Configuration

Paramiko does not itself leverage OpenSSH-style config file directives, but it does implement a parser for the format, which users can honor themselves (and is used by higher-level libraries, such as Fabric).

The API for this is SSHConfig, which loads SSH config files from disk, file-like object, or string and exposes a “look up a hostname, get a dict of applicable keywords/values back” functionality.

As with OpenSSH’s own support, this dict will contain values from across the parsed file, depending on the order in which keywords were encountered and how specific or generic the Host or Match directives were.

Keywords currently supported

The following is an alphabetical list of which ssh_config directives Paramiko interprets during the parse/lookup process (as above, actual SSH connections do not reference parsed configs). Departures from OpenSSH’s implementation (e.g. to support backwards compat with older Paramiko releases) are included. A keyword by itself means no known departures.

  • AddressFamily: used when looking up the local hostname for purposes of expanding the %l/%L tokens (this is actually a minor value-add on top of OpenSSH, which doesn’t actually honor this setting when expanding %l).

  • CanonicalDomains

    New in version 2.7.

  • CanonicalizeFallbackLocal: when no, triggers raising of CouldNotCanonicalize for target hostnames which do not successfully canonicalize.

    New in version 2.7.

  • CanonicalizeHostname: along with the other Canonicaliz* settings (sans CanonicalizePermittedCNAMEs, which is not yet implemented), enables hostname canonicalization, insofar as calling SSHConfig.lookup with a given hostname will return a canonicalized copy of the config data, including an updated HostName value.

    New in version 2.7.

  • CanonicalizeMaxDots

    New in version 2.7.

  • Host

  • HostName: used in %h token expansion

  • Match: fully supported, with the following caveats:

    • You must have the optional dependency Invoke installed; see the installation docs (in brief: install paramiko[invoke] or paramiko[all]).
    • As usual, connection-time information is not present during config lookup, and thus cannot be used to determine matching. This primarily impacts Match user, which can match against loaded User values but has no knowledge about connection-time usernames.

    New in version 2.7.

  • Port: supplies potential values for %p token expansion.

  • ProxyCommand: see our ProxyCommand class for an easy way to honor this keyword from a config you’ve parsed.

    • Honors token expansion.
    • When a lookup would result in an effective ProxyCommand none, Paramiko (as of 1.x-2.x) strips it from the resulting dict entirely. A later major version may retain the "none" marker for clarity’s sake.
  • User: supplies potential values for %u token expansion.

Expansion tokens

We support most SSH config expansion tokens where possible, so when they are present in a config file source, the result of a SSHConfig.lookup will contain the expansions/substitutions (based on the rest of the config or properties of the local system).

Specifically, we are known to support the below, where applicable (e.g. as in OpenSSH, %L works in ControlPath but not elsewhere):

  • %d
  • %h
  • %l
  • %L
  • %n
  • %p
  • %r
  • %u: substitutes the configured User value, or the local user (as seen by getpass.getuser) if not specified.

In addition, we extend OpenSSH’s tokens as follows:

  • ~ is treated like %d (expands to the local user’s home directory path) when expanding ProxyCommand values, since ProxyCommand does not natively support %d for some reason.

config module API documentation

Mostly of interest to contributors; see previous section for behavioral details.

Configuration file (aka ssh_config) support.

class paramiko.config.LazyFqdn(config, host=None)

Returns the host’s fqdn on request as string.

__weakref__

list of weak references to the object (if defined)

class paramiko.config.SSHConfig

Representation of config information as stored in the format used by OpenSSH. Queries can be made via lookup. The format is described in OpenSSH’s ssh_config man page. This class is provided primarily as a convenience to posix users (since the OpenSSH format is a de-facto standard on posix) but should work fine on Windows too.

New in version 1.6.

__init__()

Create a new OpenSSH config object.

