- The underlying test vectors are for Secp192r1, while TinyCrypt uses Secp256r1.
- The test implementation is specific to the structure of legacy-ECC PK ctxs.
Addition of analogous tests for TinyCrypt-based ECC PK contexts are left
for a later commit.
PEM-encoded keys with PEM header
-----BEGIN EC PRIVATE KEY-----
...
-----END EC PRIVATE KEY-----
were previously not parsed in configurations using TinyCrypt
instead of legacy ECC crypto.
The PK type MBEDTLS_PK_ECDSA is never returned from
`mbedtls_pk_info_from_type()`. Instead, EC keys either
are identified as MBEDTLS_PK_ECKEY_DH (in case they
must only be used for ECDHE) or MBEDTLS_PK_ECKEY (in
case they can be used for any algorithm).
With TinyCrypt and legacy ECC mutually exclusive, we don't have
to use #if TINYCRYPT #else #if LEGACY #endif #endif anymore, but
can add the TC and legacy based ECC implementations independently.
- TinyCrypt uses `0` for errors.
- The first argument to uECC_verify() should be the public key,
but the previous code passed the beginning of the entire
private-public key structure.
The PK-type MBEDTLS_PK_ECDSA isn't really used by the library.
Especially, when parsing a generic EC key, a PK context of type
MBEDTLS_PK_ECKEY will be requested. Hence, to drop in TinyCrypt
for the legacy-ECC implementation, the PK type that TinyCrypt
implements must be MBEDTLS_PK_ECKEY.
TinyCrypt should be used as a replacement of legacy ECC. In particular,
there shouldn't be any use of identifiers from the legacy ECC module.
So far, there's the configuration option
MBEDTLS_SSL_CONF_SINGLE_EC_GRP_ID
that's relevant if MBEDTLS_SSL_CONF_SINGLE_CURVE is set, and which in
this case must resolve to an identifier of type mbedtls_ecp_group_id
indicating which single curve to enable.
With the introduction of TinyCrypt, we must either change the type
of this option to mbedtls_uecc_group_id, or introduce a separate
compilation option.
In order to avoid type confusion, this commit follows tha latter
approach, introducing the configuration option
MBEDTLS_SSL_CONF_SINGLE_UECC_GRP_ID
that indicatesthe TinyCrypt group identifier of the single curve
to use (must be Secp256r1) if MBEDTLS_SSL_CONF_SINGLE_CURVE
and MBEDTLS_USE_TINYCRYPT are set.
So far, ssl_client2 and ssl_server2 were relying on MBEDTLS_CTR_DRBG_C
being set. This commit adapts them to use HMAC DRBG in case CTR DRBG
is disabled in the configuration.
Note that disabling CTR DRBG in favor of HMAC DRBG can be useful on
constrained systems because Mbed TLS' HMAC DRBG is slightly smaller,
and moreover needed anyway as part of deterministic ECDSA.
