diff --git a/src/applications/files/conduit/FileAllocateConduitAPIMethod.php b/src/applications/files/conduit/FileAllocateConduitAPIMethod.php
index ddc5fa14fe..c831eb2afe 100644
--- a/src/applications/files/conduit/FileAllocateConduitAPIMethod.php
+++ b/src/applications/files/conduit/FileAllocateConduitAPIMethod.php
@@ -1,139 +1,142 @@
 <?php
 
 final class FileAllocateConduitAPIMethod
   extends FileConduitAPIMethod {
 
   public function getAPIMethodName() {
     return 'file.allocate';
   }
 
   public function getMethodDescription() {
     return pht('Prepare to upload a file.');
   }
 
   protected function defineParamTypes() {
     return array(
       'name' => 'string',
       'contentLength' => 'int',
       'contentHash' => 'optional string',
       'viewPolicy' => 'optional string',
       'deleteAfterEpoch' => 'optional int',
     );
   }
 
   protected function defineReturnType() {
     return 'map<string, wild>';
   }
 
   protected function execute(ConduitAPIRequest $request) {
     $viewer = $request->getUser();
 
     $hash = $request->getValue('contentHash');
     $name = $request->getValue('name');
     $view_policy = $request->getValue('viewPolicy');
     $length = $request->getValue('contentLength');
 
     $properties = array(
       'name' => $name,
       'authorPHID' => $viewer->getPHID(),
-      'viewPolicy' => $view_policy,
       'isExplicitUpload' => true,
     );
 
+    if ($view_policy !== null) {
+      $properties['viewPolicy'] = $view_policy;
+    }
+
     $ttl = $request->getValue('deleteAfterEpoch');
     if ($ttl) {
       $properties['ttl.absolute'] = $ttl;
     }
 
     $file = null;
-    if ($hash) {
+    if ($hash !== null) {
       $file = PhabricatorFile::newFileFromContentHash(
         $hash,
         $properties);
     }
 
-    if ($hash && !$file) {
+    if ($hash !== null && !$file) {
       $chunked_hash = PhabricatorChunkedFileStorageEngine::getChunkedHash(
         $viewer,
         $hash);
       $file = id(new PhabricatorFileQuery())
         ->setViewer($viewer)
         ->withContentHashes(array($chunked_hash))
         ->executeOne();
     }
 
     if (strlen($name) && !$hash && !$file) {
       if ($length > PhabricatorFileStorageEngine::getChunkThreshold()) {
         // If we don't have a hash, but this file is large enough to store in
         // chunks and thus may be resumable, try to find a partially uploaded
         // file by the same author with the same name and same length. This
         // allows us to resume uploads in Javascript where we can't efficiently
         // compute file hashes.
         $file = id(new PhabricatorFileQuery())
           ->setViewer($viewer)
           ->withAuthorPHIDs(array($viewer->getPHID()))
           ->withNames(array($name))
           ->withLengthBetween($length, $length)
           ->withIsPartial(true)
           ->setLimit(1)
           ->executeOne();
       }
     }
 
     if ($file) {
       return array(
         'upload' => (bool)$file->getIsPartial(),
         'filePHID' => $file->getPHID(),
       );
     }
 
     // If there are any non-chunk engines which this file can fit into,
     // just tell the client to upload the file.
     $engines = PhabricatorFileStorageEngine::loadStorageEngines($length);
     if ($engines) {
       return array(
         'upload' => true,
         'filePHID' => null,
       );
     }
 
     // Otherwise, this is a large file and we want to perform a chunked
     // upload if we have a chunk engine available.
     $chunk_engines = PhabricatorFileStorageEngine::loadWritableChunkEngines();
     if ($chunk_engines) {
       $chunk_properties = $properties;
 
-      if ($hash) {
+      if ($hash !== null) {
         $chunk_properties += array(
           'chunkedHash' => $chunked_hash,
         );
       }
 
       $chunk_engine = head($chunk_engines);
       $file = $chunk_engine->allocateChunks($length, $chunk_properties);
 
       return array(
         'upload' => true,
         'filePHID' => $file->getPHID(),
       );
     }
 
     // None of the storage engines can accept this file.
     if (PhabricatorFileStorageEngine::loadWritableEngines()) {
       $error = pht(
         'Unable to upload file: this file is too large for any '.
         'configured storage engine.');
     } else {
       $error = pht(
         'Unable to upload file: the server is not configured with any '.
         'writable storage engines.');
     }
 
     return array(
       'upload' => false,
       'filePHID' => null,
       'error' => $error,
     );
   }
 
 }
diff --git a/src/applications/files/conduit/FileUploadConduitAPIMethod.php b/src/applications/files/conduit/FileUploadConduitAPIMethod.php
index ac93b7d39a..8b3b9faaaa 100644
--- a/src/applications/files/conduit/FileUploadConduitAPIMethod.php
+++ b/src/applications/files/conduit/FileUploadConduitAPIMethod.php
@@ -1,49 +1,55 @@
 <?php
 
 final class FileUploadConduitAPIMethod extends FileConduitAPIMethod {
 
   public function getAPIMethodName() {
     return 'file.upload';
   }
 
   public function getMethodDescription() {
     return pht('Upload a file to the server.');
   }
 
   protected function defineParamTypes() {
     return array(
       'data_base64' => 'required nonempty base64-bytes',
       'name' => 'optional string',
       'viewPolicy' => 'optional valid policy string or <phid>',
       'canCDN' => 'optional bool',
     );
   }
 
   protected function defineReturnType() {
     return 'nonempty guid';
   }
 
   protected function execute(ConduitAPIRequest $request) {
     $viewer = $request->getUser();
 
     $name = $request->getValue('name');
-    $can_cdn = $request->getValue('canCDN');
+    $can_cdn = (bool)$request->getValue('canCDN');
     $view_policy = $request->getValue('viewPolicy');
 
     $data = $request->getValue('data_base64');
     $data = $this->decodeBase64($data);
 
-    $file = PhabricatorFile::newFromFileData(
-      $data,
-      array(
-        'name' => $name,
-        'authorPHID' => $viewer->getPHID(),
-        'viewPolicy' => $view_policy,
-        'canCDN' => $can_cdn,
-        'isExplicitUpload' => true,
-      ));
+    $params = array(
+      'authorPHID' => $viewer->getPHID(),
+      'canCDN' => $can_cdn,
+      'isExplicitUpload' => true,
+    );
+
+    if ($name !== null) {
+      $params['name'] = $name;
+    }
+
+    if ($view_policy !== null) {
+      $params['viewPolicy'] = $view_policy;
+    }
+
+    $file = PhabricatorFile::newFromFileData($data, $params);
 
     return $file->getPHID();
   }
 
 }
diff --git a/src/applications/files/storage/PhabricatorFile.php b/src/applications/files/storage/PhabricatorFile.php
index a7dd6b2e97..08160f7cbc 100644
--- a/src/applications/files/storage/PhabricatorFile.php
+++ b/src/applications/files/storage/PhabricatorFile.php
@@ -1,1524 +1,1530 @@
 <?php
 
 /**
  * Parameters
  * ==========
  *
  * When creating a new file using a method like @{method:newFromFileData}, these
  * parameters are supported:
  *
  *   | name | Human readable filename.
  *   | authorPHID | User PHID of uploader.
  *   | ttl.absolute | Temporary file lifetime as an epoch timestamp.
  *   | ttl.relative | Temporary file lifetime, relative to now, in seconds.
  *   | viewPolicy | File visibility policy.
  *   | isExplicitUpload | Used to show users files they explicitly uploaded.
  *   | canCDN | Allows the file to be cached and delivered over a CDN.
  *   | profile | Marks the file as a profile image.
  *   | format | Internal encoding format.
  *   | mime-type | Optional, explicit file MIME type.
  *   | builtin | Optional filename, identifies this as a builtin.
  *
  */
 final class PhabricatorFile extends PhabricatorFileDAO
   implements
     PhabricatorApplicationTransactionInterface,
     PhabricatorTokenReceiverInterface,
     PhabricatorSubscribableInterface,
     PhabricatorFlaggableInterface,
     PhabricatorPolicyInterface,
     PhabricatorDestructibleInterface,
     PhabricatorConduitResultInterface {
 
   const METADATA_IMAGE_WIDTH  = 'width';
   const METADATA_IMAGE_HEIGHT = 'height';
   const METADATA_CAN_CDN = 'canCDN';
   const METADATA_BUILTIN = 'builtin';
   const METADATA_PARTIAL = 'partial';
   const METADATA_PROFILE = 'profile';
   const METADATA_STORAGE = 'storage';
 
   protected $name;
   protected $mimeType;
   protected $byteSize;
   protected $authorPHID;
   protected $secretKey;
   protected $contentHash;
   protected $metadata = array();
   protected $mailKey;
   protected $builtinKey;
 
   protected $storageEngine;
   protected $storageFormat;
   protected $storageHandle;
 
   protected $ttl;
   protected $isExplicitUpload = 1;
   protected $viewPolicy = PhabricatorPolicies::POLICY_USER;
   protected $isPartial = 0;
 
   private $objects = self::ATTACHABLE;
   private $objectPHIDs = self::ATTACHABLE;
   private $originalFile = self::ATTACHABLE;
   private $transforms = self::ATTACHABLE;
 
   public static function initializeNewFile() {
     $app = id(new PhabricatorApplicationQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withClasses(array('PhabricatorFilesApplication'))
       ->executeOne();
 
