如何产生JWT与谷歌OAuth2兼容的算法RSA SHA-256使用系统？IdentityModel.Tokens.Jwt？

Question

我尝试使用system . identity model . tokens . jwt创建一个JWT来授权一个服务帐户，如Google文档中所述。我有以下代码:

byte[] key = Convert.FromBase64String("...");
var certificate = new X509Certificate2(key, "notasecret");

DateTime now = DateTime.UtcNow;
TimeSpan span = now - UnixEpoch;
Claim[] claims =
{
    new Claim("iss", "[e-mail]"),
    new Claim("scope", "https://www.googleapis.com/auth/plus.me"),
    new Claim("aud", "https://accounts.google.com/o/oauth2/token"),
    new Claim("iat", span.TotalSeconds.ToString()),
    new Claim("exp", span.Add(TimeSpan.FromHours(1)).TotalSeconds.ToString())
};

JwtSecurityTokenHandler handler = new JwtSecurityTokenHandler();
var descriptor = new SecurityTokenDescriptor
{
    SigningCredentials = new SigningCredentials(
        new InMemorySymmetricSecurityKey(key),
        "http://www.w3.org/2001/04/xmldsig-more#hmac-sha256",
        "http://www.w3.org/2001/04/xmlenc#sha256"),
    Subject = new ClaimsIdentity(claims)
};

JwtSecurityToken jwtSecurityToken = (JwtSecurityToken)handler.CreateToken(descriptor);
string json = handler.WriteToken(jwtSecurityToken);

输出：

{ "typ" : "JWT" , "alg" : "HS256" }

虽然谷歌明确表示它支持SHA-256：

服务帐户依赖于RSA SHA-256算法和JWT令牌格式

根据wtSecurityTokenHandler.InboundAlgorithmMap：

RS256 => http://www.w3.org/2001/04/xmldsig-more#rsa-sha256
HS256 => http://www.w3.org/2001/04/xmldsig-more#hmac-sha256 

所以当我改变我的代码时:

new SigningCredentials(
    new InMemorySymmetricSecurityKey(key),
        "http://www.w3.org/2001/04/xmldsig-more#rsa-sha256",
        "http://www.w3.org/2001/04/xmlenc#sha256");

我得到了一个例外：

System.InvalidOperationException: IDX10632: SymmetricSecurityKey.GetKeyedHashAlgorithm( 'http://www.w3.org/2001/04/xmldsig-more#rsa-sha256' ) threw an exception.
SymmetricSecurityKey: 'System.IdentityModel.Tokens.InMemorySymmetricSecurityKey'
SignatureAlgorithm: 'http://www.w3.org/2001/04/xmldsig-more#rsa-sha256', check to make sure the SignatureAlgorithm is supported.

这是否意味着微软不支持谷歌独家支持的算法？

Answer 1

我不得不稍微修改@abatishchev的代码。否则，当部署到非开发环境中时，它在生成证书时会遇到问题。

问题有两个方面。如果证书未标记为可导出，它将引发异常，指出类似“keyset 不存在”的内容。它只会发生在服务器上，而不是在本地，所以我怀疑Windows的服务器版本更具限制性。

此外，由于证书是在用户密钥集中创建的，因此它将引发有关计算机信任问题的加密异常。我们的应用程序池设置为不导入高级选项中的用户配置文件，您可以这样做。但由于与其他应用程序的兼容性问题，这不是我们的选择。设置要在机器密钥集中创建的证书可以缓解此问题。

