Since tar multi-archive no longer used, we can simply instruct tar to
pipe output through gzip (or whatever compressor we want). Include used
compressor command in backup header.
Tar multi-volume support is broken when used with sparse files[1], so do
not use it. Instead simply cut the archive manually and concatenate at
restore time. This change require a little modification in restore
process, so make this new backup format ("3"). Also add backup format
version to the header, instead of some guessing code.
For now only cleartext and encrypted backups implemented, compression
will come as a separate commit.
loop device parsing should have "dXpY_style = True" in order to
correctly parse partitions on loop devices.
Reasoning:
==========
Using losetup to create a virtual SD card disk into a loop device and
creating partitions for it results in new devices within an AppVM that
look like: /dev/loop0p1 /dev/loop0p2 and so on.
However as soon as they are created, Qubes Manager rises an exception
and becomes blocked with the following message (redacted):
"QubesException: Invalid device name: loop0p1
at line 639 of file /usr/lib64/python2.7/site-
packages/qubesmanager/main.py
Details:
line: raise QubesException....
func: block_name_to_majorminor
line no.: 181
file: ....../qubes/qubesutils.py
Backups should be safe also for long-term, so change HMAC to SHA512,
which should be usable much longer than SHA1.
See this thread for discussion:
https://groups.google.com/d/msg/qubes-devel/5X-WjdP9VqQ/4zI8-QWd0S4J
Additionally save guessed HMAC in artificial header data (when no real
header exists).
Previously this message goes to /dev/null (unless BACKUP_DEBUG enabled),
so the user got cryptic "Restore failed" message without any clue about
the cause.
When non-english language is set, some processes can output non-ASCII
characters in error messages. Handle them nicely.
Also make error messages more consistent about "ERROR:" prefix. Do not
use this prefix in QubesException message, add it just before showing
the message to the user.
The --xform option affects all the names - including symlink targets. So
make the pattern as precise as possible to not break symlinks in dom0
home backup. Still not ideal, but at least limit damage to relative
symlinks pointing at <username> directory (which hopefully user will
not create). Previous version broke all relative symlinks...
Apparently kernel patch "x86/cpa: Use pte_attrs instead of pte_flags on
CPA/set_p.._wb/wc operations" (in out repo) doesn't fully solve the
problem and sometimes qubes-gui agent crashes with message like
"qubes-gui:664 map pfn expected mapping type write-back for [mem
0x00093000-0x00093fff], got uncached-minus".
Because PAT we really need only in dom0 (lack of it dramatically
decrease performance of some graphics drivers), we can simply disable it
in VM - as it is currently done in upstream kernel.
The backup_cancel() method kills processes registered by main thread and
set "running_backup_operation.canceled" to True. Then main thread get an
error because of killed processes and check if that was because of
cancel request.
Introduce BackupCanceledError, which can report temporary dir to remove.
Do wait for nest reported filename only when restoring directly from
dom0. In VM case it isn't necessary and will cause false error report
(because filename will be set to nextfile at the end of restore process,
so will be treated as spurious file without hmac).
Simply get device major-minor from /dev/ device file.
This is only partial solution, because this will work only for dom0
devices, but the same problem can apply to VM.
It stores basic backup information like used hmac/crypto algorithm,
whether backup is encrypted/compressed and possibly more. The header
file is parsed only after successful HMAC verification. Because we do
not know which HMAC algorithm was used before reading the header, try to
guess trying all supported (starting with the default one).
Backup header is stored as the first file, which is always not encrypted
and not compressed. Then qubes.xml follows.
Call backup_restore_header from backup_restore_prepare, there is no
sense in requiring the user to call them separately. Also store all
parameters in restore_info object as special '$OPTIONS$' VM to not
require passing them twice (with all the chances for the errors).
This can be any application, for example Qubes Manager. Changing current
dir can have side effects, especially when we do not change it back
after restore (or in any error encountered).
Save the next one in temporary file, then move over to destination file.
This way when writing the file to disk fails (e.g. out of disk space),
user still have old file version intact.
This is somehow related to #757, but only first (easier) step. Actual
change of QubesAdminVm base class requires somehow more changes, for
example qvm-ls needs to know how to display this type of VM (none of
template, appvm, netvm).
Make this first step change now, because starting with R2Beta3 dom0 will
be stored in qubes.xml (for new backups purposes) so this rename would
be complicated later.
Template is saved as single archive of the whole VM directory. Preserve
backup directory structure regardless of its content - in this case it
means we need "." archive (with template directory content) placed in
"vm-tempates/<template-name>/" backup directory. This allows restore
process to select right files to restore regardless of VM type.
