Achieving Keyless CDNs with Conclaves · Key sharing is widespread Who shares? 0 0.2 0.4 0.6 0.8 1...

Achieving Keyless CDNswith Conclaves

Stephen Herwig

Dave LevinChristina Garman

Measurement and Analysis of Private Key Sharing in

the HTTPS Ecosystem

Frank Cangialosi, Taejoong Chung, David Choffnes, Dave Levin, Bruce M. Maggs, Alan Mislove, Christo Wilson

User Bank

customer’s origin server

Content Delivery Networks host their customers’ websites

CDNs


CDN’sedge server

Content Delivery Networks host their customers’ websites

CDNs CDNs reduce page load times

CDN’sedge server


CDNsCDNs mitigate and block attacks

CDN’sedge server


Customers share their keys with CDNs

CDN’sedge server

bank’s private key

Customers share their keys with CDNs

CDN’sedge server

Key sharing is widespread

Cangialosi et al., CCS 2016


Who shares?

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Alexa Site Rank (bins of 10,000)

At least one key sharedAll keys shared

43% of the top 10k most popular websites



Who shares?

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Alexa Site Rank (bins of 10,000)

At least one key sharedAll keys shared

43% of the top 10k most popular websites


The web has consolidated keys in the hands of a few CDNs

Keyless SSL

Introduced by Cloudflare to mitigate key sharing

Keyless SSL


Private keys stay at the key server (origin)

Keyless SSL



Key server performs actions requiring private key


Keyless SSL



The CDN learns all session keys


Keyless SSL



The CDN learns all session keys

In practice: CDN

Third-party resources on

using Legacy applications

Can we Maintain privacy

?

Third-party resources

Legacy applications

Maintain privacy The CDN is no more trusted than a standard on-path attacker


Legacy applications


No changes to existing code-bases; facilitates deployment and adoption


Legacy applications


Leverage the existing infrastructure.One additional assumption: TEEs



Legacy applications


Leverage the existing infrastructure.One additional assumption: TEEs


Phoenix

Trusted execution environments

Hardware

OperatingSystem

Application

By default, assume all system components are untrusted

Code

Service


Hardware

OperatingSystem

Application


Small trusted CPU Resistant to physical attacks

Code

Service


Hardware

OperatingSystem

Application



Code

Service

Enclave: Isolated application memory

Enclave


Hardware

OperatingSystem

Application



Code

Service

Model: Code and data can safely reside inside an enclave

Enclave: Isolated application memory

Enclave

Hardware

OperatingSystem

Application Code

Service

Practical limitations of TEEs

Syscalls

Untrusted

Applications inside enclaves cannot make syscalls

Enclave

Hardware

OperatingSystem

Service

libOSesIdea: Implement a small “OS” inside the enclave

Enclave

Hardware

OperatingSystem

Service

Application Code

libOS Service

libOSesIdea: Implement a small “OS” inside the enclave

Enclave

Hardware

OperatingSystem

Service

Application Code

libOS Service

libOSes

"Syscalls"

Idea: Implement a small “OS” inside the enclave

Enclave

Hardware

OperatingSystem

Service

Application Code

libOS Service

libOSes

"Syscalls"


Enclave

Service locallywhen possible

Hardware

OperatingSystem

Service

Application Code

libOS Service

libOSes

"Syscalls"


Enclave

Service locallywhen possible

Syscalls

Graphene-SGX

Tsai et al., ATC 2017

A libOS for Intel SGX that supports some services

Graphene-SGXA libOS for Intel SGX that supports some services

fork

exec

Graphene’s supported services:

pipes, signals, semaphores

Tsai et al., ATC 2017


fork

exec



What constitutes a CDN?

