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Issue Date:

Revision:

TLS/SSL

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25-29 June 2018PacNOG 22, Honiara, Solomon IslandsSupported by:

History

• Secure Sockets Layer was developed by Netscape in 1994 as a protocol which permitted persistent and secure transactions.

• In 1997 an Open Source version of Netscape’s patented version was created, which is now OpenSSL.

• In 1999 the existing protocol was extended by a version now known as Transport Layer Security (TLS).

• By convention, the term "SSL" is used even when technically the TLS protocol is being used.

2This document is uncontrolled when printed. Before use, check the APNIC electronic master document to verify that this is the current version.

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Location of SSL Protocol & TCP Ports

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TLS/SSL: What it does

• Confidentiality– Encryption

• Integrity– Keyed hash (HMAC): TLS (authentication!)– Hash (MAC): SSL

• Authentication– Certificates

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SSL/TLS Operations

• Client connects to the server– To access a resource

• Public Key cryptography is used during handshake to authenticate parties and exchange session key.– PKI (X.509 Certificates)

• Symmetric Key cryptography to encrypt and hash data.– M aster secret (shared secret) generated

– Separate Encryption and H ashing keys from the m aster secret

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How SSL/TLS Works – Part 1

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PKI – public key infra

• Digital (X.509) certificates– associa tes a public key w ith an ind iv idual or organization– public key of the subject!

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PKI – Chain of Trust

• Root CA– Self-s igned– Issue and sign IC A’s

certifica te

• Intermediate CA– Issue and sign EE

certifica te

• End Entity

8This document is uncontrolled when printed. Before use, check the APNIC electronic master document to verify that this is the current version.

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PKI - Example

• Client (browser) sends https request to google.com– brow sers have trusted C A certificates stored

• Web server sends back google.com’scertificate– S igned by G oogle IC A , p lus

– G oogle IC A’s certificate s igned by root C A(G eoTrust)

• Verify the certificates up the chain of trust– O nce successfu lly verified, use the public

key

9This document is uncontrolled when printed. Before use, check the APNIC electronic master document to verify that this is the current version.

How SSL/TLS Works – Part 2

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Symmetric Encryption

• Once the server’s public key is verified up the chain of trust– The client generates a pre-m aster secret

• C-random & S-random– Sends to the server encrypted w ith server ’s public key

• Both client and server generates the Master Secret– U ses the pre-m aster secret, C -random , and S -random w ith the

agreed key exchange cipher (eg: D H )

• Separate Encryption and Hashing keys generated from the Master secret– A ll fu ture com m unication hashed and encrypted using the sym m etric

keys

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SSL Protocol Building Blocks

SSL is a Combination of a Primary Record Protocolwith Four ‘Client’ Protocols

SSLChange Cipher

Spec Protocol

SSL Alert

Protocol

SSLHandshake

Protocol

ApplicationData

Protocol

SSL Record Protocol

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SSL Protocol Building Block Functions

SSLAlert

Protocol

Ind icates error or the end of a session

SSLChange Cipher

Spec Protocol

Used to Signal Transition to New Cipherand Keys Generally Towards the End of a

Handshake Negotiation

SSLRecord

Protocol

Ind icates which encryption andintegrity protection is applied

to the data

SSL Handshake

Protocol

Negotiates crypto algorithm s and keys

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Trusted vs Non Trusted Certificate

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Certificate Authority

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Chinese CA WoSign faces revocation after issuing fake certificates of Github, Microsoft and Alibaba

https://groups.google.com/forum/m/#!topic/mozilla.dev.security.policy/k9PBmyLCi8I/discussion

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Introducing Let’sEncrypt

https://letsencrypt.org/

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Introducing Let’sEncrypt

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• Which browsers and operating systems support Let’s Encrypt– https://com m unity.le tsencrypt.org/t/w hich-brow sers-and-operating-

system s-support-le ts-encrypt/4394

• Check your browser– https://w ik i.apnictra in ing.net

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When were different SSL versions created?• SSL 3.0 in 1996

• TLS 1.0 in 1990

• TLS 1.1 in 2006

• TLS 1.2 in 2008

19This document is uncontrolled when printed. Before use, check the APNIC electronic master document to verify that this is the current version.

SSLLabs – Handson

• Do People Configure TLS/SSL (HTTPS) Correctly?

• 1. Go to https://www.ssllabs.com/ssltest/

• 2. Insert URL

• 3. What grade did you get and why?

• 4. How do we fix it?

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Recommended References

• 1. Better Crypto– https://w w w.bettercrypto.org

• 2. Bulletproof SSL & TLS– https://w w w.fe istyduck.com /books/bu lle tproof-ssl-and-tls/

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LAB

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