GNUTLS takes a paranoid approach when seeing 0 bytes returned by the
underlying OS read() function. It will consider this an error and
return GNUTLS_E_PREMATURE_TERMINATION instead of propagating the 0
return value. It expects apps to arrange for clean termination at
the protocol level and not rely on seeing EOF from a read call to
detect shutdown. This is to harden apps against a malicious 3rd party
causing termination of the sockets layer.
This is unhelpful for the QEMU NBD code which does have a clean
protocol level shutdown, but still relies on seeing 0 from the I/O
channel read in the coroutine handling incoming replies.
The upshot is that when using a plain NBD connection shutdown is
silent, but when using TLS, the client spams the console with
Cannot read from TLS channel: Broken pipe
The NBD connection has, however, called qio_channel_shutdown()
at this point to indicate that it is done with I/O. This gives
the opportunity to optimize the code such that when the channel
has been shutdown in the read direction, the error code
GNUTLS_E_PREMATURE_TERMINATION gets turned into a '0' return
instead of an error.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20181119134228.11031-1-berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
gnutls 3.0.0 was released in 2011 and all the distros that are build
target platforms for QEMU [1] include it:
RHEL-7: 3.1.18
Debian (Stretch): 3.5.8
Debian (Jessie): 3.3.8
OpenBSD (ports): 3.5.18
FreeBSD (ports): 3.5.18
OpenSUSE Leap 15: 3.6.2
Ubuntu (Xenial): 3.4.10
macOS (Homebrew): 3.5.19
Based on this, it is reasonable to require gnutls >= 3.1.18 in QEMU
which allows for all conditional version checks in the code to be
removed.
[1] https://qemu.weilnetz.de/doc/qemu-doc.html#Supported-build-platforms
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Pre-Shared Keys (PSK) is a simpler mechanism for enabling TLS
connections than using certificates. It requires only a simple secret
key:
$ mkdir -m 0700 /tmp/keys
$ psktool -u rjones -p /tmp/keys/keys.psk
$ cat /tmp/keys/keys.psk
rjones:d543770c15ad93d76443fb56f501a31969235f47e999720ae8d2336f6a13fcbc
The key can be secretly shared between clients and servers. Clients
must specify the directory containing the "keys.psk" file and a
username (defaults to "qemu"). Servers must specify only the
directory.
Example NBD client:
$ qemu-img info \
--object tls-creds-psk,id=tls0,dir=/tmp/keys,username=rjones,endpoint=client \
--image-opts \
file.driver=nbd,file.host=localhost,file.port=10809,file.tls-creds=tls0,file.export=/
Example NBD server using qemu-nbd:
$ qemu-nbd -t -x / \
--object tls-creds-psk,id=tls0,endpoint=server,dir=/tmp/keys \
--tls-creds tls0 \
image.qcow2
Example NBD server using nbdkit:
$ nbdkit -n -e / -fv \
--tls=on --tls-psk=/tmp/keys/keys.psk \
file file=disk.img
Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
It is very useful to know about TLS cert verification
status when debugging, so add a trace point for it.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Modern gnutls can use a global config file to control the
crypto priority settings for TLS connections. For example
the priority string "@SYSTEM" instructs gnutls to find the
priority setting named "SYSTEM" in the global config file.
Latest gnutls GIT codebase gained the ability to reference
multiple priority strings in the config file, with the first
one that is found to existing winning. This means it is now
possible to configure QEMU out of the box with a default
priority of "@QEMU,SYSTEM", which says to look for the
settings "QEMU" first, and if not found, use the "SYSTEM"
settings.
To make use of this facility, we introduce the ability to
set the QEMU default priority at build time via a new
configure argument. It is anticipated that distro vendors
will set this when building QEMU to a suitable value for
use with distro crypto policy setup. eg current Fedora
would run
./configure --tls-priority=@SYSTEM
while future Fedora would run
./configure --tls-priority=@QEMU,SYSTEM
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
The gnutls default priority is either "NORMAL" (most historical
versions of gnutls) which is a built-in label in gnutls code,
or "@SYSTEM" (latest gnutls on Fedora at least) which refers
to an admin customizable entry in a gnutls config file.
Regardless of which default is used by a distro, they are both
global defaults applying to all applications using gnutls. If
a single application on the system needs to use a weaker set
of crypto priorities, this potentially forces the weakness onto
all applications. Or conversely if a single application wants a
strong default than all others, it can't do this via the global
config file.
This adds an extra parameter to the tls credential object which
allows the mgmt app / user to explicitly provide a priority
string to QEMU when configuring TLS.
For example, to use the "NORMAL" priority, but disable SSL 3.0
one can now configure QEMU thus:
$QEMU -object tls-creds-x509,id=tls0,dir=/home/berrange/qemutls,\
priority="NORMAL:-VERS-SSL3.0" \
..other args...
If creating tls-creds-anon, whatever priority the user specifies
will always have "+ANON-DH" appended to it, since that's mandatory
to make the anonymous credentials work.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Commit 57cb38b included qapi/error.h into qemu/osdep.h to get the
Error typedef. Since then, we've moved to include qemu/osdep.h
everywhere. Its file comment explains: "To avoid getting into
possible circular include dependencies, this file should not include
any other QEMU headers, with the exceptions of config-host.h,
compiler.h, os-posix.h and os-win32.h, all of which are doing a
similar job to this file and are under similar constraints."
qapi/error.h doesn't do a similar job, and it doesn't adhere to
similar constraints: it includes qapi-types.h. That's in excess of
100KiB of crap most .c files don't actually need.
Add the typedef to qemu/typedefs.h, and include that instead of
qapi/error.h. Include qapi/error.h in .c files that need it and don't
get it now. Include qapi-types.h in qom/object.h for uint16List.
Update scripts/clean-includes accordingly. Update it further to match
reality: replace config.h by config-target.h, add sysemu/os-posix.h,
sysemu/os-win32.h. Update the list of includes in the qemu/osdep.h
comment quoted above similarly.
This reduces the number of objects depending on qapi/error.h from "all
of them" to less than a third. Unfortunately, the number depending on
qapi-types.h shrinks only a little. More work is needed for that one.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
[Fix compilation without the spice devel packages. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Clean up includes so that osdep.h is included first and headers
which it implies are not included manually.
This commit was created with scripts/clean-includes.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1453832250-766-3-git-send-email-peter.maydell@linaro.org
The qcrypto_tls_session_check_certificate() method was setting
an Error even when the ACL check suceeded. This didn't affect
the callers detection of errors because they relied on the
function return status, but this did cause a memory leak since
the caller would not free an Error they did not expect to be
set.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
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>
