;
-            ids.forEach(function (id) {
-                var fd = new FormData();
-                fd.append('_method', 'DELETE');
-                fetch('/mail/delete/' + id, { method: 'POST', body: fd })
-                    .then(function () { if (++done === ids.length) window.location.reload(); })
-                    .catch(function () { if (++done === ids.length) window.location.reload(); });
-            });
-        });
-
-        // 刷新
-        var btnRefresh = document.getElementById('btn-refresh');
-        btnRefresh && btnRefresh.addEventListener('click', function () { window.location.reload(); });
-
-        // 搜索过滤（发件人 / 主题 / 摘要）
-        searchInput && searchInput.addEventListener('input', function () {
-            var q = searchInput.value.trim().toLowerCase();
-            rows.forEach(function (row) {
-                var text = row.textContent.toLowerCase();
-                row.style.display = (!q || text.indexOf(q) !== -1) ? '' : 'none';
-            });
-        });
-    })();
-    </script>
+    {{template "listjs" .}}
 </body>
 </html>
 {{end}}
@@ -87,68 +87,7 @@
            </div>
        </main>
    </div>
-    <script>
-    (function () {
-        var searchInput = document.getElementById('mail-search');
-        var rows = Array.prototype.slice.call(document.querySelectorAll('.mail-row'));
-        var selectAll = document.getElementById('select-all');
-        var btnDelete = document.getElementById('btn-delete');
-
-        rows.forEach(function (row) {
-            row.addEventListener('click', function (e) {
-                if (e.target.closest('.cell-check') || e.target.closest('.row-del')) return;
-                window.location.href = row.querySelector('.cell-subject').getAttribute('href');
-            });
-        });
-
-        selectAll && selectAll.addEventListener('change', function () {
-            rows.forEach(function (row) {
-                var cb = row.querySelector('.row-check');
-                cb.checked = selectAll.checked;
-                row.classList.toggle('selected', cb.checked);
-            });
-            updateDeleteState();
-        });
-        rows.forEach(function (row) {
-            var cb = row.querySelector('.row-check');
-            cb.addEventListener('change', function () {
-                row.classList.toggle('selected', cb.checked);
-                if (!cb.checked && selectAll) selectAll.checked = false;
-                updateDeleteState();
-            });
-        });
-
-        function updateDeleteState() {
-            if (!btnDelete) return;
-            var n = rows.filter(function (r) { return r.querySelector('.row-check').checked; }).length;
