mbedtls_ssl_set_calc_verify_md() serves two purposes:
(a) It checks whether a hash algorithm is suitable to be used
in the CertificateVerify message.
(b) It updates the function callback pointing to the function that
computes handshake transcript for the CertificateVerify message
w.r.t. the chosen hash function.
Step (b) is only necessary when receiving the CertificateVerify
message, while writing the CertificateRequest only involves (a).
This commit modifies the writing code for the CertificateRequest
message to inline the check (a) and thereby avoiding the call to
mbedtls_ssl_calc_verify_md().
The fields
- mbedtls_ssl_handshake_params::max_major_ver,
- mbedtls_ssl_handshake_params::max_minor_ver
are used only for server-side RSA-based key exchanges
can be removed otherwise.
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 adapts the ClientHello parsing routines in ssl_srv.c
to use the ciphersuite traversal macros
MBEDTLS_SSL_BEGIN_FOR_EACH_CIPHERSUITE
MBEDTLS_SSL_END_FOR_EACH_CIPHERSUITE
introduced in the last commit, thereby making them work
both with and without MBEDTLS_SSL_SINGLE_CIPHERSUITE.
Another notable change concerns the ssl_ciphersuite_match:
Previous, this function would take a ciphersuite ID and a
pointer to a destination ciphersuite info structure as input
and write eithe NULL or a valid ciphersuite info structure
to that destination address, depending on whether the suite
corresponding to the given ID was suitable or not. The
function would always return 0 outside of a fatal error.
This commit changes this to ssl_ciphersuite_is_match() which
instead already takes a ciphersuite handle (which outside
of a hardcoded ciphersuite is the same as the ptr to a
ciphersuite info structure) and returns 0 or 1 (or a
negative error code in case of a fatal error) indicating
whether the suite corresponding to the handle was acceptable
or not. The conversion of the ciphersuite ID to the ciphersuite
info structure is done prior to calling ssl_ciphersuite_is_match().
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.
So far, the client-proposed list of elliptic curves was stored for the
duration of the entire handshake in a heap-allocated buffer referenced
from mbedtls_ssl_handshake_params::curves. It is used in the following
places:
1) When the server chooses a suitable ciphersuite, it checks that
it has a certificate matching the ciphersuite; in particular, if
the ciphersuite involves ECDHE, the server needs an EC certificate
with a curve suitable for the client.
2) When performing the ECDHE key exchange, the server choose one
curve among those proposed by the client which matches the server's
own supported curve configuration.
This commit removes the hold back the entire client-side curve list
during the handshake, by performing (1) and (2) on during ClientHello
parsing, and in case of (2) only remembering the curve chosen for ECDHE
within mbedtls_ssl_handshake_params.
* restricted/pr/608:
programs: Make `make clean` clean all programs always
ssl_tls: Enable Suite B with subset of ECP curves
windows: Fix Release x64 configuration
timing: Remove redundant include file
net_sockets: Fix typo in net_would_block()
Add all.sh component that exercises invalid_param checks
Remove mbedtls_param_failed from programs
Make it easier to define MBEDTLS_PARAM_FAILED as assert
Make test suites compatible with #include <assert.h>
Pass -m32 to the linker as well
Update library to 2.16.2
Use 'config.pl baremetal' in all.sh
Clarify ChangeLog entry for fix to #1628Fix#2370, minor typos and spelling mistakes
Add Changelog entry for clang test-ref-configs.pl fix
Enable more compiler warnings in tests/Makefile
Change file scoping of test helpers.function
* 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
...
Introduces MBEDTLS_SSL_CONF_CERT_REQ_CA_LIST which allows to configure
at compile-time whether a CA list should be included in the
CertificateRequest message sent by the server.
Impact on code-size:
| | GCC 8.2.1 | ARMC5 5.06 | ARMC6 6.12 |
| --- | --- | --- | --- |
| `libmbedtls.a` before | 23131 | 23805 | 26673 |
| `libmbedtls.a` after | 23099 | 23781 | 26639 |
| gain in Bytes | 32 | 24 | 34 |
mbedtls_ssl_read() can fail non-fatally, in which case
ssl_parse_certificate_verify() returned immediately without
calling mbedtls_x509_crt_pk_release(), which in turn lead
to a fatal error because of nested acquire calls in the
next call to the function.
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.
Add a new configuration option MBEDTLS_SSL_SESSION_RESUMPTION
to enable/disable the session resumption feature including
ticket and cache based session resumption.
