c# - 如何使用.Net Core验证KeyCloak提供的JWT？

Question

我有一个 ASP.Net Core 5 资源服务器，我想验证我的访问 token 但尚未成功。

我写了一个中间件来更好地处理错误:

var token = context.Request.Headers["Authorization"].FirstOrDefault()?.Split(" ").Last();
var tokenHandler = new JwtSecurityTokenHandler();
var key = Encoding.ASCII.GetBytes(_configuration["Jwt:Kid"]); // Kid is copied from 'openid-connect/certs'

tokenHandler.ValidateToken(token, new TokenValidationParameters
{
    ValidIssuer = _configuration["Jwt:Issuer"],
    IssuerSigningKey = new SymmetricSecurityKey(key),
    ValidateAudience = false,
    ValidateIssuer = true,
    ValidateIssuerSigningKey = true,
    ValidateLifetime = false
}, out SecurityToken validatedToken);

我的 KeyCloak 的 key 在 */auth/realms/test/protocol/openid-connect/certs 上:

{
  "keys": [
    {
      "kid": "O9cbi7dzidpxZGLV2eXlTvIECoKDB_YbUN2m73rp8",
      "kty": "RSA",
      "alg": "RS256",
      "use": "sig",
      "n": "qMaFN3tmQ0TaGWaWcanebanGDgh_bz7RzlTbbkiGtY707x...hF40ofv1Fxoy7hBUEKARUqCgjltj5_0TtWn850Eqak41lpa-P_PNsGdwBf18mqBCT8pFbzs8DeRZaD1Q",
      "e": "AQAB",
      "x5c": [
        "MIIClzCCAX8CBgF3jSSr9TANBgkqhkiG9w0BAQsFADAPMQ0wCwYDVQQDDAR0ZXN0MB4XDTIxMDIxMDE4MTAyNloXDTMxMDIxMDE4MTIwNlowDzENMAsGA1UEAwwEdGVzdDCCASIwDQYJKoZI...8tUe5h/7rg1+bHAGVbWg=="
      ],
      "x5t": "G5NYmhm8yEwqHtyLwygxGw89A",
      "x5t#S256": "nEnZWkJQyCG4czEJx04Nyszyzc3l8bsxZ3es2wDTw"
    }
  ]
}

发出请求时，我总是会遇到以下异常。

{"IDX10501: Signature validation failed. Unable to match key: \nkid: 'System.String'.\nExceptions caught:\n 'System.Text.StringBuilder'. \ntoken: 'System.IdentityModel.Tokens.Jwt.JwtSecurityToken'."}

知道我做错了什么吗？

Answer 1

RSA 不是对称算法。所以不要使用 SymmetricSecurityKey 作为签名 key 使用 JsonWebKey 来自动为你生成正确的 key :

tokenHandler.ValidateToken(token, new TokenValidationParameters
{
    ValidIssuer = _configuration["Jwt:Issuer"],
    IssuerSigningKey = new JsonWebKey(jsonKeyString),
    ValidateAudience = false,
    ValidateIssuer = true,
    ValidateIssuerSigningKey = true,
    ValidateLifetime = false
}, out SecurityToken validatedToken);

其中 jsonKeySting 是一个字符串变量，它在提到的 json 中保存您的关键段

{
  "kid": "O9cbi7dzidpxZGLV2eXlTvIECoKDB_YbUN2m73rp8",
  "kty": "RSA",
  "alg": "RS256",
  "use": "sig",
  "n": "qMaFN3tmQ0TaGWaWcanebanGDgh_bz7RzlTbbkiGtY707x...hF40ofv1Fxoy7hBUEKARUqCgjltj5_0TtWn850Eqak41lpa-P_PNsGdwBf18mqBCT8pFbzs8DeRZaD1Q",
  "e": "AQAB",
  "x5c": [
    "MIIClzCCAX8CBgF3jSSr9TANBgkqhkiG9w0BAQsFADAPMQ0wCwYDVQQDDAR0ZXN0MB4XDTIxMDIxMDE4MTAyNloXDTMxMDIxMDE4MTIwNlowDzENMAsGA1UEAwwEdGVzdDCCASIwDQYJKoZI...8tUe5h/7rg1+bHAGVbWg=="
  ],
  "x5t": "G5NYmhm8yEwqHtyLwygxGw89A",
  "x5t#S256": "nEnZWkJQyCG4czEJx04Nyszyzc3l8bsxZ3es2wDTw"
}