path: root/it_mail.class

<?php
/*
**	Copyright (C) 1995-2021 by the ITools Authors.
**	This file is part of ITools - the Internet Tools Library
**
**	ITools is free software; you can redistribute it and/or modify
**	it under the terms of the GNU General Public License as published by
**	the Free Software Foundation; either version 3 of the License, or
**	(at your option) any later version.
**
**	ITools is distributed in the hope that it will be useful,
**	but WITHOUT ANY WARRANTY; without even the implied warranty of
**	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
**	GNU General Public License for more details.
**
**	You should have received a copy of the GNU General Public License
**	along with this program.  If not, see <http://www.gnu.org/licenses/>.
**
**	mail.class - Create a mail object, add header and content and send it
*/

define('IT_MAIL_PLAIN', 0);
define('IT_MAIL_HTML', 1);

/* Return codes of it_mail::check_email() */
define('IT_MAIL_CHECKEMAIL_INVALID', 0);
define('IT_MAIL_CHECKEMAIL_MAILBOXFULL', 5);
define('IT_MAIL_CHECKEMAIL_OK', 10);

/**
 * Construct an email message with headers, body (plaintext and/or HTML) and
 * send it. Also provides utility function to check email address validity.<br>
 * On devel/twin machines, will output mail instead of sending it.<br>
 * <em>Example:</em><br>
 * <code><nobr>
 * if (!it_mail::check_email($to))<br>
 * &nbsp;&nbsp;&nbsp;&nbsp;die("Invalid email address '$to'\n");<br>
 * <br>
 * $mail = new it_mail(array('To' => $to&#44; 'From' => 'itools@gna.ch', 'Subject' => 'Example'));<br>
 * $mail->add_body('Plain text message body');<br>
 * $mail->add_body('HTML message with &lt;a href="https://gna.ch/"&gt;link&lt;/a&gt;', IT_MAIL_HTML);<br>
 * $mail->send();<br>
 * </nobr></code>
 */
class it_mail
{
	var $header_names = array();
	var $header_values = array();
	var $body = array();
	var $attachments = array();

	var $to = array();
	var $subject = "";
	var $cc = array();
	var $bcc = array();
	var $flags = "";
	var $charset;

/**
 * Construct a new email message. Headers and body can be added later.
 * Note: Headers To, Cc, Bcc can be arrays
 * @param $headers Array of headers for this email, e.g. From, To and Subject
 */
function __construct($headers = array())
{
	$this->charset = ini_get('default_charset');

	foreach ((array)$headers as $header => $value)
		$this->add_header($header, $value);
}


/**
 * Add header line to the this email message. Can be called repeatedly.
 * Note: Headers To, Cc, Bcc can be arrays
 * @param $header Header to be added, e.g. Cc, Bcc or X-My-Header
 * @param $value Value of header, e.g. itools@gna.ch for Bcc header
 */
function add_header($header, $value)
{
	switch ($header)
	{
		case 'To':
			foreach ((array)$value as $val)
				$this->to[] = $this->addrlist_encode($val);
			break;

		case 'Subject':
			$this->subject .= $value;	# Escape on sending
			break;

		case 'Cc':
			foreach ((array)$value as $val)
				$this->cc[] = $this->addrlist_encode($val);
			break;

		case 'Bcc':
			foreach ((array)$value as $val)
				$this->bcc[] = $this->addrlist_encode($val);
			break;

		case 'charset':
			$this->charset = $value;
			break;

		case 'Errors-To':
			$this->flags = "-f " . escapeshellarg(preg_replace('/.*<([^>]+)>.*/', '$1', $value));
			/* FALLTHROUGH */
		default:
			$this->header_names[] = $header;
			$this->header_values[] = $header == 'From' || $header =='Reply-To' ? $this->addrlist_encode($value) : $this->header_encode($value);
			break;
	}
}