-            btnDelete.disabled = n === 0;
-        }
-
-        btnDelete && btnDelete.addEventListener('click', function () {
-            var ids = rows.filter(function (r) { return r.querySelector('.row-check').checked; })
-                          .map(function (r) { return r.dataset.id; });
-            if (!ids.length) return;
-            if (!confirm('确定要删除选中的 ' + ids.length + ' 封邮件吗？')) return;
-            var done = 0;
-            ids.forEach(function (id) {
-                fetch('/mail/delete/' + id, { method: 'POST', body: new FormData() })
-                    .then(function () { if (++done === ids.length) window.location.reload(); })
-                    .catch(function () { if (++done === ids.length) window.location.reload(); });
-            });
-        });
-
-        var btnRefresh = document.getElementById('btn-refresh');
-        btnRefresh && btnRefresh.addEventListener('click', function () { window.location.reload(); });
-
-        searchInput && searchInput.addEventListener('input', function () {
-            var q = searchInput.value.trim().toLowerCase();
-            rows.forEach(function (row) {
-                var text = row.textContent.toLowerCase();
-                row.style.display = (!q || text.indexOf(q) !== -1) ? '' : 'none';
-            });
-        });
-    })();
-    </script>
+    {{template "listjs" .}}
 </body>
 </html>
 {{end}}
@@ -14,6 +14,9 @@
        <main class="mail-main settings-main">
            {{if .error}}<div class="alert alert-error">{{.error}}</div>{{end}}
            {{if .success}}<div class="alert alert-success">{{.success}}</div>{{end}}
+            {{if .mustChange}}<div class="alert" style="border:1px solid #ffa940;background:#fff7e6;color:#d46b08;border-radius:8px;padding:12px 16px;margin-bottom:16px;font-size:13.5px;">
+                ⚠️ 首次登录/密码已被重置，请立即修改密码后再继续使用邮箱功能。
+            </div>{{end}}

            <div class="card" style="max-width:720px;">
                <h2 style="font-size:17px;margin-bottom:18px;display:flex;align-items:center;gap:10px;">
@@ -0,0 +1,67 @@
+package web
+
+// P1 #3 回归测试：客户端 IP 不可通过 X-Forwarded-For 伪造。
+// 外部直连时伪造头必须被忽略（防绕过登录封禁/恶意封禁他人），
+// 本机回环（反向代理）转发时必须取 X-Forwarded-For 中的真实客户端 IP。
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+// doLoginFailure 触发一次登录失败（使 BanStore 按 ClientIP 记录失败计数），
+// 返回使用的请求。
+func doLoginFailure(t *testing.T, ws *WebServer, remoteAddr, xff string) {
+	t.Helper()
+	form := strings.NewReader("email=nobody@example.com&password=wrong")
+	req := httptest.NewRequest(http.MethodPost, "/login", form)
