[Bug 537851] [NEW] dhclient silently ignores unreadable config-file

[Mike C. Fletcher]

Public bug reported:

When running dhclient against a config-file that happens not to be
whitelisted by app-armour, dhclient will silently ignore the failure and
continue with the default config-file in /etc/dhcp3/dhclient.conf rather
than error out.  dhclient should (at least) report an error/warning on
stdout, and should likely exit with a non-zero error code when an
explicitly-passed config-file is not readable.  That is, if the user has
*explicitly* specified a config on the command-line, no config other
than that config should be used.

To reproduce/test, create a dhclient.conf file anywhere that isn't
readable/writable by the app-armour profile (such as ~/) with a non-
standard option specified (one that is not in your
/etc/dhcp3/dhclient.conf):

   send vendor-class-identifier "myvendorname";

and attempt to run:

   $ sudo dhclient -cf ~/dhclient.conf -lf /var/lib/dhcp3/test.leases
eth0

while running wireshark for eth0.  dhclient will silently ignore the
failure to load ~/dhclient.conf and will instead use
/etc/dhcp3/dhclient.conf (you can see this in your wireshark dump, as
vendor-class-identifier will not be sent).  Move the same file to
/etc/dhcp3/dhclient-test.conf and run again and you should see the
option being sent.

Description:    Ubuntu 9.10
Release:        9.10

Package: dhcp3-client
State: installed
Automatically installed: no
Version: 3.1.2-1ubuntu7.1

** Affects: dhcp3 (Ubuntu)
     Importance: Undecided
         Status: New

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dhclient silently ignores unreadable config-file
https://bugs.launchpad.net/bugs/537851
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