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透過 ASP.NET Core 寫一個簡易的 AD 帳號密碼驗證 Web API

　　最近試著透過 ASP.NET Core 寫一個 AD 帳密修改的程式，架構上大致是先有個 AD 驗證及些密碼修改的 Web API，最後再寫一個桌面應用程式，讓使用者自行修改。這次完成的是帳密驗證的 Web API，程式如下：

NuGet 安裝套件

System.DirectoryServices.Protocols (AD 套件)
Swashbuckle.AspNetCore (API 測試套件，或是在新增專案時，勾選 OpenAPI 亦可)

Controllers/PasswordValidationController.cs

using AD.Services;
using AD.Models;
using Microsoft.AspNetCore.Mvc;

namespace AD.Controllers
{
    [Route("Password-Validate")]
    [ApiController]

    public class PasswordValidationController : ControllerBase
    {
        private readonly UserPasswordService _userPassword;

        public PasswordValidationController(UserPasswordService userPassword)
        {
            _userPassword = userPassword;
        }

        [HttpPost("validate")]
        public IActionResult Validate([FromBody] LoginRequest request)
        {
            if (string.IsNullOrWhiteSpace(request.Username) || string.IsNullOrWhiteSpace(request.Password))
            {
                return BadRequest("使用者帳號或密碼不可為空白。");
            }

            var isValid = _userPassword.ValidatePassword(request.Username, request.Password);
            return isValid ? Ok("驗證成功。") : Unauthorized("驗證失敗。");
        }
    }
}

Services/UserPasswordService.cs

using System.DirectoryServices.Protocols;
using System.Net;

namespace AD.Services
{
    public class UserPasswordService
    {
        private readonly string _ldapServer;
        private readonly string _domain;

        public UserPasswordService(IOptions<LdapSettings> ldapSettings)
        {
            _ldapServer = ldapSettings.Value.Server;
            _domain = ldapSettings.Value.Domain;
        }

        public bool Validate(string username, string password)
        {
            try
            {
                var credentials = username;
                using var connection = new LdapConnection(new LdapDirectoryIdentifier(_ldapServer));
                connection.Credential = new NetworkCredential(username, password, _domain);
                connection.AuthType = AuthType.Negotiate; // 使用 Negotiate 會先嘗試 Kerberos，失敗再改試 NTLM。
                connection.Bind(); // 嘗試綁定，成功表示驗證通過
                return true;
            }
            catch (LdapException)
            {
                return false; // 驗證失敗
            }
        }
    }
}

Models/LoginRequestDTO.cs

namespace AD.Models
{
    public class LoginRequestDTO
    {
        public string Username { get; set; } // DTO (Data Transfer Object) 類型的屬性不需要初始化，因為它們的值由外部輸入資料 (例如 HTTP 請求) 決定。
        public string Password { get; set; }
    }
}

Models/LdapSettings.cs

namespace AD.Models
{
    public class LdapSettings
    {
        public string Server { get; set; } = string.Empty;
        public string Domain { get; set; } = string.Empty;
    }
}

appsettings.json

{
    "Logging": {
        "LogLevel": {
            "Default": "Information",
            "Microsoft.AspNetCore": "Warning"
        }
    },

    "AllowedHosts": "*",

    "LdapSettings": {
        "Server": "dc.abc.com.tw", // 如果是用 Kerberos 驗證，AD 的伺服器不可以使用 IP。
        "Domain": "abc"
    }
}

Program.cs

using AD.Models;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
builder.Services.Configure<LdapSettings>(builder.Configuration.GetSection("LdapSettings")); // 讀取 appsettings.json 的 LdapSettings 資料。
builder.Services.AddScoped<UserPasswordService>();

// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.

// 讓 Swagger 只在開發環境時使用。
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

要測試時，透過 Swagger，輸入帳號密碼測試即可。