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PhabricatorAuthSessionEngine.php
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Sun, Jun 15, 18:13

PhabricatorAuthSessionEngine.php
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<?php
final class PhabricatorAuthSessionEngine extends Phobject {
public function loadUserForSession($session_type, $session_key) {
$session_table = new PhabricatorAuthSession();
$user_table = new PhabricatorUser();
$conn_r = $session_table->establishConnection('w');
$info = queryfx_one(
$conn_r,
'SELECT u.* FROM %T u JOIN %T s ON u.phid = s.userPHID
AND s.type LIKE %> AND s.sessionKey = %s',
$user_table->getTableName(),
$session_table->getTableName(),
$session_type.'-',
PhabricatorHash::digest($session_key));
if (!$info) {
return null;
}
return $user_table->loadFromArray($info);
}
/**
* Issue a new session key for a given identity. Phabricator supports
* different types of sessions (like "web" and "conduit") and each session
* type may have multiple concurrent sessions (this allows a user to be
* logged in on multiple browsers at the same time, for instance).
*
* Note that this method is transport-agnostic and does not set cookies or
* issue other types of tokens, it ONLY generates a new session key.
*
* You can configure the maximum number of concurrent sessions for various
* session types in the Phabricator configuration.
*
* @param string Session type, like "web".
* @param phid Identity to establish a session for, usually a user PHID.
* @return string Newly generated session key.
*/
public function establishSession($session_type, $identity_phid) {
$session_table = new PhabricatorAuthSession();
$conn_w = $session_table->establishConnection('w');
if (strpos($session_type, '-') !== false) {
throw new Exception("Session type must not contain hyphen ('-')!");
}
// We allow multiple sessions of the same type, so when a caller requests
// a new session of type "web", we give them the first available session in
// "web-1", "web-2", ..., "web-N", up to some configurable limit. If none
// of these sessions is available, we overwrite the oldest session and
// reissue a new one in its place.
$session_limit = 1;
switch ($session_type) {
case 'web':
$session_limit = PhabricatorEnv::getEnvConfig('auth.sessions.web');
break;
case 'conduit':
$session_limit = PhabricatorEnv::getEnvConfig('auth.sessions.conduit');
break;
default:
throw new Exception("Unknown session type '{$session_type}'!");
}
$session_limit = (int)$session_limit;
if ($session_limit <= 0) {
throw new Exception(
"Session limit for '{$session_type}' must be at least 1!");
}
// NOTE: Session establishment is sensitive to race conditions, as when
// piping `arc` to `arc`:
//
// arc export ... | arc paste ...
//
// To avoid this, we overwrite an old session only if it hasn't been
// re-established since we read it.
// Consume entropy to generate a new session key, forestalling the eventual
// heat death of the universe.
$session_key = Filesystem::readRandomCharacters(40);
// Load all the currently active sessions.
$sessions = queryfx_all(
$conn_w,
'SELECT type, sessionKey, sessionStart FROM %T
WHERE userPHID = %s AND type LIKE %>',
$session_table->getTableName(),
$identity_phid,
$session_type.'-');
$sessions = ipull($sessions, null, 'type');
$sessions = isort($sessions, 'sessionStart');
$existing_sessions = array_keys($sessions);
// UNGUARDED WRITES: Logging-in users don't have CSRF stuff yet.
$unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
$retries = 0;
while (true) {
// Choose which 'type' we'll actually establish, i.e. what number we're
// going to append to the basic session type. To do this, just check all
// the numbers sequentially until we find an available session.
$establish_type = null;
for ($ii = 1; $ii <= $session_limit; $ii++) {
$try_type = $session_type.'-'.$ii;
if (!in_array($try_type, $existing_sessions)) {
$establish_type = $try_type;
$expect_key = PhabricatorHash::digest($session_key);
$existing_sessions[] = $try_type;
// Ensure the row exists so we can issue an update below. We don't
// care if we race here or not.
queryfx(
$conn_w,
'INSERT IGNORE INTO %T (userPHID, type, sessionKey, sessionStart)
VALUES (%s, %s, %s, 0)',
$session_table->getTableName(),
$identity_phid,
$establish_type,
PhabricatorHash::digest($session_key));
break;
}
}
// If we didn't find an available session, choose the oldest session and
// overwrite it.
if (!$establish_type) {
$oldest = reset($sessions);
$establish_type = $oldest['type'];
$expect_key = $oldest['sessionKey'];
}
// This is so that we'll only overwrite the session if it hasn't been
// refreshed since we read it. If it has, the session key will be
// different and we know we're racing other processes. Whichever one
// won gets the session, we go back and try again.
queryfx(
$conn_w,
'UPDATE %T SET sessionKey = %s, sessionStart = UNIX_TIMESTAMP()
WHERE userPHID = %s AND type = %s AND sessionKey = %s',
$session_table->getTableName(),
PhabricatorHash::digest($session_key),
$identity_phid,
$establish_type,
$expect_key);
if ($conn_w->getAffectedRows()) {
// The update worked, so the session is valid.
break;
} else {
// We know this just got grabbed, so don't try it again.
unset($sessions[$establish_type]);
}
if (++$retries > $session_limit) {
throw new Exception("Failed to establish a session!");
}
}
$log = PhabricatorUserLog::initializeNewLog(
null,
$identity_phid,
PhabricatorUserLog::ACTION_LOGIN);
$log->setDetails(
array(
'session_type' => $session_type,
'session_issued' => $establish_type,
));
$log->setSession($session_key);
$log->save();
return $session_key;
}
}

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