I recently decided to use paramiko to develop a remote command execution tool. <\/p>\n
It was very easy to setup initially and ran much faster than my existing pexpect implementation but it had a problem with sudo commands because they required the password to be provided as input. <\/p>\n
I solved the problem by using a pseudo-terminal and by creating my own ChannelFile objects for stdin and stdout\/stderr. The solution should be general enough to handle any case that requires simple input but it is not as flexible as pexpect. I hope that you find it useful.
\n<\/p>\n
This is similar to the older version below but it handles more than 64KiB by eliminating the stdout buffer, the stdin buffer and using recv polling. It even does a silly check for input. That check could be expanded to make it behave more like pexpect but that is for another day.
\n[crayon lang=”python” toolbar=”always” title=”remote_exec”]
\n#!\/usr\/bin\/env python
\n”’
\nThis class allows you to run commands on a remote host and provide
\ninput if necessary.<\/p>\n
VERSION 1.2
\n”’
\nimport paramiko
\nimport logging
\nimport socket
\nimport time
\nimport datetime<\/p>\n
# ================================================================
\n# class MySSH
\n# ================================================================
\nclass MySSH:
\n ”’
\n Create an SSH connection to a server and execute commands.
\n Here is a typical usage:<\/p>\n
ssh = MySSH()
\n ssh.connect(‘host’, ‘user’, ‘password’, port=22)
\n if ssh.connected() is False:
\n sys.exit(‘Connection failed’)<\/p>\n
# Run a command that does not require input.
\n status, output = ssh.run(‘uname -a’)
\n print ‘status = %d’ % (status)
\n print ‘output (%d):’ % (len(output))
\n print ‘%s’ % (output)<\/p>\n
# Run a command that does requires input.
\n status, output = ssh.run(‘sudo uname -a’, ‘sudo-password’)
\n print ‘status = %d’ % (status)
\n print ‘output (%d):’ % (len(output))
\n print ‘%s’ % (output)
\n ”’
\n def __init__(self, compress=True, verbose=False):
\n ”’
\n Setup the initial verbosity level and the logger.<\/p>\n
@param compress Enable\/disable compression.
\n @param verbose Enable\/disable verbose messages.
\n ”’
\n self.ssh = None
\n self.transport = None
\n self.compress = compress
\n self.bufsize = 65536<\/p>\n
# Setup the logger
\n self.logger = logging.getLogger(‘MySSH’)
\n self.set_verbosity(verbose)<\/p>\n
fmt = ‘%(asctime)s MySSH:%(funcName)s:%(lineno)d %(message)s’
\n format = logging.Formatter(fmt)
\n handler = logging.StreamHandler()
\n handler.setFormatter(format)
\n self.logger.addHandler(handler)
\n self.info = self.logger.info<\/p>\n
def __del__(self):
\n if self.transport is not None:
\n self.transport.close()
\n self.transport = None<\/p>\n
def connect(self, hostname, username, password, port=22):
\n ”’
\n Connect to the host.<\/p>\n
@param hostname The hostname.
\n @param username The username.
\n @param password The password.
\n @param port The port (default=22).<\/p>\n
@returns True if the connection succeeded or false otherwise.
