Commit 0e4ba618 authored by Clark Tomlinson's avatar Clark Tomlinson
Browse files

Merge pull request #14383 from jknockaert/newbranch

make encryption stream wrapper seekable
parents 98e770b6 755d52d0
......@@ -64,15 +64,17 @@ class Stream {
private $keyId;
private $handle; // Resource returned by fopen
private $meta = array(); // Header / meta for source stream
private $writeCache;
private $cache; // Current block unencrypted
private $position; // Current pointer position in the unencrypted stream
private $writeFlag; // Flag to write current block when leaving it
private $size;
private $headerSize = 0; // Size of header
private $unencryptedSize;
private $publicKey;
private $encKeyfile;
private $newFile; // helper var, we only need to write the keyfile for new files
private $isLocalTmpFile = false; // do we operate on a local tmp file
private $localTmpFile; // path of local tmp file
private $headerWritten = false;
private $containHeader = false; // the file contain a header
private $cipher; // cipher used for encryption/decryption
/** @var \OCA\Files_Encryption\Util */
......@@ -158,6 +160,17 @@ class Stream {
$proxyStatus = \OC_FileProxy::$enabled;
\OC_FileProxy::$enabled = false;
$this->position = 0;
$this->cache = '';
$this->writeFlag = 0;
// Setting handle so it can be used for reading the header
if ($this->isLocalTmpFile) {
$this->handle = fopen($this->localTmpFile, $mode);
} else {
$this->handle = $this->rootView->fopen($this->rawPath, $mode);
}
if (
$mode === 'w'
or $mode === 'w+'
......@@ -169,15 +182,12 @@ class Stream {
$this->unencryptedSize = 0;
} else {
$this->size = $this->rootView->filesize($this->rawPath);
\OC_FileProxy::$enabled = true;
$this->unencryptedSize = $this->rootView->filesize($this->rawPath);
\OC_FileProxy::$enabled = false;
$this->readHeader();
}
if ($this->isLocalTmpFile) {
$this->handle = fopen($this->localTmpFile, $mode);
} else {
$this->handle = $this->rootView->fopen($this->rawPath, $mode);
}
\OC_FileProxy::$enabled = $proxyStatus;
if (!is_resource($this->handle)) {
......@@ -200,14 +210,8 @@ class Stream {
private function readHeader() {
if ($this->isLocalTmpFile) {
$handle = fopen($this->localTmpFile, 'r');
} else {
$handle = $this->rootView->fopen($this->rawPath, 'r');
}
if (is_resource($handle)) {
$data = fread($handle, Crypt::BLOCKSIZE);
if (is_resource($this->handle)) {
$data = fread($this->handle, Crypt::BLOCKSIZE);
$header = Crypt::parseHeader($data);
$this->cipher = Crypt::getCipher($header);
......@@ -215,9 +219,16 @@ class Stream {
// remeber that we found a header
if (!empty($header)) {
$this->containHeader = true;
$this->headerSize = Crypt::BLOCKSIZE;
// if there's no header then decrypt the block and store it in the cache
} else {
if (!$this->getKey()) {
throw new \Exception('Encryption key not found for "' . $this->rawPath . '" during attempted read via stream');
} else {
$this->cache = Crypt::symmetricDecryptFileContent($data, $this->plainKey, $this->cipher);
}
}
fclose($handle);
}
}
......@@ -226,7 +237,7 @@ class Stream {
* @return int position of the file pointer
*/
public function stream_tell() {
return ftell($this->handle);
return $this->position;
}
/**
......@@ -234,18 +245,41 @@ class Stream {
* @param int $whence
* @return bool true if fseek was successful, otherwise false
*/
// seeking the stream tries to move the pointer on the encrypted stream to the beginning of the target block
// if that works, it flushes the current block and changes the position in the unencrypted stream
public function stream_seek($offset, $whence = SEEK_SET) {
// this wrapper needs to return "true" for success.
// the fseek call itself returns 0 on succeess
$this->flush();
$return=false;
// ignore the header and just overstep it
if ($this->containHeader) {
$offset += Crypt::BLOCKSIZE;
switch($whence) {
case SEEK_SET:
if($offset < $this->unencryptedSize && $offset >= 0) {
$newPosition=$offset;
}
break;
case SEEK_CUR:
if($offset>=0) {
$newPosition=$offset+$this->position;
}
break;
case SEEK_END:
if($this->unencryptedSize + $offset >= 0) {
$newPosition=$this->unencryptedSize+$offset;
}
break;
default:
return $return;
}
// this wrapper needs to return "true" for success.
