python - 强制命令打开时 paramiko 不起作用

Question

我正在尝试通过 ssh 执行一些命令。

import paramiko
client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
private_key = paramiko.RSAKey.from_private_key_file("/home/kalombo/identity")
client.connect(hostname=host, username=username, pkey=private_key)
stdin, stdout, stderr = client.exec_command('pwd', timeout=5)
for line in stdout:
    print '... ' + line.strip('\n')
client.close()

如果 ssh 服务器具有强制命令选项，则脚本会在超时到期时停止并且不执行任何操作。有调试日志。您可以注意到“强制命令”行:

DEBUG:paramiko.transport:starting thread (client mode): 0xb6d1bb4cL
INFO:paramiko.transport:Connected (version 2.0, client OpenSSH_6.0p1)
DEBUG:paramiko.transport:kex algos:[u'ecdh-sha2-nistp256', u'ecdh-sha2-nistp384', u'ecdh-sha2-nistp521', u'diffie-hellman-group-exchange-sha256', u'diffie-hellman-group-exchange-sha1', u'diffie-hellman-group14-sha1', u'diffie-hellman-group1-sha1'] server key:[u'ssh-rsa', u'ssh-dss', u'ecdsa-sha2-nistp256'] client encrypt:[u'aes128-ctr', u'aes192-ctr', u'aes256-ctr', u'arcfour256', u'arcfour128', u'aes128-cbc', u'3des-cbc', u'blowfish-cbc', u'cast128-cbc', u'aes192-cbc', u'aes256-cbc', u'arcfour', u'rijndael-cbc@lysator.liu.se'] server encrypt:[u'aes128-ctr', u'aes192-ctr', u'aes256-ctr', u'arcfour256', u'arcfour128', u'aes128-cbc', u'3des-cbc', u'blowfish-cbc', u'cast128-cbc', u'aes192-cbc', u'aes256-cbc', u'arcfour', u'rijndael-cbc@lysator.liu.se'] client mac:[u'hmac-md5', u'hmac-sha1', u'umac-64@openssh.com', u'hmac-sha2-256', u'hmac-sha2-256-96', u'hmac-sha2-512', u'hmac-sha2-512-96', u'hmac-ripemd160', u'hmac-ripemd160@openssh.com', u'hmac-sha1-96', u'hmac-md5-96'] server mac:[u'hmac-md5', u'hmac-sha1', u'umac-64@openssh.com', u'hmac-sha2-256', u'hmac-sha2-256-96', u'hmac-sha2-512', u'hmac-sha2-512-96', u'hmac-ripemd160', u'hmac-ripemd160@openssh.com', u'hmac-sha1-96', u'hmac-md5-96'] client compress:[u'none', u'zlib@openssh.com'] server compress:[u'none', u'zlib@openssh.com'] client lang:[u''] server lang:[u''] kex follows?False
DEBUG:paramiko.transport:Ciphers agreed: local=aes128-ctr, remote=aes128-ctr
DEBUG:paramiko.transport:using kex diffie-hellman-group1-sha1; server key type ssh-rsa; cipher: local aes128-ctr, remote aes128-ctr; mac: local hmac-sha1, remote hmac-sha1; compression: local none, remote none
DEBUG:paramiko.transport:Switch to new keys ...
DEBUG:paramiko.transport:Adding ssh-rsa host key for 8.8.8.8: 54c2349797979732dda94989530c1f4
DEBUG:paramiko.transport:Trying SSH key 7d834324323429b09824eb
DEBUG:paramiko.transport:userauth is OK
INFO:paramiko.transport:Authentication (publickey) successful!
DEBUG:paramiko.transport:Debug msg: Forced command.
DEBUG:paramiko.transport:Debug msg: Port forwarding disabled.
DEBUG:paramiko.transport:Debug msg: X11 forwarding disabled.
DEBUG:paramiko.transport:Debug msg: Agent forwarding disabled.
DEBUG:paramiko.transport:Debug msg: Pty allocation disabled.
DEBUG:paramiko.transport:[chan 1] Max packet in: 34816 bytes
DEBUG:paramiko.transport:[chan 1] Max packet out: 32768 bytes
INFO:paramiko.transport:Secsh channel 1 opened.
DEBUG:paramiko.transport:[chan 1] Sesch channel 1 request ok

如果我禁用该选项一切正常。为什么会这样？我该如何解决？

Answer 1

DEBUG:paramiko.transport:Debug msg: Forced command.

没有办法解决这个问题。如果服务器为 key 配置了强制命令，那么您使用该 key 打开的任何 session 都将导致服务器忽略您请求的命令并调用强制命令。

如果不知道服务器正在运行什么命令，就无法知道它为什么挂起。强制命令可能正在等待来自远程 ssh 客户端的输入，在这种情况下它将无限期地等待。

强制命令可以通过环境变量“SSH_ORIGINAL_COMMAND”访问客户端请求的原始命令。强制命令可以检查此变量并调用客户端请求的命令，但必须在编写强制命令时考虑到此功能。