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Fix truncation of files upon read when using object store and encryption #28389

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merged 2 commits into from
Oct 23, 2021
Merged

Fix truncation of files upon read when using object store and encryption #28389

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44c332a
Fix truncation of files upon read when using object store and encrypt…
alanmeeson Aug 11, 2021
16f70e8
Add type hint to fread_block $blockSize param & apply cs:fix.
alanmeeson Aug 30, 2021
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32 changes: 30 additions & 2 deletions lib/private/Files/Storage/Wrapper/Encryption.php
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Original file line number Diff line number Diff line change
Expand Up @@ -471,6 +471,7 @@ public function fopen($path, $mode) {
$handle = \OC\Files\Stream\Encryption::wrap($source, $path, $fullPath, $header,
$this->uid, $encryptionModule, $this->storage, $this, $this->util, $this->fileHelper, $mode,
$size, $unencryptedSize, $headerSize, $signed);

return $handle;
}
}
Expand Down Expand Up @@ -540,7 +541,7 @@ protected function fixUnencryptedSize($path, $size, $unencryptedSize) {

// if a header exists we skip it
if ($headerSize > 0) {
fread($stream, $headerSize);
$this->fread_block($stream, $headerSize);
}

// fast path, else the calculation for $lastChunkNr is bogus
Expand All @@ -567,7 +568,7 @@ protected function fixUnencryptedSize($path, $size, $unencryptedSize) {
$count = $blockSize;

while ($count > 0) {
$data = fread($stream, $blockSize);
$data = $this->fread_block($stream, $blockSize);
$count = strlen($data);
$lastChunkContentEncrypted .= $data;
if (strlen($lastChunkContentEncrypted) > $blockSize) {
Expand Down Expand Up @@ -598,6 +599,33 @@ protected function fixUnencryptedSize($path, $size, $unencryptedSize) {
return $newUnencryptedSize;
}

/**
* fread_block
*
* This function is a wrapper around the fread function. It is based on the
* stream_read_block function from lib/private/Files/Streams/Encryption.php
* It calls stream read until the requested $blockSize was received or no remaining data is present.
* This is required as stream_read only returns smaller chunks of data when the stream fetches from a
* remote storage over the internet and it does not care about the given $blockSize.
*
* @param handle the stream to read from
* @param int $blockSize Length of requested data block in bytes
* @return string Data fetched from stream.
*/
private function fread_block($handle, int $blockSize): string {
$remaining = $blockSize;
$data = '';

do {
$chunk = fread($handle, $remaining);
$chunk_len = strlen($chunk);
$data .= $chunk;
$remaining -= $chunk_len;
} while (($remaining > 0) && ($chunk_len > 0));

return $data;
}

/**
* @param Storage\IStorage $sourceStorage
* @param string $sourceInternalPath
Expand Down