Specifically allow the driver to override the persistency level of a
builtin key in cases where the driver is persistency-aware.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Time stamps are useful when the document gets shared around, but they
tend to lead to merge conflicts.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
While builtin keys will often have a fixed-size context, this is not
necessarily the case, so the "get_builtin_key" entry point needs to
return the size of the actual key context.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
If a random driver has a built-in entropy source and doesn't need an
external entropy source, make the driver author declare this
explicitly, rather than it being a less secure default.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
The get_random entry point was allowed to return partial data on both
PSA_SUCCESS and PSA_ERROR_INSUFFICIENT_ENTROPY, but there was no
meaningful difference between the two. Keep it simple: PSA_SUCCESS is
success but can be partial, and PSA_ERROR_INSUFFICIENT_ENTROPY is an
error with no output.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Explicitly recommend that the driver accounts for environmental
conditions that can affect the amount of entropy.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
A random generation driver does not need to support entropy injection.
This will limit it to platforms where the RNG peripheral is the sole
entropy source and without an RNG seed saved into persistent storage.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
If an RNG peripheral includes an entropy source, it would presumably
declare "initial_entropy_size" and "reseed_entropy_size" to be 0. In
this case, don't require the core to call "add_entropy".
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
The `get_entropy` entry point can be provided by multiple transparent
drivers, and the core will call all of them. But apart from that,
`get_entropy` doesn't involve an opaque key or a location, so it can
be in a transparent driver.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Transparent drivers may provide a DRBG interface through "add_entropy"
and "get_random" entry points. This interface may also be used with a
non-deterministic generator, for chips that include a TRNG.
Opaque driver may provide a "get_entropy" entry point.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Allow the core to call the "get_builtin_key" entry point to retrieve
the attributes of a built-in key. This is useful to implement
psa_get_key_attributes(), and also when the key data buffer's size
depends on the key type and size.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Having a time stamp identifying each revision of the document is
useful, but it's also a pain because it creates a conflict whenever
there are multiple pending changes at the same time. The gain isn't
worth the pain, so I'm removing the time stamp.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Rework the section describing key import, in particular to clarify key
size determination and checking. There is no intended semantic change.
Note an open question around support for implementation-specific
import formats.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
