Allow mailers to be explicitly marked as inbound or outbound

Summary:
See PHI785. Ref T13164. In this case, an install wants to receive mail via Mailgun, but not configure it (DKIM + SPF) for outbound mail.

Allow individual mailers to be marked as not supporting inbound or outbound mail.

Test Plan:
  - Added and ran unit tests.
  - Went through some mail pathways locally, but I don't have every inbound/outbound configured so this isn't totally conclusive.
  - Hit `bin/mail send-test` with a no-outbound mailer.
  - I'll hold this until after the release cut so it can soak on `secure` for a bit.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13164

Differential Revision: https://secure.phabricator.com/D19546

src/applications/metamta/adapter/PhabricatorMailImplementationAdapter.php

@@ -6,6 +6,9 @@ abstract class PhabricatorMailImplementationAdapter extends Phobject {
   private $priority;
   private $options = array();
 
+  private $supportsInbound = true;
+  private $supportsOutbound = true;
+
   final public function getAdapterType() {
     return $this->getPhobjectClassConstant('ADAPTERTYPE');
   }
@@ -67,6 +70,24 @@ abstract class PhabricatorMailImplementationAdapter extends Phobject {
     return $this->priority;
   }
 
+  final public function setSupportsInbound($supports_inbound) {
+    $this->supportsInbound = $supports_inbound;
+    return $this;
+  }
+
+  final public function getSupportsInbound() {
+    return $this->supportsInbound;
+  }
+
+  final public function setSupportsOutbound($supports_outbound) {
+    $this->supportsOutbound = $supports_outbound;
+    return $this;
+  }
+
+  final public function getSupportsOutbound() {
+    return $this->supportsOutbound;
+  }
+
   final public function getOption($key) {
     if (!array_key_exists($key, $this->options)) {
       throw new Exception(

src/applications/metamta/controller/PhabricatorMetaMTAMailgunReceiveController.php

@@ -17,9 +17,12 @@ final class PhabricatorMetaMTAMailgunReceiveController
     // inbound mail from any of them. Test the signature to see if it matches
     // any configured Mailgun mailer.
 
-    $mailers = PhabricatorMetaMTAMail::newMailersWithTypes(
+    $mailers = PhabricatorMetaMTAMail::newMailers(
       array(
+        'inbound' => true,
+        'types' => array(
           PhabricatorMailImplementationMailgunAdapter::ADAPTERTYPE,
+        ),
       ));
     foreach ($mailers as $mailer) {
       $api_key = $mailer->getOption('api-key');

src/applications/metamta/controller/PhabricatorMetaMTAPostmarkReceiveController.php

@@ -12,9 +12,12 @@ final class PhabricatorMetaMTAPostmarkReceiveController
    */
   public function handleRequest(AphrontRequest $request) {
     // Don't process requests if we don't have a configured Postmark adapter.
-    $mailers = PhabricatorMetaMTAMail::newMailersWithTypes(
+    $mailers = PhabricatorMetaMTAMail::newMailers(
       array(
+        'inbound' => true,
+        'types' => array(
           PhabricatorMailImplementationPostmarkAdapter::ADAPTERTYPE,
+        ),
       ));
     if (!$mailers) {
       return new Aphront404Response();

src/applications/metamta/controller/PhabricatorMetaMTASendGridReceiveController.php

@@ -11,9 +11,12 @@ final class PhabricatorMetaMTASendGridReceiveController
     // SendGrid doesn't sign payloads so we can't be sure that SendGrid
     // actually sent this request, but require a configured SendGrid mailer
     // before we activate this endpoint.
-    $mailers = PhabricatorMetaMTAMail::newMailersWithTypes(
+    $mailers = PhabricatorMetaMTAMail::newMailers(
       array(
+        'inbound' => true,
+        'types' => array(
           PhabricatorMailImplementationSendGridAdapter::ADAPTERTYPE,
+        ),
       ));
     if (!$mailers) {
       return new Aphront404Response();

src/applications/metamta/management/PhabricatorMailManagementSendTestWorkflow.php

