bug#35996: User account password got locked when booting old generation

["pelzflorian (Florian Pelz)" <pelzflorian@pelzflorian.de>]

On Tue, Jun 04, 2019 at 11:22:45AM +0200, Ludovic Courtès wrote:
> Hi,
> 
> "pelzflorian (Florian Pelz)" <pelzflorian@pelzflorian.de> skribis:
> 
> > On Mon, Jun 03, 2019 at 03:22:51PM +0200, Ludovic Courtès wrote:
> >> > After multiple reconfigures, it happened again, my /etc/shadow has !
> >> > again in the password field.  My recently changed root password became
> >> > empty as well, like 35902.  I did not even run sudo concurrently.  The
> >> > password just got locked.
> >> 
> >> What were the differences between your config files when you
> >> reconfigured?
> >>
> >
> > For the last reconfigure, there were no differences, although I had
> > rebooted into an unbootable, older generation with a different
> > syslog.conf and broken Udevd arguments before booting the new
> > generation.
> 
> What’s the effect of this brokenness concretely?  Is the wrong root file
> system mounted, or something like that?
> 

I have multiple broken generation.  On one that now for a third time
(on old generations without Ludo’s patches) led to a locked
/etc/shadow after booting I changed the line
(let ((pid (fork+exec-command (list udevd))))
in gnu/services/base.scm to, I believe, this:
(let ((pid (fork+exec-command (list udevd "--debug-trace"))))

(I am unsure if this is the same broken generation as on my first
report of the issue.  I may have gotten confused.)

This is unbootable, correct would have been --debug and not
--debug-trace.

I may also have changed my syslog configuration to the incorrect

                   (modify-services %desktop-services
                     (syslog-service-type config =>
                       (syslog-configuration
                        (inherit config)
                        (config-file
(plain-file "my-syslog.conf" "
     # Log all error messages, authentication messages of
     # level notice or higher and anything of level err or
     # higher to the console.
     # Don't log private authentication messages!
     *       /var/log/full
[…]")))))))

Correct would have been *.* instead of *  This latter error is
without relevant effect I believe.

I will try to find the /gnu/store files for this generation.

Danny’s suggestion to `chattr +i /etc/shadow` leads to an error with
rename-file trying to rename an empty /etc/shadow.Gi… temporary file
on both this old broken and on healthy generations.


> There really isn’t much to log: the activation code reads
> /etc/{shadow,passwd,group}, computes the list of shadow/passwd/group
> entries as a function of that, and writes it.
> 

If I cannot find a more deterministic way, I will try making (guix
build accounts) print the content of shadow.

Regards,
Florian