Java Coding Guidelines: 75 Recommendations for Reliable and Secure Programs

Fred Long / Dhruv Mohindra / Robert C. Seacord / Dean F. Sutherland / David Svoboda  
August 2013
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Java Coding Guidelines: 75 Recommendations for Reliable and Secure Programs


“A must-read for all Java developers. . . . Every developer has a responsibility to author code that is free of significant security vulnerabilities. This book provides realistic guidance to help Java developers implement desired functionality with security, reliability, and maintainability goals in mind.”

–Mary Ann Davidson, Chief Security Officer, Oracle Corporation 

Organizations worldwide rely on Java code to perform mission-critical tasks, and therefore that code must be reliable, robust, fast, maintainable, and secure. Java™ Coding Guidelines brings together expert guidelines, recommendations, and code examples to help you meet these demands.


Written by the same team that brought you The CERT® Oracle ® Secure Coding Standard for Java™, this guide extends that previous work’s expert security advice to address many additional quality attributes.


You’ll find 75 guidelines, each presented consistently and intuitively. For each guideline, conformance requirements are specified; for most, noncompliant code examples and compliant solutions are also offered. The authors explain when to apply each guideline and provide references to even more detailed information.


Reflecting pioneering research on Java security, Java™ Coding Guidelines offers updated techniques for protecting against both deliberate attacks and other unexpected events. You’ll find best practices for improving code reliability and clarity, and a full chapter exposing common misunderstandings that lead to suboptimal code.


With a Foreword by James A. Gosling, Father of the Java Programming Language

New to this Edition

This is the successor title to The CERT Oracle Secure Coding Standard for Java, which focused specifically on coding for better security. The new book covers both security and a wide range of additional quality attributes, including performance, availability, and maintainability.

Table of Contents

Foreword xi

Preface xiii

Acknowledgments xix

About the Authors xxi


Chapter 1: Security 1

1. Limit the lifetime of sensitive data 2

2. Do not store unencrypted sensitive information on the client side 5

3. Provide sensitive mutable classes with unmodifiable wrappers 9

4. Ensure that security-sensitive methods are called with validated arguments 11

5. Prevent arbitrary file upload 13

6. Properly encode or escape output 16

7. Prevent code injection 20

8. Prevent XPath injection 23

9. Prevent LDAP injection 27

10. Do not use the clone() method to copy untrusted method parameters 31

11. Do not use Object.equals() to compare cryptographic keys 34

12. Do not use insecure or weak cryptographic algorithms 36

13. Store passwords using a hash function 37

14. Ensure that SecureRandom is properly seeded 42

15. Do not rely on methods that can be overridden by untrusted code 44

16. Avoid granting excess privileges 50

17. Minimize privileged code 54

18. Do not expose methods that use reduced-security checks to untrusted code 56

19. Define custom security permissions for fine-grained security 64

20. Create a secure sandbox using a security manager 67

21. Do not let untrusted code misuse privileges of callback methods 72


Chapter 2: Defensive Programming 79

22. Minimize the scope of variables 80

23. Minimize the scope of the @SuppressWarnings annotation 82

24. Minimize the accessibility of classes and their members 84

25. Document thread-safety and use annotations where applicable 89

26. Always provide feedback about the resulting value of a method 96

27. Identify files using multiple file attributes 99

28. Do not attach significance to the ordinal associated with an enum 106

29. Be aware of numeric promotion behavior 108

30. Enable compile-time type checking of variable arity parameter types 112

31. Do not apply public final to constants whose value might change in later releases 115

32. Avoid cyclic dependencies between packages 118

33. Prefer user-defined exceptions over more general exception types 121

34. Try to gracefully recover from system errors 123

35. Carefully design interfaces before releasing them 125

36. Write garbage collection–friendly code 128


Chapter 3: Reliability 131

37. Do not shadow or obscure identifiers in subscopes 132

38. Do not declare more than one variable per declaration 134

39. Use meaningful symbolic constants to represent literal values in program logic 138

40. Properly encode relationships in constant definitions 142

41. Return an empty array or collection instead of a null value for methods that return an array or collection 143

42. Use exceptions only for exceptional conditions 146

43. Use a try-with-resources statement to safely handle closeable resources 148

44. Do not use assertions to verify the absence of runtime errors 151

45. Use the same type for the second and third operands in conditional expressions 153

46. Do not serialize direct handles to system resources 157

47. Prefer using iterators over enumerations 159

48. Do not use direct buffers for short-lived, infrequently used objects 162

49. Remove short-lived objects from long-lived container objects 163


Chapter 4: Program Understandability 167

50. Be careful using visually misleading identifiers and literals 167

51. Avoid ambiguous overloading of variable arity methods 171

52. Avoid in-band error indicators 173

53. Do not perform assignments in conditional expressions 175

54. Use braces for the body of an if, for, or while statement 178

55. Do not place a semicolon immediately following an if, for, or while condition 180

56. Finish every set of statements associated with a case label with a break statement 181

57. Avoid inadvertent wrapping of loop counters 183

58. Use parentheses for precedence of operation 186

59. Do not make assumptions about file creation 189

60. Convert integers to floating-point for floating-point operations 191

61. Ensure that the clone() method calls super.clone() 194

62. Use comments consistently and in a readable fashion 196

63. Detect and remove superfluous code and values 198

64. Strive for logical completeness 202

65. Avoid ambiguous or confusing uses of overloading 205


Chapter 5: Programmer Misconceptions 209

66. Do not assume that declaring a reference volatile guarantees safe publication of the members of the referenced object 209

