#!/usr/bin/python3
#
# Convert ntp configuration to chrony
#
# Copyright (C) 2018-2019  Miroslav Lichvar <mlichvar@redhat.com>
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


import argparse
import ipaddress
import logging
import os
import re
import subprocess
import sys

# python2 compatibility hacks
if sys.version_info[0] < 3:
    from io import open
    reload(sys)
    sys.setdefaultencoding("utf-8")


class NtpConfiguration(object):
    def __init__(self, root_dir, ntp_conf, step_tickers):
        self.root_dir = root_dir if root_dir != "/" else ""
        self.ntp_conf_path = ntp_conf
        self.step_tickers_path = step_tickers

        # Read and write files using an 8-bit transparent encoding
        self.file_encoding = "latin-1"
        self.enabled_services = set()
        self.step_tickers = []
        self.time_sources = []
        self.fudges = {}
        self.restrictions = {
                # Built-in defaults
                ipaddress.ip_network(u"0.0.0.0/0"): set(),
                ipaddress.ip_network(u"::/0"): set(),
        }
        self.keyfile = ""
        self.keys = []
        self.trusted_keys = []
        self.driftfile = ""
        self.statistics = []
        self.leapfile = ""
        self.tos_options = {}
        self.ignored_directives = set()
        self.ignored_lines = []

        # self.detect_enabled_services()
        self.parse_step_tickers()
        self.parse_ntp_conf()

    def detect_enabled_services(self):
        for service in ["ntpdate", "ntpd", "ntp-wait"]:
            service_path = os.path.join(self.root_dir,
                                        "etc/systemd/system/multi-user.target.wants/{}.service".format(service))
            if os.path.islink(service_path):
                self.enabled_services.add(service)
        logging.info("Enabled services found in /etc/systemd/system: %s",
                     " ".join(self.enabled_services))

    def parse_step_tickers(self):
        if not self.step_tickers_path:
            return

        path = os.path.join(self.root_dir, self.step_tickers_path)
        if not os.path.isfile(path):
            logging.info("Missing %s", path)
            return

        with open(path, encoding=self.file_encoding) as f:
            for line in f:
                line = line[:line.find('#')]

                words = line.split()

                if not words:
                    continue

                self.step_tickers.extend(words)

    def parse_ntp_conf(self, path=None):
        if path is None:
            path = os.path.join(self.root_dir, self.ntp_conf_path)

        with open(path, encoding=self.file_encoding) as f:
            logging.info("Reading %s", path)

            for line in f:
                line = line[:line.find('#')]

                words = line.split()

                if not words:
                    continue

                if not self.parse_directive(words):
                    self.ignored_lines.append(line)

    def parse_directive(self, words):
        name = words.pop(0)
        if name.startswith("logconfig"):
            name = "logconfig"

        if words:
            if name in ["server", "peer", "pool"]:
                return self.parse_source(name, words)
            elif name == "fudge":
                return self.parse_fudge(words)
            elif name == "restrict":
                return self.parse_restrict(words)
            elif name == "tos":
                return self.parse_tos(words)
            elif name == "includefile":
                return self.parse_includefile(words)
            elif name == "keys":
                return self.parse_keys(words)
            elif name == "trustedkey":
                return self.parse_trustedkey(words)
            elif name == "driftfile":
                self.driftfile = words[0]
            elif name == "statistics":
                self.statistics = words
            elif name == "leapfile":
                self.leapfile = words[0]
            else:
                self.ignored_directives.add(name)
                return False
        else:
            self.ignored_directives.add(name)
            return False

        return True

    def parse_source(self, source_type, words):
        ipv4_only = False
        ipv6_only = False
        source = {
                "type": source_type,
                "options": []
        }

        if words[0] == "-4":
            ipv4_only = True
            words.pop(0)
        elif words[0] == "-6":
            ipv6_only = True
            words.pop(0)

        if not words:
            return False

        source["address"] = words.pop(0)

