Connect with us

Hi, what are you looking for?

SecurityWeekSecurityWeek

Mobile & Wireless

Android 7.0 to Strictly Enforce Verified Boot

Google is planning new security features for the upcoming Android 7.0, including verified boot, which will prevent devices with a corrupt or modified boot image from booting.

Google is planning new security features for the upcoming Android 7.0, including verified boot, which will prevent devices with a corrupt or modified boot image from booting.

Android already has verified boot for cryptographic integrity checking to detect modifications to the operating system, but Android 7.0 will now require the feature to be strictly enforced, Sami Tolvanen, Software Engineer at Google, says. Thus, the device won’t boot if the boot image or verified partition is corrupt, or will boot with limited capacity with user consent, Tolvanen says.

“Such strict checking, though, means that non-malicious data corruption, which previously would be less visible, could now start affecting process functionality more,” the engineer explains.

Android uses the dm-verity kernel driver to verify large partitions and does so by dividing the partition into 4 KiB blocks, which are checked against a signed hash tree. Should a single byte be corrupted, the entire block becomes inaccessible when dm-verity is in enforcing mode, and the kernel returns EIO errors to userspace on verified partition data access.

Android 7.0, however, comes with improved dm-verity robustness, courtesy of forward error correction (FEC), and is also more resistant to data corruption. FEC allows for the detection and correction of errors in source data, Google’s engineer explains. In the upcoming Android release, dm-verity uses interleaving to recover from a loss of several 4 KiB source blocks, Tolvanen says.  

Combined with the integrity verification performed by dm-verity, interleaving makes it possible to detect exactly where the errors are in each code. Thus, since each byte of the code covers a different source block, the integrity of each block can be verified using the existing dm-verity metadata, revealing which of the bytes contain errors.

The downside of interleaving is that the decoding is slower, mainly because it isn’t used for reading a single block, but multiple blocks spread across the partition. However, Tolvanen notes that this is not an issue when dm-verity and solid-state storage are considered, because the system only needs to decode if a block is actually corrupted, which rarely happens.

Advertisement. Scroll to continue reading.

“Strictly enforced verified boot improves security, but can also reduce reliability by increasing the impact of disk corruption that may occur on devices due to software bugs or hardware issues,” Google’s engineer notes.

Courtesy of this new error correction feature for dm-verity, however, devices should be able to recover from the loss of up to 16-24 MiB of consecutive blocks anywhere on a typical 2-3 GiB system partition, Tolvanen says. The recovery needs only 0.8% space overhead and has no impact on performance, unless corruption is detected.

 While the security enhancement is meant for all devices running Android 7.0, the overwhelming majority of devices don’t have the latest security patches installed. Running over 400 million Android security scans daily, Google last month announced that it would pay up to $50,000 in bug bounties to researchers who discover vulnerabilities in TrustZone or Verified Boot.

Last year, Google requested manufacturers to enable full-disk encryption out-of-the-box for new Android 6.0 devices.

Written By

Click to comment

Daily Briefing Newsletter

Subscribe to the SecurityWeek Email Briefing to stay informed on the latest threats, trends, and technology, along with insightful columns from industry experts.

SecurityWeek’s Threat Detection and Incident Response Summit brings together security practitioners from around the world to share war stories on breaches, APT attacks and threat intelligence.

Register

Securityweek’s CISO Forum will address issues and challenges that are top of mind for today’s security leaders and what the future looks like as chief defenders of the enterprise.

Register

Expert Insights

Related Content

Mobile & Wireless

Infonetics Research has shared excerpts from its Mobile Device Security Client Software market size and forecasts report, which tracks enterprise and consumer security client...

Mobile & Wireless

Apple rolled out iOS 16.3 and macOS Ventura 13.2 to cover serious security vulnerabilities.

Mobile & Wireless

Critical security flaws expose Samsung’s Exynos modems to “Internet-to-baseband remote code execution” attacks with no user interaction. Project Zero says an attacker only needs...

Mobile & Wireless

Technical details published for an Arm Mali GPU flaw leading to arbitrary kernel code execution and root on Pixel 6.

Mobile & Wireless

Two vulnerabilities in Samsung’s Galaxy Store that could be exploited to install applications or execute JavaScript code by launching a web page.

Mobile & Wireless

The February 2023 security updates for Android patch 40 vulnerabilities, including multiple high-severity escalation of privilege bugs.

Mobile & Wireless

Apple’s iOS 12.5.7 update patches CVE-2022-42856, an actively exploited vulnerability, in old iPhones and iPads.

Cybercrime

A digital ad fraud scheme dubbed "VastFlux" spoofed over 1,700 apps and peaked at 12 billion ad requests per day before being shut down.