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Add firmware comparison section showing steps used

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Denver Gingerich 2014-10-25 19:49:47 -04:00
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enforcement-case-studies.tex
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@ -930,6 +930,41 @@ mips-librecmc-linux-uclibc-gcc.bin: /lib/libc.so.6: version `GLIBC_2.14' not fou
% FIXME: add more details once install tests have been completed
\section{Firmware Comparison}
To ensure that the CCS did indeed correspond to the firmware that was shipped on
the router, we compared the firmware image that we built using the above steps
with the filesystem we found on the device itself. The comparison steps we used
were:
* Extract the filesystem from the image we built by running find-firmware.pl
from https://gitorious.org/gpl-compliance-tools/gpl-compliance-scripts on
librecmc-ar71xx-generic-tl-wr841n-v8-squashfs-factory.bin from the bin/ar71xx
directory mentioned above (we noticed that our router said "Ver:8.2" on the
bottom). Then run squashfs4.2/squashfs-tools/bat-unsquashfs42 from
bat-extratools (at http://www.binaryanalysis.org/en/content/show/download )
on the resulting morx0.squash and use the filesystem in the new squashfs-root
directory for comparison.
* Login to the web interface (at http://192.168.10.1/ ) from a computer that is
connected to the router.
* Set a password using the provided link at the top (the UI warns that no
password is set and asks the user to change it).
* Login to the router via SSH, using the root user and the password we just set.
* Compare representative directory listings and binaries to ensure the set of
included files (on the router) is similar to those found in the firmware image
we created (whose contents are now in the local squashfs-root directory). In
particular, we did the following comparisons:
** List the /bin folder ("ls -l /bin") and confirm the list of files is the same
and that the file sizes are similar.
** Check the "strings" output of /bin/busybox to confirm it was similar in both
places (similar number of lines and content of lines). One cannot directly
compare the binaries because the slight compilation variations will cause
some bits to be different.
** Do the above two steps for /lib/modules, /usr/bin, and other directories with
a significant number of binaries.
% FIXME: add details about how to compare the kernel binary
\section{Minor Infractions}
As mentioned above, there were a few minor infractions. These made it slightly