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GPL Workshop
How to (not?) use Free Software


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by

Harald Welte <laforge@gpl-violations.org>



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How to (not) use GPL Software
Contents

	About the speaker
	Ideas / Goals of the GPL
	How to (not) use GPL Software
	Complete Source Code
	Derivative Works
	Collective Works
	GPL and Embedded Systems
	The biggest GPL Myths
	Thanks

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How to (not) use GPL Software
Introduction


Who is speaking to you?

		an independent Free Software developer
		who earns his living off Free Software since 1997
		who is one of the authors of the Linux kernel firewall system called netfilter/iptables
		who has started gpl-violations.org to enforce license compliance
		who IS NOT A LAWYER

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How to (not) use GPL Software
Disclaimer

Legal Disclaimer

		All information presented here is provided on an as-is basis
		There is no warranty for correctness of legal information
		The author is not a lawyer
		This does not comprise legal advise
		The authors' experience is limited to German copyright law

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How to (not) use GPL Software
Ideas and Goals of the GNU GPL

	Free Software
		Software that has fundamental freedoms:
			to use it for any purpose
			to "help your neighbour" (i.e. make copies)
			to study it's functionality (reading source code)
			to fix it myself (make modifications and run them)

	Copyleft
		Is the legal idea to 
			exercising copyright to grant the above freedoms
			assure that nobody can take away the freedom

	The GNU General Public License
		Is a legal instrument to apply they copyleft idea on software


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The GNU GPL revisited

Revisiting the GNU General Public License
	Regulates distribution of copyrighted code, not usage
	Allows distribution of source code and modified source code
		The license itself is mentioned
		A copy of the license accompanies every copy
	Allows distribution of binaries or modified binaries, if
		The license itself is mentioned
		A copy of the license accompanies every copy
		The complete source code is either included with the copy (alternatively a written offer to send the source code on request to any 3rd party)

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Complete Source Code

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"... complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable."

	For standard C-language programs, this means:
		Source Code
		Makefiles
		compile-time Configuration (such as kernel .config)

	General Rule:
		Intent of License is to enable user to run modified versions of the program.  They need to be enabled to do so.


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Derivative Works

	What is a derivative work?
		Not dependent on any particular kind of technology (static/dynamic linking, dlopen, whatever)
		Even while the modification can itself be a copyrightable work, the combination with GPL-licensed code is subject to GPL.
		As soon as code is written for a specific non-standard API (such as the iptables plugin API), there is significant indication for a derivative work
		This position has been successfully enforced out-of-court with two Vendors so far (iptables modules/plugins).

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Derivative Works

	Binary-only kernel modules
		In-kernel proprietary code (binary kernel modules) are hard to claim GPL compliant
		Case-by-case analysis required, as the level of integration into the GPL licensed kernel code depends on particular case
		IBM is in the process of getting rid of all binary-only kernel modules.  There are exceptions, but they are very clear ones (such as a filesystem port to linux, where the filesystem code already existed under another OS)
		There is no general acceptance or tolerance to binary-only kernel modules in the Linux (development) community.  Not even Linus himself has ever granted an exception for such modules!


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Derivative Works

	Glue Code
		Acts as glue layer between GPL licensed code and proprietary code
		Some Vendors think they can avoid the GPL by doing so
		Is definitely not a bullet-proof legal solution, especially when it is clearly visible that the only purpose of this glue code is to "get rid" of the GPL.

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Derivative Works

	Moral Issues
		Apart from what is legally possible, there are moral issues
		Even if in a particular case there is no legal way to claim a binary-only kernel module is a derivative work, you might still be acting against the authors' wishes
		By shipping binary-only kernel modules, you violate the "moral code of conduct" of the Free Software community
		But it is the work of this very community that enables you to build your product based on Free Software
		Such action might have long-term detrimental effects on the motivation of FOSS developers (dissatisfaction, demotivation, ...)

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Collective Works

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"... it is not the intent .. to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works ..."

	GPL controls "collective works"

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"... mere aggregation of another work ... with the program on a volume of a storage or distribution medium does not bring the other work und the scope of this license"

	GPL allows "mere aggregation"
		like a general-porpose GNU/Linux distribution (SuSE, Red Hat, ...)