        # Check if -4/-6 corresponds to the address and ignore hostnames
        if ipv4_only or ipv6_only:
            try:
                version = ipaddress.ip_address(source["address"]).version
                if (ipv4_only and version != 4) or (ipv6_only and version != 6):
                    return False
            except ValueError:
                return False

        if source["address"].startswith("127.127."):
            if not source["address"].startswith("127.127.1."):
                # Ignore non-LOCAL refclocks
                return False

        while words:
            if len(words) >= 2 and words[0] in ["minpoll", "maxpoll", "version", "key"]:
                source["options"].append((words[0], words[1]))
                words = words[2:]
            elif words[0] in ["burst", "iburst", "noselect", "prefer", "true", "xleave"]:
                source["options"].append((words[0],))
                words.pop(0)
            else:
                return False

        self.time_sources.append(source)
        return True

    def parse_fudge(self, words):
        address = words.pop(0)
        options = {}

        while words:
            if len(words) >= 2 and words[0] in ["stratum"]:
                if not words[1].isdigit():
                    return False
                options[words[0]] = int(words[1])
                words = words[2:]
            elif len(words) >= 2:
                words = words[2:]
            else:
                return False

        self.fudges[address] = options
        return True

    def parse_restrict(self, words):
        ipv4_only = False
        ipv6_only = False
        flags = set()
        mask = ""

        if words[0] == "-4":
            ipv4_only = True
            words.pop(0)
        elif words[0] == "-6":
            ipv6_only = True
            words.pop(0)

        if not words:
            return False

        address = words.pop(0)

        while words:
            if len(words) >= 2 and words[0] == "mask":
                mask = words[1]
                words = words[2:]
            else:
                if words[0] not in ["kod", "nomodify", "notrap", "nopeer", "noquery",
                                    "limited", "ignore", "noserve"]:
                    return False
                flags.add(words[0])
                words.pop(0)

        # Convert to IP network(s), ignoring restrictions with hostnames
        networks = []
        if address == "default" and not mask:
            if not ipv6_only:
                networks.append(ipaddress.ip_network(u"0.0.0.0/0"))
            if not ipv4_only:
                networks.append(ipaddress.ip_network(u"::/0"))
        else:
            try:
                if mask:
                    # Count bits in the mask (ipaddress does not support
                    # expanded IPv6 netmasks)
                    mask_ip = ipaddress.ip_address(mask)
                    mask_str = "{0:0{1}b}".format(int(mask_ip), mask_ip.max_prefixlen)
                    networks.append(ipaddress.ip_network(
                                    u"{}/{}".format(address, len(mask_str.rstrip('0')))))
                else:
                    networks.append(ipaddress.ip_network(address))
            except ValueError:
                return False

            if (ipv4_only and networks[-1].version != 4) or \
                    (ipv6_only and networks[-1].version != 6):
                return False

        for network in networks:
            self.restrictions[network] = flags

        return True

    def parse_tos(self, words):
        options = {}
        while words:
            if len(words) >= 2 and words[0] in ["minsane", "orphan"]:
                if not words[1].isdigit():
                    return False
                options[words[0]] = int(words[1])
                words = words[2:]
            elif len(words) >= 2 and words[0] in ["maxdist"]:
                # Check if it is a float value
                if not words[1].replace('.', '', 1).isdigit():
                    return False
                options[words[0]] = float(words[1])
                words = words[2:]
            else:
                return False

        self.tos_options.update(options)

        return True

    def parse_includefile(self, words):
        path = os.path.join(self.root_dir, words[0])
        if not os.path.isfile(path):
            return False

        self.parse_ntp_conf(path)
        return True

    def parse_keys(self, words):
        keyfile = words[0]
        path = os.path.join(self.root_dir, keyfile)
        if not os.path.isfile(path):
            logging.info("Missing %s", path)
            return False

        with open(path, encoding=self.file_encoding) as f:
            logging.info("Reading %s", path)
            keys = []
            for line in f:
                words = line.split()
                if len(words) < 3 or not words[0].isdigit():
                    continue
                keys.append((int(words[0]), words[1], words[2]))

