mbedtls_ssl_{get,set}_session() exhibited idempotent behaviour
in Mbed TLS 2.x. Multiple calls to those functions are not useful
in TLS 1.2, and the idempotent nature is unsuitable for support of
TLS 1.3 which introduces the availabilty to offer multiple tickets
for resumption, as well as receive multiple tickets.
In preparation for TLS 1.3 support, this commit relaxes the semantics
of `mbedtls_ssl_{get,set}_session()` by allowing implementations to
fail gracefully, and leveraging this freedom by modifying the
existing TLS 1.2 implementation to only accept one call to
`mbedtls_ssl_{get,set}_session()` per context, and non-fatally
failing all subsequent invocations.
For TLS 1.3, it will be leveraged by making multiple calls to
`mbedtls_ssl_get_session()` issue one ticket a time until no more
tickets are available, and by using multiple calls to
`mbedtls_ssl_set_session()` to allow the client to offer multiple
tickets to the server.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
Remove a kludge to avoid a warning in GCC 11 when calling
mbedtls_sha512_finish_ret with a 48-byte output buffer. This is correct
since we're calculating SHA-384. When mbedtls_sha512_finish_ret's output
parameter was declared as a 64-byte array, GCC 11 -Wstringop-overflow
emitted a well-meaning, but inaccurate buffer overflow warning, which we
tried to work around (successfully with beta releases but unsuccessfully
with GCC 11.1.0 as released). Now that the output parameter is declared as a
pointer, no workaround is necessary.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
The server-side `Certificate` handshake message writer checks
whether a certificate is present, and if not fails with:
```
MBEDTLS_ERR_SSL_CERTIFICATE_REQUIRED
```
This should never happen, since the library checks the presence
of a suitable certificate before picking a ciphersuite. It is
therefore more suitable to convert this check into an assertion,
and fail with MBEDTLS_ERR_SSL_INTERNAL_ERROR upon failure.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
The error code MBEDTLS_ERR_SSL_INVALID_VERIFY_HASH is only
returned from the internal function
```
mbedtls_ssl_set_calc_verify_md()
```
Moreover, at every call-site of this function, it is only
checked whether the return value is 0 or not, while the
exact return value is irrelevant.
The behavior the library is therefore unchanged if we return 1
instead of MBEDTLS_ERR_SSL_INVALID_VERIFY_HASH in
`mbedtls_ssl_set_calc_verify_md()`. This commit makes this change.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
This error is used when the output buffer isn't large enough
to hold our own certificate.
In the interest of cleaning up the error space for 3.0, this commit
removes MBEDTLS_ERR_SSL_CERTIFICATE_TOO_LARGE and replaces its single
use by MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
Although SHA512 is currently required to enable SHA384, this
is expected to change in the future. This commit is an
intermediate step towards fully separating SHA384 and SHA512.
check_config is the only module which enforces that SHA512 is
enabled together with SHA384.
Signed-off-by: Mateusz Starzyk <mateusz.starzyk@mobica.com>
MinGW and older windows compilers cannot cope with %zu or %lld (there is
a workaround for MinGW, but it involves linking more code, there is no
workaround for Windows compilers prior to 2013). Attempt to work around
this by defining printf specifiers for size_t per platform for the
compilers that cannot use the C99 specifiers.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
Fixes for printf format specifiers, where they have been flagged as
invalid sizes by coverity, and new build flags to enable catching these
errors when building using CMake. Note that this patch uses %zu, which
requires C99 or later.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
Simple find and replace using `#include (<|")mbedtls/(.*)_internal.h(>|")`
and `#include $1$2_internal.h$3`.
Also re-generated visualc files by running
`scripts/generate_visualc_files.pl`.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
`finish_sha384_t` was made more generic by using `unsigned char*`
instead of `unsigned char[48]` as the second parameter.
This change tries to make the function casting more robust against
future improvements of gcc analysis.