     $view_policy = $app->getPolicy(
       FilesDefaultViewCapability::CAPABILITY);
 
     return id(new PhabricatorFile())
       ->setViewPolicy($view_policy)
       ->setIsPartial(0)
       ->attachOriginalFile(null)
       ->attachObjects(array())
       ->attachObjectPHIDs(array());
   }
 
   protected function getConfiguration() {
     return array(
       self::CONFIG_AUX_PHID => true,
       self::CONFIG_SERIALIZATION => array(
         'metadata' => self::SERIALIZATION_JSON,
       ),
       self::CONFIG_COLUMN_SCHEMA => array(
         'name' => 'text255?',
         'mimeType' => 'text255?',
         'byteSize' => 'uint64',
         'storageEngine' => 'text32',
         'storageFormat' => 'text32',
         'storageHandle' => 'text255',
         'authorPHID' => 'phid?',
         'secretKey' => 'bytes20?',
         'contentHash' => 'bytes40?',
         'ttl' => 'epoch?',
         'isExplicitUpload' => 'bool?',
         'mailKey' => 'bytes20',
         'isPartial' => 'bool',
         'builtinKey' => 'text64?',
       ),
       self::CONFIG_KEY_SCHEMA => array(
         'key_phid' => null,
         'phid' => array(
           'columns' => array('phid'),
           'unique' => true,
         ),
         'authorPHID' => array(
           'columns' => array('authorPHID'),
         ),
         'contentHash' => array(
           'columns' => array('contentHash'),
         ),
         'key_ttl' => array(
           'columns' => array('ttl'),
         ),
         'key_dateCreated' => array(
           'columns' => array('dateCreated'),
         ),
         'key_partial' => array(
           'columns' => array('authorPHID', 'isPartial'),
         ),
         'key_builtin' => array(
           'columns' => array('builtinKey'),
           'unique' => true,
         ),
       ),
     ) + parent::getConfiguration();
   }
 
   public function generatePHID() {
     return PhabricatorPHID::generateNewPHID(
       PhabricatorFileFilePHIDType::TYPECONST);
   }
 
   public function save() {
     if (!$this->getSecretKey()) {
       $this->setSecretKey($this->generateSecretKey());
     }
     if (!$this->getMailKey()) {
       $this->setMailKey(Filesystem::readRandomCharacters(20));
     }
     return parent::save();
   }
 
   public function getMonogram() {
     return 'F'.$this->getID();
   }
 
   public function scrambleSecret() {
     return $this->setSecretKey($this->generateSecretKey());
   }
 
   public static function readUploadedFileData($spec) {
     if (!$spec) {
       throw new Exception(pht('No file was uploaded!'));
     }
 
     $err = idx($spec, 'error');
     if ($err) {
       throw new PhabricatorFileUploadException($err);
     }
 
     $tmp_name = idx($spec, 'tmp_name');
     $is_valid = @is_uploaded_file($tmp_name);
     if (!$is_valid) {
       throw new Exception(pht('File is not an uploaded file.'));
     }
 
     $file_data = Filesystem::readFile($tmp_name);
     $file_size = idx($spec, 'size');
 
     if (strlen($file_data) != $file_size) {
       throw new Exception(pht('File size disagrees with uploaded size.'));
     }
 
     return $file_data;
   }
 
   public static function newFromPHPUpload($spec, array $params = array()) {
     $file_data = self::readUploadedFileData($spec);
 
     $file_name = nonempty(
       idx($params, 'name'),
       idx($spec,   'name'));
     $params = array(
       'name' => $file_name,
     ) + $params;
 
     return self::newFromFileData($file_data, $params);
   }
 
   public static function newFromXHRUpload($data, array $params = array()) {
     return self::newFromFileData($data, $params);
   }
 
 
   public static function newFileFromContentHash($hash, array $params) {
-    // Check to see if a file with same contentHash exist
+    if ($hash === null) {
+      return null;
+    }
+
+    // Check to see if a file with same hash already exists.
     $file = id(new PhabricatorFile())->loadOneWhere(
       'contentHash = %s LIMIT 1',
       $hash);
+    if (!$file) {
+      return null;
+    }
 
-    if ($file) {
-      $copy_of_storage_engine = $file->getStorageEngine();
-      $copy_of_storage_handle = $file->getStorageHandle();
-      $copy_of_storage_format = $file->getStorageFormat();
-      $copy_of_storage_properties = $file->getStorageProperties();
-      $copy_of_byte_size = $file->getByteSize();
-      $copy_of_mime_type = $file->getMimeType();
-
-      $new_file = self::initializeNewFile();
+    $copy_of_storage_engine = $file->getStorageEngine();
+    $copy_of_storage_handle = $file->getStorageHandle();
+    $copy_of_storage_format = $file->getStorageFormat();
+    $copy_of_storage_properties = $file->getStorageProperties();
+    $copy_of_byte_size = $file->getByteSize();
+    $copy_of_mime_type = $file->getMimeType();
 
-      $new_file->setByteSize($copy_of_byte_size);
+    $new_file = self::initializeNewFile();
 
-      $new_file->setContentHash($hash);
-      $new_file->setStorageEngine($copy_of_storage_engine);
-      $new_file->setStorageHandle($copy_of_storage_handle);
-      $new_file->setStorageFormat($copy_of_storage_format);
-      $new_file->setStorageProperties($copy_of_storage_properties);
-      $new_file->setMimeType($copy_of_mime_type);
-      $new_file->copyDimensions($file);
+    $new_file->setByteSize($copy_of_byte_size);
 
-      $new_file->readPropertiesFromParameters($params);
+    $new_file->setContentHash($hash);
+    $new_file->setStorageEngine($copy_of_storage_engine);
+    $new_file->setStorageHandle($copy_of_storage_handle);
+    $new_file->setStorageFormat($copy_of_storage_format);
+    $new_file->setStorageProperties($copy_of_storage_properties);
+    $new_file->setMimeType($copy_of_mime_type);
+    $new_file->copyDimensions($file);
 
-      $new_file->save();
+    $new_file->readPropertiesFromParameters($params);
 
-      return $new_file;
-    }
+    $new_file->save();
 
-    return $file;
+    return $new_file;
   }
 
   public static function newChunkedFile(
     PhabricatorFileStorageEngine $engine,
     $length,
     array $params) {
 
     $file = self::initializeNewFile();
 
     $file->setByteSize($length);
 
     // NOTE: Once we receive the first chunk, we'll detect its MIME type and
     // update the parent file. This matters for large media files like video.
     $file->setMimeType('application/octet-stream');
 
     $chunked_hash = idx($params, 'chunkedHash');
     if ($chunked_hash) {
       $file->setContentHash($chunked_hash);
     } else {
       // See PhabricatorChunkedFileStorageEngine::getChunkedHash() for some
       // discussion of this.
       $seed = Filesystem::readRandomBytes(64);
       $hash = PhabricatorChunkedFileStorageEngine::getChunkedHashForInput(
         $seed);
       $file->setContentHash($hash);
     }
 
     $file->setStorageEngine($engine->getEngineIdentifier());
     $file->setStorageHandle(PhabricatorFileChunk::newChunkHandle());
 