            self.keyfile = keyfile
            self.keys = keys

        return True

    def parse_trustedkey(self, words):
        key_ranges = []
        for word in words:
            if word.isdigit():
                key_ranges.append((int(word), int(word)))
            elif re.match("^[0-9]+-[0-9]+$", word):
                first, last = word.split("-")
                key_ranges.append((int(first), int(last)))
            else:
                return False

        self.trusted_keys = key_ranges
        return True

    def write_chrony_configuration(self, chrony_conf_path, chrony_keys_path,
                                   dry_run=False, backup=False):
        chrony_conf = self.get_chrony_conf(chrony_keys_path)
        logging.debug("Generated %s:\n%s", chrony_conf_path, chrony_conf)

        if not dry_run:
            self.write_file(chrony_conf_path, 0o644, chrony_conf, backup)

        chrony_keys = self.get_chrony_keys()
        if chrony_keys:
            logging.debug("Generated %s:\n%s", chrony_keys_path, chrony_keys)

        if not dry_run:
            self.write_file(chrony_keys_path, 0o640, chrony_keys, backup)

    def get_processed_time_sources(self):
        # Convert {0,1,2,3}.*pool.ntp.org servers to 2.*pool.ntp.org pools

        # Make shallow copies of all sources (only type will be modified)
        time_sources = [s.copy() for s in self.time_sources]

        pools = {}
        for source in time_sources:
            if source["type"] != "server":
                continue
            m = re.match("^([0123])(\\.\\w+)?\\.pool\\.ntp\\.org$", source["address"])
            if m is None:
                continue
            number = m.group(1)
            zone = m.group(2)
            if zone not in pools:
                pools[zone] = []
            pools[zone].append((int(number), source))

        remove_servers = set()
        for zone, pool in pools.items():
            # sort and skip all pools not in [0, 3] range
            pool.sort()
            if [number for number, source in pool] != [0, 1, 2, 3]:
                # only exact group of 4 servers can be converted, nothing to do here
                continue
            # verify that parameters are the same for all servers in the pool
            if not all([p[1]["options"] == pool[0][1]["options"] for p in pool]):
                break
            remove_servers.update([pool[i][1]["address"] for i in [0, 1, 3]])
            pool[2][1]["type"] = "pool"

        processed_sources = []
        for source in time_sources:
            if source["type"] == "server" and source["address"] in remove_servers:
                continue
            processed_sources.append(source)
        return processed_sources

    def get_chrony_conf_sources(self):
        conf = ""

        if self.step_tickers:
            conf += "# Specify NTP servers used for initial correction.\n"
            conf += "initstepslew 0.1 {}\n".format(" ".join(self.step_tickers))
            conf += "\n"

        conf += "# Specify time sources.\n"

        for source in self.get_processed_time_sources():
            address = source["address"]
            if address.startswith("127.127."):
                if address.startswith("127.127.1."):
                    continue
                # No other refclocks are expected from the parser
                assert False
            else:
                conf += "{} {}".format(source["type"], address)
                for option in source["options"]:
                    if option[0] in ["minpoll", "maxpoll", "version", "key",
                                     "iburst", "noselect", "prefer", "xleave"]:
                        conf += " {}".format(" ".join(option))
                    elif option[0] == "burst":
                        conf += " presend 6"
                    elif option[0] == "true":
                        conf += " trust"
                    else:
                        # No other options are expected from the parser
                        assert False
                conf += "\n"
        conf += "\n"

        return conf

    def get_chrony_conf_allows(self):
        allowed_networks = filter(lambda n: "ignore" not in self.restrictions[n] and
                                    "noserve" not in self.restrictions[n],
                                  self.restrictions.keys())

        conf = ""
        for network in sorted(allowed_networks, key=lambda n: (n.version, n)):
            if network.num_addresses > 1:
                conf += "allow {}\n".format(network)
            else:
                conf += "allow {}\n".format(network.network_address)

        if conf:
            conf = "# Allow NTP client access.\n" + conf
            conf += "\n"

