This commit adds support for the use of PSA-based opaque PSKs
in the TLS client example application programs/ssl/ssl_client2.
Specifically, a numerical command line option `psk_slot` with
the following constraints and semantics is added:
- It can only be used alongside the provisioning of a raw PSK
through the preexisting `psk` command line option.
- It can only be used if both TLS 1.2 and a PSK-only ciphersuite
are enforced through the appropriate use of the `min_version`
and `force_ciphersuite` command line options.
- If the previous conditions are met, setting `psk_slot=d` will
result in the PSA key slot with identifier `d` being populated
with the raw PSK data specified through the `psk` parameter
and passed to Mbed TLS via `mbedtls_ssl_conf_psk_opaque()`
prior to the handshake.
Enforcing the TLS version and ciphersuite is necessary to determine
the exact KDF algorithm the PSK will be used for. This is required
as it is currently not possible to set up a key without specifying
exactly one algorithm the key may be used with.
This commit adds a field `psk_opaque` to the handshake parameter
struct `mbedtls_ssl_handshake_params` which indicates if the user
has configured the use of an opaque PSK.
This commit adds two public API functions
mbedtls_ssl_conf_psk_opaque()
mbedtls_ssl_set_hs_psk_opaque()
which allow to configure the use of opaque, PSA-maintained PSKs
at configuration time or run time.
In case of AEAD ciphers, the cipher mode (and not even the entire content
of mbedtls_cipher_info_t) doesn't uniquely determine a psa_algorithm_t
because it doesn't specify the AEAD tag length, which however is included
in psa_algorithm_t identifiers.
This commit adds a tag length value to mbedtls_psa_translate_cipher_mode()
to account for that ambiguity.
This commit adds the header file mbedtls/psa_util.h which contains
static utility functions `mbedtls_psa_xxx()` used in the integration
of PSA Crypto into Mbed TLS.
Warning: These functions are internal only and may change at any time.
When running `make install`, it can be desirable for the PSA Crypto header
files to get installed as well, so that the PSA portions of the library are
usable.
Note that one can also use CMake and doesn't strictly require GNU Make. For
instance, telling CMake to output Visual Studio project files and using
those would preclude the need for GNU Make.
For Makefiles, enable overriding where includes can come from in order to
enable the parent module to set the include path. This allows the parent
module to specify that its config.h should be used, even when the submodule
when built standalone would use a different config.h.
For CMake, always look in the parent's include folder and our own. List the
parent's include folder first, so that preference is given to parent
include files.
Move our Mbed Crypto README out from the crypto folder and up to the top
level for better visibility when using Mbed Crypto as a submodule of Mbed
TLS.
When building Mbed Crypto as a subproject, don't add targets for
libmbedx509 or libmbedtls, as the parent project should build these. The
parent project will define USE_CRYPTO_SUBMODULE variable when using Mbed
Crypto as a submodule, so we can depend on that variable to control whether
or not we build non-crypto libraries.
The new file is conditionally compiled with the new mbedtls
configuration option that Mbed OS would set by default -
`MBEDTLS_PSA_CRYPTO_STORAGE_ITS_C`.
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