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phab/src/aphront/sink/AphrontHTTPSink.php
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AphrontHTTPSink.php
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<?php
/**
* Abstract class which wraps some sort of output mechanism for HTTP responses.
* Normally this is just @{class:AphrontPHPHTTPSink}, which uses "echo" and
* "header()" to emit responses.
*
* Mostly, this class allows us to do install security or metrics hooks in the
* output pipeline.
*
* @task write Writing Response Components
* @task emit Emitting the Response
*/
abstract class AphrontHTTPSink extends Phobject {
/* -( Writing Response Components )---------------------------------------- */
/**
* Write an HTTP status code to the output.
*
* @param int Numeric HTTP status code.
* @return void
*/
final public function writeHTTPStatus($code, $message = '') {
if (!preg_match('/^\d{3}$/', $code)) {
throw new Exception(pht("Malformed HTTP status code '%s'!", $code));
}
$code = (int)$code;
$this->emitHTTPStatus($code, $message);
}
/**
* Write HTTP headers to the output.
*
* @param list<pair> List of <name, value> pairs.
* @return void
*/
final public function writeHeaders(array $headers) {
foreach ($headers as $header) {
if (!is_array($header) || count($header) !== 2) {
throw new Exception(pht('Malformed header.'));
}
list($name, $value) = $header;
if (strpos($name, ':') !== false) {
throw new Exception(
pht(
'Declining to emit response with malformed HTTP header name: %s',
$name));
}
// Attackers may perform an "HTTP response splitting" attack by making
// the application emit certain types of headers containing newlines:
//
// http://en.wikipedia.org/wiki/HTTP_response_splitting
//
// PHP has built-in protections against HTTP response-splitting, but they
// are of dubious trustworthiness:
//
// http://news.php.net/php.internals/57655
if (preg_match('/[\r\n\0]/', $name.$value)) {
throw new Exception(
pht(
'Declining to emit response with unsafe HTTP header: %s',
"<'".$name."', '".$value."'>."));
}
}
foreach ($headers as $header) {
list($name, $value) = $header;
$this->emitHeader($name, $value);
}
}
/**
* Write HTTP body data to the output.
*
* @param string Body data.
* @return void
*/
final public function writeData($data) {
$this->emitData($data);
}
/**
* Write an entire @{class:AphrontResponse} to the output.
*
* @param AphrontResponse The response object to write.
* @return void
*/
final public function writeResponse(AphrontResponse $response) {
$response->willBeginWrite();
// Build the content iterator first, in case it throws. Ideally, we'd
// prefer to handle exceptions before we emit the response status or any
// HTTP headers.
$data = $response->getContentIterator();
$all_headers = array_merge(
$response->getHeaders(),
$response->getCacheHeaders());
$this->writeHTTPStatus(
$response->getHTTPResponseCode(),
$response->getHTTPResponseMessage());
$this->writeHeaders($all_headers);
// Allow clients an unlimited amount of time to download the response.
// This allows clients to perform a "slow loris" attack, where they
// download a large response very slowly to tie up process slots. However,
// concurrent connection limits and "RequestReadTimeout" already prevent
// this attack. We could add our own minimum download rate here if we want
// to make this easier to configure eventually.
// For normal page responses, we've fully rendered the page into a string
// already so all that's left is writing it to the client.
// For unusual responses (like large file downloads) we may still be doing
// some meaningful work, but in theory that work is intrinsic to streaming
// the response.
set_time_limit(0);
$abort = false;
foreach ($data as $block) {
if (!$this->isWritable()) {
$abort = true;
break;
}
$this->writeData($block);
}
$response->didCompleteWrite($abort);
}
/* -( Emitting the Response )---------------------------------------------- */
abstract protected function emitHTTPStatus($code, $message = '');
abstract protected function emitHeader($name, $value);
abstract protected function emitData($data);
abstract protected function isWritable();
}
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