Improper input validation: Difference between revisions

Revision as of 12:20, 29 November 2007

Revision as of 21:54, 25 December 2007

Line 1:

{{Cleanup|date=March 2006}}

[[String (computer science)|String]] programming is believed to be easy by programmers. This is hower not the case: severalSeveral implementation / design flaws are associated with [[String (computer science)|string]] programming, some of those are associated with [[security exploitsexploit]]s.

== Canonicalization problems ==

Software programmers often assume that strings are canonical. This a fallacy.

=== Example: HTML tags are not canonical ===

Fallacy:

"<code><nowiki><script></nowiki></code>" can only be written as "<code><nowiki><script></nowiki></code>"

This is not true. Many HTML processors will accept "<code><nowiki><</nowiki>'''SPACE'''<nowiki>script></nowiki></code>" or "<code><nowiki><</nowiki>'''NUL'''<nowiki>script></nowiki></code>"

== Concatenation problems ==

A lot of people believe that

It is possible to cause ''String1 + User_Input_String + String2'' to behave in unepected ways by by crafting unanticipated User_Input_String, such as having string2 ignored in processing.

will behave in some sort of controlled manner. This is not true.

=== String termination ===

Line 28 ⟶ 20:

* Unix shells: '''#''' means ignore rest of line

== RelatedSee articlesalso (other string problems) ==

* [[Format string attack]] - *printf format strings are dangerous

* [[Buffer overflow]] - Buffer overflows often occurs in unsafe string functions