PhabricatorMailEmailEngine.php
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PhabricatorMailEmailEngine.php
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	<?php

	final class PhabricatorMailEmailEngine
	extends PhabricatorMailMessageEngine {

	public function newMessage() {
	$mailer = $this->getMailer();
	$mail = $this->getMail();

	$message = new PhabricatorMailEmailMessage();

	$from_address = $this->newFromEmailAddress();
	$message->setFromAddress($from_address);

	$reply_address = $this->newReplyToEmailAddress();
	if ($reply_address) {
	$message->setReplyToAddress($reply_address);
	}

	$to_addresses = $this->newToEmailAddresses();
	$cc_addresses = $this->newCCEmailAddresses();

	if (!$to_addresses && !$cc_addresses) {
	$mail->setMessage(
	pht(
	'Message has no valid recipients: all To/CC are disabled, '.
	'invalid, or configured not to receive this mail.'));
	return null;
	}

	// If this email describes a mail processing error, we rate limit outbound
	// messages to each individual address. This prevents messes where
	// something is stuck in a loop or dumps a ton of messages on us suddenly.
	if ($mail->getIsErrorEmail()) {
	$all_recipients = array();
	foreach ($to_addresses as $to_address) {
	$all_recipients[] = $to_address->getAddress();
	}
	foreach ($cc_addresses as $cc_address) {
	$all_recipients[] = $cc_address->getAddress();
	}
	if ($this->shouldRateLimitMail($all_recipients)) {
	$mail->setMessage(
	pht(
	'This is an error email, but one or more recipients have '.
	'exceeded the error email rate limit. Declining to deliver '.
	'message.'));
	return null;
	}
	}

	// Some mailers require a valid "To:" in order to deliver mail. If we
	// don't have any "To:", try to fill it in with a placeholder "To:".
	// If that also fails, move the "Cc:" line to "To:".
	if (!$to_addresses) {
	$void_address = $this->newVoidEmailAddress();
	$to_addresses = array($void_address);
	}

	$to_addresses = $this->getUniqueEmailAddresses($to_addresses);
	$cc_addresses = $this->getUniqueEmailAddresses(
	$cc_addresses,
	$to_addresses);

	$message->setToAddresses($to_addresses);
	$message->setCCAddresses($cc_addresses);

	$attachments = $this->newEmailAttachments();
	$message->setAttachments($attachments);

	$subject = $this->newEmailSubject();
	$message->setSubject($subject);

	$headers = $this->newEmailHeaders();
	foreach ($this->newEmailThreadingHeaders() as $threading_header) {
	$headers[] = $threading_header;
	}

	$stamps = $mail->getMailStamps();
	if ($stamps) {
	$headers[] = $this->newEmailHeader(
	'X-Phabricator-Stamps',
	implode(' ', $stamps));
	}

	$must_encrypt = $mail->getMustEncrypt();

	$raw_body = $mail->getBody();
	$body = $raw_body;
	if ($must_encrypt) {
	$parts = array();

	$encrypt_uri = $mail->getMustEncryptURI();
	if (!strlen($encrypt_uri)) {
	$encrypt_phid = $mail->getRelatedPHID();
	if ($encrypt_phid) {
	$encrypt_uri = urisprintf(
	'/object/%s/',
	$encrypt_phid);
	}
	}

	if (strlen($encrypt_uri)) {
	$parts[] = pht(
	'This secure message is notifying you of a change to this object:');
	$parts[] = PhabricatorEnv::getProductionURI($encrypt_uri);
	}

	$parts[] = pht(
	'The content for this message can only be transmitted over a '.
	'secure channel. To view the message content, follow this '.
	'link:');

	$parts[] = PhabricatorEnv::getProductionURI($mail->getURI());

	$body = implode("\n\n", $parts);
	} else {
	$body = $raw_body;
	}

	$body_limit = PhabricatorEnv::getEnvConfig('metamta.email-body-limit');