\n ”’
\n self.info(‘connecting %s@%s:%d’ % (username, hostname, port))
\n self.hostname = hostname
\n self.username = username
\n self.port = port
\n self.ssh = paramiko.SSHClient()
\n self.ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
\n try:
\n self.ssh.connect(hostname=hostname,
\n port=port,
\n username=username,
\n password=password)
\n self.transport = self.ssh.get_transport()
\n self.transport.use_compression(self.compress)
\n self.info(‘succeeded: %s@%s:%d’ % (username,
\n hostname,
\n port))
\n except socket.error as e:
\n self.transport = None
\n self.info(‘failed: %s@%s:%d: %s’ % (username,
\n hostname,
\n port,
\n str(e)))
\n except paramiko.BadAuthenticationType as e:
\n self.transport = None
\n self.info(‘failed: %s@%s:%d: %s’ % (username,
\n hostname,
\n port,
\n str(e)))<\/p>\n
return self.transport is not None<\/p>\n
def run(self, cmd, input_data=None, timeout=10):
\n ”’
\n Run a command with optional input data.<\/p>\n
Here is an example that shows how to run commands with no input:<\/p>\n
ssh = MySSH()
\n ssh.connect(‘host’, ‘user’, ‘password’)
\n status, output = ssh.run(‘uname -a’)
\n status, output = ssh.run(‘uptime’)<\/p>\n
Here is an example that shows how to run commands that require input:<\/p>\n
ssh = MySSH() @param cmd The command to run. if self.transport is None: # Fix the input data. # Initialize the session. def connected(self): @returns True if connected or false otherwise. def set_verbosity(self, verbose): @param verbose Enable\/disable verbose messages. def _run_fix_input_data(self, input_data): @param input_data The input data (default is None). def _run_send_input(self, session, stdin, input_data): @param session The session. def _run_poll(self, session, timeout, input_data): @param session The session. # Poll until completion or timeout if session.send_ready(): self.info(‘polling loop ended’) self.info(‘polling finished – %d output bytes’ % (len(output))) return output<\/p>\n # ================================================================ # Access variables. # Create the SSH connection def run_cmd(cmd, indata=None): @param cmd The command to execute. run_cmd(‘uname -a’) This version will not handle more than 64KiB of output. I am not sure why. # ================================================================ ssh = MySSH() # Run a command that does not require input. # Run a command that does requires input. @param compress Enable\/disable compression. # Setup the logger fmt = ‘%(asctime)s MySSH:%(funcName)s:%(lineno)d %(message)s’ def __del__(self): def connect(self, hostname, username, password, port=22): @param hostname The hostname. @returns True if the connection succeeded or false otherwise. return self.transport is not None<\/p>\n def run(self, cmd, input_data=None, timeout=10): Here is an example that shows how to run commands with no input:<\/p>\n ssh = MySSH() Here is an example that shows how to run commands that require input:<\/p>\n ssh = MySSH() @param cmd The command to run. if self.transport is None: # Fix the input data. # Initialize the session. self._run_send_input(stdout, stdin, input_data) def connected(self): @returns True if connected or false otherwise. def set_verbosity(self, verbose): @param verbose Enable\/disable verbose messages. def _run_fix_input_data(self, input_data): @param input_data The input data (default is None). def _run_send_input(self, stdout, stdin, input_data): @param stdout The stdout stream for the session. def _run_poll(self, stdout, timeout, input_data): @param timeout The timeout in seconds. # Poll until completion or timeout I recently decided to use paramiko to develop a remote command execution tool. It was very easy to setup initially and ran much faster than my existing pexpect implementation but it had a problem with sudo commands because they required the password to be provided as input. I solved the problem by using a pseudo-terminal … Continue reading Remote command execution in python using paramiko that supports arbitrary input<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0},"categories":[5,7,16],"tags":[],"_links":{"self":[{"href":"https:\/\/joelinoff.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/905"}],"collection":[{"href":"https:\/\/joelinoff.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/joelinoff.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/joelinoff.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/joelinoff.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=905"}],"version-history":[{"count":12,"href":"https:\/\/joelinoff.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/905\/revisions"}],"predecessor-version":[{"id":996,"href":"https:\/\/joelinoff.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/905\/revisions\/996"}],"wp:attachment":[{"href":"https:\/\/joelinoff.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=905"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/joelinoff.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=905"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/joelinoff.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=905"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\n ssh.connect(‘host’, ‘user’, ‘password’)
\n status, output = ssh.run(‘sudo uname -a’, ‘
\n @param input_data The input data (default is None).
\n @param timeout The timeout in seconds (default is 10 seconds).
\n @returns The status and the output (stdout and stderr combined).