     // Chunked files are always stored raw because they do not actually store
     // data. The chunks do, and can be individually formatted.
     $file->setStorageFormat(PhabricatorFileRawStorageFormat::FORMATKEY);
 
     $file->setIsPartial(1);
 
     $file->readPropertiesFromParameters($params);
 
     return $file;
   }
 
   private static function buildFromFileData($data, array $params = array()) {
 
     if (isset($params['storageEngines'])) {
       $engines = $params['storageEngines'];
     } else {
       $size = strlen($data);
       $engines = PhabricatorFileStorageEngine::loadStorageEngines($size);
 
       if (!$engines) {
         throw new Exception(
           pht(
             'No configured storage engine can store this file. See '.
             '"Configuring File Storage" in the documentation for '.
             'information on configuring storage engines.'));
       }
     }
 
     assert_instances_of($engines, 'PhabricatorFileStorageEngine');
     if (!$engines) {
       throw new Exception(pht('No valid storage engines are available!'));
     }
 
     $file = self::initializeNewFile();
 
     $aes_type = PhabricatorFileAES256StorageFormat::FORMATKEY;
     $has_aes = PhabricatorKeyring::getDefaultKeyName($aes_type);
     if ($has_aes !== null) {
       $default_key = PhabricatorFileAES256StorageFormat::FORMATKEY;
     } else {
       $default_key = PhabricatorFileRawStorageFormat::FORMATKEY;
     }
     $key = idx($params, 'format', $default_key);
 
     // Callers can pass in an object explicitly instead of a key. This is
     // primarily useful for unit tests.
     if ($key instanceof PhabricatorFileStorageFormat) {
       $format = clone $key;
     } else {
       $format = clone PhabricatorFileStorageFormat::requireFormat($key);
     }
 
     $format->setFile($file);
 
     $properties = $format->newStorageProperties();
     $file->setStorageFormat($format->getStorageFormatKey());
     $file->setStorageProperties($properties);
 
     $data_handle = null;
     $engine_identifier = null;
     $exceptions = array();
     foreach ($engines as $engine) {
       $engine_class = get_class($engine);
       try {
         list($engine_identifier, $data_handle) = $file->writeToEngine(
           $engine,
           $data,
           $params);
 
         // We stored the file somewhere so stop trying to write it to other
         // places.
         break;
       } catch (PhabricatorFileStorageConfigurationException $ex) {
         // If an engine is outright misconfigured (or misimplemented), raise
         // that immediately since it probably needs attention.
         throw $ex;
       } catch (Exception $ex) {
         phlog($ex);
 
         // If an engine doesn't work, keep trying all the other valid engines
         // in case something else works.
         $exceptions[$engine_class] = $ex;
       }
     }
 
     if (!$data_handle) {
       throw new PhutilAggregateException(
         pht('All storage engines failed to write file:'),
         $exceptions);
     }
 
     $file->setByteSize(strlen($data));
-    $file->setContentHash(self::hashFileContent($data));
+
+    $hash = self::hashFileContent($data);
+    $file->setContentHash($hash);
 
     $file->setStorageEngine($engine_identifier);
     $file->setStorageHandle($data_handle);
 
     $file->readPropertiesFromParameters($params);
 
     if (!$file->getMimeType()) {
       $tmp = new TempFile();
       Filesystem::writeFile($tmp, $data);
       $file->setMimeType(Filesystem::getMimeType($tmp));
     }
 
     try {
       $file->updateDimensions(false);
     } catch (Exception $ex) {
       // Do nothing
     }
 
     $file->save();
 
     return $file;
   }
 
   public static function newFromFileData($data, array $params = array()) {
     $hash = self::hashFileContent($data);
-    $file = self::newFileFromContentHash($hash, $params);
 
-    if ($file) {
-      return $file;
+    if ($hash !== null) {
+      $file = self::newFileFromContentHash($hash, $params);
+      if ($file) {
+        return $file;
+      }
     }
 
     return self::buildFromFileData($data, $params);
   }
 
   public function migrateToEngine(
     PhabricatorFileStorageEngine $engine,
     $make_copy) {
 
     if (!$this->getID() || !$this->getStorageHandle()) {
       throw new Exception(
         pht("You can not migrate a file which hasn't yet been saved."));
     }
 
     $data = $this->loadFileData();
     $params = array(
       'name' => $this->getName(),
     );
 
     list($new_identifier, $new_handle) = $this->writeToEngine(
       $engine,
       $data,
       $params);
 
     $old_engine = $this->instantiateStorageEngine();
     $old_identifier = $this->getStorageEngine();
     $old_handle = $this->getStorageHandle();
 
     $this->setStorageEngine($new_identifier);
     $this->setStorageHandle($new_handle);
     $this->save();
 
     if (!$make_copy) {
       $this->deleteFileDataIfUnused(
         $old_engine,
         $old_identifier,
         $old_handle);
     }
 
     return $this;
   }
 
   public function migrateToStorageFormat(PhabricatorFileStorageFormat $format) {
     if (!$this->getID() || !$this->getStorageHandle()) {
       throw new Exception(
         pht("You can not migrate a file which hasn't yet been saved."));
     }
 
     $data = $this->loadFileData();
     $params = array(
       'name' => $this->getName(),
     );
 
     $engine = $this->instantiateStorageEngine();
     $old_handle = $this->getStorageHandle();
 
     $properties = $format->newStorageProperties();
     $this->setStorageFormat($format->getStorageFormatKey());
     $this->setStorageProperties($properties);
 
     list($identifier, $new_handle) = $this->writeToEngine(
       $engine,
       $data,
       $params);
 
     $this->setStorageHandle($new_handle);
     $this->save();
 
     $this->deleteFileDataIfUnused(
       $engine,
       $identifier,
       $old_handle);
 
     return $this;
   }
 
   public function cycleMasterStorageKey(PhabricatorFileStorageFormat $format) {
     if (!$this->getID() || !$this->getStorageHandle()) {
       throw new Exception(
         pht("You can not cycle keys for a file which hasn't yet been saved."));
     }
 
     $properties = $format->cycleStorageProperties();
     $this->setStorageProperties($properties);
     $this->save();
 
     return $this;
   }
 
   private function writeToEngine(
     PhabricatorFileStorageEngine $engine,
     $data,
     array $params) {
 
     $engine_class = get_class($engine);
 
     $key = $this->getStorageFormat();
     $format = id(clone PhabricatorFileStorageFormat::requireFormat($key))
       ->setFile($this);
 
     $data_iterator = array($data);
     $formatted_iterator = $format->newWriteIterator($data_iterator);
     $formatted_data = $this->loadDataFromIterator($formatted_iterator);
 
     $data_handle = $engine->writeFile($formatted_data, $params);
 
     if (!$data_handle || strlen($data_handle) > 255) {
       // This indicates an improperly implemented storage engine.
       throw new PhabricatorFileStorageConfigurationException(
         pht(
           "Storage engine '%s' executed %s but did not return a valid ".
           "handle ('%s') to the data: it must be nonempty and no longer ".
           "than 255 characters.",
           $engine_class,
           'writeFile()',
           $data_handle));
     }
 
     $engine_identifier = $engine->getEngineIdentifier();
     if (!$engine_identifier || strlen($engine_identifier) > 32) {
       throw new PhabricatorFileStorageConfigurationException(
         pht(
           "Storage engine '%s' returned an improper engine identifier '{%s}': ".
           "it must be nonempty and no longer than 32 characters.",
           $engine_class,
           $engine_identifier));
     }
 
     return array($engine_identifier, $data_handle);
   }
 
 
   /**
    * Download a remote resource over HTTP and save the response body as a file.
    *
    * This method respects `security.outbound-blacklist`, and protects against
    * HTTP redirection (by manually following "Location" headers and verifying
    * each destination). It does not protect against DNS rebinding. See
    * discussion in T6755.
    */
   public static function newFromFileDownload($uri, array $params = array()) {
     $timeout = 5;
 
     $redirects = array();
     $current = $uri;
     while (true) {
       try {
         if (count($redirects) > 10) {
           throw new Exception(
             pht('Too many redirects trying to fetch remote URI.'));
         }
 
         $resolved = PhabricatorEnv::requireValidRemoteURIForFetch(
           $current,
           array(
             'http',
             'https',
           ));
 
         list($resolved_uri, $resolved_domain) = $resolved;
 
