LWN.net Weekly Edition for November 11, 2004

An open source licensing white paper

The Olliance Group has announced the availability of a white paper entitled "Open Source Intellectual Property and Licensing Compliance: A Survey and Analysis of Industry Best Practices." The paper is available for free download to those willing to fill in a registration form.

The press release includes a recommendation from the president of the Free Standards Group, and the paper itself includes a foreward by OSDL head Stuart Cohen. So one might conclude that it would be a relatively high-clue work on how to interpret and comply with free software licenses. The sad truth, however, is that it appears to have been thrown together quickly (it contains a number of grammatical errors, for example), and the ultimate goals of its authors are unclear at best.

The purpose of the paper seems to be to help companies figure out how to avoid "open source risk." But that risk is not defined or justified anywhere in the paper. The closest it gets is toward the end, where we read:

In other words, we have the same old "the GPL can cause you to lose your intellectual property" argument. This line has been debunked numerous times: there is nothing in the GPL which can legally force a company to loosen its death grip in its valuable IP. The GPL can subject a non-compliant company to copyright infringement suits, fines, and injunctions stopping distribution of a product. These are real risks which should be understood by any company which is considering incorporating GPL-licensed code into its products. But it is discouraging to see representatives of the Free Standards Group and OSDL putting their names on a report that brings back the "lose all your IP" scarecrow.

Oh, there is one other risk mentioned on the same page:

In fact, the revocable nature of the GPL came out at the end of the KDE wars, when Richard Stallman revoked the right of the KDE developers to distribute the FSF's code, then magnanimously forgave them their sins:

The real point, however, is that revocability is certainly not a feature which is unique to free software licenses. Consider the Windows XP EULA:

Almost any proprietary software license includes a term like this one. Olliance's claim that such terms are unique to free software licenses is simply false.

So what does Olliance recommend be done to address those scary free software risks? The first step is to perform an audit of every free application in use in the company. Employees are to be required to document every program they use, its version numbers, the dates over which it has been used, the reason why it is used, the manager who approved its use, and so on. A database is then to be built containing all of that information. What then is to be done with this database is not entirely clear.

Some other "best practices" include:

• Requiring written approval by an "open source review board" before any open source application may be used.

• Requiring a separate approval before modifying any free software.

• Getting warranties from suppliers that they use no open source software, or that any such use is documented and indemnified.

In the midst of all this is a recommendation which actually makes sense:

OK, so maybe it doesn't make that much sense. The core of this recommendation is, however: think before you incorporate free software into your products. One could extend that to "think before you incorporate any software copyrighted by others into your products," but that would be asking a lot of the authors of this particular work.

As far as your editor can tell, the goal of this particular white paper is to stoke fears about open source licensing, and to urge companies to create a vast, grinding bureaucracy to impede the adoption of free software internally. Following its recommendations is unlikely to make many companies safer, but it will increase the apparent costs of using free software. There is a place for documentation of the real risks of using code copyrighted by others - both free and proprietary - and on how to avoid distributing products which violate free software licenses. But this paper does not fill that role.

Comments (8 posted)

Sendmail X

Sendmail has a difficult reputation. It is the canonical example of how large, complex programs are subject to security problems. It has a configuration file format which makes obfuscated Perl code seem highly readable by comparison. Its performance when dealing with large amounts of mail is held to be inferior. One could, of course, point out that sendmail's security problems appear to be mostly behind it, that few people ever have to look at the raw configuration file, and that sendmail was a cherished gift, once upon a time, to anybody who had ever tried to convince delivermail to route a message along a uucp bang path, by way of the Arpanet, from a CSNet node. For all of its blemishes, sendmail has been a crucial and valuable part of the network's infrastructure for many years.

After all those years, however, sendmail may just be due for a major upgrade. As it turns out, work on the next generation of sendmail, called sendmail X, has been under way for some time. Some early code has been made available; sendmail X 0.0.16 is available from this page. Do note that it is billed as "pre-alpha" code; using it on a server which handles real mail is probably not a good idea.

A lengthy design document for sendmail X is available; it gives some insight into what the next version of sendmail will look like. The first impression that comes out is that sendmail X will be so different that one wonders why the "sendmail" name is being used at all. Sendmail X is a completely new mail transfer agent, redesigned and rewritten from the beginning.

As is the norm for contemporary MTA design, sendmail X is implemented as a set of (relatively) small, cooperating processes. The system is divided in this way:

• The queue manager is the core of sendmail X; its job is to manage messages as they move through the system, make delivery decisions, etc.

• The SMTP server accepts incoming mail from the net and passes them to the queue manager. Actually, the queue manager is involved throughout the SMTP conversation; it is consulted on whether to accept the connection in the first place, and it may have actually delivered the mail before the text is acknowledged.

• The SMTP client passes mail on to other systems for delivery.

• The address resolver is charged with understanding - and rewriting - recipient addresses. This process also handles DNS blacklisting and other types of address-based filtering.

• The master control program gets all of the other processes going and handles termination, restarts, and crash recovery. This program is actually derived from the BSD inetd source.

In addition, there will be a collection of local delivery agents, mail filter processes, etc.

Much thought has been given to performance, to the point that may cause some to wonder if there might be some premature optimization going on. For example, the SMTP server has been designed to use an Apache-style mode, where multiple processes exist, each of which runs several server threads. This design will certainly add complexity to the server, but few sites are likely to benefit from the associated performance increase.

