◇◇新语丝(www.xys.org)(xys3.dxiong.com)(www.xysforum.org)(xys2.dropin.org)◇◇

美国密歇根大学计算机安全专家发现“绿坝”存在严重的安全漏洞

（方舟子按：我只摘译了研究报告的总结和结论部分。全文内容见spluto的翻译）

　　在对“绿坝”进行了测试之后，美国密歇根大学计算机科学与工程部的
Scott Wolchok, Randy Yao和J. Alex Halderman发现“绿坝”软件存在由于编
程错误导致的严重的安全漏洞。任何网站都可以利用这些漏洞控制安装了“绿坝”
的计算机，用来偷窃私人数据、发送垃圾邮件或用作僵尸网络的机器。此外，黑
客也可以利用这些漏洞，在“绿坝”自动更新时安装恶意程序。

　　这些漏洞是在仅对该软件进行了不到12小时的测试之后就发现的。研究人员
相信这只是冰山的一角。由于“绿坝”软件频繁使用不安全的和过时的编程技术，
很容易引入许多其他的漏洞。要纠正这些问题，必须对该软件进行重大的改写，
并做仔细的重新测试。研究人员建议用户立即卸载“绿坝”以保护自己。

　　如果“绿坝”软件按现在的版本安装，将会严重削弱中国计算机安全性。虽
然他们发现的这些具体漏洞很容易打上补丁，但是这些已知的漏洞反映的是系统
性的错误，要纠正全部问题，需要对程序做大规模的改写和全面的测试，这是在
7月1日开始预装之前难以完成的。

研究报告的全文见：

http://www.cse.umich.edu/~jhalderm/pub/gd/

Summary 

We have discovered remotely-exploitable vulnerabilities in Green Dam, 
the censorship software reportedly mandated by the Chinese government. 
Any web site a Green Dam user visits can take control of the PC.

According to press reports, China will soon require all PCs sold in 
the country to include Green Dam. This software monitors web sites 
visited and other activity on the computer and blocks adult content as 
well as politically sensitive material.

We examined the Green Dam software and found that it contains serious 
security vulnerabilities due to programming errors. Once Green Dam is 
installed, any web site the user visits can exploit these problems to 
take control of the computer. This could allow malicious sites to 
steal private data, send spam, or enlist the computer in a botnet. In 
addition, we found vulnerabilities in the way Green Dam processes 
blacklist updates that could allow the software makers or others to 
install malicious code during the update process.

We found these problems with less than 12 hours of testing, and we 
believe they may be only the tip of the iceberg. Green Dam makes 
frequent use of unsafe and outdated programming practices that likely 
introduce numerous other vulnerabilities. Correcting these problems 
will require extensive changes to the software and careful retesting. 
In the meantime, we recommend that users protect themselves by 
uninstalling Green Dam immediately.

......

Conclusion

Our brief testing proves that Green Dam contains very serious security 
vulnerabilities. Unfortunately, these problems seem to reflect 
systemic flaws in the code. The software makes extensive use of 
programming techniques that are known to be unsafe, such as deprecated 
C string processing functions including sprintf and fscanf. These 
problems are compounded by the design of the program, which creates a 
large attack surface: since Green Dam filters and processes all 
Internet traffic, large parts of its code are exposed to attack.

If Green Dam is deployed in its current form, it will significantly 
weaken China's computer security. While the flaws we discovered can be 
quickly patched, correcting all the problems in the Green Dam software 
will likely require extensive rewriting and thorough testing. This 
will be difficult to achieve before China's July 1 deadline for 
deploying Green Dam nationwide.

(XYS20090613)

◇◇新语丝(www.xys.org)(xys3.dxiong.com)(www.xysforum.org)(xys2.dropin.org)◇◇