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Secure Programming Cookbook for C and C++
The Target Audience of the Book In the foreword to this book Gene Spafford observes that there really are four types of programmers:
- Those who are constantly writing buggy code, no matter what,
- Those who can write reasonable code, given coaching and examples,
- Those who write good code most of the time, but who don't fully realize their limitations,
- Those who really understand the language, the machine architecture, software engineering, and the application area, and who can write textbook code on a regular basis.
There are, as Spafford claims, too many people in category 3 who think they belong to the category 4, and that's the primary target audience of the book. John Viega and Matt Messier co-wrote Secure Programming Cookbook for C and C++ not with the intent of proving the necessity of application security, as they mention in the foreword, but to illustrate its application. If you're reading this book, you are probably well aware of the security needs at your workplace or in your projects, and you would like to have a large library of sample code for various operations.
The book has yet another Web site, and since John Viega didn't mind a little slashdotting during the launching stage, so he probably won't mind another link to SecureProgramming.com.
The Book Itself The structure of the book will be familiar to anyone who has read an O'Reilly Cookbook before. The "cookbook" part of the text is nothing more than a collection of solutions to common problems. The code is generally of high quality and written by an expert in the field. What's more important is the discussion section following the code, which explains why things are done in a certain way, what alternatives exist, and what are the best practices in the field.Viega and Messier have expanded the discussion session, basically doubling the content, by introducing separate Windows and Unix sections where applicable. The reader has a chance to peruse the code for both platforms as well as read separate discussion sections, which helps in navigating the content of the book.
Microsoft platform developers, though, will only be introduced to native Win32 API -- the authors chose to ignore the STL/ATL/COM/DCOM/.NET solutions on the assumption that those could be derived by someone closely familiar with the lowest-level API available from Microsoft. Even though the discussion section is quite detailed and informative for both Unix and Windows developers, the authors do not discuss the design and architecture issues behind secure programming in C and C++. That falls outside the scope of this book; besides, John Viega co-authored Building Secure Software , where a lot of attention is paid to the philosophy of secure programming as well as initial application design with security in mind.
The Contents You can view the table of contents on the O'Reilly Publishing Web site, and with the cookbook format, it's pretty much WISYWIG -- whatever the title of the subchapter is, you will be introduced to the nature of the problem, followed by C/C++ solution, followed by the discussion of the subject with occasional URLs to relevant information on the Web.
Just to sum it up, usage of encryption, message integrity checks, symmetric and public-key cryptography and secure programming get a lot of attention. With 41 recipes (Chapters 4 and 5) on symmetric encryption and 29 (Chapters 7 and 10)on PKI-related code snippets, you can get your yearly supply of Unix and MS CryptoAPI examples.
But this book is not entirely about encryption, since current security problems are rarely caused by the encryption algorithm failures. The networking and Internet-related programming issues are covered in Chapter 8 (Authentication) and Chapter 9 (Networking). In Chapter 3, those designing Web interfaces will find some useful examples of validating the input URL and checking the SQL string against injection attacks. Admittedly, such examples would serve a better purpose in Perl/PHP/ASP, however, anyone familiar with C should be able to derive their own variations of the algorithm. Chapters 1 and 2 provide a great deal of insight into operating system specifics in regards to such system security issues as environment variables, spawning child processes, revealing memory dumps, using temp files on Windows and Unix, etc.
Off-the-beaten-path chapters include information on random numbers (the chapter is available online for free) and preventing tampering with applications. The random number chapter would be interesting to both professional programmers with good math skills and beginners in the computer programming field writing their first number-guessing C++ game. Recipes on gathering entropy and access to standard Windows/Unix APIs for random number generation are of great practical use. The application tampering chapter was probably the most informative thing for me - great collection of information, rarely found in other application or network security publications. How do you protect against software piracy by using checksums? How much time should you dedicate to software protection? What is the theory behind code obfuscation? How do you hide ASCII strings in data segment? How do you detect modern debuggers? The answers to such questions are usually fragmentary and are usually considered either intellectual property of the company or belong to a 'warez' site, where the quality of sources is questionable.
