d54905ecee
* known_hosts: clarify key format in documentation Add a small clarification to the documentation about the format of the "key" parameter. Should make #664 less of a issue for newcomers. * known_hosts: normalize key entry to simplify input Keys are normalized before comparing input with present keys. This should make it easier to deal with some corner cases, such as having a hashed entry for some host and trying to add it as non-hashed. * known_hosts: allow multiple entries per host In order to support multiple key types and allow the installed ssh version to decide which is more secure, the module now only overwrites an existing entry in known_hosts if the provided key is of the same type. Old keys of different types must be explicitly removed. Setting state to "absent" and providing no key will remove all entries for the host.
278 lines
10 KiB
Python
278 lines
10 KiB
Python
#!/usr/bin/python
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"""
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Ansible module to manage the ssh known_hosts file.
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Copyright(c) 2014, Matthew Vernon <mcv21@cam.ac.uk>
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This module is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This module is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this module. If not, see <http://www.gnu.org/licenses/>.
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"""
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DOCUMENTATION = '''
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---
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module: known_hosts
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short_description: Add or remove a host from the C(known_hosts) file
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description:
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- The M(known_hosts) module lets you add or remove a host keys from the C(known_hosts) file. Multiple entries per host are allowed, but only one for each key type supported by ssh.
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This is useful if you're going to want to use the M(git) module over ssh, for example.
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If you have a very large number of host keys to manage, you will find the M(template) module more useful.
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version_added: "1.9"
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options:
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name:
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aliases: [ 'host' ]
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description:
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- The host to add or remove (must match a host specified in key)
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required: true
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default: null
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key:
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description:
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- 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). The key must be in the right format for ssh (see ssh(1), section "SSH_KNOWN_HOSTS FILE FORMAT")
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required: false
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default: null
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path:
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description:
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- The known_hosts file to edit
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required: no
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default: "(homedir)+/.ssh/known_hosts"
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state:
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description:
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- I(present) to add the host key, I(absent) to remove it.
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choices: [ "present", "absent" ]
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required: no
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default: present
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requirements: [ ]
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author: "Matthew Vernon (@mcv21)"
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'''
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EXAMPLES = '''
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# Example using with_file to set the system known_hosts file
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- name: tell the host about our servers it might want to ssh to
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known_hosts: path='/etc/ssh/ssh_known_hosts'
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name='foo.com.invalid'
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key="{{ lookup('file', 'pubkeys/foo.com.invalid') }}"
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'''
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# Makes sure public host keys are present or absent in the given known_hosts
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# file.
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#
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# Arguments
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# =========
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# name = hostname whose key should be added (alias: host)
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# key = line(s) to add to known_hosts file
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# path = the known_hosts file to edit (default: ~/.ssh/known_hosts)
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# state = absent|present (default: present)
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import os
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import os.path
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import tempfile
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import errno
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import re
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def enforce_state(module, params):
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"""
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Add or remove key.
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"""
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host = params["name"]
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key = params.get("key",None)
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port = params.get("port",None)
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path = params.get("path")
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state = params.get("state")
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#Find the ssh-keygen binary
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sshkeygen = module.get_bin_path("ssh-keygen",True)
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# Trailing newline in files gets lost, so re-add if necessary
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if key and key[-1] != '\n':
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key+='\n'
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if key is None and state != "absent":
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module.fail_json(msg="No key specified when adding a host")
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sanity_check(module,host,key,sshkeygen)
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found,replace_or_add,found_line=search_for_host_key(module,host,key,path,sshkeygen)
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#We will change state if found==True & state!="present"
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#or found==False & state=="present"
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#i.e found XOR (state=="present")
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#Alternatively, if replace is true (i.e. key present, and we must change it)
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if module.check_mode:
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module.exit_json(changed = replace_or_add or (state=="present") != found)
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#Now do the work.
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#Only remove whole host if found and no key provided
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if found and key is None and state=="absent":
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module.run_command([sshkeygen,'-R',host,'-f',path], check_rc=True)
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params['changed'] = True
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#Next, add a new (or replacing) entry
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if replace_or_add or found != (state=="present"):
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try:
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inf=open(path,"r")
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except IOError, e:
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if e.errno == errno.ENOENT:
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inf=None
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else:
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module.fail_json(msg="Failed to read %s: %s" % \
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(path,str(e)))
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try:
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outf=tempfile.NamedTemporaryFile(dir=os.path.dirname(path))
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if inf is not None:
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for line_number, line in enumerate(inf, start=1):
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if found_line==line_number and (replace_or_add or state=='absent'):
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continue # skip this line to replace its key
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outf.write(line)
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inf.close()
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if state == 'present':
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outf.write(key)
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outf.flush()
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module.atomic_move(outf.name,path)
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except (IOError,OSError),e:
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module.fail_json(msg="Failed to write to file %s: %s" % \
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(path,str(e)))
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try:
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outf.close()
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except:
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pass
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params['changed'] = True
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return params
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def sanity_check(module,host,key,sshkeygen):
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'''Check supplied key is sensible
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host and key are parameters provided by the user; If the host
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provided is inconsistent with the key supplied, then this function
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quits, providing an error to the user.
