Re: [PATCH 0/1] hw/virtio-crypto: add akcipher keylen validation

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Jun 07, 2026 at 08:15:19AM +0800, helei wrote:
> 
> On 6/6/26 16:37, Michael S. Tsirkin wrote:
> > On Sat, Jun 06, 2026 at 03:47:55PM +0800, helei wrote:
> > > The virtio-crypto spec does not dictate a maximum length limit for
> > > asymmetric cipher (akcipher) keys. We added a hard limit which mirrors
> > > the linux kernels's internal limit for akcipher keys (see
> > > keyctl framework and the add_key syscall).
> > We have max_size - doesn't that apply?
> > backends/cryptodev-builtin.c actually sets it:
> > backends/cryptodev-builtin.c:#define CRYPTODEV_BUITLIN_MAX_REQUEST_SIZE  (1024 * 1024)
> > backends/cryptodev-builtin.c:    backend->conf.max_size = CRYPTODEV_BUITLIN_MAX_REQUEST_SIZE;
> 
> Thanks for your review!  I have verified via testing that all processing
> requests in the dataq are strictly
> 
> bounded by max_size, but session creation requests in the ctrlq are not.



well if we read the spec it's vague

  max_size is defined as "the maximum size of the variable-length parameters of data operation of
  each crypto request's content." and
  The driver SHOULD read max_size to discover the maximum size of the variable-length parameters of
  data operation of the crypto request's content


  so data operation.

  however:

  "The device MUST set max_size to show the
  maximum size of crypto request the device supports".

  seems to cover all requests?



btw vhost user sets max_size to max u64 - is that sane?

  

> > 
> > > Maybe we should update the virtio-spec and add a max_akcipher_key_len
> > > field for virtio crypto devices.
> > maybe
> > 
> > > helei (1):
> > >    hw/virtio-crypto: enforce max akcipher key length
> > > 
> > >   hw/virtio/virtio-crypto.c | 13 +++++++++++++
> > >   1 file changed, 13 insertions(+)
> > > 
> > > -- 
> > > 2.43.0