The previous commit introduced a potential memory overread by reading
secret_len bytes from secret->p, while the is no guarantee that secret has
enough limbs for that.
Fix that by using an intermediate buffer and mpi_write_binary().
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
The dependency on a DRBG module was perhaps a bit strict for LTS branches, so
let's have an option that works with no DRBG when at least one SHA module is
present.
This changes the internal API of ecp_drbg_seed() by adding the size of the
MPI as a parameter. Re-computing the size from the number of limbs doesn't
work too well here as we're writing out to a fixed-size buffer and for some
curves (P-521) that would round up too much. Using mbedtls_mpi_get_len() is
not entirely satisfactory either as it would mean using a variable-length
encoding, with could open side channels.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
It results in smaller code than using CTR_DRBG (64 bytes smaller on ARMv6-M
with arm-none-eabi-gcc 7.3.1), so let's use this by default when both are
available.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
Unless MBEDTLS_ECP_NO_INTERNAL_RNG is defined, it's no longer possible for
f_rng to be NULL at the places that randomize coordinates.
Eliminate the NULL check in this case:
- it makes it clearer to reviewers that randomization always happens (unless
the user opted out at compile time)
- a NULL check in a place where it's easy to prove the value is never NULL
might upset or confuse static analyzers (including humans)
- removing the check saves a bit of code size
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
The case of MBEDTLS_ECP_RESTARTABLE isn't handled correctly yet: in that case
the DRBG instance should persist when resuming the operation. This will be
addressed in the next commit.
When both CTR_DRBG and HMAC_DRBG are available, CTR_DRBG is preferred since
both are suitable but CTR_DRBG tends to be faster and I needed a tie-breaker.
There are currently three possible cases to test:
- NO_INTERNAL_RNG is set -> tested in test_ecp_no_internal_rng
- it's unset and CTR_DRBG is available -> tested in the default config
- it's unset and CTR_DRBG is disabled -> tested in
test_ecp_internal_rng_no_ctr_drbg
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
See the comments in the code for how an attack would go, and the ChangeLog
entry for an impact assessment. (For ECDSA, leaking a few bits of the scalar
over several signatures translates to full private key recovery using a
lattice attack.)
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
The signature of mbedtls_mpi_cmp_mpi_ct() meant to support using it in
place of mbedtls_mpi_cmp_mpi(). This meant full comparison functionality
and a signed result.
To make the function more universal and friendly to constant time
coding, we change the result type to unsigned. Theoretically, we could
encode the comparison result in an unsigned value, but it would be less
intuitive.
Therefore we won't be able to represent the result as unsigned anymore
and the functionality will be constrained to checking if the first
operand is less than the second. This is sufficient to support the
current use case and to check any relationship between MPIs.
The only drawback is that we need to call the function twice when
checking for equality, but this can be optimised later if an when it is
needed.
In ecp_mul_comb(), if (!p_eq_g && grp->T == NULL) and then ecp_precompute_comb() fails (which can
happen due to OOM), then the new array of points T will be leaked (as it's newly allocated, but
hasn't been asigned to grp->T yet).
Symptom was a memory leak in ECDHE key exchange under low memory conditions.
The function mbedtls_ecp_gen_keypair_base did not wipe the stack buffer used to
hold the private exponent before returning. This commit fixes this by not using
a stack buffer in the first place but instead calling mpi_fill_random directly
to acquire the necessary random MPI.
Protecting the ECP hardware acceleratior with mutexes is inconsistent with the
philosophy of the library. Pre-existing hardware accelerator interfaces
leave concurrency support to the underlying platform.
Fixes#863
With this commit the Elliptic Curve Point interface is rewised. Two
compile time options has been removed to simplify the interface and
the function names got a new prefix that indicates that these functions
are for internal use and not part of the public interface.
The intended use of the abstraction layer for Elliptic Curve Point
arithmetic is to enable using hardware cryptographic accelerators.
These devices are a shared resource and the driver code rarely provides
thread safety.
This commit adds mutexes to the abstraction layer to protect the device
in a multi-threaded environment.
The compile time macros enabling the initialisation and deinitialisation
in the alternative Elliptic Curve Point arithmetic implementation had
names that did not end with '_ALT' as required by check-names.sh.
* development: (73 commits)
Bump yotta dependencies version
Fix typo in documentation
Corrected misleading fn description in ssl_cache.h
Corrected URL/reference to MPI library
Fix yotta dependencies
Fix minor spelling mistake in programs/pkey/gen_key.c
Bump version to 2.1.2
Fix CVE number in ChangeLog
Add 'inline' workaround where needed
Fix references to non-standard SIZE_T_MAX
Fix yotta version dependencies again
Upgrade yotta dependency versions
Fix compile error in net.c with musl libc
Add missing warning in doc
Remove inline workaround when not useful
Fix macroization of inline in C++
Changed attribution for Guido Vranken
Merge of IOTSSL-476 - Random malloc in pem_read()
Fix for IOTSSL-473 Double free error
Fix potential overflow in CertificateRequest
...
Conflicts:
include/mbedtls/ssl_internal.h
library/ssl_cli.c
