The blinding applied to the scalar before modular inversion is
inadequate. Bignum is not constant time/constant trace, side channel
attacks can retrieve the blinded value, factor it (it is smaller than
RSA keys and not guaranteed to have only large prime factors). Then the
key can be recovered by brute force.
Reducing the blinded value makes factoring useless because the adversary
can only recover pk*t+z*N instead of pk*t.
* origin/pr/2878:
mbedtls_hmac_drbg_set_entropy_len() only matters when reseeding
mbedtls_ctr_drbg_set_entropy_len() only matters when reseeding
mbedtls_ctr_drbg_seed: correct maximum for len
Add a note about CTR_DRBG security strength to config.h
CTR_DRBG: more consistent formatting and wording
DRBG documentation: Relate f_entropy arguments to the entropy module
Add ChangeLog entry for the DRBG documentation improvements
HMAC_DRBG documentation improvements
CTR_DRBG: explain the security strength and the entropy input length
CTR_DRBG documentation improvements
The documentation of HMAC_DRBG erroneously claimed that
mbedtls_hmac_drbg_set_entropy_len() had an impact on the initial
seeding. This is in fact not the case: mbedtls_hmac_drbg_seed() forces
the entropy length to its chosen value. Fix the documentation.
The documentation of CTR_DRBG erroneously claimed that
mbedtls_ctr_drbg_set_entropy_len() had an impact on the initial
seeding. This is in fact not the case: mbedtls_ctr_drbg_seed() forces
the initial seeding to grab MBEDTLS_CTR_DRBG_ENTROPY_LEN bytes of
entropy. Fix the documentation and rewrite the discussion of the
entropy length and the security strength accordingly.
* State explicit whether several numbers are in bits or bytes.
* Clarify whether buffer pointer parameters can be NULL.
* Minor wording and formatting improvements.
* origin/pr/2704:
Adapt auth_crypt_tv usage to 2.7
Add missing dependencies in test_suite_cipher.gcm
Adapt ChangeLog
Add NIST AES GCM test vectors to single-step cipher API test suite
Explain what how entropy input length is determined from the
configuration, and how this in turn determines the security strength.
Explain how the nonce is obtained during initialization.
* State explicit whether several numbers are in bits or bytes.
* Clarify whether buffer pointer parameters can be NULL.
* Clarify some terminology.
* Minor wording and formatting improvements.
Reduce the stack usage of the `test_suite_pkcs1_v21` by reducing the
size of the buffers used in the tests, to a reasonable big enough size,
and change the size sent to the API to sizeof output.
Reduce the stack usage of the `test_suite_rsa` by reducing the
size of the buffers used in the tests, to a reasonable big enough size,
and change the data size to decrypt in the data file.
* origin/pr/2828:
Enable MBEDTLS_MEMORY_DEBUG in memory buffer alloc test in all.sh
Remove unnecessary memory buffer alloc unsets
Disable DTLS proxy tests for MEMORY_BUFFER_ALLOC test
all.sh: restructure memory allocator tests
Add missing dependency in memory buffer alloc set in all.sh
Don't set MBEDTLS_MEMORY_DEBUG through `scripts/config.pl full`
Add cfg dep MBEDTLS_MEMORY_DEBUG->MBEDTLS_MEMORY_BUFFER_ALLOC_C
Add all.sh run with full config and ASan enabled
Add all.sh run with MBEDTLS_MEMORY_BUFFER_ALLOC_C enabled
Update documentation of exceptions for `config.pl full`
Adapt all.sh to removal of buffer allocator from full config
Disable memory buffer allocator in full config
Check dependencies of MBEDTLS_MEMORY_BACKTRACE in check_config.h
With the removal of MBEDTLS_MEMORY_BUFFER_ALLOC_C from the
full config, there are no tests for it remaining in all.sh.
This commit adds a build as well as runs of `make test` and
`ssl-opt.sh` with MBEDTLS_MEMORY_BUFFER_ALLOC_C enabled to all.sh.
Previously, numerous all.sh tests manually disabled the buffer allocator
or memory backtracting after setting a full config as the starting point.
With the removal of MBEDTLS_MEMORY_BACKTRACE and MBEDTLS_MEMORY_BUFFER_ALLOC_C
from full configs, this is no longer necessary.
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.
compat.sh used to skip OpenSSL altogether for DTLS 1.2, because older
versions of OpenSSL didn't support it. But these days it is supported.
We don't want to use DTLS 1.2 with OpenSSL unconditionally, because we
still use legacy versions of OpenSSL to test with legacy ciphers. So
check whether the version we're using supports it.