So far, the CRT frame structure `mbedtls_x509_crt_frame` used
as `issuer_raw` and `subject_raw` the _content_ of the ASN.1
name structure for issuer resp. subject. This was in contrast
to the fields `issuer_raw` and `subject_raw` from the legacy
`mbedtls_x509_crt` structure, and caused some information
duplication by having both variants `xxx_no_hdr` and `xxx_with_hdr`
in `mbedtls_x509_crt` and `mbedtls_x509_crt_frame`.
This commit removes this mismatch by solely using the legacy
form of `issuer_raw` and `subject_raw`, i.e. those _including_
the ASN.1 name header.
Previously, `mbedtls_x509_crt_der_internal()` used the `version` field
(which is `0` after initialization but strictly greater than 0 once a
CRT has successfully been parsed) to determine whether an
`mbedtls_x509_crt` instance had already been setup.
Preparating for the removal of `version` from the structure, this
commit modifies the code to instead peek at the raw data pointer,
which is NULL as long as the CRT structure hasn't been setup with a CRT,
and will be kept in the new CRT structure.
The server-side routine `ssl_pick_cert()` is responsible for
picking a suitable CRT from the list of CRTs configured on the
server. For that, it previously used the public key context
from the certificate to check whether its type (including the
curve type for ECC keys) suits the ciphersuite and the client's
preferences.
This commit changes the code to instead use the PK context
holding the corresponding private key. For inferring the type
of the key, this makes no difference, and it removes a PK-from-CRT
extraction step which, if CRTs are stored raw, is costly in terms
of computation and memory: CRTs need to be parsed, and memory needs
to be allocated for the PK context.
The server-side routine `ssl_decrypt_encrypted_pms()` is
responsible for decrypting the RSA-encrypted PMS in case of
an RSA-based ciphersuite.
Previously, the code checked that the length of the PMS sent
by the client matches the bit length of the RSA key. This commit
removes this check -- thereby removing the need to access the
server's own CRT -- because the RSA decryption routine performs
this check itself, too.
`mbedtls_ssl_handshake_params::extended_ms` holds the state of the
ExtendedMasterSecret extension in the current handshake. Initially
set to 'disabled' for both client and server,
- the client sets it to 'enabled' as soon as it finds the ExtendedMS
extension in the `ServerHello` and it has advertised that extension
in its ClientHello,
- the server sets it to 'enabled' as soon as it finds the ExtendedMS
extension in the `ClientHello` and is willing to advertise is in its
`ServerHello`.
This commit slightly restructures this logic in prepraration for the
removal of `mbedtls_ssl_handshake_params::extended_ms` in case both
the use and the enforcement of the ExtendedMasterSecret extension have
been fixed at compile-time. Namely, in this case there is no need for
the `extended_ms` field in the handshake structure, as the ExtendedMS
must be in use if the handshake progresses beyond the Hello stage.
Paving the way for the removal of mbedtls_ssl_handshake_params::extended_ms
this commit introduces a temporary variable tracking the presence of the
ExtendedMS extension in the ClientHello/ServerHello messages, leaving
the derivation of `extended_ms` (and potential failure) to the end of
the parsing routine.
This commit is the first in a series demonstrating how code-size
can be reduced by hardcoding parts of the SSL configuration at
compile-time, focusing on the example of the configuration of
the ExtendedMasterSecret extension.
The flexibility of an SSL configuration defined a runtime vs.
compile-time is necessary for the use of Mbed TLS as a
dynamically linked library, but is undesirable in constrained
environments because it introduces the following overhead:
- Definition of SSL configuration API (code-size overhead)
(and on the application-side: The API needs to be called)
- Additional fields in the SSL configuration (RAM overhead,
and potentially code-size overhead if structures grow
beyond immediate-offset bounds).
- Dereferencing is needed to obtain configuration settings.
- Code contains branches and potentially additional structure
fields to distinguish between different configurations.
Considering the example of the ExtendedMasterSecret extension,
this instantiates as follows:
- mbedtls_ssl_conf_extended_master_secret() and
mbedtls_ssl_conf_extended_master_secret_enforced()
are introduced to configure the ExtendedMasterSecret extension.
- mbedtls_ssl_config contains bitflags `extended_ms` and
`enforce_extended_master_secret` reflecting the runtime
configuration of the ExtendedMasterSecret extension.
