WordPress用户密码加密和验证的详细解释

正文：

wordpress 用户密码加密和验证的原理是 wordpress 开发人员必须掌握的。虽然可以通过使用 WordPress 提供的函数直接完成，但在与第三方用户系统连接时，您必须知道如何计算它。WordPress 用户密码加密和验证功能实现起来比较简单，官方将其编写为不需要依赖其他文件的PHP类，可以直接使用。该文件位于:/WP-includes/class-PHP pass.php。

最近因为 wordpress 核心功能太多无法使用，速度特别慢，这让我产生了用 PHP 重写网站前端的想法。按照我的想法，后端仍然由 wordpress 管理，前端放弃 wordpress 核心，使用 PHP+mysql。根据我的测试，响应时间可以缩短到 10ms，远低于当前的 100 ms .而且即使分离的前端出现问题，它也可以无损切换到当前状态，wordpress 的主题模板仍然可以使用。

如果没有用户系统，只是作为一个显示站，实现起来非常简单。但是代码狗有 1W+的用户，所以绝对不仅仅是展示效果，所以如何将分离的前端与 wordpress 后端连接起来是一个难题。为了实现这些功能，首先要解决的是了解 wordpress 用户帐户密码的加密和解密方法，然后是 cookie 的设置和验证。

加密解密验证源码如下：

<?php
/**
 * Portable PHP password hashing framework.
 * @package phpass
 * @since 2.5.0
 * @version 0.5 / WordPress
 * @link https://www.openwall.com/phpass/
 */

#
# Portable PHP password hashing framework.
#
# Version 0.5 / WordPress.
#
# Written by Solar Designer <solar at openwall.com> in 2004-2006 and placed in
# the public domain.  Revised in subsequent years, still public domain.
#
# There's absolutely no warranty.
#
# The homepage URL for this framework is:
#
#	http://www.openwall.com/phpass/
#
# Please be sure to update the Version line if you edit this file in any way.
# It is suggested that you leave the main version number intact, but indicate
# your project name (after the slash) and add your own revision information.
#
# Please do not change the "private" password hashing method implemented in
# here, thereby making your hashes incompatible.  However, if you must, please
# change the hash type identifier (the "$P$") to something different.
#
# Obviously, since this code is in the public domain, the above are not
# requirements (there can be none), but merely suggestions.
#

/**
 * Portable PHP password hashing framework.
 *
 * @package phpass
 * @version 0.5 / WordPress
 * @link https://www.openwall.com/phpass/
 * @since 2.5.0
 */
class PasswordHash {
	var $itoa64;
	var $iteration_count_log2;
	var $portable_hashes;
	var $random_state;

	function __construct($iteration_count_log2, $portable_hashes)
	{
		$this->itoa64 = './0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';

		if ($iteration_count_log2 < 4 || $iteration_count_log2 > 31)
			$iteration_count_log2 = 8;
		$this->iteration_count_log2 = $iteration_count_log2;

		$this->portable_hashes = $portable_hashes;

		$this->random_state = microtime();
		if (function_exists('getmypid'))
			$this->random_state .= getmypid();
	}

	function PasswordHash($iteration_count_log2, $portable_hashes)
	{
		self::__construct($iteration_count_log2, $portable_hashes);
	}

	function get_random_bytes($count)
	{
		$output = '';
		if (@is_readable('/dev/urandom') &&
		    ($fh = @fopen('/dev/urandom', 'rb'))) {
			$output = fread($fh, $count);
			fclose($fh);
		}

		if (strlen($output) < $count) {
			$output = '';
			for ($i = 0; $i < $count; $i += 16) {
				$this->random_state =
				    md5(microtime() . $this->random_state);
				$output .= md5($this->random_state, TRUE);
			}
			$output = substr($output, 0, $count);
		}

		return $output;
	}

	function encode64($input, $count)
	{
		$output = '';
		$i = 0;
		do {
			$value = ord($input[$i++]);
			$output .= $this->itoa64[$value & 0x3f];
			if ($i < $count)
				$value |= ord($input[$i]) << 8;
			$output .= $this->itoa64[($value >> 6) & 0x3f];
			if ($i++ >= $count)
				break;
			if ($i < $count)
				$value |= ord($input[$i]) << 16;
			$output .= $this->itoa64[($value >> 12) & 0x3f];
			if ($i++ >= $count)
				break;
			$output .= $this->itoa64[($value >> 18) & 0x3f];
		} while ($i < $count);

		return $output;
	}

	function gensalt_private($input)
	{
		$output = '$P$';
		$output .= $this->itoa64[min($this->iteration_count_log2 +
			((PHP_VERSION >= '5') ? 5 : 3), 30)];
		$output .= $this->encode64($input, 6);

		return $output;
	}

	function crypt_private($password, $setting)
	{
		$output = '*0';
		if (substr($setting, 0, 2) === $output)
			$output = '*1';

