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remote.py
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# Copyright 2019 VyOS maintainers and contributors <maintainers@vyos.io>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library. If not, see <http://www.gnu.org/licenses/>.
import sys
import os
import re
import fileinput
from vyos.util import cmd
from vyos.util import DEVNULL
def check_and_add_host_key(host_name):
"""
Filter host keys and prompt for adding key to known_hosts file, if
needed.
"""
known_hosts = '{}/.ssh/known_hosts'.format(os.getenv('HOME'))
if not os.path.exists(known_hosts):
mode = 0o600
os.mknod(known_hosts, 0o600)
keyscan_cmd = 'ssh-keyscan -t rsa {}'.format(host_name)
try:
host_key = cmd(keyscan_cmd, stderr=DEVNULL)
except OSError:
sys.exit("Can not get RSA host key")
# libssh2 (jessie; stretch) does not recognize ec host keys, and curl
# will fail with error 51 if present in known_hosts file; limit to rsa.
usable_keys = False
offending_keys = []
for line in fileinput.input(known_hosts, inplace=True):
if host_name in line and 'ssh-rsa' in line:
if line.split()[-1] != host_key.split()[-1]:
offending_keys.append(line)
continue
else:
usable_keys = True
if host_name in line and not 'ssh-rsa' in line:
continue
sys.stdout.write(line)
if usable_keys:
return
if offending_keys:
print("Host key has changed!")
print("If you trust the host key fingerprint below, continue.")
fingerprint_cmd = 'ssh-keygen -lf /dev/stdin'
try:
fingerprint = cmd(fingerprint_cmd, stderr=DEVNULL, input=host_key)
except OSError:
sys.exit("Can not get RSA host key fingerprint.")
print("RSA host key fingerprint is {}".format(fingerprint.split()[1]))
response = input("Do you trust this host? [y]/n ")
if not response or response == 'y':
with open(known_hosts, 'a+') as f:
print("Adding {} to the list of known"
" hosts.".format(host_name))
f.write(host_key)
else:
sys.exit("Host not trusted")
def get_remote_config(remote_file):
""" Invoke curl to download remote (config) file.
Args:
remote file URI:
scp://<user>[:<passwd>]@<host>/<file>
sftp://<user>[:<passwd>]@<host>/<file>
http://<host>/<file>
https://<host>/<file>
ftp://<user>[:<passwd>]@<host>/<file>
tftp://<host>/<file>
"""
request = dict.fromkeys(['protocol', 'user', 'host', 'file'])
protocols = ['scp', 'sftp', 'http', 'https', 'ftp', 'tftp']
or_protocols = '|'.join(protocols)
request_match = re.match(r'(' + or_protocols + r')://(.*?)(/.*)',
remote_file)
if request_match:
(request['protocol'], request['host'],
request['file']) = request_match.groups()
else:
print("Malformed URI")
sys.exit(1)
user_match = re.search(r'(.*)@(.*)', request['host'])
if user_match:
request['user'] = user_match.groups()[0]
request['host'] = user_match.groups()[1]
remote_file = '{0}://{1}{2}'.format(request['protocol'], request['host'], request['file'])
if request['protocol'] in ('scp', 'sftp'):
check_and_add_host_key(request['host'])
redirect_opt = ''
if request['protocol'] in ('http', 'https'):
redirect_opt = '-L'
# Try header first, and look for 'OK' or 'Moved' codes:
curl_cmd = 'curl {0} -q -I {1}'.format(redirect_opt, remote_file)
try:
curl_output = cmd(curl_cmd)
except OSError:
sys.exit(1)
return_vals = re.findall(r'^HTTP\/\d+\.?\d\s+(\d+)\s+(.*)$',
curl_output, re.MULTILINE)
for val in return_vals:
if int(val[0]) not in [200, 301, 302]:
print('HTTP error: {0} {1}'.format(*val))
sys.exit(1)
if request['user']:
curl_cmd = 'curl -# -u {0} {1}'.format(request['user'], remote_file)
else:
curl_cmd = 'curl {0} -# {1}'.format(redirect_opt, remote_file)
try:
return cmd(curl_cmd, stderr=None)
except OSError:
return None

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