[PATCH 02/12] random: Implement read_random via getentropy.

[Christian Mauderer]

Am 02.08.2018 um 15:16 schrieb Gedare Bloom:
> On Thu, Aug 2, 2018 at 1:28 AM, Christian Mauderer
> <christian.mauderer at embedded-brains.de> wrote:
>> Am 01.08.2018 um 16:28 schrieb Gedare Bloom:
>>> Is this relied on for IPSec? How secure is it?
>>
>> Hello Gedare,
>>
>> the IPSec implementation in FreeBSD and therefore in RTEMS too uses that
>> function. So you are right that it is a critical one for security.
>>
>> `read_random` is a low-level FreeBSD random number function. From the
>> man page (see
>> https://www.freebsd.org/cgi/man.cgi?query=read_random&manpath=FreeBSD+11.2-RELEASE+and+Ports):
>>
>>     The read_random() function is used to return entropy directly from
>>     the entropy device if it has been loaded. If the entropy device is
>>     not loaded, then the buffer is ignored and zero is returned. The
>>     buffer is filled with no more than count bytes. It is strongly
>>     advised that read_random() is not used; instead use arc4rand()
>>     unless it is necessary to know that no entropy has been returned.
>>
>> That's basically the same what our `getentropy` does. Returning entropy
>> directly from the entropy device if it is available. So it is as close
>> to the original behavior as we can get.
>>
>> Of course `getentropy` only returns a good entropy if there is a real
>> entropy source in the BSP. Currently that is only true for the atsam
>> BSP. I think there should be a patch for BBB somewhere on the mailing list.
>>
>> We have a chapter in the BSP guide regarding that:
>>
>>     https://docs.rtems.org/branches/master/bsp-howto/getentropy.html
>>
>> There is also a hint that a good entropy source is necessary for
>> cryptographic applications. It would be great if you have a good idea
>> how to make a user aware of the security problem if he doesn't use a
>> good crypto source.
>>
> 
> Thank, this makes sense. It is in my long-range plan to sort out
> security concerns. I'm not certain the best way to approach it, maybe
> I will start with a wiki page first.

I agree that addressing security is a good idea. Maybe a checklist in
the manual with relevant points (like "If you do something with
encryption: Does your BSP has a good entropy source?")? This page than
could be referenced throughout the manual or READMEs every time there is
something security relevant.

> 
>> Best regards
>>
>> Christian
>>
>>>
>>> On Wed, Aug 1, 2018 at 4:04 AM, Christian Mauderer
>>> <christian.mauderer at embedded-brains.de> wrote:
>>>> ---
>>>>  freebsd/sys/sys/random.h | 10 ++++++++++
>>>>  1 file changed, 10 insertions(+)
>>>>
>>>> diff --git a/freebsd/sys/sys/random.h b/freebsd/sys/sys/random.h
>>>> index 396ec2b1..996ca5c1 100644
>>>> --- a/freebsd/sys/sys/random.h
>>>> +++ b/freebsd/sys/sys/random.h
>>>> @@ -50,11 +50,21 @@ read_random_uio(void *a __unused, u_int b __unused)
>>>>  {
>>>>         return (0);
>>>>  }
>>>> +#ifndef __rtems__
>>>>  static __inline u_int
>>>>  read_random(void *a __unused, u_int b __unused)
>>>>  {
>>>>         return (0);
>>>>  }
>>>> +#else /* __rtems__ */
>>>> +#include <unistd.h>
>>>> +static __inline u_int
>>>> +read_random(void *ptr, u_int n)
>>>> +{
>>>> +       getentropy(ptr, n);
>>>> +       return (n);
>>>> +}
>>>> +#endif /* __rtems__ */
>>>>  #endif
>>>>
>>>>  /*
>>>> --
>>>> 2.13.7
>>>>
>>>> _______________________________________________
>>>> devel mailing list
>>>> devel at rtems.org
>>>> http://lists.rtems.org/mailman/listinfo/devel
>>
>> --
>> --------------------------------------------
>> embedded brains GmbH
>> Herr Christian Mauderer
>> Dornierstr. 4
>> D-82178 Puchheim
>> Germany
>> email: christian.mauderer at embedded-brains.de
>> Phone: +49-89-18 94 741 - 18
>> Fax:   +49-89-18 94 741 - 08
>> PGP: Public key available on request.
>>
>> Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.

-- 
--------------------------------------------
embedded brains GmbH
Herr Christian Mauderer
Dornierstr. 4
D-82178 Puchheim
Germany
email: christian.mauderer at embedded-brains.de
Phone: +49-89-18 94 741 - 18
Fax:   +49-89-18 94 741 - 08
PGP: Public key available on request.

Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.