        return conf

    def get_chrony_conf_cmdallows(self):
        allowed_networks = filter(lambda n: "ignore" not in self.restrictions[n] and
                                    "noquery" not in self.restrictions[n] and
                                    n != ipaddress.ip_network(u"127.0.0.1/32") and
                                    n != ipaddress.ip_network(u"::1/128"),
                                  self.restrictions.keys())

        ip_versions = set()
        conf = ""
        for network in sorted(allowed_networks, key=lambda n: (n.version, n)):
            ip_versions.add(network.version)
            if network.num_addresses > 1:
                conf += "cmdallow {}\n".format(network)
            else:
                conf += "cmdallow {}\n".format(network.network_address)

        if conf:
            conf = "# Allow remote monitoring.\n" + conf
            if 4 in ip_versions:
                conf += "bindcmdaddress 0.0.0.0\n"
            if 6 in ip_versions:
                conf += "bindcmdaddress ::\n"
            conf += "\n"

        return conf

    def get_chrony_conf(self, chrony_keys_path):
        local_stratum = 0
        maxdistance = 0.0
        minsources = 1
        orphan_stratum = 0
        logs = []

        for source in self.time_sources:
            address = source["address"]
            if address.startswith("127.127.1."):
                if address in self.fudges and "stratum" in self.fudges[address]:
                    local_stratum = self.fudges[address]["stratum"]
                else:
                    local_stratum = 5

        if "maxdist" in self.tos_options:
            maxdistance = self.tos_options["maxdist"]
        if "minsane" in self.tos_options:
            minsources = self.tos_options["minsane"]
        if "orphan" in self.tos_options:
            orphan_stratum = self.tos_options["orphan"]

        if "clockstats" in self.statistics:
            logs.append("refclocks")
        if "loopstats" in self.statistics:
            logs.append("tracking")
        if "peerstats" in self.statistics:
            logs.append("statistics")
        if "rawstats" in self.statistics:
            logs.append("measurements")

        conf = "# This file was converted from {}{}.\n".format(
                    self.ntp_conf_path,
                    " and " + self.step_tickers_path if self.step_tickers_path else "")
        conf += "\n"

        if self.ignored_lines:
            conf += "# The following directives were ignored in the conversion:\n"

            for line in self.ignored_lines:
                # Remove sensitive information
                line = re.sub(r"\s+pw\s+\S+", " pw XXX", line.rstrip())
                conf += "# " + line + "\n"
            conf += "\n"

        conf += self.get_chrony_conf_sources()

        conf += "# Record the rate at which the system clock gains/losses time.\n"
        if not self.driftfile:
            conf += "#"
        conf += "driftfile /var/lib/chrony/drift\n"
        conf += "\n"

        conf += "# Allow the system clock to be stepped in the first three updates\n"
        conf += "# if its offset is larger than 1 second.\n"
        conf += "makestep 1.0 3\n"
        conf += "\n"

        conf += "# Enable kernel synchronization of the real-time clock (RTC).\n"
        conf += "rtcsync\n"
        conf += "\n"

        conf += "# Enable hardware timestamping on all interfaces that support it.\n"
        conf += "#hwtimestamp *\n"
        conf += "\n"

        if maxdistance > 0.0:
            conf += "# Specify the maximum distance of sources to be selectable.\n"
            conf += "maxdistance {}\n".format(maxdistance)
            conf += "\n"

        conf += "# Increase the minimum number of selectable sources required to adjust\n"
        conf += "# the system clock.\n"
        if minsources > 1:
            conf += "minsources {}\n".format(minsources)
        else:
            conf += "#minsources 2\n"
        conf += "\n"

        conf += self.get_chrony_conf_allows()

        conf += self.get_chrony_conf_cmdallows()

        conf += "# Serve time even if not synchronized to a time source.\n"
        if orphan_stratum > 0 and orphan_stratum < 16:
            conf += "local stratum {} orphan\n".format(orphan_stratum)
        elif local_stratum > 0 and local_stratum < 16:
            conf += "local stratum {}\n".format(local_stratum)
        else:
            conf += "#local stratum 10\n"
        conf += "\n"