         $current = new PhutilURI($current);
         if ($current->getProtocol() == 'http') {
           // For HTTP, we can use a pre-resolved URI to defuse DNS rebinding.
           $fetch_uri = $resolved_uri;
           $fetch_host = $resolved_domain;
         } else {
           // For HTTPS, we can't: cURL won't verify the SSL certificate if
           // the domain has been replaced with an IP. But internal services
           // presumably will not have valid certificates for rebindable
           // domain names on attacker-controlled domains, so the DNS rebinding
           // attack should generally not be possible anyway.
           $fetch_uri = $current;
           $fetch_host = null;
         }
 
         $future = id(new HTTPSFuture($fetch_uri))
           ->setFollowLocation(false)
           ->setTimeout($timeout);
 
         if ($fetch_host !== null) {
           $future->addHeader('Host', $fetch_host);
         }
 
         list($status, $body, $headers) = $future->resolve();
 
         if ($status->isRedirect()) {
           // This is an HTTP 3XX status, so look for a "Location" header.
           $location = null;
           foreach ($headers as $header) {
             list($name, $value) = $header;
             if (phutil_utf8_strtolower($name) == 'location') {
               $location = $value;
               break;
             }
           }
 
           // HTTP 3XX status with no "Location" header, just treat this like
           // a normal HTTP error.
           if ($location === null) {
             throw $status;
           }
 
           if (isset($redirects[$location])) {
             throw new Exception(
               pht('Encountered loop while following redirects.'));
           }
 
           $redirects[$location] = $location;
           $current = $location;
           // We'll fall off the bottom and go try this URI now.
         } else if ($status->isError()) {
           // This is something other than an HTTP 2XX or HTTP 3XX status, so
           // just bail out.
           throw $status;
         } else {
           // This is HTTP 2XX, so use the response body to save the
           // file data.
           $params = $params + array(
             'name' => basename($uri),
           );
 
           return self::newFromFileData($body, $params);
         }
       } catch (Exception $ex) {
         if ($redirects) {
           throw new PhutilProxyException(
             pht(
               'Failed to fetch remote URI "%s" after following %s redirect(s) '.
               '(%s): %s',
               $uri,
               phutil_count($redirects),
               implode(' > ', array_keys($redirects)),
               $ex->getMessage()),
             $ex);
         } else {
           throw $ex;
         }
       }
     }
   }
 
   public static function normalizeFileName($file_name) {
     $pattern = "@[\\x00-\\x19#%&+!~'\$\"\/=\\\\?<> ]+@";
     $file_name = preg_replace($pattern, '_', $file_name);
     $file_name = preg_replace('@_+@', '_', $file_name);
     $file_name = trim($file_name, '_');
 
     $disallowed_filenames = array(
       '.'  => 'dot',
       '..' => 'dotdot',
       ''   => 'file',
     );
     $file_name = idx($disallowed_filenames, $file_name, $file_name);
 
     return $file_name;
   }
 
   public function delete() {
     // We want to delete all the rows which mark this file as the transformation
     // of some other file (since we're getting rid of it). We also delete all
     // the transformations of this file, so that a user who deletes an image
     // doesn't need to separately hunt down and delete a bunch of thumbnails and
     // resizes of it.
 
     $outbound_xforms = id(new PhabricatorFileQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withTransforms(
         array(
           array(
             'originalPHID' => $this->getPHID(),
             'transform'    => true,
           ),
         ))
       ->execute();
 
     foreach ($outbound_xforms as $outbound_xform) {
       $outbound_xform->delete();
     }
 
     $inbound_xforms = id(new PhabricatorTransformedFile())->loadAllWhere(
       'transformedPHID = %s',
       $this->getPHID());
 
     $this->openTransaction();
       foreach ($inbound_xforms as $inbound_xform) {
         $inbound_xform->delete();
       }
       $ret = parent::delete();
     $this->saveTransaction();
 
     $this->deleteFileDataIfUnused(
       $this->instantiateStorageEngine(),
       $this->getStorageEngine(),
       $this->getStorageHandle());
 
     return $ret;
   }
 
 
   /**
    * Destroy stored file data if there are no remaining files which reference
    * it.
    */
   public function deleteFileDataIfUnused(
     PhabricatorFileStorageEngine $engine,
     $engine_identifier,
     $handle) {
 
     // Check to see if any files are using storage.
     $usage = id(new PhabricatorFile())->loadAllWhere(
       'storageEngine = %s AND storageHandle = %s LIMIT 1',
       $engine_identifier,
       $handle);
 
     // If there are no files using the storage, destroy the actual storage.
     if (!$usage) {
       try {
         $engine->deleteFile($handle);
       } catch (Exception $ex) {
         // In the worst case, we're leaving some data stranded in a storage
         // engine, which is not a big deal.
         phlog($ex);
       }
     }
   }
 
-
   public static function hashFileContent($data) {
-    return sha1($data);
+    return null;
   }
 
   public function loadFileData() {
     $iterator = $this->getFileDataIterator();
     return $this->loadDataFromIterator($iterator);
   }
 
 
   /**
    * Return an iterable which emits file content bytes.
    *
    * @param int Offset for the start of data.
    * @param int Offset for the end of data.
    * @return Iterable Iterable object which emits requested data.
    */
   public function getFileDataIterator($begin = null, $end = null) {
     $engine = $this->instantiateStorageEngine();
     $raw_iterator = $engine->getRawFileDataIterator($this, $begin, $end);
 
     $key = $this->getStorageFormat();
 
     $format = id(clone PhabricatorFileStorageFormat::requireFormat($key))
       ->setFile($this);
 
     return $format->newReadIterator($raw_iterator);
   }
 
   public function getURI() {
     return $this->getInfoURI();
   }
 
   public function getViewURI() {
     if (!$this->getPHID()) {
       throw new Exception(
         pht('You must save a file before you can generate a view URI.'));
     }
 
     return $this->getCDNURI();
   }
 
   public function getCDNURI() {
     $name = self::normalizeFileName($this->getName());
     $name = phutil_escape_uri($name);
 
     $parts = array();
     $parts[] = 'file';
     $parts[] = 'data';
 
     // If this is an instanced install, add the instance identifier to the URI.
     // Instanced configurations behind a CDN may not be able to control the
     // request domain used by the CDN (as with AWS CloudFront). Embedding the
     // instance identity in the path allows us to distinguish between requests
     // originating from different instances but served through the same CDN.
     $instance = PhabricatorEnv::getEnvConfig('cluster.instance');
     if (strlen($instance)) {
       $parts[] = '@'.$instance;
     }
 
     $parts[] = $this->getSecretKey();
     $parts[] = $this->getPHID();
     $parts[] = $name;
 
     $path = '/'.implode('/', $parts);
 
     // If this file is only partially uploaded, we're just going to return a
     // local URI to make sure that Ajax works, since the page is inevitably
     // going to give us an error back.
     if ($this->getIsPartial()) {
       return PhabricatorEnv::getURI($path);
     } else {
       return PhabricatorEnv::getCDNURI($path);
     }
   }
 
 
   public function getInfoURI() {
     return '/'.$this->getMonogram();
   }
 
   public function getBestURI() {
     if ($this->isViewableInBrowser()) {
       return $this->getViewURI();
     } else {
       return $this->getInfoURI();
     }
   }
 
   public function getDownloadURI() {
     $uri = id(new PhutilURI($this->getViewURI()))
       ->setQueryParam('download', true);
     return (string)$uri;
   }
 
   public function getURIForTransform(PhabricatorFileTransform $transform) {
     return $this->getTransformedURI($transform->getTransformKey());
   }
 
   private function getTransformedURI($transform) {
     $parts = array();
     $parts[] = 'file';
     $parts[] = 'xform';
 
     $instance = PhabricatorEnv::getEnvConfig('cluster.instance');
     if (strlen($instance)) {
       $parts[] = '@'.$instance;
     }
 
     $parts[] = $transform;
     $parts[] = $this->getPHID();
     $parts[] = $this->getSecretKey();
 
     $path = implode('/', $parts);
     $path = $path.'/';
 
     return PhabricatorEnv::getCDNURI($path);
   }
 
   public function isViewableInBrowser() {
     return ($this->getViewableMimeType() !== null);
   }
 
   public function isViewableImage() {
     if (!$this->isViewableInBrowser()) {
       return false;
     }
 
     $mime_map = PhabricatorEnv::getEnvConfig('files.image-mime-types');
     $mime_type = $this->getMimeType();
     return idx($mime_map, $mime_type);
   }
 
   public function isAudio() {
     if (!$this->isViewableInBrowser()) {
       return false;
     }
 
     $mime_map = PhabricatorEnv::getEnvConfig('files.audio-mime-types');
     $mime_type = $this->getMimeType();
     return idx($mime_map, $mime_type);
   }
 
   public function isVideo() {
     if (!$this->isViewableInBrowser()) {
       return false;
     }
 
     $mime_map = PhabricatorEnv::getEnvConfig('files.video-mime-types');
     $mime_type = $this->getMimeType();
     return idx($mime_map, $mime_type);
   }
 
   public function isTransformableImage() {
     // NOTE: The way the 'gd' extension works in PHP is that you can install it
     // with support for only some file types, so it might be able to handle
     // PNG but not JPEG. Try to generate thumbnails for whatever we can. Setup
     // warns you if you don't have complete support.
 