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.RemoteAddr = remoteAddr
+	if xff != "" {
+		req.Header.Set("X-Forwarded-For", xff)
+	}
+	w := httptest.NewRecorder()
+	ws.Handler().ServeHTTP(w, req)
+	if w.Code != http.StatusOK { // 登录失败重渲染登录页
+		t.Fatalf("login failure status = %d, want 200", w.Code)
+	}
+}
+
+func TestExternalClientIPCannotBeSpoofed(t *testing.T) {
+	ws, stores := newTestWebServer(t, "0123456789abcdef0123456789abcdef")
+
+	// 模拟外部攻击者直连 8080 端口，伪造 X-Forwarded-For
+	doLoginFailure(t, ws, "203.0.113.99:5555", "1.2.3.4")
+
+	// 失败计数必须记在真实来源 IP 上
+	if _, err := stores.Bans.GetByIP("1.2.3.4"); err == nil {
+		t.Fatal("spoofed X-Forwarded-For IP must not be recorded")
+	}
+	entry, err := stores.Bans.GetByIP("203.0.113.99")
+	if err != nil {
+		t.Fatalf("real client IP should be recorded: %v", err)
+	}
+	if entry.FailCount != 1 {
+		t.Fatalf("fail count = %d, want 1", entry.FailCount)
+	}
+}
+
+func TestLoopbackProxyXFFIsHonored(t *testing.T) {
+	ws, stores := newTestWebServer(t, "0123456789abcdef0123456789abcdef")
+
+	// 模拟本机 Caddy/Nginx 转发：RemoteAddr 是回环，XFF 是真实客户端
+	doLoginFailure(t, ws, "127.0.0.1:5555", "198.51.100.7")
+
+	entry, err := stores.Bans.GetByIP("198.51.100.7")
+	if err != nil {
+		t.Fatalf("proxied client IP should be recorded: %v", err)
+	}
+	if entry.FailCount != 1 {
+		t.Fatalf("fail count = %d, want 1", entry.FailCount)
+	}
+	if _, err := stores.Bans.GetByIP("127.0.0.1"); err == nil {
+		t.Fatal("proxy's own IP should not be recorded")
+	}
+}
@@ -238,7 +238,7 @@ func main() {
 	}

 	// 7. Start SMTP server
-	smtpSrv := smtp_server.NewSMTPServer(cfg.SMTP, stores, attStorage, outboundMgr, smtpTLS)
+	smtpSrv := smtp_server.NewSMTPServer(cfg.SMTP, stores, attStorage, outboundMgr, smtpTLS, cfg.Ban)
 	go func() {
 		if err := smtpSrv.Start(); err != nil {
 			log.Printf("SMTP 服务启动失败: %v", err)
@@ -259,7 +259,7 @@ func main() {
 	}

 	// 7. Start IMAP server
-	imapSrv := imap_server.NewIMAPServer(cfg.IMAP, stores, imapTLS)
+	imapSrv := imap_server.NewIMAPServer(cfg.IMAP, stores, imapTLS, cfg.Ban)
 	go func() {
 		if err := imapSrv.Start(); err != nil {
 			log.Printf("IMAP 服务启动失败: %v", err)
@@ -275,7 +275,7 @@ func main() {
 	}

 	// 8. Start POP3 server
-	pop3Srv := pop3_server.NewPOP3Server(cfg.POP3, stores, pop3TLS)
+	pop3Srv := pop3_server.NewPOP3Server(cfg.POP3, stores, pop3TLS, cfg.Ban)
 	go func() {
 		if err := pop3Srv.Start(); err != nil {
 			log.Printf("POP3 服务启动失败: %v", err)
@@ -291,7 +291,10 @@ func main() {
 	}

 	// 10. Start Web server
-	webServer := web.NewWebServer(cfg.Web, stores, attStorage, cfg.Storage, cfg.Auth, cfg.Ban, cfg.Caddy, outboundMgr)
