This makes a mbedtls_pk_context memory-wise equivalent to a
mbedtls_uecc_keypair and removes a dynamic allocation, making the PK layer
zero-cost in terms of memory when PK_SINGLE_TYPE is enabled.
In very reduced configurations, we don't want the overhead of maintaining a
bool just to remember if the context is valid and checking that bit at every
point of entry.
Note: so far this validity bit also served as a proxy to ensure that pk_ctx
was valid (currently this is a pointer to a dynamically-allocated buffer). In
the next series of commits, this will be changed to a statically-allocated
buffer, so there will be no question about its validity.
In the end (after this commit and the next series), a pk_context_t will be
(memory-wise) just the same as a mbedtls_uecc_keypair when SINGLE_TYPE is
enabled - meaning the PK layer will have zero memory overhead in that case.
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.
For optional functions, we introduce an extra macro to tell if the function is
omitted. As the C preprocessor doesn't directly support comparing strings,
testing if the _FUNC macro is defined to NULL isn't obvious. One could
probably play tricks to avoid the need for _OMIT macros, but the small amount
of (entirely local) duplication here is probably a lesser evil than extra
preprocessor complexity.
We want public functions to resolve to the internal wrappers at compile-time.
For this we need the wrappers to be visible from where the public functions
are defined. A simple declaration is not enough if we want the compiler to be
able to inline the wrapper and eliminate function overhead.
This commit just copies verbatim the contents of pk_wrap.c into pk.c. The next
commit will clean up the result (redundant includes etc.).
This achieves two related goals:
1. Those members are now only accessed via the accessor function (except in
code paths that we don't care about: those guarded by
MBEDTLS_PK_RSA_ALT_SUPPORT or MBEDTLS_ECP_RESTARTABLE)
2. When we turn on compile-time dispatch, we don't obviously don't want to
keep a runtime NULL check.
For debug this requires changing the signature or the accessor function to
return int; this is done without changing the signature of the accessed
function.
1. Mark an RSA-alt-specific code path as such.
2. Move NULL check for wrapper function closer to the use of that function.
Those are in preparation of the next commit.
This is the first commit in a series aiming at implementing optional
compile-time dispatch when a single PK type is hardcoded. At the end of this
series, the functions introduced here will directly resolve to the correct
function at compile-time when this (to be created) option is enabled.
* baremetal: (78 commits)
Review corrections 6
Review corrections 5
Minor changes to tinycrypt README
Typos in the tinycrypt README
Addition of copyright statements to tinycrypt files
Add LICENSE and README for tinycrypt
Add SPDX lines to each imported TinyCrypt file
Review corrections 4
Review corrections 3
Review corrections 2
Review corrections
Update signature of BE conversion functions
Use function for 16/24/32-bit BE conversion
x509.c: Minor readability improvement
x509_crt.c: Indicate guarding condition in #else branch
X.509: Don't remove verify callback by default
Fix Doxygen warnings regarding removed verify cb+ctx parameters
ECC restart: Use optional verification mode in bad signature test
Re-implement verify chain if vrfy cbs are disabled
Add zero-cost abstraction layer for CRT verification chain
...
On the mbedtls-2.16 side, there was a change in commit
a7cfdad82e (PR r#503) in order to write
fixed-length private keys. It added a new helper function
pk_write_ec_private() for that.
On the baremetal side, there were changes in order to add a tinycrypt-based
implementation. It added a new helper function pk_write_ec_privkey() with two
implementations (with or without tinycrypt).
This commit keeps the function pk_write_ec_privkey() but changes its
implementation in the non-tinycrypt configuration in order to match the
implementation of pk_write_ec_private(), which is in turn removed it was only
used in that place.
The tinycrypt version of pk_write_ec_private() was already writing
constant-length private keys, so there is nothing to change here.
