In order to for tests to pass from the previous commit (which it mandatory for all pk verify/sign
functions to be given a hash_len that is exactly equal to the message digest length of md_alg) the
hash_len that is supplied to the fucntion cannot be MBEDTLS_MD_MAX_SIZE. This would result in all tests failing. Since the md alg for all of these funtions are SHA256, we can use mbedtls functions to get
the required length of a SHA256 digest (32 bytes). Then that number can be used for allocating the
hash buffer.
Signed-off-by: Nick Child <nick.child@ibm.com>
The function `pk_hashlen_helper` exists to ensure a valid hash_len is
used in pk_verify and pk_sign functions. This function has been
used to adjust to the corrsponding hash_len if the user passes in 0
for the hash_len argument based on the md algorithm given. If the user
does not pass in 0 as the hash_len, then it is not adjusted. This is
problematic if the user gives a hash_len and hash buffer that is less than the
associated length of the md algorithm. This error would go unchecked
and eventually lead to buffer overread when given to specific pk_sign/verify
functions, since they both ignore the hash_len argument if md_alg is not MBEDTLS_MD_NONE.
This commit, adds a conditional to `pk_hashlen_helper` so that an
error is thrown if the user specifies a hash_length (not 0) and it is
not equal to the expected for the associated message digest algorithm.
This aligns better with the api documentation where it states "If
hash_len is 0, then the length associated with md_alg is used instead,
or an error returned if it is invalid"
Signed-off-by: Nick Child <nick.child@ibm.com>
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
It is enough only one test case for a key type, algorithm pair when
testing the implicit usage flags.
Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
Add test cases validating that if a stored key only had the hash policy,
then after loading it psa_get_key_attributes reports that it also has the
message policy, and the key can be used with message functions.
Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
These macros were moved into a header and now check-names.sh is failing.
Add an MBEDTLS_ prefix to the macro names to make it pass.
Signed-off-by: Janos Follath <janos.follath@arm.com>
Negative x coordinate was tested with the value -1. It happens to be one
of the low order points both for Curve25519 and Curve448 and might be
rejected because of that and not because it is negative. Make sure that
x < 0 is the only plausible reason for the point to be rejected.
Signed-off-by: Janos Follath <janos.follath@arm.com>
We were already rejecting them at the end, due to the fact that with the
usual (x, z) formulas they lead to the result (0, 0) so when we want to
normalize at the end, trying to compute the modular inverse of z will
give an error.
If we wanted to support those points, we'd a special case in
ecp_normalize_mxz(). But it's actually permitted by all sources (RFC
7748 say we MAY reject 0 as a result) and recommended by some to reject
those points (either to ensure contributory behaviour, or to protect
against timing attack when the underlying field arithmetic is not
constant-time).
Since our field arithmetic is indeed not constant-time, let's reject
those points before they get mixed with sensitive data (in
ecp_mul_mxz()), in order to avoid exploitable leaks caused by the
special cases they would trigger. (See the "May the Fourth" paper
https://eprint.iacr.org/2017/806.pdf)
Signed-off-by: Janos Follath <janos.follath@arm.com>
