Automate SSH without using public key authentication or expect(1)

Question

Is there a way to pass a password to ssh automatically. I would like to automatically ssh to a server without using public key authentication or expect scripts, by somehow getting ssh to read the password from stdin or a file.

The reason it has to be that way is that I would like to backup my files to a server using rsync/ssh running as a cron job. This server mounts my home directory after it authenticates me, so using public key authentication does not work since ~/.ssh isn't available until after the login is successful. expect(1) is out of the question because I would like to run it as a cron job, and since cron jobs don't run under a terminal the combination of expect/ssh just doesn't work. I do not have root access to that server, and it would be difficult to get the admins to make any changes to the way things work there.

Answer 1

expect is out of the question because I would like to run it as a cron job, and since cron jobs don't run under a terminal the combination of expect/ssh just doesn't work

You can run expect scripts from cron, at least you can with expect libraries like "pexpect" for Python. I just tested this to confirm, running a pexpect scp/ssh script from cron and I was able to successfully scp a file from a Python script running in cron.

Example code:

#!/usr/bin/python

import pexpect

FILE="/path/to/file"
REMOTE_FILE=""
USER="user"
HOST="example.com"
PASS="mypass"
COMMAND="scp -oPubKeyAuthentication=no %s %s@%s:%s" % (FILE, USER, HOST, REMOTE_FILE)

child = pexpect.spawn(COMMAND)
child.expect('password:')
child.sendline(PASS)
child.expect(pexpect.EOF)
print child.before

Answer 2

Use sshpass.

For example, when password is in password.txt file:

sshpass -fpassword.txt ssh username@hostname

(taken from the answer to a similar question)