ansible/library/system/authorized_key

#!/usr/bin/python
# -*- coding: utf-8 -*-

"""
Ansible module to add authorized_keys for ssh logins.
(c) 2012, Brad Olson <brado@movedbylight.com>

This file is part of Ansible

Ansible is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Ansible is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
"""

DOCUMENTATION = '''
---
module: authorized_key
short_description: Adds or removes an SSH authorized key
description:
     - Adds or removes an SSH authorized key for a user from a remote host.
version_added: "0.5"
options:
  user:
    description:
      - The username on the remote host whose authorized_keys file will be modified
    required: true
    default: null
    aliases: []
  key:
    description:
      - The SSH public key, as a string
    required: true
    default: null
  path:
    description:
      - Alternate path to the authorized_keys file
    required: false
    default: "(homedir)+/.ssh/authorized_keys"
    version_added: "1.2"
  manage_dir:
    description:
      - Whether this module should manage the directory of the authorized_keys file. Make sure to set C(manage_dir=no) if you are using an alternate directory for authorized_keys set with C(path), since you could lock yourself out of SSH access. See the example below.
    required: false
    choices: [ "yes", "no" ]
    default: "yes"
    version_added: "1.2"
  state:
    description:
      - Whether the given key (with the given key_options) should or should not be in the file
    required: false
    choices: [ "present", "absent" ]
    default: "present"
  key_options:
    description:
      - A string of ssh key options to be prepended to the key in the authorized_keys file
    required: false
    default: null
    version_added: "1.4"
description:
    - "Adds or removes authorized keys for particular user accounts"
author: Brad Olson
'''

EXAMPLES = '''
# Example using key data from a local file on the management machine
- authorized_key: user=charlie key="{{ lookup('file', '/home/charlie/.ssh/id_rsa.pub') }}"

# Using alternate directory locations:
- authorized_key: user=charlie
                  key="{{ lookup('file', '/home/charlie/.ssh/id_rsa.pub') }}"
                  path='/etc/ssh/authorized_keys/charlie'
                  manage_dir=no

# Using with_file
- name: Set up authorized_keys for the deploy user
  authorized_key: user=deploy
                  key="{{ item }}"
  with_file:
    - public_keys/doe-jane
    - public_keys/doe-john

# Using key_options:
- authorized_key: user=charlie
                  key="{{ lookup('file', '/home/charlie/.ssh/id_rsa.pub') }}"
                  key_options='no-port-forwarding,host="10.0.1.1"'
'''

# Makes sure the public key line is present or absent in the user's .ssh/authorized_keys.
#
# Arguments
# =========
#    user = username
#    key = line to add to authorized_keys for user
#    path = path to the user's authorized_keys file (default: ~/.ssh/authorized_keys)
#    manage_dir = whether to create, and control ownership of the directory (default: true)
#    state = absent|present (default: present)
#
# see example in examples/playbooks

import sys
import os
import pwd
import os.path
import tempfile
import re
import shlex

class keydict(dict):

    """ a dictionary that maintains the order of keys as they are added """
    
    # http://stackoverflow.com/questions/2328235/pythonextend-the-dict-class

    def __init__(self, *args, **kw):
        super(keydict,self).__init__(*args, **kw)
        self.itemlist = super(keydict,self).keys()
    def __setitem__(self, key, value):
        self.itemlist.append(key)
        super(keydict,self).__setitem__(key, value)        
    def __iter__(self):
        return iter(self.itemlist)
    def keys(self):
        return self.itemlist
    def values(self):
        return [self[key] for key in self]
    def itervalues(self):
        return (self[key] for key in self)    

def keyfile(module, user, write=False, path=None, manage_dir=True):
    """
    Calculate name of authorized keys file, optionally creating the
    directories and file, properly setting permissions.

