如何解密 IdentityServer 返回的 id_token

问题:

园子的 open api 是基于 IdentityServer 实现的，通过下面的代码跳转到 Authorization Server 进行登录用户授权

public IActionResult Authorize()
{
    var url = QueryHelpers.AddQueryString(
        "https://oauth.cnblogs.com/connect/authorize",
        new Dictionary<string, string>
        {
            ["client_id"] = _apiOptions.ClientId,
            ["scope"] = "openid profile CnBlogsApi offline_access",
            ["response_type"] = "code id_token",
            ["redirect_uri"] = _apiOptions.RedirectUri,
            ["state"] = "cnblogs open api",
            ["nonce"] = Guid.NewGuid().ToString(),
            ["response_mode"] = "form_post"
        });

    return Redirect(url);
}

授权成功后拿到了 id_token

public IActionResult Callback(string code, string id_token, string scope, string state, string session_state)
{
    return Content(id_token);
}

请问如何解密这个 id_token ？

回答1:

不需要解密，只需解码，在 Decode JWTs in C# for Authorization 中找到了答案：

var jwt = "(the JTW here)";
var handler = new JwtSecurityTokenHandler();
var token = handler.ReadJwtToken(jwt);

试验的代码：

public IActionResult Callback(string code, string id_token, string scope, string state, string session_state)
{
    var handler = new JwtSecurityTokenHandler();
    var token = handler.ReadJwtToken(id_token);
    return Content(token.Issuer);
}

注：需要安装 nuget 包 System.IdentityModel.Tokens.Jwt