Revert "Supersede VirtualBox guest DKMS modules with the ones in Linux mainline (refs: #16942)"

This reverts commit 0c000cf8.

This was a workaround for https://bugs.debian.org/934483, which is now
fixed.

config/chroot_local-hooks/50-dkms

@@ -4,16 +4,6 @@ set -e
 set -u
 set -x
 
-# Disabled as long as it's not very useful and breaks stuff:
-#  - Recent Linux kernel ship the vboxvideo and vboxguest modules.
-#  - The out-of-tree dkms package only adds vboxsf (needed by the
-#    "shared folders" feature).
-#  - The out-of-tree dkms modules regularly FTBFS against recent
-#    Linux kernels and need to be installed from sid, so we decided to keep
-#    VirtualBox guest support on a best effort basis, as long as it's
-#    not too painful/expensive to maintain.
-exit 0
-
 echo "Building VirtualBox guest modules"
 
 . /usr/share/tails/build/variables

config/chroot_local-hooks/99-zzzzzz_reproducible-builds-post-processing

@@ -33,9 +33,7 @@ rm /var/lib/systemd/catalog/database
 : > /etc/machine-id
 
 # Remove logs.
-if [ -d /var/lib/dkms ]; then
-    rm -r /var/lib/dkms/*/*/*/*/log
-fi
+rm -r /var/lib/dkms/*/*/*/*/log
 
 # Post-process /etc/shadow by setting the sp_lstchg field to the number of days
 # since SOURCE_DATE_EPOCH instead of 1st Jan 1970. (#12339)

config/chroot_local-includes/etc/live/config.d/user-default-groups.conf

-LIVE_USER_DEFAULT_GROUPS="cdrom dialout floppy video plugdev netdev powerdev scanner lp lpadmin"
+LIVE_USER_DEFAULT_GROUPS="cdrom dialout floppy video plugdev netdev powerdev scanner lp lpadmin vboxsf"

config/chroot_local-includes/usr/share/tails/build/group

@@ -55,6 +55,7 @@ lpadmin:x:115:
 scanner:x:116:saned
 pulse:x:117:
 pulse-access:x:118:
+vboxsf:x:119:
 saned:x:120:
 colord:x:121:
 Debian-gdm:x:200:

features/sane_defaults.feature

@@ -4,7 +4,7 @@ Feature: Tails has a sane default configuration
   Scenario: The live user is setup correctly
     Given I have started Tails from DVD without network and logged in
     Then the live user has been setup by live-boot
-    And the live user is a member of only its own group and "cdrom dialout floppy video plugdev netdev scanner lp lpadmin"
+    And the live user is a member of only its own group and "cdrom dialout floppy video plugdev netdev scanner lp lpadmin vboxsf"
     And the live user owns its home dir and it has normal permissions
 
   Scenario: No unexpected network services

wiki/src/doc/advanced_topics/virtualization/virtualbox.mdwn

@@ -19,6 +19,19 @@ allow to use a persistent volume.
 
 </div>
 
+<div class="tip">
+
+<p>With the <a href="https://www.virtualbox.org/manual/ch04.html#sharedfolders">
+<span class="guilabel">shared folders</span></a> feature of
+<span class="application">VirtualBox</span> you can access files of your
+host system from within the guest system.</p>
+
+<p>Make sure to understand the security implications of [[accessing
+internal hard disks|encryption_and_privacy/your_data_wont_be_saved_unless_explicitly_asked]]
+from Tails before using this feature.</p>
+
+</div>
+
 Security considerations for Windows and macOS
 =============================================