Improving Platform Security with UEFI Secure Boot and UEFI ......Mar 18, 2016 · UEFI Secure Boot...
Transcript of Improving Platform Security with UEFI Secure Boot and UEFI ......Mar 18, 2016 · UEFI Secure Boot...
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Improving Platform Security with UEFI Secure Boot and UEFI
VariablesUEFI Spring Plugfest – March 29-31, 2016
Presented by David Chen (Insyde Software)
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Updated 2011-06-01
Agenda
• Introduction
• UEFI Variables
• New Secure Boot Model
• Call For Action
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Introduction
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Variables may be attacked
POST RT
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VarA
VarB
Current Secure Boot Model
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PKpub == NULL
SetupMode == 1
SecureBoot == 0
Setup Mode User Mode
PKpub != NULL
SetupMode == 0
SecureBoot == 1
1. Delete PKpub
2. Platform-Specific
PKpub Clear
Enroll PKpub
Secure Boot OffSecure Boot
Ready To Go
UEFI Variables
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Protect the Variables
• Set Variable without RT attribute
• Variable Lock
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BS+RT BS
Critical Variables
UEFI Secure Boot Database
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PK KEK
db
dbx
dbt
dbrUpdate
Enable
Update
Enable
Update
Enable
Update
Enable
Update
Enable
2.3.1 2.3.1
2.3.1
2.3.1
2.4
2.5
If signed by key in db,
driver/loader can Run!
If signed by key in dbx,
driver/loader forbidden!
If signed by key in dbt,
Check cert’s timestamp!
If signed by key in dbr,
loader can Run for
recovery!
Scenario to use dbtBefore UEFI Specification v2.4
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Images
(signed earlier)
Images
(signed later)
KeyPriv
Certification
dbx
If signed by key in dbr,
loader can Run for
recovery!
Scenario to use dbtAfter UEFI Specification v.2.4
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Images
(signed earlier)
Images
(signed later)
KeyPriv
Certification
dbt
UEFI VariablesSecure Boot Modes
SetupMode
AuditMode
DeployedModeUEFI Plugfest – March 2016 www.uefi.org 11
2.3.1
2.5
2.5
New Secure Boot Model
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Why Audit/Deployed Mode?
• Customers (ex: data center, government, etc.) have different requirement for secure boot database.
• But the Secure Boot Database isn’t easy to be customized with the old model!
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Audit Mode
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PKpub == NULL
AuditMode==0 (RW)
SetupMode == 1
SecureBoot == 0
Audit ModeUser Mode
PKpub != NULL
AuditMode==0 (RW)
SetupMode == 0
SecureBoot == 1
1. Delete PKpub
2. Platform-Specific
PKpub Clear
Enroll PKpub
PKpub == NULL
AuditMode==1 (RO)
SetupMode == 1
SecureBoot == 0
Log more info
to IEIT
Set AuditMode to1
Deployed Mode
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PKpub == NULL
AuditMode == 0 (RW)
DeployedMode==0 (RO)
SetupMode == 1
SecureBoot == 0
Setup Mode
User Mode
PKpub != NULL
AuditMode == 0 (RW)
DeployedMode==0 (RW)
SetupMode == 0
SecureBoot == 1
1. Delete PKpub
2. Platform-Specific
PKpub Clear
Enroll PKpub
PKpub == NULL
AuditMode == 1 (RO)
DeployedMode==0 (RO)
SetupMode == 1
SecureBoot == 0Set AuditMode to1
Audit Mode
Enroll PKpub
Deployed Mode
PKpub != NULL
AuditMode == 0 (RO)
DeployedMode==1 (RO)
SetupMode == 0
SecureBoot == 1
Set DeployedMode to1
Platform-Specific DeployedMode Clear
Call For Action
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Call For Action
• Critical variables need to be protected
• Customers need more flexible customized secure boot databases
• Update your spec to adopt new secure implementation to enhance your platform’s security
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Thanks for attending the UEFI Spring Plugfest 2016
For more information on the Unified EFI Forum and UEFI Specifications, visit http://www.uefi.org
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Backup
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UEFI VariablesSecure Boot Databases
• Platform Key (PK)• Key Exchange Key Database (KEK)• Secure Boot Signature Database (db)• Secure Boot Blacklist Signature Database
(dbx)• Secure Boot Timestamp Signature Database
(dbt)• Secure Boot Authorized Recovery Signature
Database (dbr)
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2.3.1
2.3.1
2.5
2.4
2.3.1
2.3.1