// VRFY/EXPN
private string _CmdVrfy(string cmdLine)
{
var id = _GetCommandId(cmdLine);
_vrfyCount++;
var parts = _ParseCmdLine(id, cmdLine);
if (2 != parts.Count)
{
_errCount++;
return String.Format("501 {0} needs argument", parts[0]);
}
if (!_CheckMailAddr(parts[1]))
{
_errCount++;
return String.Format("553 Invalid address {0}", parts[1]);
}
_lastCmd = id;
if (id == _CmdId.Vrfy)
return "252 Cannot VRFY user; try RCPT to attempt delivery (or try finger)";
return String.Format("250 {0}", parts[1]);
}
// splits an SMTP command into command and argument(s)
private List<string> _ParseCmdLine(_CmdId id, string cmdLine)
{
var parts = new List<string>();
if (string.IsNullOrEmpty(cmdLine))
return parts;
try
{
var cmdStr = _cmdList[(int)id];
var pos = cmdLine.IndexOf(cmdStr.Contains(':') ? ':' : ' ');
if (-1 != pos)
{
var cmd = _CleanupString(cmdLine.Substring(0, pos));
var arg = _CleanupString(cmdLine.Substring(pos + 1));
parts.Add(cmd.ToUpper());
parts.Add(arg);
}
else
parts.Add(_CleanupString(cmdLine).ToUpper());
}
catch
{
parts = new List<string>();
}
return parts;
}
// RSET
private string _CmdRset()
{
_ResetSession();
_lastCmd = _CmdId.Rset;
return "250 Reset Ok";
}
// unknown/unsupported
private string _CmdUnknown(string cmdLine)
{
_errCount++;
_lastCmd = _CmdId.Invalid;
return string.IsNullOrEmpty(cmdLine)
? "500 Command unrecognized"
: string.Format("500 Command unrecognized ({0})", cmdLine);
}
// QUIT
private string _CmdQuit()
{
_lastCmd = _CmdId.Quit;
return "221 Closing connection.";
}
// RCPT TO:
private string _CmdRcpt(string cmdLine)
{
if (string.IsNullOrEmpty(_mailFrom))
{
_errCount++;
return "503 Need MAIL before RCPT";
}
var parts = _ParseCmdLine(_CmdId.RcptTo, cmdLine);
if (2 != parts.Count)
{
_errCount++;
return String.Format("501 {0} needs argument", parts[0]);
}
if (!_CheckMailAddr(parts[1]))
{
_errCount++;
return String.Format("553 Invalid address {0}", parts[1]);
}
if (!_IsLocalDomain(_mailDom))
{
// relaying not allowed...
_errCount++;
return "530 Relaying not allowed for policy reasons";
}
if (!_IsLocalBox(_mailBox, _mailDom))
{
// unkown/invalid recipient
_errCount++;
return String.Format("553 Unknown email address {0}", parts[1]);
}
_rcptTo.Add(parts[1]);
_lastCmd = _CmdId.RcptTo;
return string.Format("250 {0}... Recipient ok", parts[1]);
}
// MAIL FROM:
private string _CmdMail(string cmdLine)
{
if (string.IsNullOrEmpty(_heloStr))
{
_errCount++;
return "503 HELO/EHLO Command not issued";
}
if (!string.IsNullOrEmpty(_mailFrom))
{
_errCount++;
return "503 Nested MAIL command";
}
var parts = _ParseCmdLine(_CmdId.MailFrom, cmdLine);
if (2 != parts.Count)
{
_errCount++;
return String.Format("501 {0} needs argument", parts[0]);
}
if (!_CheckMailAddr(parts[1]))
{
_errCount++;
return String.Format("553 Invalid address {0}", parts[1]);
}
_mailFrom = parts[1];
_lastCmd = _CmdId.MailFrom;
return string.Format("250 {0}... Sender ok", parts[1]);
}
// HELO/EHLO
private string _CmdHelo(string cmdLine)
{
var id = _GetCommandId(cmdLine);
var parts = _ParseCmdLine(id, cmdLine);
if (2 != parts.Count)
{
_errCount++;
return String.Format("501 {0} needs argument", parts[0]);
}
if (!string.IsNullOrEmpty(_heloStr))
{
_errCount++;
return string.Format("503 you already sent {0} ...", parts[0]);
}
if (AppGlobals.CheckHelloFormat && !_CheckHelo(parts[1]))
{
_errCount++;
return String.Format("501 Invalid {0}", parts[0]);
}
if (parts[1].ToLower().Equals("localhost") ||
parts[1].ToLower().Equals(AppGlobals.HostName) ||
parts[1].StartsWith("[127.") ||
parts[1].Equals("[" + AppGlobals.ListenAddress + "]")
)
{
_errCount++;
return String.Format("501 spoofed {0}", parts[0]);
}
_heloStr = parts[1];
_lastCmd = id;
if (id == _CmdId.Helo)
return String.Format("250 Hello {0} ([{1}]), nice to meet you.", parts[1], _clientIp);
return String.Format("250 Hello {0} ([{1}]), nice to meet you.\r\n250-HELP\r\n250-VRFY\r\n250-EXPN\r\n250 NOOP", parts[1], _clientIp);
}
// end of DATA (dot)
private string _CmdDot()
{
_lastCmd = _CmdId.Noop;
return "250 Queued mail for delivery";
}
// DATA
private string _CmdData()
{
if (_rcptTo.Count < 1)
{
_errCount++;
return "471 Bad or missing RCPT command";
}
_lastCmd = _CmdId.Data;
return "354 Start mail input; end with <CRLF>.<CRLF>";
}
public void HandleSession()
{
var cmdLine = "?";
