python - Paramiko的open_sftp()降落SSH服务器引发 “EOF during negotiation”异常

Question

这是我使用paramiko的代码:

#!/usr/bin/env python  
from paramiko.client import SSHClient  
from paramiko.client import AutoAddPolicy  
import logging; logging.basicConfig(); logging.getLogger('paramiko.transport').setLevel(logging.DEBUG)

class MySFTP(object):  
    def __init__(self, hostname, port, username, password):
        self.client = SSHClient()
        self.client.set_missing_host_key_policy(AutoAddPolicy)
        self.client.connect(hostname=hostname, port=port, username=username, password=password)  
        self.ssh_channel = self.client.invoke_shell()  
        self.sftp_session = self.client.open_sftp()

    def get_file_from_target(self,remotepath_file, localpath_file):
        self.sftp_session.get(remotepath=remotepath_file, localpath=localpath_file)

    def end_session(self):
        self.sftp_session.close()
        self.client.close()

if `__name__` == `'__main__'`:
    sftp_object = MySFTP(hostname="192.168.21.2", port=22, username="root", password="root")
    sftp_object.get_file_from_target(localpath_file = r"/home/admin1/folder_to_get/file_to_get", remotepath_file = r"/home/root/folder_to_get/file_to_get")
    print("File transferred successfully.")
    sftp_object.end_session()

出于某种原因，当我尝试从一台Linux计算机上获取文件时，此方法可以完美地工作，但是当尝试从目标系统中获取文件时，该方法将失败。我已经验证了在bash中尝试时可以通过ssh在两台计算机上执行命令。我还可以使用scp从两台计算机上获取文件。但是，在此代码中，使用以下日志从目标系统中获取文件时， self.sftp_session = self.client.open_sftp()行失败:

