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fix: [Session] Redis session race condition #8323

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Merged
merged 7 commits into from
Feb 23, 2024
Merged

fix: [Session] Redis session race condition #8323

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9e37810
style: break long lines
kenjis Dec 11, 2023
ce34999
refactor: use $this->logger instead of log_message()
kenjis Dec 11, 2023
849b93a
fix: Redis Session race condition
kenjis Dec 11, 2023
63beda2
fix: close() should return false if releaseLock() failed
kenjis Feb 22, 2024
7707ddf
fix: read() should return false if lockSession() failed
kenjis Feb 22, 2024
0617a7b
refactor: by rector
kenjis Feb 22, 2024
2fa55d4
docs: add @throws
kenjis Feb 23, 2024
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67 changes: 44 additions & 23 deletions system/Session/Handlers/RedisHandler.php
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,8 @@ protected function setSavePath(): void
*
* @param string $path The path where to store/retrieve the session
* @param string $name The session name
*
* @throws RedisException
*/
public function open($path, $name): bool
{
Expand All @@ -124,12 +126,20 @@ public function open($path, $name): bool

$redis = new Redis();

if (! $redis->connect($this->savePath['protocol'] . '://' . $this->savePath['host'], ($this->savePath['host'][0] === '/' ? 0 : $this->savePath['port']), $this->savePath['timeout'])) {
if (
! $redis->connect(
$this->savePath['protocol'] . '://' . $this->savePath['host'],
($this->savePath['host'][0] === '/' ? 0 : $this->savePath['port']),
$this->savePath['timeout']
)
) {
$this->logger->error('Session: Unable to connect to Redis with the configured settings.');
} elseif (isset($this->savePath['password']) && ! $redis->auth($this->savePath['password'])) {
$this->logger->error('Session: Unable to authenticate to Redis instance.');
} elseif (isset($this->savePath['database']) && ! $redis->select($this->savePath['database'])) {
$this->logger->error('Session: Unable to select Redis database with index ' . $this->savePath['database']);
$this->logger->error(
'Session: Unable to select Redis database with index ' . $this->savePath['database']
);
} else {
$this->redis = $redis;

Expand All @@ -146,6 +156,8 @@ public function open($path, $name): bool
*
* @return false|string Returns an encoded string of the read data.
* If nothing was read, it must return false.
*
* @throws RedisException
*/
#[ReturnTypeWillChange]
public function read($id)
Expand All @@ -168,14 +180,16 @@ public function read($id)
return $data;
}

return '';
return false;
}

/**
* Writes the session data to the session storage.
*
* @param string $id The session ID
* @param string $data The encoded session data
*
* @throws RedisException
*/
public function write($id, $data): bool
{
Expand Down Expand Up @@ -222,8 +236,8 @@ public function close(): bool
$pingReply = $this->redis->ping();

if (($pingReply === true) || ($pingReply === '+PONG')) {
if (isset($this->lockKey)) {
$this->releaseLock();
if (isset($this->lockKey) && ! $this->releaseLock()) {
return false;
}

if (! $this->redis->close()) {
Expand All @@ -246,12 +260,16 @@ public function close(): bool
* Destroys a session
*
* @param string $id The session ID being destroyed
*
* @throws RedisException
*/
public function destroy($id): bool
{
if (isset($this->redis, $this->lockKey)) {
if (($result = $this->redis->del($this->keyPrefix . $id)) !== 1) {
$this->logger->debug('Session: Redis::del() expected to return 1, got ' . var_export($result, true) . ' instead.');
$this->logger->debug(
'Session: Redis::del() expected to return 1, got ' . var_export($result, true) . ' instead.'
);
}

return $this->destroyCookie();
Expand All @@ -278,6 +296,8 @@ public function gc($max_lifetime)
* Acquires an emulated lock.
*
* @param string $sessionID Session ID
*
* @throws RedisException
*/
protected function lockSession(string $sessionID): bool
{
Expand All @@ -287,48 +307,49 @@ protected function lockSession(string $sessionID): bool
// so we need to check here if the lock key is for the
// correct session ID.
if ($this->lockKey === $lockKey) {
// If there is the lock, make the ttl longer.
return $this->redis->expire($this->lockKey, 300);
}

$attempt = 0;

do {
$ttl = $this->redis->ttl($lockKey);
assert(is_int($ttl));
$result = $this->redis->set(
$lockKey,
(string) Time::now()->getTimestamp(),
// NX -- Only set the key if it does not already exist.
// EX seconds -- Set the specified expire time, in seconds.
['nx', 'ex' => 300]
);

if ($ttl > 0) {
sleep(1);
if (! $result) {
usleep(100000);

continue;
}

if (! $this->redis->setex($lockKey, 300, (string) Time::now()->getTimestamp())) {
$this->logger->error('Session: Error while trying to obtain lock for ' . $this->keyPrefix . $sessionID);

return false;
}

$this->lockKey = $lockKey;
break;
} while (++$attempt < 30);
} while (++$attempt < 300);

if ($attempt === 30) {
log_message('error', 'Session: Unable to obtain lock for ' . $this->keyPrefix . $sessionID . ' after 30 attempts, aborting.');
if ($attempt === 300) {
$this->logger->error(
'Session: Unable to obtain lock for ' . $this->keyPrefix . $sessionID
. ' after 300 attempts, aborting.'
);

return false;
}

if ($ttl === -1) {
log_message('debug', 'Session: Lock for ' . $this->keyPrefix . $sessionID . ' had no TTL, overriding.');
}

$this->lock = true;

return true;
}

/**
* Releases a previously acquired lock
*
* @throws RedisException
*/
protected function releaseLock(): bool
{
Expand Down