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# Copyright (C) 2012 Yahoo! Inc.
#
# Author: Joshua Harlow <harlowja@yahoo-inc.com>
#
# This file is part of cloud-init. See LICENSE file for license information.
"""SSH AuthKey Fingerprints: Log fingerprints of user SSH keys"""
import base64
import hashlib
from logging import Logger
from cloudinit import ssh_util, util
from cloudinit.cloud import Cloud
from cloudinit.config import Config
from cloudinit.config.schema import MetaSchema, get_meta_doc
from cloudinit.distros import ALL_DISTROS, ug_util
from cloudinit.settings import PER_INSTANCE
from cloudinit.simpletable import SimpleTable
MODULE_DESCRIPTION = """\
Write fingerprints of authorized keys for each user to log. This is enabled by
default, but can be disabled using ``no_ssh_fingerprints``. The hash type for
the keys can be specified, but defaults to ``sha256``.
"""
meta: MetaSchema = {
"id": "cc_ssh_authkey_fingerprints",
"name": "SSH AuthKey Fingerprints",
"title": "Log fingerprints of user SSH keys",
"description": MODULE_DESCRIPTION,
"distros": [ALL_DISTROS],
"frequency": PER_INSTANCE,
"examples": [
"no_ssh_fingerprints: true",
"authkey_hash: sha512",
],
"activate_by_schema_keys": [],
}
__doc__ = get_meta_doc(meta)
def _split_hash(bin_hash):
split_up = []
for i in range(0, len(bin_hash), 2):
split_up.append(bin_hash[i : i + 2])
return split_up
def _gen_fingerprint(b64_text, hash_meth="sha256"):
if not b64_text:
return ""
# TBD(harlowja): Maybe we should feed this into 'ssh -lf'?
try:
hasher = hashlib.new(hash_meth)
hasher.update(base64.b64decode(b64_text))
return ":".join(_split_hash(hasher.hexdigest()))
except (TypeError, ValueError):
# Raised when b64 not really b64...
# or when the hash type is not really
# a known/supported hash type...
return "?"
def _is_printable_key(entry):
if any([entry.keytype, entry.base64, entry.comment, entry.options]):
if (
entry.keytype
and entry.keytype.lower().strip() in ssh_util.VALID_KEY_TYPES
):
return True
return False
def _pprint_key_entries(
user, key_fn, key_entries, hash_meth="sha256", prefix="ci-info: "
):
if not key_entries:
message = (
"%sno authorized SSH keys fingerprints found for user %s.\n"
% (prefix, user)
)
util.multi_log(message, console=True, stderr=False)
return
tbl_fields = [
"Keytype",
"Fingerprint (%s)" % (hash_meth),
"Options",
"Comment",
]
tbl = SimpleTable(tbl_fields)
for entry in key_entries:
if _is_printable_key(entry):
row = [
entry.keytype or "-",
_gen_fingerprint(entry.base64, hash_meth) or "-",
entry.options or "-",
entry.comment or "-",
]
tbl.add_row(row)
authtbl_s = tbl.get_string()
authtbl_lines = authtbl_s.splitlines()
max_len = len(max(authtbl_lines, key=len))
lines = [
util.center(
"Authorized keys from %s for user %s" % (key_fn, user),
"+",
max_len,
),
]
lines.extend(authtbl_lines)
for line in lines:
util.multi_log(
text="%s%s\n" % (prefix, line), stderr=False, console=True
)
def handle(
name: str, cfg: Config, cloud: Cloud, log: Logger, args: list
) -> None:
if util.is_true(cfg.get("no_ssh_fingerprints", False)):
log.debug(
"Skipping module named %s, logging of SSH fingerprints disabled",
name,
)
return
hash_meth = util.get_cfg_option_str(cfg, "authkey_hash", "sha256")
(users, _groups) = ug_util.normalize_users_groups(cfg, cloud.distro)
for (user_name, _cfg) in users.items():
if _cfg.get("no_create_home") or _cfg.get("system"):
log.debug(
"Skipping printing of ssh fingerprints for user '%s' because "
"no home directory is created",
user_name,
)
continue
(key_fn, key_entries) = ssh_util.extract_authorized_keys(user_name)
_pprint_key_entries(user_name, key_fn, key_entries, hash_meth)
# vi: ts=4 expandtab
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