* mbedtls-2.16: (28 commits)
Bump version to Mbed TLS 2.16.3
Changelog entry
Check for zero length and NULL buffer pointer
ssl-opt.sh: wait for proxy to start before running the script further
Fix uninitialized variable in x509_crt
HMAC DRBG: Split entropy-gathering requests to reduce request sizes
Fix the license header of hkdf
Add a change log entry
Add a test for mlaformed ECJPAKE context
Fix handling of md failure
Add a test for signing content with a long ECDSA key
Add documentation notes about the required size of the signature buffers
Add missing MBEDTLS_ECP_C dependencies in check_config.h
Change size of preallocated buffer for pk_sign() calls
Adapt ChangeLog
Fix mpi_bigendian_to_host() on bigendian systems
Add ChangeLog entry for new function
Add ChangeLog entry
Correct deterministic ECDSA behavior
Add warning for alternative ECDSA implementations
...
- Try to follow english grammar in function documentation
- Fix too long line
- Remove additional brackets
- Follow mbedtls coding style in for-statement
-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
This commit re-implements the previously introduced internal
verification chain API in the case where verification callbacks
are disabled. In this situation, it is not necessary to maintain
the list of individual certificates and flags comprising the
verification chain - instead, it suffices to just keep track
of the length and the total (=merged) flags.
When verifying an X.509 certificate, the current verification logic
maintains an instance of the internal mbedtls_x509_crt_verify_chain
structure representing the state of the verification process. This
instance references the list of certificates that comprise the chain
built so far together with their verification flags. This information
must be stored during verification because it's being passed to the
verification callback at the end of verification - if the user has
specified those.
If the user hasn't specified a verification callback, it is not
necessary to maintain the list of CRTs, and it is also not necessary
to maintain verification flags for each CRT individually, as they're
merged at the end of the verification process.
To allow a readable simplification of the code in case no verification
callbacks are used, this commit introduces a zero-cost abstraction layer
for the functionality that's required from the verification chain structure:
- init/reset
- add a new CRT to the chain
- get pointer to current CRT flags
- add flags to EE certificate
- get current chain length
- trigger callbacks and get final (merged) flags
This gives flexibility for re-implementing the verification chain
structure, e.g. in the case where no verification callbacks are
provided, and there's hence no need to store CRTs and flags
individually. This will be done in a later commit.
When MBEDTLS_MD_SINGLE_HASH is set, both the underlying digest context
and the HMAC data are embedded into the mbedtls_md_context; otherwise,
they're dynamically allocated and referenced from mbedtls_md_context.
When the HMAC data is embedded in mbedtls_md_context, it's unnecessary
to check whether mbedtls_md_context::hmac_ctx is NULL, because that's
never the case in defined behaviour, but the check has kept for
uniformity so far. However, contrary to the expectation that compilers
would silently remove this check as always false, ARMC6 complains about
it, breaking some tests in all.sh.
This commit fixes this by guarding checks for
mbedtls_md_context::hmac_ctx == NULL
by !MBEDTLS_MD_SINGLE_HASH.
Recall that in the default configuration, Mbed TLS provides access
digest implementations through two layers of indirection:
1) Call of MD API (e.g. mbedtls_md_update())
2) Call of function pointer from MD info structure
3) Actual digest implementation (e.g. mbedtls_sha256_update()).
Ideally, if only a single digest is enabled - say SHA-256 - then calling
mbedtls_md_update() should _directly_ jump to mbedtls_sha256_update(),
with both layers of indirection removed. So far, however, setting
MBEDTLS_MD_SINGLE_HASH will only remove the second - function pointer -
layer of indirection, while keeping the non-inlined stub implementations
of e.g. mbedtls_md_update() around.
This commit is a step towards allowing to define implementations of
the MD API as `static inline` in case we know that they are so small
that they should be defined in md.h and not in md.c.
In a nutshell, the approach is as follows: For an MD API function
mbedtls_md_xxx() that should be inlin-able, introduce its implementation
as a `static inline` wrapper `mbedtls_md_xxx_internal()` in md.h,
and then define mbedtls_md_xxx() either in md.h or in md.c, by just
calling mbedtls_md_xxx_internal().
Moving the implementations of those MD API functions that should be
inlinable to md.h requires the presence of both the MD info struct
and all specific digest wrapper functions in md.h, and this is what
this commit ensures, by moving them from md.c into a new internal
header file md_internal.h. Implementing the aforementioned wrappers for
those MD API that should be inlinable is left for subsequent commits.
ARMC5 appears to use the heuristic that as soon as a function's address
is taken, the function can no longer be removed from the resulting object
file (which is not necessarily true if all uses of the functions address
can be inlined).