// the fseek call itself returns 0 on succeess
return !fseek($this->handle, $offset, $whence);
$newFilePosition=floor($newPosition/6126)*Crypt::BLOCKSIZE+$this->headerSize;
if (fseek($this->handle, $newFilePosition)===0) {
$this->flush();
$this->position=$newPosition;
$return=true;
}
return $return;
}
......@@ -256,35 +290,33 @@ class Stream {
*/
public function stream_read($count) {
$this->writeCache = '';
$result = '';
if ($count !== Crypt::BLOCKSIZE) {
\OCP\Util::writeLog('Encryption library', 'PHP "bug" 21641 no longer holds, decryption system requires refactoring', \OCP\Util::FATAL);
throw new EncryptionException('expected a block size of 8192 byte', EncryptionException::UNEXPECTED_BLOCK_SIZE);
}
// Get the data from the file handle
$data = fread($this->handle, $count);
// if this block contained the header we move on to the next block
if (Crypt::isHeader($data)) {
$data = fread($this->handle, $count);
}
$result = null;
// limit to the end of the unencrypted file; otherwise getFileSize will fail and it is good practise anyway
$count=min($count,$this->unencryptedSize - $this->position);
if (strlen($data)) {
// loop over the 6126 sized unencrypted blocks
while ($count > 0) {
if (!$this->getKey()) {
$remainingLength = $count;
// Error! We don't have a key to decrypt the file with
throw new \Exception(
'Encryption key not found for "' . $this->rawPath . '" during attempted read via stream');
// update the cache of the current block
$this->readCache();
// determine the relative position in the current block
$blockPosition=($this->position % 6126);
// if entire read inside current block then only position needs to be updated
if ($remainingLength<(6126 - $blockPosition)) {
$result .= substr($this->cache,$blockPosition,$remainingLength);
$this->position += $remainingLength;
$count=0;
// otherwise remainder of current block is fetched, the block is flushed and the position updated
} else {
// Decrypt data
$result = Crypt::symmetricDecryptFileContent($data, $this->plainKey, $this->cipher);
$result .= substr($this->cache,$blockPosition);
$this->flush();
$this->position += (6126 - $blockPosition);
$count -= (6126 - $blockPosition);
}
}
......@@ -328,16 +360,14 @@ class Stream {
}
$util = new Util($this->rootView, $this->userId);
// Fetch and decrypt keyfile
// Fetch existing keyfile
$this->encKeyfile = Keymanager::getFileKey($this->rootView, $util, $this->relPath);
$this->encKeyfile = Keymanager::getFileKey($this->rootView, $this->util, $this->relPath);
// If a keyfile already exists
if ($this->encKeyfile) {
$shareKey = Keymanager::getShareKey($this->rootView, $this->keyId, $util, $this->relPath);
$shareKey = Keymanager::getShareKey($this->rootView, $this->keyId, $this->util, $this->relPath);
// if there is no valid private key return false
if ($this->privateKey === false) {
......@@ -383,6 +413,9 @@ class Stream {
fwrite($this->handle, $paddedHeader);
$this->headerWritten = true;
$this->containHeader = true;
$this->headerSize = Crypt::BLOCKSIZE;
$this->size += $this->headerSize;
}
/**
......@@ -390,7 +423,7 @@ class Stream {
* @param string $data data to be written to disk
* @note the data will be written to the path stored in the stream handle, set in stream_open()
* @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
* @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
* @note Because the encryption process used increases the length of $data, a cache is used to carry over data which would not fit in the required block size
* @note Padding is added to each encrypted block to ensure that the resulting block is exactly 8192 bytes. This is removed during stream_read
* @note PHP automatically updates the file pointer after writing data to reflect it's length. There is generally no need to update the poitner manually using fseek
*/
......@@ -402,24 +435,10 @@ class Stream {
return strlen($data);
}
if ($this->headerWritten === false) {
if ($this->size === 0) {
$this->writeHeader();
}
// Disable the file proxies so that encryption is not
// automatically attempted when the file is written to disk -
// we are handling that separately here and we don't want to
// get into an infinite loop
$proxyStatus = \OC_FileProxy::$enabled;
\OC_FileProxy::$enabled = false;
// Get the length of the unencrypted data that we are handling
$length = strlen($data);
// Find out where we are up to in the writing of data to the
// file
$pointer = ftell($this->handle);
// Get / generate the keyfile for the file we're handling
// If we're writing a new file (not overwriting an existing
// one), save the newly generated keyfile
......@@ -429,68 +448,51 @@ class Stream {
}
// If extra data is left over from the last round, make sure it
// is integrated into the next 6126 / 8192 block
if ($this->writeCache) {
// Concat writeCache to start of $data
$data = $this->writeCache . $data;
// Clear the write cache, ready for reuse - it has been
// flushed and its old contents processed
$this->writeCache = '';
$length=0;
}
// While there still remains some data to be processed & written
// loop over $data to fit it in 6126 sized unencrypted blocks
while (strlen($data) > 0) {
// Remaining length for this iteration, not of the
// entire file (may be greater than 8192 bytes)
$remainingLength = strlen($data);
// If data remaining to be written is less than the
// size of 1 6126 byte block
if ($remainingLength < 6126) {
// Set writeCache to contents of $data
// The writeCache will be carried over to the
// next write round, and added to the start of
// $data to ensure that written blocks are
// always the correct length. If there is still
// data in writeCache after the writing round
// has finished, then the data will be written
// to disk by $this->flush().