Cache

Web Application Firewall

Key Server

Web serverMultipletenants

Needs plaintext

Needs disk

Needs safe

storage


fork

exec




Cache


Key Server

Reading & writing files

Shared memory

Also critical to a CDN:

Access to private keys


Needs plaintext

Needs disk

Needs safe

storage

The first truly keyless CDN

fork

exec




Cache


Key Server


Needs plaintext

Needs disk

Needs safe

storage

PhoenixContainers of enclavesConclaves


fork

exec




Cache


Key Server


Shared memory

Also critical to a CDN:



Needs plaintext

Needs disk

Needs safe

storage


Enclave

Enclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache


Insight: Treat enclaves like a distributed system Implement services using kernel servers

Enclave

Enclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache



TLS

Enclaves mutually authenticate via

attested TLS

Knauth et al., 2018

Enclave

Enclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache



TLS

Private key operation

Enclaves mutually authenticate via

attested TLS

Knauth et al., 2018

Enclave

Enclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache



TLS

Private key operation

ResultEnclaves mutually authenticate via

attested TLS

Knauth et al., 2018

EnclaveEnclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache



Enclave

Memory Server

EnclaveEnclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache



Enclave

Memory Server

Shared memory read

EnclaveEnclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache



Enclave

Memory Server

Shared memory read

Shared memory write

EnclaveEnclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache



Enclave

Memory Server

Application Code

libOS Service

Enclave

Enclave

Memory Server

Hardware

OperatingSystem

Service

Shared memoryConclaves

Application

libOS Service

Enclave

Enclave

Memory Server

Hardware

OperatingSystem

Service

fcntl()


Application

libOS Service

Enclave

"Syscall"Enclave

Memory Server

Hardware

OperatingSystem

Service

fcntl()


Application

libOS Service

Enclave

"Syscall"Enclave

Memory ServerRPC

Hardware

OperatingSystem

Service

fcntl()


Application

libOS Service

Enclave

"Syscall"Enclave

Memory ServerRPC

Hardware

OperatingSystem

Service

Coordinates locks Maintains memory locations

fcntl()


Application

libOS Service

Enclave

"Syscall"Enclave

Memory Server

Hardware

OperatingSystem

Service


fcntl()


Application

libOS Service

Enclave

"Syscall"Enclave

Memory Server

Hardware

OperatingSystem

Service

SyscallCoordinates locks Maintains memory locations

fcntl()


Application

libOS Service

Enclave

"Syscall"Enclave

Memory Server

Hardware

OperatingSystem

Service

Syscall

Memory file Encrypted on untrusted disk


fcntl()


Application

libOS Service

Enclave

Enclave

Memory Server

Hardware

OperatingSystem

Service

Memory file Encrypted on untrusted disk


Shared Memoryfcntl()


EnclaveEnclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache



Enclave

Memory Server

EnclaveEnclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache



Enclave

Memory Server

Enclave

File Server

EnclaveEnclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache



Enclave

Memory Server

Enclave

File Server

File access

EnclaveEnclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache



Enclave

Memory Server

Enclave

File Server

File access

Verified data

Application Code

libOS Service

Enclave

Enclave

File Server

Hardware

OperatingSystem

Service

File system accessConclaves

Application Code

libOS Service

Enclave

Enclave

File Server


Hardware

OperatingSystem

Service

Merkle TreeEncrypted on untrusted disk

Application

libOS Service

Enclave

Enclave

File Server

Hardware

OperatingSystem

Service

read()

Conclaves


File system access

Application

libOS Service

Enclave

"Syscall"Enclave

File Server

Hardware

OperatingSystem

Service

read()

Conclaves


File system access

Application

libOS Service

Enclave

"Syscall"Enclave

File ServerRPC

Hardware

OperatingSystem

Service

read()

Conclaves


File system access

Application

libOS Service

Enclave

"Syscall" Enclave

read()

libOS

Conclaves

Hardware

OperatingSystem

Service


RPC

ext2fs server

Block layerMerkle root

File system access

Application

libOS Service

Enclave

"Syscall" Enclave

read()

libOS

Conclaves

Hardware

OperatingSystem

Service


RPC

Syscall

ext2fs server


File system access

Application

libOS Service

Enclave

"Syscall" Enclave

read()

libOS

Conclaves

Hardware

OperatingSystem

Service


RPC

Syscall

Verifies branches

Decrypts blocks

ext2fs server


File system access

Application

libOS Service

Enclave

read()


