fscrypt: PAM login failure after update to bd2ca31

After updating to revision bd2ca31a8d92581582e4150de53eccef99a36b3c my previously working fscrypt setup started failing.

Steps:

1. Setup fscrypt (0.2.2.7.g141265f-1) + PAM unlocking using pam_fscrypt.so as described in https://github.com/google/fscrypt/issues/77#issuecomment-362490057
2. Logging in unlocks home and login succeeds (both console and GDM).
3. Update to fscrypt 0.2.3.2.gbd2ca31-1 or 0.2.3.0.ge131cec-1 (both tested).
4. Attempt to login results in a. GDM appears to succeed and then goes back to login screen (no desktop shown). b. Console redisplays login prompt, no shell prompt displayed.

Home directory is left in unlocked state after this, so pam_fscrypt.so is partially working. Removing all pam_fscrypt.so instances from /etc/pam.d/system-auth and /etc/pam.d/system-login results in successful login (if home directory is in unlocked state, which it is after at least one failed attempt).

Reverting to revision 141265f solves the issue and logins work again.

Non-encrypted logins do work even with pam_fscrypt.so enabled (my root home is not encrypted). Logs with debug option in all pam_fscrypt.so instances:

Look at pam_fscrypt[11273] for instance:

logs.txt

system-login.txt

system-auth.txt