	$body = phutil_string_cast($body);
	if (strlen($body) > $body_limit) {
	$body = id(new PhutilUTF8StringTruncator())
	->setMaximumBytes($body_limit)
	->truncateString($body);
	$body .= "\n";
	$body .= pht('(This email was truncated at %d bytes.)', $body_limit);
	}
	$message->setTextBody($body);
	$body_limit -= strlen($body);

	// If we sent a different message body than we were asked to, record
	// what we actually sent to make debugging and diagnostics easier.
	if ($body !== $raw_body) {
	$mail->setDeliveredBody($body);
	}

	if ($must_encrypt) {
	$send_html = false;
	} else {
	$send_html = $this->shouldSendHTML();
	}

	if ($send_html) {
	$html_body = $mail->getHTMLBody();
	if (phutil_nonempty_string($html_body)) {
	// NOTE: We just drop the entire HTML body if it won't fit. Safely
	// truncating HTML is hard, and we already have the text body to fall
	// back to.
	if (strlen($html_body) <= $body_limit) {
	$message->setHTMLBody($html_body);
	$body_limit -= strlen($html_body);
	}
	}
	}

	// Pass the headers to the mailer, then save the state so we can show
	// them in the web UI. If the mail must be encrypted, we remove headers
	// which are not on a strict whitelist to avoid disclosing information.
	$filtered_headers = $this->filterHeaders($headers, $must_encrypt);
	$message->setHeaders($filtered_headers);

	$mail->setUnfilteredHeaders($headers);
	$mail->setDeliveredHeaders($headers);

	if (PhabricatorEnv::getEnvConfig('phabricator.silent')) {
	$mail->setMessage(
	pht(
	'This software is running in silent mode. See `%s` '.
	'in the configuration to change this setting.',
	'phabricator.silent'));

	return null;
	}

	return $message;
	}

	/* -( Message Components )------------------------------------------------- */

	private function newFromEmailAddress() {
	$from_address = $this->newDefaultEmailAddress();
	$mail = $this->getMail();

	// If the mail content must be encrypted, always disguise the sender.
	$must_encrypt = $mail->getMustEncrypt();
	if ($must_encrypt) {
	return $from_address;
	}

	// If we have a raw "From" address, use that.
	$raw_from = $mail->getRawFrom();
	if ($raw_from) {
	list($from_email, $from_name) = $raw_from;
	return $this->newEmailAddress($from_email, $from_name);
	}

	// Otherwise, use as much of the information for any sending entity as
	// we can.
	$from_phid = $mail->getFrom();

	$actor = $this->getActor($from_phid);
	if ($actor) {
	$actor_email = $actor->getEmailAddress();
	$actor_name = $actor->getName();
	} else {
	$actor_email = null;
	$actor_name = null;
	}

	$send_as_user = PhabricatorEnv::getEnvConfig('metamta.can-send-as-user');
	if ($send_as_user) {
	if ($actor_email !== null) {
	$from_address->setAddress($actor_email);
	}
	}

	if ($actor_name !== null) {
	$from_address->setDisplayName($actor_name);
	}

	return $from_address;
	}

	private function newReplyToEmailAddress() {
	$mail = $this->getMail();

	$reply_raw = $mail->getReplyTo();
	if (!phutil_nonempty_string($reply_raw)) {
	return null;
	}

	$reply_address = new PhutilEmailAddress($reply_raw);

	// If we have a sending object, change the display name.
	$from_phid = $mail->getFrom();
	$actor = $this->getActor($from_phid);
	if ($actor) {
	$reply_address->setDisplayName($actor->getName());
	}

	// If we don't have a display name, fill in a default.
	if (!strlen($reply_address->getDisplayName())) {
	$reply_address->setDisplayName(PlatformSymbols::getPlatformServerName());
	}

	return $reply_address;
	}

	private function newToEmailAddresses() {
	$mail = $this->getMail();

