The sliding window exponentiation algorithm is vulnerable to
side-channel attacks. As a countermeasure we add exponent blinding in
order to prevent combining the results of fifferent measurements.
This commits handles the case when the Chinese Remainder Theorem is NOT
used to accelerate computations.
The test case was generated by modifying our signature code so that it
produces a 7-byte long padding (which also means garbage at the end, so it is
essential in to check that the error that is detected first is indeed the
padding rather than the final length check).
The PKCS#1 standard says nothing about the relation between P and Q
but many libraries guarantee P>Q and mbed TLS did so too in earlier
versions.
This commit restores this behaviour.
Once the mutex is acquired, we must goto cleanup rather that return.
Since cleanup adjusts the return value, adjust that in test cases.
Also, at cleanup we don't want to overwrite 'ret', or we'll loose track of
errors.
see #257
* commit 'ce60fbe':
Fix potential timing difference with RSA PMS
Update Changelog for recent merge
Added more constant-time code and removed biases in the prime number generation routines.
Conflicts:
library/bignum.c
library/ssl_srv.c
* mbedtls-1.3:
Add missing depends in x509 programs
Simplify ifdef checks in programs/x509
Fix thread safety issue in RSA operations
Add test certificate for bitstring in DN
Add support for X.520 uniqueIdentifier
Accept bitstrings in X.509 names
The race was due to mpi_exp_mod storing a Montgomery coefficient in the
context (RM, RP, RQ).
The fix was verified with -fsanitize-thread using ssl_pthread_server and two
concurrent clients.
A more fine-grained fix should be possible, locking just enough time to check
if those values are OK and set them if not, rather than locking for the whole
mpi_exp_mod() operation, but it will be for later.
