如何在 dotnet core 中验证非对称签名的 JWT？

Question

我找到了 .NET FW 中的非对称签名示例和 .NET Core 中的对称签名示例，但我无法弄清楚如何在 .NET Core 中非对称地验证 JWT。给定 JWK 集的 URL 或给定的 public 密钥，我如何在 .NET Core 中验证令牌？

Answer 1

非对称签名和对称签名之间的唯一区别是签名密钥。只需为令牌验证参数构造一个新的非对称安全密钥即可。

假设您想使用 RSA 算法。让我们使用 powershell 导出一对 RSA 密钥，如下所示：

$rsa = New-Object System.Security.Cryptography.RSACryptoServiceProvider -ArgumentList 2048

$rsa.ToXmlString($true) | Out-File key.private.xml
$rsa.ToXmlString($false) | Out-File key.public.xml

现在我们将使用这两个密钥对令牌进行签名。

一点补丁

由于.NET Core 支持rsa.FromXmlString() api，我只是复制@myloveCc's code 在C# 中构造一个RsaParameters（这项工作由以下完成ParseXmlString() 方法):

public static class KeyHelper 
{
    public static RSAParameters ParseXmlString( string xml){
        RSAParameters parameters = new RSAParameters();

        System.Xml.XmlDocument xmlDoc = new System.Xml.XmlDocument();
        xmlDoc.LoadXml(xml);

        if (xmlDoc.DocumentElement.Name.Equals("RSAKeyValue"))
        {
            foreach (System.Xml.XmlNode node in xmlDoc.DocumentElement.ChildNodes)
            {
                switch (node.Name)
                {
                    case "Modulus": parameters.Modulus = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                    case "Exponent": parameters.Exponent = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                    case "P": parameters.P = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                    case "Q": parameters.Q = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                    case "DP": parameters.DP = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                    case "DQ": parameters.DQ = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                    case "InverseQ": parameters.InverseQ = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                    case "D": parameters.D = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                }
            }
        }
        else
        {
            throw new Exception("Invalid XML RSA key.");
        }
        return parameters;
    }


    public static RsaSecurityKey BuildRsaSigningKey(string xml){ 
        var parameters = ParseXmlString(xml);
        var rsaProvider = new RSACryptoServiceProvider(2048);
        rsaProvider.ImportParameters(parameters);
        var key = new RsaSecurityKey(rsaProvider);   
        return key;
    }  
}

这里我添加了一个BuildRsaSigningKey()辅助方法来生成一个SecurityKey.

令牌生成

这是一个使用 RSA 生成令牌的演示：


public string GenerateToken(DateTime expiry)
{
    var tokenHandler = new JwtSecurityTokenHandler();
    var Identity = new ClaimsIdentity(new[]
    {
        new Claim(ClaimTypes.Name,          "..."),
        // ... other claims
   });

    var xml = "<RSAKeyValue> load...from..local...files...</RSAKeyValue>";
    SecurityKey key =  KeyHelper.BuildRsaSigningKey(xml); 

    var Token = new JwtSecurityToken
    (
        issuer: "test",
        audience: "test-app",
        claims: Identity.Claims,
        notBefore: DateTime.UtcNow,
        expires: expiry,
        signingCredentials: new SigningCredentials(key, SecurityAlgorithms.RsaSha256Signature, SecurityAlgorithms.Sha256Digest)
    );
    var TokenString = tokenHandler.WriteToken(Token);
    return TokenString;
}

令牌验证

要自动验证它，请按如下方式配置 JWT Bearer 身份验证：

Services.AddAuthentication(A =>
{
    A.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
    A.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
})
.AddJwtBearer(O =>
{
    var xml = "<RSAKeyValue> load...from..local...files...</RSAKeyValue>";
    var key = KeyHelper.BuildRsaSigningKey(xml);

    O.RequireHttpsMetadata = false;
    O.SaveToken = true;
    O.IncludeErrorDetails = true;
    O.TokenValidationParameters = new TokenValidationParameters
    {
        IssuerSigningKey = key,
        ValidateIssuerSigningKey = true,
        ValidateLifetime = true,   
        // ... other settings
    };
});

