Malicious Xcode could spread via download manager Xunlei

Analyzer是GreatFire的第一个项目,在2011年上线后,它一如以往的为大家提供测试服务直至今日。现在,我们做了一个新的项目叫做"Blocky",欢迎大家试用这个全新的版本!如果您对此有任何意见和建议,请发送邮件到support@greatfire.org

What’s at stake?

We reported last week that popular Chinese iOS apps were compromised in an unprecedented malware attack. We discovered that the source of the infection was compromised copies of Xcode hosted on Baidu Pan. Apple has published an article urging developers to download Xcode directly from the Mac App Store, or from the Apple Developer website and validate signatures. We’ve now discovered that even if a developer uses a download link seemingly from Apple, he might still be possible to obtain a compromised copy of Xcode.

Please note that we do not have evidence that such attacks has happened. But it is an easy attack that anyone can implement.

How does it work?

This compromise happened because of Xunlei. Xunlei is the most popular download manager in China. Much of its popularity is due to the fact they can accelerate download speeds by pulling resources from other Xunlei users as well as cached copies on the Xunlei server. All of this, however, is invisible to users. Users can simply enter a regular http download address into Xunlei  download manager and the download will start. Chinese developers were using direct download addresses such as http://adcdownload.apple.com/Developer_Tools/Xcode_7/Xcode_7.dmg to download Xcode.

Because of Xunlei’s P2P and server cache, download speeds would be much faster than the Mac App Store. Downloading via Xunlei also means that developers do not need to be enrolled in the Apple developer program. Direct downloads of Xcode via the developer program cost $99. Because the URL belongs to Apple, users were tricked into thinking that the download link was authentic and hence the Xcode copy. But in actual fact, the file is not authentic because it comes from Xunlei’s P2P and server cache.

The way to “host” a compromised copy of Xcode on Apple’s server is to trick Xunlei locally and let the error propagate. For example, a malicious user can hijack adcdownload.apple.com locally via host file and download from a non-exsistant URL http://adcdownload.apple.com/xcode-fake-1.1.1.1.dmg. Xunlei will then correlate this URL with the file specified by the malicious user and provide this file to other innocent users.

This is what actually happens when you use Xunlei to download http://adcdownload.apple.com/xcode-fake-1.1.1.1.dmg

But if you look at the details of the download source, you can see that 0% of the download is from the original server (i.e adcdownload.apple.com) while the server cache accounts for 26% and P2P accounts for 3% of the download.

You can also see that attempts by Xunlei to connect to adcdownload.apple.com were redirected to https://developer.apple.com/unauthorized/  because Apple only allows users in the Apple developer program to access the page.

Malicious attackers can poison Xunlei with a URL similar to a real Apple Xcode URL and then post the fake URL on forums and download sites. Most Chinese users by default use Xunlei to download. In fact, they have to if they are not enrolled in the Apple developer program. Most will have a compromised copy of Xcode, seemingly downloaded from Apple.

 

What can developers do to prevent future attacks?

Our suggestions are exactly the same from our last blog post.

  • Always download Xcode from the official Mac App Store. For other developer tools, always download these from official sources.

  • Always check the digital signature of developer tools. It is irresponsible for developers to ignore signature warnings. Xcode clearly should have been signed by Apple; all other versions should have produced user warnings.

  • Separate your development system with your everyday system. Development systems should be used solely for development and not for browsing random sites. If physical separation presents too much of a problem for developers, at the very least, a dedicated user account for development should be used.

 

Xunlei users should be cautious

As demonstrated above, Xunlei cannot be trusted to download the correct file, even if the download link is HTTPS. Users should manually check hash after download or use the browser’s download function.

 

References:

https://v2ex.com/t/222553

 

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星期一, 11月 25, 2024

China’s New Effort to Achieve Cyber Sovereignty

How Real-Name Registration policies create an “ideological firewall” that chills dissent by eliminating user anonymity and selectively restricting transnational access to Chinese social media apps.

星期四, 8月 10, 2023

1.4 million people used FreeBrowser to circumvent the Great Firewall of Turkmenistan

Since 2021, the authorities in Turkmenistan have taken exceptional measures to crack down on the use of circumvention tools. Citizens have been forced to swear on the Koran that they will not use a VPN. Circumvention tool websites have been systematically blocked. Arbitrary searches of mobile devices have also taken place and have even targeted school children and teachers.

The government has also blocked servers hosting VPNs which led to “near complete” internet shutdowns on several occasions in 2022. Current reports indicate that 66 hosting providers, 19 social networks and messaging platforms, and 10 leading content delivery networks (CDNs), are blocked in the country. The government presumably is unconcerned about the negative economic impact that such shutdowns can cause.

星期五, 3月 18, 2022

Well-intentioned decisions have just made it easier for Putin to control the Russian Internet

This article is in large part inspired by a recent article from Meduza (in Russian).

Since the beginning of the war in Ukraine, Russian users have had problems accessing government websites and online banking clients. Browsers began to mark these sites as unsafe and drop the connection. The reason is the revocation of digital security certificates by foreign certificate authorities (either as a direct consequence of sanctions or as an independent, good will move); without them, browsers do not trust sites and “protect” their users from them.