Signed-off-by: Rodrigo Dias Correa <rodrigo@correas.us>
This commit fixes the same warning fixed by baeedbf9, but without
wasting RAM. By casting `mbedtls_sha512_finish_ret()`, `padbuf`
could be kept 48 bytes long without triggering any warnings.
Signed-off-by: Rodrigo Dias Correa <rodrigo@correas.us>
GCC 11 generated a warning because `padbuf` was too small to be
used as an argument for `mbedtls_sha512_finish_ret`. The `output`
parameter of `mbedtls_sha512_finish_ret` has the type
`unsigned char[64]`, but `padbuf` was only 48 bytes long.
Even though `ssl_calc_finished_tls_sha384` uses only 48 bytes for
the hash output, the size of `padbuf` was increased to 64 bytes.
Signed-off-by: Rodrigo Dias Correa <rodrigo@correas.us>
In GCC 11, parameters declared as arrays in function prototypes
cannot be declared as pointers in the function definition. The
same is true for the other way around.
The definition of `mbedtls_aes_cmac_prf_128` was changed to match
its public prototype in `cmac.h`. The type `output` was
`unsigned char *`, now is `unsigned char [16]`.
In `ssl_tls.c`, all the `ssl_calc_verify_*` variants now use pointers
for the output `hash` parameter. The array parameters were removed
because those functions must be compatible with the function pointer
`calc_verify` (defined in `ssl_internal.h`).
Signed-off-by: Rodrigo Dias Correa <rodrigo@correas.us>
Move all the PSA crypto APIs using key handles
to use key identifiers but psa_key_open() and
psa_key_close(). This is done without modifying
any test as key handles and key identifiers are
now the same.
Update the library modules using PSA crypto APIs
to get rid of key handles.
Programs and unit tests are updated to not use
key handles in subsequent commits, not in this
one.
Signed-off-by: Ronald Cron <ronald.cron@arm.com>
Use the export keys functionality, to call the public API
`mbedtls_ssl_tls_prf()`, and remove the function
`mbedtls_ssl_get_dtls_srtp_key_material()`.
Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
1. Check allocation success.
2. Check parameter correctness in the use_srtp extension
in server and client.
Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
Improve readability of the code:
1. move common code to `ssl_internal.h` as `static inline`.
2. Add comments.
3. Use local variables for extension size.
4. Change function signature, by adding buffer size and output length.
5. Take server srtp profile out of the loop.
Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
1. Add DTLS-SRTP tests in `ssl-opts.sh`
2. Add logs for the tests to filter.
3. Add function to get the profile informations.
Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
Set authmode to `MBEDTLS_SSL_VERIFY_REQUIRED` when using dtls-srtp,
in case authmode was not set. This is to support self signed certificates
received by the server, which is the case with webRTC. Certificate fingerprints
are verified outside the dtls stack, as defined in RFC 5763.
Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
Enforce CertificateRequest, client and server Certificates, and
CertificateVerify messages, which are mandatory in DTLS-SRTP,
as defined in RFC 5764 section 4.1
Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
Make the key material length in mbedtls_ssl_get_dtls_srtp_key_material
to be in\out, like it is done all over the library
Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
1. Add check for prerequisites in check_config.h
2. Add mki value to use_srtp extension
3. address some review comments
Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
Mbed TLS requires users of DTLS to configure timer callbacks
needed to implement the wait-and-retransmit logic of DTLS.
Previously, the presence of these timer callbacks was checked
at every invocation of `mbedtls_ssl_fetch_input()`, so lowest
layer of the messaging stack interfacing with the underlying
transport.
This commit removes this recurring check and instead checks the
presence of timers once at the beginning of the handshake.
The main rationale for this change is that it is a step towards
separating the various layers of the messaging stack more cleanly:
datagram layer, record layer, message layer, retransmission layer.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
As a result, the copyright of contributors other than Arm is now
acknowledged, and the years of publishing are no longer tracked in the
source files.
Also remove the now-redundant lines declaring that the files are part of
MbedTLS.