	$phids = $mail->getToPHIDs();
	$addresses = $this->newEmailAddressesFromActorPHIDs($phids);

	foreach ($mail->getRawToAddresses() as $raw_address) {
	$addresses[] = new PhutilEmailAddress($raw_address);
	}

	return $addresses;
	}

	private function newCCEmailAddresses() {
	$mail = $this->getMail();
	$phids = $mail->getCcPHIDs();
	return $this->newEmailAddressesFromActorPHIDs($phids);
	}

	private function newEmailAddressesFromActorPHIDs(array $phids) {
	$mail = $this->getMail();
	$phids = $mail->expandRecipients($phids);

	$addresses = array();
	foreach ($phids as $phid) {
	$actor = $this->getActor($phid);
	if (!$actor) {
	continue;
	}

	if (!$actor->isDeliverable()) {
	continue;
	}

	$addresses[] = new PhutilEmailAddress($actor->getEmailAddress());
	}

	return $addresses;
	}

	private function newEmailSubject() {
	$mail = $this->getMail();

	$is_threaded = (bool)$mail->getThreadID();
	$must_encrypt = $mail->getMustEncrypt();

	$subject = array();

	if ($is_threaded) {
	if ($this->shouldAddRePrefix()) {
	$subject[] = 'Re:';
	}
	}

	$subject_prefix = $mail->getSubjectPrefix();
	$subject_prefix = phutil_string_cast($subject_prefix);
	$subject_prefix = trim($subject_prefix);

	$subject[] = $subject_prefix;

	// If mail content must be encrypted, we replace the subject with
	// a generic one.
	if ($must_encrypt) {
	$encrypt_subject = $mail->getMustEncryptSubject();
	if (!strlen($encrypt_subject)) {
	$encrypt_subject = pht('Object Updated');
	}
	$subject[] = $encrypt_subject;
	} else {
	$vary_prefix = $mail->getVarySubjectPrefix();
	if (phutil_nonempty_string($vary_prefix)) {
	if ($this->shouldVarySubject()) {
	$subject[] = $vary_prefix;
	}
	}

	$subject[] = $mail->getSubject();
	}

	foreach ($subject as $key => $part) {
	if (!phutil_nonempty_string($part)) {
	unset($subject[$key]);
	}
	}

	$subject = implode(' ', $subject);
	return $subject;
	}

	private function newEmailHeaders() {
	$mail = $this->getMail();

	$headers = array();

	$headers[] = $this->newEmailHeader(
	'X-Phabricator-Sent-This-Message',
	'Yes');
	$headers[] = $this->newEmailHeader(
	'X-Mail-Transport-Agent',
	'MetaMTA');

	// Some clients respect this to suppress OOF and other auto-responses.
	$headers[] = $this->newEmailHeader(
	'X-Auto-Response-Suppress',
	'All');

	$mailtags = $mail->getMailTags();
	if ($mailtags) {
	$tag_header = array();
	foreach ($mailtags as $mailtag) {
	$tag_header[] = '<'.$mailtag.'>';
	}
	$tag_header = implode(', ', $tag_header);
	$headers[] = $this->newEmailHeader(
	'X-Phabricator-Mail-Tags',
	$tag_header);
	}

	$value = $mail->getHeaders();
	foreach ($value as $pair) {
	list($header_key, $header_value) = $pair;

	// NOTE: If we have \n in a header, SES rejects the email.
	$header_value = str_replace("\n", ' ', $header_value);
	$headers[] = $this->newEmailHeader($header_key, $header_value);
	}

	$is_bulk = $mail->getIsBulk();
	if ($is_bulk) {
	$headers[] = $this->newEmailHeader('Precedence', 'bulk');
	}

	if ($mail->getMustEncrypt()) {
	$headers[] = $this->newEmailHeader('X-Phabricator-Must-Encrypt', 'Yes');
	}

	$related_phid = $mail->getRelatedPHID();
	if ($related_phid) {
	$headers[] = $this->newEmailHeader('Thread-Topic', $related_phid);
	}

