x/cloud-init
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c3c7b26690cb815da64bdf59e84eaa2d0480d0f2
cloud-init/cloudinit/ssh_util.py
Barry Warsaw 474b7f259d Largely merge lp:~harlowja/cloud-init/py2-3 albeit manually because it seemed 
to be behind trunk.

`tox -e py27` passes full test suite.  Now to work on replacing mocker.
2015-01-21 17:56:53 -05:00

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#!/usr/bin/python
# vi: ts=4 expandtab
#
# Copyright (C) 2012 Canonical Ltd.
# Copyright (C) 2012 Hewlett-Packard Development Company, L.P.
#
# Author: Scott Moser <scott.moser@canonical.com>
# Author: Juerg Hafliger <juerg.haefliger@hp.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 3, as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import os
import pwd
from cloudinit import log as logging
from cloudinit import util
LOG = logging.getLogger(__name__)
# See: man sshd_config
DEF_SSHD_CFG = "/etc/ssh/sshd_config"
# taken from openssh source key.c/key_type_from_name
VALID_KEY_TYPES = ("rsa", "dsa", "ssh-rsa", "ssh-dss", "ecdsa",
"ssh-rsa-cert-v00@openssh.com", "ssh-dss-cert-v00@openssh.com",
"ssh-rsa-cert-v00@openssh.com", "ssh-dss-cert-v00@openssh.com",
"ssh-rsa-cert-v01@openssh.com", "ssh-dss-cert-v01@openssh.com",
"ecdsa-sha2-nistp256-cert-v01@openssh.com",
"ecdsa-sha2-nistp384-cert-v01@openssh.com",
"ecdsa-sha2-nistp521-cert-v01@openssh.com")
class AuthKeyLine(object):
def __init__(self, source, keytype=None, base64=None,
comment=None, options=None):
self.base64 = base64
self.comment = comment
self.options = options
self.keytype = keytype
self.source = source
def valid(self):
return (self.base64 and self.keytype)
def __str__(self):
toks = []
if self.options:
toks.append(self.options)
if self.keytype:
toks.append(self.keytype)
if self.base64:
toks.append(self.base64)
if self.comment:
toks.append(self.comment)
if not toks:
return self.source
else:
return ' '.join(toks)
class AuthKeyLineParser(object):
"""
AUTHORIZED_KEYS FILE FORMAT
AuthorizedKeysFile specifies the file containing public keys for public
key authentication; if none is specified, the default is
~/.ssh/authorized_keys. Each line of the file contains one key (empty
(because of the size of the public key encoding) up to a limit of 8 kilo-
bytes, which permits DSA keys up to 8 kilobits and RSA keys up to 16
kilobits. You don't want to type them in; instead, copy the
identity.pub, id_dsa.pub, or the id_rsa.pub file and edit it.
sshd enforces a minimum RSA key modulus size for protocol 1 and protocol
2 keys of 768 bits.
The options (if present) consist of comma-separated option specifica-
tions. No spaces are permitted, except within double quotes. The fol-
lowing option specifications are supported (note that option keywords are
case-insensitive):
"""
def _extract_options(self, ent):
"""
The options (if present) consist of comma-separated option specifica-
tions. No spaces are permitted, except within double quotes.
Note that option keywords are case-insensitive.
"""
quoted = False
i = 0
while (i < len(ent) and
((quoted) or (ent[i] not in (" ", "\t")))):
curc = ent[i]
if i + 1 >= len(ent):
i = i + 1
break
nextc = ent[i + 1]
if curc == "\\" and nextc == '"':
i = i + 1
elif curc == '"':
quoted = not quoted
i = i + 1
options = ent[0:i]
# Return the rest of the string in 'remain'
remain = ent[i:].lstrip()
return (options, remain)
def parse(self, src_line, options=None):
# modeled after opensshes auth2-pubkey.c:user_key_allowed2
line = src_line.rstrip("\r\n")
if line.startswith("#") or line.strip() == '':
return AuthKeyLine(src_line)
def parse_ssh_key(ent):
# return ketype, key, [comment]
toks = ent.split(None, 2)
if len(toks) < 2:
raise TypeError("To few fields: %s" % len(toks))
if toks[0] not in VALID_KEY_TYPES:
raise TypeError("Invalid keytype %s" % toks[0])
# valid key type and 2 or 3 fields:
if len(toks) == 2:
# no comment in line
toks.append("")
return toks
ent = line.strip()
try:
(keytype, base64, comment) = parse_ssh_key(ent)
except TypeError:
(keyopts, remain) = self._extract_options(ent)
if options is None:
options = keyopts
try:
(keytype, base64, comment) = parse_ssh_key(remain)
except TypeError:
return AuthKeyLine(src_line)
return AuthKeyLine(src_line, keytype=keytype, base64=base64,
comment=comment, options=options)
def parse_authorized_keys(fname):
lines = []
try:
if os.path.isfile(fname):
lines = util.load_file(fname).splitlines()
except (IOError, OSError):
util.logexc(LOG, "Error reading lines from %s", fname)
lines = []
parser = AuthKeyLineParser()
contents = []
for line in lines:
contents.append(parser.parse(line))
return contents
def update_authorized_keys(old_entries, keys):
to_add = list(keys)
for i in range(0, len(old_entries)):
ent = old_entries[i]
if not ent.valid():
continue
# Replace those with the same base64
for k in keys:
if not ent.valid():
continue
if k.base64 == ent.base64:
# Replace it with our better one
ent = k
# Don't add it later
if k in to_add:
to_add.remove(k)
old_entries[i] = ent
# Now append any entries we did not match above
for key in to_add:
old_entries.append(key)
