Re: [OE-core] Adding more information to the SBOM

[Alberto Pianon <alberto@pianon.eu>]

Hi Joshua,

nice to meet you!

I'm new to this list, and I've always approached Yocto just from the
"IP compliance side", so I may miss important pieces of information. 
That
is why Marta encouraged me and is helping me to ask community feedback.

Il 2022-09-14 16:56 Joshua Watt ha scritto:
> On Wed, Sep 14, 2022 at 9:16 AM Marta Rybczynska <rybczynska@gmail.com> 
> wrote:
>> 
>> Dear all,
>> (cross-posting to oe-core and *-architecture)
>> In the last months, we have worked in Oniro on using the create-spdx
>> class for both IP compliance and security.
>> 
>> During this work, Alberto Pianon has found that some information is
>> missing from the SBOM and it does not contain enough for Software
>> Composition Analysis. The main missing point is the relation between
>> the actual upstream sources and the final binaries (create-spdx uses
>> composite sources).
> 
> I believe we map the binaries to the source code from the -dbg
> packages; is the premise that this is insufficient? Can you elaborate
> more on why that is, I don't quite understand. The debug sources are
> (basically) what we actually compiled (e.g. post-do_patch) to produce
> the binary, and you can in turn follow these back to the upstream
> sources with the downloadLocation property.

This was also my assumption at the beginning. But then I found that 
there
are recipes with multiple upstream sources, which may be combined/mixed
together in recipes' WORKDIR. For instance this one:

https://git.yoctoproject.org/meta-virtualization/tree/recipes-networking/cni/cni_git.bb

SRC_URI = "\
	git://github.com/containernetworking/cni.git;branch=main;name=cni;protocol=https 
\
         
git://github.com/containernetworking/plugins.git;branch=release-1.1;destsuffix=${S}/src/github.com/containernetworking/plugins;name=plugins;protocol=https 
\
         
git://github.com/flannel-io/cni-plugin;branch=main;name=flannel_plugin;protocol=https;destsuffix=${S}/src/github.com/containernetworking/plugins/plugins/meta/flannel 
\
	"

(The third source is unpacked in a subdir of the second one)

 From here I discovered that we can't assume that the first non-local URI
is the downloadLocation for all source files, because it is not always
the case.

Moreover, in the context of our project we also needed to find the 
upstream
sources also for local patches, scripts, etc. added by recipes (i.e. the
corresponding layers' repos).

> 
>> 
>> Alberto has worked on how to obtain the missing data and now has a
>> POC. This POC provides full source-to-binary tracking of Yocto builds
>> through a couple of scripts (intended to be transformed into a new
>> bbclass at a later stage). The goal is to add the missing pieces of
>> information in order to get a "real" SBOM from Yocto, which should, at
>> a minimum:
> 
> Please be a little careful with the wording; SBoMs have a lot of uses,
> and many of them we can satisfy with what we currently generate; it
> may not do the exact use case you are looking for, but that doesn't
> mean it's not a "real" SBoM :)

You are right, sorry! "real" is meant in the context of our project,
where we need to make our Fossology Audit Team work on "original"
upstream source packages/repos, for a number of reasons (the main being
that in Oniro project we have a complex build matrix with a lot of
available target machines and quite a number of different overrides
depending on the machine, so when it comes to IP compliance we need to
aggregate and simplify, otherwise our IP auditors would die :) )

But since our Audit Team, differently from a commercial project,
is working fully in the open, also other projects may benefit
from this approach: having fully reviewed file-level license
data publicly available for quite a number of upstream sources and
Yocto layers, a complete source-to-binary tracking system would
enable any Yocto projects to get very detailed license information
for their images, to automatically detect license incompatibilities
between linked binary files, etc.

> 
>> 
>> - carefully describe what is found in a final image (i.e. binary files
>> and their dependencies), since that is what is actually distributed
>> and goes into the final product;
>> - describe how such binary files have been generated and where they
>> come from (i.e. upstream sources, including patches and other stuff
>> added from meta-layers); provenance is important for a number of
>> reasons related to IP Compliance and security.
>> 
>> The aim is to become able to:
>> 
>> - map binaries to their corresponding upstream source packages (and
>> not to the "internal" source packages created by recipes by combining
>> multiple upstream sources and patches)
>> - map binaries to the source files that have been actually used to
>> build them - which usually are a small subset of the whole source
>> package
>> 
>> With respect to IP compliance, this would allow to, among other 
>> things:
>> 
>> - get the real license text for each binary file, by getting the
>> license of the specific source files it has been generated from
>> (provided by Fossology, for instance), - and not the main license
>> stated in the corresponding recipe (which may be as confusing as
>> GPL-2.0-or-later & LGPL-2.1-or-later & BSD-3-Clause & BSD-4-Clause, or
>> even worse)
> 
> IIUC this is the difference between the "Declared" license and the
> "Concluded" license. You can report both, and I think
> create-spdx.bbclass can currently do this with its rudimentary source
> license scanning. You really do want both and it's a great way to make
> sure that the "Declared" license (that is the license in the recipe)
> reflects the reality of the source code.
> 

The issue is with components like util-linux, which contains a lot of
sub-components subject to different licenses; util-linux recipe's
license is "GPL-2.0-or-later & LGPL-2.1-or-later & BSD-3-Clause &
BSD-4-Clause", but from such information one cannot tell if a particular
binary file generated from util-linux is subject to GPL, LGPL, or
BSD-3|4-clause.

Of course, being able to track upstream sources to binaries at file
level would be useless if one doesn't have file-level license 
information;
but since Scancode and Fossology (and our Audit Team) may provide such
information, such tracking may become super-useful, in our opinion.


>> - automatically check license incompatibilities at the binary file 
>> level.
>> 
>> Other possible interesting things could be done also on the security 
>> side.
>> 
>> This work intends to add a way to provide additional data that can be
>> used by create-spdx, not to replace create-spdx in any way.
>> 
>> The sources with a long README are available at
>> https://gitlab.eclipse.org/eclipse/oniro-compliancetoolchain/toolchain/tinfoilhat/-/tree/srctracker/srctracker
>> 
>> What do you think of this work? Would it be of interest to integrate
>> into YP at some point? Shall we discuss this?
> 
> This seems promising as something that could potentially move into
> core. I have a few points:
>  - The extraction of the sources to a dedicated directory is something
> that Richard has been toying around with for quite a while, and I
> think it would greatly simplify that part of your process. I would
> very much encourage you to look at the work he's done, and work on
> that to get it pushed across the finish line as it's a really good
> improvement that would benefit not just your source scanning.

Thanks for the suggestion, could you point me to Richard's work?
I'll surely look into it.

>  - I would encourage you to not wait to turn this into a bbclass
> and/or library functions. You should be able to do this in a new
> layer, and that would make it much clearer as to what the path to
> being included in OE-core would look like. It also would (IMHO) be
> nicer to the users :)

Understood :)

I'm the newbie here, so any other suggestion is warmly welcome.

Regards,

Alberto