python - 使用 pexpect 和 pxssh 时的 EOF

Question

我正在尝试运行 Violent Python 第 2 章中通过 Pexpect 与 SSH 交互 和使用 Pxssh 强制 SSH 密码 部分中的代码.同时使用 child.expect() 和 pxssh 我得到类似的 EOF 错误。

从 Python 控制台运行这些命令:

import pexpect
connStr = "ssh root@127.0.0.1"
child = pexpect.spawn(connStr)
ret = child.expect([pexpect.TIMEOUT, ssh_newkey, "[P|p]assword:"])

我得到这个输出:

Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pexpect.py", li
ne 1316, in expect
    return self.expect_list(compiled_pattern_list, timeout, searchwindowsize)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pexpect.py", li
ne 1330, in expect_list
    return self.expect_loop(searcher_re(pattern_list), timeout, searchwindowsize)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pexpect.py", li
ne 1401, in expect_loop
    raise EOF (str(e) + '\n' + str(self))
EOF: End Of File (EOF) in read_nonblocking(). Empty string style platform.
<pexpect.spawn object at 0x10180c550>
version: 2.4 ($Revision: 516 $)
command: /usr/bin/ssh
args: ['/usr/bin/ssh', 'root@127.0.0.1']
searcher: searcher_re:
    0: TIMEOUT
    1: re.compile("Are you sure you want to continue connecting")
    2: re.compile("[P|p]assword:")
buffer (last 100 chars): 
before (last 100 chars): 
after: <class 'pexpect.EOF'>
match: None
match_index: None
exitstatus: 255 
flag_eof: True
pid: 12122
child_fd: 4
closed: False
timeout: 30
delimiter: <class 'pexpect.EOF'>
logfile: None
logfile_read: None
logfile_send: None
maxread: 2000
ignorecase: False
searchwindowsize: None
delaybeforesend: 0.05
delayafterclose: 0.1
delayafterterminate: 0.1

然后使用 pxssh 运行这些命令:

import pxssh
s = pxssh.pxssh()
s.login("127.0.0.1", "root", "1234")

我得到这个输出:

Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pxssh.py", line
 196, in login
    i = self.expect(["(?i)are you sure you want to continue connecting", original_prompt, "(?i)(?:pas
sword)|(?:passphrase for key)", "(?i)permission denied", "(?i)terminal type", TIMEOUT, "(?i)connectio
n closed by remote host"], timeout=login_timeout)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pexpect.py", li
ne 1316, in expect
    return self.expect_list(compiled_pattern_list, timeout, searchwindowsize)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pexpect.py", li
ne 1330, in expect_list
    return self.expect_loop(searcher_re(pattern_list), timeout, searchwindowsize)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pexpect.py", li
ne 1401, in expect_loop
    raise EOF (str(e) + '\n' + str(self))
EOF: End Of File (EOF) in read_nonblocking(). Empty string style platform.
<pxssh.pxssh object at 0x1016bff90>
version: 2.4 ($Revision: 516 $)
command: /usr/bin/ssh
args: ['/usr/bin/ssh', '-q', '-l', 'root', '127.0.0.1']
searcher: searcher_re:
    0: re.compile("(?i)are you sure you want to continue connecting")
    1: re.compile("[#$]")
    2: re.compile("(?i)(?:password)|(?:passphrase for key)")
    3: re.compile("(?i)permission denied")
    4: re.compile("(?i)terminal type")
    5: TIMEOUT
    6: re.compile("(?i)connection closed by remote host")
buffer (last 100 chars): 
before (last 100 chars): 
after: <class 'pexpect.EOF'>
match: None
match_index: None
exitstatus: None
flag_eof: True
pid: 12136
child_fd: 3
closed: False
timeout: 30
delimiter: <class 'pexpect.EOF'>
logfile: None
logfile_read: None
logfile_send: None
maxread: 2000
ignorecase: False
searchwindowsize: None
delaybeforesend: 0.05
delayafterclose: 0.1
delayafterterminate: 0.1

当我将 127.0.0.1 替换为其他主机并尝试不同的用户名/密码组合时，我得到了类似的结果。

pexpect documentation建议使用 expect(pexpect.EOF) 来避免生成 EOF 异常。事实上，当我执行以下操作时:

connStr = "ssh root@127.0.0.1"
child = pexpect.spawn(connStr)
print child.expect(pexpect.EOF)

结果是0。

但还有以下问题:

1. 我对这本书的语法感到困惑:child.expect([pexpect.TIMEOUT, ssh_newkey, "[P|p]assword:"])。为什么我们要将列表传递给 expect()？这个列表应该包含什么？
2. 在使用 pxssh 时，如何按照文档中的说明使用 expect(pexpect.EOF)？
3. 为什么书中的代码不能正常运行？自本书出版以来，pexpect 库中有什么变化吗？是因为我使用的是 OS X 吗？

我在 Mac OS X 10.8.4 上运行 Python 2.7 和 pexpect 2.4。

Answer 1

关于 #2:期待 EOF 在这里是一个转移注意力的问题。您 - 不要 - 期望登录时出现 EOF，您期望登录时出现密码提示。 pxssh 在从 ssh 登录时返回 EOF 而没有得到密码提示时会踢出该错误。发生这种情况是因为它使用 ssh -q 没有收到警告，而您从 ssh 收到警告。获取它正在使用的 ssh 选项并在没有 q 的情况下自己运行它们:

/usr/bin/ssh -l root 127.0.0.1

在我的例子中，当 ssh 踢出已知主机违规时，由于我连接到的机器的身份已更改，我会收到此错误消息。