Roll third_party/pexpect 509:533

third_party/pexpect/pxssh.py

 """This class extends pexpect.spawn to specialize setting up SSH connections.
 This adds methods for login, logout, and expecting the shell prompt.
 
-$Id: pxssh.py 487 2007-08-29 22:33:29Z noah $
+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 pexpect import *
 import pexpect
 import time
+import os
 
 __all__ = ['ExceptionPxssh', 'pxssh']
 
 # Exception classes used by this module.
 class ExceptionPxssh(ExceptionPexpect):
     """Raised for pxssh exceptions.
     """
 
 class pxssh (spawn):
 
     """This class extends pexpect.spawn to specialize setting up SSH
     connections. This adds methods for login, logout, and expecting the shell
     prompt. It does various tricky things to handle many situations in the SSH
     login process. For example, if the session is your first login, then pxssh
     automatically accepts the remote certificate; or if you have public key
     authentication setup then pxssh won't wait for the password prompt.
 
     pxssh uses the shell prompt to synchronize output from the remote host. In
     order to make this more robust it sets the shell prompt to something more
     unique than just $ or #. This should work on most Borne/Bash or Csh style
     shells.
 
     Example that runs a few commands on a remote server and prints the result::
-        
+
         import pxssh
         import getpass
-        try:                                                            
+        try:
             s = pxssh.pxssh()
             hostname = raw_input('hostname: ')
             username = raw_input('username: ')
             password = getpass.getpass('password: ')
             s.login (hostname, username, password)
             s.sendline ('uptime')  # run a command
             s.prompt()             # match the prompt
             print s.before         # print everything before the prompt.
             s.sendline ('ls -l')
             s.prompt()
@@ skipping 17 matching lines @@
 
             s = pxssh.pxssh()
             s.force_password = True
             hostname = raw_input('hostname: ')
             username = raw_input('username: ')
             password = getpass.getpass('password: ')
             s.login (hostname, username, password)
     """
 
     def __init__ (self, timeout=30, maxread=2000, searchwindowsize=None, logfile=None, cwd=None, env=None):
+
         spawn.__init__(self, None, timeout=timeout, maxread=maxread, searchwindowsize=searchwindowsize, logfile=logfile, cwd=cwd, env=env)
 
         self.name = '<pxssh>'
-        
-        #SUBTLE HACK ALERT! Note that the command to set the prompt uses a
+
+        #SUBTLE HACK ALERT! Note that the command that SETS the prompt uses a
         #slightly different string than the regular expression to match it. This
         #is because when you set the prompt the command will echo back, but we
         #don't want to match the echoed command. So if we make the set command
         #slightly different than the regex we eliminate the problem. To make the
         #set command different we add a backslash in front of $. The $ doesn't
         #need to be escaped, but it doesn't hurt and serves to make the set
         #prompt command different than the regex.
 
         # used to match the command-line prompt
         self.UNIQUE_PROMPT = "\[PEXPECT\][\$\#] "
         self.PROMPT = self.UNIQUE_PROMPT
 
         # used to set shell command-line prompt to UNIQUE_PROMPT.
         self.PROMPT_SET_SH = "PS1='[PEXPECT]\$ '"
         self.PROMPT_SET_CSH = "set prompt='[PEXPECT]\$ '"
-        self.SSH_OPTS = "-o'RSAAuthentication=no' -o 'PubkeyAuthentication=no'"
+        self.SSH_OPTS = ("-o'RSAAuthentication=no'"
+                + " -o 'PubkeyAuthentication=no'")
+# Disabling host key checking, makes you vulnerable to MITM attacks.
+#                + " -o 'StrictHostKeyChecking=no'"
+#                + " -o 'UserKnownHostsFile /dev/null' ")
         # Disabling X11 forwarding gets rid of the annoying SSH_ASKPASS from
         # displaying a GUI password dialog. I have not figured out how to
         # disable only SSH_ASKPASS without also disabling X11 forwarding.
         # Unsetting SSH_ASKPASS on the remote side doesn't disable it! Annoying!
         #self.SSH_OPTS = "-x -o'RSAAuthentication=no' -o 'PubkeyAuthentication=no'"
         self.force_password = False
-        self.auto_prompt_reset = True 
+        self.auto_prompt_reset = True
 
     def levenshtein_distance(self, a,b):
 
         """This calculates the Levenshtein distance between a and b.
         """
 
         n, m = len(a), len(b)
         if n > m:
             a,b = b,a
             n,m = m,n
         current = range(n+1)
         for i in range(1,m+1):
             previous, current = current, [i]+[0]*n
             for j in range(1,n+1):
                 add, delete = previous[j]+1, current[j-1]+1
                 change = previous[j-1]
                 if a[j-1] != b[i-1]:
                     change = change + 1
                 current[j] = min(add, delete, change)
         return current[n]
 
-    def synch_original_prompt (self):
+    def sync_original_prompt (self):
 
         """This attempts to find the prompt. Basically, press enter and record
         the response; press enter again and record the response; if the two
-        responses are similar then assume we are at the original prompt. """
+        responses are similar then assume we are at the original prompt. This
+        is a slow function. It can take over 10 seconds. """
 
         # All of these timing pace values are magic.
         # I came up with these based on what seemed reliable for
         # connecting to a heavily loaded machine I have.
+        self.sendline()
+        time.sleep(0.1)
         # If latency is worse than these values then this will fail.
 
