mirror/mbedtls
1
0
Fork 0
mirror of https://github.com/Mbed-TLS/mbedtls.git synced 2025-04-17 11:43:37 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Misc updates to strategy.md

Browse Source 
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
This commit is contained in:
Manuel Pégourié-Gonnard 2022-02-01 10:34:20 +01:00
parent 8e559daaa8
commit ce6c0875d1
1 changed files with 12 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
docs/architecture/psa-migration/strategy.md
View File

@ -39,7 +39,10 @@ We currently have two compile-time options that are relevant to the migration:
The reasons why `MBEDTLS_USE_PSA_CRYPTO` is optional and disabled by default The reasons why `MBEDTLS_USE_PSA_CRYPTO` is optional and disabled by default
are: are:
- it's incompatible with `MBEDTLS_ECP_RESTARTABLE`, and `MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER`; - it's incompatible with `MBEDTLS_ECP_RESTARTABLE`;
- historical: used to be incompatible
`MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER` (fixed early 2022, see
<https://github.com/ARMmbed/mbedtls/issues/5259>);
- it does not work well with `MBEDTLS_PSA_CRYPTO_CONFIG` (could compile with - it does not work well with `MBEDTLS_PSA_CRYPTO_CONFIG` (could compile with
both of them, but then `MBEDTLS_PSA_CRYPTO_CONFIG` won't have the desired both of them, but then `MBEDTLS_PSA_CRYPTO_CONFIG` won't have the desired
effect) effect)
@ -47,10 +50,13 @@ effect)
`MBEDTLS_PSA_CRYPTO_C`, for backards compatibility reasons: `MBEDTLS_PSA_CRYPTO_C`, for backards compatibility reasons:
- when `MBEDTLS_PSA_CRYPTO_C` is enabled and used, applications need to call - when `MBEDTLS_PSA_CRYPTO_C` is enabled and used, applications need to call
`psa_crypto_init()` before TLS/X.509 uses PSA functions `psa_crypto_init()` before TLS/X.509 uses PSA functions
- `MBEDTLS_PSA_CRYPTO_C` has a hard depend on `MBEDTLS_ENTROPY_C` but it's - `MBEDTLS_PSA_CRYPTO_C` has a hard depend on `MBEDTLS_ENTROPY_C ||
currently possible to compilte TLS and X.509 without `MBEDTLS_ENTROPY_C`. MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG` but it's
currently possible to compilte TLS and X.509 without any of the options.
Also, we can't just auto-enable `MBEDTLS_ENTROPY_C` as it doesn't build Also, we can't just auto-enable `MBEDTLS_ENTROPY_C` as it doesn't build
out of the box on all platforms. out of the box on all platforms, and even less
`MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG` as it requires a user-provided RNG
function.
The downside of this approach is that until we feel ready to make The downside of this approach is that until we feel ready to make
`MBDEDTLS_USE_PSA_CRYPTO` non-optional (always enabled), we have to maintain `MBDEDTLS_USE_PSA_CRYPTO` non-optional (always enabled), we have to maintain
@ -82,6 +88,8 @@ restartable behaviour was requested at run-time (in addition to enabling
### `MBEDTLS_PSA_CRYPTO_CONFIG` ### `MBEDTLS_PSA_CRYPTO_CONFIG`
(This section taken from a comment by Gilles.)
X509 and TLS code use `MBEDTLS_xxx` macros to decide whether an algorithm is X509 and TLS code use `MBEDTLS_xxx` macros to decide whether an algorithm is
supported. This doesn't make `MBEDTLS_USE_PSA_CRYPTO` incompatible with supported. This doesn't make `MBEDTLS_USE_PSA_CRYPTO` incompatible with
`MBEDTLS_PSA_CRYPTO_CONFIG` per se, but it makes it incompatible with most `MBEDTLS_PSA_CRYPTO_CONFIG` per se, but it makes it incompatible with most
@ -106,22 +114,6 @@ to the existing code and the less code there is at this point the better,
whereas extending to more procotol features will require the same amount of whereas extending to more procotol features will require the same amount of
work either way. work either way.
### `MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER`
When `MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER` is enabled, the library is
built for use with an RPC server that dispatches PSA crypto function calls
from multiple clients. In such a build, all the `psa_xxx` functions that take
would normally take a `psa_key_id_t` as argument instead take a structure
containing both the key id and the client id. And so if e.g. a TLS function
calls `psa_import_key`, it would have to pass this structure, not just the
`psa_key_id_t` key id.
A solution is to use `mbedtls_svc_key_id_t` throughout instead of
`psa_key_id_t`, and use similar abstractions to define values.
That's what we're implemementing in early 2022, see
https://github.com/ARMmbed/mbedtls/issues/5259
### Backwars compatibility issues with making it always on ### Backwars compatibility issues with making it always on
1. Existing applications may not be calling `psa_crypto_init()` before using 1. Existing applications may not be calling `psa_crypto_init()` before using