#!/usr/bin/python """ Ansible module to manage the ssh known_hosts file. Copyright(c) 2014, Matthew Vernon This module 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. This module 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 this module. If not, see . """ DOCUMENTATION = ''' --- module: known_hosts short_description: Add or remove a host from the C(known_hosts) file description: - The M(known_hosts) module lets you add or remove a host from the C(known_hosts) file. This is useful if you're going to want to use the M(git) module over ssh, for example. If you have a very large number of host keys to manage, you will find the M(template) module more useful. version_added: "1.6" options: name: aliases: [ 'host' ] description: - The host to add or remove (must match a host specified in key) required: true default: null key: description: - The SSH public host key, as a string (required if state=present, optional when state=absent, in which case all keys for the host are removed) required: false default: null path: description: - The known_hosts file to edit required: no default: "(homedir)+/.ssh/known_hosts" state: description: - I(present) to add the host, I(absent) to remove it. choices: [ "present", "absent" ] required: no default: present requirements: [ ] author: Matthew Vernon ''' EXAMPLES = ''' # Example using with_file to set the system known_hosts file - name: tell the host about our servers it might want to ssh to known_hosts: path='/etc/ssh/ssh_known_hosts' host='foo.com.invalid' key="{{ lookup('file', 'pubkeys/foo.com.invalid') }}" ''' # Makes sure public host keys are present or absent in the given known_hosts # file. # # Arguments # ========= # name = hostname whose key should be added (alias: host) # key = line(s) to add to known_hosts file # path = the known_hosts file to edit (default: ~/.ssh/known_hosts) # state = absent|present (default: present) import os import os.path import tempfile import errno def enforce_state(module, params): """ Add or remove key. """ host = params["host"] key = params.get("key",None) port = params.get("port",None) #expand the path parameter; otherwise module.add_path_info #(called by exit_json) unhelpfully says the unexpanded path is absent. path = os.path.expanduser(params.get("path")) state = params.get("state") #Find the ssh-keygen binary sshkeygen = module.get_bin_path("ssh-keygen",True) #trailing newline in files gets lost, so re-add if necessary if key is not None and key[-1]!='\n': key+='\n' if key is None and state != "absent": module.fail_json(msg="No key specified when adding a host") sanity_check(module,host,key,sshkeygen) current,replace=search_for_host_key(module,host,key,path,sshkeygen) #We will change state if current==True & state!="present" #or current==False & state=="present" #i.e (current) XOR (state=="present") #Alternatively, if replace is true (i.e. key present, and we must change it) if module.check_mode: module.exit_json(changed = replace or ((state=="present") != current)) #Now do the work. #First, remove an extant entry if required if replace==True or (current==True and state=="absent"): module.run_command([sshkeygen,'-R',host,'-f',path], check_rc=True) params['changed'] = True #Next, add a new (or replacing) entry if replace==True or (current==False and state=="present"): try: inf=open(path,"r") except IOError, e: if e.errno == errno.ENOENT: inf=None else: module.fail_json(msg="Failed to read %s: %s" % \ (path,str(e))) try: outf=tempfile.NamedTemporaryFile(dir=os.path.dirname(path), delete=False) if inf is not None: for line in inf: outf.write(line) inf.close() outf.write(key) outf.close() module.atomic_move(outf.name,path) except IOError,e: module.fail_json(msg="Failed to write to file %s: %s" % \ (path,str(e))) params['changed'] = True return params def sanity_check(module,host,key,sshkeygen): '''Check supplied key is sensible host and key are parameters provided by the user; If the host provided is inconsistent with the key supplied, then this function quits, providing an error to the user. sshkeygen is the path to ssh-keygen, found earlier with get_bin_path ''' #If no key supplied, we're doing a removal, and have nothing to check here. if key is None: return #Rather than parsing the key ourselves, get ssh-keygen to do it #(this is essential for hashed keys, but otherwise useful, as the #key question is whether ssh-keygen thinks the key matches the host). #The approach is to write the key to a temporary file, #and then attempt to look up the specified host in that file. try: outf=tempfile.NamedTemporaryFile(delete=False) outf.write(key) outf.close() except IOError,e: module.fail_json(msg="Failed to write to temporary file %s: %s" % \ (outf.name,str(e))) rc,stdout,stderr=module.run_command([sshkeygen,'-F',host, '-f',outf.name], check_rc=True) os.remove(outf.name) if stdout=='': #host not found module.fail_json(msg="Host parameter does not match hashed host field in supplied key") def search_for_host_key(module,host,key,path,sshkeygen): '''search_for_host_key(module,host,key,path,sshkeygen) -> (current,replace) Looks up host in the known_hosts file path; if it's there, looks to see if one of those entries matches key. Returns: current (Boolean): is host found in path? replace (Boolean): is the key in path different to that supplied by user? if current=False, then replace is always False. sshkeygen is the path to ssh-keygen, found earlier with get_bin_path ''' replace=False if os.path.exists(path)==False: return False, False rc,stdout,stderr=module.run_command([sshkeygen,'-F',host,'-f',path], check_rc=True) if stdout=='': #host not found return False, False #If user supplied no key, we don't want to try and replace anything with it if key is None: return True, False lines=stdout.split('\n') k=key.strip() #trim trailing newline #ssh-keygen returns only the host we ask about in the host field, #even if the key entry has multiple hosts. Emulate this behaviour here, #otherwise we get false negatives. #Only necessary for unhashed entries. if k[0] !='|': k=k.split() #The optional "marker" field, used for @cert-authority or @revoked if k[0][0] == '@': k[1]=host else: k[0]=host k=' '.join(k) for l in lines: if l=='': continue if l[0]=='#': #comment continue if k==l: #found a match return True, False #current, not-replace #No match found, return current and replace return True, True def main(): module = AnsibleModule( argument_spec = dict( name = dict(required=True, type='str', aliases=['host']), key = dict(required=False, type='str'), path = dict(default="~/.ssh/known_hosts", type='str'), state = dict(default='present', choices=['absent','present']), ), supports_check_mode = True ) results = enforce_state(module,module.params) module.exit_json(**results) # import module snippets from ansible.module_utils.basic import * main()