$this->writeCache = $data;
// Clear $data ready for next round
$data = '';
// set the cache to the current 6126 block
$this->readCache();
// only allow writes on seekable streams, or at the end of the encrypted stream
// for seekable streams the pointer is moved back to the beginning of the encrypted block
// flush will start writing there when the position moves to another block
if((fseek($this->handle, floor($this->position/6126)*Crypt::BLOCKSIZE + $this->headerSize) === 0) || (floor($this->position/6126)*Crypt::BLOCKSIZE + $this->headerSize === $this->size)) {
// switch the writeFlag so flush() will write the block
$this->writeFlag=1;
// determine the relative position in the current block
$blockPosition=($this->position % 6126);
// check if $data fits in current block
// if so, overwrite existing data (if any)
// update position and liberate $data
if ($remainingLength<(6126 - $blockPosition)) {
$this->cache=substr($this->cache,0,$blockPosition).$data.substr($this->cache,$blockPosition+$remainingLength);
$this->position += $remainingLength;
$length += $remainingLength;
$data = '';
// if $data doens't fit the current block, the fill the current block and reiterate
// after the block is filled, it is flushed and $data is updated
} else {
$this->cache=substr($this->cache,0,$blockPosition).substr($data,0,6126-$blockPosition);
$this->flush();
$this->position += (6126 - $blockPosition);
$length += (6126 - $blockPosition);
$data = substr($data, 6126 - $blockPosition);
}
} else {
// Read the chunk from the start of $data
$chunk = substr($data, 0, 6126);
$encrypted = $this->preWriteEncrypt($chunk, $this->plainKey);
// Write the data chunk to disk. This will be
// attended to the last data chunk if the file
// being handled totals more than 6126 bytes
fwrite($this->handle, $encrypted);
// Remove the chunk we just processed from
// $data, leaving only unprocessed data in $data
// var, for handling on the next round
$data = substr($data, 6126);
$data='';
}
}
$this->size = max($this->size, $pointer + $length);
$this->unencryptedSize += $length;
\OC_FileProxy::$enabled = $proxyStatus;
$this->unencryptedSize = max($this->unencryptedSize,$this->position);
return $length;
......@@ -537,6 +539,7 @@ class Stream {
*/
public function stream_flush() {
$this->flush();
return fflush($this->handle);
// Not a typo: http://php.net/manual/en/function.fflush.php
......@@ -546,21 +549,48 @@ class Stream {
* @return bool
*/
public function stream_eof() {
return feof($this->handle);
return ($this->position>=$this->unencryptedSize);
}
private function flush() {
if ($this->writeCache) {
// write to disk only when writeFlag was set to 1
if ($this->writeFlag === 1) {
// Disable the file proxies so that encryption is not
// automatically attempted when the file is written to disk -
// we are handling that separately here and we don't want to
// get into an infinite loop
$proxyStatus = \OC_FileProxy::$enabled;
\OC_FileProxy::$enabled = false;
// Set keyfile property for file in question
$this->getKey();
$encrypted = $this->preWriteEncrypt($this->writeCache, $this->plainKey);
$encrypted = $this->preWriteEncrypt($this->cache, $this->plainKey);
fwrite($this->handle, $encrypted);
$this->writeFlag = 0;
$this->size = max($this->size,ftell($this->handle));
\OC_FileProxy::$enabled = $proxyStatus;
}
// always empty the cache (otherwise readCache() will not fill it with the new block)
$this->cache = '';
}
$this->writeCache = '';
private function readCache() {
// cache should always be empty string when this function is called
// don't try to fill the cache when trying to write at the end of the unencrypted file when it coincides with new block
if ($this->cache === '' && !($this->position===$this->unencryptedSize && ($this->position % 6126)===0)) {
// Get the data from the file handle
$data = fread($this->handle, Crypt::BLOCKSIZE);
$result = '';
if (strlen($data)) {
if (!$this->getKey()) {
// Error! We don't have a key to decrypt the file with
throw new \Exception('Encryption key not found for "'. $this->rawPath . '" during attempted read via stream');
} else {
// Decrypt data
$result = Crypt::symmetricDecryptFileContent($data, $this->plainKey, $this->cipher);
}
}
$this->cache = $result;
}
}
......@@ -581,7 +611,7 @@ class Stream {
$proxyStatus = \OC_FileProxy::$enabled;
\OC_FileProxy::$enabled = false;
if ($this->rootView->file_exists($this->rawPath) && $this->size === 0) {
if ($this->rootView->file_exists($this->rawPath) && $this->size === $this->headerSize) {
fclose($this->handle);
$this->rootView->unlink($this->rawPath);
}
......@@ -598,7 +628,7 @@ class Stream {
$this->meta['mode'] !== 'r' &&
$this->meta['mode'] !== 'rb' &&
$this->isLocalTmpFile === false &&
$this->size > 0 &&
$this->size > $this->headerSize &&
$this->unencryptedSize > 0
) {
......
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