Time Protection: The Missing OS Abstraction Qian Ge, Yuval Yarom, - - PowerPoint PPT Presentation

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Time Protection: The Missing OS Abstraction Qian Ge, Yuval Yarom, - - PowerPoint PPT Presentation

Dec 16, 2023 659 likes •1.08k views

Time Protection: The Missing OS Abstraction Qian Ge, Yuval Yarom, Tom Chothia, Gernot Heiser qian.ge@data61.csiro.au www.data61.csiro.au Top secret Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au 2 Enforcing time

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www.data61.csiro.au

Time Protection: The Missing OS Abstraction

Qian Ge, Yuval Yarom, Tom Chothia, Gernot Heiser

qian.ge@data61.csiro.au

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

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Top secret

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Enforcing time protection at the OS level

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Security Domain Security Domain

Sending information through timing

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Enforcing time protection at the OS level

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Security Domain Security Domain

Sending information through timing

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Enforcing time protection at the OS level

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Security Domain Security Domain

Sending information through timing

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Microarchitectural Timing Channels

Shared hardware caches

Security Domain Security Domain

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Microarchitectural Timing Channels

Shared hardware caches

Security Domain Security Domain

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Welcome to Dresden

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Microarchitectural Timing Channels

Shared hardware caches

Security Domain Security Domain

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Welcome to Dresden

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Microarchitectural Timing Channels

Shared hardware caches

Security Domain Security Domain

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Welcome to Dresden

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Microarchitectural Timing Channels

Shared hardware caches

Security Domain Security Domain

Fast Fast Slow Fast Fast ….. S F S FFF SSSS F

Not English, but our protocol…

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Welcome to Dresden

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Contention, Contention, Contention…

…

Shared hardware caches

  • Contention leaks information via

timing

  • Caches:
  • capacity-limited
  • stateful
  • Resulting on temporal

interference during:

  • time-shared access
  • concurrent access

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Contention, Contention, Contention…

…

Shared hardware caches

  • Contention leaks information via

timing

  • Caches:
  • capacity-limited
  • stateful
  • Resulting on temporal

interference during:

  • time-shared access
  • concurrent access

Any state-holding microarchitectural feature:

  • Caches, branch predictor, TLB

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Preventing Contention by Partitioning

Security Domain Security Domain

Partitioned caches

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Spatial Partitioning

Cache RAM

Cache Memory

Cache colouring:

  • Distributing coloured cache sets

to coloured memory frames

  • Memory management policy

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Spatial Partitioning

Cache RAM

Cache Memory

Cache colouring:

  • Distributing coloured cache sets

to coloured memory frames

  • Memory management policy

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…

Shared hardware caches

Partition security domains on disjoint cache sets

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Spatial Partitioning

Cache RAM

Cache Memory

Cache colouring:

  • Distributing coloured cache sets

to coloured memory frames

  • Memory management policy
  • Resulting on temporal

interference during:

  • time-shared access
  • concurrent access

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…

Shared hardware caches

Partition security domains on disjoint cache sets

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Spatial Partitioning

Cache RAM

Cache Memory

Cache colouring:

  • Distributing coloured cache sets

to coloured memory frames

  • Memory management policy
  • Resulting on temporal

interference during:

  • time-shared access
  • concurrent access

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…

Shared hardware caches

Partition security domains on disjoint cache sets

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Spatial Partitioning

Cache RAM

Cache Memory

Cache colouring:

  • Distributing coloured cache sets

to coloured memory frames

  • Memory management policy
  • Resulting on temporal

interference during:

  • time-shared access
  • concurrent access

Cannot be supported by on-core caches

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…

Shared hardware caches

Partition security domains on disjoint cache sets

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Temporal Partitioning

Flushing on-core caches:

  • Resetting states

…

Shared on-caches

Context switch

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Temporal Partitioning

Flushing on-core caches:

  • Resetting states
  • Resulting on temporal

interference during:

  • time-shared access
  • concurrent access

…

Shared on-caches

Context switch

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Temporal Partitioning

Flushing on-core caches:

  • Resetting states
  • Resulting on temporal

interference during:

  • time-shared access
  • concurrent access

…

Shared on-caches

Context switch

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Preventing Temporal Interference through Partitioning

…

Spatial partitioning

Security Domain Security Domain

…

Context

Temporal partitioning

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Wait, Everyone Shares the Kernel….

Security Domain Security Domain

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…

Shared hardware caches

Kernel Services

A shared partition

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Wait, Everyone Shares the Kernel….