	$headers[] = $this->newEmailHeader(
	'X-Phabricator-Mail-ID',
	$mail->getID());

	$unique = Filesystem::readRandomCharacters(16);
	$headers[] = $this->newEmailHeader(
	'X-Phabricator-Send-Attempt',
	$unique);

	return $headers;
	}

	private function newEmailThreadingHeaders() {
	$mailer = $this->getMailer();
	$mail = $this->getMail();

	$headers = array();

	$thread_id = $mail->getThreadID();
	if (!phutil_nonempty_string($thread_id)) {
	return $headers;
	}

	$is_first = $mail->getIsFirstMessage();

	// NOTE: Gmail freaks out about In-Reply-To and References which aren't in
	// the form "<string@domain.tld>"; this is also required by RFC 2822,
	// although some clients are more liberal in what they accept.
	$domain = $this->newMailDomain();
	$thread_id = '<'.$thread_id.'@'.$domain.'>';

	if ($is_first && $mailer->supportsMessageIDHeader()) {
	$headers[] = $this->newEmailHeader('Message-ID', $thread_id);
	} else {
	$in_reply_to = $thread_id;
	$references = array($thread_id);
	$parent_id = $mail->getParentMessageID();
	if ($parent_id) {
	$in_reply_to = $parent_id;
	// By RFC 2822, the most immediate parent should appear last
	// in the "References" header, so this order is intentional.
	$references[] = $parent_id;
	}
	$references = implode(' ', $references);
	$headers[] = $this->newEmailHeader('In-Reply-To', $in_reply_to);
	$headers[] = $this->newEmailHeader('References', $references);
	}
	$thread_index = $this->generateThreadIndex($thread_id, $is_first);
	$headers[] = $this->newEmailHeader('Thread-Index', $thread_index);

	return $headers;
	}

	private function newEmailAttachments() {
	$mail = $this->getMail();

	// If the mail content must be encrypted, don't add attachments.
	$must_encrypt = $mail->getMustEncrypt();
	if ($must_encrypt) {
	return array();
	}

	return $mail->getAttachments();
	}

	/* -( Preferences )-------------------------------------------------------- */

	private function shouldAddRePrefix() {
	$preferences = $this->getPreferences();

	$value = $preferences->getSettingValue(
	PhabricatorEmailRePrefixSetting::SETTINGKEY);

	return ($value == PhabricatorEmailRePrefixSetting::VALUE_RE_PREFIX);
	}

	private function shouldVarySubject() {
	$preferences = $this->getPreferences();

	$value = $preferences->getSettingValue(
	PhabricatorEmailVarySubjectsSetting::SETTINGKEY);

	return ($value == PhabricatorEmailVarySubjectsSetting::VALUE_VARY_SUBJECTS);
	}

	private function shouldSendHTML() {
	$preferences = $this->getPreferences();

	$value = $preferences->getSettingValue(
	PhabricatorEmailFormatSetting::SETTINGKEY);

	return ($value == PhabricatorEmailFormatSetting::VALUE_HTML_EMAIL);
	}


	/* -( Utilities )---------------------------------------------------------- */

	private function newEmailHeader($name, $value) {
	return id(new PhabricatorMailHeader())
	->setName($name)
	->setValue($value);
	}

	private function newEmailAddress($address, $name = null) {
	$object = id(new PhutilEmailAddress())
	->setAddress($address);

	if (strlen($name)) {
	$object->setDisplayName($name);
	}

	return $object;
	}

	public function newDefaultEmailAddress() {
	$raw_address = PhabricatorEnv::getEnvConfig('metamta.default-address');

	if (!$raw_address) {
	$domain = $this->newMailDomain();
	$raw_address = "noreply@{$domain}";
	}