-        self.read_nonblocking(size=10000,timeout=1) # GAS: Clear out the cache before getting the prompt
+        try:
+            # Clear the buffer before getting the prompt.
+            self.read_nonblocking(size=10000,timeout=1)
+        except TIMEOUT:
+            pass
         time.sleep(0.1)
         self.sendline()
         time.sleep(0.5)
         x = self.read_nonblocking(size=1000,timeout=1)
         time.sleep(0.1)
         self.sendline()
         time.sleep(0.5)
         a = self.read_nonblocking(size=1000,timeout=1)
         time.sleep(0.1)
         self.sendline()
         time.sleep(0.5)
         b = self.read_nonblocking(size=1000,timeout=1)
         ld = self.levenshtein_distance(a,b)
         len_a = len(a)
         if len_a == 0:
             return False
         if float(ld)/len_a < 0.4:
             return True
         return False
 
     ### TODO: This is getting messy and I'm pretty sure this isn't perfect.
     ### TODO: I need to draw a flow chart for this.
-    def login (self,server,username,password='',terminal_type='ansi',original_prompt=r"[#$]",login_timeout=10,port=None,auto_prompt_reset=True):
+    def login (self,server,username,password='',terminal_type='ansi',original_prompt=r"[#$]",login_timeout=10,port=None,auto_prompt_reset=True,ssh_key=None):
 
         """This logs the user into the given server. It uses the
         'original_prompt' to try to find the prompt right after login. When it
         finds the prompt it immediately tries to reset the prompt to something
         more easily matched. The default 'original_prompt' is very optimistic
         and is easily fooled. It's more reliable to try to match the original
         prompt as exactly as possible to prevent false matches by server
         strings such as the "Message Of The Day". On many systems you can
         disable the MOTD on the remote server by creating a zero-length file
         called "~/.hushlogin" on the remote server. If a prompt cannot be found
         then this will not necessarily cause the login to fail. In the case of
         a timeout when looking for the prompt we assume that the original
         prompt was so weird that we could not match it, so we use a few tricks
         to guess when we have reached the prompt. Then we hope for the best and
         blindly try to reset the prompt to something more unique. If that fails
         then login() raises an ExceptionPxssh exception.
-        
+
         In some situations it is not possible or desirable to reset the
         original prompt. In this case, set 'auto_prompt_reset' to False to
         inhibit setting the prompt to the UNIQUE_PROMPT. Remember that pxssh
         uses a unique prompt in the prompt() method. If the original prompt is
         not reset then this will disable the prompt() method unless you
         manually set the PROMPT attribute. """
 
         ssh_options = '-q'
         if self.force_password:
             ssh_options = ssh_options + ' ' + self.SSH_OPTS
         if port is not None:
             ssh_options = ssh_options + ' -p %s'%(str(port))
+        if ssh_key is not None:
+            try:
+                os.path.isfile(ssh_key)
+            except:
+                raise ExceptionPxssh ('private ssh key does not exist')
+            ssh_options = ssh_options + ' -i %s' % (ssh_key)
         cmd = "ssh %s -l %s %s" % (ssh_options, username, server)
 
         # This does not distinguish between a remote server 'password' prompt
         # and a local ssh 'passphrase' prompt (for unlocking a private key).
         spawn._spawn(self, cmd)
         i = self.expect(["(?i)are you sure you want to continue connecting", original_prompt, "(?i)(?:password)|(?:passphrase for key)", "(?i)permission denied", "(?i)terminal type", TIMEOUT, "(?i)connection closed by remote host"], timeout=login_timeout)
 
         # First phase
-        if i==0: 
+        if i==0:
             # New certificate -- always accept it.
             # This is what you get if SSH does not have the remote host's
             # public key stored in the 'known_hosts' cache.
             self.sendline("yes")
             i = self.expect(["(?i)are you sure you want to continue connecting", original_prompt, "(?i)(?:password)|(?:passphrase for key)", "(?i)permission denied", "(?i)terminal type", TIMEOUT])
         if i==2: # password or passphrase
             self.sendline(password)
             i = self.expect(["(?i)are you sure you want to continue connecting", original_prompt, "(?i)(?:password)|(?:passphrase for key)", "(?i)permission denied", "(?i)terminal type", TIMEOUT])
         if i==4:
             self.sendline(terminal_type)
             i = self.expect(["(?i)are you sure you want to continue connecting", original_prompt, "(?i)(?:password)|(?:passphrase for key)", "(?i)permission denied", "(?i)terminal type", TIMEOUT])
 
