Building a Product with OP-TEE Possible pitfalls while deploying - - PowerPoint PPT Presentation

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Building a Product with OP-TEE Possible pitfalls while deploying - - PowerPoint PPT Presentation

Oct 06, 2022 792 likes •1.01k views

Building a Product with OP-TEE Possible pitfalls while deploying OP-TEE in production Rouven Czerwinski r.czerwinski@pengutronix.de https://www.pengutronix.de About me Rouven Czerwinski Pengutronix e.K. Emantor rcz@pengutronix.de

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SLIDE 1

https://www.pengutronix.de

Building a Product with OP-TEE

Possible pitfalls while deploying OP-TEE in production Rouven Czerwinski– r.czerwinski@pengutronix.de

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2/21

About me

Rouven Czerwinski Pengutronix e.K.  Emantor  rcz@pengutronix.de

 OP-TEE 

System Integration

 T

esting

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T able of Contents

Short overview:

 Introduction  Motivation  Problems  Solutions  Conclusion  Outlook

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SLIDE 4

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TrustZone (32-bit)

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SLIDE 5

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Introduction

 Open Portable T

rusted Execution Environment (OP-TEE)

 Open source (BSD-2 clause)

implementation of the GP TEE specifjcation using T rustZone

 Support for various ARM platforms

(STM32, TI, Layerscape, broadcom,…)

 My focus is on i.MX6 platforms

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SLIDE 6

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Motivation

 Secure the OP-TEE and TAs for production

use

 Ensure that upstream OP-TEE can be used

securely on i.MX6

 Provide guidance which parts may be

missing for other platforms (TI, STM, Layerscape,…)

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Problem

 Which components do I need to secure

OP-TEE?

 Which part of the confjguration is already

upstream?

 Which part needs to be managed by

system integrator?

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Securing upstream OP-TEE

 RAM protection/Pager  Hardware Unique Key (HUK)  RNG Seeding  Peripheral Access Confjguration  Ensure trusted OP-TEE bootup  Optional: storage rollback protection

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RAM protection

 Confjgure the DDR fjrewall  Protects part of RAM for secure world  i.e. TZC380 with multiple regions  For i.MX6:

 TZC380 from ARM  Upstream driver already within OP-TEE

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i.MX6 TZC380 autoconfjguration

 TZC380 auto confjguration upstream  Correctly confjgures TZC380 for generic

RAM devices with known memory layout

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OP-TEE Pager

 Run small part of OP-TEE in SRAM  Encrypt other memory pages live in DRAM  Does not require a DDR fjrewall  For i.MX6:

 Chosen i.MX6UL may not have enough SRAM  Bigger variants may use SRAM for other use

cases (IPU, GPU,…)

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SLIDE 12

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Hardware Unique Key (HUK)

 Used to derive other keys for OP-TEE  Should be unique per device  Should not be accessible from normal

world

 For i.MX6:

 Use CAAM Master Key Verifjcation Blob

(MKVB) and lockout generation afterwards

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i.MX6 HUK generation

 Needs rebase on i.MX6/7 CAAM driver  Will be done soon™

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RNG seeding

 OP-TEE uses FORTUNA PRNG  Requires RNG seed  Default seed for dev is zero  For i.MX6:

 Retrieve RNG from CAAM TRNG on bootup  Not implemented yet

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Peripheral Access Confjguration

 SoCs have DMA masters beside CPU  Those masters may be default secure and

can access secure world memory

 For i.MX6:

 Access policies confjgurable via Central

Security Unit (CSU)

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i.MX6 CSU

 Upstream confjgures correctly for i.MX6UL  Other i.MX6/7 SoCs trivial to add (given

Security Reference Manual)

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Trusted Bootup

 Use platform verifjed/secure boot  Verifjes OP-TEE version to prevent

replacements

 For i.MX6:

 Implement High Assurance Boot (HAB), also

required for HUK

 Not implementable upstream, needs to be

handled by integrator

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Storage Rollback protection

 T

  • protect from rollback attacks, employ

eMMC RPMB FS

 Simple FAT fjlesystem  For all platforms:

 Enable with CFG_RPMB_FS=1  Deploy during manufacturing with

CFG_RPMB_WRITE_KEY=1

 Ensure to disable emulation in TEE Supplicant

with RPMB_EMU=0

 Support upstream

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Conclusion

 No platform is currently ready to deploy

OP-TEE in production

 i.MX6 is slowly getting there

 Vendor implementations may include the

necessary bits

 Still requires code review and cross reference

to platform manual

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Outlook (Wishlist)

 Clock and access coordination between

OP-TEE and Linux

 Deeper device tree integration for OP-TEE  CI infrastructure to test each commit to

OP-TEE master for i.MX6/7

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SLIDE 21

https://www.pengutronix.de

Thank you

Questions?