- Whenever we need to access these fields, we need a chain
of dereferences `ssl->conf->extended_ms`.
- Determining whether Client/Server should write the
ExtendedMasterSecret extension needs a branch
depending on `extended_ms`, and the state of the
ExtendedMasterSecret negotiation needs to be stored in a new
handshake-local variable mbedtls_ssl_handshake_params::extended_ms.
Finally (that's the point of ExtendedMasterSecret) key derivation
depends on this handshake-local state of ExtendedMasterSecret.
All this is unnecessary if it is known at compile-time that the
ExtendedMasterSecret extension is used and enforced:
- No API calls are necessary because the configuration is fixed
at compile-time.
- No SSL config fields are necessary because there are corresponding
compile-time constants instead.
- Accordingly, no dereferences for field accesses are necessary,
and these accesses can instead be replaced by the corresponding
compile-time constants.
- Branches can be eliminated at compile-time because the compiler
knows the configuration. Also, specifically for the ExtendedMasterSecret
extension, the field `extended_ms` in the handshake structure
is unnecessary, because we can fail immediately during the Hello-
stage of the handshake if the ExtendedMasterSecret extension
is not negotiated; accordingly, the non-ExtendedMS code-path
can be eliminated from the key derivation logic.
A way needs to be found to allow fixing parts of the SSL configuration
at compile-time which removes this overhead in case it is used,
while at the same time maintaining readability and backwards
compatibility.
This commit proposes the following approach:
From the user perspective, for aspect of the SSL configuration
mbedtls_ssl_config that should be configurable at compile-time,
introduce a compile-time option MBEDTLS_SSL_CONF_FIELD_NAME.
If this option is not defined, the field is kept and configurable
at runtime as usual. If the option is defined, the field is logically
forced to the value of the option at compile time.
Internally, read-access to fields in the SSL configuration which are
configurable at compile-time gets replaced by new `static inline` getter
functions which evaluate to the corresponding field access or to the
constant MBEDTLS_SSL_CONF_FIELD_NAME, depending on whether the latter
is defined or not.
Write-access to fields which are configurable at compile-time needs
to be removed: Specifically, the corresponding API itself either
needs to be removed or replaced by a stub function without effect.
This commit takes the latter approach, which has the benefit of
not requiring any change on the example applications, but introducing
the risk of mismatching API calls and compile-time configuration,
in case a user doesn't correctly keep track of which parts of the
configuration have been fixed at compile-time, and which haven't.
Write-access for the purpose of setting defaults is simply omitted.
If `MBEDTLS_SSL_KEEP_PEER_CERTIFICATE` is not set, `mbedtls_ssl_session`
contains the digest of the peer's certificate for the sole purpose of
detecting a CRT change on renegotiation. Hence, it is not needed if
renegotiation is disabled.
This commit removes the `peer_cert_digest` fields (and friends) from
`mbedtls_ssl_session` if
`!MBEDTLS_SSL_KEEP_PEER_CERTIFICATE + !MBEDTLS_SSL_RENEGOTIATION`,
which is a sensible configuration for constrained devices.
Apart from straightforward replacements of
`if !defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE)`
by
`if !defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE) && \
defined(MBEDTLS_SSL_RENEGOTIATION)`,
there's one notable change: On the server-side, the CertificateVerify
parsing function is a no-op if the client hasn't sent a certificate.
So far, this was determined by either looking at the peer CRT or the
peer CRT digest in the SSL session structure (depending on the setting
of `MBEDTLS_SSL_KEEP_PEER_CERTIFICATE`), which now no longer works if
`MBEDTLS_SSL_KEEP_PEER_CERTIFICATE` is unset. Instead, this function
now checks whether the temporary copy of the peer's public key within
the handshake structure is initialized or not (which is also a
beneficial simplification in its own right, because the pubkey is
all the function needs anyway).
The server expects a CertificateVerify message only if it has
previously received a Certificate from the client.
So far, this was detected by looking at the `peer_cert` field
in the current session. Preparing to remove the latter, this
commit changes this to instead determine the presence of a peer
certificate by checking the new `peer_cert_digest` pointer.
We must dispatch between the peer's public key stored as part of
the peer's CRT in the current session structure (situation until
now, and future behaviour if MBEDTLS_SSL_KEEP_PEER_CERTIFICATE is
enabled), and the sole public key stored in the handshake structure
(new, if MBEDTLS_SSL_KEEP_PEER_CERTIFICATE is disabled).