However, these actions, caused - or at least triggered by - a desire to punish Russia for their gruesome actions in Ukraine, will have long-lasting consequences for Russian netizens.

Digital certificates are needed to confirm that the site the user wants to visit is not fraudulent. The certificates contain encryption keys to establish a secure connection between the site and the user. It is very easy to understand whether a page on the Internet is protected by a certificate. One need just look at the address bar of the browser. If the address begins with the https:// prefix, and there is a lock symbol next to the address, the page is protected. By clicking on this lock, you can see the status of the connection, the name of the Certification Authority (CA) that issued the certificate, and its validity period.

There are several dozen commercial and non-commercial organizations in the world that have digital root certificates, but 3/4 of all certificates are issued by only five of the largest companies. Four of them are registered in the USA and one is registered in Belgium.

星期一, 8月 03, 2020

GreatFire 应用生成器 发布

GreatFire (https://en.greatfire.org/) 是一家专注于中国的审查监督组织,我们自豪地宣布一个新的反审查工具,该工具将使任何被屏蔽的媒体、博客、人权组织或民间社会组织反制审查,将其内容得以传播到中国和其他互联网审查国家的数百万读者和支持者的手机上。

GreatFire 已经构建了一个名为“GreatFire 应用生成器”的网页程序,任何组织可以使用它来为中国和其他国家的用户解锁他们的内容。任何人可以访问 (https://appmaker.greatfire.org/),该网站将编译一个带有自己logo的应用,并将包含他们以前被封锁的内容。该应用还将包含一个特殊的、绕过审查的网络浏览器,以便用户可以访问未经审查的网络。这些应用将使用包括机器学习在内的多种策略来规避中国当局先进的审查策略。这个项目在其他有类似中国的审查限制的国家也同样有效。对于组织和最终用户而言,这些应用将免费、快速且非常易于使用。

这个项目的灵感来自于GreatFire自己的应用 自由浏览(https://freebrowser.org/en)的第一手经验,并希望帮助那些可能没有内部专业知识来规避中国审查制度的小型非政府组织。GreatFire的反审查工具在中国发挥了作用,而其他工具却没有。自由浏览可以引导中国的互联网用户从应用的首页进入被僧所内容的导航(http://manyvoices.news/)。

   

人权基金会 (HRF) 已经使用 GreatFire 应用生成器 创建了一个应用程序HRF 在全球范围内促进和保护人权。该组织的使命是确保自由在世界范围内得到维护和促进。 HRF 的网站 在中国被封锁, 但现在中国任何人都可以 下载 HRF Android 应用程序 并访问该网站的信息。

“现在是中国政府防火墙倒塌的时候了,”人权基金会战略顾问王珍妮说。 “与我们在 GreatFire 的朋友一起,我们致力于击败中国的审查制度——在每一部手机。”

GreatFire 应用生成器 的起源可以追溯到 2014 年,当时开放技术基金 (OTF) 支持 GreatFire 的“依附的自由”实验。该项目直接导致了 2015 年中国政府的大规模网络攻击,后来被称为“大炮”。 OTF 还为 GreatFire 开发 AppleCensorship.com,该网站正在跟踪苹果对包括香港在内的全球应用商店的审查情况。

自由浏览 是“大炮”攻击的直接结果,五年后,我们很高兴能够向任何可能遭受中国当局审查的组织提供我们的方法。 

星期五, 7月 24, 2020

Apple, anticompetition, and censorship

On July 20, 2020, GreatFire wrote to all 13 members of the Subcommittee on Antitrust, Commercial and Administrative Law of the U.S. House Committee on the Judiciary, requesting a thorough examination into Apple’s practice of censorship of its App Store, and an investigation into how the company collaborates with the Chinese authorities to maintain its unique position as one of the few foreign tech companies operating profitably in the Chinese digital market.  

This letter was sent a week before Apple CEO TIm Cook will be called for questioning in front of the Subcommittee on Antitrust, Commercial and Administrative Law. The CEOs of Amazon, Google and Facebook will also be questioned on July 27, as part of the Committee’s ongoing investigation into competition in the digital marketplace.

This hearing offers an opportunity to detail to the Subcommittee how Apple uses its closed operating ecosystem to not only abuse its market position but also to deprive certain users, most notably those in China, of their right to download and use apps related to privacy, secure communication, and censorship circumvention.

We hope that U.S. House representatives agree with our view that Apple should not be allowed to do elsewhere what would be considered as unacceptable in the U.S. Chinese citizens are not second class citizens. Private companies such as Apple compromise themselves and their self-proclaimed values of freedom and privacy when they collaborate with the Chinese government and its censors.

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Intetesting point on xunlei. It lacks origin integrity checking (normally a big part of p2p). The problem is Xcode dpwnloads take ages as Apple does not provide it from a cdn within China. Maybe Apple themselves need to look at such a peer-to-peer accelerator.

Intetesting point on xunlei. It lacks origin integrity checking (normally a big part of p2p). The problem is Xcode dpwnloads take ages as Apple does not provide it from a cdn within China. Maybe Apple themselves need to look at such a peer-to-peer accelerator.

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