Previously calling get_num_ops more than once would have ended up with ops
getting double counted, and not calling inbetween completes would have ended up
with ops getting missed. Fix this by moving this to where the work is actually
done, and add tests for double calls to get_num_ops().
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
See docs/architecture/psa-migration/md-cipher-dispatch.md
Regarding testing, the no_md component was never very useful, as that's
not something people are likely to want to do: it was mostly useful as
executable documentation of what depends on MD. It's going to be even
less useful when more and more modules auto-enable MD_LIGHT or even
MD_C. So, recycle it to test the build with only MD_LIGHT, which is
something that might happen in practice, and is necessary to ensure that
the division is consistent.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
It was already marked as internal use only, and no longer used
internally. Also, it won't work when we dispatch to PSA.
Remove it before the MD_LIGHT split to avoid a corner case: it's
technically a hashing function, no HMAC or extra metadata, but we still
don't want it in MD_LIGHT really.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
Truncate input hashes to curve private key size as that is all that is required
for the internal implementation.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
After moving the MPIs used to output from the operation into the complete
function, I failed to move the accompanying free as well.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
Move the obfuscation of the internal library only returning a delta of ops done
into the driver wrapper, thus meaning driver wrapper and API call both return
absolute values of work done. Document the differences at the internal
implementation level.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
If an error occurs, calling any function on the same operation should return
PSA_ERROR_BAD_STATE, and we were not honouring that for all errors. Add extra
failure tests to try and ratify this.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
For sign and verify, the pointer passed in to the hash is not guaranteed to
remain valid inbetween calls, thus we need to store the hash in the
operation. Added a test to ensure this is the case.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
Set the psa level global anyway, regardless of having a built in
implementation, to match the set function. Also, ensure that value returned
is the same as value passed in, irregardless of internal implementation
requirements.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
Ensure that num_ops is cleared when manual abort is called, but obviously not
when an operation just completes, and test this.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
Move to accumulate ops in context rather than attempting to read straight out
of structures due to structure ops getting reset per operation, and also
issues with _abort clearing internal data. Fix usage of size_t in structures
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
Make public the versions of ECSDA sign and verify which return raw signatures
rather than returning ASN.1 encoded signatures, in order to use them for the
internal implemention of psa_sign/verify_hash_interruptible.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
Apply the usual parameter name and align the local variables and
comments. This naming diverges from the standard notation, but this is
beneficial as our variable meanings diverge as well and the difference
can help avoiding confusion.
Signed-off-by: Janos Follath <janos.follath@arm.com>
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
It is not necessary to save the middle limb upfront as overwriting it is
the desired result: in the first step we are reducing modulo
2^{512+biL}.
Arguably, the original flow is more intuitive and easier to see the idea
behind it.
Signed-off-by: Janos Follath <janos.follath@arm.com>
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
The prototype calculated with wrong limb size and not taken into account
the overflow in the shared limb.
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
OID subidentifiers are encoded as follow. For every byte:
* The top bit is 1 if there is another byte to come, 0 if this is the
last byte.
* The other 7 bits form 7 bits of the number. These groups of 7 are
concatenated together in big-endian order.
Overlong encodings are explicitly disallowed by the BER/DER/X690
specification. For example, the number 1 cannot be encoded as:
0x80 0x80 0x01
It must be encoded as:
0x01
Enforce this in Mbed TLS' OID DER-to-string parser.
Signed-off-by: David Horstmann <david.horstmann@arm.com>
Pacify Clang >=15 which complained:
```
include/psa/crypto.h:91:23: error: empty paragraph passed to '\retval' command [-Werror,-Wdocumentation]
* \retval #PSA_SUCCESS
~~~~~~~~~~~~~~~~~~~^
```
This commit performs the following systematic replacement:
```
perl -i -0777 -p -e 's/([\\@])(retval +\S+)\n(?! *\*? *([^\n \\*\/]|\\[cp]\b))/$1$2 ${1}emptydescription\n/g' $(git ls-files '*.[hc]' '*.function' '*.jinja')
```
i.e. add an `\emptydescription` argument to `\retval` commands (or
`@retval`, which we don't normally used) that are followed by a single word,
unless the next line looks like it contains text which would be the
description.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
The first 2 components of an OID are combined together into the same
subidentifier via the formula:
subidentifier = (component1 * 40) + component2
The current code extracts component1 and component2 using division and
modulo as one would expect. However, there is a subtlety in the
specification[1]:
>This packing of the first two object identifier components recognizes
>that only three values are allocated from the root node, and at most
>39 subsequent values from nodes reached by X = 0 and X = 1.