This commit simplifies the client-side code for outgoing CertificateVerify
messages, and server-side code for outgoing CertificateRequest messages and
incoming CertificateVerify messages, through the use of the macro
`MBEDTLS_KEY_EXCHANGE__CERT_REQ_ALLOWED__ENABLED`
indicating whether a ciphersuite allowing CertificateRequest messages
is enabled in the configuration, as well as the helper function
`mbedtls_ssl_ciphersuite_cert_req_allowed()`
indicating whether a particular ciphersuite allows CertificateRequest
messages.
These were already used in the client-side code to simplify the
parsing functions for CertificateRequest messages.
This commit handles occurrences of case 2 and 3 in the following list:
1. Some DTLS-specific code with no TLS-specific code (most frequent)
2. Some specific code for each protocol
3. Some TLS-specific code with no DTLS-specific code (least frequent)
Case 3 previously had a weird structure in that the TLS-specific code was
always present, but the if structure was conditional on DTLS being enabled.
This is changed by this commit to a more logical structure where both the code
and the test are conditional on TLS being enabled.
Case 2 doesn't require any change in the code structure in general. However,
there is one occurrence where the if/else structure is simplified to assigning
the result of a boolean operation, and one occurrence where I also noticed a
useless use of `ssl_ep_len()` in a TLS-specific branch, that I turned to the
constant 0 as it makes more sense.
Case 1 will be handled in the next commit, as it can easily be handled in an
automated way - only cases 2 and 3 (sometimes) required manual intervention.
The list of occurrences for cases 2 and 3 was established manually by looking
for occurrences of '= MBEDTLS_SSL_TRANSPORT_' in the code and manually
checking if there was a TLS-specific branch.
New sizes (see previous commit for the measuring script):
```
both
text data bss dec hex filename
1820 0 4 1824 720 debug.o (ex library/libmbedtls.a)
0 0 0 0 0 net_sockets.o (ex library/libmbedtls.a)
548 0 0 548 224 ssl_cache.o (ex library/libmbedtls.a)
11155 0 596 11751 2de7 ssl_ciphersuites.o (ex library/libmbedtls.a)
17156 0 0 17156 4304 ssl_cli.o (ex library/libmbedtls.a)
460 0 0 460 1cc ssl_cookie.o (ex library/libmbedtls.a)
17649 0 0 17649 44f1 ssl_srv.o (ex library/libmbedtls.a)
800 0 0 800 320 ssl_ticket.o (ex library/libmbedtls.a)
39286 60 0 39346 99b2 ssl_tls.o (ex library/libmbedtls.a)
88874 60 600 89534 15dbe (TOTALS)
DTLS-only
text data bss dec hex filename
1820 0 4 1824 720 debug.o (ex library/libmbedtls.a)
0 0 0 0 0 net_sockets.o (ex library/libmbedtls.a)
548 0 0 548 224 ssl_cache.o (ex library/libmbedtls.a)
11155 0 596 11751 2de7 ssl_ciphersuites.o (ex library/libmbedtls.a)
17068 0 0 17068 42ac ssl_cli.o (ex library/libmbedtls.a)
460 0 0 460 1cc ssl_cookie.o (ex library/libmbedtls.a)
17553 0 0 17553 4491 ssl_srv.o (ex library/libmbedtls.a)
800 0 0 800 320 ssl_ticket.o (ex library/libmbedtls.a)
38499 60 0 38559 969f ssl_tls.o (ex library/libmbedtls.a)
87903 60 600 88563 159f3 (TOTALS)
TLS-only
text data bss dec hex filename
1820 0 4 1824 720 debug.o (ex library/libmbedtls.a)
0 0 0 0 0 net_sockets.o (ex library/libmbedtls.a)
548 0 0 548 224 ssl_cache.o (ex library/libmbedtls.a)
11155 0 596 11751 2de7 ssl_ciphersuites.o (ex library/libmbedtls.a)
14912 0 0 14912 3a40 ssl_cli.o (ex library/libmbedtls.a)
460 0 0 460 1cc ssl_cookie.o (ex library/libmbedtls.a)
15868 0 0 15868 3dfc ssl_srv.o (ex library/libmbedtls.a)
800 0 0 800 320 ssl_ticket.o (ex library/libmbedtls.a)
27619 60 0 27679 6c1f ssl_tls.o (ex library/libmbedtls.a)
73182 60 600 73842 12072 (TOTALS)
```
The function mbedtls_ssl_hdr_len() returns the length of the record
header (so far: always 13 Bytes for DTLS, and always 5 Bytes for TLS).
