crypto: Add tls-cipher-suites object
On the host OS, various aspects of TLS operation are configurable.
In particular it is possible for the sysadmin to control the TLS
cipher/protocol algorithms that applications are permitted to use.
* Any given crypto library has a built-in default priority list
defined by the distro maintainer of the library package (or by
upstream).
* The "crypto-policies" RPM (or equivalent host OS package)
provides a config file such as "/etc/crypto-policies/config",
where the sysadmin can set a high level (library-independent)
policy.
The "update-crypto-policies --set" command (or equivalent) is
used to translate the global policy to individual library
representations, producing files such as
"/etc/crypto-policies/back-ends/*.config". The generated files,
if present, are loaded by the various crypto libraries to
override their own built-in defaults.
For example, the GNUTLS library may read
"/etc/crypto-policies/back-ends/gnutls.config".
* A management application (or the QEMU user) may overide the
system-wide crypto-policies config via their own config, if
they need to diverge from the former.
Thus the priority order is "QEMU user config" > "crypto-policies
system config" > "library built-in config".
Introduce the "tls-cipher-suites" object for exposing the ordered
list of permitted TLS cipher suites from the host side to the
guest firmware, via fw_cfg. The list is represented as an array
of bytes.
The priority at which the host-side policy is retrieved is given
by the "priority" property of the new object type. For example,
"priority=@SYSTEM" may be used to refer to
"/etc/crypto-policies/back-ends/gnutls.config" (given that QEMU
uses GNUTLS).
The firmware uses the IANA_TLS_CIPHER array for configuring
guest-side TLS, for example in UEFI HTTPS Boot.
[Description from Daniel P. Berrangé, edited by Laszlo Ersek.]
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20200623172726.21040-2-philmd@redhat.com>
diff --git a/qemu-options.hx b/qemu-options.hx
index 196f468..ecc4658 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4567,6 +4567,25 @@
string as described at
https://gnutls.org/manual/html_node/Priority-Strings.html.
+ ``-object tls-cipher-suites,id=id,priority=priority``
+ Creates a TLS cipher suites object, which can be used to control
+ the TLS cipher/protocol algorithms that applications are permitted
+ to use.
+
+ The ``id`` parameter is a unique ID which frontends will use to
+ access the ordered list of permitted TLS cipher suites from the
+ host.
+
+ The ``priority`` parameter allows to override the global default
+ priority used by gnutls. This can be useful if the system
+ administrator needs to use a weaker set of crypto priorities for
+ QEMU without potentially forcing the weakness onto all
+ applications. Or conversely if one wants wants a stronger
+ default for QEMU than for all other applications, they can do
+ this through this parameter. Its format is a gnutls priority
+ string as described at
+ https://gnutls.org/manual/html_node/Priority-Strings.html.
+
``-object filter-buffer,id=id,netdev=netdevid,interval=t[,queue=all|rx|tx][,status=on|off][,position=head|tail|id=<id>][,insert=behind|before]``
Interval t can't be 0, this filter batches the packet delivery:
all packets arriving in a given interval on netdev netdevid are
