Compliant Product - Google Pixel Phones on Android 11.0
Certificate Date: 2021.02.08CC Certificate Security Target Validation Report
Validation Report Number: CCEVS-VR-VID11124-2021
Product Type: Mobility
Conformance Claim: Protection Profile Compliant
PP Identifier: Protection Profile for Mobile Device Fundamentals Version 3.1
Extended Package for Wireless LAN Client Version 1.0
CC Testing Lab: Gossamer Security Solutions
The Target of Evaluation (TOE) is Google Pixel Phones on Android 11.0. The TOE allows basic telephony features (make and receive phone calls, send and receive SMS/MMS messages) as well as advanced network connectivity (allowing connections to both 802.11 Wi-Fi and 2G/3G/4G LTE/5 mobile data networks). The TOE supports using client certificates to connect to access points offering WPA2/WPA3 networks with 802.1x/EAP-TLS, or alternatively connecting to cellular base stations when utilizing mobile data.
The TOE provides a rich API to mobile applications and provides users installing an application the option to either approve or reject an application based upon the API access that the application requires (or to grant applications access at runtime).
The TOE also provides users with the ability to protect Data-At-Rest with AES encryption, including all user and mobile application data stored in the user’s data partition. The TOE uses a key hierarchy that combines a REK with the user’s password to provide protection to all user and application cryptographic keys stored in the TOE.
The TOE includes an additional hardware security chip (Titan M) that provides dedicated key storage. The TOE makes this secure, hardware key storage available to mobile applications through the StrongBox extensions to Android’s KeyStore. Currently, the StrongBox extension is not used for any system keys, but remains an option for applications to use should they desire the protections it provides.
Finally, the TOE can interact with a Mobile Device Management (MDM) system (not part of this evaluation) to allow enterprise control of the configuration and operation of the device so as to ensure adherence to enterprise-wide policies (for example, restricting use of a corporate provided device’s camera, forced configuration of maximum login attempts, pulling of audit logs off the TOE, etc.) as well as policies governing enterprise applications and data (in a an employee-owned device [BYOD] scenario). An MDM is made up of two parts: the MDM agent and MDM server. The MDM Agent is installed on the phone as an administrator with elevated permissions (allowing it to change the relevant settings on the phone) while the MDM Server is used to issue the commands to the MDM Agent. Neither portion of the MDM process is considered part of the TOE, and therefore not being directly evaluated.
The TOE includes several different levels of execution including (from lowest to highest): hardware, a Trusted Execution Environment, Android’s bootloader, and Android’s user space, which provides APIs allowing applications to leverage the cryptographic functionality of the device.
Security Evaluation Summary
The evaluation was carried out in accordance to the Common Criteria Evaluation and Validation Scheme (CCEVS) requirements and guidance. The criteria against which the TOE was judged are described in the Common Criteria for Information Technology Security Evaluation, Version 3.1, Revision 5, September 2017. The evaluation methodology used by the evaluation team to conduct the evaluation is the Common Methodology for Information Technology Security Evaluation, Evaluation Methodology, Version 3.1, Revision 5, July 2017. The product, when delivered and configured as identified in the Google Pixel Phones on Android 11 Administrator Guidance Documentation, Version 1.3, 02/04/2021 document, satisfies all of the security functional requirements stated in the Google Pixel Phones on Android 11.0 (MDFPP31/WLANCEP10) Security Target, Version 1.6, 02/04/2021. The project underwent CCEVS Validator review. The evaluation was completed in February 2021. Results of the evaluation can be found in the Common Criteria Evaluation and Validation Scheme Validation Report prepared by CCEVS.
The logical boundaries of the TOE are realized in the security functions that it implements. Each of these security functions is summarized below.
The TOE implements a security log and logcat that are each stored in a circular memory buffer. An MDM agent can read/fetch the security logs, can retrieve logcat logs, and then handle appropriately (potentially storing the log to Flash or transmitting its contents to the MDM server). These log methods meet the logging requirements outlined by FAU_GEN.1 in MDFPPv3.1.