With the introduction of the CID extension, the lengths of record
headers depends on whether the records are incoming or outgoing,
and also on the current transform.
Preparing for this, this commit splits mbedtls_ssl_hdr_len() in two
-- so far unmodified -- functions mbedtls_ssl_in_hdr_len() and
mbedtls_ssl_out_hdr_len() and replaces the uses of mbedtls_ssl_hdr_len()
according to whether they are about incoming or outgoing records.
There is no need to change the signature of mbedtls_ssl_{in/out}_hdr_len()
in preparation for its dependency on the currently active transform,
since the SSL context is passed as an argument, and the currently
active transform is referenced from that.
Prior to this commit, the security parameter struct `ssl_transform`
contained a `ciphersuite_info` field pointing to the information
structure for the negotiated ciphersuite. However, the only
information extracted from that structure that was used in the core
encryption and decryption functions `ssl_encrypt_buf`/`ssl_decrypt_buf`
was the authentication tag length in case of an AEAD cipher.
The present commit removes the `ciphersuite_info` field from the
`ssl_transform` structure and adds an explicit `taglen` field
for AEAD authentication tag length.
This is in accordance with the principle that the `ssl_transform`
structure should contain the raw parameters needed for the record
encryption and decryption functions to work, but not the higher-level
information that gave rise to them. For example, the `ssl_transform`
structure implicitly contains the encryption/decryption keys within
their cipher contexts, but it doesn't contain the SSL master or
premaster secrets. Likewise, it contains an explicit `maclen`, while
the status of the 'Truncated HMAC' extension -- which determines the
value of `maclen` when the `ssl_transform` structure is created in
`ssl_derive_keys` -- is not contained in `ssl_transform`.
The `ciphersuite_info` pointer was used in other places outside
the encryption/decryption functions during the handshake, and for
these functions to work, this commit adds a `ciphersuite_info` pointer
field to the handshake-local `ssl_handshake_params` structure.
The SSL module accesses ECDH context members directly. This can't work
with the new context, where we can't make any assumption about the
implementation of the context.
This commit makes use of the new functions to avoid accessing ECDH
members directly. The only members that are still accessed directly are
the group ID and the point format and they are independent from the
implementation.
Previously, mbedtls_ssl_read_record() always updated the handshake
checksum in case a handshake record was received. While desirable
most of the time, for the CertificateVerify message the checksum
update must only happen after the message has been fully processed,
because the validation requires the handshake digest up to but
excluding the CertificateVerify itself. As a remedy, the bulk
of mbedtls_ssl_read_record() was previously duplicated within
ssl_parse_certificate_verify(), hardening maintenance in case
mbedtls_ssl_read_record() is subject to changes.
This commit adds a boolean parameter to mbedtls_ssl_read_record()
indicating whether the checksum should be updated in case of a
handshake message or not. This allows using it also for
ssl_parse_certificate_verify(), manually updating the checksum
after the message has been processed.
This commit is another step towards supporting the packing of
multiple records within a single datagram.
Previously, the incremental outgoing record sequence number was
statically stored within the record buffer, at its final place
within the record header. This slightly increased efficiency
as it was not necessary to copy the sequence number when writing
outgoing records.
When allowing multiple records within a single datagram, it is
necessary to allow the position of the current record within the
datagram buffer to be flexible; in particular, there is no static
address for the record sequence number field within the record header.
This commit introduces an additional field `cur_out_ctr` within
the main SSL context structure `mbedtls_ssl_context` to keep track
of the outgoing record sequence number independent of the buffer used
for the current record / datagram. Whenever a new record is written,
this sequence number is copied to the the address `out_ctr` of the
sequence number header field within the current outgoing record.
This will allow fragmentation to always happen in the same place, always from
a buffer distinct from ssl->out_msg, and with the same way of resuming after
returning WANT_WRITE
For the situation where the mbedTLS device has limited RAM, but the
other end of the connection doesn't support the max_fragment_length
extension. To be spec-compliant, mbedTLS has to keep a 16384 byte
incoming buffer. However the outgoing buffer can be made smaller without
breaking spec compliance, and we save some RAM.
See comments in include/mbedtls/config.h for some more details.