This commit was generated using the following script:
# ========================
#!/bin/sh
# Find files
find '(' -path './.git' -o -path './3rdparty' ')' -prune -o -type f -print | xargs sed -bi '
# Replace copyright attribution line
s/Copyright.*Arm.*/Copyright The Mbed TLS Contributors/I
# Remove redundant declaration and the preceding line
$!N
/This file is part of Mbed TLS/Id
P
D
'
# ========================
Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
In library source files, include "common.h", which takes care of
including "mbedtls/config.h" (or the alternative MBEDTLS_CONFIG_FILE)
and other things that are used throughout the library.
FROM=$'#if !defined(MBEDTLS_CONFIG_FILE)\n#include "mbedtls/config.h"\n#else\n#include MBEDTLS_CONFIG_FILE\n#endif' perl -i -0777 -pe 's~\Q$ENV{FROM}~#include "common.h"~' library/*.c 3rdparty/*/library/*.c scripts/data_files/error.fmt scripts/data_files/version_features.fmt
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
These fields might be shifted accordingly in `ssl_parse_record_header()`
when receiving a connection with CID, so they require a manual update
after calling the generic `mbedtls_ssl_reset_in_out_pointers()`.
This commit also adds a regression test which is run by all.sh.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
This commit introduces two changes:
- Add in_msg and out_msg calculations for buffer upsizing. This was previously
considered as unnecessary, but renegotiation using certain ciphersuites needs
this.
- Improving the way out_msg and in_msg pointers are calculated, so that even
if no resizing is introduced, the pointers remain the same;
New tests added:
- various renegotiation schemes with a range of MFL's and ciphersuites;
- an ssl-opt.sh test exercising two things that were problematic: renegotiation
with TLS-ECDHE-ECDSA-WITH-AES-128-CCM-8 and a server MFL that's smaller
than the one negotiated by the client.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
Since the server might want to have a different maximum fragment length
for the outgoing messages than the negotiated one - introduce a new way of
computing it. This commit also adds additional ssl-opt.sh tests ensuring
that the maximum fragment lengths are set as expected.
mbedtls_ssl_get_max_frag_len() is now a deprecated function,
being an alias to mbedtls_ssl_get_output_max_frag_len(). The behaviour
of this function is the same as before.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
Merge the latest state of the target branch (mbedtls/development) into the
pull request to merge mbed-crypto into mbedtls.
Conflicts:
* ChangeLog: add/add conflict. Resolve by using the usual section order.
Rename identifiers containing double-underscore (`__`) to avoid `__`.
The reason to avoid double-underscore is that all identifiers
containing double-underscore are reserved in C++. Rename all such
identifiers that appear in any public header, including ssl_internal.h
which is in principle private but in practice is installed with the
public headers.
This commit makes check-names.sh pass.
```
perl -i -pe 's/\bMBEDTLS_SSL__ECP_RESTARTABLE\b/MBEDTLS_SSL_ECP_RESTARTABLE_ENABLED/g; s/\bMBEDTLS_KEY_EXCHANGE_(_\w+)_(_\w+)\b/MBEDTLS_KEY_EXCHANGE${1}${2}/g' include/mbedtls/*.h library/*.c programs/*/*.c scripts/data_files/rename-1.3-2.0.txt tests/suites/*.function
```
Add a conditional buffer resizing feature. Introduce tests exercising
it in various setups (serialization, renegotiation, mfl manipulations).
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
This commit is the final step in separating the functionality of
what was originally ssl_tls.c into both ssl_tls.c and ssl_msg.c.
So far, ssl_msg.c has been created as an identical copy of ssl_tls.c.
For each block of code in these files, this commit removes it from
precisely one of the two files, depending on where the respective
functionality belongs.
The splitting separates the following functionalities:
1) An implementation of the TLS and DTLS messaging layer, that is,
the record layer as well as the DTLS retransmission state machine.