If the root node (component1) is 2, the subsequent node (component2)
may be greater than 38. For example, the following are real OIDs:
* 2.40.0.25, UPU standard S25
* 2.49.0.0.826.0, Met Office
* 2.999, Allocated example OID
This has 2 implications that the current parsing code does not take
account of:
1. The second component may be > 39, so (subidentifier % 40) is not
correct in all circumstances.
2. The first subidentifier (containing the first 2 components) may be
more than one byte long. Currently we assume it is just 1 byte.
Improve parsing code to deal with these cases correctly.
[1] Rec. ITU-T X.690 (02/2021), 8.19.4
Signed-off-by: David Horstmann <david.horstmann@arm.com>
IAR was warning that conditional execution could bypass initialisation of
variables, although those same variables were not used uninitialised.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
Since only a single hash algorithm is currenlty supported, this avoids
having to perform hashing more than once.
Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
A CMS signature can have internal data, but mbedTLS does not support
verifying such signatures. Reject them during parsing.
Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
Since only one content type (signed data) is supported, storing the
content type just wastes memory.
Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
The lstrlenW() function isn't available to UWP apps, and isn't necessary, since
when given -1, WideCharToMultiByte() will process the terminating null character
itself (and the length returned by the function includes this character).
Resolves#2994
Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
To better reflect what the code relies on, limit the headers that are
included when MBEDTLS_USE_PSA_CRYPTO is disabled. Also stop including
"pkwrite.h" when it is no longer needed.
Include "mbedlts/platform_util.h" unconditionally. It was only included for
RSA ALT but was also used for MBEDTLS_USE_PSA_CRYPTO (the code worked
because other headers include "mbedtls/platform_util.h").
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Under MBEDTLS_USE_PSA_CRYPTO, ecdsa_sign_wrap() was calling
mbedtls_pk_write_key_der() to write a private key in SEC1 format, only to
then extract the part that represents the private value which is what
psa_import_key() actually wants. Instead, call an mpi function to directly
get the private key in the desired format.
This slightly reduces the code size and stack usage, and removes a
dependency on pk_write.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Under MBEDTLS_USE_PSA_CRYPTO, ecdsa_verify_wrap() was calling
mbedtls_pk_write_pubkey() to write a public key in the form of a
subjectPublicKey, only to then extract the part that represents the EC
point which psa_import_key() actually wants. Instead, call an ecp
function to directly get the public key in the desired format (just the
point).
This slightly reduces the code size and stack usage, and removes a
dependency on pk_write.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Handshake should abort will illeagal parameter allert when
receiving early data extentions but the selected_identity
parsed from pre-share key isn't equal to 0.
Signed-off-by: Xiaokang Qian <xiaokang.qian@arm.com>
The contentInfo field of PKCS7 Signed Data structures can
optionally contain the content of the signature. Per RFC 2315
it can also contain any of the PKCS7 data types. Add test and
comments making it clear that the current implementation
only supports the DATA content type and the data must be empty.
Return codes should be clear whether content was invalid or
unsupported.
Identification and fix provided by:
- Demi Marie Obenour <demiobenour@gmail.com>
- Dave Rodgman <dave.rodgman@arm.com>
Signed-off-by: Nick Child <nick.child@ibm.com>
- ASN.1 parsing functions check that length don't exceed buffer bounds,
so checks `p + len > end` are redundant.
- If `p + len == end`, this is erroneous because we expect further fields,
which is automatically caught by the next ASN.1 parsing call.
Hence, the two branches handling `p + len >= end` in x509_get_other_name()
can be removed.
Further, zeroization of the `other_name` structure isn't necessary
because it's not confidential (and it's also not performed on other
error conditions in this function).
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
There were some areas where `end_signer` were being
used when it makes more sense to use `end_issuer_and_sn`,
as pointed out by demiobenour@gmail.com.
Signed-off-by: Nick Child <nick.child@ibm.com>
Several PKCS7 invalid ASN1 Tests were failing due to extra
data bytes or incorrect content lengths going unnoticed. Make
the parser aware of possible malformed ASN1 data.