The TOE includes multiple cryptographic libraries with CAVP certified algorithms for a wide range of cryptographic functions including the following: asymmetric key generation and establishment, symmetric key generation, encryption/decryption, cryptographic hashing and keyed-hash message authentication. These functions are supported with suitable random bit generation, key derivation, salt generation, initialization vector generation, secure key storage, and key and protected data destruction. These primitive cryptographic functions are used to implement security protocols such as TLS, EAP-TLS, and HTTPS and to encrypt the media (including the generation and protection of data and key encryption keys) used by the TOE. Many of these cryptographic functions are also accessible as services to applications running on the TOE allowing application developers to ensure their application meets the required criteria to remain compliant to MDFPP standards.
User data protection:
The TOE controls access to system services by hosted applications, including protection of the Trust Anchor Database. Additionally, the TOE protects user and other sensitive data using encryption so that even if a device is physically lost, the data remains protected. The TOE’s evaluated configuration supports Android Enterprise profiles to provide additional separation between application and application data belonging to the Enterprise profile. Please see the Admin Guide for additional details regarding how to set up and use Enterprise profiles.
Identification and authentication:
The TOE supports a number of features related to identification and authentication. From a user perspective, except for FCC mandated (making phone calls to an emergency number) or non-sensitive functions (e.g., choosing the keyboard input method or taking screen shots), a password (i.e., Password Authentication Factor) must be correctly entered to unlock the TOE. Also, even when unlocked, the TOE requires the user re-enter the password to change the password. Passwords are obscured when entered so they cannot be read from the TOE's display and the frequency of entering passwords is limited and when a configured number of failures occurs, the TOE will be wiped to protect its contents. Passwords can be constructed using upper and lower cases characters, numbers, and special characters and passwords up to 16 characters are supported.
The TOE can also serve as an 802.1X supplicant and can both use and validate X.509v3 certificates for EAP-TLS, TLS, and HTTPS exchanges.
The TOE provides all the interfaces necessary to manage the security functions identified throughout this Security Target as well as other functions commonly found in mobile devices. Many of the available functions are available to users of the TOE while many are restricted to administrators operating through a Mobile Device Management solution once the TOE has been enrolled. Once the TOE has been enrolled and then un-enrolled, it will remove Enterprise applications and remove MDM policies.
Protection of the TSF:
The TOE implements a number of features to protect itself to ensure the reliability and integrity of its security features. It protects particularly sensitive data such as cryptographic keys so that they are not accessible or exportable through the use of the application processor’s hardware. The TOE disallows all read access to the Root Encryption Key and retains all keys derived from the REK within its Trusted Execution Environment (TEE). Application software can only use keys derived from the REK by reference and receive the result.
The TOE also provides its own timing mechanism to ensure that reliable time information is available (e.g., for log accountability). It enforces read, write, and execute memory page protections, uses address space layout randomization, and stack-based buffer overflow protections to minimize the potential to exploit application flaws. It also protects itself from modification by applications as well as to isolate the address spaces of applications from one another to protect those applications.
The TOE includes functions to perform self-tests and software/firmware integrity checking so that it might detect when it is failing or may be corrupt. If any self-tests fail, the TOE will not go into an operational mode. It also includes mechanisms (i.e., verification of the digital signature of each new image) so that the TOE itself can be updated while ensuring that the updates will not introduce malicious or other unexpected changes in the TOE. Digital signature checking also extends to verifying applications prior to their installation as all applications must have signatures (even if self-signed).
The TOE can be locked, obscuring its display, by the user or after a configured interval of inactivity. The TOE also has the capability to display an administrator specified (using the TOE’s MDM API) advisory message (banner) when the user unlocks the TOE for the first use after reboot.
The TOE is also able to attempt to connect to wireless networks as configured.
The TOE supports the use of IEEE 802.11-2012, 802.1X, and EAP-TLS and TLS, HTTPS to secure communications channels between itself and other trusted network devices.
The Target of Evaluation (TOE) consists of the Pixel 5, 4a, 4, 3a, and 3 phones. Google manufacturers some of the phones in two variants, differing in size (normal and large/“XL”) or build materials (entry and premium).
The evaluated configuration consists of the following models and versions: