#! @PYTHON3@
# Copyright (c) 2017 Nicira, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at:
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import argparse
import re
import subprocess
import sys
import copy
import os
from string import Template

import ovs.daemon
import ovs.db.idl
import ovs.dirs
import ovs.unixctl
import ovs.unixctl.server
import ovs.util
import ovs.vlog


FILE_HEADER = "# Generated by ovs-monitor-ipsec...do not modify by hand!\n\n"
transp_tmpl = {"gre": Template("""\
conn $ifname-$version
$auth_section
    leftprotoport=gre
    rightprotoport=gre

"""), "gre64": Template("""\
conn $ifname-$version
$auth_section
    leftprotoport=gre
    rightprotoport=gre

"""), "geneve": Template("""\
conn $ifname-in-$version
$auth_section
    leftprotoport=udp/6081
    rightprotoport=udp

conn $ifname-out-$version
$auth_section
    leftprotoport=udp
    rightprotoport=udp/6081

"""), "stt": Template("""\
conn $ifname-in-$version
$auth_section
    leftprotoport=tcp/7471
    rightprotoport=tcp

conn $ifname-out-$version
$auth_section
    leftprotoport=tcp
    rightprotoport=tcp/7471

"""), "vxlan": Template("""\
conn $ifname-in-$version
$auth_section
    leftprotoport=udp/4789
    rightprotoport=udp

conn $ifname-out-$version
$auth_section
    leftprotoport=udp
    rightprotoport=udp/4789

""")}
vlog = ovs.vlog.Vlog("ovs-monitor-ipsec")
exiting = False
monitor = None
xfrm = None


class XFRM(object):
    """This class is a simple wrapper around ip-xfrm (8) command line
    utility.  We are using this class only for informational purposes
    so that ovs-monitor-ipsec could verify that IKE keying daemon has
    installed IPsec policies and security associations into kernel as
    expected."""

    def __init__(self, ip_root_prefix):
        self.IP = ip_root_prefix + "/sbin/ip"

    def get_policies(self):
        """This function returns IPsec policies (from kernel) in a dictionary
        where <key> is destination IPv4 address and <value> is SELECTOR of
        the IPsec policy."""
        policies = {}
        proc = subprocess.Popen([self.IP, 'xfrm', 'policy'],
                                stdout=subprocess.PIPE)
        while True:
            line = proc.stdout.readline().strip()
            if line == '':
                break
            a = line.split(" ")
            if len(a) >= 4 and a[0] == "src" and a[2] == "dst":
                dst = (a[3].split("/"))[0]
                if dst not in policies:
                    policies[dst] = []
                policies[dst].append(line)
                src = (a[3].split("/"))[0]
                if src not in policies:
                    policies[src] = []
                policies[src].append(line)
        return policies

    def get_securities(self):
        """This function returns IPsec security associations (from kernel)
        in a dictionary where <key> is destination IPv4 address and <value>
        is SELECTOR."""
        securities = {}
        proc = subprocess.Popen([self.IP, 'xfrm', 'state'],
                                stdout=subprocess.PIPE)
        while True:
            line = proc.stdout.readline().strip()
            if line == '':
                break
            a = line.split(" ")
            if len(a) >= 4 and a[0] == "sel" \
                    and a[1] == "src" and a[3] == "dst":
                remote_ip = a[4].rstrip().split("/")[0]
                local_ip = a[2].rstrip().split("/")[0]
                if remote_ip not in securities:
                    securities[remote_ip] = []
                securities[remote_ip].append(line)
                if local_ip not in securities:
                    securities[local_ip] = []
                securities[local_ip].append(line)
        return securities


class StrongSwanHelper(object):
    """This class does StrongSwan specific configurations."""

    STRONGSWAN_CONF = """%s
charon.plugins.kernel-netlink.set_proto_port_transport_sa = yes
charon.plugins.kernel-netlink.xfrm_ack_expires = 10
charon.load_modular = yes
charon.plugins.gcm.load = yes
""" % (FILE_HEADER)

    CONF_HEADER = """%s
config setup
    uniqueids=yes

conn %%default
    keyingtries=%%forever
    type=transport
    keyexchange=ikev2
    auto=route
    ike=aes256gcm16-sha256-modp2048
    esp=aes256gcm16-modp2048

""" % (FILE_HEADER)

    CA_SECTION = """ca ca_auth
    cacert=%s

"""

    SHUNT_POLICY = """conn prevent_unencrypted_gre
    type=drop
    leftprotoport=gre
    mark={0}

conn prevent_unencrypted_geneve
    type=drop
    leftprotoport=udp/6081
    mark={0}

conn prevent_unencrypted_stt
    type=drop
    leftprotoport=tcp/7471
    mark={0}

conn prevent_unencrypted_vxlan
    type=drop
    leftprotoport=udp/4789
    mark={0}

"""

    auth_tmpl = {"psk": Template("""\
    left=0.0.0.0
    right=$remote_ip
    authby=psk"""),
                 "pki_remote": Template("""\
    left=0.0.0.0
    right=$remote_ip
    leftid=$local_name
    rightid=$remote_name
    leftcert=$certificate
    rightcert=$remote_cert"""),
                 "pki_ca": Template("""\
    left=0.0.0.0
    right=$remote_ip
    leftid=$local_name
    rightid=$remote_name
    leftcert=$certificate""")}

    def __init__(self, root_prefix):
        self.CHARON_CONF = root_prefix + "/etc/strongswan.d/ovs.conf"
        self.IPSEC = root_prefix + "/usr/sbin/ipsec"
        self.IPSEC_CONF = root_prefix + "/etc/ipsec.conf"
        self.IPSEC_SECRETS = root_prefix + "/etc/ipsec.secrets"
        self.conf_file = None
        self.secrets_file = None

    def restart_ike_daemon(self):
        """This function restarts StrongSwan."""
        f = open(self.CHARON_CONF, "w")
        f.write(self.STRONGSWAN_CONF)
        f.close()

        f = open(self.IPSEC_CONF, "w")
        f.write(self.CONF_HEADER)
        f.close()

        f = open(self.IPSEC_SECRETS, "w")
        f.write(FILE_HEADER)
        f.close()

        vlog.info("Restarting StrongSwan")
        subprocess.call([self.IPSEC, "restart"])

    def get_active_conns(self):
        """This function parses output from 'ipsec status' command.
        It returns dictionary where <key> is interface name (as in OVSDB)
        and <value> is another dictionary.  This another dictionary
        uses strongSwan connection name as <key> and more detailed
        sample line from the parsed outpus as <value>. """

        conns = {}
        proc = subprocess.Popen([self.IPSEC, 'status'], stdout=subprocess.PIPE)

        while True:
            line = proc.stdout.readline().strip()
            if line == '':
                break
            tunnel_name = line.split(":")
            if len(tunnel_name) < 2:
                continue
            m = re.match(r"(.*)(-in-\d+|-out-\d+|-\d+).*", tunnel_name[0])
            if not m:
                continue
            ifname = m.group(1)
            if ifname not in conns:
                conns[ifname] = {}
            (conns[ifname])[tunnel_name[0]] = line

        return conns

    def config_init(self):
        self.conf_file = open(self.IPSEC_CONF, "w")
        self.secrets_file = open(self.IPSEC_SECRETS, "w")
        self.conf_file.write(self.CONF_HEADER)
        self.secrets_file.write(FILE_HEADER)

    def config_global(self, monitor):
        """Configure the global state of IPsec tunnels."""
        needs_refresh = False

        if monitor.conf_in_use != monitor.conf:
            monitor.conf_in_use = copy.deepcopy(monitor.conf)
            needs_refresh = True

        # Configure the shunt policy
        if monitor.conf_in_use["skb_mark"]:
            skb_mark = monitor.conf_in_use["skb_mark"]
            self.conf_file.write(self.SHUNT_POLICY.format(skb_mark))

        # Configure the CA cert
        if monitor.conf_in_use["pki"]["ca_cert"]:
            cacert = monitor.conf_in_use["pki"]["ca_cert"]
            self.conf_file.write(self.CA_SECTION % cacert)

        return needs_refresh

    def config_tunnel(self, tunnel):
        if tunnel.conf["psk"]:
            self.secrets_file.write('0.0.0.0 %s : PSK "%s"\n' %
                            (tunnel.conf["remote_ip"], tunnel.conf["psk"]))
            auth_section = self.auth_tmpl["psk"].substitute(tunnel.conf)
        else:
            self.secrets_file.write("0.0.0.0 %s : RSA %s\n" %
                                        (tunnel.conf["remote_ip"],
                                        tunnel.conf["private_key"]))
            if tunnel.conf["remote_cert"]:
                tmpl = self.auth_tmpl["pki_remote"]
                auth_section = tmpl.substitute(tunnel.conf)
            else:
                tmpl = self.auth_tmpl["pki_ca"]
                auth_section = tmpl.substitute(tunnel.conf)

