Improve multipart cipher tests: 2 blocks, CTR #62
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Some calls to psa_cipher_finish or psa_cipher_update append to a buffer. Several of these calls were not calculating the offset into the buffer or the remaining buffer size correctly. This did not lead to buffer overflows before because the buffer sizes were sufficiently large for our test inputs. This did not lead to incorrect output when the test was designed to append but actually wrote too early because all the existing test cases either have no output from finish (stream cipher) or have no output from update (CBC, with less than one block of input).
The output length can be equal to the input length. This wasn't noticed at runtime because we happened to only test with CBC with the first chunk being a partial block.
Test data obtained with Python+PyCrypto:
AES.new(key, AES.MODE_CBC, iv).encrypt(plaintext.decode('hex')).encode('hex')
Test data obtained with Python+PyCrypto:
AES.new(key, mode=AES.MODE_CTR, counter=Crypto.Util.Counter.new(128, initial_value=0x2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a)).encrypt(plaintext.decode('hex')).encode('hex')
In multipart cipher tests, test that each step of psa_cipher_update produces output of the expected length. The length is hard-coded in the test data since it depends on the mode. The length of the output of psa_cipher_finish is effectively tested because it's the total output length minus the length produced by the update steps.
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CI failure is FreeBSD timing test, a known-flaky test. |
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The only cipher multipart tests we had were for CBC with exactly one block. Add tests with CBC with two blocks and tests with CTR.