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.).
No effect for now, just declaring it here, implemented in subsequent commits.
The option requires MBEDTLS_USE_TINYCRYPT and is incompatible with
MBEDTLS_PK_RSA_ALT_SUPPORT and MBEDTLS_RSA_C.
Currently users (including the X.509 and SSL libraries) assume that if both PK
and RSA are enabled, then RSA is available through PK. If we allowed RSA to be
enabled together with PK_SINGLE_TYPE, we'd break that assumption. Going
through the code to find all place that rely on that assumption and fix them
would be cumbersome, and people who want PK_SINGLE_TYPE are unlikely to care
about RSA anyway, so let's just make them incompatible.
This is also consistent with what's done in the MD module: MD_SINGLE_HASH
requires that exactly one hash be enabled.
The programs assume that including "pk.h" brings up "bignum.h". When
MBEDTLS_USE_TINYCRYPT is enabled and MBEDTLS_RSA_C is disabled, that
assumption no longer holds. Fix that by explicitly including bignum.h from the
programs that need it.
This is a bug pre-existing to this PR, fixed here to enable the inclusion of a
test with a config that happens to reveal it.
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.
This commit adds a LICENSE file and README file to tinycrypt, to help auditing
of the source code for licenses and also to indicate the origin of the work.
- 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.
