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>
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>
A lot of tests run fine on FreeBSD and macOS, too - the limitation
to Linux here was likely just copied-and-pasted from other tests.
Thus remove the "_supported_os Linux" line from tests that run
successful in our CI pipelines on FreeBSD and macOS.
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <20190502084506.8009-6-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Bash is not always installed as /bin/bash. In particular on OpenBSD,
the package installs it in /usr/local/bin.
Use the 'env' shebang to search bash in the $PATH.
Patch created mechanically by running:
$ git grep -lE '#! ?/bin/bash' -- tests/qemu-iotests \
| while read f; do \
sed -i 's|^#!.\?/bin/bash$|#!/usr/bin/env bash|' $f; \
done
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Running
git grep '\$here' tests/qemu-iotests
has 0 hits, which means we are setting a variable that has
no use. It appears that commit e8f8624d removed the last
use. So execute the following cmd to remove all of
the 'here=...' lines as dead code.
sed -i '/^here=/d' $(git grep -l '^here=' tests/qemu-iotests)
Cc: kwolf@redhat.com
Cc: mreitz@redhat.com
Cc: eblake@redhat.com
Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Mao Zhongyi <maozhongyi@cmss.chinamobile.com>
Message-Id: <20181024094051.4470-3-maozhongyi@cmss.chinamobile.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: touch up commit message, reorder series, rebase to master]
Signed-off-by: Eric Blake <eblake@redhat.com>
For the tests that use the common.qemu functions for running a QEMU
process, _cleanup_qemu must be called in the exit function.
If it is not, if the qemu process aborts, then not all of the droppings
are cleaned up (e.g. pidfile, fifos).
This updates those tests that did not have a cleanup in qemu-iotests.
(I swapped spaces for tabs in test 102 as well)
Reported-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
Message-id: d59c2f6ad6c1da8b9b3c7f357c94a7122ccfc55a.1492544096.git.jcody@redhat.com
The previous commit removed the last usage of ${tmp} inside the tests
themselves; the only remaining users are sourced by check. So we can now
drop this variable from the tests.
Signed-off-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Reviewed-by: Bo Tu <tubo@linux.vnet.ibm.com>
Message-id: 1460472980-26319-4-git-send-email-silbe@linux.vnet.ibm.com
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@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>
