怎样保护用户密码才靠谱

CSDN 密码泄露,把我的也给泄掉了⋯⋯好几年没用了,躺着也中枪啊。幸好只是一个低级别的密码。忙着改密码的同时,也在考虑要不要启用 sha1(master password + domain name) 的密码方案。。。

 

好吧,还是说点有趣的,怎样保护用户密码才靠谱?

1、数据库存储

原始:

save2db(username, password)

进化:

save2db(username, md5(password))

再进化:

random salt = GUID

save2db(username, salt, md5(password.salt))

靠谱方案:

const globalSalt = [a-z]+[A-Z]+[0-9]+[%$#@!~*…]+

random privateSalt = GUID

save2db(username, privateSalt, sha1(globalSalt.password.privateSalt))

可接受的简化方案:

save2db(username, sha1(domain.password.username)

 

为什么要搞个 globalSalt?

globalSalt 写在代码中,也就是说,万一你的数据库泄露了(代码还没泄露),仍然有一道安全防线在保护你的用户。只有一个 salt 的情况下,虽然使得字典攻击变得更难,但如果用户密码不够长、不够复杂,暴力攻击仍是很轻松的事(因为既然你的数据库已经泄露了,用户的 salt 自然也就露掉了)。而有了 globalSalt,只要代码仍然安全(攻击者不知道你 globalSalt 的值为多少的情况下),它就能保证跟用户的密码组合起来变得非常长、非常复杂,超出了暴力破解的实际可能。

 

可不可以只用一个 globalSalt?

不可以。否则,好事者就可能在知道你 globalSalt 的情况为你这个网站专门生成一个字典,一次性搞定所有用户。privateSalt 的存在,使各个用户的 salt 都不一样,因此需要为每个用户生成一个专用的字典,不具备实际可行性。简单地说,globalSalt 防暴力攻击、privateSalt 防字典攻击。

 

简化方案中,可不可以不要 domain,只用 username?

不可以。一、有的用户,即使是用户名 + 密码仍然不够长,抗不了暴力;二、我们不仅是要(尽可能)保证 salt 的全站唯一,而是要全球唯一。有些用户名如 admin, root, webmaster 等非常通用,起不到 salt 应有的作用。

 

2、修改密码

    • 改密码,必先验证老密码,而不是登录着就让改。否则,就给 Session Hijacking 变成进一步的灾难修了条大道。
    • 如果老密码输错了,启用验证码保护。否则,就是 Session Hijacking 后暴力破解的后门。
    • 清 session,使所有登录的(如果支持一个帐号同时多处登录)cookie 失效。改了密码,就应该要求该用户所有会话重新验证。因为用户密码已经改了,表示原密码不再是有效的,甚至可能已经泄露了。

     

    3、其它

      • 传输密码时用 HTTPS;
      • 最好全程 HTTPS,杜绝 Session Hijacking(WIFI 什么的,最容易中招了);
      • 避免 Session Fixation(永远重新生成,不通过 URL 传输 SID);
      • 除特别需要,httpd 进程对代码目录只应该有读权限,而不应有写权限。你懂的,后门啊什么的最讨厌了~;
      • 定期 $ git status(.git 目录为 root 专属),如果不是 working directory clean,那就该报警了喂!
      • Injection、XSS 什么的,呃⋯超纲了,打住~。

       

      虽然都是很简单的事,但如果一条条验证,估计国内绝大部分网站都能找出问题,包括那些人们觉得很牛逼的(CSDN,程序员的社区啊,“全球最大”啊…存储密码用的是最原始的方法)。关于保护用户信息安全,你还有什么想法?

        • 米饭
        • 十二月 27th, 2011 10:05下午

        写的不错

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