更改的2个部分标有注释。

private static async Task<string> GetAuthorizationToken(GoogleAuthOptions authOptions)
{
    string jwt = CreateJwt(authOptions);

    var dic = new Dictionary<string, string>
    {
        { "grant_type", "urn:ietf:params:oauth:grant-type:jwt-bearer" },
        { "assertion", jwt }
    };
    var content = new FormUrlEncodedContent(dic);

    var httpClient = new HttpClient { BaseAddress = new Uri("https://accounts.google.com") };
    var response = await httpClient.PostAsync("/o/oauth2/token", content);
    response.EnsureSuccessStatusCode();

    dynamic dyn = await response.Content.ReadAsAsync<dynamic>();
    return dyn.access_token;
}

private static readonly DateTime UnixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);

private static string CreateJwt(GoogleAuthOptions authOptions)
{
    /* changed */
    const X509KeyStorageFlags certificateFlags = X509KeyStorageFlags.MachineKeySet | X509KeyStorageFlags.PersistKeySet | X509KeyStorageFlags.Exportable;

    var certificate = new X509Certificate2(Convert.FromBase64String(authOptions.CertificateKey), authOptions.CertificateSecret, certificateFlags);
    /* end of change */

    DateTime now = DateTime.UtcNow;
    var claimset = new
    {
        iss = authOptions.Issuer,
        scope = "https://www.googleapis.com/auth/plus.me",
        aud = authOptions.Audience,
        iat = ((int)now.Subtract(UnixEpoch).TotalSeconds).ToString(CultureInfo.InvariantCulture),
        exp = ((int)now.AddMinutes(55).Subtract(UnixEpoch).TotalSeconds).ToString(CultureInfo.InvariantCulture)
    };

    // header
    var header = new { typ = "JWT", alg = "RS256" };

    // encoded header
    var headerSerialized = JsonConvert.SerializeObject(header);
    var headerBytes = Encoding.UTF8.GetBytes(headerSerialized);
    var headerEncoded = TextEncodings.Base64Url.Encode(headerBytes);

    // encoded claimset
    var claimsetSerialized = JsonConvert.SerializeObject(claimset);
    var claimsetBytes = Encoding.UTF8.GetBytes(claimsetSerialized);
    var claimsetEncoded = TextEncodings.Base64Url.Encode(claimsetBytes);

    // input
    var input = String.Join(".", headerEncoded, claimsetEncoded);
    var inputBytes = Encoding.UTF8.GetBytes(input);

    // signiture
    var rsa = (RSACryptoServiceProvider)certificate.PrivateKey;
    var cspParam = new CspParameters
    {
        KeyContainerName = rsa.CspKeyContainerInfo.KeyContainerName,
        /* changed */
        KeyNumber = (int) KeyNumber.Exchange,       
        Flags = CspProviderFlags.UseMachineKeyStore
        /* end of change */
    };
    var cryptoServiceProvider = new RSACryptoServiceProvider(cspParam) { PersistKeyInCsp = false };
    var signatureBytes = cryptoServiceProvider.SignData(inputBytes, "SHA256");
    var signatureEncoded = TextEncodings.Base64Url.Encode(signatureBytes);

    // jwt
    return String.Join(".", headerEncoded, claimsetEncoded, signatureEncoded);
}

Answer 2

private static async Task<string> GetAuthorizationToken(GoogleAuthOptions authOptions)
{
    string jwt = CreateJwt(authOptions);

    var dic = new Dictionary<string, string>
    {
        { "grant_type", "urn:ietf:params:oauth:grant-type:jwt-bearer" },
        { "assertion", jwt }
    };
    var content = new FormUrlEncodedContent(dic);

    var httpClient = new HttpClient { BaseAddress = new Uri("https://accounts.google.com") };
    var response = await httpClient.PostAsync("/o/oauth2/token", content);
    response.EnsureSuccessStatusCode();

    dynamic dyn = await response.Content.ReadAsAsync<dynamic>();
    return dyn.access_token;
}

private static readonly DateTime UnixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);

private static string CreateJwt(GoogleAuthOptions authOptions)
{
    var certificate = new X509Certificate2(Convert.FromBase64String(authOptions.CertificateKey), authOptions.CertificateSecret);