+	webServer, err := web.NewWebServer(cfg.Web, stores, attStorage, cfg.Storage, cfg.Auth, cfg.Ban, cfg.Caddy, outboundMgr)
+	if err != nil {
+		log.Fatalf("Web 服务初始化失败: %v", err)
+	}
 	fmt.Printf("Web 服务启动在 %s\n", cfg.Web.Addr)
 	go func() {
 		if err := webServer.Start(); err != nil {
@@ -331,8 +334,18 @@ func ensureAdminUser(stores *store.Stores, cfg *config.Config) {
 		fmt.Println("默认域名 example.com 创建成功")
 	}

-	// Hash the default admin password
-	hashedPassword, err := bcrypt.GenerateFromPassword([]byte("admin"), bcrypt.DefaultCost)
+	// 初始密码：优先取环境变量 MAILGO_ADMIN_PASSWORD；
+	// 否则生成随机密码并打印一次（只能在本机启动日志中看到）。
+	// 无论哪种方式都会标记首次登录必须改密，杜绝默认口令。
+	adminPassword := os.Getenv("MAILGO_ADMIN_PASSWORD")
+	generated := false
+	if adminPassword == "" {
+		adminPassword = randomPassword()
+		generated = true
+	}
+
+	// Hash the admin password
+	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(adminPassword), bcrypt.DefaultCost)
 	if err != nil {
 		log.Printf("密码哈希失败: %v", err)
 		return
@@ -340,13 +353,14 @@ func ensureAdminUser(stores *store.Stores, cfg *config.Config) {

 	// Create the admin user
 	adminUser := &db.User{
-		Username:     "admin",
-		PasswordHash: string(hashedPassword),
-		DomainID:     domain.ID,
-		QuotaBytes:   5 * 1024 * 1024 * 1024, // 5GB
-		UsedBytes:    0,
-		IsActive:     true,
-		IsAdmin:      true,
+		Username:             "admin",
+		PasswordHash:         string(hashedPassword),
+		DomainID:             domain.ID,
+		QuotaBytes:           5 * 1024 * 1024 * 1024, // 5GB
+		UsedBytes:            0,
+		IsActive:             true,
+		IsAdmin:              true,
+		MustChangePassword:   true,
 	}

 	if createErr := stores.Users.Create(adminUser); createErr != nil {
@@ -354,5 +368,29 @@ func ensureAdminUser(stores *store.Stores, cfg *config.Config) {
 		return
 	}

-	fmt.Println("管理员账户 admin@example.com 创建成功（密码: admin）")
+	if generated {
+		fmt.Printf("管理员账户 admin@example.com 创建成功，初始密码: %s\n", adminPassword)
+	} else {
+		fmt.Println("管理员账户 admin@example.com 创建成功（密码来自 MAILGO_ADMIN_PASSWORD）")
+	}
+	fmt.Println("安全提示：该账户已被标记为“首次登录必须修改密码”，请登录后立即在 设置 页面修改。")
+}
+
+// randomPassword 生成 16 位随机密码（数字+大小写字母），用于初始管理员账户。
+func randomPassword() string {
+	const charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+	buf := make([]byte, 16)
+	if _, err := rand.Read(buf); err != nil {
+		// crypto/rand 失败极罕见；退化为时间种子以避免空密码
+		log.Printf("生成随机密码失败: %v，使用弱随机回退", err)
+		n := time.Now().UnixNano()
+		for i := range buf {
+			buf[i] = charset[(n>>(uint(i)*4))%int64(len(charset))]
+		}
+		return string(buf)
+	}
+	for i := range buf {
+		buf[i] = charset[int(buf[i])%len(charset)]
+	}
+	return string(buf)
 }
@@ -0,0 +1,180 @@
+# 安全漏洞修复 TODO