This is now contained in ssl_msg.c
2) Handshake parsing and writing functions shared between client and
server (functions specific to either client or server are implemented
in ssl_cli.c and ssl_srv.c, respectively).
This is remains in ssl_tls.c.
This commit is the first in a series of commits aiming to split
the content of ssl_tls.c in two files ssl_tls.c and ssl_msg.c.
As a first step, this commit replaces ssl_tls.c by two identical
copies ssl_tls_old.c and ssl_msg.c. Even though the file
ssl_tls_old.c will subsequently be renamed back into ssl_tls.c,
this approach retains the git history in both files.
ssl_decompress_buf() was operating on data from the ssl context, but called at
a point where this data is actually in the rec structure. Call it later so
that the data is back to the ssl structure.
The library style is to start with the includes corresponding to the
current module and then the rest in alphabetical order. Some modules
have several header files (eg. ssl_internal.h).
The recently added error.h includes did not respect this convention and
this commit restores it. In some cases this is not possible just by
moving the error.h declarations. This commit fixes the pre-existing
order in these instances too.
* origin/pr/2854:
Shorter version of mbedtls_ssl_send_fatal_handshake_failure
Resolve#2801 - remove repetitive assignment to ssl->in_msg (the first value was never used)
Resolve#2800 - move declaration to avoid unused variable warning in case MBEDTLS_SSL_PROTO_DTLS was undefined
Resolve#2717 - remove erroneous sizeof (the operator was applied to constant integer number)
Record checking fails if mbedtls_ssl_check_record() is called with
external buffer. Received record sequence number is available in the
incoming record but it is not available in the ssl contexts `in_ctr`-
variable that is used when decoding the sequence number.
To fix the problem, temporarily update ssl context `in_ctr` to
point to the received record header and restore value later.
In TLS, the master secret is always a key. But EAP-TLS uses the TLS
PRF to derive an IV with an empty string for the "secret" input. The
code always stored the secret into a key slot before calling the TLS
PRF, but this doesn't work when the secret is empty, since PSA Crypto
no longer supports empty keys. Add a special case for an empty secret.
The SSL context maintains a set of 'out pointers' indicating the
address at which to write the header fields of the next outgoing
record. Some of these addresses have a static offset from the
beginning of the record header, while other offsets can vary
depending on the active record encryption mechanism: For example,
if an explicit IV is in use, there's an offset between the end
of the record header and the beginning of the encrypted data to
allow the explicit IV to be placed in between; also, if the DTLS
Connection ID (CID) feature is in use, the CID is part of the
record header, shifting all subsequent information (length, IV, data)
to the back.
When setting up an SSL context, the out pointers are initialized
according to the identity transform + no CID, and it is important
to keep them up to date whenever the record encryption mechanism
changes, which is done by the helper function ssl_update_out_pointers().
During context deserialization, updating the out pointers according
to the deserialized record transform went missing, leaving the out
pointers the initial state. When attemping to encrypt a record in
this state, this lead to failure if either a CID or an explicit IV
was in use. This wasn't caught in the tests by the bad luck that
they didn't use CID, _and_ used the default ciphersuite based on
ChaChaPoly, which doesn't have an explicit IV. Changing either of
this would have made the existing tests fail.
This commit fixes the bug by adding a call to ssl_update_out_pointers()
to ssl_context_load() implementing context deserialization.
Extending test coverage is left for a separate commit.
Breaking into a series of statements makes things easier when stepping through
the code in a debugger.
Previous comments we stating the opposite or what the code tested for (what we
want vs what we're erroring out on) which was confusing.
Also expand a bit on the reasons for these restrictions.
Modelled after the config-checking header from session s11n.
The list of relevant config flags was established by manually checking the
fields serialized in the format, and which config.h flags they depend on.
This probably deserves double-checking by reviewers.
Since the type of cid_len is unsigned but shorter than int, it gets
"promoted" to int (which is also the type of the result), unless we make the
other operand an unsigned int which then forces the expression to unsigned int
as well.