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GPL And Embedded Systems

	Historical background:
		The GPL was written for userspace programs running on existing operating systems
		Covering a whole OS (and even userspace programs) is not an ideal match, but if you read it carefully it still makes sense

	Toolchain:
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"... the source code distributed need not include anything that is normally
distributed (in either source or binary form) with the major components
(compiler, kernel, and so on) of the operating system on which the executable
runs, unless that component itself accompanies the executable."
		Practical case:
			You've modified gcc for a specific embedded platform
			Therefore, this gcc is not "normally distributed with the operating system" and you have to distribute it together with the source code
			gcc itself is covered under GPL, so you need to provide binaries and source code(!)


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GPL And Embedded Systems

	The "Scripts"
		(scripts to control compilation and installation, see earlier slide)
		In case of embedded hardware, the "scripts" include:
			Tools for generating the firmware binary from the source (even if they are technically no 'scripts')


	Embedded DRM
		Intent of License is to enable user to run modified versions of the program.  They need to be enabled to do so.
		Result: Signing binaries and only accepting signed versions from the bootloader (without providing the signature key or a possibility to set a new key in the bootloader) is not acceptable!


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Practical Source Code Offer

	Some Rules
		The "complete corresponding source code" has to be made available 
		It has to be made available for each and every object-code version that was distributed
		If you strip down the source code offer (e.g. remove proprietary source code), try to see whether the result actually compiles
		If the product is mixed free / proprietary software, consider including the proprietary parts (as object code) in the "source code package", so the full firmware image can be rebuilt without having to tear apart an existing image and ripping out those proprietary programs from there.


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The biggest myths about the GPL

The biggest myths about the GPL
	The GPL is not enforcible
	Software licensed under GPL has no copyright
	Unmodified distribution does not require source code availability
	The vendor can wait for a source code request (without offering it)

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The most common mistakes

The most common mistakes
		not even once reading the GPL text and/or the FAQ from the FSF
		not including the GPL license text with the product
		not including a written offer with the product
		not considering that the GPL also applies to software updates
		only providing original source code (e.g. vanilla kernel.org kernel)
		not including the "scripts to control installation"
		only providing off-site hyperlinks to license and/ore source code
		not responding to support requests for source code
		charging rediculously high fees for physical shipping of source code

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License Compatibility

	There's lots of Free Software available
		Different Software uses different Licenses:
			Linux: GPL
			glibc: LGPL
			apache: Apache Software License
			Perl: Artistic
			ucd-snmp: BSD
		If you combine (i.e. link) differently-licensed software,
			check license compatibility
			in case of doubt, ask legal person and/or contact software authors
			authors might give you an exception or consider making licenses compatible


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Dual Licensing

	The copyright holder (often the original author) can provide alternative licensing
	Some projects do this as a business model (reiserfs, MySQL)
	In some projects it's impossible due to the extremely distributed copyright (e.g. Linux kernel)
	However, in smaller projects it never hurts to ask whether there would be interest in providing an alternative (non-copyleft) licensing

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The GNU GPL Revisited
GPL Violations

	When do I violate the license
		when one ore more of the obligations are not fulfilled

	What risk do I take if I violate the license?
		the GPL automatically revokes any usage right
		any copyright holder can obtain a preliminary injunction banning distribution of the infringing product

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Past GPL enforcement

Past GPL enforcement

		GPL violations are nothing new, as GPL licensed software is nothing new.
		However, the recent GNU/Linux hype made GPL licensed software used more often
		The FSF enforces GPL violations of code on which they hold the copyright
			silently, without public notice
			in lengthy negotiations

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The Linksys case


	During 2003 the "Linksys" case drew a lot of attention
		Linksys was selling 802.11 WLAN Acces Ponts / Routers
		Lots of GPL licensed software embedded in the device (included Linux, uClibc, busybox, iptables, ...)
		FSF led alliance took the usual "quiet" approach 
		Linksys bought itself a lot of time
		Some source code was released two months later
		About four months later, full GPL compliance was achieved

