我的ASP.NET网站有一个全局错误处理程序,当Web应用程序中出现任何类型的错误时,它会向我(以及另一个开发人员)发送电子邮件.我们最近收到一条错误,其中包含我们从未听说过的电子邮件地址的CC.可怕的是,发送错误电子邮件的开发人员列表在编译的ASP.NET代码中进行了硬编码.我们没有看到如何添加CC.
我们也非常怀疑犯规行为,因为导致错误的请求是尝试使用我们的某个表单发送垃圾邮件.发送请求的IP地址也列在http://www.projecthoneypot.org/上.
我们现在最好的猜测是,请求在某种程度上是错误的,它在电子邮件中注入了CC标头.问题是我们无法弄清楚如何做到这一点.我们正在使用System.Net.Mail发送电子邮件,它似乎可以防止这种情况. MailMessage对象的主题只接受一行,因此您不会创建带有CC行的多行主题.在MailMessage中设置to和cc地址似乎非常强大.我无法看到如何在消息正文中添加CC标头.我找不到任何关于此的信息,我很想知道这是否是一个真正的问题.
编辑:有人要求代码.它有点长,但它是:
public class Global : System.Web.HttpApplication { protected void Application_Error(Object sender,EventArgs e) { // Get the last exception. Exception objException = Server.GetLastError(); // Work out the error details based on the exception. string ErrorType = ""; string ErrorDescription = ""; string ErrorHtml = ""; if (objException == null) { // This should never occur. ErrorType = "Unknown Error"; ErrorDescription = "Unknown Error"; } else if (objException.GetType() == typeof(HttpException)) { // This will occur when the ASP.NET engine throws a HttpException. HttpException objHttpException = objException as HttpException; if (objHttpException.GetHttpCode() == 404) { string Resource = Globals.GetFullUrl(this.Context); Server.ClearError(); Response.Redirect("/ResourceNotFound.aspx?BadUrl=" + Server.UrlEncode(Resource)); return; } else { ErrorType = objHttpException.GetHttpCode().ToString(); ErrorDescription = objHttpException.Message; } } else if (objException.GetType() == typeof(HttpUnhandledException) && objException.InnerException != null && objException.InnerException.GetType() == typeof(HttpException)) { // This will occur when the code throws a HttpException (e.g. a fake 404). HttpException objHttpException = objException.InnerException as HttpException; if (objHttpException.GetHttpCode() == 404) { string Resource = Globals.GetFullUrl(this.Context); Server.ClearError(); Response.Redirect("/ResourceNotFound.aspx?BadUrl=" + Server.UrlEncode(Resource)); return; } else { ErrorType = objHttpException.GetHttpCode().ToString(); ErrorDescription = objHttpException.Message; } } else if (objException.GetType() == typeof(HttpUnhandledException)) { // This will occur when a page throws an error. HttpUnhandledException objHttpUnhandledException = (HttpUnhandledException) objException; ErrorType = objHttpUnhandledException.GetHttpCode().ToString(); if (objHttpUnhandledException.InnerException != null) ErrorDescription = objHttpUnhandledException.InnerException.Message; else ErrorDescription = objHttpUnhandledException.Message; if (objHttpUnhandledException.GetHtmlErrorMessage() != null) { ErrorHtml = objHttpUnhandledException.GetHtmlErrorMessage(); } } else if (objException.GetType() == typeof(HttpRequestValidationException) && !Globals.IsTtiUser(this.Context)) { // Do nothing. This is mostly just spider junk and we don't want to know about it. } else { // This will occur when the ASP.NET engine throws any error other than a HttpException. ErrorType = objException.GetType().Name; ErrorDescription = objException.Message; } // Send an email if there's an error to report. if (ErrorType != "" || ErrorDescription != "") { Globals.SendErrorEmail(this.Context,ErrorType,ErrorDescription,ErrorHtml); } } public static void SendErrorEmail (HttpContext context,string errorType,string errorDescription,string errorHtml) { // Build the email subject. string Subject = "EM: " + errorType + ": " + context.Request.ServerVariables["SCRIPT_NAME"]; // Build the email body. string Body; StringBuilder sb = new StringBuilder(""); sb.Append("Server:\r\n"); sb.Append(Globals.Server.ToString() + "\r\n"); sb.Append("\r\n"); sb.Append("URL:\r\n"); sb.Append(Globals.GetFullUrl(context) + "\r\n"); sb.Append("\r\n"); sb.Append("Error Type" + ":\r\n"); sb.Append(errorType + "\r\n"); sb.Append("\r\n"); sb.Append("Error Description" + ":\r\n"); sb.Append(errorDescription + "\r\n"); sb.Append("\r\n"); sb.Append("Referring Page:\r\n"); sb.Append(context.Request.ServerVariables["HTTP_REFERER"] + "\r\n"); sb.Append("\r\n"); sb.Append("Date/Time:\r\n"); sb.Append(DateTime.Now.ToString() + "\r\n"); sb.Append("\r\n"); sb.Append("Remote IP:\r\n"); sb.Append(context.Request.ServerVariables["REMOTE_ADDR"] + "\r\n"); sb.Append("\r\n"); sb.Append("User Agent:\r\n"); sb.Append(context.Request.ServerVariables["HTTP_USER_AGENT"] + "\r\n"); sb.Append("\r\n"); sb.Append("Crawler:\r\n"); sb.Append(context.Request.Browser.Crawler.ToString() + "\r\n"); sb.Append("\r\n"); sb.Append("Admin User:\r\n"); sb.Append(context.User.Identity.Name + "\r\n"); sb.Append("\r\n"); sb.Append("\r\n"); Body = sb.ToString(); // If there's HTML to represent the error (usually from HttpUnhandledException),// then stuff the body text into the HTML (if possible). bool HtmlMessage = false; if (errorHtml != "") { Regex r = new Regex("(?<thebodytext><body.*?>)",RegexOptions.IgnoreCase); if (r.IsMatch(errorHtml)) { Body = Body.Replace("\r\n","<br>"); Body = r.Replace(errorHtml,"${thebodytext}" + Body,1); HtmlMessage = true; } } // Send an email to the TTI developers. MailMessage objMail; objMail = new MailMessage(); objMail.From = new MailAddress("from-address"); objMail.To.Add(new MailAddress("to-address")); objMail.CC.Add(new MailAddress("cc-address")); objMail.CC.Add(new MailAddress("another-cc-address")); if (HtmlMessage) objMail.IsBodyHtml = true; else objMail.IsBodyHtml = false; if (errorType == "404") objMail.Priority = MailPriority.Low; else objMail.Priority = MailPriority.High; objMail.Subject = Subject; objMail.Body = Body; try { SmtpClient objSmtpClient = new SmtpClient(); objSmtpClient.Send(objMail); } finally { // Do nothing. } } }
解决方法
我可以看到这是一个非常有创意的攻击的目标……你正在将用户控制的数据填充到你的消息体中……在这一点上,狡猾地使用二进制数据COULD会导致一个BODY在发送期间发送正确的数据用于格式化的SMTP会话JUST RIGHT …如果可以,我建议将正文转换为所有ASCII文本,或者在字符串构建期间,编写一个只允许RFC字符的字符串清理程序.(过滤URL,REFERRER,远程地址和UserAgent).那些是你更有可能的攻击点.
第二个想法可能是在代码中构造一个基本电子邮件,并将您构建的正文作为文本,HTML或PDF文件进行ATTACH.
请记住,SMTP ENVELOPE数据与消息数据不同….如果某人狡猾得足以发送导致在正文部分期间发送CRLFCRLF.CRLFCRLF的正确正文,则会终止发送,然后如果他们继续发送数据,他们可以发送整个MAIL FROM:RCPT TO:,DATA等…(当然,这是不太可能的情况……)……
我很乐意看到您收到的电子邮件的RAW源…(如实际SMTP事务的十六进制转储,而不是Outlook希望您看到的内容,或其他).
在发送消息之前,您也可以尝试使用QP或B64对身体进行编码….这可能会解决您的问题……
这是一个有趣的,我期待它的结果.