        vals = tunnel.conf.copy()
        vals["auth_section"] = auth_section
        vals["version"] = tunnel.version
        conf_text = transp_tmpl[tunnel.conf["tunnel_type"]].substitute(vals)
        self.conf_file.write(conf_text)

    def config_fini(self):
        self.secrets_file.close()
        self.conf_file.close()
        self.secrets_file = None
        self.conf_file = None

    def refresh(self, monitor):
        """This functions refreshes strongSwan configuration.  Behind the
        scenes this function calls:
        1. once "ipsec update" command that tells strongSwan to load
           all new tunnels from "ipsec.conf"; and
        2. once "ipsec rereadsecrets" command that tells strongswan to load
           secrets from "ipsec.conf" file
        3. for every removed tunnel "ipsec stroke down-nb <tunnel>" command
           that removes old tunnels.
        Once strongSwan vici bindings will be distributed with major
        Linux distributions this function could be simplified."""
        vlog.info("Refreshing StrongSwan configuration")
        subprocess.call([self.IPSEC, "update"])
        subprocess.call([self.IPSEC, "rereadsecrets"])
        # "ipsec update" command does not remove those tunnels that were
        # updated or that disappeared from the ipsec.conf file.  So, we have
        # to manually remove them by calling "ipsec stroke down-nb <tunnel>"
        # command.  We use <version> number to tell apart tunnels that
        # were just updated.
        # "ipsec down-nb" command is designed to be non-blocking (opposed
        # to "ipsec down" command).  This means that we should not be concerned
        # about possibility of ovs-monitor-ipsec to block for each tunnel
        # while strongSwan sends IKE messages over Internet.
        conns_dict = self.get_active_conns()
        for ifname, conns in conns_dict.iteritems():
            tunnel = monitor.tunnels.get(ifname)
            for conn in conns:
                # IPsec "connection" names that we choose in strongswan
                # must start with Interface name
                if not conn.startswith(ifname):
                    vlog.err("%s does not start with %s" % (conn, ifname))
                    continue

                # version number should be the first integer after
                # interface name in IPsec "connection"
                try:
                    ver = int(re.findall(r'\d+', conn[len(ifname):])[0])
                except IndexError:
                    vlog.err("%s does not contain version number")
                    continue
                except ValueError:
                    vlog.err("%s does not contain version number")
                    continue

                if not tunnel or tunnel.version != ver:
                    vlog.info("%s is outdated %u" % (conn, ver))
                    subprocess.call([self.IPSEC, "stroke", "down-nb", conn])


class LibreSwanHelper(object):
    """This class does LibreSwan specific configurations."""
    CONF_HEADER = """%s
config setup
    uniqueids=yes

conn %%default
    keyingtries=%%forever
    type=transport
    auto=route
    ike=aes_gcm256-sha2_256
    esp=aes_gcm256
    ikev2=insist

""" % (FILE_HEADER)

    SHUNT_POLICY = """conn prevent_unencrypted_gre
    type=drop
    left=%defaultroute
    leftprotoport=gre
    mark={0}

conn prevent_unencrypted_geneve
    type=drop
    left=%defaultroute
    leftprotoport=udp/6081
    mark={0}

conn prevent_unencrypted_stt
    type=drop
    left=%defaultroute
    leftprotoport=tcp/7471
    mark={0}

conn prevent_unencrypted_vxlan
    type=drop
    left=%defaultroute
    leftprotoport=udp/4789
    mark={0}

"""

    auth_tmpl = {"psk": Template("""\
    left=%defaultroute
    right=$remote_ip
    authby=secret"""),
                 "pki_remote": Template("""\
    left=%defaultroute
    right=$remote_ip
    leftid=@$local_name
    rightid=@$remote_name
    leftcert="$local_name"
    rightcert="$remote_name"
    leftrsasigkey=%cert"""),
                 "pki_ca": Template("""\
    left=%defaultroute
    right=$remote_ip
    leftid=@$local_name
    rightid=@$remote_name
    leftcert="ovs_certkey_$local_name"
    leftrsasigkey=%cert
    rightca=%same""")}

    CERT_PREFIX = "ovs_cert_"
    CERTKEY_PREFIX = "ovs_certkey_"

    def __init__(self, libreswan_root_prefix):
        self.IPSEC = libreswan_root_prefix + "/usr/sbin/ipsec"
        self.IPSEC_CONF = libreswan_root_prefix + "/etc/ipsec.conf"
        self.IPSEC_SECRETS = libreswan_root_prefix + "/etc/ipsec.secrets"
        self.conf_file = None
        self.secrets_file = None

    def restart_ike_daemon(self):
        """This function restarts LibreSwan."""
        # Remove the stale information from the NSS database
        self._nss_clear_database()

        f = open(self.IPSEC_CONF, "w")
        f.write(self.CONF_HEADER)
        f.close()

        f = open(self.IPSEC_SECRETS, "w")
        f.write(FILE_HEADER)
        f.close()

        vlog.info("Restarting LibreSwan")
        subprocess.call([self.IPSEC, "restart"])

    def config_init(self):
        self.conf_file = open(self.IPSEC_CONF, "w")
        self.secrets_file = open(self.IPSEC_SECRETS, "w")
        self.conf_file.write(self.CONF_HEADER)
        self.secrets_file.write(FILE_HEADER)

    def config_global(self, monitor):
        """Configure the global state of IPsec tunnels."""
        needs_refresh = False

        if monitor.conf_in_use["pki"] != monitor.conf["pki"]:
            # Clear old state
            if monitor.conf_in_use["pki"]["certificate"]:
                local_name = monitor.conf_in_use["pki"]["local_name"]
                self._nss_delete_cert_and_key(self.CERTKEY_PREFIX + local_name)

            if monitor.conf_in_use["pki"]["ca_cert"]:
                self._nss_delete_cert(self.CERT_PREFIX + "cacert")

            # Load new state
            if monitor.conf["pki"]["certificate"]:
                cert = monitor.conf["pki"]["certificate"]
                key = monitor.conf["pki"]["private_key"]
                name = monitor.conf["pki"]["local_name"]
                name = self.CERTKEY_PREFIX + name
                self._nss_import_cert_and_key(cert, key, name)

            if monitor.conf["pki"]["ca_cert"]:
                self._nss_import_cert(monitor.conf["pki"]["ca_cert"],
                                      self.CERT_PREFIX + "cacert", 'CT,,')

            monitor.conf_in_use["pki"] = copy.deepcopy(monitor.conf["pki"])
            needs_refresh = True

        # Configure the shunt policy
        if monitor.conf["skb_mark"]:
            skb_mark = monitor.conf["skb_mark"]
            self.conf_file.write(self.SHUNT_POLICY.format(skb_mark))

        # Will update conf_in_use later in the 'refresh' method
        if monitor.conf_in_use["skb_mark"] != monitor.conf["skb_mark"]:
            needs_refresh = True

        return needs_refresh

    def config_tunnel(self, tunnel):
        if tunnel.conf["psk"]:
            self.secrets_file.write('%%any %s : PSK "%s"\n' %
                            (tunnel.conf["remote_ip"], tunnel.conf["psk"]))
            auth_section = self.auth_tmpl["psk"].substitute(tunnel.conf)
        elif tunnel.conf["remote_cert"]:
            auth_section = self.auth_tmpl["pki_remote"].substitute(tunnel.conf)
            self._nss_import_cert(tunnel.conf["remote_cert"],
                                 self.CERT_PREFIX + tunnel.conf["remote_name"],
                                 'P,P,P')
        else:
            auth_section = self.auth_tmpl["pki_ca"].substitute(tunnel.conf)

        vals = tunnel.conf.copy()
        vals["auth_section"] = auth_section
        vals["version"] = tunnel.version
        conf_text = transp_tmpl[tunnel.conf["tunnel_type"]].substitute(vals)
        self.conf_file.write(conf_text)

    def config_fini(self):
        self.secrets_file.close()
        self.conf_file.close()
        self.secrets_file = None
        self.conf_file = None

    def clear_tunnel_state(self, tunnel):
        if tunnel.conf["remote_cert"]:
            name = self.CERT_PREFIX + tunnel.conf["remote_name"]
            self._nss_delete_cert(name)

    def refresh(self, monitor):
        vlog.info("Refreshing LibreSwan configuration")
        subprocess.call([self.IPSEC, "auto", "--rereadsecrets"])
        tunnels = set(monitor.tunnels.keys())

