pexpect应用及建立ssh信任关系小记

1. pexpect

安装好pexpect模块后，按照demo sshls.py改造了自己的lib封装，虽然很挫，也算是新增了一个可用的工具。

run脚本：

run bb2008 'ps -ef | grep drct'

使用pexpect执行ssh -l，在bb-testing-oped2008.vm机器上执行命令ps -ef | grep drct，显示执行结果，退出状态与远程退出状态相同

run

#!/bin/sh

if [ $# -lt 2 ]; then
    echo ': run $host $cmd'
    echo ": run bb2008 'ps -ef | grep drct'"
    echo "please use 'run' with user 'work'"
    exit 1
fi

python /usr/bin/Expect.py $@

Expect.py

#!/usr/bin/env python

import pexpect
import sys
import getpass, os

class Expect:
    '''
    run remote command with pexpect
    '''
    def __init__(self, host='', usr='', pwd=''):
        self.host = host
        self.usr = usr
        self.pwd = pwd
        self.res = None

    def _ssh_command (self, host, user, password, command):
        ssh_newkey = 'Are you sure you want to continue connecting'
        child = pexpect.spawn('ssh -l %s %s %s'%(user, host, command))
        i = child.expect([pexpect.TIMEOUT, ssh_newkey, 'password: '])

        if i == 0: # Timeout
            print 'ERROR!'
            print 'SSH could not login. Here is what SSH said:'
            print child.before, child.after
            return None

        if i == 1: # SSH does not have the public key. Just accept it.
            child.sendline ('yes')
            child.expect ('password: ')
            i = child.expect([pexpect.TIMEOUT, 'password: '])
            if i == 0: # Timeout
                print 'ERROR!'
                print 'SSH could not login. Here is what SSH said:'
                print child.before, child.after
                return None

        child.sendline(password)
        return child

    def run_remote_command(self, cmd=''):
        '''
        run remote command $cmd
        users should set remote host/user/password by explicitly
        '''
        if self.host == '' or \
           self.usr  == '' or \
           self.pwd  == '':
            print '[Expect]: host/usr/pwd hasnot been set, please set correct values!'
            return None

        if cmd == '':
            print '[Expect]: parameter $cmd is empty, do nothing!'
            return None

        print '[Expect]: trying to ssh to %s@%s, and executes <%s>...'%(self.usr, self.host, cmd)
        cmd += ';echo $?'
        child = self._ssh_command(self.host, self.usr, self.pwd, cmd)
        child.expect(pexpect.EOF)

        self.res = child.before
        return eval(child.before.split('\n')[-2].strip())

    def interactive_run_remote_command(self, cmd=''):
        '''
        run remote command $cmd interactively
        users should input remote host/user/password while running
        '''
        print '[Expect]: trying to remote run <%s>, please input remote host information:'%(cmd)
        cmd += ';echo $?'

        _host = raw_input('Hostname: ')
        _usr = raw_input('User: ')
        _pwd = getpass.getpass('Password: ')

        child = self._ssh_command(_host, _usr, _pwd, cmd)
        child.expect(pexpect.EOF)

        self.res = child.before
        return eval(child.before.split('\n')[-2].strip())

if __name__ == '__main__':
    try:
        host = sys.argv[1][0:2] + '-xxxxxxx-' + sys.argv[1][2:] + '.vm'
        cmd = ''
        for part in sys.argv[2:]:
            cmd += (part+' ')

        remote = Expect()
        remote.host = 'xxxxx'
        remote.usr = 'xxxxx'
        remote.pwd = 'xxxxxxxxx'

        status =  remote.run_remote_command(cmd)
        print remote.res
        exit(status)

    except Exception, e:
        print str(e)

2. ssh信任关系建立

欲建立机器A到机器B的信任：

机器A

$ ssh-keygen -t rsa

$ scp ~/.ssh/id_rsa.pub user@hostB:~/.ssh/

机器B

$ cd ~/.ssh/

$ mv id_rsa.pub authorized_keys

OK，机器A ssh到机器B不用输密码...

机器A在机器B远程执行命令： ssh -l user hostB ls

------------------------------------------------

好吧。。。好shability

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纯姐对于ssh双方建立信任关系失败的建议：

ssh密钥的权限很严格，每个目录和文件的权限都得对才OK：对于work账号的，要：

/home/work 755

.ssh 700
.ssh/* 600