Claim

• 一部分信息
• Name-Value
• 可以来自内部或外部
• 基于策略的（Policy）

Docs：Claims-based authorization in ASP.NET Core

UserController 中操作 Claim

User 与 Claim 的关系类似与 User 与 Role 的关系。

public async Task<IActionResult> ManageClaims(string id)
{
    var user = await _userManager.Users.Include(x => x.Claims)
        .Where(x => x.Id == id).SingleOrDefaultAsync();
    if (user == null)
    {
        return RedirectToAction("Index");
    }
    // 筛选出该 User 没有的 Claim
    var leftClaims = ClaimTypes.AllClaimTypeList.Except(user.Claims.Select(x => x.ClaimType)).ToList();
    var vm = new ManageClaimsViewModel
    {
        UserId = id,
        AvailableClaims = leftClaims
    };
    return View(vm);
}
[HttpPost]
public async Task<IActionResult> ManageClaims(ManageClaimsViewModel vm)
{
    var user = await _userManager.FindByIdAsync(vm.UserId);
    if (user == null)
    {
        return RedirectToAction("Index");
    }
    var claim = new IdentityUserClaim<string>
    {
        ClaimType = vm.ClaimId,
        ClaimValue = vm.ClaimId
    };
    user.Claims.Add(claim);
    var result = await _userManager.UpdateAsync(user);
    if (result.Succeeded)
    {
        return RedirectToAction("EditUser", new { id = vm.UserId });
    }
    ModelState.AddModelError(string.Empty, "编辑用户Claims时发生错误");
    return View(vm);
}
[HttpPost]
public async Task<IActionResult> RemoveClaim(string id, string claim)
{
    var user = await _userManager.Users.Include(x => x.Claims)
        .Where(x => x.Id == id).SingleOrDefaultAsync();
    if (user == null)
    {
        return RedirectToAction("Index");
    }
    var claims = user.Claims.Where(x => x.ClaimType == claim).ToList();
    foreach (var c in claims)
    {
        user.Claims.Remove(c);
    }
    var result = await _userManager.UpdateAsync(user);
    if (result.Succeeded)
    {
        return RedirectToAction("EditUser", new { id });
    }
    ModelState.AddModelError(string.Empty, "编辑用户Claims时发生错误");
    return RedirectToAction("ManageClaims", new { id });
}

Policy（策略）

• 注册 Policy
• 使用 Policy 进行授权

Docs：Policy-based authorization in ASP.NET Core

添加策略

通过 Role 和 Claim 添加策略：

services.AddAuthorization(options =>
{
    options.AddPolicy("仅限管理员", policy => policy.RequireRole("Administrators"));
    options.AddPolicy("编辑专辑", policy=> policy.RequireClaim("Edit Albums"));
});

两个注意事项

1. 如果登录账号时抛出 No IUserTokenProvider is registered 异常，可以通过 AddDefaultTokenProviders() 解决
2. 修改用户的 Claim 后，需重新登录才能生效。如果不想重新登录，可以通过 RefreshSignInAsync 解决
   1. PS：这会带来一些别的问题 Update user claims without updating authentication time