+
+依据 2026-08-19 的安全审计结果（代码静态审计 + mail.lmve.net 线上验证）整理。
+
+按优先级排列：P0 立即修复，P1 尽快修复，P2 排期修复，P3 加固项。
+
+## P0 严重：可被完全接管
+
+### 1. 会话签名密钥硬编码，可伪造任意管理员会话
+
+- [x] 位置：`internal/web/server.go:176`
+- 现状：`cookie.NewStore([]byte("mail-go-secret-key-change-in-production"))`，密钥写死在源码中且无配置项可更换。源码公开 = 任何人可签发 `userID=1, isAdmin=true` 的合法 cookie，直接以管理员身份进入线上后台。
+- 修复方案：
+  - [x] `config.Config` 新增 `[web] secret_key` 字段。
+  - [x] `LoadConfig()` 首次启动时用 `crypto/rand` 生成 32 字节随机密钥（hex 编码）写入配置文件；配置文件权限收紧为 0600（兼顾原有的中继密码等敏感字段）。
+  - [x] 支持环境变量 `MAILGO_SECRET_KEY` 覆盖（覆盖值不落盘，便于容器部署）。
+  - [x] 启动时校验：密钥为空 / 等于旧硬编码默认值 / 短于 16 字节时拒绝启动（`config.ValidateSecretKey` + `NewWebServer` 返回 error）。
+- 验证：
+  - [x] 重启后旧 cookie 全部失效（登录态被踢下线）。
+  - [x] 用旧硬编码密钥手工签发的 cookie 无法通过认证（`TestLegacyHardcodedKeyCannotForgeSession`：伪造 `userID=1, isAdmin=true` 的 cookie 被拒，302 回登录页）。
+  - [x] `config.LoadConfig()` 单测：首启生成、二次读取保持不变、旧配置补全、旧默认值替换、env 覆盖不落盘、文件权限 0600（`config/config_test.go`）。
+- 已完成（2026-08-19）。注：部署新版后所有用户需重新登录；配置文件权限由 0644 收紧为 0600。
+
+## P1 高危
+
+### 2. OAuth2 state 固定值且回调不校验（登录 CSRF / 授权码注入）
+
+- [x] 位置：`internal/web/handlers/auth.go`（原硬编码 `mailgo_oauth2_state`、`OAuth2Callback` 不校验 state）
+- 现状：当前部署未启用 OAuth2，属休眠漏洞，启用前必须修复。
+- 修复方案：
+  - [x] `OAuth2Start` 用 `crypto/rand` 生成 16 字节随机 state，写入独立的短期 SameSite=Lax cookie（`mail_go_oauth2_state`，10 分钟过期，HttpOnly+Secure）。注意主会话 cookie 是 SameSite=Strict，跨站回调导航不会携带，故不能放主会话。
+  - [x] `OAuth2Callback` 读取 `c.Query("state")` 与 cookie 值做 `subtle.ConstantTimeCompare` 比对，缺失/不匹配返回 403。
+  - [x] 比对后立即清除 cookie（`MaxAge=-1`），保证一次性使用。
+- 验证：
+  - [x] 单测：state 缺失/不匹配/无 cookie 均 403；start 设置的 cookie 与 URL state 一致且每次不同；有效 state 通过校验进入后续流程（`oauth2_state_test.go`）。
+  - [ ] 手工走完一次 OAuth2 流程（Google/GitHub）确认正常登录。
+
+### 3. Gin 信任所有代理，`ClientIP()` 可伪造（封禁绕过 / 爆破）
+
+- [x] 位置：`internal/web/server.go`（未调用 `SetTrustedProxies`）
+- 现状：gin 默认信任 0.0.0.0/0，`X-Forwarded-For` 可任意伪造。线上 8080 端口当前被防火墙挡住，属纵深防御缺失；一旦 8080/socket 可达：伪造不同 IP 即可绕过登录失败封禁无限爆破，也可恶意封禁任意 IP 造成 DoS。
+- 修复方案：
+  - [x] 统一 `engine.SetTrustedProxies([]string{"127.0.0.1", "::1"})`：外部直连时 XFF 完全不可信（防伪造/防封禁污染）；本机 Caddy/Nginx 转发时 XFF 仍可信（保留真实客户端 IP）。注意 gin 对 Unix socket 监听无条件信任转发头，socket 必须保持仅本机可达。
+  - [ ] install.sh 文档注明：8080 端口必须保持仅本机可达（防火墙/绑定 127.0.0.1）。
+- 验证：
+  - [x] 单测：外部直连 + 伪造 `X-Forwarded-For` 时封禁记录落在真实 IP 上；回环代理 + XFF 时记录 XFF 中的真实客户端 IP（`trustedproxy_test.go`）。
+  - [ ] 线上回归：Caddy 反代路径下管理后台封禁列表仍显示真实客户端 IP。
+
+### 4. Web 写信 CRLF 邮件头注入
+
+- [x] 位置：`internal/web/handlers/mail.go`（原 `to`/`cc`/`subject` 直接拼头、附件文件名拼进 `Content-Disposition`/`Content-Type`）
+- 现状：信封收件人经 `ParseAddress` 校验无法注入，但注入的头（如 `Reply-To`）会随邮件存储并外发，可被用于钓鱼。
+- 修复方案：
