SSL and TLS essentials: Securing the Web

212 Pages·2000·0.932 MB·English

by  Thomas S.A.

SSL TLS
and
Essentials
Securing the Web
Stephen Thomas
SSL TLS Essentials
&
Securing the Web
Stephen A. Thomas

Wiley Computer Publishing
John Wiley & Sons, Inc.
New York •••• Chichester •••• Weinheim •••• Brisbane •••• Singapore •••• Toronto
Publisher: Robert Ipsen
Editor: Marjorie Spencer
Assistant Editor: Margaret Hendrey
Text Design & Composition: Stephen Thomas
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Copyright © 2000 by Stephen A. Thomas. All rights reserved.
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Library of Congress Cataloging-in-Publication Data:
Thomas, Stephen A., 1962-
ssl and tls essentials : securing the Web / Stephen A. Thomas.
p. cm.
Includes index.
isbn 0-471-38354-6 (pbk./cd-rom : alk. paper)
1. Computer networks--Security measures. 2. World Wide Web--Security
measures. 3. Computer network protocols. I. Title.
tk5105.59 .t49 2000
005.8--dc21 99-058910
Printed in the United States of America.
10 9 8 7 6 5 4 3 2 1
For Kelsie,
Zookeeper of Mango the Flamingo.

Contents

Chapter 1: Introduction 1
1.1 Web Security and Electronic Commerce 2
1.2 History of ssl and tls 4
1.3 Approaches to Network Security 6
1.3.1 Separate Security Protocol 8
1.3.2 Application-Specific Security 9
1.3.3 Security within Core Protocols 10
1.3.4 Parallel Security Protocol 11
1.4 Protocol Limitations 12
1.4.1 Fundamental Protocol Limitations 12
1.4.2 Tool Limitations 13
1.4.3 Environmental Limitations 14
1.5 Organization of This Book 14
Chapter 2: Basic Cryptography 17
2.1 Using Cryptography 18
2.1.1 Keeping Secrets 18
2.1.2 Proving Identity 19
2.1.3 Verifying Information 20
2.2 Types of Cryptography 21
2.2.1 Secret Key Cryptography 22
2.2.2 Public Key Cryptography 24
2.2.3 Combining Secret & Public Key Cryptography 27
2.3 Key Management 29
2.3.1 Public Key Certificates 29
2.3.2 Certificate Authorities 31
2.3.3 Certificate Hierarchies 33
2.3.4 Certificate Revocation Lists 35
ix
x SSL & TLS Essentials: Securing the Web
Chapter 3: SSL Operation 37
3.1 SSL Roles 37
3.2 SSL Messages 38
3.3 Establishing Encrypted Communications 39
3.3.1 ClientHello 41
3.3.2 ServerHello 43
3.3.3 ServerKeyExchange 45
3.3.4 ServerHelloDone 45
3.3.5 ClientKeyExchange 45
3.3.6 ChangeCipherSpec 46
3.3.7 Finished 51
3.4 Ending Secure Communications 52
3.5 Authenticating the Server’s Identity 52
3.5.1 Certificate 55
3.5.2 ClientKeyExchange 56
3.6 Separating Encryption from Authentication 56
3.6.1 Certificate 59
3.6.2 ServerKeyExchange 59
3.6.3 ClientKeyExchange 59
3.7 Authenticating the Client’s Identity 60
3.7.1 CertificateRequest 61
3.7.2 Certificate 62
3.7.3 CertificateVerify 63
3.8 Resuming a Previous Session 64
Chapter 4: Message Formats 67
4.1 Transport Requirements 68
4.2 Record Layer 69
4.3 ChangeCipherSpec Protocol 71
4.4 Alert Protocol 72
4.4.1 Severity Level 72
4.4.2 Alert Description 73
4.5 Handshake Protocol 74
4.5.1 HelloRequest 76
4.5.2 ClientHello 77
Contents xi
4.5.3 ServerHello 79