    :param str user: name of user in passwd file
    :param bool write: if True, write changes to authorized_keys file (creating directories if needed)
    :param str path: if not None, use provided path rather than default of '~user/.ssh/authorized_keys'
    :param bool manage_dir: if True, create and set ownership of the parent dir of the authorized_keys file
    :return: full path string to authorized_keys for user
    """

    try:
        user_entry = pwd.getpwnam(user)
    except KeyError, e:
        module.fail_json(msg="Failed to lookup user %s: %s" % (user, str(e)))
    if path is None:
        homedir    = user_entry.pw_dir
        sshdir     = os.path.join(homedir, ".ssh")
        keysfile   = os.path.join(sshdir, "authorized_keys")
    else:
        sshdir     = os.path.dirname(path)
        keysfile   = path

    if not write:
        return keysfile

    uid = user_entry.pw_uid
    gid = user_entry.pw_gid

    if manage_dir:
        if not os.path.exists(sshdir):
            os.mkdir(sshdir, 0700)
            if module.selinux_enabled():
                module.set_default_selinux_context(sshdir, False)
        os.chown(sshdir, uid, gid)
        os.chmod(sshdir, 0700)

    if not os.path.exists(keysfile):
        basedir = os.path.dirname(keysfile)
        if not os.path.exists(basedir):
            os.makedirs(basedir)
        try:
            f = open(keysfile, "w") #touches file so we can set ownership and perms
        finally:
            f.close()
        if module.selinux_enabled():
            module.set_default_selinux_context(keysfile, False)

    try:
        os.chown(keysfile, uid, gid)
        os.chmod(keysfile, 0600)
    except OSError:
        pass

    return keysfile

def parseoptions(module, options):
    ''' 
    reads a string containing ssh-key options 
    and returns a dictionary of those options
    '''
    options_dict = keydict() #ordered dict
    if options:
        token_exp = [
            # matches separator
            (r',+', False),
            # matches option with value, e.g. from="x,y"
            (r'([a-z0-9-]+)="((?:[^"\\]|\\.)*)"', True),
            # matches single option, e.g. no-agent-forwarding 
            (r'[a-z0-9-]+', True)
        ]

        pos = 0
        while pos < len(options):
            match = None
            for pattern, is_valid_option in token_exp:
                regex = re.compile(pattern, re.IGNORECASE)
                match = regex.match(options, pos)
                if match:
                    text = match.group(0)
                    if is_valid_option:
                        if len(match.groups()) == 2:
                            options_dict[match.group(1)] = match.group(2)
                        else:
                            options_dict[text] = None
                    break
            if not match:
                module.fail_json(msg="invalid option string: %s" % options)
            else:
                pos = match.end(0)

    return options_dict

def parsekey(module, raw_key):
    '''
    parses a key, which may or may not contain a list
    of ssh-key options at the beginning
    '''

    VALID_SSH2_KEY_TYPES = [
        'ssh-ed25519',
        'ecdsa-sha2-nistp256',
        'ecdsa-sha2-nistp384',
        'ecdsa-sha2-nistp521', 
        'ssh-dss',
        'ssh-rsa',
    ]

    options    = None   # connection options
    key        = None   # encrypted key string
    key_type   = None   # type of ssh key
    type_index = None   # index of keytype in key string|list

    # remove comment yaml escapes
    raw_key = raw_key.replace('\#', '#')

    # split key safely
    lex = shlex.shlex(raw_key)
    lex.quotes = ["'", '"']
    lex.commenters = '' #keep comment hashes
    lex.whitespace_split = True
    key_parts = list(lex)

    for i in range(0, len(key_parts)):
        if key_parts[i] in VALID_SSH2_KEY_TYPES:
            type_index = i
            key_type = key_parts[i]
            break

    # check for options
    if type_index is None:
        return None
    elif type_index > 0:
        options = " ".join(key_parts[:type_index])