/**
 * Add body part to this email message. Can be called repeatedly.
 * @param $text Text to be added to email message
 * @param $type Type of text, one of IT_MAIL_PLAIN (default) or IT_MAIL_HTML
 */
function add_body($text, $type = IT_MAIL_PLAIN)
{
	switch ($type)
	{
		case IT_MAIL_PLAIN:
		case IT_MAIL_HTML:
			$this->body[$type] .= $text;
			break;

		default:
			it::fatal("it_mail::add_body invalid type $type");
			break;
	}
}


/**
 * Add attachment to this email message. Can be called repeatedly.
 * @param $data Data to be attached
 * @param $p['dispositon'] optional Content-Disposition value: "inline" or "attachment"
 * @param $p['mimetype'] optional MIME-Type of attached file
 * @param $p['name'] optional name of attached file
 * @return 'cid:'.Content-ID of this attachment
 */
function add_attachment($data, $p = array(), $legacy_name = null)
{
	if (!is_array($p))	# legacy mode: two scalars mime type / name
		$p = array('mimetype' => $p) + ($legacy_name ? array('name' => $legacy_name) : array());

	$this->attachments[] = $p + array(
		'cid'         => $cid = bin2hex(random_bytes(16)),
		'data'        => $data,
		'disposition' => "inline",
		'mimetype'    => "application/octet-stream",
		'name'        => "Attachment" . (count($this->attachments) + 1),
	);

	return "cid:$cid";
}


/**
 * Add file attachment to this email message. Can be called repeatedly.
 * @param $filename File to be attached
 * @param $p['dispositon'] optional Content-Disposition value: "inline" or "attachment"
 * @param $p['mimetype'] MIME-Type of attached file
 * @param $p['name'] Name of attached file as stored in mail
 */
function add_file($filename, $p = array(), $legacy_name = null)
{
	if (!is_array($p))	# legacy mode: two scalars mime type / name
		$p = array('mimetype' => $p) + ($legacy_name ? array('name' => $legacy_name) : array());

	return $this->add_attachment(it::file_get_contents($filename), $p + array('name' => basename($filename)));
}


/**
 * Send this email message
 * @param $p['forcemail'] Send mail even if on twin or devel machine
 * @param $p['it_error']  Error handling params for bad email addresses
 * @return True if mail was accepted for delivery
 */
function send($p = array())
{
	$to = implode(",", $this->to);
	$headers = array();

	if (count($this->cc) > 0)
		$headers[] = "Cc: " . implode(",", $this->cc);

	if (count($this->bcc) > 0)
		$headers[] = "Bcc: " . implode(",", $this->bcc);

	for ($i = 0; $i < count($this->header_names); $i++)
		$headers[] = $this->header_names[$i] . ': ' . $this->header_values[$i];

	foreach (array_merge((array)$this->to, (array)$this->cc, (array)$this->bcc) as $addr)
		if (($error = self::address_error($addr)))
			it::error((array)$p['it_error'] + ['title' => "address error '$error'", 'body' => $this]);

	/* Automatically add doctype if none given */
	if ($this->body[IT_MAIL_HTML] && !preg_match('/^<!doctype/i', $this->body[IT_MAIL_HTML]))
		$this->body[IT_MAIL_HTML] = '<!doctype html public "-//w3c//dtd html 4.01 transitional//en">' . "\n" . $this->body[IT_MAIL_HTML];


	$headers[] = "MIME-Version: 1.0";

	if ($this->attachments)
	{
		/* Attachments need multipart MIME mail */
		$boundary1 = bin2hex(random_bytes(16));
		$mixedtype = "Content-Type: multipart/mixed; boundary=\"$boundary1\"";

		$headers[] = $mixedtype;
		$text .= "This is a multi-part message in MIME format.";
		$text .= "\n--$boundary1\n";
	}

	/* Headers for plain and HTML content */
	$plaintype = "Content-Type: text/plain; charset=".$this->charset."\nContent-Transfer-Encoding: 8bit";
	$htmltype = "Content-Type: text/html; charset=".$this->charset."\nContent-Transfer-Encoding: 8bit";

	if ($this->body[IT_MAIL_PLAIN])
	{
		if ($this->body[IT_MAIL_HTML])
		{
			$boundary2 = bin2hex(random_bytes(16));
			$alternativetype = "Content-Type: multipart/alternative; boundary=\"$boundary2\"";