Security Domain Security Domain

Cache lines used by the kernel collide with Spy’s partition

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…

Shared hardware caches

Kernel Services

A shared partition

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Wait, Everyone Shares the Kernel….

Security Domain Security Domain

Cache lines used by the kernel collide with Spy’s partition

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…

Shared hardware caches

Kernel Services

A shared partition

Poster Session @ 17:15

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Wait, Everyone Shares the Kernel….

Security Domain Security Domain

Cache lines used by the kernel collide with Spy’s partition

Fast Fast Slow Fast Fast ….. S F S FFF SSSS F

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…

Shared hardware caches

Kernel Services

A shared partition

Poster Session @ 17:15

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Kernel Services

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Cloning the Kernel Image

.text .rodata .data

Analysing the kernel sections

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Cloning the Kernel Image

.text .rodata .data

Analysing the kernel sections

.text .rodata .data

Global (9KiB)

Maintaining coherency Duplicated sections

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Cloning the Kernel Image

.text .rodata .data

Analysing the kernel sections

.text .rodata .data

Global (9KiB)

Maintaining coherency Duplicated sections

Kernel Clone: Generating a copy of the kernel image with user-level managed memory

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Cloning the Kernel Image

.text .rodata .data

Analysing the kernel sections

.text .rodata .data

Global (9KiB)

Maintaining coherency Duplicated sections

Kernel Clone: Generating a copy of the kernel image with user-level managed memory

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Dedicated Kernel Images

…

Spatial partitioning

Security Domain Security Domain

…

Context

Temporal partitioning

Shared Global Data

Deterministic usage

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Timing Channel through the Shared Kernel

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Raw channel

seL4 system call

Input (taking seL4 syscall)

Channel matrix: conditional probability

  • f observing the output signal (time,

spy) given the input signal (system-call number, Trojan) Horizontal variation indicates a channel

Output (cycles)

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Timing Channel through the Shared Kernel

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Raw channel

seL4 system call

Input (taking seL4 syscall)

Channel matrix: conditional probability

  • f observing the output signal (time,

spy) given the input signal (system-call number, Trojan) Horizontal variation indicates a channel

Output (cycles)

Prevented by cloned kernel

Input (taking seL4 syscall) Output (cycles)

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

How realistic is cloning?

x86 Arm 224 KiB 120 KiB

Memory consumption

Arch seL4 Clone Linux fork + exec x86 79 μs 257 μs Arm 608 μs 4,300 μs

Efficiency

.text .rodata .data

Global (9KiB)

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Performance Impact

  • 1%

0% 1% 2% 3% 4% 5% 6% 7% b a r n e s c h

  • l

e s k y f f t f m m l u

  • c

e a n r a d i

  • s

i t y r a d i x r a y t r a c e w a t e r n s q u a r e d w a t e r s p a t i a l M E A N Slowdown 50% colours base 50% colour clone

The slowdown of splash-2 against base line kernel

The cost of colouring a domain:

  • 50% of the cache colour
  • 50% of the cache colour + a coloured kernel

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Performance Impact

x86 Arm 3.38% 1.09%

The geometric mean

The cost of time protection:

  • spatial partition + temporal

partition

  • 1%

0% 1% 2% 3% 4% 5% 6% 7% b a r n e s c h

  • l

e s k y f f t f m m l u

  • c

e a n r a d i

  • s

i t y r a d i x r a y t r a c e w a t e r n s q u a r e d w a t e r s p a t i a l M E A N Slowdown 50% colours base 50% colour clone

The slowdown of splash-2 against base line kernel

The cost of colouring a domain:

  • 50% of the cache colour
  • 50% of the cache colour + a coloured kernel

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

We have also done:

  • Partition IRQs
  • Domain-switch actions
  • A deterministic domain switching latency
  • Preventing timing channels:
  • Shared kernel, Intra-core, cross-core, domain-switch latency, timer
  • Performance evaluation:
  • IPC, domain switching latency, kernel cloning, cache colouring, time protection

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Time Protection: The Missing OS Abstraction qian.ge@data61.csiro.au

Summary

  • Define temporal isolation as a mandatory (black-box mechanisms) enforcement

provided by the OS.

  • Time protection for preventing microarchitectural timing channels
  • Effective on closing studied timing channels
  • Low overhead

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www.data61.csiro.au

Trustworthy Systems Qian Ge
 PhD candidate e qian.ge@data61.csiro.au w https://ts.data61.csiro.au/projects/TS/ timingchannels/

THANK YOU

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