     $matches = null;
     $ok = preg_match(
       '@^image/(gif|png|jpe?g)@',
       $this->getViewableMimeType(),
       $matches);
     if (!$ok) {
       return false;
     }
 
     switch ($matches[1]) {
       case 'jpg';
       case 'jpeg':
         return function_exists('imagejpeg');
         break;
       case 'png':
         return function_exists('imagepng');
         break;
       case 'gif':
         return function_exists('imagegif');
         break;
       default:
         throw new Exception(pht('Unknown type matched as image MIME type.'));
     }
   }
 
   public static function getTransformableImageFormats() {
     $supported = array();
 
     if (function_exists('imagejpeg')) {
       $supported[] = 'jpg';
     }
 
     if (function_exists('imagepng')) {
       $supported[] = 'png';
     }
 
     if (function_exists('imagegif')) {
       $supported[] = 'gif';
     }
 
     return $supported;
   }
 
   public function getDragAndDropDictionary() {
     return array(
       'id'   => $this->getID(),
       'phid' => $this->getPHID(),
       'uri'  => $this->getBestURI(),
     );
   }
 
   public function instantiateStorageEngine() {
     return self::buildEngine($this->getStorageEngine());
   }
 
   public static function buildEngine($engine_identifier) {
     $engines = self::buildAllEngines();
     foreach ($engines as $engine) {
       if ($engine->getEngineIdentifier() == $engine_identifier) {
         return $engine;
       }
     }
 
     throw new Exception(
       pht(
         "Storage engine '%s' could not be located!",
         $engine_identifier));
   }
 
   public static function buildAllEngines() {
     return id(new PhutilClassMapQuery())
       ->setAncestorClass('PhabricatorFileStorageEngine')
       ->execute();
   }
 
   public function getViewableMimeType() {
     $mime_map = PhabricatorEnv::getEnvConfig('files.viewable-mime-types');
 
     $mime_type = $this->getMimeType();
     $mime_parts = explode(';', $mime_type);
     $mime_type = trim(reset($mime_parts));
 
     return idx($mime_map, $mime_type);
   }
 
   public function getDisplayIconForMimeType() {
     $mime_map = PhabricatorEnv::getEnvConfig('files.icon-mime-types');
     $mime_type = $this->getMimeType();
     return idx($mime_map, $mime_type, 'fa-file-o');
   }
 
   public function validateSecretKey($key) {
     return ($key == $this->getSecretKey());
   }
 
   public function generateSecretKey() {
     return Filesystem::readRandomCharacters(20);
   }
 
   public function setStorageProperties(array $properties) {
     $this->metadata[self::METADATA_STORAGE] = $properties;
     return $this;
   }
 
   public function getStorageProperties() {
     return idx($this->metadata, self::METADATA_STORAGE, array());
   }
 
   public function getStorageProperty($key, $default = null) {
     $properties = $this->getStorageProperties();
     return idx($properties, $key, $default);
   }
 
   public function loadDataFromIterator($iterator) {
     $result = '';
 
     foreach ($iterator as $chunk) {
       $result .= $chunk;
     }
 
     return $result;
   }
 
   public function updateDimensions($save = true) {
     if (!$this->isViewableImage()) {
       throw new Exception(pht('This file is not a viewable image.'));
     }
 
     if (!function_exists('imagecreatefromstring')) {
       throw new Exception(pht('Cannot retrieve image information.'));
     }
 
     $data = $this->loadFileData();
 
     $img = imagecreatefromstring($data);
     if ($img === false) {
       throw new Exception(pht('Error when decoding image.'));
     }
 
     $this->metadata[self::METADATA_IMAGE_WIDTH] = imagesx($img);
     $this->metadata[self::METADATA_IMAGE_HEIGHT] = imagesy($img);
 
     if ($save) {
       $this->save();
     }
 
     return $this;
   }
 
   public function copyDimensions(PhabricatorFile $file) {
     $metadata = $file->getMetadata();
     $width = idx($metadata, self::METADATA_IMAGE_WIDTH);
     if ($width) {
       $this->metadata[self::METADATA_IMAGE_WIDTH] = $width;
     }
     $height = idx($metadata, self::METADATA_IMAGE_HEIGHT);
     if ($height) {
       $this->metadata[self::METADATA_IMAGE_HEIGHT] = $height;
     }
 
     return $this;
   }
 
 
   /**
    * Load (or build) the {@class:PhabricatorFile} objects for builtin file
    * resources. The builtin mechanism allows files shipped with Phabricator
    * to be treated like normal files so that APIs do not need to special case
    * things like default images or deleted files.
    *
    * Builtins are located in `resources/builtin/` and identified by their
    * name.
    *
    * @param  PhabricatorUser Viewing user.
    * @param  list<PhabricatorFilesBuiltinFile> List of builtin file specs.
    * @return dict<string, PhabricatorFile> Dictionary of named builtins.
    */
   public static function loadBuiltins(PhabricatorUser $user, array $builtins) {
     $builtins = mpull($builtins, null, 'getBuiltinFileKey');
 
     // NOTE: Anyone is allowed to access builtin files.
 
     $files = id(new PhabricatorFileQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withBuiltinKeys(array_keys($builtins))
       ->execute();
 
     $results = array();
     foreach ($files as $file) {
       $builtin_key = $file->getBuiltinName();
       if ($builtin_key !== null) {
         $results[$builtin_key] = $file;
       }
     }
 
     $build = array();
     foreach ($builtins as $key => $builtin) {
       if (isset($results[$key])) {
         continue;
       }
 
       $data = $builtin->loadBuiltinFileData();
 
       $params = array(
         'name' => $builtin->getBuiltinDisplayName(),
         'ttl.relative' => phutil_units('7 days in seconds'),
         'canCDN' => true,
         'builtin' => $key,
       );
 
       $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
         try {
           $file = self::newFromFileData($data, $params);
         } catch (AphrontDuplicateKeyQueryException $ex) {
           $file = id(new PhabricatorFileQuery())
             ->setViewer(PhabricatorUser::getOmnipotentUser())
             ->withBuiltinKeys(array($key))
             ->executeOne();
           if (!$file) {
             throw new Exception(
               pht(
                 'Collided mid-air when generating builtin file "%s", but '.
                 'then failed to load the object we collided with.',
                 $key));
           }
         }
       unset($unguarded);
 
       $file->attachObjectPHIDs(array());
       $file->attachObjects(array());
 
       $results[$key] = $file;
     }
 
     return $results;
   }
 
 
   /**
    * Convenience wrapper for @{method:loadBuiltins}.
    *
    * @param PhabricatorUser   Viewing user.
    * @param string            Single builtin name to load.
    * @return PhabricatorFile  Corresponding builtin file.
    */
   public static function loadBuiltin(PhabricatorUser $user, $name) {
     $builtin = id(new PhabricatorFilesOnDiskBuiltinFile())
       ->setName($name);
 