67. Do not assume that the sleep(), yield(), or getState() methods provide synchronization semantics 216

68. Do not assume that the remainder operator always returns a nonnegative result for integral operands 220

69. Do not confuse abstract object equality with reference equality 222

70. Understand the differences between bitwise and logical operators 225

71. Understand how escape characters are interpreted when strings are loaded 228

72. Do not use overloaded methods to differentiate between runtime types 231

73. Never confuse the immutability of a reference with that of the referenced object 234

74. Use the serialization methods writeUnshared() and readUnshared() with care 239

75. Do not attempt to help the garbage collector by setting local reference variables to null 243


Appendix A: Android 245


Glossary 249

References 255

Index 263


Fred Long is a senior lecturer in the Department of Computer Science, Aberystwyth University, in the United Kingdom. He is chairman of the British Computer Society’s Mid-Wales Branch. Fred has been a visiting scientist at the Software Engineering Institute (SEI) since 1992. Recently, his research has involved the investigation of vulnerabilities in Java. Fred is also a coauthor of The CERT® Oracle® Secure Coding Standard for Java™ (Addison-Wesley, 2012).


Dhruv Mohindra is a technical lead in the security practices group that is part of the CTO’s office at Persistent Systems Limited, India, where he provides information security consulting solutions across various technology verticals such as cloud, collaboration, banking and finance, telecommunications, enterprise, mobility, life sciences, and health care. Dhruv has worked for CERT at the Software Engineering Institute and continues to collaborate to improve the state of security awareness in the programming community. Dhruv is also a coauthor of The CERT® Oracle® Secure Coding Standard for Java™ (Addison-Wesley, 2012).


Robert C. Seacord is the Secure Coding Initiative technical manager in the CERT Program of Carnegie Mellon’s Software Engineering Institute (SEI) in Pittsburgh, Pennsylvania. Robert is also a professor in the School of Computer and the Information Networking Institute at Carnegie Mellon University. He is the author of The CERT C Secure Coding Standard (Addison-Wesley, 2008), and is coauthor of Building Systems from Commercial Components (Addison-Wesley, 2002), Modernizing Legacy Systems (Addison-Wesley, 2003), The CERT® Oracle® Secure Coding Standard for Java™ (Addison-Wesley, 2012), and Secure Coding in C and C++ (Addison-Wesley, 2013).


Dean F. Sutherland is a senior software security engineer at CERT. Dean received his Ph.D. in software engineering from Carnegie Mellon in 2008. Before his return to academia, he spent 14 years working as a professional software engineer at Tartan, Inc. He spent the last six of those years as a senior member of the technical staff and a technical lead for compiler backend technology. Dean is also a coauthor of The CERT® Oracle® Secure Coding Standard for Java™ (Addison-Wesley, 2012).


David Svoboda is a software security engineer at CERT/SEI. He also maintains the CERT Secure Coding standard websites for Java, as well as C, C++, and Perl. David has been the primary developer on a diverse set of software development projects at Carnegie Mellon since 1991, ranging from hierarchical chip modeling and social organization simulation to automated machine translation (AMT). David is also a coauthor of The CERT® Oracle® Secure Coding Standard for Java™ (Addison-Wesley, 2012).

Reader Review(s)

"This set of Java™ Coding Guidelines, a follow-on to the earlier The CERT® Oracle Secure Coding Standard for Java™, is invaluable. This book could almost be retitled Reliable Java™ Coding Guidelines. One of the things that has struck me over the years is the interplay between reliability and security. There are all sorts of explicit security tools—cryptography, authentication, and others—but most break-ins are exploitations of bugs: coding that was badly done or that was insufficiently defensive. Building a reliable system is, in many ways, equivalent to building a secure system. The work you do in reliability pays off in security, and vice versa.

"This book highlights the fact that security is not a feature; it is an attitude toward taking due care at every point. It should be a continuous part of every software engineer’s design thought process. It is organized around a list of guidelines. The meat of the book is the subtlety behind them. For example, “Store passwords using a hash function” appears to be a very basic and obvious point, and yet there are regular news articles about major data breaches just because some software engineer wasn’t thinking. Getting it right is tricky: there are a lot of details for the devil to hide in. This book is full of excellent guidance for dealing with those details."
—James A. Gosling