Merge pull request #14383 from jknockaert/newbranch
make encryption stream wrapper seekable
This commit is contained in:
Clark Tomlinson
commit
0e4ba618cf
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@ -64,15 +64,17 @@ class Stream {
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private $keyId;
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private $handle; // Resource returned by fopen
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private $meta = array(); // Header / meta for source stream
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private $writeCache;
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private $cache; // Current block unencrypted
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private $position; // Current pointer position in the unencrypted stream
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private $writeFlag; // Flag to write current block when leaving it
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private $size;
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private $headerSize = 0; // Size of header
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private $unencryptedSize;
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private $publicKey;
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private $encKeyfile;
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private $newFile; // helper var, we only need to write the keyfile for new files
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private $isLocalTmpFile = false; // do we operate on a local tmp file
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private $localTmpFile; // path of local tmp file
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private $headerWritten = false;
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private $containHeader = false; // the file contain a header
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private $cipher; // cipher used for encryption/decryption
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/** @var \OCA\Files_Encryption\Util */
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@ -158,6 +160,17 @@ class Stream {
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$proxyStatus = \OC_FileProxy::$enabled;
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\OC_FileProxy::$enabled = false;
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$this->position = 0;
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$this->cache = '';
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$this->writeFlag = 0;
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// Setting handle so it can be used for reading the header
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if ($this->isLocalTmpFile) {
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$this->handle = fopen($this->localTmpFile, $mode);
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} else {
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$this->handle = $this->rootView->fopen($this->rawPath, $mode);
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}
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if (
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$mode === 'w'
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or $mode === 'w+'
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@ -169,15 +182,12 @@ class Stream {
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$this->unencryptedSize = 0;
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} else {
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$this->size = $this->rootView->filesize($this->rawPath);
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\OC_FileProxy::$enabled = true;
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$this->unencryptedSize = $this->rootView->filesize($this->rawPath);
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\OC_FileProxy::$enabled = false;
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$this->readHeader();
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}
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if ($this->isLocalTmpFile) {
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$this->handle = fopen($this->localTmpFile, $mode);
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} else {
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$this->handle = $this->rootView->fopen($this->rawPath, $mode);
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}
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\OC_FileProxy::$enabled = $proxyStatus;
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if (!is_resource($this->handle)) {
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@ -200,14 +210,8 @@ class Stream {
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private function readHeader() {
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if ($this->isLocalTmpFile) {
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$handle = fopen($this->localTmpFile, 'r');
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} else {
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$handle = $this->rootView->fopen($this->rawPath, 'r');
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}
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if (is_resource($handle)) {
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$data = fread($handle, Crypt::BLOCKSIZE);
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if (is_resource($this->handle)) {
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$data = fread($this->handle, Crypt::BLOCKSIZE);
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$header = Crypt::parseHeader($data);
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$this->cipher = Crypt::getCipher($header);
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@ -215,9 +219,16 @@ class Stream {
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// remeber that we found a header
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if (!empty($header)) {
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$this->containHeader = true;
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$this->headerSize = Crypt::BLOCKSIZE;
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// if there's no header then decrypt the block and store it in the cache
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} else {
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if (!$this->getKey()) {
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throw new \Exception('Encryption key not found for "' . $this->rawPath . '" during attempted read via stream');
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} else {
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$this->cache = Crypt::symmetricDecryptFileContent($data, $this->plainKey, $this->cipher);
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}
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}
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fclose($handle);
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}
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}
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@ -226,7 +237,7 @@ class Stream {
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* @return int position of the file pointer
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*/
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public function stream_tell() {
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return ftell($this->handle);
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return $this->position;
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}
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/**
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@ -234,18 +245,41 @@ class Stream {
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* @param int $whence
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* @return bool true if fseek was successful, otherwise false
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*/
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// seeking the stream tries to move the pointer on the encrypted stream to the beginning of the target block
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// if that works, it flushes the current block and changes the position in the unencrypted stream
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public function stream_seek($offset, $whence = SEEK_SET) {
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$this->flush();
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// ignore the header and just overstep it
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if ($this->containHeader) {
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$offset += Crypt::BLOCKSIZE;
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}
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// this wrapper needs to return "true" for success.