Signed-off-by: Nick Child <nick.child@ibm.com>
Netscape Certificate Management System Administrator's Guide: Extension-Specific Policy Modules, Chapter 18: Extension-Specific Policy Modules, Netscape Certificate Type Extension Policy:
> The extension has no default value.
A bitstring with no flags set is still technically valid, as it will mean that the certificate has no designated purpose at the time of creation.
Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
A parsed CSR struct (`mbedtls_x509_csr`) now includes some of the
X.509v3 extensions included in the CSR -- the key usage, Netscape
cert-type, and Subject Alternative Names.
Author: Jens Alfke <jens@couchbase.com>
Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
The fix_quasi_reduction function changed to static so checking the
invalid arguments are not needed anymore.
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
Rename the function to 'fix_quasi_reduction' to better suite its functionality.
Also changed the name prefix to suite for the new module.
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
Ensure platforms that don't have an assembly implementation for
mbedtls_get_unaligned_volatile_uint32() don't experience a performance
regression.
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This path updates the clean-up logic of to individually
free each of the the group's structure members
rather than invoke `mbedtls_ecp_group_free()`.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This patch adjusts the logic, so that the method is included,
when the following components are enabled:
* MBEDTLS_ECP_DP_CURVE448_ENABLED
* MBEDTLS_ECP_DP_CURVE25519_ENABLED
* ECP_LOAD_GROUP
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This patch updates the method to not free the `grp->P`
and `grp->N` structure members.
The contents of `P` and `N` are stored in static memory at
`curve448_p/n` and `curve25519p/n` and no longer dynamically
allocated.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This patch adds two embedded constants used by `ecp_use_curve448()`.
The method has been updated to read that into an mpi instead of
calculating it on the fly.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This patch adds two embedded constants used by `ecp_use_curve25519()`.
The method has been updated to read that into an mpi instead of
calculating it on the fly.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
The key derivation algorithm PSA_ALG_TLS12_ECJPAKE_TO_PMS cannot be
used on a shared secret from a key agreement since its input must be
an ECC public key. Reject this properly.
This is tested by test_suite_psa_crypto_op_fail.generated.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
In some contexts, the output pointer may equal the first input
pointer, in which case copying is not only superfluous but results in
"Source and destination overlap in memcpy" errors from Valgrind (as I
observed in the context of ecp_double_jac) and a diagnostic message
from TrustInSoft Analyzer (as Pascal Cuoq reported in the context of
other ECP functions called by cert-app with a suitable certificate).
Signed-off-by: Aaron M. Ucko <ucko@ncbi.nlm.nih.gov>
When ticket_flags used as parameter, use unsigned int,
instead of uint8_t or mbedtls_ssl_tls13_ticket_flags.Also
remove the definition of mbedtls_ssl_tls13_ticket_flags.
Signed-off-by: Pengyu Lv <pengyu.lv@arm.com>
Return MBEDTLS_ERR_ERROR_GENERIC_ERROR when ticket_flags
are not compatible with advertised key exchange mode.
Signed-off-by: Pengyu Lv <pengyu.lv@arm.com>
Ticket flags is quite generic and may make sense in the
future versions of TLS or even in TLS 1.2 with new
extensions. This change remane the ticket_flags helper
functions with more generic `mbedtls_ssl_session` prefix
instead of `mbedtls_ssl_tls13_session`.
Signed-off-by: Pengyu Lv <pengyu.lv@arm.com>
Handshake parameter field, tls13_kex_mode is only valid when
MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED is set.
So, any functions / calls should be guarded by this macros.
Signed-off-by: Pengyu Lv <pengyu.lv@arm.com>
Move the kex mode check in ticket_flags to
ssl_tls13_offered_psks_check_identity_match_ticket and add new error
'MBEDTLS_ERR_SSL_TICKET_INVALID_KEX_MODE' to indicate the check
failure.
Signed-off-by: Pengyu Lv <pengyu.lv@arm.com>
The server check if the ticket_flags is compatible with the advertised
key exchange modes in Pre-Shared Key Exchange Modes extension. The
incompatible ticket should be mark as not matched.
