Add third_party/pexpect

third_party/pexpect/examples/ssh_tunnel.py

Index: third_party/pexpect/examples/ssh_tunnel.py
diff --git a/third_party/pexpect/examples/ssh_tunnel.py b/third_party/pexpect/examples/ssh_tunnel.py
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+#!/usr/bin/env python
+
+'''This starts an SSH tunnel to a given host. If the SSH process ever dies then
+this script will detect that and restart it. I use this under Cygwin to keep
+open encrypted tunnels to port 25 (SMTP), port 143 (IMAP4), and port 110
+(POP3). I set my mail client to talk to localhost and I keep this script
+running in the background.
+
+Note that this is a rather stupid script at the moment because it just looks to
+see if any ssh process is running. It should really make sure that our specific
+ssh process is running. The problem is that ssh is missing a very useful
+feature. It has no way to report the process id of the background daemon that
+it creates with the -f command. This would be a really useful script if I could
+figure a way around this problem.
+
+PEXPECT LICENSE
+
+    This license is approved by the OSI and FSF as GPL-compatible.
+        http://opensource.org/licenses/isc-license.txt
+
+    Copyright (c) 2012, Noah Spurrier <noah@noah.org>
+    PERMISSION TO USE, COPY, MODIFY, AND/OR DISTRIBUTE THIS SOFTWARE FOR ANY
+    PURPOSE WITH OR WITHOUT FEE IS HEREBY GRANTED, PROVIDED THAT THE ABOVE
+    COPYRIGHT NOTICE AND THIS PERMISSION NOTICE APPEAR IN ALL COPIES.
+    THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+    MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+'''
+
+from __future__ import print_function
+
+from __future__ import absolute_import
+
+import pexpect
+import getpass
+import time
+
+
+try:
+    raw_input
+except NameError:
+    raw_input = input
+
+
+# SMTP:25 IMAP4:143 POP3:110
+tunnel_command = 'ssh -C -N -f -L 25:127.0.0.1:25 -L 143:127.0.0.1:143 -L 110:127.0.0.1:110 %(user)@%(host)'
+host = raw_input('Hostname: ')
+user = raw_input('Username: ')
+X = getpass.getpass('Password: ')
+
+def get_process_info ():
+
+    # This seems to work on both Linux and BSD, but should otherwise be considered highly UNportable.
+
+    ps = pexpect.run ('ps ax -O ppid')
+    pass
+
+def start_tunnel ():
+
+    try:
+        ssh_tunnel = pexpect.spawn (tunnel_command % globals())
+        ssh_tunnel.expect ('password:')
+        time.sleep (0.1)
+        ssh_tunnel.sendline (X)
+        time.sleep (60) # Cygwin is slow to update process status.
+        ssh_tunnel.expect (pexpect.EOF)
+
+    except Exception as e:
+        print(str(e))
+
+def main ():
+
+    while True:
+        ps = pexpect.spawn ('ps')
+        time.sleep (1)
+        index = ps.expect (['/usr/bin/ssh', pexpect.EOF, pexpect.TIMEOUT])
+        if index == 2:
+            print('TIMEOUT in ps command...')
+            print(str(ps))
+            time.sleep (13)
+        if index == 1:
+            print(time.asctime(), end=' ')
+            print('restarting tunnel')
+            start_tunnel ()
+            time.sleep (11)
+            print('tunnel OK')
+        else:
+            # print 'tunnel OK'
+            time.sleep (7)
+
+if __name__ == '__main__':
+
+    main ()
+
+# This was for older SSH versions that didn't have -f option
+#tunnel_command = 'ssh -C -n -L 25:%(host)s:25 -L 110:%(host)s:110 %(user)s@%(host)s -f nothing.sh'
+#nothing_script = '''#!/bin/sh
+#while true; do sleep 53; done
+#'''
+