Today on the show, we’ve got a look at running OpenBSD on a APU, some BSD in your Android, managing your own FreeBSD cloud service with ansible and much more. Keep it turned on your place to B...SD!

The driver used for wireless networking is athn(4). It might not work properly out of the box. Once OpenBSD is installed, run fw_update with no arguments. It will figure out which firmware updates are required and will download and install them. When it finishes, reboot.

Earlier this year, we announced that we started using the bsdiff algorithm (by Colin Percival). Using bsdiff, we were able to reduce the size of app updates on average by 47% compared to the full APK size.

Today, we're excited to share a new approach that goes further — File-by-File patching. App Updates using File-by-File patching are, on average, 65% smaller than the full app, and in some cases more than 90% smaller.

A far more sophisticated algorithm, which typically provides roughly 20% smaller patches, is described in my doctoral thesis.

Most of the NAS operating systems I have used in the past were built around useful features. Some focused on making storage easy to set up and manage, others focused on services, such as making files available over multiple protocols or managing torrents. Some strive to be very easy to set up. NAS4Free does pretty well in each of the above categories. It may not be the easiest platform to set up, but it's probably a close second. It may not have the prettiest interface for managing settings, but it is quite easy to navigate. NAS4Free may not have the most add-on services and access protocols, but I suspect there are more than enough of both for most people.

Where NAS4Free does better than most other solutions I have looked at is security. I don't think the project's website or documentation particularly focuses on security as a feature, but there are plenty of little security features that I liked. NAS4Free makes it very easy to lock the text console, which is good because we do not all keep our NAS boxes behind locked doors. The system is fairly easy to upgrade and appears to publish regular security updates in the form of new firmware. NAS4Free makes it fairly easy to set up user accounts, handle permissions and manage home directories. It's also pretty straight forward to switch from HTTP to HTTPS and to block people not on the local network from accessing the NAS's web interface.

All in all, I like NAS4Free. It's a good, general purpose NAS operating system. While I did not feel the project did anything really amazing in any one category, nor did I run into any serious issues. The NAS ran as expected, was fairly straight forward to set up and easy to manage. This strikes me as an especially good platform for home or small business users who want an easy set up, some basic security and a solid collection of features.

Pipes are supported with pipe(2) enabling developers to compose processes into pipelines.

Sockets include support for TCP socket servers and clients, making it possible to run applications like databases and HTTP servers together with their clients in the browser.

Linux, FreeBSD, and Unix-like systems are multi-user and need some way of authenticating individual users. Back in the old days, this was done in different ways. You need to change each Unix application to use different authentication scheme.

So Open Group lead to the development of PAM for the Unix-like system. Today Linux, FreeBSD, MacOS X and many other Unix-like systems are configured to use a centralized authentication mechanism called Pluggable Authentication Modules (PAM). The book “PAM Mastery” deals with the black magic of PAM.

The book starts with the basic concepts about PAM and authentication. You learn about Multi-Factor Authentication and why use PAM instead of changing each program to authenticate the user. The author went into great details about why PAM is useful for developers and sysadmin for several reasons. The examples cover CentOS Linux (RHEL and clones), Debian Linux, and FreeBSD Unix system.

I like the way the author described PAM Configuration Files and Common Modules that covers everyday scenarios for the sysadmin. PAM configuration file format and PAM Module Interfaces are discussed in easy to understand language. Control flags in PAM can be very confusing for new sysadmins. Modules can be stacked in a particular order, and the control flags determine how important the success or failure of a particular module.

There is also a chapter about using one-time passwords (Google Authenticator) for your application.

The final chapter is all about enforcing good password policies for users and apps using PAM.

The sysadmin would find this book useful as it covers a common authentication scheme that can be used with a wide variety of applications on Unix. You will master PAM topics and take control over authentication for your organization IT infrastructure. If you are Linux or Unix sysadmin, I would highly recommend this book. Once again Michael W Lucas nailed it. The only book you may need for PAM deployment.

Ken Thompson's "cc hack" - Presented in the journal, Communication of the ACM, Vol. 27, No. 8, August 1984, in a paper entitled "Reflections on Trusting Trust", Ken Thompson, co-author of UNIX, recounted a story of how he created a version of the C compiler that, when presented with the source code for the "login" program, would automatically compile in a backdoor to allow him entry to the system. This is only half the story, though. In order to hide this trojan horse, Ken also added to this version of "cc" the ability to recognize if it was recompiling itself to make sure that the newly compiled C compiler contained both the "login" backdoor, and the code to insert both trojans into a newly compiled C compiler. In this way, the source code for the C compiler would never show that these trojans existed.

The C compiler is written in C. What I am about to describe is one of many "chicken and egg" problems that arise when compilers are written in their own language. In this case, I will use a specific example from the C compiler.

Suppose we wish to alter the C compiler to include the sequence "\v" to represent the vertical tab character. The extension to Figure 2 is obvious and is presented in Figure 3. We then recompile the C compiler, but we get a diagnostic. Obviously, since the binary version of the compiler does not know about "\v," the source is not legal C. We must "train" the compiler. After it "knows" what "\v" means, then our new change will become legal C. We look up on an ASCII chart that a vertical tab is decimal 11. We alter our source to look like Figure 4. Now the old compiler accepts the new source. We install the resulting binary as the new official C compiler and now we can write the portable version the way we had it in Figure 3.

The actual bug I planted in the compiler would match code in the UNIX "login" command. The replacement code would miscompile the login command so that it would accept either the intended encrypted password or a particular known password. Thus if this code were installed in binary and the binary were used to compile the login command, I could log into that system as any user. Such blatant code would not go undetected for long. Even the most casual perusal of the source of the C compiler would raise suspicions.

Next “simply add a second Trojan horse to the one that already exists. The second pattern is aimed at the C compiler. The replacement code is a Stage I self-reproducing program that inserts both Trojan horses into the compiler. This requires a learning phase as in the Stage II example. First we compile the modified source with the normal C compiler to produce a bugged binary. We install this binary as the official C. We can now remove the bugs from the source of the compiler and the new binary will reinsert the bugs whenever it is compiled. Of course, the login command will remain bugged with no trace in source anywhere.

So now there is a trojan’d version of cc. If you compile a clean version of cc, using the bad cc, you will get a bad cc. If you use the bad cc to compile the login program, it will have a backdoor. The source code for both backdoors no longer exists on the system. You can audit the source code of cc and login all you want, they are trustworthy.

The compiler you use to compile your new compiler, is the untrustworthy bit, but you have no way to know it is untrustworthy, and no way to make a new compiler, without using the bad compiler.

The moral is obvious. You can't trust code that you did not totally create yourself. (Especially code from companies that employ people like me.) No amount of source-level verification or scrutiny will protect you from using untrusted code. In demonstrating the possibility of this kind of attack, I picked on the C compiler. I could have picked on any program-handling program such as an assembler, a loader, or even hardware microcode. As the level of program gets lower, these bugs will be harder and harder to detect. A well installed microcode bug will be almost impossible to detect.

Acknowledgment: I first read of the possibility of such a Trojan horse in an Air Force critique of the security of an early implementation of Multics. I can- not find a more specific reference to this document. I would appreciate it if anyone who can supply this reference would let me know.

From December the 27th until the 30th there the 33rd Chaos Communication Congress[0] is going to take place in Hamburg, Germany. Think of it as the yearly gathering of the european hackerscene and their overseas friends. I am one of the persons organizing the "BSD assembly" as a gathering place for BSD enthusiasts and waving the flag amidst the all the other projects / communities.