Circumvent this lack of optimization by not returning function pointers.
This commit introduces the configuration option
MBEDTLS_MD_SINGLE_HASH
which can be used to hardcode support for a single digest algorithm
at compile-time, at the benefit of reduced code-size.
To use, it needs to be defined to evaluate to a macro of the form
MBEDTLS_MD_INFO_{DIGEST}, and macros MBEDTLS_MD_INFO_{DIGEST}_FIELD
must be defined, giving rise to the various aspects (name, type,
size, ...) of the chosen digest algorithm. MBEDTLS_MD_INFO_SHA256
provides an example, but other algorithms can be added if needed.
At the moment, the effect of using MBEDTLS_MD_SINGLE_HASH is that
the implementation of the MD API (e.g. mbedtls_md_update()) need no
longer to through the abstraction of the mbedtls_md_info structures
by calling their corresponding function pointers fields (akin to
virtual functions in C++), but the directly call the corresponding
core digest function (such as mbedtls_sha256_update()).
Therefore, MBEDTLS_MD_SINGLE_HASH so far removes the second layer
of indirection in the chain
User calls MD API -> MD API calls underlying digest impl'n
-> Core digest impl'n does the actual work,
but the first indirection remains, as the MD API remains untouched
and cannot yet be inlined. Studying to what extend inlining the
shortened MD API implementations would lead to further code-savings
is left for a later commit.
In builds enabling only a single MD digest, we want to be able to
implement the MD info getter functions by returning compile-time
constants matching the fields of the MD info structures used so far.
To avoid information duplication hardening maintainability, this
commit introduces the possibility of providing the various aspects
of a particular digest implementation by defining macros
MBEDTLS_MD_INFO_DIGEST_FIELD (e.g. MBEDTLS_MD_INFO_SHA256_SIZE)
and to generate the corresponding mbedtls_md_info instance from
this set of macros, via the new macro MBEDTLS_MD_INFO().
This way, we'll be able to switch between MD info based builds
and single-digest builds without information duplication.
This commit continues the introduction of the MD digest implementation
abstraction layer given by `mbedtls_md_handle_t` by adding getter
functions returning the various properties of an implementation
(e.g. name, digest type, digest size). For the existing implementation,
these are just structure field accesses; however, in configurations
hardcoding the choice of a fixed digest algorithm, we'll be able to
implement them as inline functions returning compile-time constants.
As has been previously done for ciphersuites, this commit introduces
a zero-cost abstraction layer around the type
mbedtls_md_info const *
whose valid values represent implementations of message digest algorithms.
Access to a particular digest implementation can be requested by name or
digest ID through the API mbedtls_md_info_from_xxx(), which either returns
a valid implementation or NULL, representing failure.
This commit replaces such uses of `mbedtls_md_info const *` by an abstract
type `mbedtls_md_handle_t` whose valid values represent digest implementations,
and which has a designated invalid value MBEDTLS_MD_INVALID_HANDLE.
The purpose of this abstraction layer is to pave the way for builds which
support precisely one digest algorithm. In this case, mbedtls_md_handle_t
can be implemented as a two-valued type, with one value representing the
invalid handle, and the unique valid value representing the unique enabled
digest.
Cookies are fully opaque so we can change the hash used at any time, it's not
part of the API.
The cookie module handles truncation, so it's simpler to always use SHA-256
rather than check if SHA-224 is available.
Moved some functions under defined to get rid of compiler warnings.
Functions moved under defines:
- mbedtls_x509_get_alg
- mbedtls_x509_get_alg_null
- mbedtls_x509_get_time
- mbedtls_x509_get_ext
- mbedtls_x509_sig_alg_gets
- mbedtls_x509_key_size_helper
Left one function (mbedtls_x509_write_names) as non static as it increased code size.
* origin/mbedtls-2.16:
Changelog entry
Check for zero length and NULL buffer pointer
ssl-opt.sh: wait for proxy to start before running the script further
Adapt ChangeLog
Fix mpi_bigendian_to_host() on bigendian systems
No need to play tricks with macros and functions depending on whether
SHA256_SMALLER is enabled or not, with a static inline function all common
compilers (tested with arm-gcc, armcc5, arm-clang) will Do The Right Thing
depending on whether we told them to optimize for size or speed.
