Paramiko AuthenticationException issue

https://stackoverflow.com/questions/4135261

30-09-2019
|

Question

I am having a problem connecting to a device with a Paramiko (version 1.7.6-2) ssh client:

$ python
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) 
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import paramiko
>>> ssh = paramiko.SSHClient()
>>> ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
>>> ssh.connect("123.0.0.1", username="root", password=None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/pymodules/python2.6/paramiko/client.py", line 327, in connect
    self._auth(username, password, pkey, key_filenames, allow_agent, look_for_keys)
  File "/usr/lib/pymodules/python2.6/paramiko/client.py", line 481, in _auth
    raise saved_exception
paramiko.AuthenticationException: Authentication failed.
>>>

When I use ssh from the command line, it works fine:

ssh root@123.0.0.1


BusyBox v1.12.1 (2010-11-03 13:18:46 EDT) built-in shell (ash)
Enter 'help' for a list of built-in commands.

#

Anyone seen this before?

Edit 1

Here is the verbose output of the ssh command:

:~$ ssh -v root@123.0.0.1
OpenSSH_5.3p1 Debian-3ubuntu4, OpenSSL 0.9.8k 25 Mar 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to 123.0.0.1 [123.0.0.1] port 22.
debug1: Connection established.
debug1: identity file /home/waffleman/.ssh/identity type -1
debug1: identity file /home/waffleman/.ssh/id_rsa type -1
debug1: identity file /home/waffleman/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.1
debug1: match: OpenSSH_5.1 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu4
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host '123.0.0.1' is known and matches the RSA host key.
debug1: Found key in /home/waffleman/.ssh/known_hosts:3
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentication succeeded (none).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: Sending environment.
debug1: Sending env LANG = en_US.utf8

Edit 2 Here is the python output with debug output:

Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) 
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import paramiko, os
>>> paramiko.common.logging.basicConfig(level=paramiko.common.DEBUG)
>>> ssh = paramiko.SSHClient()
>>> ssh.load_system_host_keys()
>>> ssh.load_host_keys(os.path.expanduser('~/.ssh/known_hosts'))
>>> ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
>>> ssh.connect("123.0.0.1", username='root', password=None)
DEBUG:paramiko.transport:starting thread (client mode): 0x928756cL
INFO:paramiko.transport:Connected (version 2.0, client OpenSSH_5.1)
DEBUG:paramiko.transport:kex algos:['diffie-hellman-group-exchange-sha256', 'diffie-hellman-group-exchange-sha1', 'diffie-hellman-group14-sha1', 'diffie-hellman-group1-sha1'] server key:['ssh-rsa', 'ssh-dss'] client encrypt:['aes128-cbc', '3des-cbc', 'blowfish-cbc', 'cast128-cbc', 'arcfour128', 'arcfour256', 'arcfour', 'aes192-cbc', 'aes256-cbc', 'rijndael-cbc@lysator.liu.se', 'aes128-ctr', 'aes192-ctr', 'aes256-ctr'] server encrypt:['aes128-cbc', '3des-cbc', 'blowfish-cbc', 'cast128-cbc', 'arcfour128', 'arcfour256', 'arcfour', 'aes192-cbc', 'aes256-cbc', 'rijndael-cbc@lysator.liu.se', 'aes128-ctr', 'aes192-ctr', 'aes256-ctr'] client mac:['hmac-md5', 'hmac-sha1', 'umac-64@openssh.com', 'hmac-ripemd160', 'hmac-ripemd160@openssh.com', 'hmac-sha1-96', 'hmac-md5-96'] server mac:['hmac-md5', 'hmac-sha1', 'umac-64@openssh.com', 'hmac-ripemd160', 'hmac-ripemd160@openssh.com', 'hmac-sha1-96', 'hmac-md5-96'] client compress:['none', 'zlib@openssh.com'] server compress:['none', 'zlib@openssh.com'] 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:Trying discovered key b945197b1de1207d9aa0663f01888c3c in /home/waffleman/.ssh/id_rsa
DEBUG:paramiko.transport:userauth is OK
INFO:paramiko.transport:Authentication (publickey) failed.
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/pymodules/python2.6/paramiko/client.py", line 327, in connect
    self._auth(username, password, pkey, key_filenames, allow_agent, look_for_keys)
  File "/usr/lib/pymodules/python2.6/paramiko/client.py", line 481, in _auth
    raise saved_exception
paramiko.AuthenticationException: Authentication failed.
>>>

Solution

The ssh server on the remote device denied your authentication. Make sure you're using the correct key, the public key is present in authorized_keys, .ssh directory permissions are correct, authorized_keys permissions are correct, and the device doesn't have any other access restrictions. It hard to say what's going on without logs from the server.

[EDIT] I just looked back through your output, you are authenticating using None authentication. This usually isn't ever permitted, and is used to determine what auth methods are allowed by the server. It's possible your server is using host based authentication (or none at all!).

Since auth_none() is rarely used, it's not accessible from the SSHClient class, so you will need to use Transport directly.

transport.auth_none('root')

OTHER TIPS

As a very late follow-up on this matter, I believe I was running into the same issue as waffleman, in a context of a confined network.

The hint about using auth_none on the Transport object turned out quite helpful, but I found myself a little puzzled as to how to implement that. Thing is, as of today at least, I can't get the Transport object of an SSHClient object until it has connected; but it won't connect in the first place...

So In case this is useful to others, my work around is below. I just override the _auth method.

OK, this is fragile, as _auth is a private thing. My other alternatives were - actually still are - to manually create the Transport and Channel objects, but for the time being I feel like I'm much better off with all this still under the hood.

from paramiko import SSHClient, BadAuthenticationType

class SSHClient_try_noauth(SSHClient):

    def _auth(self, username, *args):
        try:
            self._transport.auth_none(username)
        except BadAuthenticationType:
            super()._auth(username, *args)

Make sure that the permissions on the public and private key files (and possibly the containing folder) are set to very restrictive (i.e. chmod 600 id_rsa). It turns out this is required (by the Operating System?) to use the files as ssh keys. Found this out from my helpful colleague :) Also make sure that you are using the correct username for the given ssh key.

paramiko's SSHClient has load_system_host_keys method which you could use to load user specific set of keys. As example in the docs explain, it needs to be run before connecting to a server.

I get similar error, when the server uses AD authentication. I think this is a bug of paramiko. I have learned that I have to set ssh keys before use paramiko.

There could be different reasons on server side (sshd where you're connecting to), so it might be hard to debug on client side.

For example, tail -f /var/log/secure :

Oct 9 15:50:26 pc1udatahgw04 sshd[27501]: Authentication refused: bad ownership or modes for directory /home/testuser

If you run ls -lad /home/testuser to see permissions, you'll see for example in our case:

$ ls -lad /home/testuser
drwxrwxr-x 16 testuser  testgroup 57344 Oct  9 15:23 /home/testuser

Notice second w bit. Home directory was opened up for group writes. sshd refuses key based authentication in this case.

Again, check sshd log on server side. There could be other issues like already mentioned

/home/user/.ssh directory is too open
/home/user/.ssh/id_rsa file is too open
/home/user/.ssh/id_rsa.pub file is too open
/home/user/.ssh/id_ecdsa file is too open
/home/user/.ssh/id_ecdsa.pub file is too open

etc..

I have tried remove the folder ~./ssh,then it's working well

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