I'm writing a regular expression that can interactively validate SMTP responses codes, once the SMTP dialog is completed it should pass the following regex (some parentheses added for better readability):
^(220)(250){3,}(354)(250)(221)$
Or with(out) authentication:
^(220)(250)((334){2}(235))?(250){2,}(354)(250)(221)$
I'm trying to do rewrite the above regexes so that I can interactively check if the dialog is going as expected, otherwise politely send a QUIT command and close the connection saving bandwidth and time, but I'm having a hard time writing an optimal regex. So far I've managed to come up with:
^(220(250(334(235(250(354(250(221)?)?)?){0,})?){0,2})?)?$
Which, besides only matching authenticated connections, has some bugs... For instance, it matches:
220250334235250354250221
220250334334235250354250221
I've also tried the following modification:
^(220(250)?)?((334(235)?){2})?(250(354(250(221)?)?)?){0,}$
This one accepts non-authenticated responses but it fails to match 220250334 and wrongly matches 220250334334235250354250221 (at least 2 250 are needed before the 354 response code).
Can someone help me out with this? Thanks in advance.
An example of what I'm trying to do:
$smtp = fsockopen('mail.example.com', 25);
$result = null;
$commands = array('HELO', 'AUTH LOGIN', 'user', 'pass', 'MAIL FROM', 'RCPT TO', 'RCPT TO', 'DATA', "\r\n.", 'QUIT');
foreach ($commands as $command)
{
$result .= substr(fgets($smtp), 0, 3);
if (preg_match('~^(220(250)?)?((334){1,2}(235)?)?(250(354(250(221)?)?)?){0,}$~S', $result) > 0)
{
fwrite($smtp, $command . "\r\n");
}
else
{
fwrite($smtp, "QUIT\r\n");
fclose($smtp);
break;
}
}
Which should act as a replacement for the following procedural code:
$smtp = fsockopen('mail.example.com', 25);
$result = substr(fgets($smtp), 0, 3); // 220
if ($result == '220')
{
fwrite($smtp, 'HELO' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 220
if ($result == '250')
{
fwrite($smtp, 'AUTH LOGIN' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 334
if ($result == '334')
{
fwrite($smtp, 'user' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 334
if ($result == '334')
{
fwrite($smtp, 'pass' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 235
if ($result == '235')
{
fwrite($smtp, 'MAIL FROM' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 250
if ($result == '250')
{
foreach ($to as $mail)
{
fwrite($smtp, 'RCPT TO' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 250
if ($result != '250')
{
fwrite($smtp, 'QUIT' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 221
fclose($smtp);
break;
}
}
if ($result == '250')
{
fwrite($smtp, 'DATA' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 354
if ($result == '354')
{
fwrite($smtp, "\r\n.\r\n");
$result = substr(fgets($smtp), 0, 3); // 250
if ($result == '250')
{
fwrite($smtp, 'QUIT' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 221
fclose($smtp);
if ($result == '221')
{
echo 'SUCESS!';
}
}
else
{
fwrite($smtp, 'QUIT' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 221
fclose($smtp);
}
}
else
{
fwrite($smtp, 'QUIT' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 221
fclose($smtp);
}
}
}
else
{
fwrite($smtp, 'QUIT' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 221
fclose($smtp);
}
}
else
{
fwrite($smtp, 'QUIT' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 221
fclose($smtp);
}
}
else
{
fwrite($smtp, 'QUIT' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 221
fclose($smtp);
}
}
else
{
fwrite($smtp, 'QUIT' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 221
fclose($smtp);
}
}
else
{
fwrite($smtp, 'QUIT' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 221
fclose($smtp);
}
}
else
{
fwrite($smtp, 'QUIT' . "\r\n");
$result = substr(fgets($smtp), 0, 3); // 221
fclose($smtp);
}