This commit changes the internal identifiers
MBEDTLS_SSL_MINOR_VERSION_XXX
in DTLS-only builds to match the version encoding used by the
DTLS standard, encoding DTLS 1.0 as 255 and DTLS 1.2 as DTLS 1.0.
Accordingly, the version comparison functions introduced in the
previous commit must be re-implemented, as older version have
_larger_ identifiers now.
Further, since we identify DTLS 1.0 as MBEDTLS_SSL_MINOR_VERSION_2
and DTLS 1.2 as MBEDTLS_SSL_MINOR_VERSION_3, what remains is to
define MBEDTLS_SSL_MINOR_VERSION_{0|1}. While these don't have any
meaning meaning in DTLS, they still need to be set and obey the
ordering in the sense that the version comparison functions '<='
should attest that
MBEDTLS_SSL_MINOR_VERSION_i '<=' MBEDTLS_SSL_MINOR_VERSION_j
for i <= j. Since '<=' is actually >= and the wire format value
for DTLS 1.0 == MBEDTLS_SSL_MINOR_VERSION_2 is the 255, this
forces us to use values beyond 255, and hence to extend the
storage type for minor versions from uint8_t to uint16_t.
Previously, ecp.h was included only if MBEDTLS_ECDH_C was set,
which broke the build in configurations using ECDSA, but not ECDH.
An example of such a config is configs/config-thread.h, which
uses ECJPAKE exclusively.
Moreover, the inclusion of ecdh.h isn't needed, because the header
only uses constants defined in the ECP module.
Remark: Including ecp.h is actually redundant because it's
also included from ecdh.h. However, it's good practice to
explicitly include header files that are being used directly,
and ssl.h does use MBEDTLS_ECP_MAX_BYTES which is defined in ecp.h.
ssl.h contains a dummy union of fields each large enough to
hold the PMS for a particular ciphersuite. In particular, for
pure-ECDH ciphersuites, it contains a field large enough to
hold the ECDH shared secret in any of the enabled curves.
So far, this upper bound was unconditionally chosen to be
MBEDTLS_ECP_MAX_BYTES from the ECP module.
With the introduction of TinyCrypt as an alternative implementation
for ECDH, we need to
- guard the use of MBEDTLS_ECP_MAX_BYTES because MBEDTLS_ECP_C
is no longer implied by the surrounding MBEDTLS_KEY_EXCHANGE_XXX
guards
- add another field which contains the maximum length of shared
ECDH secrets for curves supported by TinyCrypt.
Now function mbedtls_ssl_set_hostname is compile-time configurable
in config.h with define MBEDTLS_X509_REMOVE_HOSTNAME_VERIFICATION.
This affects to many x509 API's. See config.h for details.
After the rewrite of incoming record processing to use the internal
SSL record structure mbedtls_record (which contains the data_offset
field to indicate where the IV resides), this field is no longer
necessary.
Note: This is an API break.
The code wants timer callbacks to be set (checked in fetch_input()), and can't
easily check whether we're using nbio, so it seems easier to require the
callbacks to be always set rather than only with nbio as was previously done.
The number of meaning of the flags will be determined later, when handling the
relevant struct members. For now three bytes are reserved as an example, but
this number may change later.
Enforce restrictions indicated in the documentation.
This allows to make some simplifying assumptions (no need to worry about
saving IVs for CBC in TLS < 1.1, nor about saving handshake data) and
guarantees that all values marked as "forced" in the design document have the
intended values and can be skipped when serialising.
Some of the "forced" values are not checked because their value is a
consequence of other checks (for example, session_negotiated == NULL outside
handshakes). We do however check that session and transform are not NULL (even
if that's also a consequence of the initial handshake being over) as we're
going to dereference them and static analyzers may appreciate the info.
This commit introduces the option MBEDTLS_SSL_CONF_SINGLE_HASH
which can be used to register a single supported signature hash
algorithm at compile time. It replaces the runtime configuration
API mbedtls_ssl_conf_sig_hashes() which allows to register a _list_
of supported signature hash algorithms.