     $key = $builtin->getBuiltinFileKey();
 
     return idx(self::loadBuiltins($user, array($builtin)), $key);
   }
 
   public function getObjects() {
     return $this->assertAttached($this->objects);
   }
 
   public function attachObjects(array $objects) {
     $this->objects = $objects;
     return $this;
   }
 
   public function getObjectPHIDs() {
     return $this->assertAttached($this->objectPHIDs);
   }
 
   public function attachObjectPHIDs(array $object_phids) {
     $this->objectPHIDs = $object_phids;
     return $this;
   }
 
   public function getOriginalFile() {
     return $this->assertAttached($this->originalFile);
   }
 
   public function attachOriginalFile(PhabricatorFile $file = null) {
     $this->originalFile = $file;
     return $this;
   }
 
   public function getImageHeight() {
     if (!$this->isViewableImage()) {
       return null;
     }
     return idx($this->metadata, self::METADATA_IMAGE_HEIGHT);
   }
 
   public function getImageWidth() {
     if (!$this->isViewableImage()) {
       return null;
     }
     return idx($this->metadata, self::METADATA_IMAGE_WIDTH);
   }
 
   public function getCanCDN() {
     if (!$this->isViewableImage()) {
       return false;
     }
 
     return idx($this->metadata, self::METADATA_CAN_CDN);
   }
 
   public function setCanCDN($can_cdn) {
     $this->metadata[self::METADATA_CAN_CDN] = $can_cdn ? 1 : 0;
     return $this;
   }
 
   public function isBuiltin() {
     return ($this->getBuiltinName() !== null);
   }
 
   public function getBuiltinName() {
     return idx($this->metadata, self::METADATA_BUILTIN);
   }
 
   public function setBuiltinName($name) {
     $this->metadata[self::METADATA_BUILTIN] = $name;
     return $this;
   }
 
   public function getIsProfileImage() {
     return idx($this->metadata, self::METADATA_PROFILE);
   }
 
   public function setIsProfileImage($value) {
     $this->metadata[self::METADATA_PROFILE] = $value;
     return $this;
   }
 
   /**
    * Write the policy edge between this file and some object.
    *
    * @param phid Object PHID to attach to.
    * @return this
    */
   public function attachToObject($phid) {
     $edge_type = PhabricatorObjectHasFileEdgeType::EDGECONST;
 
     id(new PhabricatorEdgeEditor())
       ->addEdge($phid, $edge_type, $this->getPHID())
       ->save();
 
     return $this;
   }
 
 
   /**
    * Remove the policy edge between this file and some object.
    *
    * @param phid Object PHID to detach from.
    * @return this
    */
   public function detachFromObject($phid) {
     $edge_type = PhabricatorObjectHasFileEdgeType::EDGECONST;
 
     id(new PhabricatorEdgeEditor())
       ->removeEdge($phid, $edge_type, $this->getPHID())
       ->save();
 
     return $this;
   }
 
 
   /**
    * Configure a newly created file object according to specified parameters.
    *
    * This method is called both when creating a file from fresh data, and
    * when creating a new file which reuses existing storage.
    *
    * @param map<string, wild>   Bag of parameters, see @{class:PhabricatorFile}
    *  for documentation.
    * @return this
    */
   private function readPropertiesFromParameters(array $params) {
     PhutilTypeSpec::checkMap(
       $params,
       array(
         'name' => 'optional string',
         'authorPHID' => 'optional string',
         'ttl.relative' => 'optional int',
         'ttl.absolute' => 'optional int',
         'viewPolicy' => 'optional string',
         'isExplicitUpload' => 'optional bool',
         'canCDN' => 'optional bool',
         'profile' => 'optional bool',
         'format' => 'optional string|PhabricatorFileStorageFormat',
         'mime-type' => 'optional string',
         'builtin' => 'optional string',
         'storageEngines' => 'optional list<PhabricatorFileStorageEngine>',
       ));
 
     $file_name = idx($params, 'name');
     $this->setName($file_name);
 
     $author_phid = idx($params, 'authorPHID');
     $this->setAuthorPHID($author_phid);
 
     $absolute_ttl = idx($params, 'ttl.absolute');
     $relative_ttl = idx($params, 'ttl.relative');
     if ($absolute_ttl !== null && $relative_ttl !== null) {
       throw new Exception(
         pht(
           'Specify an absolute TTL or a relative TTL, but not both.'));
     } else if ($absolute_ttl !== null) {
       if ($absolute_ttl < PhabricatorTime::getNow()) {
         throw new Exception(
           pht(
             'Absolute TTL must be in the present or future, but TTL "%s" '.
             'is in the past.',
             $absolute_ttl));
       }
 
       $this->setTtl($absolute_ttl);
     } else if ($relative_ttl !== null) {
       if ($relative_ttl < 0) {
         throw new Exception(
           pht(
             'Relative TTL must be zero or more seconds, but "%s" is '.
             'negative.',
             $relative_ttl));
       }
 
       $max_relative = phutil_units('365 days in seconds');
       if ($relative_ttl > $max_relative) {
         throw new Exception(
           pht(
             'Relative TTL must not be more than "%s" seconds, but TTL '.
             '"%s" was specified.',
             $max_relative,
             $relative_ttl));
       }
 
       $absolute_ttl = PhabricatorTime::getNow() + $relative_ttl;
 
       $this->setTtl($absolute_ttl);
     }
 
     $view_policy = idx($params, 'viewPolicy');
     if ($view_policy) {
       $this->setViewPolicy($params['viewPolicy']);
     }
 
     $is_explicit = (idx($params, 'isExplicitUpload') ? 1 : 0);
     $this->setIsExplicitUpload($is_explicit);
 
     $can_cdn = idx($params, 'canCDN');
     if ($can_cdn) {
       $this->setCanCDN(true);
     }
 
     $builtin = idx($params, 'builtin');
     if ($builtin) {
       $this->setBuiltinName($builtin);
       $this->setBuiltinKey($builtin);
     }
 
     $profile = idx($params, 'profile');
     if ($profile) {
       $this->setIsProfileImage(true);
     }
 
     $mime_type = idx($params, 'mime-type');
     if ($mime_type) {
       $this->setMimeType($mime_type);
     }
 
     return $this;
   }
 
   public function getRedirectResponse() {
     $uri = $this->getBestURI();
 
     // TODO: This is a bit iffy. Sometimes, getBestURI() returns a CDN URI
     // (if the file is a viewable image) and sometimes a local URI (if not).
     // For now, just detect which one we got and configure the response
     // appropriately. In the long run, if this endpoint is served from a CDN
     // domain, we can't issue a local redirect to an info URI (which is not
     // present on the CDN domain). We probably never actually issue local
     // redirects here anyway, since we only ever transform viewable images
     // right now.
 
     $is_external = strlen(id(new PhutilURI($uri))->getDomain());
 
     return id(new AphrontRedirectResponse())
       ->setIsExternal($is_external)
       ->setURI($uri);
   }
 
   public function attachTransforms(array $map) {
     $this->transforms = $map;
     return $this;
   }
 
   public function getTransform($key) {
     return $this->assertAttachedKey($this->transforms, $key);
   }
 
 
 /* -(  PhabricatorApplicationTransactionInterface  )------------------------- */
 
 
   public function getApplicationTransactionEditor() {
     return new PhabricatorFileEditor();
   }
 
   public function getApplicationTransactionObject() {
     return $this;
   }
 
   public function getApplicationTransactionTemplate() {
     return new PhabricatorFileTransaction();
   }
 
   public function willRenderTimeline(
     PhabricatorApplicationTransactionView $timeline,
     AphrontRequest $request) {
 
     return $timeline;
   }
 
 
 /* -(  PhabricatorPolicyInterface Implementation  )-------------------------- */
 
 
   public function getCapabilities() {
     return array(
       PhabricatorPolicyCapability::CAN_VIEW,
       PhabricatorPolicyCapability::CAN_EDIT,
     );
   }
 
   public function getPolicy($capability) {
     switch ($capability) {
       case PhabricatorPolicyCapability::CAN_VIEW:
         if ($this->isBuiltin()) {
           return PhabricatorPolicies::getMostOpenPolicy();
         }
         if ($this->getIsProfileImage()) {
           return PhabricatorPolicies::getMostOpenPolicy();
         }
         return $this->getViewPolicy();
       case PhabricatorPolicyCapability::CAN_EDIT:
         return PhabricatorPolicies::POLICY_NOONE;
     }
   }
 
   public function hasAutomaticCapability($capability, PhabricatorUser $viewer) {
     $viewer_phid = $viewer->getPHID();
     if ($viewer_phid) {
       if ($this->getAuthorPHID() == $viewer_phid) {
         return true;
       }
     }
 
     switch ($capability) {
       case PhabricatorPolicyCapability::CAN_VIEW:
         // If you can see the file this file is a transform of, you can see
         // this file.
         if ($this->getOriginalFile()) {
           return true;
         }
 
