A 5 security x line platform

1 LINE Architecture 2 Transport Security 3 Messaging and VoIP Security 4 Device Security

LINE Architecture

LINE Android Talk Server User DB

LINE

LINE iOS

LINE Desktop

Timeline

Auth

Media

LEGY Bot / OA

LEGY encryp t ion

SPDY/2

LEGY encryp t ion

SPDY/2

LEGY encryp t ion

SPDY/2

HTTP/HTTPS

LEGY

Line Event GatewaY

And more

Routing

Transport encryption

http://developers.linecorp.com/blog/?p=2381 http://developers.linecorp.com/blog/?p=2709

TLS Problems

Current version – TLS v1.2

TLS v1.3 aims to provide some solutions

Requires several round-trips to complete handshake

High RTT on mobile networks

• simplified handshake • 0-RTT • but not final yet (draft status)

https:// t lswg.github.io/ t ls13-spec/

Current version

• pinned RSA keys +AES • no X.509 certificates • 0-RTT handshake • no forward secrecy (FS)

LEGY Encryption

Lightweight TLS alternative

LEGY Encryption FS

Forward secrecy (FS)

Elliptic curve cryptography (ECC)

0-RTT handshake

AES-GCM for app data encryption

ECDH-based key exchange

first message under client ephemeral/server static subsequent messages under ephemeral/ephemeral

Messaging E2EE • End- to-end enc r yp t ion (E2EE) f o r L INE - Le t t e r Sea l ing • I n t roduced in Oc t 2015/ L INE 5 .3 .0 • I n i t i a l l y iOS/Andro id on ly • Appl i ed to t ex t and loca t ion messages

h t t p : / / d e v e l o p e r s . l i n e c o r p . c o m / b l o g / ? p = 3 6 7 9

Letter Sealing Evolution • Group cha t suppor t • Secondar y dev ice suppor t • Sta tus ind ica to r • ON by de fau l t iOS/Android 6.5.0+ Mac/Win 4.8.0+ • Planned enhancements Media encryption h t t p : / / d e v e l o p e r s . l i n e c o r p . c o m / b l o g / ? p = 3 6 7 9

Sending an Encrypted Message

LINE User 1 Talk

Server

1.user2 ’ s pub l ic key?

2 .send message

( ID :456 , pub key) LINE User 2

Message

AES encryp t

Message

to :user2 f rom:user1 toKeyID :456 f romKey ID :123 [sa l t ] [encryp ted da ta]

Message to :user2 f rom:user1 tex t : ’He l lo ’

Receiving an Encrypted Message

LINE User 1 Talk

Server

3.push message

4 .user1 ’ s pub l ic key?

( ID :123 , pub key)

LINE User 2

Message

Message

AES decryp t to :user2 f rom:user1 toKeyID :456 f romKey ID :123 [sa l t ] [encryp ted da ta]


Encrypted Message Exchange

LINE User 1 Talk

Server

1.user2 ’ s pub l ic key?

2 .send message


3 .push message

4 .user1 ’ s pub l ic key?


LINE User 2

Message

Message

AES encryp t to :user2 f rom:user1 toKeyID :456 f romKey ID :123 [sa l t ] [encryp ted da ta]


AES decryp t


Encryption Method Message user 1

shared secret KDF

(SS, sa l t ) KDF (SS, sa l t )

user1 p r iv key

user2 pub key

Keychain key ID:123 [p r iv key]

[user2 pub key]

[userN pub key]

ECDH (Curve22519)

user2 p r iv key

user1 pub key

Message

AES encryp t to :user2 f rom:user1 toKeyID :456 f romKey ID :123 [sa l t ] [encryp ted da ta]


AES decryp t


Keychain key ID:456 [p r iv key]

[user1 pub key]

[userN pub key]

user 2

Key Verification Android

Chat Settings > Encryption Key iOS

Settings > Encryption Key

Group Chat Support

Dedicated shared key is generated for each group

Encrypted shared key distributed to all members

Principle is same as 1:1 chats

Shared key is replaced when members leave or join

Key-encryption key derived for each member

ECDH key exchange AES encryption

Group Key Registration

LINE User 1

Talk Server

1.group1 member pub keys?