Note: the newer alternate constructors from_path, from_file and from_text are simpler to use, as they parse on instantiation. For example, instead of:

config = SSHConfig()
config.parse(open("some-path.config")

you could:

config = SSHConfig.from_file(open("some-path.config"))
# Or more directly:
config = SSHConfig.from_path("some-path.config")
# Or if you have arbitrary ssh_config text from some other source:
config = SSHConfig.from_text("Host foo\n\tUser bar")
__weakref__

list of weak references to the object (if defined)

canonicalize(hostname, options, domains)

Return canonicalized version of hostname.

Parameters:
  • hostname (str) – Target hostname.
  • options – An SSHConfigDict from a previous lookup pass.
  • domains – List of domains (e.g. ["paramiko.org"]).
Returns:

A canonicalized hostname if one was found, else None.

New in version 2.7.

classmethod from_file(flo)

Create a new, parsed SSHConfig from file-like object flo.

New in version 2.7.

classmethod from_path(path)

Create a new, parsed SSHConfig from the file found at path.

New in version 2.7.

classmethod from_text(text)

Create a new, parsed SSHConfig from text string.

New in version 2.7.

get_hostnames()

Return the set of literal hostnames defined in the SSH config (both explicit hostnames and wildcard entries).

lookup(hostname)

Return a dict (SSHConfigDict) of config options for a given hostname.

The host-matching rules of OpenSSH’s ssh_config man page are used: For each parameter, the first obtained value will be used. The configuration files contain sections separated by Host and/or Match specifications, and that section is only applied for hosts which match the given patterns or keywords

Since the first obtained value for each parameter is used, more host- specific declarations should be given near the beginning of the file, and general defaults at the end.

The keys in the returned dict are all normalized to lowercase (look for "port", not "Port". The values are processed according to the rules for substitution variable expansion in ssh_config.

Finally, please see the docs for SSHConfigDict for deeper info on features such as optional type conversion methods, e.g.:

conf = my_config.lookup('myhost')
assert conf['passwordauthentication'] == 'yes'
assert conf.as_bool('passwordauthentication') is True

Note

If there is no explicitly configured HostName value, it will be set to the being-looked-up hostname, which is as close as we can get to OpenSSH’s behavior around that particular option.

Parameters:hostname (str) – the hostname to lookup

Changed in version 2.5: Returns SSHConfigDict objects instead of dict literals.

Changed in version 2.7: Added canonicalization support.

Changed in version 2.7: Added Match support.

parse(file_obj)

Read an OpenSSH config from the given file object.

Parameters:file_obj – a file-like object to read the config file from
class paramiko.config.SSHConfigDict(*args, **kwargs)

A dictionary wrapper/subclass for per-host configuration structures.

This class introduces some usage niceties for consumers of SSHConfig, specifically around the issue of variable type conversions: normal value access yields strings, but there are now methods such as as_bool and as_int that yield casted values instead.

For example, given the following ssh_config file snippet:

Host foo.example.com
    PasswordAuthentication no
    Compression yes
    ServerAliveInterval 60

the following code highlights how you can access the raw strings as well as usefully Python type-casted versions (recalling that keys are all normalized to lowercase first):

my_config = SSHConfig()
my_config.parse(open('~/.ssh/config'))
conf = my_config.lookup('foo.example.com')

assert conf['passwordauthentication'] == 'no'
assert conf.as_bool('passwordauthentication') is False
assert conf['compression'] == 'yes'
assert conf.as_bool('compression') is True
assert conf['serveraliveinterval'] == '60'
assert conf.as_int('serveraliveinterval') == 60

New in version 2.5.

__weakref__

list of weak references to the object (if defined)

as_bool(key)

Express given key’s value as a boolean type.

Typically, this is used for ssh_config’s pseudo-boolean values which are either "yes" or "no". In such cases, "yes" yields True and any other value becomes False.

Note

If (for whatever reason) the stored value is already boolean in nature, it’s simply returned.

New in version 2.5.

as_int(key)

Express given key’s value as an integer, if possible.

This method will raise ValueError or similar if the value is not int-appropriate, same as the builtin int type.

New in version 2.5.