        # Delete old connections
        conns_dict = self.get_active_conns()
        for ifname, conns in conns_dict.iteritems():
            tunnel = monitor.tunnels.get(ifname)

            for conn in conns:
                # IPsec "connection" names must start with Interface name
                if not conn.startswith(ifname):
                    vlog.err("%s does not start with %s" % (conn, ifname))
                    continue

                # version number should be the first integer after
                # interface name in IPsec "connection"
                try:
                    ver = int(re.findall(r'\d+', conn[len(ifname):])[0])
                except ValueError:
                    vlog.err("%s does not contain version number")
                    continue
                except IndexError:
                    vlog.err("%s does not contain version number")
                    continue

                if not tunnel or tunnel.version != ver:
                    vlog.info("%s is outdated %u" % (conn, ver))
                    subprocess.call([self.IPSEC, "auto", "--delete", conn])
                elif ifname in tunnels:
                    tunnels.remove(ifname)

        # Activate new connections
        for name in tunnels:
            ver = monitor.tunnels[name].version

            if monitor.tunnels[name].conf["tunnel_type"] == "gre":
                conn = "%s-%s" % (name, ver)
                self._start_ipsec_connection(conn)
            else:
                conn_in = "%s-in-%s" % (name, ver)
                conn_out = "%s-out-%s" % (name, ver)
                self._start_ipsec_connection(conn_in)
                self._start_ipsec_connection(conn_out)

        # Update shunt policy if changed
        if monitor.conf_in_use["skb_mark"] != monitor.conf["skb_mark"]:
            if monitor.conf["skb_mark"]:
                subprocess.call([self.IPSEC, "auto", "--add",
                            "--asynchronous", "prevent_unencrypted_gre"])
                subprocess.call([self.IPSEC, "auto", "--add",
                            "--asynchronous", "prevent_unencrypted_geneve"])
                subprocess.call([self.IPSEC, "auto", "--add",
                            "--asynchronous", "prevent_unencrypted_stt"])
                subprocess.call([self.IPSEC, "auto", "--add",
                            "--asynchronous", "prevent_unencrypted_vxlan"])
            else:
                subprocess.call([self.IPSEC, "auto", "--delete",
                            "--asynchronous", "prevent_unencrypted_gre"])
                subprocess.call([self.IPSEC, "auto", "--delete",
                            "--asynchronous", "prevent_unencrypted_geneve"])
                subprocess.call([self.IPSEC, "auto", "--delete",
                            "--asynchronous", "prevent_unencrypted_stt"])
                subprocess.call([self.IPSEC, "auto", "--delete",
                            "--asynchronous", "prevent_unencrypted_vxlan"])
            monitor.conf_in_use["skb_mark"] = monitor.conf["skb_mark"]

    def get_active_conns(self):
        """This function parses output from 'ipsec status' command.
        It returns dictionary where <key> is interface name (as in OVSDB)
        and <value> is another dictionary.  This another dictionary
        uses LibreSwan connection name as <key> and more detailed
        sample line from the parsed outpus as <value>. """

        conns = {}
        proc = subprocess.Popen([self.IPSEC, 'status'], stdout=subprocess.PIPE)

        while True:
            line = proc.stdout.readline().strip()
            if line == '':
                break

            m = re.search(r"#\d+: \"(.*)\".*", line)
            if not m:
                continue

            conn = m.group(1)
            m = re.match(r"(.*)(-in-\d+|-out-\d+|-\d+)", conn)
            if not m:
                continue

            ifname = m.group(1)
            if ifname not in conns:
                conns[ifname] = {}
            (conns[ifname])[conn] = line

        return conns

    def _start_ipsec_connection(self, conn):
        # In a corner case, LibreSwan daemon restarts for some reason and
        # the "ipsec auto --start" command is lost. Just retry to make sure
        # the command is received by LibreSwan.
        while True:
            proc = subprocess.Popen([self.IPSEC, "auto", "--start",
                                    "--asynchronous", conn],
                                    stdout=subprocess.PIPE,
                                    stderr=subprocess.PIPE)
            perr = str(proc.stderr.read())
            pout = str(proc.stdout.read())
            if not re.match(r".*Connection refused.*", perr) and \
                    not re.match(r".*need --listen.*", pout):
                break

    def _nss_clear_database(self):
        """Remove all OVS IPsec related state from the NSS database"""
        try:
            proc = subprocess.Popen(['certutil', '-L', '-d',
                                    'sql:/etc/ipsec.d/'],
                                    stdout=subprocess.PIPE,
                                    stderr=subprocess.PIPE)
            lines = proc.stdout.readlines()