Signed-off-by: Pengyu Lv <pengyu.lv@arm.com>
- added 2 new certificates: 1 for testing a serial which is full lenght
and another one for a serial which starts with 0x80
- added also proper Makefile and openssl configuration file to generate
these 2 new certificates
Signed-off-by: Valerio Setti <vsetti@baylibre.com>
- enhance mbedtls_x509write_crt_set_serial(): avoid use of useless
temporary buffer
- fix mbedtls_x509write_crt_der(): add an extra 0x00 byte at the
beginning of serial if the MSb of serial is 1, as required from
ASN.1
Signed-off-by: Valerio Setti <vsetti@baylibre.com>
We provide windows and posix implementation for it.
With MBEDTLS_PLATFORM_MS_TIME_ALT, user can provide
their own implementation.
Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
As some static functions are only used inside ssl_tls13_keys.c,
the prefix mbedtls_ should be removed. Furthermore, code format is
also maintained to fix code style.
Signed-off-by: Yanray Wang <yanray.wang@arm.com>
Since some functions are only used in ssl_tls13_keys.c not by any
other modules, those functions are changed to static.
Signed-off-by: Yanray Wang <yanray.wang@arm.com>
Since tls13_early_secrets is only temperately used in the function,
there is no need to keep it in the handshake context.
Signed-off-by: Yanray Wang <yanray.wang@arm.com>
We're including psa/crypto_values.h, which defines the necessary error
codes. Remove redundant definitions, which hurt because they need to be
styled in exactly the same way (same presence/absence of spaces between
tokens).
This completes the fix of https://github.com/Mbed-TLS/mbedtls/issues/6875.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Move the *INDENT-ON* annotation to the end of the file so that
uncrustify does not restyle the later sections (since it introduces a
risk of future problems).
Signed-off-by: David Horstmann <david.horstmann@arm.com>
The inline assembly defined in bn_mul.h confuses code style parsing,
causing code style correction to fail. Disable code style correction for
the whole section gated by "#if defined(MBEDTLS_HAVE_ASM)" to prevent
this.
Signed-off-by: David Horstmann <david.horstmann@arm.com>
Some PSA curves' symbols (PSA_WANT_) were not matching the corresponding
MBEDTLS_ECP_DP_. This was fixed together with the removal of extra code
when DEBUG_C is not enabled.
Signed-off-by: Valerio Setti <vsetti@baylibre.com>
The following code:
#ifndef asm
#define asm __asm
#endif
causes Uncrustify to stop correcting the rest of the file. This may be
due to parsing the "asm" keyword in the definition.
Work around this by wrapping the idiom in an *INDENT-OFF* comment
wherever it appears.
Signed-off-by: David Horstmann <david.horstmann@arm.com>
Used to be private, hence the duplication, but that's been fixed in the
meantime, I guess we just missed this occurrence.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
mbedtls_mpi_mod_raw_random() and mbedtls_mpi_mod_random() were producing
output in the Montgomery representation, instead of obeying the
representation chosen in the modulus structure. Fix this.
Duplicate the test cases for mod-random output to have separate test cases
for each representation.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Call mbedtls_mpi_mod_raw_canonical_to_modulus_rep instead of assuming that
anything that isn't MBEDTLS_MPI_MOD_REP_MONTGOMERY is canonical.
mbedtls_mpi_mod_write should get the same treatment, but I'm holding off
until https://github.com/Mbed-TLS/mbedtls/issues/6679 is done.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
In the basic/XXX=core test cases, use odd upper bounds, because the mod
version of random() only supports odd upper bounds (the upper bound is a
modulus and the mod modules only support odd moduli).
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Using proper configuration options (i.e. MBEDTLS_SHA224_C and
MBEDTLS_SHA256_C) it is now possible to build SHA224 and SHA256
independently from each other.
Signed-off-by: Valerio Setti <vsetti@baylibre.com>
This is meant to adapt to the new library design in which
SHA384 and SHA512 can be built independently from each other.
Signed-off-by: Valerio Setti <vsetti@baylibre.com>
Using proper configuration options (i.e. MBEDTLS_SHA384_C and
MBEDTLS_SHA512_C) it is now possible to build SHA384 and SHA512
independently from each other.
Signed-off-by: Valerio Setti <vsetti@baylibre.com>
This fixes the two failing cases in test_suite_pk when ECP_RESTARTABLE
and USE_PSA_CRYPTO are both enabled. The two failing cases where
ECDSA restartable sign/verify: ECDSA, max_ops=0 (disabled)
ECDSA restartable sign/verify: ECKEY, max_ops=0 (disabled)
associated with test function pk_sign_verify_restart(). The failure was
caused by the interaction of several things that are each reasonable on
their own:
1. The test function relies on ECDSA restartable, which is reasonable as it
allows making sure that the generated signature is correct with a simple
memcmp().
