SSH client & key policies
- class paramiko.client.SSHClient¶
A high-level representation of a session with an SSH server. This class wraps
SFTPClientto take care of most aspects of authenticating and opening channels. A typical use case is:
client = SSHClient() client.load_system_host_keys() client.connect('ssh.example.com') stdin, stdout, stderr = client.exec_command('ls -l')
You may pass in explicit overrides for authentication and server host key checking. The default mechanism is to try to use local key files or an SSH agent (if one is running).
Instances of this class may be used as context managers.
New in version 1.6.
Create a new SSHClient.
Load host keys from a system (read-only) file. Host keys read with this method will not be saved back by
This method can be called multiple times. Each new set of host keys will be merged with the existing set (new replacing old if there are conflicts).
filenameis left as
None, an attempt will be made to read keys from the user’s local “known hosts” file, as used by OpenSSH, and no exception will be raised if the file can’t be read. This is probably only useful on posix.
filename (str) – the filename to read, or
IOError– if a filename was provided and the file could not be read
Load host keys from a local host-key file. Host keys read with this method will be checked after keys loaded via
load_system_host_keys, but will be saved back by
save_host_keys(so they can be modified). The missing host key policy
AutoAddPolicyadds keys to this set and saves them, when connecting to a previously-unknown server.
This method can be called multiple times. Each new set of host keys will be merged with the existing set (new replacing old if there are conflicts). When automatically saving, the last hostname is used.
filename (str) – the filename to read
IOError– if the filename could not be read
filename (str) – the filename to save to
IOError– if the file could not be written
Get the local
HostKeysobject. This can be used to examine the local host keys or change them.
the local host keys as a
Set the channel for logging. The default is
"paramiko.transport"but it can be set to anything you want.
name (str) – new channel name for logging
Set policy to use when connecting to servers without a known host key.
policy (MissingHostKeyPolicy) – the policy to use when receiving a host key from a previously-unknown server
- connect(hostname, port=22, username=None, password=None, pkey=None, key_filename=None, timeout=None, allow_agent=True, look_for_keys=True, compress=False, sock=None, gss_auth=False, gss_kex=False, gss_deleg_creds=True, gss_host=None, banner_timeout=None, auth_timeout=None, channel_timeout=None, gss_trust_dns=True, passphrase=None, disabled_algorithms=None, transport_factory=None, auth_strategy=None)¶
Connect to an SSH server and authenticate to it. The server’s host key is checked against the system host keys (see
load_system_host_keys) and any local host keys (
load_host_keys). If the server’s hostname is not found in either set of host keys, the missing host key policy is used (see
set_missing_host_key_policy). The default policy is to reject the key and raise an
Authentication is attempted in the following order of priority:
key_filenamepassed in (if any)
key_filenamemay contain OpenSSH public certificate paths as well as regular private-key paths; when files ending in
-cert.pubare found, they are assumed to match a private key, and both components will be loaded. (The private key itself does not need to be listed in
key_filenamefor this to occur - just the certificate.)
Any key we can find through an SSH agent
Any “id_rsa”, “id_dsa” or “id_ecdsa” key discoverable in
When OpenSSH-style public certificates exist that match an existing such private key (so e.g. one has
id_rsa-cert.pub) the certificate will be loaded alongside the private key and used for authentication.
Plain username/password auth, if a password was given
If a private key requires a password to unlock it, and a password is passed in, that password will be used to attempt to unlock the key.
hostname (str) – the server to connect to
port (int) – the server port to connect to
username (str) – the username to authenticate as (defaults to the current local username)
password (str) – Used for password authentication; is also used for private key decryption if
passphraseis not given.
passphrase (str) – Used for decrypting private keys.
pkey (PKey) – an optional private key to use for authentication
key_filename (str) – the filename, or list of filenames, of optional private key(s) and/or certs to try for authentication
timeout (float) – an optional timeout (in seconds) for the TCP connect
allow_agent (bool) – set to False to disable connecting to the SSH agent
look_for_keys (bool) – set to False to disable searching for discoverable private key files in
compress (bool) – set to True to turn on compression
sock (socket) – an open socket or socket-like object (such as a
Channel) to use for communication to the target host
gss_auth (bool) –
Trueif you want to use GSS-API authentication
gss_kex (bool) – Perform GSS-API Key Exchange and user authentication
gss_deleg_creds (bool) – Delegate GSS-API client credentials or not
gss_host (str) – The targets name in the kerberos database. default: hostname
gss_trust_dns (bool) – Indicates whether or not the DNS is trusted to securely canonicalize the name of the host being connected to (default
banner_timeout (float) – an optional timeout (in seconds) to wait for the SSH banner to be presented.
