Python paramiko.ssh_exception.SSHException：无现有会话

问题描述

此站点的示例代码（https://www.kite.com/python/answers/how-to-ssh-using-paramiko-in-python）

host = "test.rebex.net"
port = 22
username = "demo"
password = "password"

command = "ls"

ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(host,port,username,password)

stdin,stdout,stderr = ssh.exec_command(command)
lines = stdout.readlines()
print(lines)

应该产生此输出。

['aspnet_client\n','pub\n','readme.txt\n']

此演示站点的凭据运行正常

wolf@linux:~$ sshpass -p password ssh [e-mail]
Welcome to Rebex Virtual Shell!
For a list of supported commands,type 'help'.
demo@ETNA:/$ 
demo@ETNA:/$ ls
aspnet_client
pub
readme.txt
demo@ETNA:/$ 

但是，代码无法按预期运行。 ssh.connect(host,password)行后出现错误。

>>> import paramiko
>>> host = "test.rebex.net"
>>> username = "demo"
>>> password = "password"
>>> port = 22
>>> 
>>> command = "ls"
>>> 
>>> ssh = paramiko.SSHClient()
>>> ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
>>> ssh.connect(host,password)
Traceback (most recent call last):
  File "<stdin>",line 1,in <module>
  File "/home/wolf/.local/lib/python3.8/site-packages/paramiko/client.py",line 435,in connect
    self._auth(
  File "/home/wolf/.local/lib/python3.8/site-packages/paramiko/client.py",line 764,in _auth
    raise saved_exception
  File "/home/wolf/.local/lib/python3.8/site-packages/paramiko/client.py",line 751,in _auth
    self._transport.auth_password(username,password)
  File "/home/wolf/.local/lib/python3.8/site-packages/paramiko/transport.py",line 1498,in auth_password
    raise SSHException("No existing session")
paramiko.ssh_exception.SSHException: No existing session
>>> 

让我知道如何实现此目的。我只想要一个简单的SSH连接代码。

更新

>>> ssh.connect(host,password,look_for_keys=False,allow_agent=False)
>>> 

参考：https://github.com/ktbyers/netmiko/issues/1034

解决方法

该代码对我有用。

---

当我在Pageant中加载了密钥时，我在auth_password中也遇到了错误（尽管有所不同– “验证失败” ）。在Paramiko尝试使用Pageant键后，Rebex测试服务器似乎关闭了会话。这样，连续的密码身份验证将失败。我猜这将是一个类似的问题。不同的错误消息可能只是由于时间差异而引起的。

starting thread (client mode): 0x33629f0
Local version/idstring: SSH-2.0-paramiko_2.6.0
Remote version/idstring: SSH-2.0-RebexSSH_5.0.7448.0
Connected (version 2.0,client RebexSSH_5.0.7448.0)
kex algos:['curve25519-sha256','[e-mail]','ecdh-sha2-nistp521','ecdh-sha2-nistp384','ecdh-sha2-nistp256','diffie-hellman-group16-sha512','diffie-hellman-group15-sha512','diffie-hellman-group-exchange-sha256','diffie-hellman-group14-sha256','diffie-hellman-group14-sha1','diffie-hellman-group-exchange-sha1'] server key:['ssh-ed25519','ecdsa-sha2-nistp256','rsa-sha2-512','[e-mail]','rsa-sha2-256','ssh-rsa'] client encrypt:['[e-mail]','[e-mail]','aes256-ctr','aes256-cbc','aes192-ctr','aes192-cbc','aes128-ctr','aes128-cbc','[e-mail]','twofish256-ctr','twofish192-ctr','twofish128-ctr','twofish256-cbc','twofish192-cbc','twofish128-cbc','twofish-cbc','3des-ctr','3des-cbc'] server encrypt:['[e-mail]','3des-cbc'] client mac:['[e-mail]','[e-mail]','hmac-sha2-512','hmac-sha2-256','hmac-sha1','hmac-sha1-96'] server mac:['[e-mail]','hmac-sha1-96'] client compress:['none'] server compress:['none'] client lang:[''] server lang:[''] kex follows?False
Kex agreed: [e-mail]
HostKey agreed: ssh-ed25519
Cipher agreed: aes128-ctr
MAC agreed: hmac-sha2-256
Compression agreed: none
kex engine KexCurve25519 specified hash_algo <built-in function openssl_sha256>
Switch to new keys ...
Adding ssh-ed25519 host key for test.rebex.net: b'e7e445c6b8e4bbd868892786fd0158f0'
Trying SSH agent key b'3f3ae3e3b0e0ef4e5b4bfe93613557d4'
userauth is OK
Authentication (publickey) failed.
Disconnect (code 2): Authentication is already in progress.

---

如果要避免尝试Pageant，请使用SSHClient.connect的allow_agent参数：

ssh.connect(host,port,username,password,allow_agent=False)

---

强制性警告：请勿使用AutoAddPolicy-这样做会失去对MITM attacks的保护。有关正确的解决方案，请参见Paramiko "Unknown Server" 。