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// the fseek call itself returns 0 on succeess
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return !fseek($this->handle, $offset, $whence);
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$return=false;
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switch($whence) {
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case SEEK_SET:
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if($offset < $this->unencryptedSize && $offset >= 0) {
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$newPosition=$offset;
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}
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break;
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case SEEK_CUR:
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if($offset>=0) {
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$newPosition=$offset+$this->position;
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}
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break;
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case SEEK_END:
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if($this->unencryptedSize + $offset >= 0) {
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$newPosition=$this->unencryptedSize+$offset;
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}
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break;
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default:
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return $return;
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}
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$newFilePosition=floor($newPosition/6126)*Crypt::BLOCKSIZE+$this->headerSize;
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if (fseek($this->handle, $newFilePosition)===0) {
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$this->flush();
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$this->position=$newPosition;
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$return=true;
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}
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return $return;
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}
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@ -256,35 +290,33 @@ class Stream {
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*/
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public function stream_read($count) {
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$this->writeCache = '';
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$result = '';
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if ($count !== Crypt::BLOCKSIZE) {
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\OCP\Util::writeLog('Encryption library', 'PHP "bug" 21641 no longer holds, decryption system requires refactoring', \OCP\Util::FATAL);
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throw new EncryptionException('expected a block size of 8192 byte', EncryptionException::UNEXPECTED_BLOCK_SIZE);
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}
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// limit to the end of the unencrypted file; otherwise getFileSize will fail and it is good practise anyway
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$count=min($count,$this->unencryptedSize - $this->position);
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// Get the data from the file handle
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$data = fread($this->handle, $count);
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// loop over the 6126 sized unencrypted blocks
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while ($count > 0) {
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// if this block contained the header we move on to the next block
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if (Crypt::isHeader($data)) {
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$data = fread($this->handle, $count);
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}
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$remainingLength = $count;
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$result = null;
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if (strlen($data)) {
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if (!$this->getKey()) {
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// Error! We don't have a key to decrypt the file with
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throw new \Exception(
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'Encryption key not found for "' . $this->rawPath . '" during attempted read via stream');
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// update the cache of the current block
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$this->readCache();
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// determine the relative position in the current block
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$blockPosition=($this->position % 6126);
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// if entire read inside current block then only position needs to be updated
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if ($remainingLength<(6126 - $blockPosition)) {
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$result .= substr($this->cache,$blockPosition,$remainingLength);
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$this->position += $remainingLength;
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$count=0;
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// otherwise remainder of current block is fetched, the block is flushed and the position updated
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} else {
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// Decrypt data
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$result = Crypt::symmetricDecryptFileContent($data, $this->plainKey, $this->cipher);
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$result .= substr($this->cache,$blockPosition);
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$this->flush();
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$this->position += (6126 - $blockPosition);
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$count -= (6126 - $blockPosition);
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}
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}
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@ -328,16 +360,14 @@ class Stream {
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}
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$util = new Util($this->rootView, $this->userId);
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// Fetch and decrypt keyfile
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// Fetch existing keyfile
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$this->encKeyfile = Keymanager::getFileKey($this->rootView, $util, $this->relPath);
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$this->encKeyfile = Keymanager::getFileKey($this->rootView, $this->util, $this->relPath);
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// If a keyfile already exists
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if ($this->encKeyfile) {