	$address = new PhutilEmailAddress($raw_address);

	if (!phutil_nonempty_string($address->getDisplayName())) {
	$address->setDisplayName(PlatformSymbols::getPlatformServerName());
	}

	return $address;
	}

	public function newVoidEmailAddress() {
	return $this->newDefaultEmailAddress();
	}

	private function newMailDomain() {
	$domain = PhabricatorEnv::getEnvConfig('metamta.reply-handler-domain');
	if ($domain) {
	return $domain;
	}

	$install_uri = PhabricatorEnv::getURI('/');
	$install_uri = new PhutilURI($install_uri);

	return $install_uri->getDomain();
	}

	private function filterHeaders(array $headers, $must_encrypt) {
	assert_instances_of($headers, 'PhabricatorMailHeader');

	if (!$must_encrypt) {
	return $headers;
	}

	$whitelist = array(
	'In-Reply-To',
	'Message-ID',
	'Precedence',
	'References',
	'Thread-Index',
	'Thread-Topic',

	'X-Mail-Transport-Agent',
	'X-Auto-Response-Suppress',

	'X-Phabricator-Sent-This-Message',
	'X-Phabricator-Must-Encrypt',
	'X-Phabricator-Mail-ID',
	'X-Phabricator-Send-Attempt',
	);

	// NOTE: The major header we want to drop is "X-Phabricator-Mail-Tags".
	// This header contains a significant amount of meaningful information
	// about the object.

	$whitelist_map = array();
	foreach ($whitelist as $term) {
	$whitelist_map[phutil_utf8_strtolower($term)] = true;
	}

	foreach ($headers as $key => $header) {
	$name = $header->getName();
	$name = phutil_utf8_strtolower($name);

	if (!isset($whitelist_map[$name])) {
	unset($headers[$key]);
	}
	}

	return $headers;
	}

	private function getUniqueEmailAddresses(
	array $addresses,
	array $exclude = array()) {
	assert_instances_of($addresses, 'PhutilEmailAddress');
	assert_instances_of($exclude, 'PhutilEmailAddress');

	$seen = array();

	foreach ($exclude as $address) {
	$seen[$address->getAddress()] = true;
	}

	foreach ($addresses as $key => $address) {
	$raw_address = $address->getAddress();

	if (isset($seen[$raw_address])) {
	unset($addresses[$key]);
	continue;
	}

	$seen[$raw_address] = true;
	}

	return array_values($addresses);
	}

	private function generateThreadIndex($seed, $is_first_mail) {
	// When threading, Outlook ignores the 'References' and 'In-Reply-To'
	// headers that most clients use. Instead, it uses a custom 'Thread-Index'
	// header. The format of this header is something like this (from
	// camel-exchange-folder.c in Evolution Exchange):

	/* A new post to a folder gets a 27-byte-long thread index. (The value
	* is apparently unique but meaningless.) Each reply to a post gets a
	* 32-byte-long thread index whose first 27 bytes are the same as the
	* parent's thread index. Each reply to any of those gets a
	* 37-byte-long thread index, etc. The Thread-Index header contains a
	* base64 representation of this value.
	*/

	// The specific implementation uses a 27-byte header for the first email
	// a recipient receives, and a random 5-byte suffix (32 bytes total)
	// thereafter. This means that all the replies are (incorrectly) siblings,
	// but it would be very difficult to keep track of the entire tree and this
	// gets us reasonable client behavior.

	$base = substr(md5($seed), 0, 27);
	if (!$is_first_mail) {
	// Not totally sure, but it seems like outlook orders replies by
	// thread-index rather than timestamp, so to get these to show up in the
	// right order we use the time as the last 4 bytes.
	$base .= ' '.pack('N', time());
	}

	return base64_encode($base);
	}

	private function shouldRateLimitMail(array $all_recipients) {
	try {
	PhabricatorSystemActionEngine::willTakeAction(
	$all_recipients,
	new PhabricatorMetaMTAErrorMailAction(),
	1);
	return false;
	} catch (PhabricatorSystemActionRateLimitException $ex) {
	return true;
	}
	}

	}

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