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sshkeygen is the path to ssh-keygen, found earlier with get_bin_path
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'''
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#If no key supplied, we're doing a removal, and have nothing to check here.
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if key is None:
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return
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#Rather than parsing the key ourselves, get ssh-keygen to do it
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#(this is essential for hashed keys, but otherwise useful, as the
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#key question is whether ssh-keygen thinks the key matches the host).
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#The approach is to write the key to a temporary file,
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#and then attempt to look up the specified host in that file.
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try:
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outf=tempfile.NamedTemporaryFile()
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outf.write(key)
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outf.flush()
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except IOError,e:
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module.fail_json(msg="Failed to write to temporary file %s: %s" % \
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(outf.name,str(e)))
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rc,stdout,stderr=module.run_command([sshkeygen,'-F',host,
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'-f',outf.name],
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check_rc=True)
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try:
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outf.close()
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except:
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pass
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if stdout=='': #host not found
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module.fail_json(msg="Host parameter does not match hashed host field in supplied key")
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def search_for_host_key(module,host,key,path,sshkeygen):
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'''search_for_host_key(module,host,key,path,sshkeygen) -> (found,replace_or_add,found_line)
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Looks up host and keytype in the known_hosts file path; if it's there, looks to see
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if one of those entries matches key. Returns:
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found (Boolean): is host found in path?
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replace_or_add (Boolean): is the key in path different to that supplied by user?
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found_line (int or None): the line where a key of the same type was found
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if found=False, then replace is always False.
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sshkeygen is the path to ssh-keygen, found earlier with get_bin_path
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'''
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if os.path.exists(path)==False:
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return False, False, None
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#openssh >=6.4 has changed ssh-keygen behaviour such that it returns
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#1 if no host is found, whereas previously it returned 0
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rc,stdout,stderr=module.run_command([sshkeygen,'-F',host,'-f',path],
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check_rc=False)
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if stdout=='' and stderr=='' and (rc==0 or rc==1):
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return False, False, None #host not found, no other errors
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if rc!=0: #something went wrong
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module.fail_json(msg="ssh-keygen failed (rc=%d,stdout='%s',stderr='%s')" % (rc,stdout,stderr))
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#If user supplied no key, we don't want to try and replace anything with it
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if key is None:
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return True, False, None
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lines=stdout.split('\n')
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new_key = normalize_known_hosts_key(key, host)
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for l in lines:
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if l=='':
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continue
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elif l[0]=='#': # info output from ssh-keygen; contains the line number where key was found
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try:
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# This output format has been hardcoded in ssh-keygen since at least OpenSSH 4.0
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# It always outputs the non-localized comment before the found key
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found_line = int(re.search(r'found: line (\d+)', l).group(1))
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except IndexError, e:
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module.fail_json(msg="failed to parse output of ssh-keygen for line number: '%s'" % l)
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else:
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found_key = normalize_known_hosts_key(l,host)
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if new_key==found_key: #found a match
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return True, False, found_line #found exactly the same key, don't replace
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elif new_key['type'] == found_key['type']: # found a different key for the same key type
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return True, True, found_line
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#No match found, return found and replace, but no line
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return True, True, None
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def normalize_known_hosts_key(key, host):
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'''
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Transform a key, either taken from a known_host file or provided by the
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user, into a normalized form.
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The host part (which might include multiple hostnames or be hashed) gets
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replaced by the provided host. Also, any spurious information gets removed
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from the end (like the username@host tag usually present in hostkeys, but
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absent in known_hosts files)
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'''
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k=key.strip() #trim trailing newline
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k=key.split()
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d = dict()
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#The optional "marker" field, used for @cert-authority or @revoked
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if k[0][0] == '@':
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d['options'] = k[0]
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d['host']=host
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d['type']=k[2]
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d['key']=k[3]
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else:
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d['host']=host
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d['type']=k[1]
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d['key']=k[2]
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return d
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def main():
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module = AnsibleModule(
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argument_spec = dict(
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name = dict(required=True, type='str', aliases=['host']),
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key = dict(required=False, type='str'),
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path = dict(default="~/.ssh/known_hosts", type='path'),
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state = dict(default='present', choices=['absent','present']),
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),
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supports_check_mode = True
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)
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results = enforce_state(module,module.params)
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module.exit_json(**results)
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# import module snippets
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from ansible.module_utils.basic import *
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main()
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