auth_timeout (float) – an optional timeout (in seconds) to wait for an authentication response.
channel_timeout (float) – an optional timeout (in seconds) to wait for a channel open response.
transport_factory – an optional callable which is handed a subset of the constructor arguments (primarily those related to the socket, GSS functionality, and algorithm selection) and generates a
Transportinstance to be used by this client. Defaults to
an optional instance of
AuthStrategy, triggering use of this newer authentication mechanism instead of SSHClient’s legacy auth method.
This parameter is incompatible with all other authentication-related parameters (such as, but not limited to,
allow_agent) and will trigger an exception if given alongside them.
None; otherwise, returns
BadHostKeyException – if the server’s host key could not be verified.
AuthenticationException – if authentication failed.
UnableToAuthenticate – if authentication failed (when
None; and note that this is a subclass of
socket.error – if a socket error (other than connection-refused or host-unreachable) occurred while connecting.
NoValidConnectionsError – if all valid connection targets for the requested hostname (eg IPv4 and IPv6) yielded connection-refused or host-unreachable socket errors.
SSHException – if there was any other error connecting or establishing an SSH session.
Changed in version 1.15: Added the
Changed in version 2.3: Added the
Changed in version 2.4: Added the
Changed in version 2.6: Added the
Changed in version 2.12: Added the
Changed in version 3.2: Added the
Close this SSHClient and its underlying
This should be called anytime you are done using the client object.
Paramiko registers garbage collection hooks that will try to automatically close connections for you, but this is not presently reliable. Failure to explicitly close your client after use may lead to end-of-process hangs!
- exec_command(command, bufsize=- 1, timeout=None, get_pty=False, environment=None)¶
Execute a command on the SSH server. A new
Channelis opened and the requested command is executed. The command’s input and output streams are returned as Python
file-like objects representing stdin, stdout, and stderr.
command (str) – the command to execute
bufsize (int) – interpreted the same way as by the built-in
file()function in Python
environment (dict) –
a dict of shell environment variables, to be merged into the default environment that the remote command executes within.
Servers may silently reject some environment variables; see the warning in
the stdin, stdout, and stderr of the executing command, as a 3-tuple
SSHException– if the server fails to execute the command
Changed in version 1.10: Added the
- invoke_shell(term='vt100', width=80, height=24, width_pixels=0, height_pixels=0, environment=None)¶
Start an interactive shell session on the SSH server. A new
Channelis opened and connected to a pseudo-terminal using the requested terminal type and size.
term (str) – the terminal type to emulate (for example,
width (int) – the width (in characters) of the terminal window
height (int) – the height (in characters) of the terminal window
width_pixels (int) – the width (in pixels) of the terminal window
height_pixels (int) – the height (in pixels) of the terminal window
environment (dict) – the command’s environment
Channelconnected to the remote shell
SSHException– if the server fails to invoke a shell
- class paramiko.client.MissingHostKeyPolicy¶
Interface for defining the policy that
SSHClientshould use when the SSH server’s hostname is not in either the system host keys or the application’s keys. Pre-made classes implement policies for automatically adding the key to the application’s
AutoAddPolicy), and for automatically rejecting the key (
This function may be used to ask the user to verify the key, for example.
- missing_host_key(client, hostname, key)¶
Called when an
SSHClientreceives a server key for a server that isn’t in either the system or local
HostKeysobject. To accept the key, simply return. To reject, raised an exception (which will be passed to the calling application).
list of weak references to the object (if defined)
- class paramiko.client.AutoAddPolicy¶
- class paramiko.client.RejectPolicy¶
Policy for automatically rejecting the unknown hostname & key. This is used by
- class paramiko.client.WarningPolicy¶
Policy for logging a Python-style warning for an unknown host key, but accepting it. This is used by