Bug#959056: apache2: virtualhost configuration ignored by 000-default.conf interference

[Simone Piccardi <piccardi@truelite.it>]

Package: apache2
Version: 2.4.38-3+deb10u3
Severity: normal

Dear Maintainer,

I configured a virtual host in sites-available for the 
nextcloud.truelite.it hostname, that's also the FQDN hostname (as from
hostname --fqdn) of the server.  I enabled it (with a2ensite) and
restarted apache but still having it ignored and getting the welcome
page as served by 000-default.

After some research I found this is caused by 000-default not having a
ServerName configuration, that means automatically defining it at the
server FQDN hostname. And because 000-default came *before* all other
vhost, it is used instead of the specific one I set.

This is misleading, because despite having an explicit configuration
for a virtual host, an implicit one (and not so easy to spot) is used.
Please also note that this problem is absent in Debian default
configuration of nginx. 

So please put a suitable non interfering ServerName config value on
000-default (someting like ServerName invalid put in the modified
000-default I'm using that should be attached to this report), this
way 000-default will still act as default for not defined hostnames,
but will not give interference when you define an explicit virtual
host for your FSDN hostname.

-- Package-specific info:

-- System Information:
Debian Release: 10.3
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 5.3.18-3-pve (SMP w/8 CPU cores)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE
Locale: LANG=it_IT.UTF-8, LC_CTYPE=it_IT.UTF-8 (charmap=UTF-8), LANGUAGE=it_IT.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages apache2 depends on:
ii  apache2-bin    2.4.38-3+deb10u3
ii  apache2-data   2.4.38-3+deb10u3
ii  apache2-utils  2.4.38-3+deb10u3
ii  dpkg           1.19.7
ii  lsb-base       10.2019051400
ii  mime-support   3.62
ii  perl           5.28.1-6
ii  procps         2:3.3.15-2

Versions of packages apache2 recommends:
ii  ssl-cert  1.0.39

Versions of packages apache2 suggests:
pn  apache2-doc                                      <none>
pn  apache2-suexec-pristine | apache2-suexec-custom  <none>
pn  www-browser                                      <none>

Versions of packages apache2-bin depends on:
ii  libapr1                  1.6.5-1+b1
ii  libaprutil1              1.6.1-4
ii  libaprutil1-dbd-sqlite3  1.6.1-4
ii  libaprutil1-ldap         1.6.1-4
ii  libbrotli1               1.0.7-2
ii  libc6                    2.28-10
ii  libcurl4                 7.64.0-4+deb10u1
ii  libjansson4              2.12-1
ii  libldap-2.4-2            2.4.47+dfsg-3+deb10u1
ii  liblua5.2-0              5.2.4-1.1+b2
ii  libnghttp2-14            1.36.0-2+deb10u1
ii  libpcre3                 2:8.39-12
ii  libssl1.1                1.1.1d-0+deb10u3
ii  libxml2                  2.9.4+dfsg1-7+b3
ii  perl                     5.28.1-6
ii  zlib1g                   1:1.2.11.dfsg-1

Versions of packages apache2-bin suggests:
pn  apache2-doc                                      <none>
pn  apache2-suexec-pristine | apache2-suexec-custom  <none>
pn  www-browser                                      <none>

Versions of packages apache2 is related to:
ii  apache2      2.4.38-3+deb10u3
ii  apache2-bin  2.4.38-3+deb10u3

-- Configuration Files:
/etc/apache2/sites-available/000-default.conf changed:
<VirtualHost *:80>
	# The ServerName directive sets the request scheme, hostname and port that
	# the server uses to identify itself. This is used when creating
	# redirection URLs. In the context of virtual hosts, the ServerName
	# specifies what hostname must appear in the request's Host: header to
	# match this virtual host. For the default virtual host (this file) this
	# value is not decisive as it is used as a last resort host regardless.
	# However, you must set it for any further virtual host explicitly.
	#ServerName www.example.com
	ServerAdmin webmaster@localhost
	DocumentRoot /var/www/html
	ServerName invalid
	# Available loglevels: trace8, ..., trace1, debug, info, notice, warn,
	# error, crit, alert, emerg.
	# It is also possible to configure the loglevel for particular
	# modules, e.g.
	#LogLevel info ssl:warn
	ErrorLog ${APACHE_LOG_DIR}/error.log
	CustomLog ${APACHE_LOG_DIR}/access.log combined
	# For most configuration files from conf-available/, which are
	# enabled or disabled at a global level, it is possible to
	# include a line for only one particular virtual host. For example the
	# following line enables the CGI configuration for this host only
	# after it has been globally disabled with "a2disconf".
	#Include conf-available/serve-cgi-bin.conf
</VirtualHost>


-- no debconf information