DEBUG:paramiko.transport:starting thread (client mode): 0x1b21c0d0L  
DEBUG:paramiko.transport:Local version/idstring: SSH-2.0-paramiko_2.4.0  
DEBUG:paramiko.transport:Remote version/idstring: SSH-2.0-dropbear_2016.72  
INFO:paramiko.transport:Connected (version 2.0, client dropbear_2016.72)  
DEBUG:paramiko.transport:kex algos:[u'curve25519-sha256@libssh.org', u'ecdh-sha2-nistp521', u'ecdh-sha2-nistp384', u'ecdh-sha2-nistp256', u'diffie-hellman-group14-sha1', u'diffie-hellman-group1-sha1', u'kexguess2@matt.ucc.asn.au'] server key:[u'ssh-rsa'] client encrypt:[u'aes128-ctr', u'aes256-ctr', u'aes128-cbc', u'aes256-cbc', u'twofish256-cbc', u'twofish-cbc', u'twofish128-cbc', u'3des-ctr', u'3des-cbc'] server encrypt:[u'aes128-ctr', u'aes256-ctr', u'aes128-cbc', u'aes256-cbc', u'twofish256-cbc', u'twofish-cbc', u'twofish128-cbc', u'3des-ctr', u'3des-cbc'] client mac:[u'hmac-sha1-96', u'hmac-sha1', u'hmac-sha2-256', u'hmac-sha2-512', u'hmac-md5'] server mac:[u'hmac-sha1-96', u'hmac-sha1', u'hmac-sha2-256', u'hmac-sha2-512', u'hmac-md5'] client compress:[u'zlib@openssh.com', u'none'] server compress:[u'zlib@openssh.com', u'none'] client lang:[u''] server lang:[u''] kex follows?False  
DEBUG:paramiko.transport:Kex agreed: ecdh-sha2-nistp256  
DEBUG:paramiko.transport:HostKey agreed: ssh-rsa  
DEBUG:paramiko.transport:Cipher agreed: aes128-ctr  
DEBUG:paramiko.transport:MAC agreed: hmac-sha2-256  
DEBUG:paramiko.transport:Compression agreed: none  
DEBUG:paramiko.transport:kex engine KexNistp256 specified hash_algo <built-in function openssl_sha256>  
DEBUG:paramiko.transport:Switch to new keys ...  
DEBUG:paramiko.transport:Adding ssh-rsa host key for 192.168.21.2: f5b6a7b3fd5537ea9bd5085b49cbca7a  
DEBUG:paramiko.transport:userauth is OK  
INFO:paramiko.transport:Authentication (password) successful!  
DEBUG:paramiko.transport:[chan 0] Max packet in: 32768 bytes  
DEBUG:paramiko.transport:[chan 0] Max packet out: 32759 bytes  
DEBUG:paramiko.transport:Secsh channel 0 opened.  
DEBUG:paramiko.transport:[chan 0] Sesch channel 0 request ok  
DEBUG:paramiko.transport:[chan 0] Sesch channel 0 request ok  
DEBUG:paramiko.transport:[chan 1] Max packet in: 32768 bytes  
DEBUG:paramiko.transport:[chan 1] Max packet out: 32759 bytes  
DEBUG:paramiko.transport:Secsh channel 1 opened.  
DEBUG:paramiko.transport:[chan 1] Sesch channel 1 request ok  
DEBUG:paramiko.transport:[chan 1] EOF received (1)  
Traceback (most recent call last):  
  File "./sftp_remote_so.py", line 26, in <module>  
    sftp_object = MySFTP(hostname="192.168.21.2", port=22, username="root", password="root")  
  File "./sftp_remote_so.py", line 15, in __init__  
    self.sftp_session = self.client.open_sftp()  
  File "/usr/local/lib/python2.7/dist-packages/paramiko/client.py", line 521, in open_sftp  
    return self._transport.open_sftp_client()  
  File "/usr/local/lib/python2.7/dist-packages/paramiko/transport.py", line 980, in open_sftp_client  
    return SFTPClient.from_transport(self)  
  File "/usr/local/lib/python2.7/dist-packages/paramiko/sftp_client.py", line 140, in from_transport  
    return cls(chan)  
  File "/usr/local/lib/python2.7/dist-packages/paramiko/sftp_client.py", line 105, in __init__  
    raise SSHException('EOF during negotiation')  
paramiko.ssh_exception.SSHException: EOF during negotiation  

Answer 1

注意到您的远程SSH服务器是dropbear，并且我有一个OpenWRT wifi路由器(与SSH服务器具有dropbear)，所以我尝试了一下，并得到了同样的错误。

Traceback (most recent call last):
  File "foo.py", line 22, in <module>
    sftp_object = MySFTP(hostname="wifi", port=22, username="root", password="...")
  File "foo.py", line 12, in __init__
    self.sftp_session = self.client.open_sftp()
  File "/usr/lib/python2.7/dist-packages/paramiko/client.py", line 452, in open_sftp
    return self._transport.open_sftp_client()
  File "/usr/lib/python2.7/dist-packages/paramiko/transport.py", line 906, in open_sftp_client
    return SFTPClient.from_transport(self)
  File "/usr/lib/python2.7/dist-packages/paramiko/sftp_client.py", line 132, in from_transport
    return cls(chan)
  File "/usr/lib/python2.7/dist-packages/paramiko/sftp_client.py", line 101, in __init__
    raise SSHException('EOF during negotiation')
paramiko.ssh_exception.SSHException: EOF during negotiation

然后我尝试了手动 sftp到我的wifi路由器:

[STEP 101] # sftp wifi
root@wifi's password:
ash: /usr/libexec/sftp-server: not found
Connection closed
[STEP 102] #

因此，尽管SCP正常工作，但 dropbear似乎不支持SFTP。

更新:

在Debian 9上， dbclient( dropbear客户端)手册页显示:

[...] Dropbear doesn't implement sftp itself but the OpenSSH sftp client can be used [...]