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$shareKey = Keymanager::getShareKey($this->rootView, $this->keyId, $util, $this->relPath);
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$shareKey = Keymanager::getShareKey($this->rootView, $this->keyId, $this->util, $this->relPath);
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// if there is no valid private key return false
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if ($this->privateKey === false) {
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@ -383,6 +413,9 @@ class Stream {
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fwrite($this->handle, $paddedHeader);
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$this->headerWritten = true;
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$this->containHeader = true;
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$this->headerSize = Crypt::BLOCKSIZE;
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$this->size += $this->headerSize;
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}
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/**
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@ -390,7 +423,7 @@ class Stream {
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* @param string $data data to be written to disk
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* @note the data will be written to the path stored in the stream handle, set in stream_open()
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* @note $data is only ever be a maximum of 8192 bytes long. This is set by PHP internally. stream_write() is called multiple times in a loop on data larger than 8192 bytes
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* @note Because the encryption process used increases the length of $data, a writeCache is used to carry over data which would not fit in the required block size
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* @note Because the encryption process used increases the length of $data, a cache is used to carry over data which would not fit in the required block size
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* @note Padding is added to each encrypted block to ensure that the resulting block is exactly 8192 bytes. This is removed during stream_read
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* @note PHP automatically updates the file pointer after writing data to reflect it's length. There is generally no need to update the poitner manually using fseek
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*/
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@ -402,24 +435,10 @@ class Stream {
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return strlen($data);
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}
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if ($this->headerWritten === false) {
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if ($this->size === 0) {
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$this->writeHeader();
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}
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// Disable the file proxies so that encryption is not
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// automatically attempted when the file is written to disk -
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// we are handling that separately here and we don't want to
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// get into an infinite loop
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$proxyStatus = \OC_FileProxy::$enabled;
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\OC_FileProxy::$enabled = false;
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// Get the length of the unencrypted data that we are handling
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$length = strlen($data);
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// Find out where we are up to in the writing of data to the
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// file
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$pointer = ftell($this->handle);
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// Get / generate the keyfile for the file we're handling
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// If we're writing a new file (not overwriting an existing
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// one), save the newly generated keyfile
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@ -429,68 +448,51 @@ class Stream {
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}
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// If extra data is left over from the last round, make sure it
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// is integrated into the next 6126 / 8192 block
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if ($this->writeCache) {
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$length=0;
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// Concat writeCache to start of $data
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$data = $this->writeCache . $data;
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// Clear the write cache, ready for reuse - it has been
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// flushed and its old contents processed
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$this->writeCache = '';
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}
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// While there still remains some data to be processed & written
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// loop over $data to fit it in 6126 sized unencrypted blocks
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while (strlen($data) > 0) {
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// Remaining length for this iteration, not of the
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// entire file (may be greater than 8192 bytes)
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$remainingLength = strlen($data);
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// If data remaining to be written is less than the
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// size of 1 6126 byte block
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if ($remainingLength < 6126) {
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// set the cache to the current 6126 block
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$this->readCache();
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// Set writeCache to contents of $data
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// The writeCache will be carried over to the
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// next write round, and added to the start of
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// $data to ensure that written blocks are
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// always the correct length. If there is still
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// data in writeCache after the writing round
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// has finished, then the data will be written
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// to disk by $this->flush().