+  - [x] 新增 `sanitizeHeaderField`：strip `\r`、`\n`、NUL，应用于 From/To/Cc 头。
+  - [x] `subject` 经 `sanitizeHeaderField` + RFC 2047（`mime.QEncoding`）编码非 ASCII 内容。
+  - [x] 附件名经 `mime.FormatMediaType` 生成 `Content-Disposition`/`Content-Type name` 参数（RFC 2231 编码，中和 CRLF 注入）。
+  - [x] 消息构建抽出为 `buildOutgoingMessage` 纯函数（可单测）；`DownloadAttachment`/`AdminDownloadAttachment` 的响应头同步改用 `formatContentDisposition`。
+- 验证：
+  - [x] 单测：`to`/`cc`/`subject` 携带 CRLF 注入载荷时 RawData 无独立注入头；文件名含 CRLF/引号时头结构完好；非 ASCII 主题正确编码（`mail_injection_test.go`）。
+  - [ ] 含特殊字符附件名的邮件实测收发正常。
+
+## P2 中危
+
+### 5. 会话 Cookie 缺 Secure 标志
+
+- [x] 位置：`internal/web/server.go`
+- 修复方案：
+  - [x] `sessions.Options` 增加 `Secure: cfg.CookieSecure`；新增配置项 `[web].cookie_secure`（默认 true，仅本地 HTTP 调试时改 false；缺失字段按默认 true 处理，参照 relay_starttls 的原始文件检查）。
+  - [x] 修正 SameSite 注释（3 = Strict）。
+  - [x] 测试：会话 cookie 断言 HttpOnly+Secure+SameSite=Strict。
+- 验证：
+  - [x] 测试断言 cookie 标志。
+  - [ ] 线上登录后检查 `Set-Cookie` 包含 `Secure; HttpOnly; SameSite=Strict`。
+
+### 6. SMTP/IMAP/POP3 认证无速率限制
+
+- [x] 位置：`internal/smtp_server/server.go`、`internal/imap_server/`、`internal/pop3_server/server.go`
+- 修复方案：
+  - [x] `store.RecordAuthFailure(ip, maxFail, minutes)`：认证失败计数复用 BanStore，达到 `ban.max_fail_attempts` 阈值即封禁 `ban.ban_duration_min` 分钟（与 Web 登录共用封禁记录）。
+  - [x] SMTP：`NewSession` 记录 `c.Conn().RemoteAddr()` 提取 IP；Auth 回调失败计数 + 封禁 IP 拒绝认证。
+  - [x] IMAP：`Login(connInfo,...)` 从 `connInfo.RemoteAddr` 取 IP；失败计数 + 封禁拒绝。
+  - [x] POP3：`handleConn` 开头检查封禁直接拒绝；`handlePASS` 失败计数。
+  - [x] 三个服务器构造函数注入 `config.BanConfig`。
+- 验证：
+  - [x] store 层单测：达到阈值封禁、空 IP 无副作用、与 Web 共用封禁记录（`auth_guard_test.go`）。
+  - [ ] 线上用错误密码连续尝试触发封禁后，SMTP/IMAP/POP3 认证被拒。
+
+### 7. 附件存储路径遍历防护无效
+
+- [x] 位置：`internal/storage/attachment.go`
+- 修复方案：
+  - [x] `FullPath` 改为白名单校验（UUID 文件名正则），非法路径返回错误；兜底校验最终路径仍在 baseDir 内。
+  - [x] `Save` 的扩展名白名单化（`safeExt`，丢弃 CR/LF、路径分隔符等）。
+- 验证：
+  - [x] 单测：`../`、绝对路径、Windows 分隔符、空路径、注入文件名全部拒绝；合法文件名正常读写删（`attachment_test.go`）。
+
+### 8. 默认管理员 admin@example.com/admin
+
+- [x] 位置：`main.go`（`ensureAdminUser`）
+- 修复方案：
+  - [x] 初始密码改为：环境变量 `MAILGO_ADMIN_PASSWORD` 显式指定，否则生成 16 位随机密码打印一次。
+  - [x] User 模型新增 `MustChangePassword`：初始管理员、管理员重置密码的用户在登录后强制跳转设置页改密，改密后清除标记（`UpdatePassword` 顺带清除）。
+  - [x] AuthMiddleware 拦截（除 /settings、/logout），settings 页显示提示横幅。
+- 验证：
+  - [x] 全新数据库启动后 admin/admin 无法登录（密码为随机值）；登录后强制改密流程生效。
+  - [ ] 线上验证新装机流程。
+
+### 9. Smarthost 中继 TLS 不验证证书（凭据可被 MITM 截获）
+
+- [x] 位置：`internal/outbound/mailer.go`
+- 修复方案：
+  - [x] 直投 MX 保持机会式 TLS（`InsecureSkipVerify=true`，业界常规）；relay 路径默认验证证书（`InsecureSkipVerify=false`），IP literal 时以 IP 作为 ServerName 校验 IP SAN。
+  - [x] 新增配置 `outbound.relay_tls_insecure`（默认 false），供自签证书内网中继显式放行。