\n ”’
\n self.info(‘running command: (%d) %s’ % (timeout, cmd))<\/p>\n
\n self.info(‘no connection to %s@%s:%s’ % (str(self.username),
\n str(self.hostname),
\n str(self.port)))
\n return -1, ‘ERROR: connection not established\\n’<\/p>\n
\n input_data = self._run_fix_input_data(input_data)<\/p>\n
\n self.info(‘initializing the session’)
\n session = self.transport.open_session()
\n session.set_combine_stderr(True)
\n session.get_pty()
\n session.exec_command(cmd)
\n output = self._run_poll(session, timeout, input_data)
\n status = session.recv_exit_status()
\n self.info(‘output size %d’ % (len(output)))
\n self.info(‘status %d’ % (status))
\n return status, output<\/p>\n
\n ”’
\n Am I connected to a host?<\/p>\n
\n ”’
\n return self.transport is not None<\/p>\n
\n ”’
\n Turn verbose messages on or off.<\/p>\n
\n ”’
\n if verbose > 0:
\n self.logger.setLevel(logging.INFO)
\n else:
\n self.logger.setLevel(logging.ERROR)<\/p>\n
\n ”’
\n Fix the input data supplied by the user for a command.<\/p>\n
\n @returns the fixed input data.
\n ”’
\n if input_data is not None:
\n if len(input_data) > 0:
\n if ‘\\\\n’ in input_data:
\n # Convert \\n in the input into new lines.
\n lines = input_data.split(‘\\\\n’)
\n input_data = ‘\\n’.join(lines)
\n return input_data.split(‘\\n’)
\n return []<\/p>\n
\n ”’
\n Send the input data.<\/p>\n
\n @param stdin The stdin stream for the session.
\n @param input_data The input data (default is None).
\n ”’
\n if input_data is not None:
\n self.info(‘session.exit_status_ready() %s’ % str(session.exit_status_ready()))
\n self.info(‘stdin.channel.closed %s’ % str(stdin.channel.closed))
\n if stdin.channel.closed is False:
\n self.info(‘sending input data’)
\n stdin.write(input_data)<\/p>\n
\n ”’
\n Poll until the command completes.<\/p>\n
\n @param timeout The timeout in seconds.
\n @param input_data The input data.
\n @returns the output
\n ”’
\n interval = 0.1
\n maxseconds = timeout
\n maxcount = maxseconds \/ interval<\/p>\n
\n # Note that we cannot directly use the stdout file descriptor
\n # because it stalls at 64K bytes (65536).
\n input_idx = 0
\n timeout_flag = False
\n self.info(‘polling (%d, %d)’ % (maxseconds, maxcount))
\n start = datetime.datetime.now()
\n start_secs = time.mktime(start.timetuple())
\n output = ”
\n session.setblocking(0)
\n while True:
\n if session.recv_ready():
\n data = session.recv(self.bufsize)
\n output += data
\n self.info(‘read %d bytes, total %d’ % (len(data), len(output)))<\/p>\n
\n # We received a potential prompt.
\n # In the future this could be made to work more like
\n # pexpect with pattern matching.
\n if input_idx < len(input_data):\n data = input_data[input_idx] + '\\n'\n input_idx += 1\n self.info('sending input data %d' % (len(data)))\n session.send(data)\n\n self.info('session.exit_status_ready() = %s' % (str(session.exit_status_ready())))\n if session.exit_status_ready():\n break\n\n # Timeout check\n now = datetime.datetime.now()\n now_secs = time.mktime(now.timetuple()) \n et_secs = now_secs - start_secs\n self.info('timeout check %d %d' % (et_secs, maxseconds))\n if et_secs > maxseconds:
\n self.info(‘polling finished – timeout’)
\n timeout_flag = True
\n break
\n time.sleep(0.200)<\/p>\n
\n if session.recv_ready():
\n data = session.recv(self.bufsize)
\n output += data
\n self.info(‘read %d bytes, total %d’ % (len(data), len(output)))<\/p>\n
\n if timeout_flag:
\n self.info(‘appending timeout message’)
\n output += ‘\\nERROR: timeout after %d seconds\\n’ % (timeout)
\n session.close()<\/p>\n
\n# MAIN
\n# ================================================================
\nif __name__ == ‘__main__’:
\n import sys<\/p>\n
\n hostname = ‘hostname’
\n port = 22
\n username = ‘username’
\n password = ‘password’
\n sudo_password = password # assume that it is the same password<\/p>\n
\n ssh = MySSH()
\n ssh.set_verbosity(False)
\n ssh.connect(hostname=hostname,
\n username=username,
\n password=password,
\n port=port)
\n if ssh.connected() is False:
\n print ‘ERROR: connection failed.’
\n sys.exit(1)<\/p>\n
\n ”’
\n Run a command with optional input.<\/p>\n
\n @param indata The input data.