(user1 pubK,user2 pubK,user3 pubK)

3 .enc . g roup skey

Keychain

key ID:123 [p r iv key]

[g roup shared key]

[user3 pub key]

[user2 pub key]

Group Key fo r user1* [encryp ted skey]

fo r user2 [encryp ted skey]


2 .gen . g roup shared key

4 . reg is t e r g roup1 shared key

Group 1

Group Key fo r user1* [encryp ted skey]



user1

user2

user3

Group Key Distribution

LINE User 2 Talk

Server

1.group1 shared key?

(enc . skey fo r user2)

1 .g roup1 shared key?

(enc . skey fo r user3)

LINE User 3

Message

Keychain


[g roup1 shared key]

Group Key fo r user1* [enc ryp ted skey]

fo r user2 [enc ryp ted skey]

fo r user3 [enc ryp ted skey]

Keychain


[g roup1 shared key]

2 .decryp t & save g roup shared key

2 .decryp t & save g roup shared key

VoIP E2EE • L INE 6 .5 .0+ • ECDH key exchange ephemeral keys server-mediated custom SIP headers • Media s t ream enc r yp t ion SRTP AES-CTR + HMAC-SHA1

Device Security

True Delete - Since 5.3.0

More advanced data protection features

coming soon

Overwrit ing NULL

http://developers.linecorp.com/blog/?p=3660

LINE Encryption Whitepaper

Detailed cryptographic protocol specification

Covers

Available now at

transport encryption Letter Sealing

https://linecorp.com/en/security/artic le/37

messaging E2EE VoIP E2EE

1 Risk Assessment 2 Anti-Spam/Game Abusing 3 Bug Bounty Program

Risk Assessment Monitoring Bug Bounty

Design Implement QA Operate

Risk Assessment

Server

• XSS • CSRF • Path Traversal • Open-Redirect

Client

Web

Server

• Analyzing the protocol • Abusing/Cheating • Bot (un-off ic ial cl ient)

Client

LINE / Game

• Reversing • Modifying

Risk Assessment

Server

• Analyzing the protocol • Abusing/Cheating • Bot (un-off ic ial cl ient)

Client

LINE / Game

• Reversing • Modifying

Reverse engineering

Malware analysis

Vulnerability diagnosis/

investigation

Illegal copy of contents

Software tracking, cheating

Reverse engineering is a process of analyzing software/hardware and examining operating principles, source code, and development methods.

Purpose of use (examples)

Change in game environment

Cheat tools are created

Possible to level up without spending money and time

Bots are created Online, item purchase

Android, iOS opening up of the platform

Security Measures

Enhance security to the level where it is difficulty to abuse/cheat

Bot/abuser detection is performed on the server side

General cheat tool counter measure Encryption of locally stored data Encryption of communication between games and servers ARM/IL analysis measure

Abuser detection/automation

RA for LINE Games Memory / file cheat

• Possible to prevent it by storing score and other data on the server • Status data, such as attack power and HP, are fully handled on the client, and there is no counter measure for them.

From GameHacker

RA for LINE Games Speed hack

Ex.1: Stamina power recovery (possible to prevent)

Stamina: 40 / 100

Time: 12:54

Stamina: 40 / 100 Sync Abuser: added extra 20 min

to in-game t ime

Time: 12:34 Not ice

Stamina power recovery

Time: 12:34 Time: 12:34 Sync Since i t does not match server-side

t ime, the notice is rejected.

RA for LINE Games Speed hack

Ex.2: Time attack (impossible to prevent)

Time: 12:20

Time: 12:21

Time: 12:20 Sync

Star t a stage

Time: 12:21 Not ice

Stage clear notice

• Play game at twice the speed • Fake a stage clear notice

I f set to a real ist ic t ime, the server cannot detect the hack.

RA for LINE Games MITM (Man-In-The-Middle)

• I f i t is just HTTPS, communication is analyzed by MITM • SSL pinning should be performed in the game

However, the data is decrypted in the game. Hence, there is no perfect counter measure.

certificate

Possible to view communication

RA for LINE Games MITM (Man-In-The-Middle)

• Place proxy certif icate in device • With only HTTPS, communication is cryptanalyzed by MITM • [Measure]Execute SSL Pinning (certif icate check) in game

Check certificate

SSL Pinning

public static bool ValidateServerCertificate (object sender,System.Security.Cryptography.X509Certificates.X509Certificate certificate, X509Chain chain, System.Net.Security.SslPolicyErrors sslPolicyErrors) { string chash = certificate.GetCertHashString (); if (chash == " (hardcoded hash)") return true; // SSL certificate check ok return false; }

Examples of code to check certif icate of communication partner in game (Check routine may be removed)

RA for LINE Games

Unity C# -> CIL (DLL) -> Decompile *.dll C# -> CIL -> ASM(il2cpp) -> Disassemble libil2cpp.so

Cocos2d-x C++ -> .so -> Disassemble *.so

RA for LINE Games

Unity C# -> CIL (DLL) -> Decompile *.dll

From ILSpy

public void TakeDamage (int amount) { damaged = true; currentHealth -= amount; healthSlider.value = currentHealth; playerAudio.Play (); if(currentHealth <= 0 && !isDead) Death (); }

public void TakeDamage(int amount) { this.damaged = true; this.currentHealth -= amount; this.healthSlider.set_value( (float)this.currentHealth); this.playerAudio.Play(); if (this.currentHealth <= 0 && !this.isDead) { this.Death(); } }

RA for LINE Games

Unity C# -> CIL -> ASM(il2cpp) -> Disassemble libil2cpp.so

From IDA

public void TakeDamage (int amount) { damaged = true; currentHealth -= amount; healthSlider.value = currentHealth; playerAudio.Play (); if(currentHealth <= 0 && !isDead) Death (); }

RA for LINE Games

From IDA

Security Measures

Enhance security to the level where it is difficulty to abuse/cheat

Bot/abuser detection is performed on the server side

General cheat tool counter measure Encryption of locally stored data Encryption of communication between games and servers ARM/IL analysis measure

Abuser detection/automation

Security Measures

Duration/period/frequency of game play

Timing of level up Timing of stage clear Item usage history (including payment) IP bandwidth

Detect anomalies based on the characteristics below, while taking false positives into utmost consideration

Human Bot

Anti-Spam Message

Spammer’s Account

Security CS

spam message

Users

Anti-Spam

block Repor t Query

LINE • Block rule • Text mining • Human check

Check flow

Anti-Spam/Abusing

Operator takes necessary measures (e.g. adding rules)

Finds potential loopholes for the abuser (measures for the measure)

Operator takes additional measures (return to 2.)

Datasets change

Datasets change

Datasets change

Anti-Spam/Abusing

Datasets change periodically

False positives of less than 0.01%

Datasets change

Datasets change

Datasets change

Able to explain the cause of false positives

There is a limit to detection by machine learning based on similarity. (Manual check is essential.)

Anti-Spam/Abusing

Bring client (app) measure to a certain level

Automate server-side as much as possible

Final check to be done manually (as needed)

We intend to explore this area and implement further automation

Bug Bounty Program https://bugbounty. l inecorp.com/ja/

Bug Bounty Program

0

5

10

15

20

25

The number of reports

6/2 6/16 6/30 7/14 7/28 8/11

Category

XSS

CSRF

RCE

Auth bypass

Purchase bypass

Encryption break

Other

A 5 security x line platform

Technology

Transcript of A 5 security x line platform