使用Paramiko进行DSA密钥转发？

Question

我正在使用Paramiko在远程服务器上执行bash脚本。在这些脚本中，有些会连接到其他服务器。如果我只用bash，不用Python，我的DSA密钥会被转发，并且第一个远程服务器上的bash脚本可以用这个密钥连接到第二个远程服务器。但是当我使用Paramiko时，就不行了。

这是一个bash的例子：

Jean@mydesktop:~ & ssh root@firstserver
root@firstserver:~ # ssh root@secondserver hostname
secondserver.mydomain.org

使用Paramiko的情况：

#!/usr/bin/python3
# -*- coding: utf-8 -*-

import paramiko

class SSHSession:


    def __init__(self, server_address, user='root', port=22):
        self.connected = False
        self.server_address = server_address
        self.user           = user
        self.port           = port


    def connect(self, clear_channel=True):
        try:
            if self.server_address == None:
                raise ValueError('No hostname')
        except:
            raise ValueError('No hostname')
        else:
            try:
                self.ssh_client = paramiko.SSHClient()
                self.ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
                self.ssh_client.connect(self.server_address, username=self.user)
                #self.transport = self.ssh_client.get_transport()
                #self.channel   = self.transport.open_forward_agent_channel()
                self.channel   = self.ssh_client.invoke_shell()
            except:
                self.connected = False
                return False
            else:
                self.connected = True
                return True

    def exec_command(self, command, newline='\r'):
        if not self.connected:
            raise Exception('Not connected')
        else:
            timeout = 31536000 # 365 days in seconds
            self.channel.settimeout(timeout)
            line_buffer    = ''
            channel_buffer = ''
            end_string     = 'CLIENT_EXPECT_CMD_OK'
            print('[SEND   ] >>', command)
            self.channel.send(command + ' ; echo ' + end_string + newline)
            while True:
                channel_buffer = self.channel.recv(1).decode('UTF-8')
                if len(channel_buffer) == 0:
                    raise Exception('connection lost with server: ' + self.server_address)
                    break 
                channel_buffer  = channel_buffer.replace('\r', '')
                if channel_buffer != '\n':
                    line_buffer += channel_buffer
                else:
                    if line_buffer == end_string:
                        break
                    print('[RECEIVE] <<', line_buffer)
                    line_buffer   = ''


    def disconnect(self):
        self.ssh_client.close()


    def __enter__(self):
        self.connect()
        return self


    def __exit__(self, _type, value, traceback):
        self.disconnect()


if __name__ == "__main__":
    server_address = 'firstserver'
    ssh_user       = 'root'
    with SSHSession(server_address) as ssh_session:
        ssh_session.exec_command('hostname')
        ssh_session.exec_command('ssh root@secondserver hostname')

输出结果是：

[SEND   ] >> hostname
[RECEIVE] << [root@firstserver ~]# hostname ; echo CLIENT_EXPECT_CMD_OK
[RECEIVE] << firstserver.mydomain.fr
[SEND   ] >> ssh root@secondserver hostname
[RECEIVE] << [root@firstserver ~]# ssh root@secondserver hostname ; echo CLIENT_EXPECT_CMD_OK
[RECEIVE] << Permission denied (publickey,gssapi-keyex,gssapi-with-mic).

我尝试过：

self.transport = self.ssh_client.get_transport()
self.channel   = self.transport.open_forward_agent_channel()

而不是：

self.channel   = self.ssh_client.invoke_shell()

但是我遇到了一个错误：

paramiko.ssh_exception.ChannelException: Administratively prohibited

有没有人知道这是否可能？我看到有讨论说可以，但我还是找不到具体怎么做。

错误处理脚本执行远程服务器 bash脚本 paramiko ssh连接 dsa密钥密钥转发

使用Paramiko进行DSA密钥转发？

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