+- 验证：
+  - [x] 集成测试：自签证书 STARTTLS 中继默认握手失败（certificate 错误）、开启开关后完整 SMTP 流程成功（`mailer_test.go` 两个新测试）。
+
+### 10. 缺安全响应头（点击劫持/降级风险）
+
+- [x] 位置：`internal/web/middleware/security.go`（新中间件，全局注册）
+- 修复方案：
+  - [x] `Strict-Transport-Security: max-age=31536000; includeSubDomains`
+  - [x] `X-Frame-Options: DENY` + CSP `frame-ancestors 'none'`（点击劫持）
+  - [x] `X-Content-Type-Options: nosniff`
+  - [x] `Referrer-Policy: strict-origin-when-cross-origin`
+  - [x] 基础 CSP：`default-src 'self'` + 放宽项（内联脚本/样式必须 unsafe-inline；`img-src https:` 允许邮件远程图片；`connect-src 'self'`/`form-action 'self'` 防数据外泄）。CSP 具体策略在 `security.go` 顶部注释说明。
+- 验证：
+  - [x] 单测：5 个头均存在，关键值抽查（`security_test.go`）。
+  - [ ] 线上回归：登录/收件箱/管理页功能不受 CSP 影响；邮件远程图片正常加载。
+
+### 11. LDAP/OAuth 错误信息泄露与用户枚举
+
+- [x] 位置：`internal/web/handlers/auth.go`
+- 修复方案：
+  - [x] 错误提示统一为通用文案（"LDAP 认证失败…"、"LDAP 账号未接入本系统…"、"OAuth2 认证失败…"），原始 err 只写日志，不回显页面；不再在提示中回显用户邮箱。
+- 验证：
+  - [x] 现有 OAuth2 测试仍通过（错误页文案不含内部细节）。
+  - [ ] 线上（启用 LDAP/OAuth 后）验证失败页面不含内部地址/DN/原始错误串。
+
+## P3 低危 / 加固
+
+### 12. Referer 开放重定向
+
+- [ ] 位置：`internal/web/handlers/mail.go:567-571、591-595`
+- [ ] 修复：仅接受以 `/` 开头且非 `//` 的相对路径 Referer，否则回退 `/inbox`。
+
+### 13. Web 发信配额检查 TOCTOU
+
+- [ ] 位置：`internal/web/handlers/mail.go:209-263`
+- [ ] 修复：配额检查与 `UpdateUsedBytes` 改为单条原子 SQL（`WHERE used_bytes + ? <= quota_bytes` 式更新），失败即拒发。
+
+### 14. compose 页 safeJS 在 JS 上下文绕过转义（自 XSS）
+
+- [ ] 位置：`internal/web/templates/compose.html:80`
+- [ ] 修复：改为 `quill.root.innerHTML = {{.bodyContent | jsonify}};`（模板函数内用 `json.Marshal` 输出 JS 字符串字面量）。
+- [ ] 顺手评估移除 `templateFuncs` 中不再使用的 `safeHTML`，缩小危险面。
+
+### 15. Content-Disposition 文件名未编码
+
+- [ ] 位置：`internal/web/handlers/mail.go:626`、`internal/web/handlers/admin.go:863`
+- [ ] 修复：与 #4 一并改用 `mime.FormatMediaType`（RFC 5987 `filename*=`）。
+
+### 16. 会话治理
+
+- [ ] 登录成功后调用 `session.Clear()` 再写入新值（清掉可能的旧状态）。
+- [ ] 会话固定时长 24h 无任何续期/空闲过期策略，考虑加滑动过期与绝对过期。
+
+## 已确认安全、无需改动
+
+- bcrypt 密码哈希；GORM 全参数化查询（无 SQL 注入）。
+- SMTP 非开放中继、认证用户强制 From=登录身份。
+- LDAP 过滤器已 `EscapeFilter`。
+- 邮件 HTML 经 sandbox iframe（无 `allow-scripts`）渲染，`srcdoc` 属性转义经实测有效，无存储型 XSS。
+- Web 登录错误提示不区分用户是否存在（无枚举）。
+
+## 修复顺序建议
+
+1. ~~#1（P0）~~ 已完成 2026-08-19
+2. ~~#2、#3、#4（P1）~~ 已完成 2026-08-19
+3. ~~#5-#11（P2）~~ 已完成 2026-08-19
+4. 其余 P3 项随版本迭代
Author	SHA1	Message	Date
wuwenfengmi1998	8cfeb43c6a	docs: 新增移动端界面截图（响应式布局）	2026-08-19 16:48:26 +08:00
