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#!/usr/bin/env python3
# Restricts rsync to subdirectory declared in .ssh/authorized_keys. See
# the rrsync man page for details of how to make use of this script.
# NOTE: install python3 braceexpand to support brace expansion in the args!
# Originally a perl script by: Joe Smith <js-cgi@inwap.com> 30-Sep-2004
# Python version by: Wayne Davison <wayne@opencoder.net>
# You may configure these 2 values to your liking. See also the section of
# short & long options if you want to disable any options that rsync accepts.
RSYNC = '/usr/bin/rsync'
LOGFILE = 'rrsync.log' # NOTE: the file must exist for a line to be appended!
# The following options are mainly the options that a client rsync can send
# to the server, and usually just in the one option format that the stock
# rsync produces. However, there are some additional convenience options
# added as well, and thus a few options are present in both the short and
# long lists (such as --group, --owner, and --perms).
# NOTE when disabling: check for both a short & long version of the option!
### START of options data produced by the cull-options script. ###
# To disable a short-named option, add its letter to this string:
short_disabled = 's'
# These are also disabled when the restricted dir is not "/":
short_disabled_subdir = 'KLk'
# These are all possible short options that we will accept (when not disabled above):
short_no_arg = 'ACDEHIJKLNORSUWXbcdgklmnopqrstuvxyz' # DO NOT REMOVE ANY
short_with_num = '@B' # DO NOT REMOVE ANY
# To disable a long-named option, change its value to a -1. The values mean:
# 0 = the option has no arg; 1 = the arg doesn't need any checking; 2 = only
# check the arg when receiving; and 3 = always check the arg.
long_opts = {
'append': 0,
'backup-dir': 2,
'block-size': 1,
'bwlimit': 1,
'checksum-choice': 1,
'checksum-seed': 1,
'compare-dest': 2,
'compress-choice': 1,
'compress-level': 1,
'copy-dest': 2,
'copy-devices': -1,
'copy-unsafe-links': 0,
'daemon': -1,
'debug': 1,
'delay-updates': 0,
'delete': 0,
'delete-after': 0,
'delete-before': 0,
'delete-delay': 0,
'delete-during': 0,
'delete-excluded': 0,
'delete-missing-args': 0,
'existing': 0,
'fake-super': 0,
'files-from': 3,
'force': 0,
'from0': 0,
'fsync': 0,
'fuzzy': 0,
'group': 0,
'groupmap': 1,
'hard-links': 0,
'iconv': 1,
'ignore-errors': 0,
'ignore-existing': 0,
'ignore-missing-args': 0,
'ignore-times': 0,
'info': 1,
'inplace': 0,
'link-dest': 2,
'links': 0,
'list-only': 0,
'log-file': 3,
'log-format': 1,
'max-alloc': 1,
'max-delete': 1,
'max-size': 1,
'min-size': 1,
'mkpath': 0,
'modify-window': 1,
'msgs2stderr': 0,
'munge-links': 0,
'new-compress': 0,
'no-W': 0,
'no-implied-dirs': 0,
'no-msgs2stderr': 0,
'no-munge-links': -1,
'no-r': 0,
'no-relative': 0,
'no-specials': 0,
'numeric-ids': 0,
'old-compress': 0,
'one-file-system': 0,
'only-write-batch': 1,
'open-noatime': 0,
'owner': 0,
'partial': 0,
'partial-dir': 2,
'perms': 0,
'preallocate': 0,
'recursive': 0,
'remove-sent-files': 0,
'remove-source-files': 0,
'safe-links': 0,
'sender': 0,
'server': 0,
'size-only': 0,
'skip-compress': 1,
'specials': 0,
'stats': 0,
'stderr': 1,
'suffix': 1,
'super': 0,
'temp-dir': 2,
'timeout': 1,
'times': 0,
'use-qsort': 0,
'usermap': 1,
'write-devices': -1,
}
### END of options data produced by the cull-options script. ###
import os, sys, re, argparse, glob, socket, time, subprocess
from argparse import RawTextHelpFormatter
try:
from braceexpand import braceexpand
except:
braceexpand = lambda x: [ DE_BACKSLASH_RE.sub(r'\1', x) ]
HAS_DOT_DOT_RE = re.compile(r'(^|/)\.\.(/|$)')
LONG_OPT_RE = re.compile(r'^--([^=]+)(?:=(.*))?$')
DE_BACKSLASH_RE = re.compile(r'\\(.)')
def main():
if not os.path.isdir(args.dir):
die("Restricted directory does not exist!")
