[PATCH v9 5/5] crypto/tls-cipher-suites: Produce fw_cfg consumable blob

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Since our format is consumable by the fw_cfg device,
we can implement the FW_CFG_DATA_GENERATOR interface.

Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
v9: Fixed typos in qemu-options.hx (lersek)
---
 crypto/tls-cipher-suites.c | 19 +++++++++++++++++++
 qemu-options.hx            | 18 ++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/crypto/tls-cipher-suites.c b/crypto/tls-cipher-suites.c
index f02a041f9a..d6ea0ed190 100644
--- a/crypto/tls-cipher-suites.c
+++ b/crypto/tls-cipher-suites.c
@@ -14,6 +14,7 @@
 #include "qemu/error-report.h"
 #include "crypto/tlscreds.h"
 #include "crypto/tls-cipher-suites.h"
+#include "hw/nvram/fw_cfg.h"
 #include "trace.h"
 
 static void parse_cipher_suites(QCryptoTLSCipherSuites *s,
@@ -99,11 +100,28 @@ static void qcrypto_tls_cipher_suites_finalize(Object *obj)
     g_free(s->cipher_list);
 }
 
+static const void *qcrypto_tls_cipher_suites_get_data(Object *obj)
+{
+    QCryptoTLSCipherSuites *s = QCRYPTO_TLS_CIPHER_SUITES(obj);
+
+    return s->cipher_list;
+}
+
+static size_t qcrypto_tls_cipher_suites_get_length(Object *obj)
+{
+    QCryptoTLSCipherSuites *s = QCRYPTO_TLS_CIPHER_SUITES(obj);
+
+    return s->cipher_count * sizeof(IANA_TLS_CIPHER);
+}
+
 static void qcrypto_tls_cipher_suites_class_init(ObjectClass *oc, void *data)
 {
     UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
+    FWCfgDataGeneratorClass *fwgc = FW_CFG_DATA_GENERATOR_CLASS(oc);
 
     ucc->complete = qcrypto_tls_cipher_suites_complete;
+    fwgc->get_data = qcrypto_tls_cipher_suites_get_data;
+    fwgc->get_length = qcrypto_tls_cipher_suites_get_length;
 }
 
 static const TypeInfo qcrypto_tls_cipher_suites_info = {
@@ -115,6 +133,7 @@ static const TypeInfo qcrypto_tls_cipher_suites_info = {
     .class_init = qcrypto_tls_cipher_suites_class_init,
     .interfaces = (InterfaceInfo[]) {
         { TYPE_USER_CREATABLE },
+        { TYPE_FW_CFG_DATA_GENERATOR_INTERFACE },
         { }
     }
 };
diff --git a/qemu-options.hx b/qemu-options.hx
index 4f519f35fd..ce54c7359c 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4585,6 +4585,24 @@ SRST
         string as described at
         https://gnutls.org/manual/html_node/Priority-Strings.html.
 
+        An example of use of this object is to control UEFI HTTPS Boot.
+        The tls-cipher-suites object exposes 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 IANA_TLS_CIPHER
+        objects. The firmware uses the IANA_TLS_CIPHER array for configuring
+        guest-side TLS.
+
+        In the following example, the priority at which the host-side policy
+        is retrieved is given by the ``priority`` property.
+        Given that QEMU uses GNUTLS, ``priority=@SYSTEM`` may be used to
+        refer to /etc/crypto-policies/back-ends/gnutls.config.
+
+        .. parsed-literal::
+
+             # |qemu_system| \
+                 -object tls-cipher-suites,id=mysuite0,priority=@SYSTEM \
+                 -fw_cfg name=etc/edk2/https/ciphers,gen_id=mysuite0
+
     ``-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
-- 
2.21.3