Malicious Xcode could spread via download manager Xunlei

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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Mon, Aug 03, 2020

Announcing the Release of GreatFire Appmaker

GreatFire (https://en.greatfire.org/), a China-focused censorship monitoring organization, is proud to announce that we have developed and released a new anti-censorship tool that will enable any blocked media outlet, blogger, human rights group, or civil society organization to evade censors and get their content onto the phones of millions of readers and supporters in China and other countries that censor the Internet.

GreatFire has built an Android mobile app creator, called “GreatFire AppMaker”, that can be used by organizations to unblock their content for users in China and other countries. Organizations can visit a website (https://appmaker.greatfire.org/) which will compile an app that is branded with the organization’s own logo and will feature their own, formerly blocked content. The app will also contain a special, censorship-circumventing web browser so that users can access the uncensored World Wide Web. The apps will use multiple strategies, including machine learning, to evade advanced censorship tactics employed by the Chinese authorities.  This project will work equally well in other countries that have China-like censorship restrictions. For both organizations and end users, the apps will be free, fast, and extremely easy to use.

This project was inspired by China-based GreatFire’s first-hand experience with our own FreeBrowser app (https://freebrowser.org/en) and desire to help small NGOs who may not have the in-house expertise to circumvent Chinese censorship. GreatFire’s anti-censorship tools have worked in China when others do not. FreeBrowser directs Chinese internet users to normally censored stories from the app’s start page (http://manyvoices.news/).

Fri, Jul 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.

Mon, Jun 10, 2019

Apple Censoring Tibetan Information in China

Apple has a long history of censorship when it comes to information about Tibet. In 2009, it was revealed that several apps related to the Dalai Lama were not available in the China App Store. The developers of these apps were not notified that their apps were removed. When confronted with these instances of censorship, an Apple spokesperson simply said that the company “continues to comply with local laws”.

In December, 2017, at a conference in China, when asked about working with the Chinese authorities to censor the Apple App Store, Tim Cook proclaimed:

"Your choice is: do you participate, or do you stand on the sideline and yell at how things should be. And my own view very strongly is you show up and you participate, you get in the arena because nothing ever changes from the sideline."

In the ten years since Apple was first criticized for working with the Chinese authorities to silence already marginalized voices, what has changed? Apple continues to strictly follow the censorship orders of the Chinese authorities. When does Tim Cook expect that his company will help to bring about positive change in China?

Based on data generated from https://applecensorship.com, Apple has now censored 29 popular Tibetan mobile applications in the China App Store. Tibetan-themed apps dealing with news, religious study, tourism, and even games are being censored by Apple. A full list of the censored apps appear below.

Thu, Jun 06, 2019

Report Shines Spotlight on Apple’s Censorship Practices in China

The newest Ranking Digital Rights Corporate Accountability Index makes recommendations on what companies and governments need to do in order to improve the protection of internet users’ human rights around the world. Ranking Digital Rights (RDR) works to promote freedom of expression and privacy on the internet by creating global standards and incentives for companies to respect and protect users’ rights.

In their 2019 Accountability Index, RDR looks at the policies of 24 of the world’s most important internet companies in respect to freedom of expression and privacy and highlights the companies that have made improvements and those companies that need to do more. RDR notes that:

Insufficient transparency makes it easier for private parties, governments, and companies themselves to abuse their power over online speech and avoid accountability.

In particular, the report highlights how Apple has abused their power over online speech, and notes instances of this in China. According to the report, Apple has not disclosed data around the content that it removes from its App Store when faced with requests from the government authorities.

While [Apple] disclosed data about government requests to restrict accounts, it disclosed no data about content removal requests, such as requests to remove apps from its App Store. Apple revealed little about policies and practices affecting freedom of expression, scoring below all other U.S. companies in this category.

The report makes intelligent and sensible recommendations for governments. However, the recommendations also highlight how difficult it is to have these discussions with governments like China’s.

Thu, Nov 30, 2017

About those 674 apps that Apple censored in China

Apple opened the door on its censorship practices in China - but just a crack.
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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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