diff options
Diffstat (limited to 'cloudinit/config/cc_ssh.py')
| -rwxr-xr-x | cloudinit/config/cc_ssh.py | 153 |
1 files changed, 114 insertions, 39 deletions
diff --git a/cloudinit/config/cc_ssh.py b/cloudinit/config/cc_ssh.py index f8f7cb35..163cce99 100755 --- a/cloudinit/config/cc_ssh.py +++ b/cloudinit/config/cc_ssh.py @@ -9,43 +9,23 @@ """ SSH --- -**Summary:** configure ssh and ssh keys +**Summary:** configure SSH and SSH keys (host and authorized) -This module handles most configuration for ssh and ssh keys. Many images have -default ssh keys, which can be removed using ``ssh_deletekeys``. Since removing -default keys is usually the desired behavior this option is enabled by default. +This module handles most configuration for SSH and both host and authorized SSH +keys. -Keys can be added using the ``ssh_keys`` configuration key. The argument to -this config key should be a dictionary entries for the public and private keys -of each desired key type. Entries in the ``ssh_keys`` config dict should -have keys in the format ``<key type>_private`` and ``<key type>_public``, e.g. -``rsa_private: <key>`` and ``rsa_public: <key>``. See below for supported key -types. Not all key types have to be specified, ones left unspecified will not -be used. If this config option is used, then no keys will be generated. +Authorized Keys +^^^^^^^^^^^^^^^ -.. note:: - when specifying private keys in cloud-config, care should be taken to - ensure that the communication between the data source and the instance is - secure +Authorized keys are a list of public SSH keys that are allowed to connect to a +a user account on a system. They are stored in `.ssh/authorized_keys` in that +account's home directory. Authorized keys for the default user defined in +``users`` can be specified using ``ssh_authorized_keys``. Keys +should be specified as a list of public keys. .. note:: - to specify multiline private keys, use yaml multiline syntax - -If no keys are specified using ``ssh_keys``, then keys will be generated using -``ssh-keygen``. By default one public/private pair of each supported key type -will be generated. The key types to generate can be specified using the -``ssh_genkeytypes`` config flag, which accepts a list of key types to use. For -each key type for which this module has been instructed to create a keypair, if -a key of the same type is already present on the system (i.e. if -``ssh_deletekeys`` was false), no key will be generated. - -Supported key types for the ``ssh_keys`` and the ``ssh_genkeytypes`` config -flags are: - - - rsa - - dsa - - ecdsa - - ed25519 + see the ``cc_set_passwords`` module documentation to enable/disable SSH + password authentication Root login can be enabled/disabled using the ``disable_root`` config key. Root login options can be manually specified with ``disable_root_opts``. If @@ -55,13 +35,46 @@ root login is disabled, and root login opts are set to:: no-port-forwarding,no-agent-forwarding,no-X11-forwarding -Authorized keys for the default user/first user defined in ``users`` can be -specified using `ssh_authorized_keys``. Keys should be specified as a list of -public keys. +Host Keys +^^^^^^^^^ + +Host keys are for authenticating a specific instance. Many images have default +host SSH keys, which can be removed using ``ssh_deletekeys``. This prevents +re-use of a private host key from an image on multiple machines. Since +removing default host keys is usually the desired behavior this option is +enabled by default. + +Host keys can be added using the ``ssh_keys`` configuration key. The argument +to this config key should be a dictionary entries for the public and private +keys of each desired key type. Entries in the ``ssh_keys`` config dict should +have keys in the format ``<key type>_private`` and ``<key type>_public``, +e.g. ``rsa_private: <key>`` and ``rsa_public: <key>``. See below for supported +key types. Not all key types have to be specified, ones left unspecified will +not be used. If this config option is used, then no keys will be generated. .. note:: - see the ``cc_set_passwords`` module documentation to enable/disable ssh - password authentication + when specifying private host keys in cloud-config, care should be taken to + ensure that the communication between the data source and the instance is + secure + +.. note:: + to specify multiline private host keys, use