如何在C#中正确使用OpenID Connect jwks_uri元数据？

Question

每个OpenID Connect提供程序都会发布包含jwks_uri属性的发现文档.从这里返回的数据jwks_uri似乎有两种不同的形式.一个表单包含名为x5c和的字段x5t.这样的一个例子如下:

{
    "keys": [
        {
            "kty": "RSA",
            "use": "sig",
            "kid": "C61F8F2524D080D0DB0A508747A94C2161DEDAC8",
            "x5t": "xh-PJSTQgNDbClCHR6lMIWHe2sg", <------ HERE
            "e": "AQAB",
            "n": "lueb...",
            "x5c": [
                "MIIC/..." <------ HERE
            ],
            "alg": "RS256"
        }
    ]
}

我看到的另一个版本省略了x5c和x5t属性但包含e和n.一个例子是:

{
    "keys": [
        {
            "kty": "RSA",
            "alg": "RS256",
            "use": "sig",
            "kid": "cb11e2f233aee0329a5344570349cddb6b8ff252",
            "n": "sJ46h...", <------ HERE
            "e": "AQAB"      <------ HERE
        }
    ]
}

我不太明白区别是什么,为什么有时会使用x5c/x5t组合,但有时候只是简单e/n.我正在使用C#Microsoft.IdentityModel.Tokens.TokenValidationParameters,我正在试图找出如何供应该物业IssuerSigningKey.此类的示例用法是

new TokenValidationParameters
{
    ValidateAudience = true,
    ValidateIssuer = true,
    ...,
    IssuerSigningKey = new X509SecurityKey(???) or new JsonWebKey(???) //How to create this based on x5c/x5t and also how to create this based on e and n ?
}

鉴于两种不同的JWK元数据格式,我如何使用它们来提供IssuerSigningKey,TokenValidationParameter以便我可以验证访问令牌？

Answer 1

这就是我最终的目的:

//Model the JSON Web Key Set
public class JsonWebKeySet
{
     [JsonProperty(DefaultValueHandling = DefaultValueHandling.Ignore, NullValueHandling = NullValueHandling.Ignore, PropertyName = "keys", Required = Required.Default)]
     public JsonWebKey[] Keys { get; set; }
}


//Model the JSON Web Key object
public class JsonWebKey
{
    [JsonProperty(DefaultValueHandling = DefaultValueHandling.Ignore, NullValueHandling = NullValueHandling.Ignore, PropertyName = "kty", Required = Required.Default)]
    public string Kty { get; set; }

    [JsonProperty(DefaultValueHandling = DefaultValueHandling.Ignore, NullValueHandling = NullValueHandling.Ignore, PropertyName = "use", Required = Required.Default)]
    public string Use { get; set; }

    [JsonProperty(DefaultValueHandling = DefaultValueHandling.Ignore, NullValueHandling = NullValueHandling.Ignore, PropertyName = "kid", Required = Required.Default)]
    public string Kid { get; set; }

    [JsonProperty(DefaultValueHandling = DefaultValueHandling.Ignore, NullValueHandling = NullValueHandling.Ignore, PropertyName = "x5t", Required = Required.Default)]
    public string X5T { get; set; }

    [JsonProperty(DefaultValueHandling = DefaultValueHandling.Ignore, NullValueHandling = NullValueHandling.Ignore, PropertyName = "e", Required = Required.Default)]
    public string E { get; set; }

    [JsonProperty(DefaultValueHandling = DefaultValueHandling.Ignore, NullValueHandling = NullValueHandling.Ignore, PropertyName = "n", Required = Required.Default)]
    public string N { get; set; }

    [JsonProperty(DefaultValueHandling = DefaultValueHandling.Ignore, NullValueHandling = NullValueHandling.Ignore, PropertyName = "x5c", Required = Required.Default)]
    public string[] X5C { get; set; }

    [JsonProperty(DefaultValueHandling = DefaultValueHandling.Ignore, NullValueHandling = NullValueHandling.Ignore, PropertyName = "alg", Required = Required.Default)]
    public string Alg { get; set; }
}

