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_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.
The previous code writes the content (the EC curve list) of the extension
before writing the extension length field at the beginning, which is common
in the library in places where we don't know the length upfront. Here,
however, we do traverse the EC curve list upfront to infer its length
and do the bounds check, so we can reorder the code to write the extension
linearly and hence improve readability.
ssl_write_supported_elliptic_curves_ext() is guarded by
```
#if defined(MBEDTLS_ECDH_C) || defined(MBEDTLS_ECDSA_C) || \
defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
```
each of which implies (by check_config.h) that MBEDTLS_ECP_C
is enabled.
If the minor/major version is enforced at compile-time, the `major_ver`
and `minor_ver` fields in `mbedtls_ssl_context` are redundant and can
be removed.
This commit introduces the numeric compile-time constants
- MBEDTLS_SSL_CONF_MIN_MINOR_VER
- MBEDTLS_SSL_CONF_MAX_MINOR_VER
- MBEDTLS_SSL_CONF_MIN_MAJOR_VER
- MBEDTLS_SSL_CONF_MAX_MAJOR_VER
which, when defined, overwrite the runtime configurable fields
mbedtls_ssl_config::min_major_ver etc. in the SSL configuration.
As for the preceding case of the ExtendedMasterSecret configuration,
it also introduces and puts to use getter functions for these variables
which evaluate to either a field access or the macro value, maintaining
readability of the code.
The runtime configuration API mbedtls_ssl_conf_{min|max}_version()
is kept for now but has no effect if MBEDTLS_SSL_CONF_XXX are set.
This is likely to be changed in a later commit but deliberately omitted
for now, in order to be able to study code-size benefits earlier in the
process.
If MBEDTLS_SSL_SINGLE_CIPHERSUITE is enabled, the type
mbedtls_ssl_ciphersuite_handle_t
is logically a boolean (concretely realized as `unsigned char`),
containing the invalid handle and the unique valid handle, which
represents the single enabled ciphersuite.
The SSL session structure mbedtls_ssl_session contains an instance
of mbedtls_ssl_ciphersuite_handle_t which is guaranteed to be valid,
and which is hence redundant in any two-valued implementation of
mbedtls_ssl_ciphersuite_handle_t.
This commit replaces read-uses of
mbedtls_ssl_session::ciphersuite_info
by a getter functions which, and defines this getter function
either by just reading the field from the session structure
(in case MBEDTLS_SSL_SINGLE_CIPHERSUITE is disabled), or by
returning the single valid ciphersuite handle (in case
MBEDTLS_SSL_SINGLE_CIPHERSUITE is enabled) and removing the
field from mbedtls_ssl_session in this case.
If MBEDTLS_SSL_SINGLE_CIPHERSUITE is enabled, the type
mbedtls_ssl_ciphersuite_handle_t
is logically a boolean (concretely realized as `unsigned char`),
containing the invalid handle and the unique valid handle, which
represents the single enabled ciphersuite.
The SSL handshake structure mbedtls_ssl_handshake_params contains
an instance of mbedtls_ssl_ciphersuite_handle_t which is guaranteed
to be valid, and which is hence redundant in any two-valued
implementation of mbedtls_ssl_ciphersuite_handle_t.
This commit replaces read-uses of
mbedtls_ssl_handshake_params::ciphersuite_info
by a getter functions which, and defines this getter function
either by just reading the field from the handshake structure
(in case MBEDTLS_SSL_SINGLE_CIPHERSUITE is disabled), or by
returning the single valid ciphersuite handle (in case
MBEDTLS_SSL_SINGLE_CIPHERSUITE is enabled) and removing the
field from mbedtls_ssl_handshake_params in this case.
This commit modifies the ClientHello writing routine ssl_write_client_hello
in ssl_cli.c to switch between
(a) listing all runtime configured ciphersuites
(in case MBEDTLS_SSL_SINGLE_CIPHERSUITE is not defined)
(b) listing just the single hardcoded ciphersuite
(in case MBEDTLS_SSL_SINGLE_CIPHERSUITE is defined)
The approach taken is to introduce a pair of helper macros
MBEDTLS_SSL_BEGIN_FOR_EACH_CIPHERSUITE( ssl, ver, info )
MBEDTLS_SSL_END_FOR_EACH_CIPHERSUITE
which when delimiting a block of code lead to that block of
code being run once for each ciphersuite that's enabled in the
context `ssl` and version `ver`, referenced through the (fresh)
`info` variable. Internally, this is implemented either through
a plain `for` loop traversing the runtime configured ciphersuite
list (if MBEDTLS_SSL_SINGLE_CIPHERSUITE is disabled) or by just
hardcoding `info` to the single enabled ciphersuite (if
MBEDTLS_SSL_SINGLE_CIPHERSUITE is enabled).