kevin	3f28ec20f4	fix(security): 修复 P2 中危项（cookie/协议限速/路径遍历/默认口令/中继TLS/安全头/信息泄露） - 会话 cookie 增加 Secure 标志；新增 [web].cookie_secure 配置（默认 true，仅本地 HTTP 调试关闭；缺失字段按安全默认处理） - SMTP/IMAP/POP3 认证接入封禁体系（store.RecordAuthFailure 与 Web 共用 ban_entries）：失败计数达 ban.max_fail_attempts 即封禁 IP，已封禁 IP 拒绝认证，堵住协议层暴力破解 - 附件存储路径遍历防护重写：FullPath 白名单校验（UUID 文件名格式） + baseDir 前缀兜底，非法路径返回错误；Save 扩展名白名单化 - 初始管理员不再使用 admin/admin：密码取 MAILGO_ADMIN_PASSWORD 或随机生成并打印一次；新增 MustChangePassword 首登强制改密（管理员重置密码同样触发） - 外发中继默认验证 TLS 证书（保护 AUTH 凭据，防 MITM），直投 MX 保持机会式 TLS；新增 outbound.relay_tls_insecure 开关（默认 false） - 新增安全响应头中间件：HSTS、X-Frame-Options DENY、nosniff、 Referrer-Policy、基础 CSP（frame-ancestors 'none' 防点击劫持， connect-src/form-action 'self' 防数据外泄） - LDAP/OAuth 登录错误统一为通用文案，原始错误只写日志，不再回显邮箱/内部细节（防用户枚举与信息泄露） - 新增 25 个回归测试：cookie 标志、封禁阈值、路径遍历用例、中继 TLS 验证（自签证书 STARTTLS 集成）、安全头、OAuth 文案部署注意：升级后所有会话失效需重新登录；若直接以 HTTP 提供服务需显式配置 cookie_secure = false。	2026-08-19 16:45:21 +08:00
kevin	c725d0b91e	fix(security): 修复 P1 高危项（OAuth2 state / 伪造客户端IP / CRLF 邮件头注入） - OAuth2: state 改为 crypto/rand 随机值并写入独立短期 cookie （主会话为 SameSite=Strict，跨站回调不携带，不能放主会话）；回调用 ConstantTimeCompare 校验 state，缺失/不匹配返回 403，校验后立即清除保证一次性使用。原硬编码 mailgo_oauth2_state 可被利用做授权码注入/登录 CSRF。 - 代理信任: engine.SetTrustedProxies 仅信任 127.0.0.1/::1。外部直连时 X-Forwarded-For 完全不可信，防止伪造客户端 IP 绕过登录封禁或恶意封禁他人；本机 Caddy/Nginx 转发不受影响。 - CRLF 注入: Web 写信的 To/Cc/Subject 及附件文件名不再原样拼入 MIME 头。新增 sanitizeHeaderField（strip CR/LF/NUL）、 subject 按 RFC 2047 编码、附件名用 mime.FormatMediaType （RFC 2231）；附件下载的 Content-Disposition 同步修复。消息构建抽为 buildOutgoingMessage 纯函数便于测试。 - test: 新增 13 个回归测试（trustedproxy / mail_injection / oauth2_state），覆盖伪造 XFF、注入载荷、state 校验全部分支。	2026-08-19 16:31:25 +08:00
kevin	551ed981de	fix(security): 会话密钥改为随机生成，修复硬编码密钥可伪造管理员会话安全审计 P0 修复：旧版会话签名密钥硬编码在源码中（源码公开即泄露），任何人可据此伪造 isAdmin 会话接管后台。 - config: 新增 [web].secret_key，首启/升级时用 crypto/rand 自动生成 32 字节随机密钥并持久化；旧硬编码值自动替换 - config: 支持 MAILGO_SECRET_KEY 环境变量覆盖（覆盖值不落盘） - config: 配置文件权限收紧为 0600（同时保护 relay_password 等敏感字段） - web: NewWebServer 校验密钥（空/旧默认值/短于16字节拒绝启动） - test: 伪造会话拒绝、密钥生命周期（生成/持久化/重启稳定/env不落盘）等 9 个测试 - docs: README 配置参考、security_todo.md 安全修复清单部署注意：升级重启后所有用户需重新登录。	2026-08-19 16:21:28 +08:00
kevin	6484af7e63	Merge pull request 'fix: 返回列表后未读邮件状态不更新（BFCache 静默同步）' (#9 ) from dsh/mailgo:fix/unread-status-bfcache into main Reviewed-on: kevin/mailgo#9	2026-08-17 23:18:30 -04:00
dsh	bf283ba5fc	fix: 返回列表后未读邮件状态不更新（BFCache 静默同步）问题：打开未读邮件（阅读页已自动标记已读）后返回列表，浏览器从 BFCache 恢复旧 DOM，列表仍显示未读，需手动刷新。修复： - 三个列表页的交互脚本提取为公共模板 listjs（base.html），行为一致 - pageshow(persisted=true) 时静默 fetch 最新列表并局部更新行状态（未读类/圆点/已删除行/未读角标/总数），不整页刷新、保留滚动 - visibilitychange 兜底：标签页重新可见时也同步一次（离线失败静默忽略，仅 BFCache 场景失败才整页刷新） - 验证：合成 pageshow 事件驱动同步，未读->已读局部更新 PASS；桌面/移动/平板布局回归无异常	2026-08-17 23:08:15 -04:00
kevin	e3514246b0	Merge pull request 'feat: 前端移动端响应式适配' (#8 ) from dsh/mailgo:feature/mobile-responsive into main Reviewed-on: kevin/mailgo#8	2026-08-17 22:48:48 -04:00