    DateTime now = DateTime.UtcNow;
    var claimset = new
    {
        iss = authOptions.Issuer,
        scope = "https://www.googleapis.com/auth/plus.me",
        aud = authOptions.Audience,
        iat = ((int)now.Subtract(UnixEpoch).TotalSeconds).ToString(CultureInfo.InvariantCulture),
        exp = ((int)now.AddMinutes(55).Subtract(UnixEpoch).TotalSeconds).ToString(CultureInfo.InvariantCulture)
    };

    // header
    var header = new { typ = "JWT", alg = "RS256" };

    // encoded header
    var headerSerialized = JsonConvert.SerializeObject(header);
    var headerBytes = Encoding.UTF8.GetBytes(headerSerialized);
    var headerEncoded = TextEncodings.Base64Url.Encode(headerBytes);

    // encoded claimset
    var claimsetSerialized = JsonConvert.SerializeObject(claimset);
    var claimsetBytes = Encoding.UTF8.GetBytes(claimsetSerialized);
    var claimsetEncoded = TextEncodings.Base64Url.Encode(claimsetBytes);

    // input
    var input = String.Join(".", headerEncoded, claimsetEncoded);
    var inputBytes = Encoding.UTF8.GetBytes(input);

    // signiture
    var rsa = (RSACryptoServiceProvider)certificate.PrivateKey;
    var cspParam = new CspParameters
    {
        KeyContainerName = rsa.CspKeyContainerInfo.KeyContainerName,
        KeyNumber = rsa.CspKeyContainerInfo.KeyNumber == KeyNumber.Exchange ? 1 : 2
    };
    var cryptoServiceProvider = new RSACryptoServiceProvider(cspParam) { PersistKeyInCsp = false };
    var signatureBytes = cryptoServiceProvider.SignData(inputBytes, "SHA256");
    var signatureEncoded = TextEncodings.Base64Url.Encode(signatureBytes);

    // jwt
    return String.Join(".", headerEncoded, claimsetEncoded, signatureEncoded);
}

Answer 3

这个问题已经问了一段时间了，但我认为，对于未来的用户来说，使用.NET Google Auth API（其nuget可在此处获得：Google.API.Auth）在几行代码中获得相同的结果可能非常容易

using System.Security.Cryptography.X509Certificates;
using System.Threading;
using System.Threading.Tasks;
using Google.Apis.Auth.OAuth2;

namespace GoogleTest
{
    public class GoogleOAuth2
    {
        /// <summary>
        /// Authorization scope for our requests
        /// </summary>
        private readonly string _defaultScope;

        /// <summary>
        /// Service account will be of the form [e-mail]
        /// </summary>
        private readonly string _serviceAccount;

        /// <summary>
        /// Set this to the full path to your service account private key file.
        /// </summary>
        private readonly string _certificateFile;

        public GoogleOAuth2(string defaultScope, string serviceAccount, string certificateFile)
        {
            _defaultScope = defaultScope;
            _serviceAccount = serviceAccount;
            _certificateFile = certificateFile;
        }

        /// <summary>
        /// Access Token returned by Google Token Server
        /// </summary>
        public string AccessToken { get; set; }

        public async Task<bool> RequestAccessTokenAsync()
        {
            var certificate = new X509Certificate2(_certificateFile, "notasecret", X509KeyStorageFlags.Exportable);
            var serviceAccountCredential = new ServiceAccountCredential(new ServiceAccountCredential.Initializer(_serviceAccount)
            {
                Scopes = new[] { _defaultScope }
            }.FromCertificate(certificate));

            var status = await serviceAccountCredential.RequestAccessTokenAsync(CancellationToken.None);
            if (status)
                AccessToken = serviceAccountCredential.Token.AccessToken;
            return status;
        }
    }
}

要获取访问令牌，您只需调用方法RequestAccessTokenAsync，如果结果成功，则在AccessTown属性中获得令牌。

注意，此实现假设在开发人员控制台中，您已将私钥导出为.P12文件。

希望这个答案会有所帮助。