These helper macros will prove useful whereever previous code
traversed the runtime configured ciphersuite list, but adaptations
of those occasions outside ClientHello writing are left for later
commits.
This commit introduces an internal zero-cost abstraction layer for
SSL ciphersuites: Instead of addressing ciphersuites via pointers
to instances of mbedtls_ssl_ciphersuite_t and accessing their fields
directly, this commit introduces an opaque type
mbedtls_ssl_ciphersuite_handle_t,
and getter functions
mbedtls_ssl_suite_get_xxx()
operating on ciphersuite handles.
The role of NULL is played by a new macro constant
MBEDTLS_SSL_CIPHERSUITE_INVALID_HANDLE
which results of functions returning handles can be checked against.
(For example, when doing a lookup of a ciphersuite from a peer-provided
ciphersuite ID in the per's Hello message).
The getter functions have the validity of the handle as a precondition
and are undefined if the handle is invalid.
So far, there's only one implementation of this abstraction layer, namely
mbedtls_ssl_ciphersuite_handle_t being mbedtls_ssl_ciphersuite_t const *
and
getter functions being field accesses.
In subsequent commits, however, the abstraction layer will be useful
to save code in the situation where only a single ciphersuite is enabled.
* restricted/pr/594:
Adapt baremetal.h and baremetal.sh
Don't incl. CAs in CertReq message in baremetal build
Allow config'n of incl of CertificateReq CA list Y/N at compile-time
Allow configuration of endpoint (cli/srv) at compile-time
Allow configuration of read timeouts at compile-time
Allow configuration of ConnectionID at compile-time
Allow compile-time configuration of legacy renegotiation
Allow compile-time configuration of authentication mode
Allow compile-time configuration of DTLS badmac limit
Allow compile-time configuration of DTLS anti replay
* restricted/pr/601: (27 commits)
Fix compile-time guard for optional field in struct
Move code to reduce probability of conflicts
Fix typos caught by check-names.sh
Clarify conditions related to resumption in client
Introduce getter function for renego_status
Add getter function for handshake->resume
Remove now-redundant code
Remove cache callbacks from config on client
Fix a few style issues
Expand documentation of new options a bit
Fix renaming oversight in documentation
Remove backticks in doxygen in config.h
Declare dependency on tickets for two ssl-opt.sh tests
Exclude new negative options from config.pl full
Restore config.h defaults
Address review comments
Fix ssl_cli resumption guards
Fix check-files, check-names and check-generated-features
Add test to all.sh
Add changelog entry
...
* restricted/pr/584: (140 commits)
Remove superfluous new line in x509.c
Add comment about X.509 name comparison of buffer with itself
[Fixup] Add missing PK release call in Cert Verify parsing
Fix guard controlling whether nested acquire calls are allowed
Add X.509 CRT test for nested calls for CRT frame / PK acquire
Don't return threading error on release()-without-acquire() calls
Don't allow nested CRT acquire()-calls if MBEDTLS_X509_ALWAYS_FLUSH
Make X.509 CRT cache reference counting unconditional
Remove memory buffer alloc from i386 test in all.sh
Don't mention pk_sign() in the context of public-key contexts
Don't use assertion for failures of mbedtls_x509_crt_x_acquire()
Fix copy pasta in x509_crt.h
Reference copy-less versions of X.509 CRT frame/PK getters
x509_crt.c: Add blank line to increase readability
[FIXUP] Fix bug in ASN.1 traversal of silently ignored tag
[FIXUP] Fix typo in declaration of mbedtls_x509_memcasecmp()
Move signature-info extraction out of MBEDTLS_X509_REMOVE_INFO
Fix certificate validity checking logic to work with !TIME_DATE
Simplify X.509 CRT version check in UID parsing
Remove unused variable warning in on-demand X.509 parsing
...
While not strictly related to this PR, this change improves readability in
some resumption-related runtime conditions that previously had rather ugly
preprocessor directives in the middle of already complex predicates.
Due to previous change of conditions, this is now in the 'else' branch of 'if
resume == 1' and the only allowed values are 0 or 1, so setting to 0 is
redundant.
Add a new configuration option MBEDTLS_SSL_SESSION_RESUMPTION
to enable/disable the session resumption feature including
ticket and cache based session resumption.
