将Proxy PAC与EWS API一起使用

Question

我有一个Web应用程序调用EWS托管API连接到office365.

我在MSDN上关注了EWS Managed API 2.0客户端应用程序入门文档.

在web.config我指定的代理pac:

<configuration>
  <system.net>
    <defaultProxy useDefaultCredentials="false">
      <proxy autoDetect="False" bypassonlocal="True" scriptLocation="http://example.com:8080/proxy.pac" usesystemdefault="False" />
    </defaultProxy>
  </system.net>
  [...]
</configuration>

我尝试以下列方式连接到Exchange:

public static ExchangeService getExchangeService(String username)
{
    ServicePointManager.ServerCertificateValidationCallback = CertificateValidationCallBack;

    ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2013);
    service.Credentials = new WebCredentials(USER_365, PWD_365, DOMAIN_365);
    service.UseDefaultCredentials = true;

    //I've tried both WebProxy settings, this:
    service.WebProxy = WebRequest.GetSystemWebProxy();
    //And this (with no success):
    //service.WebProxy = WebRequest.DefaultWebProxy;

    //I've also tried Autodiscover...
    service.AutodiscoverUrl(USER_365, RedirectionUrlValidationCallback);
    //...and direct url
    //service.Url = new Uri("https://outlook.office365.com/EWS/Exchange.asmx");

    service.ImpersonatedUserId = new ImpersonatedUserId(ConnectingIdType.SmtpAddress, username);

    return service;
}

以下是从MSDN复制和粘贴的方法:

private static bool RedirectionUrlValidationCallback(string redirectionUrl)
{
    // The default for the validation callback is to reject the URL.
    bool result = false;

    Uri redirectionUri = new Uri(redirectionUrl);

    // Validate the contents of the redirection URL. In this simple validation
    // callback, the redirection URL is considered valid if it is using HTTPS
    // to encrypt the authentication credentials. 
    if (redirectionUri.Scheme == "https")
    {
        result = true;
    }
    return result;
}

private static bool CertificateValidationCallBack(object sender,
    System.Security.Cryptography.X509Certificates.X509Certificate certificate,
    System.Security.Cryptography.X509Certificates.X509Chain chain,
    System.Net.Security.SslPolicyErrors sslPolicyErrors)
{
    // If the certificate is a valid, signed certificate, return true.
    if (sslPolicyErrors == System.Net.Security.SslPolicyErrors.None)
    {
        return true;
    }

    // If there are errors in the certificate chain, look at each error to determine the cause.
    if ((sslPolicyErrors & System.Net.Security.SslPolicyErrors.RemoteCertificateChainErrors) != 0)
    {
        if (chain != null && chain.ChainStatus != null)
        {
            foreach (System.Security.Cryptography.X509Certificates.X509ChainStatus status in chain.ChainStatus)
            {
                if ((certificate.Subject == certificate.Issuer) &&
                   (status.Status == System.Security.Cryptography.X509Certificates.X509ChainStatusFlags.UntrustedRoot))
                {
                    // Self-signed certificates with an untrusted root are valid. 
                    continue;
                }
                else
                {
                    if (status.Status != System.Security.Cryptography.X509Certificates.X509ChainStatusFlags.NoError)
                    {
                        // If there are any other errors in the certificate chain, the certificate is invalid,
                        // so the method returns false.
                        return false;
                    }
                }
            }
        }

        // When processing reaches this line, the only errors in the certificate chain are 
        // untrusted root errors for self-signed certificates. These certificates are valid
        // for default Exchange server installations, so return true.
        return true;
    }
    else
    {
        // In all other cases, return false.
        return false;
    }
}

我试图评论出这条线:

//service.Url = new Uri("https://outlook.office365.com/ews/Exchange.asmx");

并添加自动发现:

service.AutodiscoverUrl(username);

是否设置代理,注释掉该行:

ServicePointManager.ServerCertificateValidationCallback = CertificateValidationCallBack;

但似乎ExchangeService直接调用服务器而没有通过代理...我错过了什么？

谢谢

Answer 1

尝试从 web.config 中的代理配置中完全删除bypassonlocal 属性。将此属性与 scriptLocation 一起设置时存在问题。

欲了解更多信息：https://blogs.msdn.microsoft.com/rickrain/2011/03/25/why-scriptlocation-may-not-work-when-pointing-to-a-proxy-script-file-in-您的应用程序配置文件/

此外，web.config 默认代理配置应该足够了，以便您可以删除代码中的任何代理设置。

也许这里就是这种情况。

更新：在 web.config 中指定 pac 脚本位置而proxyaddress不是属性应该可以解决此问题。scriptLocation