Re: [PATCH v2 19/58] qom: implement property helper for sha384

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Aug 18, 2023 at 05:50:02AM -0400, Xiaoyao Li wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
> 
> Implement property_add_sha384() which converts hex string <-> uint8_t[48]
> It will be used for TDX which uses sha384 for measurement.

I think it is likely a better idea to use base64 for the encoding
the binary hash - we use base64 for all the sev-guest properties
that were binary data.

At which points the property set/get logic is much simpler as it
is just needing a call to  g_base64_encode / g_base64_decode and
length validation for the decode case.

> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>  include/qom/object.h | 17 ++++++++++
>  qom/object.c         | 76 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 93 insertions(+)
> 
> diff --git a/include/qom/object.h b/include/qom/object.h
> index ef7258a5e149..70399a5b1940 100644
> --- a/include/qom/object.h
> +++ b/include/qom/object.h
> @@ -1887,6 +1887,23 @@ ObjectProperty *object_property_add_alias(Object *obj, const char *name,
>  ObjectProperty *object_property_add_const_link(Object *obj, const char *name,
>                                                 Object *target);
>  
> +
> +/**
> + * object_property_add_sha384:
> + * @obj: the object to add a property to
> + * @name: the name of the property
> + * @v: pointer to value
> + * @flags: bitwise-or'd ObjectPropertyFlags
> + *
> + * Add an sha384 property in memory.  This function will add a
> + * property of type 'sha384'.
> + *
> + * Returns: The newly added property on success, or %NULL on failure.
> + */
> +ObjectProperty * object_property_add_sha384(Object *obj, const char *name,
> +                                            const uint8_t *v,
> +                                            ObjectPropertyFlags flags);
> +
>  /**
>   * object_property_set_description:
>   * @obj: the object owning the property
> diff --git a/qom/object.c b/qom/object.c
> index e25f1e96db1e..e71ce46ed576 100644
> --- a/qom/object.c
> +++ b/qom/object.c
> @@ -15,6 +15,7 @@
>  #include "qapi/error.h"
>  #include "qom/object.h"
>  #include "qom/object_interfaces.h"
> +#include "qemu/ctype.h"
>  #include "qemu/cutils.h"
>  #include "qemu/memalign.h"
>  #include "qapi/visitor.h"
> @@ -2781,6 +2782,81 @@ object_property_add_alias(Object *obj, const char *name,
>      return op;
>  }
>  
> +#define SHA384_DIGEST_SIZE      48
> +static void property_get_sha384(Object *obj, Visitor *v, const char *name,
> +                                void *opaque, Error **errp)
> +{
> +    uint8_t *value = (uint8_t *)opaque;
> +    char str[SHA384_DIGEST_SIZE * 2 + 1];
> +    char *str_ = (char*)str;
> +    size_t i;
> +
> +    for (i = 0; i < SHA384_DIGEST_SIZE; i++) {
> +        char *buf;
> +        buf = &str[i * 2];
> +
> +        sprintf(buf, "%02hhx", value[i]);
> +    }
> +    str[SHA384_DIGEST_SIZE * 2] = '\0';
> +
> +    visit_type_str(v, name, &str_, errp);
> +}
> +
> +static void property_set_sha384(Object *obj, Visitor *v, const char *name,
> +                                    void *opaque, Error **errp)
> +{
> +    uint8_t *value = (uint8_t *)opaque;
> +    char* str;
> +    size_t len;
> +    size_t i;
> +
> +    if (!visit_type_str(v, name, &str, errp)) {
> +        goto err;
> +    }
> +
> +    len = strlen(str);
> +    if (len != SHA384_DIGEST_SIZE * 2) {
> +        error_setg(errp, "invalid length for sha348 hex string %s. "
> +                   "it must be 48 * 2 hex", name);
> +        goto err;
> +    }
> +
> +    for (i = 0; i < SHA384_DIGEST_SIZE; i++) {
> +        if (!qemu_isxdigit(str[i * 2]) || !qemu_isxdigit(str[i * 2 + 1])) {
> +            error_setg(errp, "invalid char for sha318 hex string %s at %c%c",
> +                       name, str[i * 2], str[i * 2 + 1]);
> +            goto err;
> +        }
> +
> +        if (sscanf(str + i * 2, "%02hhx", &value[i]) != 1) {
> +            error_setg(errp, "invalid format for sha318 hex string %s", name);
> +            goto err;
> +        }
> +    }
> +
> +err:
> +    g_free(str);
> +}
> +
> +ObjectProperty *
> +object_property_add_sha384(Object *obj, const char *name,
> +                           const uint8_t *v, ObjectPropertyFlags flags)
> +{
> +    ObjectPropertyAccessor *getter = NULL;
> +    ObjectPropertyAccessor *setter = NULL;
> +
> +    if ((flags & OBJ_PROP_FLAG_READ) == OBJ_PROP_FLAG_READ) {
> +        getter = property_get_sha384;
> +    }
> +
> +    if ((flags & OBJ_PROP_FLAG_WRITE) == OBJ_PROP_FLAG_WRITE) {
> +        setter = property_set_sha384;
> +    }
> +
> +    return object_property_add(obj, name, "sha384",
> +                               getter, setter, NULL, (void *)v);
> +}
> +
>  void object_property_set_description(Object *obj, const char *name,
>                                       const char *description)
>  {
> -- 
> 2.34.1
> 

With regards,
Daniel
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