I ran across this cryptic error message in an SSH log file today:
Feb 7 03:33:21 hostname sshd: error: buffer_get_ret: trying to get more bytes 4 than in buffer 0 Feb 7 03:33:21 hostname sshd: fatal: buffer_get_int: buffer error
The problem is actually a corrupt line in a users ~/.ssh/authorized_keys file. This user had copy/pasted a new key into his authorized_keys file and it had a newline after the ssh-rsa. Strangely enough, people were still able to authenticate if their key was above the corrupted line. Users whose key was listed below the corrupt line were not able to log in.