I spent Phase One of both my academic and professional careers working on hardware fault models and design for testability. In fact, the first static analysis tool I wrote was for hardware: it analyzed Verilog looking for design mistakes that would make it difficult or impossible to perform design verification or to apply adequate manufacturing tests. Some observations:
- The hardware guys are indeed ahead. Chip designers budget for test and verification from day one. They also do a fair amount of thinking about what's going to go wrong. Somebody's going to give you 5 volts instead of 3.3 volts. What's going to happen? The transistors are going to switch at a different rate when the chip is cold. What's going to happen? A speck of dust is going to fall on the wafer between the time the metal 2 layer goes down and the time the metal 3 layer goes down. What's going to happen? - The difference between a manufacturing defect and a design defect is not always immediately obvious. Maybe two wires got bridged because a piece of dust fell in exactly the right spot. Maybe two wires got bridged because you made a mistake in your process physics and you need 50 nm of tolerance instead of 0.5 nm. You'd better figure it out before you go into full-swing manufacturing, or big batches of defective chips could kill your profit margins and drive your customers away at the same time. For that reason, diagnosing the cause of failure is an important topic. Brian -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Chris Wysopal Sent: 02 February 2006 21:35 To: Gary McGraw Cc: William Kruse; Wall, Kevin; Secure Coding Mailing List Subject: RE: [SC-L] Bugs and flaws In the manufacturing world, which is far more mature than the software development world, they use the terminology of "design defect" and "manufacturing defect". So this distinction is useful and has stood the test of time. Flaw and defect are synonymous. We should just pick one. You could say that the term for manufacturing software is "implementation". So why do we need to change the terms for the software world? Wouldn't "design defect" and "implementation defect" be clearer and more in line with the manufacturing quality discipline, which the software quality discipline should be working towards emulating. (When do we get to Six Sigma?) I just don't see the usefulness of calling a "design defect" a "flaw". "Flaw" by itself is overloaded. And in the software world, "bug" can mean an implementation or design problem, so "bug" alone is overloaded for describing an implementation defect. At @stake the Application Center of Excellence used the terminology "design flaw" and "implementation flaw". It well understood by our customers. As Crispin said in an earlier post on the subject, the line is sometimes blurry. I am sure this is the case in manufacturing too. Architecture flaws can be folded into the design flaw category for simplicity. My vote is for a less overloaded and clearer terminology. -Chris P.S. My father managed a non-destructive test lab at a jet engine manufacturer. They had about the highest quality requirements in the world. So for many hours I was regaled with tales about the benefits of performing static analysis on individual components early in the manufacturing cycle. They would dip cast parts in a fluorescent liquid and look at them under ultraviolet light to illuminate cracks caused during casting process. For critical parts which would receive more stress, such as the fan blades, they would x-ray each part to inspect for internal cracks. A more expensive process but warranted due to the increased risk of total system failure for a defect in those parts. The static testing was obviously much cheaper and delivered better quality than just bolting the parts together and doing dynamic testing in a test cell. It's a wonder that it has taken the software security world so long to catch onto the benefits of static testing of implementation. I think we can learn a lot more from the manufacturing world. On Thu, 2 Feb 2006, Gary McGraw wrote: > Hi all, > > When I introduced the "bugs" and "flaws" nomenclature into the > literature, I did so in an article about the software security > workshop I chaired in 2003 (see http://www.cigital.com/ssw/). This > was ultimately written up in an "On the Horizon" paper published by > IEEE Security & Privacy. > > Nancy Mead and I queried the SWEBOK and looked around to see if the > new usage caused collision. It did not. The reason I think it is > important to distinguish the two ends of the rather slippery range > (crispy is right about that) is that software security as a field is > not paying enough attention to architecture. By identifying flaws as > a subcategory of defects (according the the SWEBOK), we can focus some > attention on the problem. > > >>From the small glossary in "Software Security" (my new book out > tomorrow): > > Bug-A bug is an implementation-level software problem. Bugs may exist > in code but never be executed. Though the term bug is applied quite > generally by many software practitioners, I reserve use of the term to > encompass fairly > simple implementation errors. Bugs are implementation-level problems > that > can be easily discovered and remedied. See Chapter 1. > > Flaw-A design-level or architectural software defect. High-level > defects cause 50% of software security problems. See Chapter 1. > > In any case, I intend to still use these terms like this, and I would > be very pleased if you would all join me. > > gem > > > _______________________________________________ Secure Coding mailing list (SC-L) SC-L@securecoding.org List information, subscriptions, etc - http://krvw.com/mailman/listinfo/sc-l List charter available at - http://www.securecoding.org/list/charter.php
