tree c19bede45d7474d319e193c6f3b2f1c1bc7d754a
parent 5f387e38fc406d6e341248865df61dd9d957171f
author Adam Langley <agl@google.com> 1432236301 -0700
committer Adam Langley <agl@google.com> 1432240057 -0700

Fix test used for not-in-place CBC mode.

With NO_ASM defined, the recent AEAD changes broke the tests. The
problem is that the generic CBC mode code tests whether in != out and
omits to save the IV, assuming that it'll be able to read the old
ciphertext block.

However, consider the case where out = in - 16:

    1       2      3       4
|-------|-------|------|-------|
    ^       ^
    |       |
   out     in

First time around, 1 = decrypt(2) ^ iv and everything is fine, because
the IV was preconfigured. However, the next iteration of the loop sets
2 = decrypt(3) and tries to XOR it with the contents of the previous
ciphertext block… from 2.

Change-Id: Ibabff430704fad246de132b4d6d514f6a0362734