Friday, May 16, 2014

Software verification of SVR4 packages with pkgchk

On Solaris (and Tribblix) you can use the pkgchk command to verify that the contents of a software package are correctly installed.

The simplest invocation is to give pkgchk the name of a package:

pkgchk SUNWcsl

I would expect SUNWcsl to normally validate cleanly. Whereas something like SUNWcsr will tend to produce lots of output as it contains lots of configuration files that get modified. (Use the -n flag to suppress most of the noise.

If you want to check individual files, then you can use

pkgchk -p /usr/bin/ls

or (and I implemented this as part of the OpenSolaris project) you can feed a list of files on stdin:

find /usr/bin -mtime -150 | pkgchk -i -

However, it turns out that there's a a snag with the basic usage of pkgchk to analyze a package, in that it will trust the contents file - both for the list of files in the package, and for their attributes.

Modifying the list of files can be a result of using installf and removef. For example, I delete some of the junk out of /usr/ucb (such as /usr/ucb/cc so as to be sure no poor unfortunate user can ever run it), and use removef to clean up the contents file. A side-effect of this is that pkgchk won't normally be able to detect that those files are missing.

Modifying file attributes can be the result of a second package installing the same pathname with different attributes. Having multiple packages deliver a directory is common, but you can also have multiple packages own a file. Whichever package was installed last gets to choose which attributes are correct, and the normal pkgchck is blind to any changes as a result.

There's a trick to get round this. From Solaris 10, the original package metadata (and unmodified copies of editable files) are kept. Each package has a directory in /var/sadm/pkg, and in each of those you'll find a save directory. This is used when installing zones, so you get a pristine copy. However, you can also use the pkgmap file to verify a package:

pkgchk -m /var/sadm/pkg/SUNWscpu/save/pspool/SUNWscpu/pkgmap

and this form of usage will detect files that have been removed or modified by tools that are smart enough to update the contents file.

(Because those save files are used by zones, you'll find they don't exist in a zone because they wouldn't be needed there. So this trick only works in a global zone, or you need to manually copy the pkgmap file.)

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