/etc/apparmor.d/abstractions/apache2-common is in apparmor 2.12-4ubuntu5.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 | # vim:syntax=apparmor
# This file contains basic permissions for Apache and every vHost
  #include <abstractions/nameservice>
  # Allow unconfined processes to send us signals by default
  signal (receive) peer=unconfined,
  # Allow apache to send us signals by default
  signal (receive) peer=/usr/sbin/apache2,
  # Allow other hats to signal by default
  signal peer=/usr/sbin/apache2//*,
  # Allow us to signal ourselves
  signal peer=@{profile_name},
  # Apache
  network inet stream,
  network inet6 stream,
  # apache manual, error pages and icons
  /usr/share/apache2/** r,
  # changehat itself
  @{PROC}/@{pid}/attr/current                        rw,
  # htaccess files - for what ever it is worth
  /**/.htaccess            r,
  /dev/urandom            r,
  # sasl-auth
  /run/saslauthd/mux rw,
  # OCSP stapling
  /var/log/apache2/stapling-cache rw,
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