			/* Plain and HTML */
			if ($this->attachments)
				$text .= "$alternativetype\n\n";
			else
				$headers[] = $alternativetype;

			$text .= "--$boundary2\n$plaintype\n\n";
			$text .= $this->body[IT_MAIL_PLAIN];
			$text .= "\n--$boundary2\n$htmltype\n\n";
			$text .= $this->body[IT_MAIL_HTML];
			$text .= "\n--$boundary2--\n";
		}
		else
		{
			/* Just plain */
			if ($this->attachments)
				$text .= "$plaintype\n\n";
			else
				$headers[] = $plaintype;

			$text .= $this->body[IT_MAIL_PLAIN];
		}
	}
	else if ($this->body[IT_MAIL_HTML])
	{
		/* Just HTML */
		if ($this->attachments)
		{
			if (strstr($this->body[IT_MAIL_HTML], "cid:"))
			{
				$boundary3 = bin2hex(random_bytes(16));
				$text .= "Content-Type: multipart/related; boundary=\"$boundary3\"\n\n--$boundary3\n";
			}

			$text .= "$htmltype\n\n";
		}
		else
			$headers[] = $htmltype;

		$text .= $this->body[IT_MAIL_HTML];
	}

	if ($this->attachments)
	{
		$text .= "\n";
		$boundary = $boundary3 ? $boundary3 : $boundary1;

		foreach ($this->attachments as $attachment)
		{
			$name = $this->header_encode($attachment['name']);
			$text .= "\n--$boundary\nContent-Type: {$attachment['mimetype']}; name=\"$name\"\nContent-Transfer-Encoding: base64\nContent-ID: <{$attachment['cid']}>\nContent-Disposition: {$attachment['disposition']}; filename=\"$name\"\n\n";
			$text .= chunk_split(base64_encode($attachment['data']));
		}

		if ($boundary3)
			$text .= "\n--$boundary3--\n\n";

		$text .= "--$boundary1--\n";
	}

	if (it::is_live() || EDC('forcemail') || $p['forcemail'])
	{
		if (($result = mail($to, $this->header_encode($this->subject), $text, implode("\n", $headers), $this->flags)) === false)
			it::error(['title' => "failed sending mail to $to subject $this->subject", 'body' => ['text' => $text, 'headers' => $headers, 'flags' => $this->flags]]);
		return $result;
	}
	else
		return ED($to, $this->header_encode($this->subject), $text, $headers, $this->flags);
}


/**
 * INTERNAL: Split address lists in headers like From, To, Cc, Bcc into
 * name/email pairs
 * @param $string String containing address list
 * @return Generator returning name/email tuples
 */
static function addrlist_split($string)
{
	$quoted = false;
	foreach (str_split($string) as $char)
	{
		if ($char == '"')
			$quoted = !$quoted;

		if ($char == ',' && !$quoted)
			$n++;
		else
			$mailboxes[$n] .= $char;
	}

	foreach ((array)$mailboxes as $mailbox)
	{
		$mode = 'name';
		$name = $email = '';
		$quoted = false;
		foreach (str_split($mailbox) as $char)
		{
			if ($char == '"')
				$quoted = !$quoted;
			switch ($mode)
			{
			case 'name':
				if ($char == '<' && !$quoted)
					$mode = 'email';
				else
					$name .= $char;
				break;
			case 'email':
				if ($char == '>' && !$quoted)
				{
					$mode = 'finish';
					break 2;
				}
				else
					$email .= $char;
				break;
			}
		}
		if ($mode == 'email')
		{
			$name = $name . '<' . $email;
			$email = '';
			$mode = 'name';
		}
		if ($mode == 'name' && !$email)
		{
			$email = it::replace(['^"(.*)"$' => '$1'], trim($name));
			$name = '';
		}
		yield [$name, trim($email)];
	}
}