         // If you can see any object this file is attached to, you can see
         // the file.
         return (count($this->getObjects()) > 0);
     }
 
     return false;
   }
 
   public function describeAutomaticCapability($capability) {
     $out = array();
     $out[] = pht('The user who uploaded a file can always view and edit it.');
     switch ($capability) {
       case PhabricatorPolicyCapability::CAN_VIEW:
         $out[] = pht(
           'Files attached to objects are visible to users who can view '.
           'those objects.');
         $out[] = pht(
           'Thumbnails are visible only to users who can view the original '.
           'file.');
         break;
     }
 
     return $out;
   }
 
 
 /* -(  PhabricatorSubscribableInterface Implementation  )-------------------- */
 
 
   public function isAutomaticallySubscribed($phid) {
     return ($this->authorPHID == $phid);
   }
 
 
 /* -(  PhabricatorTokenReceiverInterface  )---------------------------------- */
 
 
   public function getUsersToNotifyOfTokenGiven() {
     return array(
       $this->getAuthorPHID(),
     );
   }
 
 
 /* -(  PhabricatorDestructibleInterface  )----------------------------------- */
 
 
   public function destroyObjectPermanently(
     PhabricatorDestructionEngine $engine) {
 
     $this->openTransaction();
       $this->delete();
     $this->saveTransaction();
   }
 
 
 /* -(  PhabricatorConduitResultInterface  )---------------------------------- */
 
 
   public function getFieldSpecificationsForConduit() {
     return array(
       id(new PhabricatorConduitSearchFieldSpecification())
         ->setKey('name')
         ->setType('string')
         ->setDescription(pht('The name of the file.')),
       id(new PhabricatorConduitSearchFieldSpecification())
         ->setKey('dataURI')
         ->setType('string')
         ->setDescription(pht('Download URI for the file data.')),
       id(new PhabricatorConduitSearchFieldSpecification())
         ->setKey('size')
         ->setType('int')
         ->setDescription(pht('File size, in bytes.')),
     );
   }
 
   public function getFieldValuesForConduit() {
     return array(
       'name' => $this->getName(),
       'dataURI' => $this->getCDNURI(),
       'size' => (int)$this->getByteSize(),
     );
   }
 
   public function getConduitSearchAttachments() {
     return array();
   }
 
 }
diff --git a/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php b/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php
index 5b64c9b1ac..936676b902 100644
--- a/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php
+++ b/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php
@@ -1,490 +1,495 @@
 <?php
 
 final class PhabricatorFileTestCase extends PhabricatorTestCase {
 
   protected function getPhabricatorTestCaseConfiguration() {
     return array(
       self::PHABRICATOR_TESTCONFIG_BUILD_STORAGE_FIXTURES => true,
     );
   }
 
   public function testFileDirectScramble() {
     // Changes to a file's view policy should scramble the file secret.
 
     $engine = new PhabricatorTestStorageEngine();
     $data = Filesystem::readRandomCharacters(64);
 
     $author = $this->generateNewTestUser();
 
     $params = array(
       'name' => 'test.dat',
       'viewPolicy' => PhabricatorPolicies::POLICY_USER,
       'authorPHID' => $author->getPHID(),
       'storageEngines' => array(
         $engine,
       ),
     );
 
     $file = PhabricatorFile::newFromFileData($data, $params);
 
     $secret1 = $file->getSecretKey();
 
     // First, change the name: this should not scramble the secret.
     $xactions = array();
     $xactions[] = id(new PhabricatorFileTransaction())
       ->setTransactionType(PhabricatorFileNameTransaction::TRANSACTIONTYPE)
       ->setNewValue('test.dat2');
 
     $engine = id(new PhabricatorFileEditor())
       ->setActor($author)
       ->setContentSource($this->newContentSource())
       ->applyTransactions($file, $xactions);
 
     $file = $file->reload();
 
     $secret2 = $file->getSecretKey();
 
     $this->assertEqual(
       $secret1,
       $secret2,
       pht('No secret scramble on non-policy edit.'));
 
     // Now, change the view policy. This should scramble the secret.
     $xactions = array();
     $xactions[] = id(new PhabricatorFileTransaction())
       ->setTransactionType(PhabricatorTransactions::TYPE_VIEW_POLICY)
       ->setNewValue($author->getPHID());
 
     $engine = id(new PhabricatorFileEditor())
       ->setActor($author)
       ->setContentSource($this->newContentSource())
       ->applyTransactions($file, $xactions);
 
     $file = $file->reload();
     $secret3 = $file->getSecretKey();
 
     $this->assertTrue(
       ($secret1 !== $secret3),
       pht('Changing file view policy should scramble secret.'));
   }
 
   public function testFileIndirectScramble() {
     // When a file is attached to an object like a task and the task view
     // policy changes, the file secret should be scrambled. This invalidates
     // old URIs if tasks get locked down.
 
     $engine = new PhabricatorTestStorageEngine();
     $data = Filesystem::readRandomCharacters(64);
 
     $author = $this->generateNewTestUser();
 
     $params = array(
       'name' => 'test.dat',
       'viewPolicy' => $author->getPHID(),
       'authorPHID' => $author->getPHID(),
       'storageEngines' => array(
         $engine,
       ),
     );
 
     $file = PhabricatorFile::newFromFileData($data, $params);
     $secret1 = $file->getSecretKey();
 
     $task = ManiphestTask::initializeNewTask($author);
 
     $xactions = array();
     $xactions[] = id(new ManiphestTransaction())
       ->setTransactionType(ManiphestTransaction::TYPE_TITLE)
       ->setNewValue(pht('File Scramble Test Task'));
 
     $xactions[] = id(new ManiphestTransaction())
       ->setTransactionType(ManiphestTransaction::TYPE_DESCRIPTION)
       ->setNewValue('{'.$file->getMonogram().'}');
 
     id(new ManiphestTransactionEditor())
       ->setActor($author)
       ->setContentSource($this->newContentSource())
       ->applyTransactions($task, $xactions);
 
     $file = $file->reload();
     $secret2 = $file->getSecretKey();
 
     $this->assertEqual(
       $secret1,
       $secret2,
       pht(
         'File policy should not scramble when attached to '.
         'newly created object.'));
 
     $xactions = array();
     $xactions[] = id(new ManiphestTransaction())
       ->setTransactionType(PhabricatorTransactions::TYPE_VIEW_POLICY)
       ->setNewValue($author->getPHID());
 
     id(new ManiphestTransactionEditor())
       ->setActor($author)
       ->setContentSource($this->newContentSource())
       ->applyTransactions($task, $xactions);
 
     $file = $file->reload();
     $secret3 = $file->getSecretKey();
 
     $this->assertTrue(
       ($secret1 !== $secret3),
       pht('Changing attached object view policy should scramble secret.'));
   }
 
 
   public function testFileVisibility() {
     $engine = new PhabricatorTestStorageEngine();
     $data = Filesystem::readRandomCharacters(64);
 
     $author = $this->generateNewTestUser();
     $viewer = $this->generateNewTestUser();
     $users = array($author, $viewer);
 
     $params = array(
       'name' => 'test.dat',
       'viewPolicy' => PhabricatorPolicies::POLICY_NOONE,
       'authorPHID' => $author->getPHID(),
       'storageEngines' => array(
         $engine,
       ),
     );
 
     $file = PhabricatorFile::newFromFileData($data, $params);
     $filter = new PhabricatorPolicyFilter();
 
     // Test bare file policies.
     $this->assertEqual(
       array(
         true,
         false,
       ),
       $this->canViewFile($users, $file),
       pht('File Visibility'));
 
     // Create an object and test object policies.
 
     $object = ManiphestTask::initializeNewTask($author);
     $object->setViewPolicy(PhabricatorPolicies::getMostOpenPolicy());
     $object->save();
 
     $this->assertTrue(
       $filter->hasCapability(
         $author,
         $object,
         PhabricatorPolicyCapability::CAN_VIEW),
       pht('Object Visible to Author'));
 
     $this->assertTrue(
       $filter->hasCapability(
         $viewer,
         $object,
         PhabricatorPolicyCapability::CAN_VIEW),
       pht('Object Visible to Others'));
 
     // Attach the file to the object and test that the association opens a
     // policy exception for the non-author viewer.
 
