Lcu14 306 - OP-TEE Future Enhancements --------------------------------------------------- Speaker: Joakim Bech, Jens Wiklander and Pascal Brand Date: September 17, 2014 --------------------------------------------------- ★ Session Summary ★ In this discussion session, we will cover the plans Linaro have to enhance the current OP-TEE implementation. Different topics will be covered, among them: Adding a cryptographic layer to support custom cryptographic libraries or HW-acceleration IP / instructions (REQ-413 and REQ-421) PSCI support (REQ-415) Add ECC support for TEE Internal API 1.1 (REQ-419) --------------------------------------------------- ★ Resources ★ Zerista: http://lcu14.zerista.com/event/member/137753 Google Event: https://plus.google.com/u/0/events/cq01taemqeeblb8k8jnu21lifus Video: https://www.youtube.com/watch?v=GTKEmdUU1lE&list=UUIVqQKxCyQLJS6xvSmfndLA Etherpad: http://pad.linaro.org/p/lcu14-306 --------------------------------------------------- ★ Event Details ★ Linaro Connect USA - #LCU14 September 15-19th, 2014 Hyatt Regency San Francisco Airport --------------------------------------------------- http://www.linaro.org http://connect.linaro.org

1. LCU14-306: OP-TEE Future Enhancements
Joakim Bech, Jens Wiklander and Pascal Brand, LCU14
LCU14 BURLINGAME

2. Cryptographic Layer in OP-TEE
● Aim and problem
● Interaction between TA and Cryptographic Services
● Does not define how the services are implemented / data structures
● Current Status
● LibTomCrypt is the cryptographic library in OP-TEE
● End user may want to switch to ...
- OpenSSL
- Using ARMv8-A cryptographic extensions
- Dedicated cryptographic IP
● Enhancement
● Define a low level API to easily switch from one implementation to another one.

3. GlobalPlatform Internal Core API 1.1
● Current Status
● Internal API 1.0 is supported
● Enhancement
● Add support for GP Internal API 1.1 released in June 2014
● Main updates are:
- Elliptic Curve Digital Signature Algorithm (ECDSA)
- Elliptic Curve Cryptography Cofactor Diffie-Hellman (ECDH)
- Some errata with new error cause
- Few deprecated features (object)

4. Secure Storage
● Current Status
● File storage is implemented (using a daemon running normal world)
● Data isn’t encrypted by default
● No persistent storage
● Enhancement
● Making Secure Storage … more secure
● Enable encryption by default
● Key provisioning
● Streaming to be taken into account
● Replay Protected Memory Block (RPMB) support
Secure World
Trusted
Application
Normal World
TEE supplicant
Linux kernel Trusted OS
Secure monitor
RPMB

5. Secure Time
● Aim and problem
● GlobalPlatform TEE Internal API defines support of the Clock
● Secure clock will be needed in DRM use cases
● Secure IP usage is specific to a given platform
● Current Status
● Only based on REE using RPC NOT Secure!
● Enhancement
● Enable clocks from both REE and Secure IP
● Create a Time API to access the Secure IP
● Fulfill TEE Internal API 1.1 requirements of maximum 15% deviation from real time

6. Reduce Memory Footprint
● Aim and problem
● Memory footprint of the Trusted OS part is critical
● OP-TEE enables all GlobalPlatform features by default
● Enhancement
● Make it possible to select functionality at compile time
● All cryptographic algorithms are probably not needed …
● Some functionality may not be needed (Big Number arithmetic, ...)

7. Multiple TA Support
● Aim
● Enable multiple TA functions to be called at the same time
● Current Status
● Threading model of the Trusted OS is ready, but not activated
● Enhancement
● Will enable multiple-TA’s running in parallel

8. Paging
● Aim
● Trusted OS may run on embedded memory which is small
● Enhancement
● Paging the Trusted OS would solve memory constraint
● some parts would never be paged out (mmu management,...)
● some parts could be paged in DDR (secured or encrypted)

9. PSCI - Power State Coordination Interface
● Aim
● Make OP-TEE aware of PSCI functions.
● Current Status
● OP-TEE aware of: CPU_ON, CPU_OFF,
CPU_SUSPEND and CPU_RESUME (as stubbed functions)
● ARM-Trusted-Firmware handles
● Implemented: PSCI_VERSION, AFFINITY_INFO
● Not implemented: MIGRATE, MIGRATE_INFO_TYPE,
MIGRATE_INFO_UP_CPU, SYSTEM_OFF and SYSTEM_RESET

10. ASLR - Address Space Layout Randomization
● Aim and problem
● Already exists in normal world (user space and kernel)
● To avoid attack like return-to-libc-attack for example
● Make it random enough!
● Enhancement
● This feature could be part of Trusted OS
● Current limitations
● We use pre-defined virtual addresses
● Trusted Applications are currently statically linked

11. Other Potential Enhancements
● GlobalPlatform Trusted UI 1.1
● API to display content and capture input
in a secure manner.
● User-mode TEE
● For early Trusted Applications development and debug
● Avoid the need for having a full TrustZone platform
● Support for OP-TEE in QEMU
● Virtualization team have patches enabling
TrustZone functionality

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Linaro members: www.linaro.org/members
More about Linaro: www.linaro.org/about/