modules/tls-01.html

<!--
  Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
  the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
-->
<section>
  <h2>Introduction to TLS</h2>
</section>
<section>
  <h3>Why?</h3>
  <p>Lots of questions about TLS on the mailing lists</p>
  <p>It is clear many folks don’t understand how TLS works</p>
  <p>Debugging something you don’t understand is hard</p>
  <p>Should use TLS not SSL</p>
  <p>I’ll probably use them interchangeably<br/>(as do the Tomcat docs)</p>
</section>
<section>
  <h3>Cryptography Basics</h3>
</section>
<section>
  <h3>Symmetric Encryption</h3>
  <p>Use the same secret key to encrypt and decrypt</p>
  <img src="../images/tls-01/diagram-01.svg" style="border: none; box-shadow:none;"/>
</section>
<section>
  <h3>Asymmetric Encryption</h3>
  <p>Pair of keys, A and B</p>
  <p>A and B are mathematically related</p>
  <p>Very hard to derive one from the other</p> 
  <p>Encrypt with A, decrypt with B</p>
  <p>Encrypt with B, decrypt with A</p>
  <p>Make one key public</p>
  <p>Keep one key private</p>
</section>
<section>
  <h3>Asymmetric Encryption</h3>
  <p>Encrypt with public key, decrypt with private key</p>
  <img src="../images/tls-01/diagram-02.svg" style="border: none; box-shadow:none;"/>
</section>
<section>
  <h3>Asymmetric Encryption</h3>
  <p>Encrypt with private key, decrypt with public key</p>
  <img src="../images/tls-01/diagram-03.svg" style="border: none; box-shadow:none;"/>
</section>
<section>
  <h3>Hash Functions</h3>
  <p>Generate a fingerprint (hash) for a given input</p>
  <p>Small change in input gives a large change in the hash</p>
  <p>Very difficult to generate an input for a given hash</p>
  <img src="../images/tls-01/diagram-04.svg" style="border: none; box-shadow:none;"/>
</section>
<section>
  <h3>Digital Signatures</h3>
  <p>Proves a document was sent by a given entity</p>
  <img src="../images/tls-01/diagram-05.svg" style="border: none; box-shadow:none;"/>
</section>
<section>
  <h3>Digital Signatures</h3>
  <p>Validation</p>
  <img src="../images/tls-01/diagram-06.svg" style="border: none; box-shadow:none;"/>
</section>
<section>
  <h3>Digital Signatures</h3>
  <p>If the hashes match...</p>
  <p>...then the public key decrypted the digital signature...</p>
  <p>...so the private key created the digital signature...</p>
  <p>...so the owner of the private key signed the document</p>
  <p/>
  <p>Who owns the private key?</p>
</section>
<section>
  <h3>Certificates</h3>
  <p>Associates a public key with an identity</p>
  <img src="../images/tls-01/diagram-07.svg" style="border: none; box-shadow:none;"/>
</section>
<section>
  <h3>Certificates</h3>
  <p>CA is Certificate Authority</p>
  <p>Need to link CA's public key to CA's identity</p>
  <p>Use another certificate</p>
  <p>Result is a chain of certificates</p>
  <p>Chain ends with a root certificate authority</p>
  <p>There are multiple root CAs</p>
</section>
<section>
  <h3>Root Certificates</h3>
  <p>Self-signed</p>
  <p>Alternative trust path required</p>
  <p>Often installed by OS</p>
  <p>Manual validation against root CA's web site</p>
  <img src="../images/tls-01/diagram-08.svg" style="border: none; box-shadow:none;"/>
</section>
<section>
  <h3>TLS Handshake: Starting point</h3>
  <img src="../images/tls-01/diagram-09.svg" style="border: none; box-shadow:none; float: right"/>
  <p style="text-align: left">Client:</p>
  <ul style="display: block">
    <li>CA certificates</li>
    <li>supported algorithms</li>
  </ul>
  <p style="text-align: left">Server:</p>
  <ul style="display: block">
    <li>Certificate</li>
    <li>Private key</li>
    <li>supported algorithms</li>
  </ul> 
</section>
<section>
  <h3 style="text-transform: none">Step 1: ClientHello</h3>
  <img src="../images/tls-01/diagram-10.svg" style="border: none; box-shadow:none; float: right"/>
  <p style="text-align: left">Client generates random number</p>
  <p style="text-align: left">Client sends message to server</p>
  <ul style="display: block">
    <li>supported algorithms</li>
    <li>random number</li>
  </ul> 
</section>
<section>
  <h3 style="text-transform: none">Step 2: ServerHello</h3>
  <img src="../images/tls-01/diagram-11.svg" style="border: none; box-shadow:none; float: right"/>
  <p style="text-align: left">Server generates random number</p>
  <p style="text-align: left">Server compares algorithms</p>
  <ul style="display: block">
    <li>selects algorithms</li>
  </ul> 
  <p style="text-align: left">Server sends message to client</p>
  <ul style="display: block">
    <li>selected algorithms</li>
    <li>random number</li>
  </ul> 
</section>
<section>
  <h3 style="text-transform: none">Step 3: Certificate</h3>
  <img src="../images/tls-01/diagram-12.svg" style="border: none; box-shadow:none; float: right"/>
  <p style="text-align: left">Server sends message to client</p>
  <ul style="display: block">
    <li>Server certificate</li>
  </ul> 
  <p style="text-align: left">Client validates certificate</p>
</section>
<section>
  <h3 style="text-transform: none">Step 6: ServerHelloDone</h3>
  <img src="../images/tls-01/diagram-13.svg" style="border: none; box-shadow:none; float: right"/>
  <p style="text-align: left">Server sends message to client</p>
  <ul style="display: block">
    <li>No content</li>
  </ul> 
</section>
<section>
  <h3 style="text-transform: none">Step 8: ClientKeyExchange</h3>
  <img src="../images/tls-01/diagram-14.svg" style="border: none; box-shadow:none; float: right"/>
  <p style="text-align: left">Client generates pre-master-secret</p>
  <p style="text-align: left">Client encrypts PMS with Server's public key</p>
  <p style="text-align: left">Client sends message to server</p>
  <ul style="display: block">
    <li>Encrypted PMS</li>
  </ul> 
</section>
<section>
  <h4 style="text-transform: none">Step 10: ChangeCipherSpec</h4>
  <img src="../images/tls-01/diagram-15.svg" style="border: none; box-shadow:none; float: right"/>
  <p style="text-align: left">Client generates master-secret</p>
  <ul style="display: block">
    <li>R<sub>C</sub> + R<sub>S</sub> + PMS</li>
  </ul> 
  <p style="text-align: left">Client switches to encrypted mode</p>
  <ul style="display: block">
    <li>Algorithms agreed in step 2</li>
    <li>Symmetric encryption with MS</li>
  </ul> 
  <p style="text-align: left">Client sends message to server</p>
  <ul style="display: block">
    <li>No content</li>
  </ul> 
</section>
<section>
  <h4 style="text-transform: none">Step 11: Finished</h4>
  <img src="../images/tls-01/diagram-15.svg" style="border: none; box-shadow:none; float: right"/>
  <p style="text-align: left">Client has completed handshake</p>
  <p style="text-align: left">Client sends message to server</p>
  <ul style="display: block">
    <li>No content</li>
  </ul> 
</section>
<section>
  <h4 style="text-transform: none">Step 12: ChangeCipherSpec</h4>
  <img src="../images/tls-01/diagram-16.svg" style="border: none; box-shadow:none; float: right"/>
  <p style="text-align: left">Server decrypts PMS</p>
  <p style="text-align: left">Server creates MS</p>
  <ul style="display: block">
    <li>R<sub>C</sub> + R<sub>S</sub> + PMS</li>
  </ul> 
  <p style="text-align: left">Server switches to encrypted mode</p>
  <ul style="display: block">
    <li>Algorithms agreed in step 2</li>
    <li>Symmetric encryption with MS</li>
  </ul> 
  <p style="text-align: left">Server sends message to client</p>
  <ul style="display: block">
    <li>No content</li>
  </ul> 
</section>
<section>
  <h4 style="text-transform: none">Step 13: Finished</h4>
  <img src="../images/tls-01/diagram-16.svg" style="border: none; box-shadow:none; float: right"/>
  <p style="text-align: left">Server has completed handshake</p>
  <p style="text-align: left">Server sends message to client</p>
  <ul style="display: block">
    <li>No content</li>
  </ul> 
</section>
<section>
  <h4>Encryption</h4>
  <p>Algorithms agreed in step 2</p>
  <p>Symmetric</p>
  <p>Master secret is shared secret key</p> 
</section>
<section>
  <h4>TLS Extensions</h4>
  <p>Client certificate authentication</p>
  <p>Server Name Indication</p>
  <p>Application Layer Protocol Negotiation</p> 
</section>