passh

NOTE: The pty related code is stolen from the APUE book.

compile

$ cc -o passh passh.c
$ cp -v passh /usr/bin/
$ passh -h

usage

Usage: passh [OPTION]... COMMAND...

  -c <N>          Send at most <N> passwords (0 means infinite. Default: 0)
  -C              Exit if prompted for the <N+1>th password
  -h              Help
  -i              Case insensitive for password prompt matching
  -n              Nohup the child (e.g. used for `ssh -f')
  -p <password>   The password (Default: `password')
  -p env:<var>    Read password from env var
  -p file:<file>  Read password from file
  -P <prompt>     Regexp (BRE) for the password prompt
                  (Default: `[Pp]assword: \{0,1\}$')
  -l <file>       Save data written to the pty
  -L <file>       Save data read from the pty
  -t <timeout>    Timeout waiting for next password prompt
                  (0 means no timeout. Default: 0)
  -T              Exit if timed out waiting for password prompt
  -y              Auto answer `(yes/no)?' questions

Report bugs to Clark Wang <dearvoid@gmail.com>

supported platforms

Tested on:

• OpenWRT 15.05.1, ramips/mt7620 (on Newifi Mini, or Lenovo Y1 v1)
• Debian Linux 8, x86_64 (Jessie)
• macOS 10.12 (Sierra)
• Cygwin, x86_64 (on Windows 7)
• FreeBSD 11.1, x86_64
• AIX 7.2, ppc64le (added in issue #7)

why i wrote passh

1. I got a Newifi Mini router and installed OpenWRT on it. I want the router to be my SOCKS proxy so I run ssh -D 8888 user@host automatically at boot time but the SSH server only supports password auth. On Linux I would use Expect to automate ssh but OpenWRT does not install Expect by default and my router does not have enough storage for the extra Tcl and Expect packages.

2. Then I tried sshpass but sshpass seems more like a nice hack and it's broken by design. See following example on a Linux system:

    $ tty
    /dev/pts/18                                      // now we're on pts/18
    $ sshpass bash --norc
    bash: cannot set terminal process group (-1): Inappropriate ioctl for device
    bash: no job control in this shell
    bash-4.4# tty
    /dev/pts/18                                      // the bash's stdin is also connected to pts/18
    bash-4.4# ps p $$
       PID TTY      STAT   TIME COMMAND
     37151 pts/36   Ss+    0:00 bash --norc          // but the controlling terminal is pts/36
    bash-4.4# ps t pts/36
       PID TTY      STAT   TIME COMMAND
     37151 pts/36   Ss+    0:00 bash --norc
     37154 pts/36   R+     0:00 ps t pts/36
    bash-4.4#
   

   Now let's try passh:

    $ tty
    /dev/pts/18                                      // now we're on pts/18
    $ passh bash --norc
    bash-4.4# tty
    /dev/pts/36                                      // the bash's stdin is connected to the new pts/36
    bash-4.4# ps p $$
       PID TTY      STAT   TIME COMMAND
     37159 pts/36   Ss     0:00 bash --norc          // pts/36 is its controlling terminal
    bash-4.4# ps t pts/36
       PID TTY      STAT   TIME COMMAND
     37159 pts/36   Ss     0:00 bash --norc
     37162 pts/36   R+     0:00 ps t pts/36
    bash-4.4#
   

   See sshpass-broken.md for more sshpass is broken examples.

auto answer questions

You can use passh for more than just inputting the passwords. For example, you could use this to both enter the password and answer yes to the question Proceed with propagating updates with the unison bidirecional sync tool:

1. passh -P 'Proceed with propagating updates' -p y passh -P '[Pp]assword: \{0,1\}$' -p password unison ...

unison has the builtin option called -batch to answer yes to this question Proceed with propagating updates, however that option also implies to ignore conflicts and fail silently. Then, using passh to answer y to the input question Proceed with propagating updates allows you to automate the process when there is no conflicts, because when there are conflicts the first question would be to chose which file should be synced.

examples

1. sshpass is better in its own way.

   For example, you can use rsync + sshpass like this:

    $ rsync -e 'sshpass -p password ssh' file user@host:/dir
   

   But with passh you have to:

    $ passh -p password rsync -e ssh file user@host:/dir
   

   Another example, with sshpass you can:

    $ echo date | sshpass -p password ssh user@host bash
   

   But with passh you have to:

    $ passh -p password bash -c 'echo date | ssh user@host bash'
   

2. Start SSH SOCKS proxy in background

    $ passh -n -p password ssh -D 7070 -N -n -f user@host
   

   Here -n is required or ssh -f would not work. (I believe the bug is in OpenSSH though.)

3. Login to a remote server

    $ passh -p password ssh user@host
   

4. Run a command on remote server

    $ passh -p password ssh user@host date
   

5. Share a remote server with others and want to use your local bashrc?

    $ passh -p password scp /local/bashrc user@host:/tmp/tmp.cAE8Kv
    $ passh -p password ssh -t user@host bash --rc /tmp/tmp.cAE8Kv
   

6. Or just for fun

    $ passh bash
    $ passh vim