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.
This mainly follows the design document (saving all fields marked "saved" in
the main structure and the transform sub-structure) with two exceptions:
- things related to renegotiation are excluded here (there weren't quite in
the design document as the possibility of allowing renegotiation was still
on the table, which is no longer is) - also, ssl.secure_renegotiation (which
is not guarded by MBEDTLS_SSL_RENEGOTIATION because it's used in initial
handshakes even with renegotiation disabled) is still excluded, as we don't
need it after the handshake.
- things related to Connection ID are added, as they weren't present at the
time the design document was written.
The exact format of the header (value of the bitflag indicating compile-time
options, whether and how to merge it with the serialized session header) will
be determined 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 a new SSL error code
`MBEDTLS_ERR_SSL_VERSION_MISMATCH`
which can be used to indicate operation failure due to a
mismatch of version or configuration.
It is put to use in the implementation of `mbedtls_ssl_session_load()`
to signal the attempt to de-serialize a session which has been serialized
in a build of Mbed TLS using a different version or configuration.
This commit makes use of the added space in the session header to
encode the state of those parts of the compile-time configuration
which influence the structure of the serialized session in the
present version of Mbed TLS. Specifically, these are
- the options which influence the presence/omission of fields
from mbedtls_ssl_session (which is currently shallow-copied
into the serialized session)
- the setting of MBEDTLS_X509_CRT_PARSE_C, which determines whether
the serialized session contains a CRT-length + CRT-value pair after
the shallow-copied mbedtls_ssl_session instance.
- the setting of MBEDTLS_SSL_SESSION_TICKETS, which determines whether
the serialized session contains a session ticket.
This commit adds space for two bytes in the header of serizlied
SSL sessions which can be used to determine the structure of the
remaining serialized session in the respective version of Mbed TLS.
Specifically, if parts of the session depend on whether specific
compile-time options are set or not, the setting of these options
can be encoded in the added space.
This commit doesn't yet make use of the fields.
The format of serialized SSL sessions depends on the version and the
configuration of Mbed TLS; attempts to restore sessions established
in different versions and/or configurations lead to undefined behaviour.
This commit adds an 3-byte version header to the serialized session
generated and cleanly fails ticket parsing in case a session from a
non-matching version of Mbed TLS is presented.
This bug was present since cert digest had been introduced, which highlights
the need for testing.
While at it, fix a bug in the comment explaining the format - this was
introduced by me copy-pasting to hastily from current baremetal, that has a
different format (see next PR in the series for the same in development).
We have explicit recommendations to use US spelling for technical writing, so
let's apply this to code as well for uniformity. (My fingers tend to prefer UK
spelling, so this needs to be fixed in many places.)
sed -i 's/\([Ss]eriali\)s/\1z/g' **/*.[ch] **/*.function **/*.data ChangeLog
This uncovered a bug that led to a double-free (in practice, in general could
be free() on any invalid value): initially the session structure is loaded
with `memcpy()` which copies the previous values of pointers peer_cert and
ticket to heap-allocated buffers (or any other value if the input is
attacker-controlled). Now if we exit before we got a chance to replace those
invalid values with valid ones (for example because the input buffer is too
small, or because the second malloc() failed), then the next call to
session_free() is going to call free() on invalid pointers.
This bug is fixed in this commit by always setting the pointers to NULL right
after they've been read from the serialised state, so that the invalid values
can never be used.
(An alternative would be to NULL-ify them when writing, which was rejected
mostly because we need to do it when reading anyway (as the consequences of
free(invalid) are too severe to take any risk), so doing it when writing as
well is redundant and a waste of code size.)
Also, while thinking about what happens in case of errors, it became apparent
to me that it was bad practice to leave the session structure in an
half-initialised state and rely on the caller to call session_free(), so this
commit also ensures we always clear the structure when loading failed.
This allows callers to discover what an appropriate size is. Otherwise they'd
have to either try repeatedly, or allocate an overly large buffer (or some
combination of those).