# The format of the environment variables set by sshd:
# SSH_ORIGINAL_COMMAND:
# rsync --server -vlogDtpre.iLsfxCIvu --etc . ARG # push
# rsync --server --sender -vlogDtpre.iLsfxCIvu --etc . ARGS # pull
# SSH_CONNECTION (client_ip client_port server_ip server_port):
# 192.168.1.100 64106 192.168.1.2 22
command = os.environ.get('SSH_ORIGINAL_COMMAND', None)
if not command:
die("Not invoked via sshd")
command = command.split(' ', 2)
if command[0:1] != ['rsync']:
die("SSH_ORIGINAL_COMMAND does not run rsync")
if command[1:2] != ['--server']:
die("--server option is not the first arg")
command = '' if len(command) < 3 else command[2]
global am_sender
am_sender = command.startswith("--sender ") # Restrictive on purpose!
if args.ro and not am_sender:
die("sending to read-only server is not allowed")
if args.wo and am_sender:
die("reading from write-only server is not allowed")
if args.wo or not am_sender:
long_opts['sender'] = -1
if args.no_del:
for opt in long_opts:
if opt.startswith(('remove', 'delete')):
long_opts[opt] = -1
if args.ro:
long_opts['log-file'] = -1
if args.dir != '/':
global short_disabled
short_disabled += short_disabled_subdir
short_no_arg_re = short_no_arg
short_with_num_re = short_with_num
if short_disabled:
for ltr in short_disabled:
short_no_arg_re = short_no_arg_re.replace(ltr, '')
short_with_num_re = short_with_num_re.replace(ltr, '')
short_disabled_re = re.compile(r'^-[%s]*([%s])' % (short_no_arg_re, short_disabled))
short_no_arg_re = re.compile(r'^-(?=.)[%s]*(e\d*\.\w*)?$' % short_no_arg_re)
short_with_num_re = re.compile(r'^-[%s]\d+$' % short_with_num_re)
log_fh = open(LOGFILE, 'a') if os.path.isfile(LOGFILE) else None
try:
os.chdir(args.dir)
except OSError as e:
die('unable to chdir to restricted dir:', str(e))
rsync_opts = [ '--server' ]
rsync_args = [ ]
saw_the_dot_arg = False
last_opt = check_type = None
for arg in re.findall(r'(?:[^\s\\]+|\\.[^\s\\]*)+', command):
if check_type:
rsync_opts.append(validated_arg(last_opt, arg, check_type))
check_type = None
elif saw_the_dot_arg:
# NOTE: an arg that starts with a '-' is safe due to our use of "--" in the cmd tuple.
try:
b_e = braceexpand(arg) # Also removes backslashes
except: # Handle errors such as unbalanced braces by just de-backslashing the arg:
b_e = [ DE_BACKSLASH_RE.sub(r'\1', arg) ]
for xarg in b_e:
rsync_args += validated_arg('arg', xarg, wild=True)
else: # parsing the option args
if arg == '.':
saw_the_dot_arg = True
continue
rsync_opts.append(arg)
if short_no_arg_re.match(arg) or short_with_num_re.match(arg):
continue
disabled = False
m = LONG_OPT_RE.match(arg)
if m:
opt = m.group(1)
opt_arg = m.group(2)
ct = long_opts.get(opt, None)
if ct is None:
break # Generate generic failure due to unfinished arg parsing
if ct == 0:
continue
opt = '--' + opt
if ct > 0:
if opt_arg is not None:
rsync_opts[-1] = opt + '=' + validated_arg(opt, opt_arg, ct)
else:
check_type = ct
last_opt = opt
continue
disabled = True
elif short_disabled:
m = short_disabled_re.match(arg)
if m:
disabled = True
opt = '-' + m.group(1)
if disabled:
die("option", opt, "has been disabled on this server.")
