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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