The product mixes trusted and untrusted data in the same data
structure or structured message.
Extended Description
By combining trusted and untrusted data in the same data structure, it
becomes easier for programmers to mistakenly trust unvalidated data.
Time of Introduction
Architecture and Design
Applicable Platforms
Languages
All
Demonstrative Examples
Example 1
The following code accepts an HTTP request and stores the username
parameter in the HTTP session object before checking to ensure that the user
has been authenticated.
(Bad Code)
Java
usrname = request.getParameter("usrname");
if (session.getAttribute(ATTR_USR) == null) {
session.setAttribute(ATTR_USR, usrname);
}
(Bad Code)
C#
usrname = request.Item("usrname");
if (session.Item(ATTR_USR) == null) {
session.Add(ATTR_USR, usrname);
}
Without well-established and maintained trust boundaries, programmers
will inevitably lose track of which pieces of data have been validated
and which have not. This confusion will eventually allow some data to be
used without first being validated.
Other Notes
A trust boundary can be thought of as line drawn through a program. On one
side of the line, data is untrusted. On the other side of the line, data is
assumed to be trustworthy. The purpose of validation logic is to allow data
to safely cross the trust boundary--to move from untrusted to trusted. A
trust boundary violation occurs when a program blurs the line between what
is trusted and what is untrusted. The most common way to make this mistake
is to allow trusted and untrusted data to commingle in the same data
structure.
Description
