Introduce CKF_MULTI_MESSAGE flag

[Jakuje]

Description

Fixes: #170

If you think some more tests will be needed, please let me know. I think we support this only for AES-GCM/CCM for now.

Checklist

• [ ] Test suite updated with functionality tests
• [ ] Test suite updated with negative tests
• [ ] Documentation was updated
• [ ] This is not a code change

Reviewer's checklist:

• Any issues marked for closing are fully addressed
• There is a test suite reasonably covering new functionality or modifications
• This feature/change has adequate documentation added
• A changelog entry is added if the change is significant
• Code conform to coding style that today cannot yet be enforced via the check style test
• Commits have short titles and sensible text

[simo5]

Should we add a test that ensure this works as expected ?
Ie the GCM mechanism has the flag set and trying to use the Message function with another cipher fails because of lack of the flag ?

[Jakuje]

Should we add a test that ensure this works as expected ? Ie the GCM mechanism has the flag set and trying to use the Message function with another cipher fails because of lack of the flag ?

I was thinking what would be a usable tests, but for now only AES-GCM and AES-CCM works with the message API and both of them have the MULTI_MESSAGE flag. So the only thing I can test is to call init with mechanism that does not have message API (AES-CRT). But this fails already at fn_message_encrypt_init() on the missing CKF_MESSAGE_ENCRYPT flag. Do you have some other test in you mind that could excercise this code path? Or do you know from top of you head if there is some mechanism that does not support the MULTI_MESSAGE that we can implement/wire for the test?

[simo5]

Should we add a test that ensure this works as expected ? Ie the GCM mechanism has the flag set and trying to use the Message function with another cipher fails because of lack of the flag ?

I was thinking what would be a usable tests, but for now only AES-GCM and AES-CCM works with the message API and both of them have the MULTI_MESSAGE flag. So the only thing I can test is to call init with mechanism that does not have message API (AES-CRT). But this fails already at fn_message_encrypt_init() on the missing CKF_MESSAGE_ENCRYPT flag. Do you have some other test in you mind that could excercise this code path? Or do you know from top of you head if there is some mechanism that does not support the MULTI_MESSAGE that we can implement/wire for the test?

Uhmmm I had not considered that ... indeed it seem like we do not have a way to test this in a meannigful way.
In that case I'll just merge and we'll add a test, if we figure out how, in the future.