break # Generate a generic failure
if not saw_the_dot_arg:
die("invalid rsync-command syntax or options")
if args.munge:
rsync_opts.append('--munge-links')
if not rsync_args:
rsync_args = [ '.' ]
cmd = (RSYNC, *rsync_opts, '--', '.', *rsync_args)
if log_fh:
now = time.localtime()
host = os.environ.get('SSH_CONNECTION', 'unknown').split()[0] # Drop everything after the IP addr
if host.startswith('::ffff:'):
host = host[7:]
try:
host = socket.gethostbyaddr(socket.inet_aton(host))
except:
pass
log_fh.write("%02d:%02d:%02d %-16s %s\n" % (now.tm_hour, now.tm_min, now.tm_sec, host, str(cmd)))
log_fh.close()
# NOTE: This assumes that the rsync protocol will not be maliciously hijacked.
if args.no_lock:
os.execlp(RSYNC, *cmd)
die("execlp(", RSYNC, *cmd, ') failed')
child = subprocess.run(cmd)
if child.returncode != 0:
sys.exit(child.returncode)
def validated_arg(opt, arg, typ=3, wild=False):
if opt != 'arg': # arg values already have their backslashes removed.
arg = DE_BACKSLASH_RE.sub(r'\1', arg)
orig_arg = arg
if arg.startswith('./'):
arg = arg[1:]
arg = arg.replace('//', '/')
if args.dir != '/':
if HAS_DOT_DOT_RE.search(arg):
die("do not use .. in", opt, "(anchor the path at the root of your restricted dir)")
if arg.startswith('/'):
arg = args.dir + arg
if wild:
got = glob.glob(arg)
if not got:
got = [ arg ]
else:
got = [ arg ]
ret = [ ]
for arg in got:
if args.dir != '/' and arg != '.' and (typ == 3 or (typ == 2 and not am_sender)):
arg_has_trailing_slash = arg.endswith('/')
if arg_has_trailing_slash:
arg = arg[:-1]
else:
arg_has_trailing_slash_dot = arg.endswith('/.')
if arg_has_trailing_slash_dot:
arg = arg[:-2]
real_arg = os.path.realpath(arg)
if arg != real_arg and not real_arg.startswith(args.dir_slash):
die('unsafe arg:', orig_arg, [arg, real_arg])
if arg_has_trailing_slash:
arg += '/'
elif arg_has_trailing_slash_dot:
arg += '/.'
if opt == 'arg' and arg.startswith(args.dir_slash):
arg = arg[args.dir_slash_len:]
if arg == '':
arg = '.'
ret.append(arg)
return ret if wild else ret[0]
def lock_or_die(dirname):
import fcntl
global lock_handle
lock_handle = os.open(dirname, os.O_RDONLY)
try:
fcntl.flock(lock_handle, fcntl.LOCK_EX | fcntl.LOCK_NB)
except:
die('Another instance of rrsync is already accessing this directory.')
def die(*msg):
print(sys.argv[0], 'error:', *msg, file=sys.stderr)
if sys.stdin.isatty():
arg_parser.print_help(sys.stderr)
sys.exit(1)
# This class displays the --help to the user on argparse error IFF they're running it interactively.
class OurArgParser(argparse.ArgumentParser):
def error(self, msg):
die(msg)
if __name__ == '__main__':
our_desc = """Use "man rrsync" to learn how to restrict ssh users to using a restricted rsync command."""
arg_parser = OurArgParser(description=our_desc, add_help=False)
only_group = arg_parser.add_mutually_exclusive_group()
only_group.add_argument('-ro', action='store_true', help="Allow only reading from the DIR. Implies -no-del and -no-lock.")
only_group.add_argument('-wo', action='store_true', help="Allow only writing to the DIR.")
arg_parser.add_argument('-munge', action='store_true', help="Enable rsync's --munge-links on the server side.")
arg_parser.add_argument('-no-del', action='store_true', help="Disable rsync's --delete* and --remove* options.")
arg_parser.add_argument('-no-lock', action='store_true', help="Avoid the single-run (per-user) lock check.")
arg_parser.add_argument('-help', '-h', action='help', help="Output this help message and exit.")
arg_parser.add_argument('dir', metavar='DIR', help="The restricted directory to use.")
args = arg_parser.parse_args()
args.dir = os.path.realpath(args.dir)
args.dir_slash = args.dir + '/'
args.dir_slash_len = len(args.dir_slash)
if args.ro:
args.no_del = True
elif not args.no_lock:
lock_or_die(args.dir)
main()
# vim: sw=4 et
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