Re: [RFC PATCH 03/10] block: Use qemu_security_policy_taint() API

[Daniel P. Berrangé <berrange@xxxxxxxxxx>]

On Thu, Sep 09, 2021 at 01:20:17AM +0200, Philippe Mathieu-Daudé wrote:
> Add the BlockDriver::bdrv_taints_security_policy() handler.
> Drivers implementing it might taint the global QEMU security
> policy.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
> ---
>  include/block/block_int.h | 6 +++++-
>  block.c                   | 6 ++++++
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index f1a54db0f8c..0ec0a5c06e9 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -169,7 +169,11 @@ struct BlockDriver {
>      int (*bdrv_file_open)(BlockDriverState *bs, QDict *options, int flags,
>                            Error **errp);
>      void (*bdrv_close)(BlockDriverState *bs);
> -
> +    /*
> +     * Return %true if the driver is withing QEMU security policy boundary,
> +     * %false otherwise. See: 
> https://www.qemu.org/contribute/security-process/
> +     */
> +    bool (*bdrv_taints_security_policy)(BlockDriverState *bs);
>  
>      int coroutine_fn (*bdrv_co_create)(BlockdevCreateOptions *opts,
>                                         Error **errp);
> diff --git a/block.c b/block.c
> index b2b66263f9a..696ba486001 100644
> --- a/block.c
> +++ b/block.c
> @@ -49,6 +49,7 @@
>  #include "qemu/timer.h"
>  #include "qemu/cutils.h"
>  #include "qemu/id.h"
> +#include "qemu-common.h"
>  #include "block/coroutines.h"
>  
>  #ifdef CONFIG_BSD
> @@ -1587,6 +1588,11 @@ static int bdrv_open_driver(BlockDriverState *bs, 
> BlockDriver *drv,
>          }
>      }
>  
> +    if (drv->bdrv_taints_security_policy) {
> +        qemu_security_policy_taint(drv->bdrv_taints_security_policy(bs),
> +                                   "Block protocol '%s'", drv->format_name);
> +    }
> +
>      return 0;
>  open_failed:
>      bs->drv = NULL;

Again we need a way to report this via QAPI, but we don't have a natural
place is hang this off for introspection before starting a guest.

The best we can do is report the information after a block backend has
been instantiated. eg  Modify "BlockInfo" struct to gain

   '*secure': 'bool'

Note I made this an optional field, since unless we mark every single
block driver impl straight away, we'll need to cope with the absence
of information.

Regards,
Daniel
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