/**
 * INTERNAL: Escape header line with ?=?<charset>?Q if necessary, e.g. in Subject line
 * @param $string String to be escaped
 * @return String escape suitable for sending in header line
 */
function header_encode($string)
{
	return preg_match('/[\x00-\x1f\x7f-\xff]/', $string)
		? ltrim(
			($encoded = @iconv_mime_encode('', $string, array('scheme' => 'Q', 'input-charset' => $this->charset, 'output-charset' => $this->charset))) !== false
			? $encoded
			: (($encoded = @iconv_mime_encode('', $string, array('scheme' => 'B', 'input-charset' => $this->charset, 'output-charset' => $this->charset))) !== false
				? $encoded
				: iconv_mime_encode('', $string, array('scheme', 'B', 'input-charset' => 'ISO-8859-1', 'output-charset' => $this->charset))),
			' :'
		)
		: $string;
}

/**
 * INTERNAL: Escape address lists in headers like From, To, Cc, Bcc
 * @param $string String containing address list
 * @return String suitable for sending in address list headers
 */
function addrlist_encode($string)
{
	# Exclude e-mail addresses from being encoded as
	# e.g. GMail or Exchange have problems with that
	foreach (self::addrlist_split($string) as list($name, $email))
	{
		$email = self::email_encode($email);
		if ($name && $email)
			$result[] = $this->header_encode(trim($name)) . " <$email>";
		else if (!$name && $email)
			$result[] = $email;
	}

	return implode(', ', $result);
}


/**
 * Make string safe to be used in "$fullname <$email>": Remove illegal
 * characters and enclose in double quotes.
 * @param $string Fulle name to be escaped
 * @return String to be safely used in "$fullname <$email>" for To: etc.
 */
static function fullname_encode($string)
{
	return '"' . preg_replace('/["\x00-\x1f]/', '', $string) . '"';
}


/**
 * INTERNAL: Split email-address into local part and doomain
 * @return Array with to elements: local part and domain
 */
static function email_split($email)
{
	$mode = 'local';
	$local = $domain = '';
	$quoted = false;
	foreach (str_split($email) as $char)
	{
		if ($char == '"')
			$quoted = !$quoted;
		switch ($mode)
		{
		case 'local':
			if ($char == '@' && !$quoted)
				$mode = 'domain';
			else
				$local .= $char;
			break;
		case 'domain':
			$domain .= $char;
		}
	}

	return [$local, $domain];
}


/**
 * INTERNAL: Convert domain part of email address into ascii idn form
 * @return String with converted email address
 */
static function email_encode($email)
{
	list($local, $domain) = self::email_split($email);

	return $local . ($domain ? '@' . idn_to_ascii($domain) : '');
}


/**
 * INTERNAL: Send SMTP command and return true if result is 2XX
 * @param $fp Connection to SMTP server opened using fsockopen
 * @param $command Command to send, e.g. HELO gna.ch
 * @param $anwer String containing full answer from SMTP server
 * @param timeoutok Whether a timeout is considered ok
 * @param $failcode Lowest SMTP result code which is considered a failure (default 300)
 * @return True if SMTP result code is lower than $failcode
 *
 */
static function send_smtp_cmd($fp, $cmd, &$answer, $timeoutok = false, $failcode = 300)
{
	$result = false;
	$answer = '';

	if (!$cmd || (!feof($fp) && fwrite($fp, "$cmd\r\n")))
	{
		while (!feof($fp) && preg_match('/^(...)(.?)(.*)[\r\n]*$/', fgets($fp, 1024), $regs))
		{
			$answer .= $regs[0];
			$resultcode = intval($regs[1]);

			if ($regs[2] != '-')	/* Multi line response? */
			{
				if (($resultcode >= 100) && ($resultcode < $failcode))
					$result = true;

				break;
			}
		}
	}

	/* A timeout can be considered ok for SLOW mail servers */
	if ($answer == '')
		$result = $timeoutok;

	EDC('mailcheck', time(), $cmd, $result, $answer);

	return $result;
}

/* Return errors found with email address, null otherwise
 */
static function address_error($addresslist)
{
	foreach (self::addrlist_split($addresslist) as list($dummy, $email))
	{
		$email = self::email_encode($email);
		if (filter_var($email, FILTER_VALIDATE_EMAIL, FILTER_FLAG_EMAIL_UNICODE) === false && !it::match('^\s*[a-z][-a-z0-9]*\s*$', $email))
			return "invalid format on $email";
	}
}


