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<?php
/**
* SPDX-FileCopyrightText: 2021 Nextcloud GmbH and Nextcloud contributors
* SPDX-License-Identifier: AGPL-3.0-only
*/
namespace OCA\DAV\BulkUpload;
use OCP\AppFramework\Http;
use Psr\Log\LoggerInterface;
use Sabre\DAV\Exception;
use Sabre\DAV\Exception\BadRequest;
use Sabre\DAV\Exception\LengthRequired;
use Sabre\HTTP\RequestInterface;
class MultipartRequestParser {
/** @var resource */
private $stream;
/** @var string */
private $boundary = '';
/** @var string */
private $lastBoundary = '';
/**
* @throws BadRequest
*/
public function __construct(
RequestInterface $request,
protected LoggerInterface $logger,
) {
$stream = $request->getBody();
$contentType = $request->getHeader('Content-Type');
if (!is_resource($stream)) {
throw new BadRequest('Body should be of type resource');
}
if ($contentType === null) {
throw new BadRequest('Content-Type can not be null');
}
$this->stream = $stream;
$boundary = $this->parseBoundaryFromHeaders($contentType);
$this->boundary = '--'.$boundary."\r\n";
$this->lastBoundary = '--'.$boundary."--\r\n";
}
/**
* Parse the boundary from the Content-Type header.
* Example: Content-Type: "multipart/related; boundary=boundary_bf38b9b4b10a303a28ed075624db3978"
*
* @throws BadRequest
*/
private function parseBoundaryFromHeaders(string $contentType): string {
try {
[$mimeType, $boundary] = explode(';', $contentType);
[$boundaryKey, $boundaryValue] = explode('=', $boundary);
} catch (\Exception $e) {
throw new BadRequest('Error while parsing boundary in Content-Type header.', Http::STATUS_BAD_REQUEST, $e);
}
$boundaryValue = trim($boundaryValue);
// Remove potential quotes around boundary value.
if (str_starts_with($boundaryValue, '"') && str_ends_with($boundaryValue, '"')) {
$boundaryValue = substr($boundaryValue, 1, -1);
}
if (trim($mimeType) !== 'multipart/related') {
throw new BadRequest('Content-Type must be multipart/related');
}
if (trim($boundaryKey) !== 'boundary') {
throw new BadRequest('Boundary is invalid');
}
return $boundaryValue;
}
/**
* Check whether the stream's cursor is sitting right before the provided string.
*
* @throws Exception
*/
private function isAt(string $expectedContent): bool {
$expectedContentLength = strlen($expectedContent);
$content = fread($this->stream, $expectedContentLength);
if ($content === false) {
throw new Exception('An error occurred while checking content');
}
$seekBackResult = fseek($this->stream, -$expectedContentLength, SEEK_CUR);
if ($seekBackResult === -1) {
throw new Exception('Unknown error while seeking content', Http::STATUS_INTERNAL_SERVER_ERROR);
}
return $expectedContent === $content;
}
/**
* Check whether the stream's cursor is sitting right before the boundary.
*/
private function isAtBoundary(): bool {
return $this->isAt($this->boundary);
}
/**
* Check whether the stream's cursor is sitting right before the last boundary.
*/
public function isAtLastBoundary(): bool {
return $this->isAt($this->lastBoundary);
}
/**
* Parse and return the next part of the multipart headers.
*
* Example:
* --boundary_azertyuiop
* Header1: value
* Header2: value
*
* Content of
* the part
*
*/
public function parseNextPart(): array {
$this->readBoundary();
$headers = $this->readPartHeaders();
$content = $this->readPartContent((int)$headers['content-length'], $headers['x-file-md5']);
return [$headers, $content];
}
/**
* Read the boundary and check its content.
*
* @throws BadRequest
*/
private function readBoundary(): string {
if (!$this->isAtBoundary()) {
throw new BadRequest('Boundary not found where it should be.');
}
return fread($this->stream, strlen($this->boundary));
}
/**
* Return the headers of a part of the multipart body.
*
* @throws Exception
* @throws BadRequest
* @throws LengthRequired
*/
private function readPartHeaders(): array {
$headers = [];
while (($line = fgets($this->stream)) !== "\r\n") {
if ($line === false) {
throw new Exception('An error occurred while reading headers of a part');
}
if (!str_contains($line, ':')) {
$this->logger->error('Header missing ":" on bulk request: ' . json_encode($line));
throw new Exception('An error occurred while reading headers of a part', Http::STATUS_BAD_REQUEST);
}
try {
[$key, $value] = explode(':', $line, 2);
$headers[strtolower(trim($key))] = trim($value);
} catch (\Exception $e) {
throw new BadRequest('An error occurred while parsing headers of a part', Http::STATUS_BAD_REQUEST, $e);
}
}
if (!isset($headers['content-length'])) {
throw new LengthRequired('The Content-Length header must not be null.');
}
if (!isset($headers['x-file-md5'])) {
throw new BadRequest('The X-File-MD5 header must not be null.');
}
return $headers;
}
/**
* Return the content of a part of the multipart body.
*
* @throws Exception
* @throws BadRequest
*/
private function readPartContent(int $length, string $md5): string {
$computedMd5 = $this->computeMd5Hash($length);
if ($md5 !== $computedMd5) {
throw new BadRequest('Computed md5 hash is incorrect.');
}
if ($length === 0) {
$content = '';
} else {
$content = stream_get_line($this->stream, $length);
}
if ($content === false) {
throw new Exception("Fail to read part's content.");
}
if ($length !== 0 && feof($this->stream)) {
throw new Exception('Unexpected EOF while reading stream.');
}
// Read '\r\n'.
stream_get_contents($this->stream, 2);
return $content;
}
/**
* Compute the MD5 hash of the next x bytes.
*/
private function computeMd5Hash(int $length): string {
$context = hash_init('md5');
hash_update_stream($context, $this->stream, $length);
fseek($this->stream, -$length, SEEK_CUR);
return hash_final($context);
}
}
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