So far, with MBEDTLS_SSL_KEEP_PEER_CERTIFICATE disabled, the SSL module relied
on a undocumented feature of the PK module: that you can distinguish between
contexts that have been setup and context that haven't. This feature is going
to go away in the case of PK_SINGLE_TYPE, as we'll soon (as in: the next
commit does that) no longer be storing the (now two-valued) pk_info member.
Note even with this change, we could still distinguish if the context has been
set up by look if pk_ctx is NULL or not, but this is also going away in the
near future (a few more commits down the road), so not a good option either.
This is the first in a series of commit aimed at removing the pk_info
structures when we're building with MBEDTLS_PK_SINGLE_TYPE enabled.
Introducing this abstraction allows us to later make it a two-valued type
(valid, invalid) instead, which is much lighter.
-Fix MSVC compiler warnings about size_t to uint32_t conversions by
updating GET/PUT functions signature to use size_t.
-Add type casts to functions calling GET/PUT conversions
-Remove additional space after return statement
Previously, TinyCrypt was only used for ECDHE-ECDSA/RSA ciphersuites.
This commit is a step towards using it for _all_ ciphersuites involving
ECDHE (specifically: ECDHE, ECDHE-PSK, static ECDH), extending the scope
of the use of TinyCrypt in the parsing of the ClientKeyExchange message.
Previously, TinyCrypt was only used for ECDHE-ECDSA/RSA ciphersuites.
This commit is a step towards using it for _all_ ciphersuites involving
ECDHE (specifically: ECDHE, ECDHE-PSK, static ECDH), extending the scope
of the use of TinyCrypt in the writing of the ServerKeyExchange message.
mbedtls/ecp.h defines constants
MBEDTLS_ECP_PF_UNCOMPRESSED
MBEDTLS_ECP_PF_COMPRESSED
MBEDTLS_ECP_TLS_NAMED_CURVE
which regard the encoding of elliptic curves and curve point formats in TLS.
As such, they should be defined in the SSL namespace. Asides, this will help
replacing the legacy ECC crypto by alternative ECC implementations.
The use of tinyCrypt is restricted Secp256r1-only, and a check in
ssl_ciphersuite_is_match() ensures that an EC ciphersuite is chosen
only if the client advertised support for Secp256r1, too.
In a way inconsistent with the rest of the library restricting the
use of tinyCrypt to pure-ECDHE, the previous ServerKeyExchange writing
routine would use tinyCrypt also for ECDHE-PSK-based ciphersuites.
This commit fixes this.
Previously, MBEDTLS_KEY_EXCHANGE_ECDH[E]_XXX_ENABLED would imply
that MBEDTLS_ECDH_C is set, but with the introduction of tinyCrypt
as an alternative ECDH implementation, this is no longer the case.
Eventually, all HS parsing/writing functions should take an arbitrary buffer +
length pair as their argument, and return MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL if
the provided buffer is too short. So far, we've only made a first step by
allowing to pass an arbitrary buffer, but don't yet add bounds checks
throughout. While deliberate for now, this must be clearly documented.
This makes grepping the functions more difficult, and also leads to compilation failures
when trying to build the library from a single source file (which might be useful for
code-size reasons).
The postprocessing code for the server-side incoming client key
exchange and the client-side outgoing client key exchange both
contain the same code-paths for building the premaster secret
depending on the chosen ciphersuite (e.g., for ECDHE-PSK,
concatenating the ECDHE secret with the chosen PSK).
This commit moves this common code to ssl_tls.c, allowing
client- and server-side to share it.
The code from the previous function ssl_parse_client_key_exchange()
has been entirely moved to one of the newly introduced subroutines
and is no longer needed. This commit removes it.
After parsing and performing key generation operations,
the server-side incoming ClientKeyExchange handling includes
code-paths to assembly the PreMasterSecret (PMS) from the
available keying material, the exact assembly procedure
depending on which ciphersuite is in use. E.g., in an
(EC)DHE-PSK ciphersuite, the (EC)DHE secret would be concatenated
with the PSK to form the PMS.
This assembly of the PMS logically comes done after the ClientKeyExchange
has been parsed and the respective keying material has been generated,
and this commit moves it to the new postprocessing function
ssl_client_key_exchange_postprocess().
This commit moves the generation of the master secret and session keys
from the premaster secret (done in mbedtlsssl_derive_keys()) from the
previous ClientKeyExchange parsing function ssl_parse_client_key_exchange()
to the new postprocessing function ssl_client_key_exchange_postprocess().