yaml multiline syntax + +If no host keys are specified using ``ssh_keys``, then keys will be generated +using ``ssh-keygen``. By default one public/private pair of each supported +host key type will be generated. The key types to generate can be specified +using the ``ssh_genkeytypes`` config flag, which accepts a list of host key +types to use. For each host key type for which this module has been instructed +to create a keypair, if a key of the same type is already present on the +system (i.e. if ``ssh_deletekeys`` was false), no key will be generated. + +Supported host key types for the ``ssh_keys`` and the ``ssh_genkeytypes`` +config flags are: + + - rsa + - dsa + - ecdsa + - ed25519 **Internal name:** ``cc_ssh`` @@ -91,6 +104,10 @@ public keys. ssh_authorized_keys: - ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAGEA3FSyQwBI6Z+nCSjUU ... - ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEA3I7VUf2l5gSn5uavROsc5HRDpZ ... + allow_public_ssh_keys: <true/false> + ssh_publish_hostkeys: + enabled: <true/false> (Defaults to true) + blacklist: <list of key types> (Defaults to [dsa]) """ import glob @@ -104,6 +121,10 @@ from cloudinit import util GENERATE_KEY_NAMES = ['rsa', 'dsa', 'ecdsa', 'ed25519'] KEY_FILE_TPL = '/etc/ssh/ssh_host_%s_key' +PUBLISH_HOST_KEYS = True +# Don't publish the dsa hostkey by default since OpenSSH recommends not using +# it. +HOST_KEY_PUBLISH_BLACKLIST = ['dsa'] CONFIG_KEY_TO_FILE = {} PRIV_TO_PUB = {} @@ -176,6 +197,23 @@ def handle(_name, cfg, cloud, log, _args): util.logexc(log, "Failed generating key type %s to " "file %s", keytype, keyfile) + if "ssh_publish_hostkeys" in cfg: + host_key_blacklist = util.get_cfg_option_list( + cfg["ssh_publish_hostkeys"], "blacklist", + HOST_KEY_PUBLISH_BLACKLIST) + publish_hostkeys = util.get_cfg_option_bool( + cfg["ssh_publish_hostkeys"], "enabled", PUBLISH_HOST_KEYS) + else: + host_key_blacklist = HOST_KEY_PUBLISH_BLACKLIST + publish_hostkeys = PUBLISH_HOST_KEYS + + if publish_hostkeys: + hostkeys = get_public_host_keys(blacklist=host_key_blacklist) + try: + cloud.datasource.publish_host_keys(hostkeys) + except Exception: + util.logexc(log, "Publishing host keys failed!") + try: (users, _groups) = ug_util.normalize_users_groups(cfg, cloud.distro) (user, _user_config) = ug_util.extract_default(users) @@ -183,14 +221,20 @@ def handle(_name, cfg, cloud, log, _args): disable_root_opts = util.get_cfg_option_str(cfg, "disable_root_opts", ssh_util.DISABLE_USER_OPTS) - keys = cloud.get_public_ssh_keys() or [] + keys = [] + if util.get_cfg_option_bool(cfg, 'allow_public_ssh_keys', True): + keys = cloud.get_public_ssh_keys() or [] + else: + log.debug('Skipping import of publish SSH keys per ' + 'config setting: allow_public_ssh_keys=False') + if "ssh_authorized_keys" in cfg: cfgkeys = cfg["ssh_authorized_keys"] keys.extend(cfgkeys) apply_credentials(keys, user, disable_root, disable_root_opts) except Exception: - util.logexc(log, "Applying ssh credentials failed!") + util.logexc(log, "Applying SSH credentials failed!") def apply_credentials(keys, user, disable_root, disable_root_opts): @@ -209,4 +253,35 @@ def apply_credentials(keys, user, disable_root, disable_root_opts): ssh_util.setup_user_keys(keys, 'root', options=key_prefix) + +def get_public_host_keys(blacklist=None): + """Read host keys from /etc/ssh/*.pub files and return them as a list. + + @param blacklist: List of key types to ignore. e.g. ['dsa', 'rsa'] + @returns: List of keys, each formatted as a two-element tuple. + e.g. [('ssh-rsa', 'AAAAB3Nz...'), ('ssh-ed25519', 'AAAAC3Nx...')] + """ + public_key_file_tmpl = '%s.pub' % (KEY_FILE_TPL,) + key_list = [] + blacklist_files = [] + if blacklist: + # Convert blacklist to filenames: + # 'dsa' -> '/etc/ssh/ssh_host_dsa_key.pub' + blacklist_files = [public_key_file_tmpl % (key_type,) + for key_type in blacklist] + # Get list of public key files and filter out blacklisted files. + file_list = [hostfile for hostfile + in glob.glob(public_key_file_tmpl % ('*',)) + if hostfile not in blacklist_files] + + # Read host key files, retrieve first two fields as a tuple and + # append that tuple to key_list. + for file_name in file_list: + file_contents = util.load_file(file_name) + key_data = file_contents.split() + if key_data and len(key_data) > 1: + key_list.append(tuple(key_data[:2])) + return key_list + + # vi: ts=4 expandtab |