Bug#1002527: postinst ignores USER from /etc/default/milter-greylist when invoking chown ... /var/lib/milter-greylist

[Marvin Renich <mrvn@renich.org>]

Package: milter-greylist
Version: 4.6.4-1
Severity: critical

With an existing installation of milter-greylist set up to work with
chrooted postfix (i.e. USER="postfix" in /etc/default/milter-greylist),
every upgrade sets the owner of the directory /var/lib/milter-greylist
to "greylist" regardless of the setting of USER.  This effectively
breaks postfix, as it will no longer deliver mail until the problem is
resolved.

Note that the particular system hosting my mail server is still running
sysvinit, not systemd.  I do not know how milter-greylist configures the
user under systemd, but the postinst has "greylist" hardcoded, so I
suspect that if the sysadmin has configured a different user, this will
break under systemd, as well.

I chose severity critical because it breaks other software, and said
software is possibly the primary reason for the host on which it is
running, and this breakage can affect many users.

...Marvin


-- System Information:
Debian Release: bookworm/sid
  APT prefers testing
  APT policy: (990, 'testing'), (500, 'stable-updates'), (500, 'stable-security'), (500, 'oldstable-updates'), (500, 'stable'), (500, 'oldstable'), (200, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.15.0-2-amd64 (SMP w/8 CPU threads)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /bin/dash
Init: sysvinit (via /sbin/init)
LSM: AppArmor: enabled

Versions of packages milter-greylist depends on:
ii  adduser              3.118
ii  init-system-helpers  1.61
ii  libbind9-161         1:9.11.19+dfsg-2.1
ii  libc6                2.33-1
ii  libcurl4             7.79.1-2
ii  libgeoip1            1.6.12-8
ii  libmilter1.0.1       8.16.1-2
ii  libopendkim11        2.11.0~beta2-6
ii  libspf2-2            1.2.10-7.1
ii  libssl1.1            1.1.1l-1
ii  lsb-base             11.1.0

Versions of packages milter-greylist recommends:
ii  postfix  3.6.3-1

milter-greylist suggests no packages.