In contrast to other options used to hardcode configuration options,
MBEDTLS_SSL_CONF_SINGLE_HASH isn't a numeric option, but instead it's
only relevant if it's defined or not. To actually set the single
supported hash algorithm that should be supported, numeric options
MBEDTLS_SSL_CONF_SINGLE_HASH_TLS_ID
MBEDTLS_SSL_CONF_SINGLE_HASH_MD_ID
must both be defined and provide the TLS ID and the Mbed TLS internal
ID and the chosen hash algorithm, respectively.
This commit introduces the option MBEDTLS_SSL_CONF_SINGLE_EC
which can be used to register a single supported elliptic curve
at compile time. It replaces the runtime configuration API
mbedtls_ssl_conf_curves() which allows to register a _list_
of supported elliptic curves.
In contrast to other options used to hardcode configuration options,
MBEDTLS_SSL_CONF_SINGLE_EC isn't a numeric option, but instead it's
only relevant if it's defined or not. To actually set the single
elliptic curve that should be supported, numeric options
MBEDTLS_SSL_CONF_SINGLE_EC_TLS_ID
MBEDTLS_SSL_CONF_SINGLE_EC_GRP_ID
must both be defined and provide the TLS ID and the Mbed TLS internal
ID and the chosen curve, respectively.
If the minor/major version is enforced at compile-time, the `major_ver`
and `minor_ver` fields in `mbedtls_ssl_context` are redundant and can
be removed.
This commit introduces the numeric compile-time constants
- MBEDTLS_SSL_CONF_MIN_MINOR_VER
- MBEDTLS_SSL_CONF_MAX_MINOR_VER
- MBEDTLS_SSL_CONF_MIN_MAJOR_VER
- MBEDTLS_SSL_CONF_MAX_MAJOR_VER
which, when defined, overwrite the runtime configurable fields
mbedtls_ssl_config::min_major_ver etc. in the SSL configuration.
As for the preceding case of the ExtendedMasterSecret configuration,
it also introduces and puts to use getter functions for these variables
which evaluate to either a field access or the macro value, maintaining
readability of the code.
The runtime configuration API mbedtls_ssl_conf_{min|max}_version()
is kept for now but has no effect if MBEDTLS_SSL_CONF_XXX are set.
This is likely to be changed in a later commit but deliberately omitted
for now, in order to be able to study code-size benefits earlier in the
process.
If MBEDTLS_SSL_SINGLE_CIPHERSUITE is enabled, the type
mbedtls_ssl_ciphersuite_handle_t
is logically a boolean (concretely realized as `unsigned char`),
containing the invalid handle and the unique valid handle, which
represents the single enabled ciphersuite.
The SSL session structure mbedtls_ssl_session contains an instance
of mbedtls_ssl_ciphersuite_handle_t which is guaranteed to be valid,
and which is hence redundant in any two-valued implementation of
mbedtls_ssl_ciphersuite_handle_t.
This commit replaces read-uses of
mbedtls_ssl_session::ciphersuite_info
by a getter functions which, and defines this getter function
either by just reading the field from the session structure
(in case MBEDTLS_SSL_SINGLE_CIPHERSUITE is disabled), or by
returning the single valid ciphersuite handle (in case
MBEDTLS_SSL_SINGLE_CIPHERSUITE is enabled) and removing the
field from mbedtls_ssl_session in this case.
If MBEDTLS_SSL_SINGLE_CIPHERSUITE is enabled, it overwrites
the runtime configuration of supported ciphersuites, which
includes both the configuration API and the fields which are
used to store the configuration. Both are therefore no longer
needed and should be removed for the benefit of code-size,
memory usage, and API clarity (no accidental hiccup of runtime
vs. compile-time configuration possible).
The configuration API mbedtls_ssl_conf_ciphersuites() has
already been removed in case MBEDTLS_SSL_SINGLE_CIPHERSUITE,
and this commit removes the field
mbedtls_ssl_config::ciphersuite_list
which it updates.
Previously, ssl.h included ssl_ciphersuites.h to have access to the
helper macros MBEDTLS_KEY_EXCHANGE_XXX_ENABLED, and for no other
reason. This commit moves the definitions of these macros to ssl.h,
thereby removing the dependency of ssl.h on ssl_ciphersuites.h.