@@ -168,7 +168,8 @@ final class PhabricatorMailManagementSendTestWorkflow
 
     $mailer_key = $args->getArg('mailer');
     if ($mailer_key !== null) {
-      $mailers = PhabricatorMetaMTAMail::newMailers();
+      $mailers = PhabricatorMetaMTAMail::newMailers(array());
+
       $mailers = mpull($mailers, null, 'getKey');
       if (!isset($mailers[$mailer_key])) {
         throw new PhutilArgumentUsageException(
@@ -178,6 +179,13 @@ final class PhabricatorMailManagementSendTestWorkflow
             implode(', ', array_keys($mailers))));
       }
 
+      if (!$mailers[$mailer_key]->getSupportsOutbound()) {
+        throw new PhutilArgumentUsageException(
+          pht(
+            'Mailer ("%s") is not configured to support outbound mail.',
+            $mailer_key));
+      }
+
       $mail->setTryMailers(array($mailer_key));
     }
 

src/applications/metamta/storage/PhabricatorMetaMTAMail.php

@@ -494,7 +494,10 @@ final class PhabricatorMetaMTAMail
       throw new Exception(pht('Trying to send an already-sent mail!'));
     }
 
-    $mailers = self::newMailers();
+    $mailers = self::newMailers(
+      array(
+        'outbound' => true,
+      ));
 
     $try_mailers = $this->getParam('mailers.try');
     if ($try_mailers) {
@@ -505,21 +508,15 @@ final class PhabricatorMetaMTAMail
     return $this->sendWithMailers($mailers);
   }
 
-  public static function newMailersWithTypes(array $types) {
+  public static function newMailers(array $constraints) {
-    $mailers = self::newMailers();
+    PhutilTypeSpec::checkMap(
-    $types = array_fuse($types);
+      $constraints,
+      array(
+        'types' => 'optional list<string>',
+        'inbound' => 'optional bool',
+        'outbound' => 'optional bool',
+      ));
 
-    foreach ($mailers as $key => $mailer) {
-      $mailer_type = $mailer->getAdapterType();
-      if (!isset($types[$mailer_type])) {
-        unset($mailers[$key]);
-      }
-    }
-
-    return array_values($mailers);
-  }
-
-  public static function newMailers() {
     $mailers = array();
 
     $config = PhabricatorEnv::getEnvConfig('cluster.mailers');
@@ -565,10 +562,45 @@ final class PhabricatorMetaMTAMail
         $options = idx($spec, 'options', array()) + $defaults;
         $mailer->setOptions($options);
 
+        $mailer->setSupportsInbound(idx($spec, 'inbound', true));
+        $mailer->setSupportsOutbound(idx($spec, 'outbound', true));
+
         $mailers[] = $mailer;
       }
     }
 
+    // Remove mailers with the wrong types.
+    if (isset($constraints['types'])) {
+      $types = $constraints['types'];
+      $types = array_fuse($types);
+      foreach ($mailers as $key => $mailer) {
+        $mailer_type = $mailer->getAdapterType();
+        if (!isset($types[$mailer_type])) {
+          unset($mailers[$key]);
+        }
+      }
+    }
+
+    // If we're only looking for inbound mailers, remove mailers with inbound
+    // support disabled.
+    if (!empty($constraints['inbound'])) {
+      foreach ($mailers as $key => $mailer) {
+        if (!$mailer->getSupportsInbound()) {
+          unset($mailers[$key]);
+        }
+      }
+    }
+
+    // If we're only looking for outbound mailers, remove mailers with outbound
+    // support disabled.
+    if (!empty($constraints['outbound'])) {
+      foreach ($mailers as $key => $mailer) {
+        if (!$mailer->getSupportsOutbound()) {
+          unset($mailers[$key]);
+        }
+      }
+    }
+
     $sorted = array();
     $groups = mgroup($mailers, 'getPriority');
     krsort($groups);
@@ -589,9 +621,24 @@ final class PhabricatorMetaMTAMail
 
