ubuntu 11.10 desktop: paramiko.SSHException: No existing session

[wang yang]

https://answers.launchpad.net/ubuntu/+source/paramiko/+question/183769

if user is not root, and use "ssh.connect(xxxx, username=xxxx, password=xxxx)", it always report exception: "paramiko.SSHException: No existing session". through debug, can find it failed because access agent, so disable agent can work: "ssh.connect(xxxx, username=xxxx, password=xxxx, allow_agent=False)"

python ssh_test.py

*INFO* Logging into '10.56.117.82:22' as 'root'.
Traceback (most recent call last):
  File "ssh_test.py", line 22, in <module>
    main()
  File "ssh_test.py", line 14, in main
    ssh.login(user, passwd)
  File "/usr/local/lib/python2.7/dist-packages/SSHLibrary/__init__.py", line 193, in login
    self._client.login(username, password)
  File "/usr/local/lib/python2.7/dist-packages/SSHLibrary/pythonclient.py", line 46, in login
    self.client.connect(self.host, self.port, username, password)
  File "build/bdist.linux-i686/egg/paramiko/client.py", line 332, in connect
  File "build/bdist.linux-i686/egg/paramiko/client.py", line 493, in _auth

DEBUG:paramiko.transport:starting thread (client mode): 0x919a1ccL
INFO:paramiko.transport:Connected (version 2.0, client OpenSSH_4.3)
DEBUG:paramiko.transport:kex algos:['diffie-hellman-group-exchange-sha1', 'diffie-hellman-group14-sha1', 'diffie-hellman-group1-sha1'] server key:['ssh-rsa', 'ssh-dss'] client encrypt:['aes128-ctr', 'aes192-ctr', 'aes256-ctr', 'arcfour256', 'arcfour128', 'aes128-cbc', '3des-cbc', 'blowfish-cbc', 'cast128-cbc', 'aes192-cbc', 'aes256-cbc', 'arcfour', '<email address hidden>'] server encrypt:['aes128-ctr', 'aes192-ctr', 'aes256-ctr', 'arcfour256', 'arcfour128', 'aes128-cbc', '3des-cbc', 'blowfish-cbc', 'cast128-cbc', 'aes192-cbc', 'aes256-cbc', 'arcfour', '<email address hidden>'] client mac:['hmac-md5', 'hmac-sha1', 'hmac-ripemd160', '<email address hidden>', 'hmac-sha1-96', 'hmac-md5-96'] server mac:['hmac-md5', 'hmac-sha1', 'hmac-ripemd160', '<email address hidden>', 'hmac-sha1-96', 'hmac-md5-96'] client compress:['none', '<email address hidden>'] server compress:['none', '<email address hidden>'] client lang:[''] server lang:[''] 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 10.56.117.82: 36a9604e78384576455244088b688c0a
DEBUG:paramiko.transport:Trying SSH agent key 94fb43f4fcab28b992cc3f07ecbd1484
DEBUG:paramiko.transport:userauth is OK
ERROR:paramiko.transport:Exception: key cannot be used for signing
ERROR:paramiko.transport:Traceback (most recent call last):
ERROR:paramiko.transport: File "build/bdist.linux-i686/egg/paramiko/transport.py", line 1559, in run
ERROR:paramiko.transport: self.auth_handler._handler_table[ptype](self.auth_handler, m)
ERROR:paramiko.transport: File "build/bdist.linux-i686/egg/paramiko/auth_handler.py", line 209, in _parse_service_accept
ERROR:paramiko.transport: sig = self.private_key.sign_ssh_data(self.transport.rng, blob)
ERROR:paramiko.transport: File "build/bdist.linux-i686/egg/paramiko/agent.py", line 152, in sign_ssh_data
ERROR:paramiko.transport: raise SSHException('key cannot be used for signing')
ERROR:paramiko.transport:SSHException: key cannot be used for signing
ERROR:paramiko.transport:
Traceback (most recent call last):
  File "test.py", line 19, in <module>
    main()
  File "test.py", line 8, in main
    ssh.connect(ip_addr, username=user, password=passwd)
  File "build/bdist.linux-i686/egg/paramiko/client.py", line 332, in connect
  File "build/bdist.linux-i686/egg/paramiko/client.py", line 493, in _auth
paramiko.SSHException: No existing session

[wang yang (wang-yang1980)]

i checked paramiko, in agent.py

     self.conn = None
 59 self.keys = ()
 60 if ('SSH_AUTH_SOCK' in os.environ) and (sys.platform != 'win32'):
 61 conn = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
 62 try:
 63 conn.connect(os.environ['SSH_AUTH_SOCK'])
 64 except:
 65 # probably a dangling env var: the ssh agent is gone
 66 return
 67 self.conn = conn
 68 elif sys.platform == 'win32':
 69 import win_pageant
 70 if win_pageant.can_talk_to_agent():
 71 self.conn = win_pageant.PageantConnection()
 72 else:
 73 return

it will use SSH_AUTH_SOCK envrionment variable when through auth_publickey
SSH_AUTH_SOCK=/tmp/keyring-2bBsGe/ssh

for root user, has no such envrionment variable, so it is ok.
if i add, it will fail too.

[wang yang (wang-yang1980)]

y136wang@y136wang-VirtualBox:~/work/Eclipse_workspace/python_test/src$ export SSH_AUTH_SOCK=/tmp/ssh-aqGtVuyQ1583/agent.1583
y136wang@y136wang-VirtualBox:~/work/Eclipse_workspace/python_test/src$ python test.py
out: /root

err:
y136wang@y136wang-VirtualBox:~/work/Eclipse_workspace/python_test/src$ export SSH_AUTH_SOCK=/tmp/keyring-2bBsGe/ssh
y136wang@y136wang-VirtualBox:~/work/Eclipse_workspace/python_test/src$ python test.py
No handlers could be found for logger "paramiko.transport"
Traceback (most recent call last):
  File "test.py", line 20, in <module>
    main()
  File "test.py", line 9, in main
    ssh.connect(ip_addr, username=user, password=passwd)
  File "build/bdist.linux-i686/egg/paramiko/client.py", line 332, in connect
  File "build/bdist.linux-i686/egg/paramiko/client.py", line 493, in _auth
paramiko.SSHException: No existing session
y136wang@y136wang-VirtualBox:~/work/Eclipse_workspace/python_test/src$