IdentityServer4 实现自定义 GrantType 授权模式

OAuth 2.0 默认四种授权模式（GrantType）：

• 授权码模式（authorization_code）
• 简化模式（implicit）
• 密码模式（password）
• 客户端模式（client_credentials）

使用 IdentityServer4，我们可以自定义授权模式吗？答案是可以的，比如我们自定义实现一个anonymous授权模式（匿名访问）。

创建AnonymousGrantValidator（继承IExtensionGrantValidator）：

public class AnonymousGrantValidator : IExtensionGrantValidator
{
    private readonly ITokenValidator _validator;

    public AnonymousGrantValidator(ITokenValidator validator)
    {
        _validator = validator;
    }

    public string GrantType => "anonymous";

    public async Task ValidateAsync(ExtensionGrantValidationContext context)
    {
        //var userToken = context.Request.Raw.Get("token");

        //if (string.IsNullOrEmpty(userToken))
        //{
        //    context.Result = new GrantValidationResult(TokenRequestErrors.InvalidGrant);
        //    return;
        //}

        //var result = await _validator.ValidateAccessTokenAsync(userToken);
        //if (result.IsError)
        //{
        //    context.Result = new GrantValidationResult(TokenRequestErrors.InvalidGrant);
        //    return;
        //}

        // get user's identity
        //var sub = result.Claims.FirstOrDefault(c => c.Type == "sub").Value;

        var claims = new List<Claim>() { new Claim("role", GrantType) }; // Claim 用于配置服务站点 [Authorize("anonymous")]
        context.Result = new GrantValidationResult(GrantType, GrantType, claims);
    }
}

修改Client配置：

new Client
{
    ClientId = "client1",
    AllowedGrantTypes = GrantTypes.List(GrantTypes.ResourceOwnerPassword.FirstOrDefault(), "anonymous"), //一个 Client 可以配置多个 GrantType
    AllowOfflineAccess = true,
    AccessTokenLifetime = 3600 * 6, //6小时
    SlidingRefreshTokenLifetime = 1296000, //15天
    ClientSecrets =
    {
        new Secret("123".Sha256())
    },
    AllowedScopes = new List<string>
    {
        "api2"
    }
}

DI 增加注入对象：

builder.AddExtensionGrantValidator<AnonymousGrantValidator>();

调用示例代码：

public async Task<TokenResponse> AnonymousAsync(string userToken)
{
    var payload = new
    {
        token = userToken
    };

    // create token client
    var client = new TokenClient(disco.TokenEndpoint, "client1", "123");

    // send custom grant to token endpoint, return response
    return await client.RequestCustomGrantAsync("anonymous", "api2", payload);
}

Http 访问示例：

POST /connect/token

grant_type=anonymous&
scope=api2&
token=...&
client_id=api1.client
client_secret=secret

参考资料：

• Extension Grants