   public function sendWithMailers(array $mailers) {
     if (!$mailers) {
+      $any_mailers = self::newMailers();
+
+      // NOTE: We can end up here with some custom list of "$mailers", like
+      // from a unit test. In that case, this message could be misleading. We
+      // can't really tell if the caller made up the list, so just assume they
+      // aren't tricking us.
+
+      if ($any_mailers) {
+        $void_message = pht(
+          'No configured mailers support sending outbound mail.');
+      } else {
+        $void_message = pht(
+          'No mailers are configured.');
+      }
+
       return $this
         ->setStatus(PhabricatorMailOutboundStatus::STATUS_VOID)
-        ->setMessage(pht('No mailers are configured.'))
+        ->setMessage($void_message)
         ->save();
     }
 

src/applications/metamta/storage/__tests__/PhabricatorMailConfigTestCase.php

@@ -118,11 +118,80 @@ final class PhabricatorMailConfigTestCase
     $this->assertTrue($saw_a1 && $saw_a2);
   }
 
-  private function newMailersWithConfig(array $config) {
+  public function testMailerConstraints() {
+    $config = array(
+      array(
+        'key' => 'X1',
+        'type' => 'test',
+      ),
+      array(
+        'key' => 'X1-in',
+        'type' => 'test',
+        'outbound' => false,
+      ),
+      array(
+        'key' => 'X1-out',
+        'type' => 'test',
+        'inbound' => false,
+      ),
+      array(
+        'key' => 'X1-void',
+        'type' => 'test',
+        'inbound' => false,
+        'outbound' => false,
+      ),
+    );
+
+    $mailers = $this->newMailersWithConfig(
+      $config,
+      array());
+    $this->assertEqual(4, count($mailers));
+
+    $mailers = $this->newMailersWithConfig(
+      $config,
+      array(
+        'inbound' => true,
+      ));
+    $this->assertEqual(2, count($mailers));
+
+    $mailers = $this->newMailersWithConfig(
+      $config,
+      array(
+        'outbound' => true,
+      ));
+    $this->assertEqual(2, count($mailers));
+
+    $mailers = $this->newMailersWithConfig(
+      $config,
+      array(
+        'inbound' => true,
+        'outbound' => true,
+      ));
+    $this->assertEqual(1, count($mailers));
+
+    $mailers = $this->newMailersWithConfig(
+      $config,
+      array(
+        'types' => array('test'),
+      ));
+    $this->assertEqual(4, count($mailers));
+
+    $mailers = $this->newMailersWithConfig(
+      $config,
+      array(
+        'types' => array('duck'),
+      ));
+    $this->assertEqual(0, count($mailers));
+  }
+
+  private function newMailersWithConfig(
+    array $config,
+    array $constraints = array()) {
+
     $env = PhabricatorEnv::beginScopedEnv();
     $env->overrideEnvConfig('cluster.mailers', $config);
 
-    $mailers = PhabricatorMetaMTAMail::newMailers();
+    $mailers = PhabricatorMetaMTAMail::newMailers($constraints);
 
     unset($env);
     return $mailers;

src/docs/user/configuration/configuring_outbound_email.diviner

@@ -82,6 +82,10 @@ The supported keys for each mailer are:
   - `priority`: Optional string. Advanced option which controls load balancing
     and failover behavior. See below for details.
   - `options`: Optional map. Additional options for the mailer type.
+  - `inbound`: Optional bool. Use `false` to prevent this mailer from being
+    used to receive inbound mail.
+  - `outbound`: Optional bool. Use `false` to prevent this mailer from being
+    used to send outbound mail.
 
 The `type` field can be used to select these third-party mailers:
 

src/infrastructure/cluster/config/PhabricatorClusterMailersConfigType.php

@@ -43,6 +43,8 @@ final class PhabricatorClusterMailersConfigType
             'type' => 'string',
             'priority' => 'optional int',
             'options' => 'optional wild',
+            'inbound' => 'optional bool',
+            'outbound' => 'optional bool',
           ));
       } catch (Exception $ex) {
         throw $this->newException(