        conf += "# Specify file containing keys for NTP authentication.\n"
        conf += "keyfile {}\n".format(chrony_keys_path)
        conf += "\n"

        conf += "# Get TAI-UTC offset and leap seconds from the system tz database.\n"
        conf += "leapsectz right/UTC\n"
        conf += "\n"

        conf += "# Specify directory for log files.\n"
        conf += "logdir /var/log/chrony\n"
        conf += "\n"

        conf += "# Select which information is logged.\n"
        if logs:
            conf += "log {}\n".format(" ".join(logs))
        else:
            conf += "#log measurements statistics tracking\n"

        return conf

    def get_chrony_keys(self):
        if not self.keyfile:
            return ""

        keys = "# This file was converted from {}.\n".format(self.keyfile)
        keys += "\n"

        for key in self.keys:
            key_id = key[0]
            key_type = key[1]
            password = key[2]

            if key_type in ["m", "M"]:
                key_type = "MD5"
            elif key_type == "AES128CMAC":
                key_type = "AES128"
            elif key_type not in ["MD5", "SHA1", "SHA256", "SHA384", "SHA512"]:
                continue

            prefix = "ASCII" if len(password) <= 20 else "HEX"

            for first, last in self.trusted_keys:
                if first <= key_id <= last:
                    trusted = True
                    break
            else:
                trusted = False

            # Disable keys that were not marked as trusted
            if not trusted:
                keys += "#"

            keys += "{} {} {}:{}\n".format(key_id, key_type, prefix, password)

        return keys

    def write_file(self, path, mode, content, backup):
        path = self.root_dir + path
        if backup and os.path.isfile(path):
            os.rename(path, path + ".old")

        with open(os.open(path, os.O_CREAT | os.O_WRONLY | os.O_EXCL, mode), "w",
                  encoding=self.file_encoding) as f:
            logging.info("Writing %s", path)
            f.write(u"" + content)

        # Fix SELinux context if restorecon is installed
        try:
            subprocess.call(["restorecon", path])
        except OSError:
            pass


def main():
    parser = argparse.ArgumentParser(description="Convert ntp configuration to chrony.")
    parser.add_argument("-r", "--root", dest="roots", default=["/"], nargs="+",
                        metavar="DIR", help="specify root directory (default /)")
    parser.add_argument("--ntp-conf", action="store", default="/etc/ntp.conf",
                        metavar="FILE", help="specify ntp config (default /etc/ntp.conf)")
    parser.add_argument("--step-tickers", action="store", default="",
                        metavar="FILE", help="specify ntpdate step-tickers config (no default)")
    parser.add_argument("--chrony-conf", action="store", default="/etc/chrony.conf",
                        metavar="FILE", help="specify chrony config (default /etc/chrony.conf)")
    parser.add_argument("--chrony-keys", action="store", default="/etc/chrony.keys",
                        metavar="FILE", help="specify chrony keyfile (default /etc/chrony.keys)")
    parser.add_argument("-b", "--backup", action="store_true", help="backup existing configs before writing")
    parser.add_argument("-L", "--ignored-lines", action="store_true", help="print ignored lines")
    parser.add_argument("-D", "--ignored-directives", action="store_true",
                        help="print names of ignored directives")
    parser.add_argument("-n", "--dry-run", action="store_true", help="don't make any changes")
    parser.add_argument("-v", "--verbose", action="count", default=0, help="increase verbosity")

    args = parser.parse_args()

    logging.basicConfig(format="%(message)s",
                        level=[logging.ERROR, logging.INFO, logging.DEBUG][min(args.verbose, 2)])

    for root in args.roots:
        conf = NtpConfiguration(root, args.ntp_conf, args.step_tickers)

        if args.ignored_lines:
            for line in conf.ignored_lines:
                print(line)

        if args.ignored_directives:
            for directive in conf.ignored_directives:
                print(directive)

        conf.write_chrony_configuration(args.chrony_conf, args.chrony_keys, args.dry_run, args.backup)


if __name__ == "__main__":
    main()