(The lower limit of outgoing buffer size is the buffer size used during
handshake/cert negotiation. As the handshake is half-duplex it might
even be possible to store this data in the "incoming" buffer during the
handshake, which would save even more RAM - but it would also be a lot
hackier and error-prone. I didn't really explore this possibility, but
thought I'd mention it here in case someone sees this later on a mission
to jam mbedTLS into an even tinier RAM footprint.)
Fix compilation warnings with IAR toolchain, on 32 bit platform.
Reported by rahmanih in #683
This is based on work by Ron Eldor in PR #750, some of which was independently
fixed by Azim Khan and already merged in PR #1646.
In ssl_parse_encrypted_pms, some operational failures from
ssl_decrypt_encrypted_pms lead to diff being set to a value that
depended on some uninitialized unsigned char and size_t values. This didn't
affect the behavior of the program (assuming an implementation with no
trap values for size_t) because all that matters is whether diff is 0,
but Valgrind rightfully complained about the use of uninitialized
memory. Behave nicely and initialize the offending memory.
Rename to mbedtls_ssl_get_async_operation_data and
mbedtls_ssl_set_async_operation_data so that they're about
"async operation data" and not about some not-obvious "data".
When a handshake step starts an asynchronous operation, the
application needs to know which SSL connection the operation is for,
so that when the operation completes, the application can wake that
connection up. Therefore the async start callbacks need to take the
SSL context as an argument. It isn't enough to let them set a cookie
in the SSL connection, the application needs to be able to find the
right SSL connection later.
Also pass the SSL context to the other callbacks for consistency. Add
a new field to the handshake that the application can use to store a
per-connection context. This new field replaces the former
context (operation_ctx) that was created by the start function and
passed to the resume function.
Add a boolean flag to the handshake structure to track whether an
asynchronous operation is in progress. This is more robust than
relying on the application to set a non-null application context.
In the refactoring of ssl_parse_encrypted_pms, I advertently broke the
case when decryption signalled an error, with the variable ret getting
overwritten before calculating diff. Move the calculation of diff
immediately after getting the return code to make the connection more
obvious. Also move the calculation of mask immediately after the
calculation of diff, which doesn't change the behavior, because I find
the code clearer that way.
Conflict resolution:
* ChangeLog: put the new entry from my branch in the proper place.
* include/mbedtls/error.h: counted high-level module error codes again.
* include/mbedtls/ssl.h: picked different numeric codes for the
concurrently added errors; made the new error a full sentence per
current standards.
* library/error.c: ran scripts/generate_errors.pl.
* library/ssl_srv.c:
* ssl_prepare_server_key_exchange "DHE key exchanges": the conflict
was due to style corrections in development
(4cb1f4d49c) which I merged with
my refactoring.
* ssl_prepare_server_key_exchange "For key exchanges involving the
server signing", first case, variable declarations: merged line
by line:
* dig_signed_len: added in async
* signature_len: removed in async
* hashlen: type changed to size_t in development
* hash: size changed to MBEDTLS_MD_MAX_SIZE in async
* ret: added in async
* ssl_prepare_server_key_exchange "For key exchanges involving the
server signing", first cae comment: the conflict was due to style
corrections in development (4cb1f4d49c)
which I merged with my comment changes made as part of refactoring
the function.
* ssl_prepare_server_key_exchange "Compute the hash to be signed" if
`md_alg != MBEDTLS_MD_NONE`: conflict between
ebd652fe2d
"ssl_write_server_key_exchange: calculate hashlen explicitly" and
46f5a3e9b4 "Check return codes from
MD in ssl code". I took the code from commit
ca1d742904 made on top of development
which makes mbedtls_ssl_get_key_exchange_md_ssl_tls return the
hash length.
* programs/ssl/ssl_server2.c: multiple conflicts between the introduction
of MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS and new auxiliary functions and
definitions for async support, and the introduction of idle().
* definitions before main: concurrent additions, kept both.
* main, just after `handshake:`: in the loop around
mbedtls_ssl_handshake(), merge the addition of support for
MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS and SSL_ASYNC_INJECT_ERROR_CANCEL
with the addition of the idle() call.
* main, if `opt.transport == MBEDTLS_SSL_TRANSPORT_STREAM`: take the
code from development and add a check for
MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS.
* main, loop around mbedtls_ssl_read() in the datagram case:
take the code from development and add a check for
MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS; revert to a do...while loop.
* main, loop around mbedtls_ssl_write() in the datagram case:
take the code from development and add a check for
MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS; revert to a do...while loop.