4.5.4 Certificate 80
4.5.5 ServerKeyExchange 81
4.5.6 CertificateRequest 84
4.5.7 ServerHelloDone 85
4.5.8 ClientKeyExchange 85
4.5.9 CertificateVerify 88
4.5.10 Finished 90
4.6 Securing Messages 92
4.6.1 Message Authentication Code 93
4.6.2 Encryption 95
4.6.3 Creating Cryptographic Parameters 96
4.7 Cipher Suites 102
4.7.1 Key Exchange Algorithms 103
4.7.2 Encryption Algorithms 104
4.7.3 Hash Algorithms 104
Chapter 5: Advanced SSL 105
5.1 Compatibility with Previous Versions 105
5.1.1 Negotiating ssl Versions 106
5.1.2 SSL Version 2.0 ClientHello 109
5.1.3 SSL Version 2.0 Cipher Suites 110
5.2 Netscape International Step-Up 111
5.2.1 Server Components 112
5.2.2 Client Components 112
5.2.3 Controlling Full-Strength Encryption 113
5.3 Microsoft Server Gated Cryptography 115
5.3.1 Server Gated Cryptography Certificates 115
5.3.2 Cipher Suite Renegotiation 115
5.4 The Transport Layer Security Protocol 117
5.4.1 TLS Protocol Version 118
5.4.2 Alert Protocol Message Types 118
5.4.3 Message Authentication 121
5.4.4 Key Material Generation 123
5.4.5 CertificateVerify 125
5.4.6 Finished 126
xii SSL & TLS Essentials: Securing the Web
5.4.7 Baseline Cipher Suites 126
5.4.8 Interoperability with SSL 128
5.5 The Future of ssl and tls 128
Appendix A: X.509 Certificates 131
A.1 X.509 Certificate Overview 132
A.1.1 Version 132
A.1.2 Serial Number 133
A.1.3 Algorithm Identifier 133
A.1.4 Issuer 133
A.1.5 Period of Validity 133
A.1.6 Subject 134
A.1.7 Subject’s Public Key 134
A.1.8 Issuer Unique Identifier 134
A.1.9 Subject Unique Identifier 134
A.1.10 Extensions 135
A.1.11 Signature 135
A.2 Abstract Syntax Notation One 135
A.2.1 Primitive Objects 136
A.2.2 Constructed Objects 136
A.2.3 The Object Identifier Hierarchy 137
A.2.4 Tagging 139
A.2.5 Encoding Rules 142
A.3 X.509 Certificate Definition 145
A.3.1 The Certificate Object 145
A.3.2 The Version Object 146
A.3.3 The CertificateSerialNumber Object 147
A.3.4 The AlgorithmIdentifier Object 147
A.3.5 The Validity Object 148
A.3.6 The SubjectPublicKeyInfo Object 148
A.3.7 The Time Object 149
A.3.8 The Extensions Object 149
A.3.9 The UniqueIdentifier Object 150
A.3.10 The Name Object 150
A.4 Example Certificate 152
Contents xiii
Appendix B: SSL Security Checklist 161
B.1 Authentication Issues 161
B.1.1 Certificate Authority 162
B.1.2 Certificate Signature 163
B.1.3 Certificate Validity Times 163
B.1.4 Certificate Revocation Status 163
B.1.5 Certificate Subject 163
B.1.6 Diffie-Hellman Trapdoors 164
B.1.7 Algorithm Rollback 164
B.1.8 Dropped ChangeCipherSpec Messages 165
B.2 Encryption Issues 166
B.2.1 Encryption Key Size 166
B.2.2 Traffic Analysis 167
B.2.3 The Bleichenbacher Attack 168
B.3 General Issues 170
B.3.1 RSA Key Size 170
B.3.2 Version Rollback Attacks 171
B.3.3 Premature Closure 171
B.3.4 SessionID Values 172
B.3.5 Random Number Generation 172
B.3.6 Random Number Seeding 173
References 175
Protocol Standards 175
Certificate Formats 176
Cryptographic Algorithms 177
SSL Implementations 178
Glossary 179
Index 191