The TinyCrypt PK signature wrapper uses ASN.1 writing functions
for length and tag, accounting for the only dependency of the
baremetal build on ASN.1 writing.
Since all lengths to be encoded are below 128 Bytes and are hence
ASN.1 encoded as single Bytes, the dependency on ASN.1 writing can
be removed at low complexity by writing the length and tags directly.
Extend scope of TC in ECDH-param extraction from CRT
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 ClientKeyExchange message.
Extend scope of TC in ECDH-param extraction from CRT
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 ServerKeyExchange 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 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.
Extend scope of TC in ECDH-param extraction from CRT
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 assembly of the PMS.
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.
PEM-encoded keys with PEM header
-----BEGIN EC PRIVATE KEY-----
...
-----END EC PRIVATE KEY-----
were previously not parsed in configurations using TinyCrypt
instead of legacy ECC crypto.
The PK type MBEDTLS_PK_ECDSA is never returned from
`mbedtls_pk_info_from_type()`. Instead, EC keys either
are identified as MBEDTLS_PK_ECKEY_DH (in case they
must only be used for ECDHE) or MBEDTLS_PK_ECKEY (in
case they can be used for any algorithm).
With TinyCrypt and legacy ECC mutually exclusive, we don't have
to use #if TINYCRYPT #else #if LEGACY #endif #endif anymore, but
can add the TC and legacy based ECC implementations independently.
- TinyCrypt uses `0` for errors.
- The first argument to uECC_verify() should be the public key,
but the previous code passed the beginning of the entire
private-public key structure.
The PK-type MBEDTLS_PK_ECDSA isn't really used by the library.
Especially, when parsing a generic EC key, a PK context of type
MBEDTLS_PK_ECKEY will be requested. Hence, to drop in TinyCrypt
for the legacy-ECC implementation, the PK type that TinyCrypt
implements must be MBEDTLS_PK_ECKEY.
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.
This patch fixes an issue we encountered with more stringent compiler
warnings. The signature_is_good variable has a possibility of being
used uninitialized. This patch moves the use of the variable to a
place where it cannot be used while uninitialized.
Signed-off-by: Andy Gross <andy.gross@linaro.org>
According to SP800-90A, the DRBG seeding process should use a nonce
of length `security_strength / 2` bits as part of the DRBG seed. It
further notes that this nonce may be drawn from the same source of
entropy that is used for the first `security_strength` bits of the
DRBG seed. The present HMAC DRBG implementation does that, requesting
`security_strength * 3 / 2` bits of entropy from the configured entropy
source in total to form the initial part of the DRBG seed.
However, some entropy sources may have thresholds in terms of how much
entropy they can provide in a single call to their entropy gathering
function which may be exceeded by the present HMAC DRBG implementation
even if the threshold is not smaller than `security_strength` bits.
Specifically, this is the case for our own entropy module implementation
which only allows requesting at most 32 Bytes of entropy at a time
in configurations disabling SHA-512, and this leads to runtime failure
of HMAC DRBG when used with Mbed Crypto' own entropy callbacks in such
configurations.
This commit fixes this by splitting the seed entropy acquisition into
two calls, one requesting `security_strength` bits first, and another
one requesting `security_strength / 2` bits for the nonce.
Fixes#237.
* mbedtls-2.16: (21 commits)
Exclude DTLS 1.2 only with older OpenSSL
Document the rationale for the armel build
Switch armel build to -Os
Add a build on ARMv5TE in ARM mode
Add changelog entry for ARM assembly fix
bn_mul.h: require at least ARMv6 to enable the ARM DSP code
Changelog entry for test certificates update
Change worktree_rev to HEAD for rev-parse
Add ChangeLog entry for entropy_nv_seed test case fix
entropy_nv_seed: cope with SHA-256
entropy_nv_seed: clean up properly
Add ChangeLog entry for undefined behavior fix in test_suite_nist_kw
Don't call memset after calloc
Adapt ChangeLog
ECP restart: Don't calculate address of sub ctx if ctx is NULL
Update certificates to expire in 2029
Update soon to be expired crl
Test that a shared library build produces a dynamically linked executable
Test that the shared library build with CMake works
Add a test of MBEDTLS_CONFIG_FILE
...
