The Mistakes Behind Most Breaches
The Caller Is Not Running Your Software
Last timeWhen Data Becomes an Instruction
A check in the page you shipped is a convenience for the honest. The caller can be a one-line command, and then only the checks on your side exist at all.
Whose software is calling
You wrote a page, or an application, and it contains checks. The quantity
must be at least one. The discount code must be valid. This button is
hidden unless the person is an administrator. The price shown is the price
from the catalogue.
Then you shipped that code to a machine somebody else owns, and the
situation is this: they can read it, edit it, delete the checks, or never
load it at all. The browser has a console. The application can be run
under a debugger. The traffic can be watched and replayed. And none of
that is even necessary, because the simplest approach skips your software
entirely and sends the request directly with a one-line command.
It is worth being precise about what this does and does not mean. The
checks in the shipped application are not useless and you should keep
writing them. They are a feature for honest users. They are simply not a
control, because a control is something the subject cannot remove.
Telling the two kinds apart
So each check in a feature is one of two things, and the test to tell
them apart is a single question: where does this run?
The lesson stops here
3 more paragraphs to go
You have read the opening. The rest of the argument, the problems that check whether it landed, and the lines worth keeping at the end all come with a plan.
The first lesson of every course in the library reads the whole way through, free, so you can see exactly what the rest of them are.
See the planThe contentsThis is the reading half
Starting the course gives you your own copy of it. Every idea on every page has problems standing under it, marked with a reason rather than a tick, and any sentence you do not believe can be opened and argued with. None of that can happen on a page nobody owns.
The contents