		$id = substr($setting, 0, 3);
		# We use "$P$", phpBB3 uses "$H$" for the same thing
		if ($id !== '$P$' && $id !== '$H$')
			return $output;

		$count_log2 = strpos($this->itoa64, $setting[3]);
		if ($count_log2 < 7 || $count_log2 > 30)
			return $output;

		$count = 1 << $count_log2;

		$salt = substr($setting, 4, 8);
		if (strlen($salt) !== 8)
			return $output;

		# We were kind of forced to use MD5 here since it's the only
		# cryptographic primitive that was available in all versions
		# of PHP in use.  To implement our own low-level crypto in PHP
		# would have resulted in much worse performance and
		# consequently in lower iteration counts and hashes that are
		# quicker to crack (by non-PHP code).
		$hash = md5($salt . $password, TRUE);
		do {
			$hash = md5($hash . $password, TRUE);
		} while (--$count);

		$output = substr($setting, 0, 12);
		$output .= $this->encode64($hash, 16);

		return $output;
	}

	function gensalt_blowfish($input)
	{
		# This one needs to use a different order of characters and a
		# different encoding scheme from the one in encode64() above.
		# We care because the last character in our encoded string will
		# only represent 2 bits.  While two known implementations of
		# bcrypt will happily accept and correct a salt string which
		# has the 4 unused bits set to non-zero, we do not want to take
		# chances and we also do not want to waste an additional byte
		# of entropy.
		$itoa64 = './ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';

		$output = '$2a$';
		$output .= chr(ord('0') + $this->iteration_count_log2 / 10);
		$output .= chr(ord('0') + $this->iteration_count_log2 % 10);
		$output .= '$';

		$i = 0;
		do {
			$c1 = ord($input[$i++]);
			$output .= $itoa64[$c1 >> 2];
			$c1 = ($c1 & 0x03) << 4;
			if ($i >= 16) {
				$output .= $itoa64[$c1];
				break;
			}

			$c2 = ord($input[$i++]);
			$c1 |= $c2 >> 4;
			$output .= $itoa64[$c1];
			$c1 = ($c2 & 0x0f) << 2;

			$c2 = ord($input[$i++]);
			$c1 |= $c2 >> 6;
			$output .= $itoa64[$c1];
			$output .= $itoa64[$c2 & 0x3f];
		} while (1);

		return $output;
	}

	function HashPassword($password)
	{
		if ( strlen( $password ) > 4096 ) {
			return '*';
		}

		$random = '';

		if (CRYPT_BLOWFISH === 1 && !$this->portable_hashes) {
			$random = $this->get_random_bytes(16);
			$hash =
			    crypt($password, $this->gensalt_blowfish($random));
			if (strlen($hash) === 60)
				return $hash;
		}

		if (strlen($random) < 6)
			$random = $this->get_random_bytes(6);
		$hash =
		    $this->crypt_private($password,
		    $this->gensalt_private($random));
		if (strlen($hash) === 34)
			return $hash;

		# Returning '*' on error is safe here, but would _not_ be safe
		# in a crypt(3)-like function used _both_ for generating new
		# hashes and for validating passwords against existing hashes.
		return '*';
	}

	function CheckPassword($password, $stored_hash)
	{
		if ( strlen( $password ) > 4096 ) {
			return false;
		}

		$hash = $this->crypt_private($password, $stored_hash);
		if ($hash[0] === '*')
			$hash = crypt($password, $stored_hash);

		# This is not constant-time.  In order to keep the code simple,
		# for timing safety we currently rely on the salts being
		# unpredictable, which they are at least in the non-fallback
		# cases (that is, when we use /dev/urandom and bcrypt).
		return $hash === $stored_hash;
	}
}

wordpress 用户密码加密后的密文格式：

$P$BcSda3/tRXQcRZMPj3cUI0jZJFdMgL0
$P$BNclJc4wbM.vSjKPYxKggDPtw3siXQ0

同样的密码每次加密结果都不同

第一段：$P$格式固定
第二段：只有一个字符。若 php 版本大于 5.0 则为 B，否则为 9
第三段：8 位 salt
第四段：22 位，真正加密后的密码
PHP 版本低于 5.0 则使用的 md5 加密，具体加密方法这里不详细说了，已经有网友发布了相关文章，高于则使用本文加密方式。

简单测试

$wp_hasher = new PasswordHash( 8, true );
print($wp_hasher->HashPassword('你的密码'));
//$check = $wp_hasher->CheckPassword( '你的密码','$P$BHNlQVxpEEuKKtm2q539mCWsKA8dwq/' );
//print($check);

将生成的密码直接替换掉数据库中的密码，能够正常登录。注意：memcached 缓存会存储密码，测试时需刷新缓存！

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