         # Second phase
         if i==0:
             # This is weird. This should not happen twice in a row.
             self.close()
             raise ExceptionPxssh ('Weird error. Got "are you sure" prompt twice.')
-        elif i==1: # can occur if you have a public key pair set to authenticate. 
+        elif i==1: # can occur if you have a public key pair set to authenticate.
             ### TODO: May NOT be OK if expect() got tricked and matched a false prompt.
             pass
         elif i==2: # password prompt again
             # For incorrect passwords, some ssh servers will
             # ask for the password again, others return 'denied' right away.
             # If we get the password prompt again then this means
-            # we didn't get the password right the first time. 
+            # we didn't get the password right the first time.
             self.close()
             raise ExceptionPxssh ('password refused')
         elif i==3: # permission denied -- password was bad.
             self.close()
             raise ExceptionPxssh ('permission denied')
         elif i==4: # terminal type again? WTF?
             self.close()
             raise ExceptionPxssh ('Weird error. Got "terminal type" prompt twice.')
         elif i==5: # Timeout
             #This is tricky... I presume that we are at the command-line prompt.
             #It may be that the shell prompt was so weird that we couldn't match
             #it. Or it may be that we couldn't log in for some other reason. I
             #can't be sure, but it's safe to guess that we did login because if
             #I presume wrong and we are not logged in then this should be caught
             #later when I try to set the shell prompt.
             pass
         elif i==6: # Connection closed by remote host
             self.close()
             raise ExceptionPxssh ('connection closed')
-        else: # Unexpected 
+        else: # Unexpected
             self.close()
             raise ExceptionPxssh ('unexpected login response')
-        if not self.synch_original_prompt():
+        if not self.sync_original_prompt():
             self.close()
             raise ExceptionPxssh ('could not synchronize with original prompt')
         # We appear to be in.
         # set shell prompt to something unique.
         if auto_prompt_reset:
             if not self.set_unique_prompt():
                 self.close()
                 raise ExceptionPxssh ('could not set shell prompt\n'+self.before)
         return True
 
     def logout (self):
 
         """This sends exit to the remote shell. If there are stopped jobs then
         this automatically sends exit twice. """
 
         self.sendline("exit")
         index = self.expect([EOF, "(?i)there are stopped jobs"])
         if index==1:
             self.sendline("exit")
             self.expect(EOF)
         self.close()
 
-    def prompt (self, timeout=20):
+    def prompt (self, timeout=-1):
 
         """This matches the shell prompt. This is little more than a short-cut
         to the expect() method. This returns True if the shell prompt was
-        matched. This returns False if there was a timeout. Note that if you
-        called login() with auto_prompt_reset set to False then you should have
-        manually set the PROMPT attribute to a regex pattern for matching the
-        prompt. """
+        matched. This returns False if a timeout was raised. Note that if you
+        called login() with auto_prompt_reset set to False then before calling
+        prompt() you must set the PROMPT attribute to a regex that prompt()
+        will use for matching the prompt. Calling prompt() will erase the
+        contents of the 'before' attribute even if no prompt is ever matched.
+        If timeout is not given or it is set to -1 then self.timeout is used.
+        """
 
+        if timeout == -1:
+            timeout = self.timeout
         i = self.expect([self.PROMPT, TIMEOUT], timeout=timeout)
         if i==1:
             return False
         return True
-        
+
     def set_unique_prompt (self):
 
         """This sets the remote prompt to something more unique than # or $.
         This makes it easier for the prompt() method to match the shell prompt
         unambiguously. This method is called automatically by the login()
         method, but you may want to call it manually if you somehow reset the
         shell prompt. For example, if you 'su' to a different user then you
         will need to manually reset the prompt. This sends shell commands to
         the remote host to set the prompt, so this assumes the remote host is
         ready to receive commands.
 
         Alternatively, you may use your own prompt pattern. Just set the PROMPT
         attribute to a regular expression that matches it. In this case you
         should call login() with auto_prompt_reset=False; then set the PROMPT
         attribute. After that the prompt() method will try to match your prompt
         pattern."""
 
         self.sendline ("unset PROMPT_COMMAND")
         self.sendline (self.PROMPT_SET_SH) # sh-style
         i = self.expect ([TIMEOUT, self.PROMPT], timeout=10)
         if i == 0: # csh-style
             self.sendline (self.PROMPT_SET_CSH)
             i = self.expect ([TIMEOUT, self.PROMPT], timeout=10)
             if i == 0:
                 return False
         return True
 
 # vi:ts=4:sw=4:expandtab:ft=python: