The certificate passed to async callbacks may not be the one set by
mbedtls_ssl_conf_own_cert. For example, when using an SNI callback,
it's whatever the callback is using. Document this, and add a test
case (and code sample) with SNI.
Add a test case for SSL asynchronous signature where f_async_resume is
called twice. Verify that f_async_sign_start is only called once.
This serves as a non-regression test for a bug where f_async_sign_start
was only called once, which turned out to be due to a stale build
artifacts with mismatched numerical values of
MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS.
The AES OFB self-test made use of a variable `offset` but failed to have a
preprocessor condition around it, so unless CTR and CBC were enabled, the
variable would be undeclared.
In ssl_parse_encrypted_pms, some operational failures from
ssl_decrypt_encrypted_pms lead to diff being set to a value that
depended on some uninitialized unsigned char and size_t values. This didn't
affect the behavior of the program (assuming an implementation with no
trap values for size_t) because all that matters is whether diff is 0,
but Valgrind rightfully complained about the use of uninitialized
memory. Behave nicely and initialize the offending memory.
The code paths in the library are different for decryption and for
signature. Improve the test coverage by doing some error path tests
for decryption in addition to signature.
In ssl_server2, the private key objects are normally local variables
of the main function. However this does not hold for private keys in
the SNI configuration. When async callbacks are used, the test code
transfers the ownership of the private keys to the async callbacks.
Therefore the test code must free the SNI private keys through the
async callbacks (but it must not free the straight private keys this
way since they are not even heap-allocated).
When testing async callbacks with SNI, make all the keys async, not
just the first one. Otherwise the test is fragile with respect to
whether a key is used directly or through the async callbacks.
The XTS configuration option MBEDTLS_CIPHER_MODE_XTS currently only enables
XTS for AES. So, don't say it enables XTS for "symmetric ciphers", just
AES. This helps to avoid being misleading.
THe function `mbedtls_gf128mul_x_ble()` doesn't multiply by x, x^4, and
x^8. Update the function description to properly describe what the function
does.
mbedtls_aes_crypt_xts() currently takes a `bits_length` parameter, unlike
the other block modes. Change the parameter to accept a bytes length
instead, as the `bits_length` parameter is not actually ever used in the
current implementation.
Add a new context structure for XTS. Adjust the API for XTS to use the new
context structure, including tests suites and the benchmark program. Update
Doxgen documentation accordingly.
AES-XEX is a building block for other cryptographic standards and not yet a
standard in and of itself. We'll just provide the standardized AES-XTS
algorithm, and not AES-XEX. The AES-XTS algorithm and interface provided
can be used to perform the AES-XEX algorithm when the length of the input
is a multiple of the AES block size.
If we're unlucky with memory placement, gf128mul_table_bbe may spread over
two cache lines and this would leak b >> 63 to a cache timing attack.
Instead, take an approach that is less likely to make different memory
loads depending on the value of b >> 63 and is also unlikely to be compiled
to a condition.
XTS mode is fully known as "xor-encrypt-xor with ciphertext-stealing".
This is the generalization of the XEX mode.
This implementation is limited to an 8-bits (1 byte) boundary, which
doesn't seem to be what was thought considering some test vectors [1].
This commit comes with tests, extracted from [1], and benchmarks.
Although, benchmarks aren't really nice here, as they work with a buffer
of a multiple of 16 bytes, which isn't a challenge for XTS compared to
XEX.
[1] http://csrc.nist.gov/groups/STM/cavp/documents/aes/XTSTestVectors.zip
As seen from the first benchmark run, AES-XEX was running pourly (even
slower than AES-CBC). This commit doubles the performances of the
current implementation.