2. The implementation of pk_sign_restartable() has a shortcut to
dispatch to the sign function (as opposed to sign_restartable) when
restart is disabled (max_ops == 0).
3. When USE_PSA is enabled, the sign function dispatches to PSA, which
so far always used ECDSA (non-deterministic) even when the non-PSA
version would use deterministic ECDSA.
This could be fixed by changing any of those. I chose (3) because I
think it makes sense that when PK dispatches to PSA instead of legacy
this should not change which version of ECDSA is selected.
OTOH, I think it makes sense to keep (2), because that means more
opportunities to dispatch to PSA.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
- disable reuse of max_early_data_size.
- make conf_early_data available for server.
- various comment issues
Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
Shuffle things around a bit inside mbedtls_mpi_random() in preparation for
breaking out mbedtls_mpi_core_random().
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Rewrite the minimum bound comparison to avoid a local allocation. This costs
a bit of code size, but saves RAM. This is in preparation for moving the
bulk of the function to the bignum_core module where allocation is not
permitted.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Compare a single-limb MPI with a multi-limb MPI. This is rather ad hoc, but
will be useful for mbedtls_mpi_core_random.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This may have been a use-after-free, but I haven't worked out whether it was
a problem or not. Even if it turns out to have been ok, keeping invalid
pointers around is fragile.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Require equality for the number of limbs in the modulus and the residue.
This makes these functions consistent with residue_setup().
Signed-off-by: Janos Follath <janos.follath@arm.com>
The function isn't documented as accepting null pointer, and there's no
reason why it should be. Just let it dereference the pointer.
The null/zero checks are only marginally useful: they validate that m
and r are properly populated objects, not freshly initialized ones. For
that, it's enough to check that the pointers aren't null or that the
sizes aren't zero, we don't need to check both.
Also, use separate if statements for unrelated checks.
Signed-off-by: Janos Follath <janos.follath@arm.com>
The external representation before included more than just endianness
(like reading in Mongtomery curve scalars or converting hashes to
numbers in a standard compliant way).
These are higher level concepts and are out of scope for Bignum and for
the modulus structure.
Signed-off-by: Janos Follath <janos.follath@arm.com>
The external representation before included more than just endianness
(like reading in Mongtomery curve scalars or converting hashes to
numbers in a standard compliant way).
These are higher level concepts and are out of scope for Bignum and for
the modulus structure.
Passing endianness as a parameter is a step towards removing it from the
modulus structure.
Signed-off-by: Janos Follath <janos.follath@arm.com>
The external representation before included more than just endianness
(like reading in Mongtomery curve scalars or converting hashes to
numbers in a standard compliant way).
These are higher level concepts and are out of scope for Bignum and for
the modulus structure.
Passing endianness as a parameter is a step towards removing it from the
modulus structure.
Signed-off-by: Janos Follath <janos.follath@arm.com>
In theory we could allow residues to have more allocated limbs than the
modulus, but we might or might not need it in the end.
Go for the simpler option for now and we can extend it later if we
really need it.
Signed-off-by: Janos Follath <janos.follath@arm.com>
We want to make sure that the value has at least as many limbs allocated
as the modulus as we need this to be able to do any operations in
constant time.
An invariant of the API is that the residue values are canonical, make
sure that the residue is compared to the entire modulus.
Signed-off-by: Janos Follath <janos.follath@arm.com>
This patch adjusts the I/O methods and the tests.
Documentation has also been updated to be more clear.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This patch adjusts the logic of the size checking of the method,
and refactors the tests. Documentation has also been updated.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This patch is inverting the input type checking logic in the method,
in order to ensure that residue < modulus.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This patch adds input and ouput fucntions in the `bignum_mod` layer.
The data will be automatically converted between Cannonical and
Montgomery representation if required.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
When legacy CID is enabled at compile time, but not used at runtime, we
would incorrectly skip the sequence number at the beginning of the AAD.
There was already two "else" branches for writing the sequence number
but none of them was taken in that particular case.
Simplify the structure of the code: with TLS 1.2 (we're already in that
branch), we always write the sequence number, unless we're using
standard CID.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