Adapt documentation an example usage in ssl_client2.
Avoid useless copy with mbedtls_ssl_get_session() before serialising.
Used in ssl_client2 for testing and demonstrating usage, but unfortunately
that means mbedtls_ssl_get_session() is no longer tested, which will be fixed
in the next commit.
On client side, this is required for the main use case where of serialising a
session for later resumption, in case tickets are used.
On server side, this doesn't change much as ticket_len will always be 0.
This unblocks testing the functions by using them in ssl_client2, which will
be done in the next commit.
This finishes making these functions public. Next step is to get them tested,
but there's currently a blocker for that, see next commit (and the commit
after it for tests).
While 'session hash' is currently unique, so suitable to prove that the
intended code path has been taken, it's a generic enough phrase that in the
future we might add other debug messages containing it in completely unrelated
code paths. In order to future-proof the accuracy of the test, let's use a
more specific string.
The previous comment used "TLS" as a shortcut for "TLS 1.0/1.1" which was
confusing. This partially reflected the names of the calc_verify/finished that
go ssl, tls (for 1.0/1.1) tls_shaxxx (for 1.2), but still it's clearer to be
explicit in the comment - and perhaps in the long term the function names
could be clarified instead.
When using this function to deserialize, it's not a problem to have a session
structure as input as we'll have one around anyway (most probably freshly
deserialised).
However for tests it's convenient to be able to build a transform without
having a session structure around.
Also, removing this structure from parameters makes the function signature
more uniform, the only exception left being the ssl param at the end that's
hard to avoid for now.
Configs with no DEBUG_C are used for example in test-ref-configs.pl, which also
runs parts of compat.sh or ssl-opt.sh on them, so the added 'ssl = NULL'
statements will be exercised in those tests at least.
Make it more explicit what's used. Unfortunately, we still need ssl as a
parameter for debugging, and because calc_verify wants it as a parameter (for
all TLS versions except SSL3 it would actually only need handshake, but SSL3
also accesses session_negotiate).
It's also because of calc_verify that we can't make it const yet, but see next
commit.
* origin/pr/2790: (40 commits)
Fix possibly-lossy conversion warning from MSVC
Reintroduce length 0 check for records
Don't use memcpy() for 2-byte copy operation
Remove integer parsing macro
Fix alignment in record header parsing routine
Don't disallow 'record from another epoch' log msg in proxy ref test
Make sure 'record from another epoch' is displayed for next epoch
Implement record checking API
Mark ssl_parse_record_header() as `const` in SSL context
Make mbedtls_ssl_in_hdr_len() CID-unaware
Remove duplicate setting of ssl->in_msgtype and ssl->in_msglen
Move update of in_xxx fields in ssl_get_next_record()
Move update of in_xxx fields outside of ssl_prepare_record_content()
Reduce dependency of ssl_prepare_record_content() on in_xxx fields
Move ssl_update_in_pointers() to after record hdr parsing
Mark DTLS replay check as `const` on the SSL context
Move updating the internal rec ptrs to outside of rec hdr parsing
Mark ssl_decrypt_buf() as `const in the input SSL context
Adapt ssl_prepare_record_content() to use SSL record structure
Use record length from record structure when fetching content in TLS
...
* origin/pr/2781:
Documentation fixes according to review
Remove unused label in ssl_client2/ssl_server2
Add missing word in documentation of mbedtls_ssl_check_record()
cli/srv ex: Add dbg msg if record checking gives inconsistent result
Fix minor issues in documentation of mbedtls_ssl_check_record()
State that record checking is DTLS only and doesn't check content type
Update version_features.c
Pass dgrams to mbedtls_ssl_check_record in ssl_client2/server2
Add IO wrappers to ssl_server2 as interm's between NET and SSL layer
Add IO wrappers to ssl_client2 as interm's between NET and SSL layer
Introduce configuration option and API for SSL record checking