\n @returns The command exit status and output.
\n Stdout and stderr are combined.
\n ”’
\n print
\n print ‘=’ * 64
\n print ‘command: %s’ % (cmd)
\n status, output = ssh.run(cmd, indata)
\n print ‘status : %d’ % (status)
\n print ‘output : %d bytes’ % (len(output))
\n print ‘=’ * 64
\n print ‘%s’ % (output)<\/p>\n
\n run_cmd(‘sudo ls -ltrh \/var\/log | tail’, sudo_password) # sudo command
\n[\/crayon]<\/p>\nOlder Version<\/h1>\n
\n[crayon lang=”python” toolbar=”always” title=”old_remote_exec”]
\n#!\/usr\/bin\/env python
\n”’
\nThis class allows you to run commands on a remote host and provide
\ninput if necessary.
\n”’
\nimport paramiko
\nimport logging
\nimport socket
\nimport time<\/p>\n
\n# class MySSH
\n# ================================================================
\nclass MySSH:
\n ”’
\n Create an SSH connection to a server and execute commands.
\n Here is a typical usage:<\/p>\n
\n ssh.connect(‘host’, ‘user’, ‘password’, port=22)
\n if ssh.connected() is False:
\n sys.exit(‘Connection failed’)<\/p>\n
\n status, output = ssh.run(‘uname -a’)
\n print ‘status = %d’ % (status)
\n print ‘output (%d):’ % (len(output))
\n print ‘%s’ % (output)<\/p>\n
\n status, output = ssh.run(‘sudo uname -a’, ‘sudo-password’)
\n print ‘status = %d’ % (status)
\n print ‘output (%d):’ % (len(output))
\n print ‘%s’ % (output)
\n ”’
\n def __init__(self, compress=True, verbose=False):
\n ”’
\n Setup the initial verbosity level and the logger.<\/p>\n
\n @param verbose Enable\/disable verbose messages.
\n ”’
\n self.ssh = None
\n self.transport = None
\n self.compress = compress<\/p>\n
\n self.logger = logging.getLogger(‘MySSH’)
\n self.set_verbosity(verbose)<\/p>\n
\n format = logging.Formatter(fmt)
\n handler = logging.StreamHandler()
\n handler.setFormatter(format)
\n self.logger.addHandler(handler)
\n self.info = self.logger.info<\/p>\n
\n if self.transport is not None:
\n self.transport.close()
\n self.transport = None<\/p>\n
\n ”’
\n Connect to the host.<\/p>\n
\n @param username The username.
\n @param password The password.
\n @param port The port (default=22).<\/p>\n
\n ”’
\n self.info(‘connecting %s@%s:%d’ % (username, hostname, port))
\n self.hostname = hostname
\n self.username = username
\n self.port = port
\n self.ssh = paramiko.SSHClient()
\n self.ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
\n try:
\n self.ssh.connect(hostname=hostname,
\n port=port,
\n username=username,
\n password=password)
\n self.transport = self.ssh.get_transport()
\n self.transport.use_compression(self.compress)
\n self.info(‘succeeded: %s@%s:%d’ % (username,
\n hostname,
\n port))
\n except socket.error:
\n self.transport = None
\n self.info(‘failed: %s@%s:%d: %s’ % (username,
\n hostname,
\n port,
\n str(e)))
\n except paramiko.BadAuthenticationType as e:
\n self.transport = None
\n self.info(‘failed: %s@%s:%d: %s’ % (username,
\n hostname,
\n port,
\n str(e)))<\/p>\n
\n ”’
\n Run a command with optional input data.<\/p>\n
\n ssh.connect(‘host’, ‘user’, ‘password’)
\n status, output = ssh.run(‘uname -a’)
\n status, output = ssh.run(‘uptime’)<\/p>\n
\n ssh.connect(‘host’, ‘user’, ‘password’)
\n status, output = ssh.run(‘sudo uname -a’, ‘
\n @param input_data The input data (default is None).
\n @param timeout The timeout in seconds (default is 10 seconds).
\n @returns The status and the output (stdout and stderr combined).
