feat(admin): add administrator sessions

admin/internal/config/config.go

@@ -0,0 +1,84 @@
+// Package config 读取采购服务的启动配置。凭据只允许来自显式环境变量，避免把秘密写入代码或仓库。
+package config
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+
+	"golang.org/x/crypto/bcrypt"
+)
+
+const (
+	adminUsernameEnv       = "CMBUYER_ADMIN_USERNAME"
+	adminPasswordBcryptEnv = "CMBUYER_ADMIN_PASSWORD_BCRYPT"
+	sessionSecretEnv       = "CMBUYER_SESSION_SECRET"
+	cookieSecureEnv        = "CMBUYER_COOKIE_SECURE"
+	minimumSecretLength    = 32
+)
+
+// Config 是启动采购服务所需的最小安全配置。
+type Config struct {
+	AdminUsername       string
+	AdminPasswordBcrypt string
+	SessionSecret       []byte
+	CookieSecure        bool
+}
+
+// LoadFromEnv 从进程环境读取配置。错误只指出缺失或非法的变量名，绝不回显秘密。
+func LoadFromEnv() (Config, error) {
+	return Load(os.LookupEnv)
+}
+
+// Load 使用 lookup 读取配置，以便在不污染进程环境的情况下测试启动边界。
+func Load(lookup func(string) (string, bool)) (Config, error) {
+	username, err := required(lookup, adminUsernameEnv)
+	if err != nil {
+		return Config{}, err
+	}
+
+	passwordHash, err := required(lookup, adminPasswordBcryptEnv)
+	if err != nil {
+		return Config{}, err
+	}
+	if _, err := bcrypt.Cost([]byte(passwordHash)); err != nil {
+		return Config{}, fmt.Errorf("%s is not a valid bcrypt hash", adminPasswordBcryptEnv)
+	}
+
+	secret, err := required(lookup, sessionSecretEnv)
+	if err != nil {
+		return Config{}, err
+	}
+	if len([]byte(secret)) < minimumSecretLength {
+		return Config{}, fmt.Errorf("%s must be at least %d bytes", sessionSecretEnv, minimumSecretLength)
+	}
+
+	cookieSecure := false
+	if value, present := lookup(cookieSecureEnv); present {
+		switch value {
+		case "true":
+			cookieSecure = true
+		case "false":
+			cookieSecure = false
+		default:
+			return Config{}, fmt.Errorf("%s must be exactly true or false", cookieSecureEnv)
+		}
+	}
+
+	return Config{
+		AdminUsername:       username,
+		AdminPasswordBcrypt: passwordHash,
+		SessionSecret:       []byte(secret),
+		CookieSecure:        cookieSecure,
+	}, nil
+}
+
+func required(lookup func(string) (string, bool), name string) (string, error) {
+	value, present := lookup(name)
+	if !present || strings.TrimSpace(value) == "" {
+		return "", errors.New(name + " must be set")
+	}
+
+	return value, nil
+}