            for line in lines:
                s = line.strip().split()
                if len(s) < 1:
                    continue
                name = s[0]
                if name.startswith(self.CERT_PREFIX):
                    self._nss_delete_cert(name)
                elif name.startswith(self.CERTKEY_PREFIX):
                    self._nss_delete_cert_and_key(name)

        except Exception as e:
            vlog.err("Failed to clear NSS database.\n" + str(e))

    def _nss_import_cert(self, cert, name, cert_type):
        """Cert_type is 'CT,,' for the CA certificate and 'P,P,P' for the
        normal certificate."""
        try:
            proc = subprocess.Popen(['certutil', '-A', '-a', '-i', cert,
                                    '-d', 'sql:/etc/ipsec.d/', '-n',
                                    name, '-t', cert_type],
                                    stdout=subprocess.PIPE,
                                    stderr=subprocess.PIPE)
            proc.wait()
            if proc.returncode:
                raise Exception(proc.stderr.read())
        except Exception as e:
            vlog.err("Failed to import ceretificate into NSS.\n" + str(e))

    def _nss_delete_cert(self, name):
        try:
            proc = subprocess.Popen(['certutil', '-D', '-d',
                                    'sql:/etc/ipsec.d/', '-n', name],
                                    stdout=subprocess.PIPE,
                                    stderr=subprocess.PIPE)
            proc.wait()
            if proc.returncode:
                raise Exception(proc.stderr.read())
        except Exception as e:
            vlog.err("Failed to delete ceretificate from NSS.\n" + str(e))

    def _nss_import_cert_and_key(self, cert, key, name):
        try:
            # Avoid deleting other files
            path = os.path.abspath('/tmp/%s.p12' % name)
            if not path.startswith('/tmp/'):
                raise Exception("Illegal certificate name!")

            # Create p12 file from pem files
            proc = subprocess.Popen(['openssl', 'pkcs12', '-export',
                                    '-in', cert, '-inkey', key, '-out',
                                    path, '-name', name, '-passout', 'pass:'],
                                    stdout=subprocess.PIPE,
                                    stderr=subprocess.PIPE)
            proc.wait()
            if proc.returncode:
                raise Exception(proc.stderr.read())

            # Load p12 file to the database
            proc = subprocess.Popen(['pk12util', '-i', path, '-d',
                                    'sql:/etc/ipsec.d/', '-W', ''],
                                    stdout=subprocess.PIPE,
                                    stderr=subprocess.PIPE)
            proc.wait()
            if proc.returncode:
                raise Exception(proc.stderr.read())

        except Exception as e:
            vlog.err("Import cert and key failed.\n" + str(e))
        os.remove(path)

    def _nss_delete_cert_and_key(self, name):
        try:
            # Delete certificate and private key
            proc = subprocess.Popen(['certutil', '-F', '-d',
                                    'sql:/etc/ipsec.d/', '-n', name],
                                    stdout=subprocess.PIPE,
                                    stderr=subprocess.PIPE)
            proc.wait()
            if proc.returncode:
                raise Exception(proc.stderr.read())

        except Exception as e:
            vlog.err("Delete cert and key failed.\n" + str(e))


class IPsecTunnel(object):
    """This is the base class for IPsec tunnel."""

    unixctl_config_tmpl = Template("""\
  Tunnel Type:    $tunnel_type
  Remote IP:      $remote_ip
  SKB mark:       $skb_mark
  Local cert:     $certificate
  Local name:     $local_name
  Local key:      $private_key
  Remote cert:    $remote_cert
  Remote name:    $remote_name
  CA cert:        $ca_cert
  PSK:            $psk
""")

    unixctl_status_tmpl = Template("""\
  Ofport:         $ofport
  CFM state:      $cfm_state
""")

    def __init__(self, name, row):
        self.name = name  # 'name' will not change because it is key in OVSDB
        self.version = 0  # 'version' is increased on configuration changes
        self.last_refreshed_version = -1
        self.state = "INIT"
        self.conf = {}
        self.status = {}
        self.update_conf(row)

    def update_conf(self, row):
        """This function updates IPsec tunnel configuration by using 'row'
        from OVSDB interface table.  If configuration was actually changed
        in OVSDB then this function returns True.  Otherwise, it returns
        False."""
        ret = False
        options = row.options
        remote_cert = options.get("remote_cert")
        remote_name = options.get("remote_name")
        if remote_cert:
            remote_name = monitor._get_cn_from_cert(remote_cert)