    # parse the options (if any)
    options = parseoptions(module, options)

    # get key after the type index
    key = key_parts[(type_index + 1)]

    # set comment to everything after the key
    if len(key_parts) > (type_index + 1):
        comment = " ".join(key_parts[(type_index + 2):])

    return (key, key_type, options, comment)

def readkeys(module, filename):

    if not os.path.isfile(filename):
        return {}

    keys = {}
    f = open(filename)
    for line in f.readlines():
        key_data = parsekey(module, line)
        if key_data:
            # use key as identifier
            keys[key_data[0]] = key_data
        else:
            # for an invalid line, just append the line
            # to the array so it will be re-output later
            keys[line] = line
    f.close()
    return keys

def writekeys(module, filename, keys):

    fd, tmp_path = tempfile.mkstemp('', 'tmp', os.path.dirname(filename))
    f = open(tmp_path,"w")
    try:
        for index, key in keys.items():
            try:
                (keyhash,type,options,comment) = key
                option_str = ""
                if options:
                    option_strings = []
                    for option_key in options.keys():
                        if options[option_key]:
                            option_strings.append("%s=\"%s\"" % (option_key, options[option_key]))
                        else:
                            option_strings.append("%s" % option_key)

                    option_str = ",".join(option_strings)
                    option_str += " "
                key_line = "%s%s %s %s\n" % (option_str, type, keyhash, comment)
            except:
                key_line = key
            f.writelines(key_line)
    except IOError, e:
        module.fail_json(msg="Failed to write to file %s: %s" % (tmp_path, str(e)))
    f.close()
    module.atomic_move(tmp_path, filename)

def enforce_state(module, params):
    """
    Add or remove key.
    """

    user        = params["user"]
    key         = params["key"]
    path        = params.get("path", None)
    manage_dir  = params.get("manage_dir", True)
    state       = params.get("state", "present")
    key_options = params.get("key_options", None)

    # extract indivial keys into an array, skipping blank lines and comments
    key = [s for s in key.splitlines() if s and not s.startswith('#')]


    # check current state -- just get the filename, don't create file
    do_write = False
    params["keyfile"] = keyfile(module, user, do_write, path, manage_dir)
    existing_keys = readkeys(module, params["keyfile"])

    # Check our new keys, if any of them exist we'll continue.
    for new_key in key:
        parsed_new_key = parsekey(module, new_key)
        if key_options is not None:
            parsed_options = parseoptions(module, key_options)
            parsed_new_key = (parsed_new_key[0], parsed_new_key[1], parsed_options, parsed_new_key[3])

        if not parsed_new_key:
            module.fail_json(msg="invalid key specified: %s" % new_key)

        present = False
        matched = False
        non_matching_keys = []

        if parsed_new_key[0] in existing_keys:
            present = True
            # Then we check if everything matches, including
            # the key type and options. If not, we append this
            # existing key to the non-matching list
            # We only want it to match everything when the state
            # is present
            if parsed_new_key != existing_keys[parsed_new_key[0]] and state == "present":
                non_matching_keys.append(existing_keys[parsed_new_key[0]])
            else:
                matched = True


        # handle idempotent state=present
        if state=="present":
            if len(non_matching_keys) > 0:
                for non_matching_key in non_matching_keys:
                    if non_matching_key[0] in existing_keys:
                        del existing_keys[non_matching_key[0]]
                        do_write = True

            if not matched:
                existing_keys[parsed_new_key[0]] = parsed_new_key
                do_write = True

        elif state=="absent":
            if not matched:
                continue
            del existing_keys[parsed_new_key[0]]
            do_write = True

    if do_write:
        writekeys(module, keyfile(module, user, do_write, path, manage_dir), existing_keys)
        params['changed'] = True

    return params

def main():

    module = AnsibleModule(
        argument_spec = dict(
           user        = dict(required=True, type='str'),
           key         = dict(required=True, type='str'),
           path        = dict(required=False, type='str'),
           manage_dir  = dict(required=False, type='bool', default=True),
           state       = dict(default='present', choices=['absent','present']),
           key_options = dict(required=False, type='str'),
           unique      = dict(default=False, type='bool'),
        )
    )

    results = enforce_state(module, module.params)
    module.exit_json(**results)

# import module snippets
from ansible.module_utils.basic import *
main()