Hardware

OperatingSystem

Service


Enclave

ext2fs server

libOS


Data Verifies branches

Decrypts blocks

EnclaveEnclave

Web server

Cache


Enclave

Web server

Cache


Key ServerEnclave

Web server

Cache


Execution environment is a distributed system of enclaves

Enclave

Memory Server

Enclave

File Server

The first truly keyless CDNPhoenixContainers of enclavesConclaves

EnclaveEnclave

Web server

Cache


Enclave

Web server

Cache


Key ServerEnclave

Web server

Cache



Enclave

Memory Server

Enclave

File Server

Conclave


EnclaveEnclave

Web server

Cache


Enclave

Web server

Cache



Key Server


Enclave

Web server

Cache



Enclave

Memory Server

Enclave

File Server

Conclave

fork

exec

Conclaves supported services:



Shared memory


Trusted time server

The first truly keyless CDNPhoenix


Websites delegate provisioning to CDNs

Phoenix supports many deployment configurations

Other details in the paper

Supports multi-tenancyBoth CDN and website can store private data


Websites delegate provisioning to CDNs

Phoenix supports many deployment configurations

Other details in the paper

Conclave Conclave Conclave

Supports multi-tenancyBoth CDN and website can store private data


Conclave Conclave Conclave

ARTIFACTEVALUATED

PASSED

Implemented on top of Graphene-SGX

Evaluated to understand throughput and scalability

0 500

1000 1500 2000 2500 3000 3500

1 KiB 10 KiB 100 KiB

# Workers1 2 4 8

Thro

ughp

ut (r

eque

sts/

sec)

Downloaded file size

Fetch a file 10,000 times over non-persistent HTTPS connections from among 128 concurrent clients

What is Phoenix’s request throughput?

0 500

1000 1500 2000 2500 3000 3500


# Workers1 2 4 8

Thro

ughp

ut (r

eque

sts/

sec)


Linux

Fetch a file 10,000 times over non-persistent HTTPS connections from among 128 concurrent clients

NGINX running on normal Linux


0 500

1000 1500 2000 2500 3000 3500


# Workers1 2 4 8

Thro

ughp

ut (r

eque

sts/

sec)


LinuxPhoenix-cryptPhoenix-vericrypt

Fetch a file 10,000 times over non-persistent HTTPS connections from among 128 concurrent clients confidentiality

confidentiality & integrity


How does Phoenix scale to multiple tenants?

0 200 400 600 800

1000 1200 1400 1600

1 2 4 6

Tim

e pe

r req

uest

(ms)

Number of tenants

Linux (shared NGINX)

40 ms

264 ms

0 200 400 600 800

1000 1200 1400 1600

1 2 4 6

Tim

e pe

r req

uest

(ms)

Number of tenants

Linux (shared NGINX)

Phoenix-crypt (shared nothing)

816

32

48


264 ms

40 ms127 ms

1437 ms

Number of enclaves

0 200 400 600 800

1000 1200 1400 1600

1 2 4 6

Tim

e pe

r req

uest

(ms)

Number of tenants

Linux (shared NGINX)Phoenix-crypt (shared NGINX)

810

14

18


816

32

48

Number of enclaves


264 ms

40 ms

128 ms127 ms

1437 ms

806 ms

0 200 400 600 800

1000 1200 1400 1600

1 2 4 61

1K

10K

100K

1M

10M

Tim

e pe

r req

uest

(ms)

SGX

pagi

ng e

vent

s

Number of tenants

Linux (shared NGINX)Phoenix-crypt (shared NGINX)

810

14

18


816

32

48


Number of enclaves

264 ms

40 ms

128 ms

806 ms

127 ms

1437 ms

Other results

Benchmark overhead of running WAFs (ModSecurity) in SGX (overhead about the same as in Linux)

Perform detailed micro-benchmarks of each kernel server

Compare standard ocalls to exitless ocalls(not always better)

ARTIFACTEVALUATED

PASSED

Moderate performance overheads

https://phoenix.cs.umd.edu/

0 500

1000 1500 2000 2500 3000 3500


# Workers1 2 4 8

Thro

ughp

ut (r

eque

sts/

sec)


LinuxPhoenix-cryptPhoenix-vericrypt


Run legacy apps in enclaves

Achieving Keyless CDNs with Conclaves · Key sharing is widespread Who shares? 0 0.2 0.4 0.6 0.8 1...

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