因为排查一个问题，顺带着熟悉了一下Discuz!与Ucenter注册和登录的机制，特整理分析。

下面以Discuz! X2.5为例分析代码实现。

1.注册

找到source\class\class_member.php文件，有如下代码：

$uid = uc_user_register(addslashes($username), $password, $email, $questionid, $answer, $_G['clientip']);

uc_user_register定义在uc_client\client.php文件，代码如下：

function uc_user_register($username, $password, $email, $questionid = '', $answer = '', $regip = '') {
	return call_user_func(UC_API_FUNC, 'user', 'register', array('username'=>$username, 'password'=>$password, 'email'=>$email, 'questionid'=>$questionid, 'answer'=>$answer, 'regip' => $regip));
}

此函数会回调uc_server下的方法，执行文件为uc_server\control\user.php，执行代码如下：

function onregister() {
	$this->init_input();
	$username = $this->input('username');
	$password =  $this->input('password');
	$email = $this->input('email');
	$questionid = $this->input('questionid');
	$answer = $this->input('answer');
	$regip = $this->input('regip');

	if(($status = $this->_check_username($username)) < 0) {
		return $status;
	}
	if(($status = $this->_check_email($email)) < 0) {
		return $status;
	}

	$uid = $_ENV['user']->add_user($username, $password, $email, 0, $questionid, $answer, $regip);
	return $uid;
}

add_user定义在uc_server\model\user.php文件，代码如下：

function add_user($username, $password, $email, $uid = 0, $questionid = '', $answer = '', $regip = '') {
	$regip = empty($regip) ? $this->base->onlineip : $regip;
	$salt = substr(uniqid(rand()), -6);
	$password = md5(md5($password).$salt);
	$sqladd = $uid ? "uid='".intval($uid)."'," : '';
	$sqladd .= $questionid > 0 ? " secques='".$this->quescrypt($questionid, $answer)."'," : " secques='',";
	$this->db->query("INSERT INTO ".UC_DBTABLEPRE."members SET $sqladd username='$username', password='$password', email='$email', regip='$regip', regdate='".$this->base->time."', salt='$salt'");
	$uid = $this->db->insert_id();
	$this->db->query("INSERT INTO ".UC_DBTABLEPRE."memberfields SET uid='$uid'");
	return $uid;
}

这里会将用户信息写入Ucenter的用户表中。
在这里可以看到用户密码不是用明文存储的，加密的格式为：

md5(md5(用户密码) . 6位随机串)

2.登录

找到source\class\class_member.php文件，有如下代码：

$result = userlogin($_GET['username'], $_GET['password'], $_GET['questionid'], $_GET['answer'], $this->setting['autoidselect'] ? 'auto' : $_GET['loginfield'], $_G['clientip']);

userlogin定义在source\function\function_member.php文件，函数内部有如下代码：

if($isuid == 3) {
	if(!strcmp(dintval($username), $username)) {
		$return['ucresult'] = uc_user_login($username, $password, 1, 1, $questionid, $answer, $ip);
	} elseif(isemail($username)) {
		$return['ucresult'] = uc_user_login($username, $password, 2, 1, $questionid, $answer, $ip);
	}
	if($return['ucresult'][0] <= 0 && $return['ucresult'][0] != -3) {
		$return['ucresult'] = uc_user_login(addslashes($username), $password, 0, 1, $questionid, $answer, $ip);
	}
} else {
	$return['ucresult'] = uc_user_login(addslashes($username), $password, $isuid, 1, $questionid, $answer, $ip);
}

uc_user_login定义在uc_client\client.php文件，代码如下：

function uc_user_login($username, $password, $isuid = 0, $checkques = 0, $questionid = '', $answer = '') {
	$isuid = intval($isuid);
	$return = call_user_func(UC_API_FUNC, 'user', 'login', array('username'=>$username, 'password'=>$password, 'isuid'=>$isuid, 'checkques'=>$checkques, 'questionid'=>$questionid, 'answer'=>$answer));
	return UC_CONNECT == 'mysql' ? $return : uc_unserialize($return);
}

此函数会回调uc_server下的方法，执行文件为uc_server\control\user.php，执行代码如下：

function onlogin() {
	$this->init_input();
	$isuid = $this->input('isuid');
	$username = $this->input('username');
	$password = $this->input('password');
	$checkques = $this->input('checkques');
	$questionid = $this->input('questionid');
	$answer = $this->input('answer');
	if($isuid == 1) {
		$user = $_ENV['user']->get_user_by_uid($username);
	} elseif($isuid == 2) {
		$user = $_ENV['user']->get_user_by_email($username);
	} else {
		$user = $_ENV['user']->get_user_by_username($username);
	}

	$passwordmd5 = preg_match('/^\w{32}$/', $password) ? $password : md5($password);
	if(empty($user)) {
		$status = -1;
	} elseif($user['password'] != md5($passwordmd5.$user['salt'])) {
		$status = -2;
	} elseif($checkques && $user['secques'] != '' && $user['secques'] != $_ENV['user']->quescrypt($questionid, $answer)) {
		$status = -3;
	} else {
		$status = $user['uid'];
	}
	$merge = $status != -1 && !$isuid && $_ENV['user']->check_mergeuser($username) ? 1 : 0;
	return array($status, $user['username'], $password, $user['email'], $merge);
}

这里会验证用户输入的密码是否和Ucenter里存储的密码一致。
验证的格式为：

首先会验证用户密码是否为32位，如果不是则对用户输出的密码进行md5处理。（32位验证是后台设置的加密传输密码，开启后会先进行md5然后才传递给Ucenter）
Ucenter里存储的对应用户的加密后的密码 == md5(格式化后的用户输入的密码 . Ucenter里存储的对应用户的6位随机串)