CasperSecurity
# Copyright (C) 2016 Canonical Ltd.
#
# Author: Scott Moser <scott.moser@canonical.com>
# Author: Christian Ehrhardt <christian.ehrhardt@canonical.com>
#
# This file is part of cloud-init. See LICENSE file for license information.
"""gpg.py - Collection of gpg key related functions"""
import logging
import os
import re
import signal
import time
from tempfile import TemporaryDirectory
from typing import Dict, Optional
from cloudinit import subp
LOG = logging.getLogger(__name__)
HOME = "GNUPGHOME"
class GPG:
def __init__(self):
self.gpg_started = False
self._env = {}
self.temp_dir = TemporaryDirectory()
def __enter__(self):
return self
@property
def env(self) -> Dict[str, str]:
"""when this env property gets invoked, set up our temporary
directory, and also set gpg_started to tell the cleanup()
method whether or not
why put this here and not in __init__? pytest seems unhappy
and it's not obvious how to work around it
"""
if self._env:
return self._env
self.gpg_started = True
self._env = {HOME: self.temp_dir.name}
return self._env
def __exit__(self, exc_typ, exc_value, traceback):
self.cleanup()
def cleanup(self) -> None:
"""cleanup the gpg temporary directory and kill gpg"""
self.kill_gpg()
if self.temp_dir and os.path.isdir(self.temp_dir.name):
self.temp_dir.cleanup()
def export_armour(self, key: str) -> Optional[str]:
"""Export gpg key, armoured key gets returned"""
try:
return subp.subp(
["gpg", "--export", "--armour", key],
capture=True,
update_env=self.env,
).stdout
except subp.ProcessExecutionError as error:
# debug, since it happens for any key not on the system initially
LOG.debug('Failed to export armoured key "%s": %s', key, error)
return None
def dearmor(self, key: str) -> str:
"""Dearmor gpg key, dearmored key gets returned
note: man gpg(1) makes no mention of an --armour spelling, only --armor
"""
return subp.subp(
["gpg", "--dearmor"], data=key, decode=False, update_env=self.env
).stdout
def list_keys(self, key_file: str, human_output=False) -> str:
"""List keys from a keyring with fingerprints. Default to a
stable machine parseable format.
@param key_file: a string containing a filepath to a key
@param human_output: return output intended for human parsing
"""
cmd = [
"gpg",
"--no-options",
"--with-fingerprint",
"--no-default-keyring",
"--list-keys",
"--keyring",
]
if not human_output:
cmd.append("--with-colons")
cmd.append(key_file)
stdout, stderr = subp.subp(cmd, update_env=self.env, capture=True)
if stderr:
LOG.warning(
'Failed to export armoured key "%s": %s', key_file, stderr
)
return stdout
def recv_key(self, key: str, keyserver: str, retries=(1, 1)) -> None:
"""Receive gpg key from the specified keyserver.
Retries are done by default because keyservers can be unreliable.
Additionally, there is no way to determine the difference between
a non-existent key and a failure. In both cases gpg (at least 2.2.4)
exits with status 2 and stderr: "keyserver receive failed: No data"
It is assumed that a key provided to cloud-init exists on the keyserver
so re-trying makes better sense than failing.
@param key: a string key fingerprint (as passed to gpg --recv-keys).
@param keyserver: the keyserver to request keys from.
@param retries: an iterable of sleep lengths for retries.
Use None to indicate no retries."""
LOG.debug("Importing key '%s' from keyserver '%s'", key, keyserver)
trynum = 0
error = None
sleeps = iter(retries or [])
while True:
trynum += 1
try:
subp.subp(
[
"gpg",
"--no-tty",
"--keyserver=%s" % keyserver,
"--recv-keys",
key,
],
capture=True,
update_env=self.env,
)
LOG.debug(
"Imported key '%s' from keyserver '%s' on try %d",
key,
keyserver,
trynum,
)
return
except subp.ProcessExecutionError as e:
error = e
try:
naplen = next(sleeps)
LOG.debug(
"Import failed with exit code %d, will try again in %ss",
error.exit_code,
naplen,
)
time.sleep(naplen)
except StopIteration as e:
raise ValueError(
"Failed to import key '%s' from keyserver '%s' "
"after %d tries: %s" % (key, keyserver, trynum, error)
) from e
def delete_key(self, key: str) -> None:
"""Delete the specified key from the local gpg ring"""
try:
subp.subp(
["gpg", "--batch", "--yes", "--delete-keys", key],
capture=True,
update_env=self.env,
)
except subp.ProcessExecutionError as error:
LOG.warning('Failed delete key "%s": %s', key, error)
def getkeybyid(
self, keyid: str, keyserver: str = "keyserver.ubuntu.com"
) -> Optional[str]:
"""get gpg keyid from keyserver"""
armour = self.export_armour(keyid)
if not armour:
try:
self.recv_key(keyid, keyserver=keyserver)
armour = self.export_armour(keyid)
except ValueError:
LOG.exception("Failed to obtain gpg key %s", keyid)
raise
finally:
# delete just imported key to leave environment as it
# was before
self.delete_key(keyid)
return armour
def kill_gpg(self) -> None:
"""killing with gpgconf is best practice, but when it isn't available
failover is possible
GH: 4344 - stop gpg-agent/dirmgr daemons spawned by gpg
key imports. Daemons spawned by cloud-config.service on systemd
v253 report (running)
"""
try:
if not self.gpg_started:
return
if subp.which("gpgconf"):
gpg_process_out = subp.subp(
["gpgconf", "--kill", "all"],
capture=True,
update_env=self.env,
).stdout
else:
gpg_process_out = subp.subp(
[
"ps",
"-o",
"ppid,pid",
"-C",
"keyboxd",
"-C",
"dirmngr",
"-C",
"gpg-agent",
],
capture=True,
rcs=[0, 1],
).stdout
gpg_pids = re.findall(
r"(?P<ppid>\d+)\s+(?P<pid>\d+)", gpg_process_out
)
root_gpg_pids = [
int(pid[1]) for pid in gpg_pids if pid[0] == "1"
]
if root_gpg_pids:
LOG.debug(
"Killing gpg-agent and dirmngr pids: %s", root_gpg_pids
)
for gpg_pid in root_gpg_pids:
os.kill(gpg_pid, signal.SIGKILL)
except subp.ProcessExecutionError as e:
LOG.warning("Failed to clean up gpg process: %s", e)