/**
 * Check if given email address is valid (syntax, MX record). If you set
 * checkmailbox to true it also connects to MX and asks if mailbox is valid.
 * Note: Connecting to the MX can be slow.
 * @param $email email to be check
 * @param $checkmailbox True if you want to connect to MX and check account
 * @return One of IT_MAIL_CHECKEMAIL_INVALID (0), IT_MAIL_CHECKEMAIL_MAILBOXFULL
 * or IT_MAIL_CHECKEMAIL_OK (both != 0).
 */
static function check_email($email, $checkmailbox = false)
{
	$result = IT_MAIL_CHECKEMAIL_INVALID;

	$email = self::email_encode($email);
	list($dummy, $domain) = self::email_split($email);
	/* Check if username starts with www. or not well-formed => reject */
	if (!preg_match('/^www\./', $email) && filter_var($email, FILTER_VALIDATE_EMAIL) !== false && $domain)
	{
		if (!getmxrr($domain, $mxhosts, $weights))
		{
			/* If we find no MX we check if domain exists */
			if (gethostbynamel($domain))
			{
				$mxhosts = array($domain);
				$weights = array(1);
			}
		}

		if (array_filter($mxhosts))	/* We need at least one valid MX */
		{
			if ($checkmailbox)
			{
				$mx = array();

				for ($i = 0; $i < count($mxhosts); $i++)
					$mx[$mxhosts[$i]] = $weights[$i];

				asort($mx, SORT_NUMERIC);
				$port = getservbyname('smtp', 'tcp');
				$from = "itools@" . (($domain = it::match('[^.]*\.(.+)', getenv('ULTRAHOSTNAME') ? getenv('ULTRAHOSTNAME') : it::exec('hostname -f 2>/dev/null || hostname 2>/dev/null'))) ? $domain : "gna.ch");

				/* Determine domain and email for test, skip if called as it_mail::check_email() */
				if (isset($this) && is_object($this))
				{
					for ($i = 0; $i < count($this->header_names); $i++)
					{
						if ($this->header_names[$i] == 'From')
						{
							$from = $this->header_values[$i];
							break;
						}
					}
				}

				if (preg_match('/@([a-z0-9.-]+\.[a-z]+)$/i', $from, $regs))
					$fromdomain = $regs[1];
				else
					$fromdomain = 'gna.ch';

				$finished = false;
				$connected = 0;

				if (function_exists('stream_set_timeout'))
					$timeout = 'stream_set_timeout';
				else
					$timeout = 'socket_set_timeout';

				foreach ($mx as $mxhost => $dummy_weight)
				{
					if ($fp = @fsockopen($mxhost, $port, $dummy_errno, $dummy_errstr, 5))
					{
						$connected++;
						$timeout($fp, 45);
						$answer = '';

						if (it_mail::send_smtp_cmd($fp, '', $answer) && it_mail::send_smtp_cmd($fp, "HELO $fromdomain", $answer) && it_mail::send_smtp_cmd($fp, "MAIL FROM: <$from>", $answer))
						{
							$timeout($fp, 2);
							$timeoutok = ($domain != 'bluewin.ch');

							if (it_mail::send_smtp_cmd($fp, "RCPT TO: <$email>", $answer, $timeoutok, 500))	# 450 is often used for Greylisting
								$result = IT_MAIL_CHECKEMAIL_OK;
							else if (preg_match('/quota|full|exceeded storage/i', $answer))
								$result = IT_MAIL_CHECKEMAIL_MAILBOXFULL;

							/* Do not try other MX if we got this far */
							$finished = true;
						}

						$timeout($fp, 0, 1);

						it_mail::send_smtp_cmd($fp, 'RSET', $answer);

						it_mail::send_smtp_cmd($fp, 'QUIT', $answer);
						fclose($fp);
					}

					if ($finished)
						break;
				}

				/* If we cannot connect to _any_ MX it could be because of temporary overload / virus attack */
				if (!$connected)
					$result = IT_MAIL_CHECKEMAIL_OK;
			}
			else
				$result = IT_MAIL_CHECKEMAIL_OK;
		}
	}

	return $result;
}

}