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# 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 time
from cloudinit import log as logging
from cloudinit import subp
LOG = logging.getLogger(__name__)
GPG_LIST = [
"gpg",
"--with-fingerprint",
"--no-default-keyring",
"--list-keys",
"--keyring",
]
def export_armour(key):
"""Export gpg key, armoured key gets returned"""
try:
(armour, _) = subp.subp(
["gpg", "--export", "--armour", key], capture=True
)
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)
armour = None
return armour
def dearmor(key):
"""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).stdout
def list(key_file, human_output=False):
"""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 = []
cmd.extend(GPG_LIST)
if not human_output:
cmd.append("--with-colons")
cmd.append(key_file)
(stdout, stderr) = subp.subp(cmd, capture=True)
if stderr:
LOG.warning('Failed to export armoured key "%s": %s', key_file, stderr)
return stdout
def recv_key(key, keyserver, retries=(1, 1)):
"""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-existant 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)
cmd = ["gpg", "--no-tty", "--keyserver=%s" % keyserver, "--recv-keys", key]
if retries is None:
retries = []
trynum = 0
error = None
sleeps = iter(retries)
while True:
trynum += 1
try:
subp.subp(cmd, capture=True)
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(key):
"""Delete the specified key from the local gpg ring"""
try:
subp.subp(
["gpg", "--batch", "--yes", "--delete-keys", key], capture=True
)
except subp.ProcessExecutionError as error:
LOG.warning('Failed delete key "%s": %s', key, error)
def getkeybyid(keyid, keyserver="keyserver.ubuntu.com"):
"""get gpg keyid from keyserver"""
armour = export_armour(keyid)
if not armour:
try:
recv_key(keyid, keyserver=keyserver)
armour = 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
delete_key(keyid)
return armour
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