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The Linksys case

	Some developers didn't agree with this approach
		not enough publicity
		violators don't loose anything by first not complying and wait for the FSF
		four months delay is too much for low product lifecycles in WLAN world
	The netfilter/iptables project started to do their own enforcement in more cases that were coming up

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Enforcement case timeline

	In chronological order
		some user sends us a note he found our code somewhere
		reverse engineering of firmware images
		test purchase to verify device ships gpl-incompliant
		sending the infringing organization a warning notice
		wait for them to sign a statement to cease and desist
		if no statement is signed
			contract technical expert to do a study
			apply for a preliminary injunction
		if statement was signed
			try to work out the details 
			grace period for boxes in stock possible
			try to indicate that a donation would be good PR

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Sucess so far

	Success so far
		amicable agreements with a number (35+) of companies
			some of which made significant donations to charitable organizations of the free software community
		preliminary injunction against Sitecom, Sitecom also lost appeals case 
		court decision of munich district court in Sitecom appeals case
		three more preliminary injunctions 
		more settled cases (not public yet)
		negotiating in more cases
		public awareness 

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Cases so far (1/3)


		Allnet GmbH
		Siemens AG
		Fujitsu-Siemens Computers GmbH
		Axis A.B.
		Securepoint GmbH
		U.S.Robotics Germany GmbH
		Netgear GmbH
		Belkin Compnents GmbH
		Asus GmbH
		Gateprotect GmbH
		Sitecom GmbH / B.V.
		TomTom B.V.
		Gigabyte Technologies GmbH

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Cases so far (2/3)


		Sun Deutschland GmbH
		Open-E GmbH
		Siemens AG (second case)
		Deutsche Telekom AG
		Hitachi Inc.
		Tecom Inc.
		ARP Datacon GmbH
		Conceptronic B.V.
		D-Link GmbH
		Adaptec Deutschland GmbH
		Belkin Compnents GmbH (second case)

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Cases so far (3/3)


		Siemens AG (third case)
		TARGA GmbH
		Medion AG
		naviflash GmbH
		Maxtor Inc.
		Cisco Deutschland GmbH
		Fortinet
		naviflash GmbH
		iRiver Europe GmbH
		Cisco Deutschland GmbH (second case)
		Acer Deutschland GmbH
		SMC Networks GmbH

		>= 100 more not public


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What we've learned


	Copyleft-style licenses can be enforced!
	A lot of companies don't take Free Software licenses seriously
		Even corporations with large legal departments who should know
		Reasons unclear, probably the financial risk of infringement was considered less than the expected gains
	The FUD spread about "GPL not holding up in court" has disappeared



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Future GPL Enforcement


	GPL Enforcement
		remains an important issue for Free Software
		will start to happen within the court more often
		has to be made public in order to raise awareness
		will probably happen within some form of organization
		talks have started with the FSF Europe

	What about Copylefted Content (Creative Commons)
		probably just a matter of time until CC-licensed works of art are infringed

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Problems of GPL Enforcement

	Problems
		distributed copyright
			is an important safeguard
			can make enforcement difficult, since copyright traditionally doesn't know cases with thousands of copyright holders
			distribution of damages extremely difficult
		the legal issue of having to do reverse engineering in order to prove copyright infringement(!)
		only the copyright holder (in most cases the author) can do it
		users discovering GPL'd software need to communicate those issues to all entitled parties (copyright holders)
		infringers obfuscating and/or encrypting fres software as disguise

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gpl-violations.org

	The http://www.gpl-violations.org/ project was started ~ 3 year ago
		as a platform wher users can report alleged violations
		to verify those violations and inform all copyright holders
		to inform the public about ongoing enforcement efforts
	
	At the moment, project is only backed by the author
		more volunteers needed to investigate all cases
		something like 270 reported (alleged) violations backlog