# Now format them back to strings...
lines = [str(b) for b in old_entries]
# Ensure it ends with a newline
lines.append('')
return '\n'.join(lines)
def users_ssh_info(username):
pw_ent = pwd.getpwnam(username)
if not pw_ent or not pw_ent.pw_dir:
raise RuntimeError("Unable to get ssh info for user %r" % (username))
return (os.path.join(pw_ent.pw_dir, '.ssh'), pw_ent)
def extract_authorized_keys(username):
(ssh_dir, pw_ent) = users_ssh_info(username)
auth_key_fn = None
with util.SeLinuxGuard(ssh_dir, recursive=True):
try:
# The 'AuthorizedKeysFile' may contain tokens
# of the form %T which are substituted during connection set-up.
# The following tokens are defined: %% is replaced by a literal
# '%', %h is replaced by the home directory of the user being
# authenticated and %u is replaced by the username of that user.
ssh_cfg = parse_ssh_config_map(DEF_SSHD_CFG)
auth_key_fn = ssh_cfg.get("authorizedkeysfile", '').strip()
if not auth_key_fn:
auth_key_fn = "%h/.ssh/authorized_keys"
auth_key_fn = auth_key_fn.replace("%h", pw_ent.pw_dir)
auth_key_fn = auth_key_fn.replace("%u", username)
auth_key_fn = auth_key_fn.replace("%%", '%')
if not auth_key_fn.startswith('/'):
auth_key_fn = os.path.join(pw_ent.pw_dir, auth_key_fn)
except (IOError, OSError):
# Give up and use a default key filename
auth_key_fn = os.path.join(ssh_dir, 'authorized_keys')
util.logexc(LOG, "Failed extracting 'AuthorizedKeysFile' in ssh "
"config from %r, using 'AuthorizedKeysFile' file "
"%r instead", DEF_SSHD_CFG, auth_key_fn)
return (auth_key_fn, parse_authorized_keys(auth_key_fn))
def setup_user_keys(keys, username, options=None):
# Make sure the users .ssh dir is setup accordingly
(ssh_dir, pwent) = users_ssh_info(username)
if not os.path.isdir(ssh_dir):
util.ensure_dir(ssh_dir, mode=0o700)
util.chownbyid(ssh_dir, pwent.pw_uid, pwent.pw_gid)
# Turn the 'update' keys given into actual entries
parser = AuthKeyLineParser()
key_entries = []
for k in keys:
key_entries.append(parser.parse(str(k), options=options))
# Extract the old and make the new
(auth_key_fn, auth_key_entries) = extract_authorized_keys(username)
with util.SeLinuxGuard(ssh_dir, recursive=True):
content = update_authorized_keys(auth_key_entries, key_entries)
util.ensure_dir(os.path.dirname(auth_key_fn), mode=0o700)
util.write_file(auth_key_fn, content, mode=0o600)
util.chownbyid(auth_key_fn, pwent.pw_uid, pwent.pw_gid)
class SshdConfigLine(object):
def __init__(self, line, k=None, v=None):
self.line = line
self._key = k
self.value = v
@property
def key(self):
if self._key is None:
return None
# Keywords are case-insensitive
return self._key.lower()
def __str__(self):
if self._key is None:
return str(self.line)
else:
v = str(self._key)
if self.value:
v += " " + str(self.value)
return v
def parse_ssh_config(fname):
# See: man sshd_config
# The file contains keyword-argument pairs, one per line.
# Lines starting with '#' and empty lines are interpreted as comments.
# Note: key-words are case-insensitive and arguments are case-sensitive
lines = []
if not os.path.isfile(fname):
return lines
for line in util.load_file(fname).splitlines():
line = line.strip()
if not line or line.startswith("#"):
lines.append(SshdConfigLine(line))
continue
try:
key, val = line.split(None, 1)
except ValueError:
key, val = line.split('=', 1)
lines.append(SshdConfigLine(line, key, val))
return lines
def parse_ssh_config_map(fname):
lines = parse_ssh_config(fname)
if not lines:
return {}
ret = {}
for line in lines:
if not line.key:
continue
ret[line.key] = line.value
return ret
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