        new_conf = {
            "ifname": self.name,
            "tunnel_type": row.type,
            "remote_ip": options.get("remote_ip"),
            "skb_mark": monitor.conf["skb_mark"],
            "certificate": monitor.conf["pki"]["certificate"],
            "private_key": monitor.conf["pki"]["private_key"],
            "ca_cert": monitor.conf["pki"]["ca_cert"],
            "remote_cert": remote_cert,
            "remote_name": remote_name,
            "local_name": monitor.conf["pki"]["local_name"],
            "psk": options.get("psk")}

        if self.conf != new_conf:
            # Configuration was updated in OVSDB.  Validate it and figure
            # out what to do next with this IPsec tunnel.  Also, increment
            # version number of this IPsec tunnel so that we could tell
            # apart old and new tunnels in "ipsec status" output.
            self.version += 1
            ret = True
            self.conf = new_conf

            if self._is_valid_tunnel_conf():
                self.state = "CONFIGURED"
            else:
                vlog.warn("%s contains invalid configuration%s" %
                          (self.name, self.invalid_reason))
                self.state = "INVALID"

        new_status = {
            "cfm_state": "Up" if row.cfm_fault == [False] else
                         "Down" if row.cfm_fault == [True] else
                         "Disabled",
            "ofport": "Not assigned" if (row.ofport in [[], [-1]]) else
                      row.ofport[0]}

        if self.status != new_status:
            # Tunnel has become unhealthy or ofport changed.  Simply log this.
            vlog.dbg("%s changed status from %s to %s" %
                     (self.name, str(self.status), str(new_status)))
            self.status = new_status
        return ret

    def mark_for_removal(self):
        """This function marks tunnel for removal."""
        self.version += 1
        self.state = "REMOVED"

    def show(self, policies, securities, conns):
        state = self.state
        if self.state == "INVALID":
            state += self.invalid_reason
        header = "Interface name: %s v%u (%s)\n" % (self.name, self.version,
                                                    state)
        conf = self.unixctl_config_tmpl.substitute(self.conf)
        status = self.unixctl_status_tmpl.substitute(self.status)
        spds = "Kernel policies installed:\n"
        remote_ip = self.conf["remote_ip"]
        if remote_ip in policies:
            for line in policies[remote_ip]:
                spds += "  " + line + "\n"
        sas = "Kernel security associations installed:\n"
        if remote_ip in securities:
            for line in securities[remote_ip]:
                sas += "  " + line + "\n"
        cons = "IPsec connections that are active:\n"
        if self.name in conns:
            for tname in conns[self.name]:
                cons += "  " + conns[self.name][tname] + "\n"

        return header + conf + status + spds + sas + cons + "\n"

    def _is_valid_tunnel_conf(self):
        """This function verifies if IPsec tunnel has valid configuration
        set in 'conf'.  If it is valid, then it returns True.  Otherwise,
        it returns False and sets the reason why configuration was considered
        as invalid.

        This function could be improved in future to also verify validness
        of certificates themselves so that ovs-monitor-ipsec would not
        pass malformed configuration to IKE daemon."""

        self.invalid_reason = None

        if not self.conf["remote_ip"]:
            self.invalid_reason = ": 'remote_ip' is not set"
            return False

        if self.conf["psk"]:
            if self.conf["certificate"] or self.conf["private_key"] \
                    or self.conf["ca_cert"] or self.conf["remote_cert"] \
                    or self.conf["remote_name"]:
                self.invalid_reason = ": 'certificate', 'private_key', "\
                                      "'ca_cert', 'remote_cert', and "\
                                      "'remote_name' must be unset with PSK"
                return False
        # If configuring authentication with CA-signed certificate or
        # self-signed certificate, the 'remote_name' should be specified at
        # this point.  When using CA-signed certificate, the 'remote_name' is
        # read from interface's options field. When using self-signed
        # certificate, the 'remote_name' is extracted from the 'remote_cert'
        # file.
        elif self.conf["remote_name"]:
            if not self.conf["certificate"]:
                self.invalid_reason = ": must set 'certificate' as local"\
                                      " certificate when using CA-signed"\
                                      " certificate or self-signed"\
                                      " certificate to authenticate peers"
                return False
            elif not self.conf["private_key"]:
                self.invalid_reason = ": must set 'private_key' as local"\
                                      " private key when using CA-signed"\
                                      " certificate or self-signed"\
                                      " certificate to authenticate peers"
                return False
            if not self.conf["remote_cert"] and not self.conf["ca_cert"]:
                self.invalid_reason = ": must set 'remote_cert' when using"\
                                      " self-signed certificate"\
                                      " authentication or 'ca_cert' when"\
                                      " using CA-signed certificate"\
                                      " authentication"
                return False
        else:
            self.invalid_reason = ": must choose a authentication method"
            return False

