Defensive programming: Difference between revisions

Revision as of 18:49, 20 July 2005

Revision as of 12:46, 17 August 2005

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* One of the most common problems is unchecked use of constant-size structures and functions for dynamic-size data (the [[buffer overflow]] problem). This is especially common for [[string]] data in [[C programming language|C]]. C library functions like <tt>gets</tt> should never be used since the maximum size of the input buffer is not passed as an argument. <tt>gets()</tt> can be made safe, provided the programmer checks to make sure that he knows the size of the source string by calling <tt>strlen()</tt> or a similar function before calling <tt>gets</tt>.) C library functions like <tt>scanf</tt> can be used safely, but require the programmer to take care with the selection of safe format strings, by sanitising it before using it.

* Never make code more complex than necessary. Complexity breeds bugs, including security problems.

* Either leave the code available to everyone on the Net (see [[Free software]] or [[Open Source Definition]]) or hire someone who will perform a software [[security audit]].