SANS Penetration Testing

iOS 10 is Apple's Gift to Android Users

How the latest update to iOS 10 will dramatically improve Android security

At the Apple WWDC conference in June, Ivan Krstic, Apple Head of Security Engineering & Architecture, made a bold declaration:

"At the end of 2016, Apple will make ATS mandatory for all developers who hope to submit their apps to the App Store."

ATS is App Transport Security, Apple's security feature that requires the use of TLS/1.2 encryption for all network transport data (specifically, the libraries used for interacting with web servers, NSURLSession and NSURLConnection). Apple introduced ATS in iOS 9, but offered developers the ability to work with servers on insecure domains by specifying exceptions in the application Info.plist file.

According to Krstic and Lucia Ballard, Apple's Secure Transports Engineering Manager, the enhancements to ATS will no longer accommodate the exceptions previously available for insecure domains. Further, ATS will now require TLS/1.2 with AES-128 and SHA2 hashing, while introducing support for ECDHE forward secrecy (to prevent a private key compromise from decrypting passively collected traffic), OCSP stapling (to mitigate information leaks from CRL checking), and certificate transparency (to defeat compromised CA attacks). The ATS changes will dramatically improve network transport security of iOS apps. This bears repeating:

ATS changes will dramatically improve the network transport security of iOS apps

Of course, transitioning from plain-old HTTP to TLS/1.2 is no simple affair, particularly for large application vendors. For a quick test, I downloaded a list of the top 20 iOS apps (on 6/32, this was before the Pokémon Go debut):

Top 20 Free iOS Apps, 6/23/2016

For each app, I took a packet capture while using the application using the rvictl utility, then evaluated the packet capture with Wireshark using the http display filter. From this top 20 list, only 7 were exclusively using HTTPS encryption for network transport, bringing shame to the remaining 13 for continuing to use HTTP.

Top Free iOS Apps using HTTP, 6/23/2016

Looking at the network traffic, I see this pattern often:

Instagram Network Traffic in Wireshark

CDN, CDN, CDN

Whether hosted on AWS or other cloud services, or traditional Content Distribution Networks (CDNs) such as Akamai or MaxCDN, big and little app developers alike will need to change their apps and infrastructure alike to meet the ATS requirement in iOS 10. The use of CDN is not iOS-specific, with many platforms sharing the same infrastructure for iOS, Android, and web applications.

With this change for iOS 10 users, Apple forces developers to migrate their platforms to TLS. Instagram, WhatsApp, Spotify, and other companies will accommodate this change to continue to serve the iOS market. In doing so, Android apps will also reap the benefits from this transition, even if Google continues to maintain a position of stubborn passivity in encouraging developers to do the right thing.

Apple's you-must-TLS decision is not without its drawbacks. Migrating an HTTP infrastructure to TLS is not free, and companies must find a way to pay for this added overhead. Further, TLS has distinct disadvantages for end-users: more network overhead, slower network responsiveness, and reduced battery life due to increased CPU overhead.

For end-users, an app update to Kik that causes their battery to die at 3:00 pm (instead of the 4:30 pm, these are iPhones we're talking about) will be met with derision, cries of outrage, and 1-star ratings. Regardless, TLS/1.2 is something Apple will require of iOS app developers. Why? Because HTTP must die.

HTTP MUST DIE

It's long past time when we need to protect mobile device users from the deficiencies in HTTP. Just like I tell my kids when they don't like the taste of medicine, sometimes we have to do things that we don't like because they are good for us.

For Android users, you've been given a gift with iOS 10 and ATS enhancements: it will naturally lead Android app developers to migrate to TLS and strong network transport security for your apps as well. It's a much-needed positive change for mobile security. Thank you, Apple.

-Joshua Wright
SANS Instructor and Course Author

SANS Note: Joshua Wright is the course author of SANS SEC575: Mobile Device Security and Ethical Hacking. This course is offered in-person numerous times each year and always available 24/7 in an online format - OnDemand.

 

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1 Comments

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