在 .NET Core 3.1 中验证 Azure AD 生成的 JWT 签名和算法

Question

我是 Azure AD 的新手。我们正在使用 v1.0 令牌。我有一个 Azure JWT 令牌验证例程，主要基于 ValidateSignature 和 AzureTokenValidation 以下是我的 ClaimsTransformer：

public Task<ClaimsPrincipal> TransformAsync(ClaimsPrincipal principal)
{
<do something>
var token = httpContextAccessor.HttpContext.Request.Headers["Authorization"].ToString().Replace("Bearer ", "");
if (Validate(token))
{ 
             <proceed to add claims>
}

和我的验证程序：

 public bool Validate(string token)
        {
            string stsEndpoint = "https://login.microsoftonline.com/common/.well-known/openid-configuration";
            ConfigurationManager<OpenIdConnectConfiguration> configManager = new ConfigurationManager<OpenIdConnectConfiguration>(stsEndpoint, new OpenIdConnectConfigurationRetriever());
            OpenIdConnectConfiguration config = configManager.GetConfigurationAsync().Result;
            TokenValidationParameters parameters = new TokenValidationParameters
            {
                ValidIssuer = "https://sts.windows.net/<mytenant-id>",
                ValidAudience = <my client-id>,
                IssuerSigningKeys = config.SigningKeys,
                ValidateAudience = true,
                ValidateIssuer = true,
                ValidateLifetime = true,
            };
            JwtSecurityTokenHandler tokendHandler = new JwtSecurityTokenHandler();
            SecurityToken jwt;
            bool verified;
            try
            {
               var handler = tokendHandler.ValidateToken(token, validationParameters, out jwt);
               var signature = ((System.IdentityModel.Tokens.Jwt.JwtSecurityToken)jwt).RawSignature;
                string algorithm = ((System.IdentityModel.Tokens.Jwt.JwtSecurityToken)jwt).Header["alg"].ToString();
                if (signature.Length == 0 || algorithm.ToLower().Equals("none"))
                {
                    tokenVerified = false;
                }
                tokenVerified = true;
            }
            catch
            {
                tokenVerified = false;
            }
            return tokenVerified;
        }

请告诉我我做的是否正确，或者我可以使用（在我的验证（字符串令牌）中）

try
{
   var result = tokendHandler.ValidateToken(token, validationParameters, out _);
   verified = true;
}
catch {
   verified = false;
}

并且是，检查算法（不接受 alg 中的“无”）和签名存在是必需的，或者这种检查方式是否正确？没有“秘钥”

Answer 1

JwtBearer 中间件与 Web 应用程序中的 OpenID Connect 中间件一样，根据 TokenValidationParameters 的值验证令牌。根据需要解密令牌，提取声明并验证签名。然后中间件通过检查这些数据来验证令牌：

    Audience: The token is targeted for the web API.
    Sub: It was issued for an app that's allowed to call the web API.
    Issuer: It was issued by a trusted security token service (STS).
    Expiry: Its lifetime is in range.
    Signature: It wasn't tampered with.

更多详情请参考document

示例：

           String token = "Token";  
            string myTenant = "Tenant Name";  
            var myAudience = "Audience";  
            var myIssuer = String.Format(CultureInfo.InvariantCulture, "https://login.microsoftonline.com/{0}/v2.0", myTenant);  
            var mySecret = "Secrete";  
            var mySecurityKey = new SymmetricSecurityKey(Encoding.ASCII.GetBytes(mySecret));              
            var stsDiscoveryEndpoint = String.Format(CultureInfo.InvariantCulture, "https://login.microsoftonline.com/{0}/.well-known/openid-configuration", myTenant);  
            var configManager = new ConfigurationManager<OpenIdConnectConfiguration>(stsDiscoveryEndpoint, new OpenIdConnectConfigurationRetriever());  
            var config = await configManager.GetConfigurationAsync();  
  
            var tokenHandler = new JwtSecurityTokenHandler();  
  
            var validationParameters = new TokenValidationParameters  
            {  
                ValidAudience = myAudience,  
                ValidIssuer = myIssuer,  
                IssuerSigningKeys = config.SigningKeys,  
                ValidateLifetime = false,  
                IssuerSigningKey = mySecurityKey  
            };  
  
            var validatedToken = (SecurityToken)new JwtSecurityToken();  
  
            // Throws an Exception as the token is invalid (expired, invalid-formatted, etc.)  
            tokenHandler.ValidateToken(token, validationParameters, out validatedToken);  
            Console.WriteLine(validatedToken);  
            Console.ReadLine();

输出