Re: [PATCH] s390/zcrypt: enable s390 hwrng to seed kernel entropy

[Ingo Tuchscherer]

On 08/11/2014 03:56 PM, Torsten Duwe wrote:
> On Wed, Jul 30, 2014 at 02:17:36PM +0200, Ingo Tuchscherer wrote:
> > Set the 'quality' property in the zcrypt rng device structure to enable the
> > zcrypt hwrng device to take part in the kernel entropy seeding process.
> > A module parameter named hwrng_seed will be introduced to disable the
> > participation. By default this parameter is set to 1 (enabled).
> I only had a one-liner that simply enabled it. I guess the extra switch
> is for certification scenarios?
I introduced this switch for several reasons. I would like to have the 
possibility to prevent the card from being interrupted with rng queries 
(in case of heavy workload) or card verification/certification or other 
measurement processes.
Last but not least we are able to deactivate this feature in case of any 
failures/attacks.

> Anyway,
>
> Acked-by: Torsten Duwe <duwe@xxxxxxx>
> > Signed-off-by: Ingo Tuchscherer <ingo.tuchscherer@xxxxxxxxxx>
> > ---
> >   drivers/s390/crypto/ap_bus.c     | 5 +++++
> >   drivers/s390/crypto/ap_bus.h     | 1 +
> >   drivers/s390/crypto/zcrypt_api.c | 3 +++
> >   3 files changed, 9 insertions(+)
> >
> > diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
> > index 4038437..19fac5f 100644
> > --- a/drivers/s390/crypto/ap_bus.c
> > +++ b/drivers/s390/crypto/ap_bus.c
> > @@ -85,6 +85,11 @@ static int ap_thread_flag = 0;
> >   module_param_named(poll_thread, ap_thread_flag, int, S_IRUSR|S_IRGRP);
> >   MODULE_PARM_DESC(poll_thread, "Turn on/off poll thread, default is 0 (off).");
> >   
> > +int ap_hwrng_seed = 1;
> > +EXPORT_SYMBOL(ap_hwrng_seed);
> > +module_param_named(hwrng_seed, ap_hwrng_seed, int, S_IRUSR|S_IRGRP);
> > +MODULE_PARM_DESC(hwrng_seed, "Turn on/off hwrng auto seed, default is 1 (on).");
> > +
> >   static struct device *ap_root_device = NULL;
> >   static struct ap_config_info *ap_configuration;
> >   static DEFINE_SPINLOCK(ap_device_list_lock);
> > diff --git a/drivers/s390/crypto/ap_bus.h b/drivers/s390/crypto/ap_bus.h
> > index 6405ae2..b0be09a 100644
> > --- a/drivers/s390/crypto/ap_bus.h
> > +++ b/drivers/s390/crypto/ap_bus.h
> > @@ -38,6 +38,7 @@
> >   #define AP_POLL_TIME 1		/* Time in ticks between receive polls. */
> >   
> >   extern int ap_domain_index;
> > +extern int ap_hwrng_seed;
> >   
> >   /**
> >    * The ap_qid_t identifier of an ap queue. It contains a
> > diff --git a/drivers/s390/crypto/zcrypt_api.c b/drivers/s390/crypto/zcrypt_api.c
> > index 0e18c5d..ed91665 100644
> > --- a/drivers/s390/crypto/zcrypt_api.c
> > +++ b/drivers/s390/crypto/zcrypt_api.c
> > @@ -1374,6 +1374,7 @@ static int zcrypt_rng_data_read(struct hwrng *rng, u32 *data)
> >   static struct hwrng zcrypt_rng_dev = {
> >   	.name		= "zcrypt",
> >   	.data_read	= zcrypt_rng_data_read,
> > +	.quality	= 990,
> >   };
> >   
> >   static int zcrypt_rng_device_add(void)
> > @@ -1388,6 +1389,8 @@ static int zcrypt_rng_device_add(void)
> >   			goto out;
> >   		}
> >   		zcrypt_rng_buffer_index = 0;
> > +		if (!ap_hwrng_seed)
> > +			zcrypt_rng_dev.quality = 0;
> >   		rc = hwrng_register(&zcrypt_rng_dev);
> >   		if (rc)
> >   			goto out_free;
> > --
> > 1.8.5.5
> >
> > --
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