Two bugs found via the weston journal (issue #92):
1. MD5 rotation index used (j>>2 & 3) for the round number, which
cycles every 4 steps instead of every 16. Verified against RFC 1321
test vectors: md5("") was 7a1dce5b... instead of d41d8cd9... — the
derived AES key was wrong, so the server decrypted the credentials
to garbage. Fixed to j>>4.
2. weston's vnc_handle_auth calls getpwnam(username) and requires
pw_uid == weston's own uid before PAM is consulted. We sent an empty
username, which fails outright ("VNC: wrong user"). weston runs as
root, so send username "root"; the empty password still passes via
pam_permit.so on the weston-remote-access service.
Fixes#92
c10b4e26ef