TLS Vulnerability in iOS Apps Opens the Door to Man-in-the-Middle Attacks

How many vulnerabilities do we have to uncover before keys and certificates get the attention they deserve? Despite their importance in securing the privacy of communications and commerce, keys and certificates are still largely overlooked by developers. The latest proof is a new suite of vulnerable iOS apps that were discovered by security researcher Will Strafach of Sudo. He ran a bulk scan of the App Store and found over 70 iOS apps that were vulnerable to silent interception due to sloppy use of Transport Layer Security (TLS) encryption. 

As reported in an article in Appleinsider, “The apps identified in the report are able to be fooled into providing readable data, with testing involving an iPhone running iOS 10 and a ‘malicious’ proxy that provided invalid TLS certificates.” This allows an attacker to use custom hardware or a modified mobile phone to read or manipulate data before it’s forwarded to a company’s servers. Even worse, the attacks are not limited to rogue Wi-Fi hotspots in public places. They can potentially be conducted anywhere within Wi-Fi range of the targeted device.

The ugly truth is that this vulnerability is not unique. And it’s certainly nothing new. But TLS security is still not top of mind for app developers. Venafi VP of security strategy, Kevin Bocek, laments, “Unfortunately, app developers and mobile platforms continue to open the door for adversaries to attack our privacy and threaten our personal safety. From Fandango to GM, apps fail to know which digital certificates are trusted for machines and cloud.” This inattention has resulted in the siphoning of credit card data and even the takeover of cards.

The irony of this situation is that TLS encryption is designed to improve the privacy of apps users. But if it’s implemented poorly, it can actually allow attackers to hide inside the very encryption that is intended to keep them out. Bocek notes that improperly applied certificates can undermine trust, “We’re learning that over 70 apps in Apple App Store fail to know which certificates should be trusted – enabling attackers to masquerade, steal data, and—as we saw with GM—perpetrate attacks in the real world that could cause harm.” 

The implications of this research extend beyond local Wi-Fi. Cyber criminals are not the only entities that can take advantage of this vulnerability. Internet Service Providers can also leverage this capability to snoop on mobile traffic. “This is especially alarming in countries like China, Russia, and elsewhere where the Internet architecture is designed for surveillance,” cautions Bocek.

Are you exposed to this vulnerability? Strafach has published a list of low-risk vulnerable apps and has notified the owners of medium and high-risk apps to remedy the situation. In the meantime, he recommends switching from Wi-Fi to cellular when using sensitive apps in public areas.

Ultimately, this type of vulnerability is unacceptable. As we turn to apps to conduct increasing amounts of communication and commerce, we need to be assured of the privacy of our sensitive data. Without that trust, the system will simply collapse. Bocek warns that this type of vulnerability can’t persist: “Every machine, cloud, and app relies on digital certificates to know what is trusted or not. In the era of IoT, drones, and autonomous vehicles, the global economy can’t be safe if we fail to protect digital certificates.”

If your organization is still a bit leery about trusting apps with sensitive data, there are new technologies which allow you to determine the reputation of a given certificate. Data gathered from Certificate Reputation queries will help you understand which certificates should be trusted and when.

How easily can you determine which certificates to trust in your organization?