我首先jwks_uri向OpenID Connect发现文档中提供的端点发出请求.请求将相应地填充上述对象.然后我将JsonWebKeySet对象传递给创建一个的方法ClaimsPrincipal

string idToken = "<the id_token that was returned from the Token endpoint>";
List<SecurityKey> keys = this.GetSecurityKeys(jsonWebKeySet);
var parameters = new TokenValidationParameters
                 {
                      ValidateAudience = true,
                      ValidAudience = tokenValidationParams.Audience,
                      ValidateIssuer = true,
                      ValidIssuer = tokenValidationParams.Issuer,
                      ValidateIssuerSigningKey = true,
                      IssuerSigningKeys = keys,
                      NameClaimType = NameClaimType,
                      RoleClaimType = RoleClaimType
                  };

 var handler = new JwtSecurityTokenHandler();
 handler.InboundClaimTypeMap.Clear();

 SecurityToken jwt;
 ClaimsPrincipal claimsPrincipal = handler.ValidateToken(idToken, parameters, out jwt);

 // validate nonce
 var nonceClaim = claimsPrincipal.FindFirst("nonce")?.Value ?? string.Empty;

 if (!string.Equals(nonceClaim, "<add nonce value here>", StringComparison.Ordinal))
 {
      throw new AuthException("An error occurred during the authentication process - invalid nonce parameter");
 }

 return claimsPrincipal;

该GetSecurityKeys方法是这样实现的

private List<SecurityKey> GetSecurityKeys(JsonWebKeySet jsonWebKeySet)
{
      var keys = new List<SecurityKey>();

      foreach (var key in jsonWebKeySet.Keys)
      {
          if (key.Kty == OpenIdConnectConstants.Rsa)
          {
             if (key.X5C != null && key.X5C.Length > 0)
             {
                string certificateString = key.X5C[0];
                var certificate = new X509Certificate2(Convert.FromBase64String(certificateString));

                var x509SecurityKey = new X509SecurityKey(certificate)
                                      {
                                          KeyId = key.Kid
                                      };

                 keys.Add(x509SecurityKey);
              }
              else if (!string.IsNullOrWhiteSpace(key.E) && !string.IsNullOrWhiteSpace(key.N))
              {
                  byte[] exponent = Base64UrlUtility.Decode(key.E);
                  byte[] modulus = Base64UrlUtility.Decode(key.N);

                  var rsaParameters = new RSAParameters
                                      {
                                          Exponent = exponent,
                                          Modulus = modulus
                                      };

                  var rsaSecurityKey = new RsaSecurityKey(rsaParameters)
                                       {
                                           KeyId = key.Kid
                                       };

                  keys.Add(rsaSecurityKey);
              }
              else
              {
                  throw new PlatformAuthException("JWK data is missing in token validation");
              }
          }
          else
          {
              throw new NotImplementedException("Only RSA key type is implemented for token validation");
          }
      }

      return keys;
  }

Answer 2

一些更新 - Microsoft.IdentityModel.Tokens nuget包含JsonWebKey 以及采用 jwk JSON 字符串的构造函数。

// JSON class
public class OpenIdConnectKeyCollection
{
    [JsonProperty("keys")]
    public ICollection<JToken> JsonWebKeys { get; set; }
}  
  
// map the keys using the JSON ctor
var jsonKeys = keysResp.JsonWebKeys;
var jwk = jsonKeys
    .Select(k => new JsonWebKey(k.ToString()))
    .ToList();

Answer 3

RSA公钥将始终至少包含成员kty（具有value RSA）n和e（AQAB即，几乎所有密钥的65537公有指数）。

其他成员是可选的，用于提供有关密钥的信息。通常，您会发现以下推荐成员：

• 其ID（kid），
• 使用方法（签名或加密）
• 它们设计用于什么算法（RS256在您的示例中）。

当密钥来自X.509证书时，通常会找到x5t或x5t#256（分别为sha1和sha256证书指纹）。某些系统无法直接使用JWK，并且提供了PKCS＃1密钥（x5c成员）。

您可以使用（n，e）对或x5c成员（如果提供）。这取决于您使用的库/第三方应用程序的功能。