When TLS 1.3 is negotiated on a TLS session, GNUTLS will perform
automatic rekeying of the session after 16 million records. This
is done for all algorithms except CHACHA20_POLY1305 which does
not require rekeying.
Unfortunately the rekeying breaks GNUTLS' promise that it is safe
to use a gnutls_session_t object concurrently from multiple threads
if they are exclusively calling gnutls_record_send/recv.
This patch implements a workaround for QEMU that adds a mutex lock
around any gnutls_record_send/recv call to serialize execution
within GNUTLS code. When GNUTLS calls into the push/pull functions
we can release the lock so the OS level I/O calls can at least
have some parallelism.
The big downside of this is that the actual encryption/decryption
code is fully serialized, which will halve performance of that
cipher operations if two threads are contending.
The workaround is not enabled by default, since most use of GNUTLS
in QEMU does not tickle the problem, only non-multifd migration
with a return path open is affected. Fortunately the migration
code also won't trigger the halving of performance, since only
the outbound channel diretion needs to sustain high data rates,
the inbound direction is low volume.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/qemu-devel/20250718150514.2635338-2-berrange@redhat.com
[add stub for qcrypto_tls_session_require_thread_safety; fix unused var]
Signed-off-by: Fabiano Rosas <farosas@suse.de>
The correct way of calling qcrypto_tls_session_handshake() requires
calling qcrypto_tls_session_get_handshake_status() right after it so
there's no reason to have a separate method.
Refactor qcrypto_tls_session_handshake() to inform the status in its
own return value and alter the callers accordingly.
No functional change.
Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
QEMU's TLS session code provides no way to call gnutls_bye() to
terminate a TLS session. Callers of qcrypto_tls_session_read() can
choose to ignore a GNUTLS_E_PREMATURE_TERMINATION error by setting the
gracefulTermination argument.
The QIOChannelTLS ignores the premature termination error whenever
shutdown() has already been issued. This was found to be not enough for
the migration code because shutdown() might not have been issued before
the connection is terminated.
Add support for calling gnutls_bye() in the tlssession layer so users
of QIOChannelTLS can clearly identify the end of a TLS session.
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
GNUTLS doesn't know how to perform I/O on anything other than plain
FDs, so the TLS session provides it with some I/O callbacks. The
GNUTLS API design requires these callbacks to return a unix errno
value, which means we're currently loosing the useful QEMU "Error"
object.
This changes the I/O callbacks in QEMU to stash the "Error" object
in the QCryptoTLSSession class, and fetch it when seeing an I/O
error returned from GNUTLS, thus preserving useful error messages.
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
The current TLS session I/O APIs just return a synthetic errno
value on error, which has been translated from a gnutls error
value. This looses a large amount of valuable information that
distinguishes different scenarios.
Pushing population of the "Error *errp" object into the TLS
session I/O APIs gives more detailed error information.
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
The new `qcrypto_tls_session_check_pending` function allows the caller
to know if data have already been consumed from the backend and is
already available.
Signed-off-by: Antoine Damhet <antoine.damhet@shadow.tech>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Cc: "Daniel P. Berrangé" <berrange@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20191204093625.14836-3-armbru@redhat.com>
Acked-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Allow crypto structs to be used with g_autoptr, avoiding the need to
explicitly call XXX_free() functions when variables go out of scope on
the stack.
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
It's either "GNU *Library* General Public License version 2" or "GNU
Lesser General Public License version *2.1*", but there was no "version
2.0" of the "Lesser" license. So assume that version 2.1 is meant here.
Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Header guard symbols should match their file name to make guard
collisions less likely. Offenders found with
scripts/clean-header-guards.pl -vn.
Cleaned up with scripts/clean-header-guards.pl, followed by some
renaming of new guard symbols picked by the script to better ones.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
The example code wouldn't even compile, since it did not use
a consistent spelling for the Error ** parameter.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Introduce a QCryptoTLSSession object that will encapsulate
all the code for setting up and using a client/sever TLS
session. This isolates the code which depends on the gnutls
library, avoiding #ifdefs in the rest of the codebase, as
well as facilitating any possible future port to other TLS
libraries, if desired. It makes use of the previously
defined QCryptoTLSCreds object to access credentials to
use with the session. It also includes further unit tests
to validate the correctness of the TLS session handshake
and certificate validation. This is functionally equivalent
to the current TLS session handling code embedded in the
VNC server, and will obsolete it.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
