Some suggestions on how to write more safe and secure programs

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This paper presents a list of suggestions on how to avoid the most common pitfalls that make software less secure or less safe than it should be. It is addressed to software developers and covers the phases of software design, implementation, and testing. It focuses on network application programs, but many of the suggestions are equally valid for other kinds of software.

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Table of Contents

Introduction

Design

Design with security and safety in mind
Design for quality
Use formal methods and languages
Limit software complexity
Ensure that all the operations (both normal and exceptional) in your application are safe and secure
Use only well-known cryptographic algorithms
Don't assume that you can increase security by keeping the source code of your algorithms hidden
Don't rely on the users of your application to select the appropriate (more secure) security settings
Verify exchanged digital certificates and involve the user as much as possible in this process
Limit the internal data redundancy and manage the existing redundancy

Implementation

Ensure that the program doesn't try to read or write data outside an allocated memory block (buffer overflow)
Ensure that all resource allocation errors are detected and handled
Ensure that the program's stack never overflows
Check boundary conditions
Use tools for checking the correctness of the program's code
Limit use of privileged modes during program execution
When processing an input message, check that the message can be safely decoded and that its contents are valid
When processing an input message, limit the resources (memory, disk space, CPU time) used for the message.
Make generous use of assertions in your code
Use restrictive language features extensively
Compile with the highest warning level

Testing

Use system-stress simulation techniques during program testing
Use a multiprocessor computer during program testing
Ensure that the entire program code is executed during program testing

Resources

Contact for comment/discussion:

Mr. Alessandro TRIGLIA

sandro@oss.com