System administrators will be glad to know that the sendmail.cf configuration file is gone. Sendmail X will use a C-like configuration syntax, similar to that used by BIND. Configuration of real-world mail systems will, perhaps, never be an entirely simple task, but sendmail X should be easier to set up than its predecessor.

Unsurprisingly, security is said to be a core design goal. The multi-process design is clearly motivated by security concerns, though the relatively high level of interaction between these processes may complicate things. The qmail design, for example, has a far lower level of interaction and trust between its components - though that approach leads to problems of its own. There are no setuid programs in sendmail X. It is necessary to run the master control program as root; it then handles any privileged tasks that it can before starting the subsidiary processes under a different user ID. Thus, for example, it binds to the SMTP port before starting the SMTP server. Since the master control program does not actually handle mail or communicate with the outside, it should be relatively hard to compromise.

The code consists of almost 600 C files. In some ways it resembles the qmail code; it has many short files with reimplementations of many functions normally found in the C library. A special string type is used to avoid buffer overruns. A casual look suggests that the code really is being written with security in mind. That much new code is sure to have a surprise or two in it somewhere, however.

The author of sendmail X (Claus Aßmann) claims to have been running it since the beginning of the year without losing any mail. Even so, it will probably be some time before it is put forward as a viable option for production sites. What happens then will be interesting. Sendmail X will be jumping into an environment where several other options exist and are in wide use. The MTA ecosystem has, over the years, gone from being a single-program monoculture to a diverse field with several alternatives. Sendmail X will have to be significantly better than those alternatives, and much better than sendmail 8, to be widely successful in that environment.

(Thanks to Xose Vazquez Perez for drawing our attention to this project).

Comments (17 posted)

The state of RTAI

After the Approaches to realtime Linux article drew a great deal of interest, we decided to drill down and offer a closer look at one of the projects mentioned therein: The Real Time Application Interface (RTAI) project, whose developers felt that our portrayal of the project was not entirely accurate. To set things straight, we touched base with RTAI hackers Philippe Gerum and Paolo Mantegazza.

First, we learned that there are actually two ongoing projects, the first is the original RTAI project, funded by the Dipartimento di Ingegneria Aerospaziale, Politecnico di Milano (DIAPM). The other project is RTAI/Fusion, which is a different approach that merges the RTAI interfaces with the Xenomai development framework.

The RTAI project with Linux RealTime (LXRT) uses several kernel modules to gain the realtime functionality that one may need. RTAI makes changes in the Linux interrupt and scheduling policies to provide real time capabilities within the non-real time Linux environment. According to the RTAI website:

The original RTAI project was designed specifically for DIAPM projects, says Mantegazza:

On the other hand, Xenomai was designed to allow developers to port applications from other realtime systems, and therefore it takes a different approach. Gerum describes Xenomai as a "kind of generic RTOS (Real Time Operating System) core" that enable a developer to plug in their own real-time APIs. Gerum says the idea was that most RTOS vendors offer the same functionality, but with "different API window dressings." Xenomai was designed to "provide one generic core running side-by-side with the Linux kernel" that would allow for different APIs.

The RTAI/Fusion project that is now under development works with a "vanilla" Linux kernel running on top of the Adeos (Adaptive Domain Environment for Operating Systems) nanokernel. By running the Linux kernel and Fusion under the Adeos nanokernel, Fusion cooperates with Linux and allows developers to use "any number of real-time APIs at the same time."

Given that there are a number of real time projects for Linux, not to mention the other various RTOSes, we asked whether it would be possible to come up with a "one size fits all" solution for real time operating systems. Mantegazza says yes, but Gerum is not so sure:

It's important to note that RTAI/Fusion would not replace RTAI/LXRT so much as envelope it, if successful. According to Gerum, the plan is to "refactor the original RTAI 3.x interfaces over Fusion, if this technology is successful."

What's left to implement in Fusion? Gerum says there are several things left to be done:

Users that are interested in trying RTAI/Fusion can get a jump-start with Debian, which has RTAI packages in testing and unstable.

Though the Real Time market is a small niche of the Linux community, it's good to see healthy projects like RTAI/LXRT and RTAI/Fusion that will give Linux the opportunity to achieve the goal of world domination.

Comments (none posted)

Page editor: Jonathan Corbet

Inside this week's LWN.net Weekly Edition

• Security: Habeas returns; New vulnerabilities in Apache, dhcp, freeamp, gzip, kernel, samba, shadow, zip, ...
• Kernel: ABISS; Stackable security modules; Partitionable loop devices.
• Distributions: A First Look at Novell Linux Desktop 9
• Development: The Darcs Revision Control System, New versions of Berkeley DB, Samba, libDSP, Zope X3, Xen, gok, GNOME, FLU, Gtk#, Java-Gnome, Thunderbird, DSSI, Gnomoradio, Firefox, GCC, ECL, urwid, Conglomerate.
• Press: Debian and Trademarks, Software Patents in Standards, Firefox plans, SuperComputing 2004 trends, cluster companies find funding, The Open Gaming License, Novell's NLD-9 desktop.
• Announcements: Microsoft's protocol license agreement, Qtopia 2.1, Super Computing 2004 highlights, open source licensing whitepaper, Desktop Linux Summit, EclipseCon 2005 keynotes.

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