The NO_INLINE annotation of tls_prf_sha256() and tls_prf_sha384() from
the last commit surprisingly had an influence on ARMC5 compilation in
that tls_prf_generic() was no longer automatically inlined into
tls_prf_sha256() if only the latter was enabled (and is the point
where tls_prf_generic() is called). This commit forces inlining
of tls_prf_generic() in this case.
Usually, compilers are clever enough to pick the best inlining
strategy, but in this instance, it appears that compiling on ARMC6,
the compilers inlines xxx_prf_yyy() and xxx_calc_finished_yyy()
even though it really shouldn't. Forbid inlining through the use
of __attribute__((noinline)).
Somehow, at least ARMC5 isn't able to recognize this automatically.
Since some of the arguments to ssl_populate_transform() are compile-
time constants in reduced configurations, inlining leads to slightly
shorter code.
This saves a few bytes in configurations where only one hash
is enabled, and configurations allowing multiple hashes probably
don't care about code-size anyway.
This function is called on client-only once the ciphersuite has
been chosen and it it is known which digest the client will need
for the handshake transcript throughout the handshake, and causes
all other unneeded handshake transcripts to be discontinued.
(On the server, we cannot call this function because we don't know
which hash the client will those in its CertificateVerify message).
However, the benefit of this call is marginal, since transcript hash
computation is negligible compared to asymmetric crypto, and moreover
the handshake transcript contexts for the unused digests are still
stored in the SSL handshake parameter structure and not freed until
the end of the handshake.
Finally, if we're running on a _really_ constrained client, there
will be only one hash function enabled anyway, and in this case
the checksum optimization has no effect.
This commit therefore removes checksum optimization altogether,
saving some code on constrained systems.
- a comment regarding the implementation of hmac_drbg_reseed_core()
was misplaced.
- add more references to the standard, and add details on how the
comments in the code refer to various parts of the standard.
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.
According to SP800-90A, the DRBG seeding process should use a nonce
of length `security_strength / 2` bits as part of the DRBG seed. It
further notes that this nonce may be drawn from the same source of
entropy that is used for the first `security_strength` bits of the
DRBG seed. The present HMAC DRBG implementation does that, requesting
`security_strength * 3 / 2` bits of entropy from the configured entropy
source in total to form the initial part of the DRBG seed.
However, some entropy sources may have thresholds in terms of how much
entropy they can provide in a single call to their entropy gathering
function which may be exceeded by the present HMAC DRBG implementation
even if the threshold is not smaller than `security_strength` bits.
Specifically, this is the case for our own entropy module implementation
which only allows requesting at most 32 Bytes of entropy at a time
in configurations disabling SHA-512, and this leads to runtime failure
of HMAC DRBG when used with Mbed TLS' own entropy callbacks in such
configurations.
This commit fixes this by splitting the seed entropy acquisition into
two calls, one requesting `security_strength` bits first, and another
one requesting `security_strength / 2` bits for the nonce.
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).
IAR doesn't like `((void) var);` as a means to indicate an unused
variable if that variable hasn't been initialized before. Make it
happy by initializing the variable before.
ssl_server_key_exchange_parse() is compiled even if there's no ciphersuite
enabled which uses it (for example, that's the case in RSA-only builds).
The rationale for that is to avoid cluttering the code with numerous
compile-time guards. A consequence, however, is the top of
ssl_server_key_exchange_parse() contains declarations for variables
which are never put to use, and rightfully leading to compiler warnings.
This commit silences these warnings by putting `((void) VAR);` statements
in the branch which detects if we ever happen to call the function in an
unexpected ciphersuite.
In the PSK and RSA-PSK ciphersuites, the ServerKeyExchange message
MAY be skipped. This commit moves the code-path peeking at the
incoming message to decide whether it's probably a ServerKeyExchange
to the new coordination function ssl_server_key_exchange_coordinate().
This commit moves the code checking whether a SrvKeyExchange message
is expected or not to the new function ssl_srv_key_exchange_coordinate().
Note that the potential static DH extraction is done prior to the
coordination step.
