ASP.NET Form authentication被攻破-安全更新推出

flyspirit

Security Hack Exposes Forms Authentication in ASP.NET

    * By Peter Vogel
    * 09/14/2010

Two security researchers, Thai Duong and Juliano Rizzo, have discovered a bug in the default encryption mechanism used to protect the cookies normally used to implement Forms Authentication in ASP.NET. Using their tool (the Padding Oracle Exploit Tool or POET), they can repeatedly modify an ASP.NET Forms Authentication cookie encrypted using AES and, by examining the errors returned, determine the Machine Key used to encrypt the cookie. The process is claimed to be 100 percent reliable and takes between 30 and 50 minutes for any site.

Once the Machine Key is determined, attackers can create bogus forms authentication cookies. If site designers have chosen the option to embed role information in the security cookie, then attackers could arbitrarily assign themselves to administrator roles. This exposure also affects other membership provider features, spoofing protection on the ViewState, and encrypted information that might be stored in cookies or otherwise be made available at the client.

While the exposure is both wide and immediate, the fix is simple. The hack exploits a bug in .NET's implementation of AES encryption. The solution is to switch to one of the other encryption mechanisms -- to 3DES, for instance. Since encryption for the membership and roles providers is handled by ASP.NET, no modification of existing code should be required for Forms Authentication.

The encryption method can be set in the web.config file for a site, in IIS 7 for a Web server, or in the config file for .NET on a server in %SYSTEMROOT%\Microsoft.NET\Framework\version\CONFIG\. On 64-bit systems, it must also be set in %SYSTEMROOT%\Microsoft.NET\Framework64\version\CONFIG\. A typical entry would look like this:

    <machineKey validationKey="AutoGenerate,IsolateApps"         
                           validation="3DES"                           
                           decryptionKey="AutoGenerate,IsolateApps"
                           decryption="3DES" />  

On a Web farm, this setting will have to be made on all the servers in the farm.

These settings are also used to prevent spoofing (ViewState data is encoded but not encrypted), so making this change will also switch the ViewState to using 3DES. Developers who are using AES in their code to encrypt information made available at the client should consider modifying their code to use a different encryption mechanism.

Duong and Rizzo intend to provide more information at the ekoparty Security Conference on Friday, Sept. 17 in Buenos Aires.

原文连接http://visualstudiomagazine.com/ ... -security-hack.aspx

[ 本帖最后由 flyspirit 于 2010-9-30 09:57 编辑 ]

乱码

Padding Oracle Exploit Tool 比较牛B

http://www.youtube.com/v/euujmKDxmC4

bulaohu

原帖由 flyspirit 于 2010-9-15 17:11 发表
Security Hack Exposes Forms Authentication in ASP.NET

    * By Peter Vogel
    * 09/14/2010

Two security researchers, Thai Duong and Juliano Rizzo, have discovered a bug in the default encryption me ...

3DES is weaker but hell, still better than flawed implementation of AES

flyspirit

原帖由 乱码 于 2010-9-15 17:25 发表
Padding Oracle Exploit Tool 比较牛B

http://www.youtube.com/v/euujmKDxmC4

确实牛B, 有没有可能搞到这工具？

flyspirit

原帖由 bulaohu 于 2010-9-15 17:41 发表


3DES is weaker but hell, still better than flawed implementation of AES

Yes, but maybe there is some ways out there to hack 3DES as well.

bulaohu

原帖由 flyspirit 于 2010-9-15 22:07 发表


Yes, but maybe there is some ways out there to hack 3DES as well.

Have you found one?

huazhb

这个好像没有什么大问题, 只是针对那些把角色用户信息放在cookie中的网站, 如果你要到后台去validation的话应该问题就不大了

flyspirit

原帖由 bulaohu 于 2010-9-16 13:51 发表


Have you found one?

I did some search on the web, but couldn't find this tool. Maybe it's not free.

coolioo

晕

乱码

老赵的这篇文章可能更容易理解一些。

http://www.cnblogs.com/JeffreyZh ... ity-in-asp-net.html

flyspirit

原帖由 乱码 于 2010-9-26 14:25 发表
老赵的这篇文章可能更容易理解一些。

http://www.cnblogs.com/JeffreyZh ... ity-in-asp-net.html

Scott Gu的原文是说得很简单。

flyspirit

Scott Gu的Blog里有。

chech28

原帖由 bulaohu 于 2010-9-15 17:41 发表


3DES is weaker but hell, still better than flawed implementation of AES

粗粗看了下原文blog，换3des应该不解决问题，问题出在padding，而不是aes本身的实现

乱码

原帖由 chech28 于 2010-9-30 10:22 发表

粗粗看了下原文blog，换3des应该不解决问题，问题出在padding，而不是aes本身的实现

padding本身也没有问题，问题出在如果padding错或者对，错误code有很强的特性（对是500，错是404），这些code对于熟悉burp suite的人太简单了，用payload来穷举那个service，只用观察return code就可以。

如何来设置payloads，就看出水平高低了，经验丰富的高手用小的set来穷举，所以的时间短，新手时间久，payload设置的不科学，可能要几天的时间，但只要service不deny，都可以hack出来。

flyspirit

看来研究过啊。

乱码

原帖由 flyspirit 于 2010-9-30 14:02 发表
看来研究过啊。

谢谢加分，我没研究过这个issue，不过比较能理解他说的那些东西。

我对http tools比较熟，hack web site有些东西还是很相似，尤其是return code，是一样的。

cdfei

是不是我理解的问题，我觉得按照这个machineKey的长度，即使能持续获得响应，理论上用尝试密钥的方法应该不是几天几个月能完成破解的啊。

cdfei

http://ethicalhackingaspnet.codeplex.com/
大家可以去下个工具，看看自己的程序有没有问题

乱码

原帖由 cdfei 于 2010-9-30 14:53 发表
是不是我理解的问题，我觉得按照这个machineKey的长度，即使能持续获得响应，理论上用尝试密钥的方法应该不是几天几个月能完成破解的啊。

我觉得不是尝试密钥的方法，否则有点太蠢了点，虽然现在计算机及其强大，但毕竟是http request,花上几年时间是肯定的，他们对这个问题介绍的不够详细。