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Apr 24, 2018

Why You Don't Need Google's Domain Fronting

Google’s removal of domain fronting emphasizes the need for solutions like Psiphon.

Google has confirmed that they will block domain fronting across Google domains and App Engine. For many apps and publishers, this represents a step backwards in the fight for internet freedom. While Psiphon has never relied on this Google service, many app developers continued to depend on the practice as a convenient and straightforward means of circumventing state-level censorship, despite the long-running speculation that Google would close this loophole (eg. Will Scott’s blog post in 2017).

While the announcement has been met with criticism from internet activists and service providers alike, Google has defended their decision, saying “domain fronting has never been a supported feature”.

Domain fronting has been a popular means of censorship circumvention for several years, being embraced by popular apps like Signal, who publicly adopted the practice in 2016. While using Google domains to front traffic does not require advanced technical knowledge, it is a half measure that relies on Google, without consultation, to provide infrastructure for something it was not designed to do. In short, using the Google App Engine for domain fronting meant taking advantage of an unsupported loophole. For this reason, the practice would inevitably face restrictions as it gained popularity.

In 2015, Cloudflare also ended domain fronting across its domains when it began matching the SNI and host header of web traffic, after its infrastructure was implicated in censorship circumvention.

Most recently, in a frenzied attempt to block Telegram, which has made use of this loophole, Russian censorship authority Roskomnadzor blocked an estimated 17 million IP addresses. The interference disrupted access to Gmail, Google search, Google Play, YouTube, and other Google services.

Domain fronting is hardly the preeminent censorship circumvention solution. In cases where Google itself is blocked, as it is in Iran, any site or application that used Google for domain fronting would be unavailable as well. Psiphon’s network relies on a wide variety of protocols and obfuscation techniques to deliver Internet freedom. The complex and ever-changing nature of our network protects against over-reliance on one technology or approach.

The importance of a diversified circumvention toolbox cannot be overstated - for apps like Signal, reliance on Google domain fronting resulted in the need for an immediate and complete shift to another CDN. Tools like Psiphon seek to mitigate this risk by implementing numerous protocols, thereby eliminating reliance on any one method. Both Telegram and Tor’s use of multiple domain fronts minimized the disturbance caused to their services.

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