Is the Book Useful? This book is a great resource for quick look-up of readily available solution (I've read it online on Safari, so I cannot vouch for the usability of the paper edition when searching for information). I've written a Master's thesis on this topic (although my actual topic was way more narrow than the scope of this book) and still found a lot of great information. If you've never seen C/C++ code or feel uncomfortable with Unix/Windows API programming, you will probably find the Cookbook overly technical. A higher-level application security text is available for those new to the subject (besides the Building Secure Software title mentioned above, there's a great title called Writing Secure Code from Microsoft), while this book gets into dirty, nitty-gritty details.
Yeah, everyone and his brother knows how to implement a symmetric encryption algorithm, but how do you actually do it without compromising the system and introducing new possible loopholes? The cookbook answers questions like that, and, as mentioned above, provides detailed overview of programming strategies for the two most popular platforms. Taking the cookbook concept further, this book teaches you how to make a basic ham-and-cheese sandwich as well as fine cuisine. Too often the code measures for basic security and preventing buffer overflows are summarized in higher-level concepts, thus allowing the developers to make errors even with the most trivial applications. If you're a professional programmer and do not get tired by looking at sometimes profuse code examples, this book would probably be a good read from the beginning to the end. If C/C++ is not your preferred area, the usefulness of this title decreases severely, however, it might serve as a good reference.
You can purchase Secure Programming Cookbook for C and C++ from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
I would send a free copy to openssl staff
int main(void)
{
system("python mainapp.py");
return 0;
}
there are too many people in catagory 1 that think they are in catagory 4.
funny enough, if there code was a hurricane, it would be at least a catagory 4.
The Kruger Dunning explains most post on
- Those who are constantly writing buggy code, no matter what,
-
Those who can write reasonable code, given coaching and examples,
-
Those who write good code most of the time, but who don't fully realize their limitations,
-
Those who really understand the language, the machine architecture, software engineering, and the application area, and who can write textbook code on a regular basis.
There are, as Spafford claims, too many people in category 3 who think they belong to the category 4, and that's the primary target audience of the book.Well, I don't need this, since I'm in category 4. Instead of reading this nonsense, I'll go finish my Visual Basic project.
There is a fifth type of programmer, not covered by the categorization mentioned above: Those who really understand the language, the machine architecture, software engineering, and the application area, and who write code which is absolutely antithetical to anything you'd find in a textbook.
I, for example, severely abuse short-circuit evaluation -- I'll often put five or more function calls into an if() conditional, ||ing their error conditions together -- but there's nothing wrong with that; you'll never find it in a textbook, but once you're used to reading that sort of code, it is more compact, easy to understand, and easy to maintain than the alternatives.
Tarsnap: Online backups for the truly paranoid
There are, as Spafford claims, too many people in category 3 who think they belong to the category 4, and that's the primary target audience of the book
:-)
People who think they are in category 4 wont buy the book, because they belive they dont need it. So who is the target audience anyway?
There are 4 types of programming book authors:
...
1. Those who categorize programmers artificially for the sake of a point.
2. Those who categorize programmers incorrectly because they don't know better, but for good reason.
3. Those who categorize programmers because they figure that, by doing so, they will establish themselves as an authority on ranges and types of programming skill.
4. Those who avoid categorizing programmers because they realize that it's kind of goofy to do so.
Everyone knows that there are folks out there that can do their job better than others. But do those categories really exist? It may seem like I'm picking nits, but is there really a class of programmers that writes buggy code almost all of the time? I mean, I suppose there is, but it doesn't seem to me like they'll have a long career in software
Chr0m0Dr0m!C
I read the sample chapter and the table of contents, and this certainly looks like a very useful book for developers.
/dev/urandom. ... I wonder if this book is out on Safari yet.
The random number generation chapter is excellent. Many people overlook this necessity in cryptographic applications unaware that flaws introduced by insecurely random (i.e. predictable) enrtropy sources can render the best PKI, ciphers and authentication mechanisms crippled.
One of the reasons I tend to drool over VIA hardware is that their MiniITX EPIA systems have support for hardware entropy on the CPU via the Nehemiah core, which is also available for a wide variety of OEM/embedded applications.