This code moves the code-path that extracts static DH parameters
from the server's CRT (if applicable) to the new function
ssl_server_key_exchange_prepare().
This commit adds declarations and dummy implementations for
the restructured incoming server key exchange handling that
will replace the previous ssl_parse_server_key_exchange().
The entry point for the SrvKeyExchange handling that is called
from the handshake state machine is
`ssl_process_server_key_exchange()`,
splitting the processing into the following steps:
- Preparation: For a static DH key exchange, extract
DH parameters from the server's CRT.
- Coordination: Check if a SrvKeyExchange message is expected
(e.g., it isn't for a RSA-based key exchange)
- Reading: Fetch and check content and handshake type
of incoming message.
- Parsing: Parse and store the ServerKeyExchange message.
- Postprocessing: Update handstate state machine.
The subsequent commits will scatter the code from the previous
monolithic function ssl_parse_server_key_exchange() among those
dedicated functions, commenting out each part of
ssl_parse_server_key_exchange() that has already been dealt with.
This gradual progression is meant to ease reviewing. Once all
code has been moved and all changes explained,
ssl_parse_server_key_exchange() will be removed.
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().
This commit adds declarations and dummy implementations for
the restructured incoming client key exchange handling that
will replace the previous ssl_parse_client_key_exchange().
The entry point for the CliKeyExchange handling that is called
from the handshake state machine is
`ssl_process_client_key_exchange()`,
splitting the processing into the following steps:
- Fetching: Read next message from the messaging layer
and check that it has the correct type.
The ClientKeyExchange message is never
omitted, so there is no ambiguity in what
to expect, and hence no dedicated preparation
step as for other handshake states.
- Parsing: Parse the ClientKeyExchange message and
use the information in it to derive keying
material such as the shared (EC)DHE secret.
- Postprocessing:
Compute the session keys from the available
keying material. This splits in two steps:
(1) Build the PreMasterSecret (PMS) from the
available keying material, e.g. concatenate
the (EC)DHE secret with a PSK, if used.
(2) Extract the MasterSecret and Session Keys
from the PreMasterSecret.
The subsequent commits will scatter the code from the previous
monolithic function ssl_parse_client_key_exchange() among those
dedicated functions, commenting out each part of
ssl_parse_client_key_exchange() that has already been dealt with.
This gradual progression is meant to ease reviewing. Once all
code has been moved and all changes explained,
ssl_parse_client_key_exchange() will be removed.
The code from the previous function ssl_write_client_key_exchange()
has been entirely moved to one of the newly introduced subroutines
and is no longer needed. This commit removes it.
This commit moves the code responsible for
(a) generating the client's private and public (EC)DHE keys
(b) writing it to the message buffer
to the new writing function ssl_client_key_exchange_write().
As mentioned in the previous commit message, (a) and (b) are
currently inseparable at the (EC)DHE API level, which is why
(a) can't be moved to the preparation step.
For RSA or RSA-PSK exchanges, the PMS contains 46 random bytes
picked by the client. These bytes are generated prior to the
writing of the ClientKeyExchange message.
This commit splits the previous function ssl_write_encrypted_pms() into
PPMS-GEN: ssl_rsa_generate_partial_pms()
PPMS-ENC: ssl_rsa_encrypt_partial_pms().
The prefix 'partial' is meant to emphasize that the generation of the PMS
is not always entirely done by these functions: For RSA-PSK e.g., the
PSK still needs to be added.
The two calls of ssl_write_encrypted_pms() in
ssl_write_client_key_exchange() will split in calls of the functions
PPMS-GEN and PPMS-ENC each, with PPMS-GEN being moved to the new
preparation function ssl_client_key_exchange_prepare() in this commit,
and PPMS-ENC being moved to ssl_client_key_exchange_write() in the
next commit.
After and performing key generation operations,
the client-side outgoing 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 can be done after the ClientKeyExchange
has been written and the respective keying material has been generated,
and this commit moves it to the new postprocessing function
ssl_client_key_exchange_postprocess().
Ideally, the PMS assembly could be done prior to writing the
ClientKeyExchange message, but the (EC)DHE API does currently
not allow splitting secret-generation and secret-export; as
long as that's the case, we to generation and exporting in the
message writing function, forcing PMS assembly to be done in
the postprocessing.
