Re: [PATCH v8 5/5] crypto/tls-cipher-suites: Produce fw_cfg consumable blob

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

Hi Laszlo,

On 6/9/20 7:07 PM, Philippe Mathieu-Daudé wrote:
> 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>
> ---
> v8: Add example in qemu-options.hx

I forgot to explain why. Since the fw_cfg 'gen_id' is only added/enabled
in this patch, it seems natural to add the example here.
I kept your A-b for the logical part, but you might recheck my
description/English (or ask to add the description in the previous patch).

> ---
>  crypto/tls-cipher-suites.c | 19 +++++++++++++++++++
>  qemu-options.hx            | 19 +++++++++++++++++++
>  2 files changed, 38 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 c74366d7cc..b12cc910e3 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -4585,6 +4585,25 @@ SRST
>          string as described at
>          https://gnutls.org/manual/html_node/Priority-Strings.html.
>  
> +        An example of use of this object is to enable the UEFI HTTPS Boot.
> +        The tls-cipher-suites object exposes the ordered list of permitted
> +        TLS cipher suites from the host side to the 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 of the new object
> +        type. ``priority=@SYSTEM`` may be used to refer to
> +        /etc/crypto-policies/back-ends/gnutls.config (given that QEMU uses
> +        GNUTLS).
> +
> +        .. 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
>