var currCmd = _CmdId.Invalid;
if (false == _initOk)
{
_CloseSession();
return;
}
// sessions limit reached, reject session
if (_sessCount > AppGlobals.MaxSessions)
{
_SendLine(_tempfailMsg);
_CloseSession();
return;
}
// if the remote IP isn't a private one
if (!_IsPrivateIp(_clientIp))
{
// checks the incoming IP against whitelists, if listed skip blacklist checks
var isDnsListed = _IsListed(_clientIp, AppGlobals.WhiteLists, "white");
if (!isDnsListed)
{
// check the IP against blacklists
isDnsListed = _IsListed(_clientIp, AppGlobals.BlackLists, "black");
if ((isDnsListed) && (!AppGlobals.StoreData))
{
// if blacklisted and NOT storing messages
_SendLine(string.Format(_dnsblMsg, _clientIp, _dnsListName));
_CloseSession();
return;
}
}
}
// add a short delay before banner and check for early talker
// see http://wiki.asrg.sp.am/wiki/Early_talker_detection
_SleepDown(AppGlobals.BannerDelay);
_earlyTalker = _IsEarlyTalker();
if (_earlyTalker)
{
_SendLine(_etalkerMsg);
_CloseSession();
return;
}
// all ok, send out our banner
var connOk = _SendLine(_CmdBanner());
while ((null != cmdLine) && connOk)
{
string response;
if (_lastCmd == _CmdId.Data)
{
var mailMsg = _RecvData();
if (_timedOut)
{
// got a receive timeout during the DATA phase
_SendLine(_timeoutMsg);
_CloseSession();
return;
}
response = _CmdDot();
if (String.IsNullOrEmpty(mailMsg))
response = "422 Recipient mailbox exceeded quota limit.";
else
{
_StoreMailMsg(mailMsg);
if (AppGlobals.DoTempFail)
{
// emit a tempfail AFTER storing the mail DATA
_SendLine(_tempfailMsg);
_CloseSession();
return;
}
}
_ResetSession();
}
else
{
// read an SMTP command line and deal with the command
cmdLine = _RecvLine();
if (null != cmdLine)
{
_LogCmdAndResp(_dirRx, cmdLine);
currCmd = _GetCommandId(cmdLine);
switch (currCmd)
{
case _CmdId.Helo: // HELO
response = _CmdHelo(cmdLine);
break;
case _CmdId.Ehlo: // EHLO
response = _CmdHelo(cmdLine);
break;
case _CmdId.MailFrom: // MAIL FROM:
response = _CmdMail(cmdLine);
break;
case _CmdId.RcptTo: // RCPT TO:
response = _CmdRcpt(cmdLine);
break;
case _CmdId.Data: // DATA
if ((AppGlobals.DoTempFail) && (!AppGlobals.StoreData))
{
// emit a tempfail upon receiving the DATA command
response = _tempfailMsg;
cmdLine = null;
_lastCmd = currCmd = _CmdId.Quit;
}
else
response = _CmdData();
break;
case _CmdId.Rset: // RSET
response = _CmdRset();
break;
case _CmdId.Quit: // QUIT
response = _CmdQuit();
cmdLine = null; // force closing
break;
case _CmdId.Vrfy: // VRFY
response = _CmdVrfy(cmdLine);
break;
case _CmdId.Expn: // EXPN
response = _CmdVrfy(cmdLine);
break;
case _CmdId.Help: // HELP
response = _CmdHelp();
break;
case _CmdId.Noop: // NOOP
response = _CmdNoop(cmdLine);
break;
default: // unkown/unsupported
response = _CmdUnknown(cmdLine);
break;
}
}
else
{
// the read timed out (or we got an error), emit a message and drop the connection
response = _timeoutMsg;
currCmd = _CmdId.Quit;
}
}
// send response
if ((_errCount > 0) && (_CmdId.Quit != currCmd))
{
// tarpit a bad client, time increases with error count
_SleepDown(AppGlobals.ErrorDelay * _errCount);
}
else
{
// add a short delay
_SleepDown(25);
}
// checks for early talkers
_earlyTalker = _IsEarlyTalker();
// send out the response
connOk = _SendLine(response);
// check/enforce hard limits (errors, vrfy ...)
if (_CmdId.Quit != currCmd && connOk)
{
string errMsg = null;
if (_msgCount > AppGlobals.MaxMessages)
{
// above max # of message in a single session
errMsg = "451 Session messages count exceeded";
}
else if (_errCount > AppGlobals.MaxSmtpErr)
{
// too many errors
errMsg = "550 Max errors exceeded";
}
else if (_vrfyCount > AppGlobals.MaxSmtpVrfy)
{
// tried to VRFY/EXPN too many addresses
errMsg = "451 Max recipient verification exceeded";
}
else if (_noopCount > AppGlobals.MaxSmtpNoop)
{
// entered too many NOOP commands
errMsg = "451 Max NOOP count exceeded";
}
else if (_rcptTo.Count > AppGlobals.MaxSmtpRcpt)
{
// too many recipients for a single message
errMsg = "452 Too many recipients";
}
else if (_earlyTalker)
{
// early talker
errMsg = _etalkerMsg;
}
if (null != errMsg)
{
connOk = _SendLine(errMsg);
cmdLine = null; // force closing
}
}
// check if connection Ok
if (connOk)
connOk = _client.Connected;
} // while null...
// close/reset this session
_CloseSession();
}