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$this->writeCache = $data;
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// only allow writes on seekable streams, or at the end of the encrypted stream
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// for seekable streams the pointer is moved back to the beginning of the encrypted block
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// flush will start writing there when the position moves to another block
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if((fseek($this->handle, floor($this->position/6126)*Crypt::BLOCKSIZE + $this->headerSize) === 0) || (floor($this->position/6126)*Crypt::BLOCKSIZE + $this->headerSize === $this->size)) {
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// Clear $data ready for next round
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$data = '';
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// switch the writeFlag so flush() will write the block
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$this->writeFlag=1;
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// determine the relative position in the current block
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$blockPosition=($this->position % 6126);
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// check if $data fits in current block
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// if so, overwrite existing data (if any)
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// update position and liberate $data
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if ($remainingLength<(6126 - $blockPosition)) {
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$this->cache=substr($this->cache,0,$blockPosition).$data.substr($this->cache,$blockPosition+$remainingLength);
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$this->position += $remainingLength;
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$length += $remainingLength;
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$data = '';
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// if $data doens't fit the current block, the fill the current block and reiterate
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// after the block is filled, it is flushed and $data is updated
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} else {
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$this->cache=substr($this->cache,0,$blockPosition).substr($data,0,6126-$blockPosition);
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$this->flush();
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$this->position += (6126 - $blockPosition);
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$length += (6126 - $blockPosition);
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$data = substr($data, 6126 - $blockPosition);
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}
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} else {
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// Read the chunk from the start of $data
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$chunk = substr($data, 0, 6126);
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$encrypted = $this->preWriteEncrypt($chunk, $this->plainKey);
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// Write the data chunk to disk. This will be
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// attended to the last data chunk if the file
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// being handled totals more than 6126 bytes
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fwrite($this->handle, $encrypted);
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// Remove the chunk we just processed from
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// $data, leaving only unprocessed data in $data
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// var, for handling on the next round
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$data = substr($data, 6126);
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$data='';
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}
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}
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$this->size = max($this->size, $pointer + $length);
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$this->unencryptedSize += $length;
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\OC_FileProxy::$enabled = $proxyStatus;
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$this->unencryptedSize = max($this->unencryptedSize,$this->position);
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return $length;
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@ -537,6 +539,7 @@ class Stream {
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*/
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public function stream_flush() {
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$this->flush();
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return fflush($this->handle);
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// Not a typo: http://php.net/manual/en/function.fflush.php
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@ -546,21 +549,48 @@ class Stream {
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* @return bool
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*/
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public function stream_eof() {
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return feof($this->handle);
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return ($this->position>=$this->unencryptedSize);
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}
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private function flush() {
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if ($this->writeCache) {
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// write to disk only when writeFlag was set to 1
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if ($this->writeFlag === 1) {
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// Disable the file proxies so that encryption is not
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// automatically attempted when the file is written to disk -
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// we are handling that separately here and we don't want to
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// get into an infinite loop
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$proxyStatus = \OC_FileProxy::$enabled;
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\OC_FileProxy::$enabled = false;
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// Set keyfile property for file in question
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$this->getKey();
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$encrypted = $this->preWriteEncrypt($this->writeCache, $this->plainKey);
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$encrypted = $this->preWriteEncrypt($this->cache, $this->plainKey);
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fwrite($this->handle, $encrypted);
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$this->writeFlag = 0;
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$this->size = max($this->size,ftell($this->handle));
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\OC_FileProxy::$enabled = $proxyStatus;
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}
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// always empty the cache (otherwise readCache() will not fill it with the new block)
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$this->cache = '';
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}
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$this->writeCache = '';
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private function readCache() {
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// cache should always be empty string when this function is called
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// don't try to fill the cache when trying to write at the end of the unencrypted file when it coincides with new block
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if ($this->cache === '' && !($this->position===$this->unencryptedSize && ($this->position % 6126)===0)) {
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// Get the data from the file handle
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$data = fread($this->handle, Crypt::BLOCKSIZE);
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$result = '';
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if (strlen($data)) {
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if (!$this->getKey()) {
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// Error! We don't have a key to decrypt the file with
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throw new \Exception('Encryption key not found for "'. $this->rawPath . '" during attempted read via stream');
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} else {
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// Decrypt data
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$result = Crypt::symmetricDecryptFileContent($data, $this->plainKey, $this->cipher);
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}
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}
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$this->cache = $result;
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}
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}
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@ -581,7 +611,7 @@ class Stream {
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$proxyStatus = \OC_FileProxy::$enabled;
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\OC_FileProxy::$enabled = false;
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if ($this->rootView->file_exists($this->rawPath) && $this->size === 0) {
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if ($this->rootView->file_exists($this->rawPath) && $this->size === $this->headerSize) {
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fclose($this->handle);
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$this->rootView->unlink($this->rawPath);
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}
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@ -598,7 +628,7 @@ class Stream {
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$this->meta['mode'] !== 'r' &&
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$this->meta['mode'] !== 'rb' &&
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$this->isLocalTmpFile === false &&
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$this->size > 0 &&
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$this->size > $this->headerSize &&
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$this->unencryptedSize > 0
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) {
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