     $file->attachToObject($object->getPHID());
 
     // Test the attached file's visibility.
     $this->assertEqual(
       array(
         true,
         true,
       ),
       $this->canViewFile($users, $file),
       pht('Attached File Visibility'));
 
     // Create a "thumbnail" of the original file.
     $params = array(
       'name' => 'test.thumb.dat',
       'viewPolicy' => PhabricatorPolicies::POLICY_NOONE,
       'storageEngines' => array(
         $engine,
       ),
     );
 
     $xform = PhabricatorFile::newFromFileData($data, $params);
 
     id(new PhabricatorTransformedFile())
       ->setOriginalPHID($file->getPHID())
       ->setTransform('test-thumb')
       ->setTransformedPHID($xform->getPHID())
       ->save();
 
     // Test the thumbnail's visibility.
     $this->assertEqual(
       array(
         true,
         true,
       ),
       $this->canViewFile($users, $xform),
       pht('Attached Thumbnail Visibility'));
 
     // Detach the object and make sure it affects the thumbnail.
     $file->detachFromObject($object->getPHID());
 
     // Test the detached thumbnail's visibility.
     $this->assertEqual(
       array(
         true,
         false,
       ),
       $this->canViewFile($users, $xform),
       pht('Detached Thumbnail Visibility'));
   }
 
   private function canViewFile(array $users, PhabricatorFile $file) {
     $results = array();
     foreach ($users as $user) {
       $results[] = (bool)id(new PhabricatorFileQuery())
         ->setViewer($user)
         ->withPHIDs(array($file->getPHID()))
         ->execute();
     }
     return $results;
   }
 
   public function testFileStorageReadWrite() {
     $engine = new PhabricatorTestStorageEngine();
 
     $data = Filesystem::readRandomCharacters(64);
 
     $params = array(
       'name' => 'test.dat',
       'storageEngines' => array(
         $engine,
       ),
     );
 
     $file = PhabricatorFile::newFromFileData($data, $params);
 
     // Test that the storage engine worked, and was the target of the write. We
     // don't actually care what the data is (future changes may compress or
     // encrypt it), just that it exists in the test storage engine.
     $engine->readFile($file->getStorageHandle());
 
     // Now test that we get the same data back out.
     $this->assertEqual($data, $file->loadFileData());
   }
 
   public function testFileStorageUploadDifferentFiles() {
     $engine = new PhabricatorTestStorageEngine();
 
     $data = Filesystem::readRandomCharacters(64);
     $other_data = Filesystem::readRandomCharacters(64);
 
     $params = array(
       'name' => 'test.dat',
       'storageEngines' => array(
         $engine,
       ),
     );
 
     $first_file = PhabricatorFile::newFromFileData($data, $params);
 
     $second_file = PhabricatorFile::newFromFileData($other_data, $params);
 
     // Test that the second file uses  different storage handle from
     // the first file.
     $first_handle = $first_file->getStorageHandle();
     $second_handle = $second_file->getStorageHandle();
 
     $this->assertTrue($first_handle != $second_handle);
   }
 
   public function testFileStorageUploadSameFile() {
     $engine = new PhabricatorTestStorageEngine();
 
     $data = Filesystem::readRandomCharacters(64);
 
+    $hash = PhabricatorFile::hashFileContent($data);
+    if ($hash === null) {
+      $this->assertSkipped(pht('File content hashing is not available.'));
+    }
+
     $params = array(
       'name' => 'test.dat',
       'storageEngines' => array(
         $engine,
       ),
     );
 
     $first_file = PhabricatorFile::newFromFileData($data, $params);
 
     $second_file = PhabricatorFile::newFromFileData($data, $params);
 
     // Test that the second file uses the same storage handle as
     // the first file.
     $handle = $first_file->getStorageHandle();
     $second_handle = $second_file->getStorageHandle();
 
     $this->assertEqual($handle, $second_handle);
   }
 
   public function testFileStorageDelete() {
     $engine = new PhabricatorTestStorageEngine();
 
     $data = Filesystem::readRandomCharacters(64);
 
     $params = array(
       'name' => 'test.dat',
       'storageEngines' => array(
         $engine,
       ),
     );
 
     $file = PhabricatorFile::newFromFileData($data, $params);
     $handle = $file->getStorageHandle();
     $file->delete();
 
     $caught = null;
     try {
       $engine->readFile($handle);
     } catch (Exception $ex) {
       $caught = $ex;
     }
 
     $this->assertTrue($caught instanceof Exception);
   }
 
   public function testFileStorageDeleteSharedHandle() {
     $engine = new PhabricatorTestStorageEngine();
 
     $data = Filesystem::readRandomCharacters(64);
 
     $params = array(
       'name' => 'test.dat',
       'storageEngines' => array(
         $engine,
       ),
     );
 
     $first_file = PhabricatorFile::newFromFileData($data, $params);
     $second_file = PhabricatorFile::newFromFileData($data, $params);
     $first_file->delete();
 
     $this->assertEqual($data, $second_file->loadFileData());
   }
 
   public function testReadWriteTtlFiles() {
     $engine = new PhabricatorTestStorageEngine();
 
     $data = Filesystem::readRandomCharacters(64);
 
     $ttl = (PhabricatorTime::getNow() + phutil_units('24 hours in seconds'));
 
     $params = array(
       'name' => 'test.dat',
       'ttl.absolute' => $ttl,
       'storageEngines' => array(
         $engine,
       ),
     );
 
     $file = PhabricatorFile::newFromFileData($data, $params);
     $this->assertEqual($ttl, $file->getTTL());
   }
 
   public function testFileTransformDelete() {
     // We want to test that a file deletes all its inbound transformation
     // records and outbound transformed derivatives when it is deleted.
 
     // First, we create a chain of transforms, A -> B -> C.
 
     $engine = new PhabricatorTestStorageEngine();
 
     $params = array(
       'name' => 'test.txt',
       'storageEngines' => array(
         $engine,
       ),
     );
 
     $a = PhabricatorFile::newFromFileData('a', $params);
     $b = PhabricatorFile::newFromFileData('b', $params);
     $c = PhabricatorFile::newFromFileData('c', $params);
 
     id(new PhabricatorTransformedFile())
       ->setOriginalPHID($a->getPHID())
       ->setTransform('test:a->b')
       ->setTransformedPHID($b->getPHID())
       ->save();
 
     id(new PhabricatorTransformedFile())
       ->setOriginalPHID($b->getPHID())
       ->setTransform('test:b->c')
       ->setTransformedPHID($c->getPHID())
       ->save();
 
     // Now, verify that A -> B and B -> C exist.
 
     $xform_a = id(new PhabricatorFileQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withTransforms(
         array(
           array(
             'originalPHID' => $a->getPHID(),
             'transform'    => true,
           ),
         ))
       ->execute();
 
     $this->assertEqual(1, count($xform_a));
     $this->assertEqual($b->getPHID(), head($xform_a)->getPHID());
 
     $xform_b = id(new PhabricatorFileQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withTransforms(
         array(
           array(
             'originalPHID' => $b->getPHID(),
             'transform'    => true,
           ),
         ))
       ->execute();
 
     $this->assertEqual(1, count($xform_b));
     $this->assertEqual($c->getPHID(), head($xform_b)->getPHID());
 
     // Delete "B".
 
     $b->delete();
 
     // Now, verify that the A -> B and B -> C links are gone.
 
     $xform_a = id(new PhabricatorFileQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withTransforms(
         array(
           array(
             'originalPHID' => $a->getPHID(),
             'transform'    => true,
           ),
         ))
       ->execute();
 
     $this->assertEqual(0, count($xform_a));
 
     $xform_b = id(new PhabricatorFileQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withTransforms(
         array(
           array(
             'originalPHID' => $b->getPHID(),
             'transform'    => true,
           ),
         ))
       ->execute();
 
     $this->assertEqual(0, count($xform_b));
 
     // Also verify that C has been deleted.
 
     $alternate_c = id(new PhabricatorFileQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withPHIDs(array($c->getPHID()))
       ->execute();
 
     $this->assertEqual(array(), $alternate_c);
   }
 
 }