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

[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.

> 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
>
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