Describe flaws in qcow/qcow2 encryption in the docs

The qemu-img.texi / qemu-doc.texi files currently describe the
qcow2/qcow2 encryption thus

  "Encryption uses the AES format which is very secure (128 bit
   keys). Use a long password (16 characters) to get maximum
   protection."

While AES is indeed a strong encryption system, the way that
QCow/QCow2 use it results in a poor/weak encryption system.
Due to the use of predictable IVs, based on the sector number
extended to 128 bits, it is vulnerable to chosen plaintext
attacks which can reveal the existence of encrypted data.

The direct use of the user passphrase as the encryption key
also leads to an inability to change the passphrase of an
image. If passphrase is ever compromised the image data will
all be vulnerable, since it cannot be re-encrypted. The admin
has to clone the image files with a new passphrase and then
use a program like shred to secure erase all the old files.

Recommend against any use of QCow/QCow2 encryption, directing
users to dm-crypt / LUKS which can meet modern cryptography
best practices.

[Changed "Qcow" to "qcow" for consistency.
--Stefan]

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
block: remove QED .bdrv_make_empty implementation

The QED .bdrv_make_empty() implementation does nothing but return
-ENOTSUP, which causes problems in bdrv_commit().  Since the function
stub exists for QED, it is called, which then always returns an error.

The proper way to not support an optional driver function stub is to
just not implement it, so let's remove the stub.

Signed-off-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
block: remove qcow2 .bdrv_make_empty implementation

The QCOW2 .bdrv_make_empty implementation always returns 0 for success,
but does not actually do anything.

The proper way to not support an optional driver function stub is to
just not implement it, so let's remove the stub.

Signed-off-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
block/vmdk: add basic .bdrv_check support

this adds a basic vmdk corruption check. it should detect severe
table corruptions and file truncation.

Signed-off-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
qemu-iotests: Drop assert_no_active_commit in case 040

It is exactly assert_no_active_block_jobs in iotests.py

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
block/vhdx: Error checking fixes

Errors are inadvertently ignored in a few places.  Has always been
broken.  Spotted by Coverity.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
dataplane: Comment fix

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
qemu-iotests: only run 071 on qcow2

The 071 test is designed for IMGFMT=qcow2 because it uses the l2_load
blkdebug event.  Its output filtering also assumes that IMGFMT is not
raw since 071.out contains "format=raw" but IMGFMT=raw would filter the
output to "format=IMGFMT".

Perhaps the test case can be rewritten to be more generic, but for now
let's document that it was only supposed to work with qcow2.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
qemu 1.7.0 does not build on NetBSD

 Do not rely on int8_t (and friends) not being preprocessor
 symbols (or symbols expanding to themselves). On NetBSD (for example) the
 glue(u, SDATA_TYPE) results in u__int8_t, which is undefined. There is no way
 to stop cpp expanding inner macros, so just add the few lines explicitly and
 get rid of the magic.

Signed-off-by: Martin Husemann <martin@NetBSD.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
osdep: drop unused #include "trace.h"

osdep.c does not use trace_*() so we can just drop the include.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
i386: Add missing include file for QEMU_PACKED

Instead of packing BiosLinkerLoaderEntry, an unused global variable called
QEMU_PACKED was created (detected by smatch static code analysis).

Including qemu-common.h gets the right definition and also includes some
standard include files which now can be removed here.

Cc: qemu-stable@nongnu.org
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
tcg/s390: Remove sigill_handler

Commit c9baa30f42a87f61627391698f63fa4d1566d9d8 failed to
delete all of the relevant code, leading to Werrors about
unused symbols.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
readline: Add missing GCC_FMT_ATTR

This fixes a compiler warning with -Werror=missing-format-attribute
and allows improved compiler checks for variable argument lists.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
hw/ppc: Remove unused defines

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
tests/.gitignore: Ignore tests/check-qom-interface

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Block pull request

# gpg: Signature made Fri 31 Jan 2014 21:16:43 GMT using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  qemu-iotests: only run 071 on qcow2
  dataplane: Comment fix
  block/vhdx: Error checking fixes
  qemu-iotests: Drop assert_no_active_commit in case 040
  block/vmdk: add basic .bdrv_check support
  block: remove qcow2 .bdrv_make_empty implementation
  block: remove QED .bdrv_make_empty implementation
  Describe flaws in qcow/qcow2 encryption in the docs

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Merge remote-tracking branch 'remotes/mjt/tags/trivial-patches-2014-02-02' into staging

trivial patches for 2014-02-02

# gpg: Signature made Sun 02 Feb 2014 16:11:37 GMT using RSA key ID 74F0C838
# gpg: Good signature from "Michael Tokarev <mjt@tls.msk.ru>"
# gpg:                 aka "Michael Tokarev <mjt@corpit.ru>"
# gpg:                 aka "Michael Tokarev <mjt@debian.org>"
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 6EE1 95D1 886E 8FFB 810D  4324 457C E0A0 8044 65C5
#      Subkey fingerprint: E190 8639 3B10 B51B AC2C  8B73 5253 C5AD 74F0 C838

* remotes/mjt/tags/trivial-patches-2014-02-02:
  tests/.gitignore: Ignore tests/check-qom-interface
  hw/ppc: Remove unused defines
  readline: Add missing GCC_FMT_ATTR
  tcg/s390: Remove sigill_handler
  i386: Add missing include file for QEMU_PACKED
  osdep: drop unused #include "trace.h"
  qemu 1.7.0 does not build on NetBSD

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>