This means you can use a highly secure entropy source (/dev/hw_random in linux for example) for all of your cryptographic applications, from GPG to ssh to the linux kernel itself (IPSEC). And best of all, you never have to worry about the entropy pool blocking, or reverting to less secure PRNG like
I'll tell it out loud flatly, the reason is because it's not a "my system is better then your system" kind of book from what it seems. Those are the books that annoy me the most "Well, you see, you could be using ASP, but then your app would be WAAAAAY more insecure."
On top of that, actually seeing equivalents of the same code on both system families will be a nice intro to some, including me, for equivalent APIs that we didn't know existed in other systems.
Btw, the Secure Coding book by microsoft is really good too (very few actual API references, so it's not really microsoft platform targeted).
OPEN Skull, and poke around with stick.
How much does the programming language matter?
Posted by John Viega on Mon, Sep 15, 2003 (07:59 AM) GMT
We've now been slashdotted. After lowering the idle connection timeout from hours to minutes, we're doing fine (famous last words). The comments are full of "C sucks" rants. I thought I'd summarize a few of my thoughts on this issue.
Yes, C and C++ have special "features" that make adding security problems easy, even for a fairly informed and careful developer. That's impossible to deny, though the book and this site do cover mitigation strategies that can make a big difference. However, people are miscalculating by assuming that just switching to another programming language is going to make a big difference. It can make a difference, but not as big of one as people are expecting. Defensive practices can offset the problem.
We've done a few case studies on number of defects per line of code when performing code audits. C and C++ programs have averaged 4-5 security-critical defects per thousand lines of code. Java programs still average 1-2 security-critical defect per thousand lines.
There are plenty of problems that programming languages themselves haven't fixed. And, honestly, most of those problems should be fixed at the API level. For example, it's stupid that neither OpenSSL or Microsoft supports full certificate validation by default. The programmer has to know what security checks to perform and write the code to do them manually, instead of getting "secure by default" behavior. As a result, most applications that use SSL/TLS are vulnerable to man-in-the-middle attacks. Sure, this is a problem in some common C-based libraries, but it's just as common in the SSL implementations for other languages. Other problems such as cross-site-scripting and SQL injection affect other languages far more commonly than C and C++, since those languages aren't often used in web apps.
In C and C++, the common security problems are relatively easy to understand, and if you are diligent and take the right preventative measures, they're not so hard to avoid. In other languages, the easy/obvious problems don't apply, but as people use high-level primitives to build complex applications, they tend to introduce complex security problems (race conditions in servlets can be quite tough to identify, and still have security implications).
In short, you aren't likely to accidentally end up with a "secure" program, no matter which programming language you use. We're currently working on a Java Secure Programming Cookbook, and are assembling a team for a PHP Secure Programming Cookbook. There's plenty of material for both books, without question. Expect both to be at least 400 pages, without even covering all of the low-level cryptographic stuff we cover in the C/C++ version.
At the end of the day, if you're going to be diligent, then security can be reduced to a fairly minor consideration in programming language choice.
One final note: C++ is often perceived as being more secure than C, because it has an abstracted string type. That's not really true, even ignoring the few cases where you can still overflow using C++ strings. Basically, heap overflows are far more dangerous in C++, because lots of function pointers tend to be stored on the heap, due to the way classes and exception handling is implemented (the GOT is stored on the heap even in C programs, but C++ programs tend to have function pointers coming out of the wazoo). If an attacker can overwrite one of those pointers, then it's often possible that he can replace it with a pointer to some sort of malicious payload.
Thanks for the good review. A few minor points:
1) All of the book's code is available on our web site. The web site is probably the right place to go to to get the code, just because we can update it when there are errata (and you don't have to copy it out manually if you want to use it).
2) This is an implementation-focused book. You're right to refer to other texts for architecture, and besides my other book, the Microsoft press book you recommend and David Wheeler's free online HOWTO are both excellent (though I personally think the O'Reilly entry into that space is poor). At the same time, we do end up covering many aspects of good architecture in the discussion. Providing the context for a good implementation requires an understanding of the architectural issues, at least to some degree.
3) We have had several people tell us that they find the book very useful for other languages as well. I think it covers a lot of low-level implementation stuff that isn't available in other books, and is useful as long as you can READ C code. If there's anything people want to see for other languages, etc., feel free to send us email suggesting it. We will have frequent updates to this web site with new content (at least monthly). Much of the content will be for other languages.