如果您想手动验证它：

public IActionResult ValidateTokenManually(string jwt)
{
    var xml = "<RSAKeyValue>... the keys ...</RSAKeyValue>";
    SecurityKey key = KeyHelper.BuildRsaSigningKey(xml);    

    var validationParameters = new TokenValidationParameters
    {
        IssuerSigningKey = key,
        RequireSignedTokens = true,
        RequireExpirationTime = true,
        ValidateLifetime = true,
        // ... other settings
    };

    var tokenHandler = new JwtSecurityTokenHandler();
    var principal = tokenHandler.ValidateToken(jwt, validationParameters, out var rawValidatedToken);
    var securityToken = (JwtSecurityToken)rawValidatedToken;
    return Ok(principal);
}

Answer 2

我最终实现了 OpenID Connect Discovery 规范，它允许您以标准格式发布令牌端点和密钥集端点。然后我可以使用 AddJwtBearer() AuthenticationBuilder 扩展方法来自动缓存密钥集、验证令牌并填充 ClaimsPrincipal.

要编写您自己的实施 OpenID Connect 发现协议的令牌服务，您需要：

实施路由 /keys 服务于派生自您的 pfx 证书的 Microsoft.IdentityModel.Tokens.JsonWebKeySet 对象。

JsonWebKeySet GetJwksFromCertificates(IEnumerable<X509Certificate2> certificates)
{
    var jwks = new JsonWebKeySet();

    foreach (var certificate in certificates)
    {
        var rsaParameters = ((RSA)certificate.PublicKey.Key).ExportParameters(false);

        var jwk = new JsonWebKey
        {
            // https://tools.ietf.org/html/rfc7517#section-4
            Kty = certificate.PublicKey.Key.KeyExchangeAlgorithm,
            Use = "sig",
            Kid = certificate.Thumbprint,
            X5t = certificate.Thumbprint,

            // https://tools.ietf.org/html/rfc7517#appendix-B
            N = Convert.ToBase64String(rsaParameters.Modulus),
            E = Convert.ToBase64String(rsaParameters.Exponent),
        };

        jwks.Keys.Add(jwk);
    }

     return jwks;
}

实现 /not-yet-implemented returns 501 Not Implemented 的路由。

实施服务于 Microsoft.IdentityModel.Protocols.OpenIdConnect.OpenIdConnectConfiguration 对象的路由 /.well-known/openid-configuration。

OpenIdConnectConfiguration GetOpenIdConnectConfiguration(string issuer) {
    var configuration = new OpenIdConnectConfiguration
    {
        Issuer = issuer,
        TokenEndpoint = issuer + "/token",
        AuthorizationEndpoint = issuer + "/not-yet-implemented",
        JwksUri = issuer + "/keys",
    };
    configuration.GrantTypesSupported.Add(grantType);
    return configuration;
}

实施路由 /token，使用您的应用程序特定逻辑来验证用户并生成 ClaimsIdentity，然后使用 [= 创建 System.IdentityModel.Tokens.Jwt.JwtSecurityToken 25=].

JwtSecurityToken CreateJwt(
    string issuer,
    TimeSpan lifetime,
    ClaimsIdentity claimsIdentity,
    X509Certificate2 signingCertificate)
{
    var tokenDescriptor = new SecurityTokenDescriptor
    {
        Issuer = issuer,
        Expires = DateTime.UtcNow.Add(lifetime),
        NotBefore = DateTime.UtcNow,
        Subject = claimsIdentity,
        SigningCredentials = new X509SigningCredentials(signingCertificate),
    };

    return new JwtSecurityTokenHandler().CreateJwtSecurityToken(tokenDescriptor);
}

我还鼓励您为您的 /token 路由实施 OAuth client_credentials 授权流程。

更新

我发表了一篇完整的文章：non-paywalled link。

如何在 dotnet core 中验证非对称签名的 JWT？

How do I verify an asymmetrically signed JWT in dotnet core?

rsa

jwt

.net-core

asp.net-core

一点补丁

令牌生成

令牌验证

更新