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Make later enforcement easy

	Practical rules for proof by reverse engineering
		Don't fix typos in error messages and symbol names
		Leave obscure error messages like 'Rusty needs more caffeine'
		Make binary contain string of copyright message, not only source
	Practical rules for potential damages claims
		Use revision control system
		Document source of each copyrightable contribution
			Name+Email address in CVS commit message
		Consider something like FSFE FLA (Fiduciary License Agreement)
		Make sure that employers are fine with contributions of their employees
	If you find out about violation
		Don't make it public (has to be new/urgent for injunctive relief)
		Contact lawyer immediately to send wanrning notice

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Finding GPL violations

Finding GPL violations in embedded systems
	Software based reverse engineering techniques
		Analyze firmware update files
		Exploit security bugs in firmware
		Use existing "backdoors"
	Hardware based reverse engineering techniques
		Take actual board apart, note major components
		Find + use JTAG testpads
		Find + use serial console

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Finding GPL violations

Software based reverse enigneering
	Analyzing firmware update files
		Typically very easy, you don't even need the device to start with
		Firmware updates available on the internet
		Start with hex-editor, 'strings' and some pattern-matching
		Find magic numbers of kernel image, cramfs/jffs2 rootfs image
		extract kernel and/or rootfs by very easy means (dd, gzip/bzip2, ...)

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Finding GPL violations

Software based reverse enigneering
	Exploit security bugs in firmware
		Typical embedded system vendor has 
			zero clue about Linux
			zero clue about Security
			ages old software versions
		Therefore, very easy to exploit years-old security problems
			buffer overflows, stack smashing
			HTTP UI scripting problems (quoting problems)
		Goal
			to get a [root] shell on the affected device

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Finding GPL violations

Software based reverse enigneering
	Use existing "backdoors"
		Sometimes, devices have existing backdoors from R&D
		e.g. special undocumented command in telnet or SSH UI for getting a shell
		very device-specific, no generic rule how to find it

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Hardware based reverse engineering

Hardware based reverse engineering
	almost always successful
	amount of work differs from device to device
	see the next slides for an example
	BTW: the device in question is NOT a GPL violation

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Take hardware apart

Opening the case and void your warranty
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Note the convenient test pads beneath the battery 

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Take hardware apart

Opening the case
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If you have a bit of experience in taking apart devices, you can do that without any damage...

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Take hardware apart

The Mainboard with all its shielding covers
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Obvoiusly, the shielding needs to go

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Take hardware apart

The application processor section
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Take hardware apart

The HSDPA modem section
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Take hardware apart

The backside
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JTAG pins


	JTAG is a very useful interface
		boundary scan (EXTEST + INTEST)
		ARM Integrated Debug Macrocell
	Find + use JTAG testpads
		look for suspicious testpads on PCB
		tracing PCB traces impossible at 8-layer PCB
		trial + error
		sometimes you might find schematics ;)

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JTAG pins

Find + use JTAG testpads
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JTAG pins

	Find + use JTAG testpads
		JTAG is basically a long shift register
		Input, Output, Clock (TDI, TDO, TCK)
		Therefore, you can try to shift data in and check if/where it comes out
		Automatized JTAG search by project "jtagfinder" by Hunz (German CCC member)

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JTAG pins

Find + use JTAG testpads
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JTAG pins

Find + use JTAG testpads
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JTAG pins

Find + use JTAG testpads
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JTAG pins

Find + use JTAG testpads
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JTAG pins


Found JTAG pins
	Chain 1
		Samsung S3C2442 Application Processor
		Has standard ARM JTAG ICE
	Chain 2
		CPLD programming interface
	Remaining work
		find the nTRST and nSRST pins

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Serial console


How to find the serial console
	Just run some code that you think writes to it
	Use a Scope to find typical patterns of a serial port
	I haven't actually done (or needed) this on the glofiish yet, but on many other devices
	RxD pin is harder to find, just trial+error usually works as soon as you have some interactive prompt that echo's the characters you write
	Don't forget to add level shifter from 3.3/5V to RS232 levels


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The End


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	Further reading:
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	The http://gpl-violations.org/ project
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	The Free Software Foundation http://www.fsf.org/, http://www.fsf-europe.org/
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	The GNU Project http://www.gnu.org/
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	The netfilter homepage http://www.netfilter.org/
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