\n ”’
\n self.info(‘running command: (%d) %s’ % (timeout, cmd))<\/p>\n
\n self.info(‘no connection to %s@%s:%s’ % (str(self.username),
\n str(self.hostname),
\n str(self.port)))
\n return -1, ‘ERROR: connection not established\\n’<\/p>\n
\n input_data = self._run_fix_input_data(input_data)<\/p>\n
\n self.info(‘initializing the session’)
\n session = self.transport.open_session()
\n session.set_combine_stderr(True)
\n session.get_pty()
\n session.exec_command(cmd)
\n stdin = session.makefile(‘wb’, -1)
\n stdout = session.makefile(‘rb’, -1)<\/p>\n
\n output = self._run_poll(stdout, timeout, input_data)
\n status = stdout.channel.recv_exit_status()
\n self.info(‘output size %d’ % (len(output)))
\n self.info(‘status %d’ % (status))
\n return status, output<\/p>\n
\n ”’
\n Am I connected to a host?<\/p>\n
\n ”’
\n return self.transport is not None<\/p>\n
\n ”’
\n Turn verbose messages on or off.<\/p>\n
\n ”’
\n if verbose is True:
\n self.logger.setLevel(logging.INFO)
\n else:
\n self.logger.setLevel(logging.ERROR)<\/p>\n
\n ”’
\n Fix the input data supplied by the user for a command.<\/p>\n
\n @returns the fixed input data.
\n ”’
\n if input_data is not None:
\n if len(input_data) > 0:
\n if ‘\\\\n’ in input_data:
\n # Convert \\n in the input into new lines.
\n lines = input_data.split(‘\\\\n’)
\n input_data = ‘\\n’.join(lines)
\n if input_data[-1] != ‘\\n’:
\n input_data += ‘\\n’
\n return input_data<\/p>\n
\n ”’
\n Send the input data.<\/p>\n
\n @param stdin The stdin stream for the session.
\n @param input_data The input data (default is None).
\n ”’
\n if stdout.channel.closed is False:
\n if input_data is not None:
\n self.info(‘sending input data’)
\n stdin.write(input_data)<\/p>\n
\n ”’
\n Poll until the command completes.<\/p>\n
\n @param input_data The input data.
\n @returns the output
\n ”’
\n interval = 0.1
\n maxseconds = timeout
\n maxcount = maxseconds \/ interval<\/p>\n
\n self.info(‘polling (%d, %d)’ % (maxseconds, maxcount))
\n count = 0
\n while stdout.channel.closed is False and count <= maxcount:\n count += 1\n time.sleep(interval)\n\n # Polling finished.\n if stdout.channel.closed is False:\n # Some sort of error occurred, assume a timeout.\n self.info('polling finished - timeout')\n stdout.channel.close()\n output = stdout.read()\n output += '\\nERROR: timeout after %d seconds\\n' % (timeout)\n else:\n output = stdout.read()\n self.info('polling finished - %d output bytes' % (len(output)))\n\n if input_data is not None:\n # Strip out the input data.\n output = output[len(input_data):]\n self.info('stripped %d input bytes' % (len(input_data)))\n\n return output\n\n\n# ================================================================\n# MAIN\n# ================================================================\nif __name__ == '__main__':\n import sys\n\n # Access variables.\n hostname = 'hostname'\n port = 22\n username = 'username'\n password = 'password'\n sudo_password = password # assume that it is the same password\n\n # Create the SSH connection\n ssh = MySSH()\n ssh.set_verbosity(False)\n ssh.connect(hostname=hostname,\n username=username,\n password=password,\n port=port)\n if ssh.connected() is False:\n print 'ERROR: connection failed.'\n sys.exit(1)\n\n def run_cmd(cmd, indata=None):\n '''\n Run a command with optional input.\n\n @param cmd The command to execute.\n @param indata The input data.\n @returns The command exit status and output.\n Stdout and stderr are combined.\n '''\n print\n print '=' * 64\n print 'command: %s' % (cmd)\n status, output = ssh.run(cmd, indata)\n print 'status : %d' % (status)\n print 'output : %d bytes' % (len(output))\n print '=' * 64\n print '%s' % (output)\n\n run_cmd('uname -a')\n run_cmd('sudo ls -ltrh \/var\/log | tail', sudo_password) # sudo command\n[\/crayon]\n\n<\/p>\n","protected":false},"excerpt":{"rendered":"