This commit adds declarations and dummy implementations for
the restructured outgoing client key exchange handling that
will replace the previous ssl_write_client_key_exchange().
The entry point for the CliKeyExchange handling that is called
from the handshake state machine is
`ssl_process_client_key_exchange()`,
splitting the processing into the following steps:
- Preparation
Compute the keying material to be sent.
* For (EC)DH: Pick parameters and compute PMS.
* For ECJPAKE: Run round 2
* For RSA: Encrypt PMS
- Writing: Prepare the writing of a new messae.
- Postprocessing: Update handstate state machine.
The subsequent commits will scatter the code from the previous
monolithic function ssl_write_client_key_exchange() among those
dedicated functions, commenting out each part of
ssl_write_client_key_exchange() that has already been dealt with.
This gradual progression is meant to ease reviewing. Once all
code has been moved and all changes explained,
ssl_write_client_key_exchange() will be removed.
This commit implements the record checking API
mbedtls_ssl_check_record()
on top of the restructured incoming record stack.
Specifically, it makes use of the fact that the core processing routines
ssl_parse_record_header()
mbedtls_ssl_decrypt_buf()
now operate on instances of the SSL record structure mbedtls_record
instead of the previous mbedtls_ssl_context::in_xxx fields.
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.
ssl_get_next_record() updates the legacy in_xxx fields in two places,
once before record decryption and once after. Now that record decryption
doesn't use or affect the in_xxx fields anymore, setting up the these
legacy fields can entirely be moved to the end of ssl_get_next_record(),
which is what this comit does.
This commit solely moves existing code, but doesn't yet simplify the
now partially redundant settings of the in_xxx fields. This will be
done in a separate commit.
Multiple record attributes such as content type and payload length
may change during record decryption, and the legacy in_xxx fields
in the SSL context therefore need to be updated after the record
decryption routine ssl_decrypt_buf() has been called.
After the previous commit has made ssl_prepare_record_content()
independent of the in_xxx fields, setting them can be moved
outside of ssl_prepare_record_content(), which is what this
commit does.
Previously, ssl_update_in_pointers() ensured that the in_xxx pointers
in the SSL context are set to their default state so that the record
header parsing function ssl_parse_record_header() could make use of them.
By now, the latter is independent of these pointers, so they don't need
to be setup before calling ssl_parse_record_header() anymore.
However, other parts of the messaging stack might still depend on it
(to be studied), and hence this commit does not yet reomve
ssl_update_in_pointers() entirely.
The stack maintains pointers mbedtls_ssl_context::in_xxx pointing to
various parts of the [D]TLS record header. Originally, these fields
were determined and set in ssl_parse_record_header(). By now,
ssl_parse_record_header() has been modularized to setup an instance
of the internal SSL record structure mbedtls_record, and to derive
the old in_xxx fields from that.
This commit takes a further step towards removing the in_xxx fields
by deriving them from the established record structure _outside_ of
ssl_parse_record_header() after the latter has succeeded.
One exception is the handling of possible client reconnects,
which happens in the case then ssl_parse_record_header() returns
MBEDTLS_ERR_SSL_UNEXPECTED_RECORD; since ssl_check_client_reconnect()
so far uses the in_xxx fields, they need to be derived from the
record structure beforehand.
This commit makes a first step towards modularizing the incoming record
processing by having it operate on instances of the structure mbedtls_record
representing SSL records.
So far, only record encryption/decryption operate in terms of record
instances, but the rest of the parsing doesn't. In particular,
ssl_parse_record_header() operates directly on the fixed input buffer,
setting the various ssl->in_xxx pointers and fields, and only directly
before/after calling ssl_decrypt_buf() these fields a converted to/from
mbedtls_record instances.
This commit does not yet remove the ssl->in_xxx fields, but makes a step
towards extending the lifetime of mbedtls_record structure representing
incoming records, by modifying ssl_parse_record_header() to setup an
instance of mbedtls_record, and setting the ssl->in_xxx fields from that
instance. The instance so-constructed isn't used further so far, and in
particular it is not yet consolidated with the instance set up for use
in ssl_decrypt_record(). That's for a later commit.
