Ever since commit 36683283 (v2.8), the server code asserts that error
strings sent to the client are well-formed per the protocol by not
exceeding the maximum string length of 4096. At the time the server
first started sending error messages, the assertion could not be
triggered, because messages were completely under our control.
However, over the years, we have added latent scenarios where a client
could trigger the server to attempt an error message that would
include the client's information if it passed other checks first:
- requesting NBD_OPT_INFO/GO on an export name that is not present
(commit 0cfae925 in v2.12 echoes the name)
- requesting NBD_OPT_LIST/SET_META_CONTEXT on an export name that is
not present (commit e7b1948d in v2.12 echoes the name)
At the time, those were still safe because we flagged names larger
than 256 bytes with a different message; but that changed in commit
93676c88 (v4.2) when we raised the name limit to 4096 to match the NBD
string limit. (That commit also failed to change the magic number
4096 in nbd_negotiate_send_rep_err to the just-introduced named
constant.) So with that commit, long client names appended to server
text can now trigger the assertion, and thus be used as a denial of
service attack against a server. As a mitigating factor, if the
server requires TLS, the client cannot trigger the problematic paths
unless it first supplies TLS credentials, and such trusted clients are
less likely to try to intentionally crash the server.
We may later want to further sanitize the user-supplied strings we
place into our error messages, such as scrubbing out control
characters, but that is less important to the CVE fix, so it can be a
later patch to the new nbd_sanitize_name.
Consideration was given to changing the assertion in
nbd_negotiate_send_rep_verr to instead merely log a server error and
truncate the message, to avoid leaving a latent path that could
trigger a future CVE DoS on any new error message. However, this
merely complicates the code for something that is already (correctly)
flagging coding errors, and now that we are aware of the long message
pitfall, we are less likely to introduce such errors in the future,
which would make such error handling dead code.
Reported-by: Xueqiang Wei <xuwei@redhat.com>
CC: qemu-stable@nongnu.org
Fixes: https://bugzilla.redhat.com/1843684 CVE-2020-10761
Fixes: 93676c88d7
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200610163741.3745251-2-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
We generally include relevant HMP input in .out files, by virtue of
the fact that HMP echoes its input. But QMP does not, so we have to
explicitly inject it in the output stream (appropriately filtered to
keep the tests passing), in order to make it easier to read .out files
to see what behavior is being tested (especially true where the output
file is a sequence of {'return': {}}).
Suggested-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20191114213415.23499-4-eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-id: 20191017133155.5327-9-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
One of the recent commits changed the way qemu-io prints out its
errors and warnings - they are now prefixed with the program name.
We've got to adapt the iotests accordingly to prevent that they
are failing.
Fixes: 99e98d7c9f ("qemu-io: Use error_[gs]et_progname()")
Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
It is interesting to know whether the shutdown cause was 'quit' or
'reset', especially when using "--no-reboot". In that case, a management
layer can now determine if the guest wanted a reboot or shutdown, and
can act accordingly.
Changes the output of the reason in the iotests from 'host-qmp' to
'host-qmp-quit'. This does not break compatibility because
the field was introduced in the same version.
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
Message-Id: <20181205110131.23049-4-d.csapak@proxmox.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
This makes it possible to determine what the exact reason was for
a RESET or a SHUTDOWN. A management layer might need the specific reason
of those events to determine which cleanups or other actions it needs to do.
This patch also updates the iotests to the new expected output that includes
the reason.
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
Message-Id: <20181205110131.23049-3-d.csapak@proxmox.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Commit 8ecaeae8 changed the way the client requests an NBD export,
and in the process also changed the resulting error message when
the export is not present, breaking a couple of iotests. The error
message is now directly given by the server (a failed NBD_OPT_GO)
instead of implied by the client (after exhausting NBD_OPT_LIST),
but looking at the testsuite changes, it proves worthwhile to
reword the error message to be slightly less verbose (as this is
one particular error message likely to be hit by a user).
Note that the error message is now sensitive to which binary is
running the server as well as the client (since the expected
output is replaying a message received from the server - for that
matter, it depends on a server new enough to understand NBD_OPT_GO);
in general iotests are run on client and server from the same source
code base so the default setup will pass; but if it proves
problematic for people overriding QEMU_PROG, QEMU_IMG_PROG,
QEMU_IO_PROG, and QEMU_NBD_PROG to point across multiple builds for
cross-version integration testing, we may have to later tweak or
sanitize the output somehow.
Reported-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170717142310.17048-1-eblake@redhat.com>
Tested-by: John Snow <jsnow@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Libvirt would like to be able to distinguish between a SHUTDOWN
event triggered solely by guest request and one triggered by a
SIGTERM or other action on the host. While qemu_kill_report() was
already able to give different output to stderr based on whether a
shutdown was triggered by a host signal (but NOT by a host UI event,
such as clicking the X on the window), that information was then
lost to management. The previous patches improved things to use an
enum throughout all callsites, so now we have something ready to
expose through QMP.
Note that for now, the decision was to expose ONLY a boolean,
rather than promoting ShutdownCause to a QAPI enum; this is because
libvirt has not expressed an interest in anything finer-grained.
We can still add additional details, in a backwards-compatible
manner, if a need later arises (if the addition happens before 2.10,
we can replace the bool with an enum; otherwise, the enum will have
to be in addition to the bool); this patch merely adds a helper
shutdown_caused_by_guest() to map the internal enum into the
external boolean.
Update expected iotest outputs to match the new data (complete
coverage of the affected tests is obtained by -raw, -qcow2, and -nbd).
Here is output from 'virsh qemu-monitor-event --loop' with the
patch installed:
event SHUTDOWN at 1492639680.731251 for domain fedora_13: {"guest":true}
event STOP at 1492639680.732116 for domain fedora_13: <null>
event SHUTDOWN at 1492639680.732830 for domain fedora_13: {"guest":false}
Note that libvirt runs qemu with -no-shutdown: the first SHUTDOWN event
was triggered by an action I took directly in the guest (shutdown -h),
at which point qemu stops the vcpus and waits for libvirt to do any
final cleanups; the second SHUTDOWN event is the result of libvirt
sending SIGTERM now that it has completed cleanup. Libvirt is already
smart enough to only feed the first qemu SHUTDOWN event to the end user
(remember, virsh qemu-monitor-event is a low-level debugging interface
that is explicitly unsupported by libvirt, so it sees things that normal
end users do not); changing qemu to emit SHUTDOWN only once is outside
the scope of this series.
See also https://bugzilla.redhat.com/1384007
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170515214114.15442-6-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
With the new style protocol, the NBD client will currenetly
send NBD_OPT_EXPORT_NAME as the first (and indeed only)
option it wants. The problem is that the NBD protocol spec
does not allow for returning an error message with the
NBD_OPT_EXPORT_NAME option. So if the server mandates use
of TLS, the client will simply see an immediate connection
close after issuing NBD_OPT_EXPORT_NAME which is not user
friendly.
To improve this situation, if we have the fixed new style
protocol, we can sent NBD_OPT_LIST as the first option
to query the list of server exports. We can check for our
named export in this list and raise an error if it is not
found, instead of going ahead and sending NBD_OPT_EXPORT_NAME
with a name that we know will be rejected.
This improves the error reporting both in the case that the
server required TLS, and in the case that the client requested
export name does not exist on the server.
If the server does not support NBD_OPT_LIST, we just ignore
that and carry on with NBD_OPT_EXPORT_NAME as before.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1455129674-17255-12-git-send-email-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Trying to connect to a nonexistent NBD export should not crash the
server.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