        return True


class IPsecMonitor(object):
    """This class monitors and configures IPsec tunnels"""

    def __init__(self, root_prefix, ike_daemon):
        self.IPSEC = root_prefix + "/usr/sbin/ipsec"
        self.tunnels = {}

        # Global configuration shared by all tunnels
        self.conf = {
            "pki": {
                "private_key": None,
                "certificate": None,
                "ca_cert": None,
                "local_name": None
            },
            "skb_mark": None
        }
        self.conf_in_use = copy.deepcopy(self.conf)

        # Choose to either use StrongSwan or LibreSwan as IKE daemon
        if ike_daemon == "strongswan":
            self.ike_helper = StrongSwanHelper(root_prefix)
        elif ike_daemon == "libreswan":
            self.ike_helper = LibreSwanHelper(root_prefix)
        else:
            vlog.err("The IKE daemon should be strongswan or libreswan.")
            sys.exit(1)

        # Check whether ipsec command is available
        if not os.path.isfile(self.IPSEC) or \
                not os.access(self.IPSEC, os.X_OK):
            vlog.err("IKE daemon is not installed in the system.")

        self.ike_helper.restart_ike_daemon()

    def is_tunneling_type_supported(self, tunnel_type):
        """Returns True if we know how to configure IPsec for these
        types of tunnels.  Otherwise, returns False."""
        return tunnel_type in ["gre", "geneve", "vxlan", "stt"]

    def is_ipsec_required(self, options_column):
        """Return True if tunnel needs to be encrypted.  Otherwise,
        returns False."""
        return "psk" in options_column or \
                "remote_name" in options_column or \
                "remote_cert" in options_column

    def add_tunnel(self, name, row):
        """Adds a new tunnel that monitor will provision with 'name'."""
        vlog.info("Tunnel %s appeared in OVSDB" % (name))
        self.tunnels[name] = IPsecTunnel(name, row)

    def update_tunnel(self, name, row):
        """Updates configuration of already existing tunnel with 'name'."""
        tunnel = self.tunnels[name]
        if tunnel.update_conf(row):
            vlog.info("Tunnel's '%s' configuration changed in OVSDB to %u" %
                      (tunnel.name, tunnel.version))

    def del_tunnel(self, name):
        """Deletes tunnel by 'name'."""
        vlog.info("Tunnel %s disappeared from OVSDB" % (name))
        self.tunnels[name].mark_for_removal()

    def update_conf(self, pki, skb_mark):
        """Update the global configuration for IPsec tunnels"""
        self.conf["pki"]["certificate"] = pki[0]
        self.conf["pki"]["private_key"] = pki[1]
        self.conf["pki"]["ca_cert"] = pki[2]
        self.conf["pki"]["local_name"] = pki[3]

        # Update skb_mark used in IPsec policies.
        self.conf["skb_mark"] = skb_mark

    def read_ovsdb_open_vswitch_table(self, data):
        """This functions reads IPsec relevant configuration from Open_vSwitch
        table."""
        pki = [None, None, None, None]
        skb_mark = None
        is_valid = False

        for row in data["Open_vSwitch"].rows.itervalues():
            pki[0] = row.other_config.get("certificate")
            pki[1] = row.other_config.get("private_key")
            pki[2] = row.other_config.get("ca_cert")
            skb_mark = row.other_config.get("ipsec_skb_mark")

        # Test whether it's a valid configration
        if pki[0] and pki[1]:
            pki[3] = self._get_cn_from_cert(pki[0])
            if pki[3]:
                is_valid = True
        elif not pki[0] and not pki[1] and not pki[2]:
            is_valid = True

        if not is_valid:
            vlog.warn("The cert and key configuration is not valid. "
                "The valid configuations are 1): certificate, private_key "
                "and ca_cert are not set; or 2): certificate and "
                "private_key are all set.")
        else:
            self.update_conf(pki, skb_mark)

    def read_ovsdb_interface_table(self, data):
        """This function reads the IPsec relevant configuration from Interface
        table."""
        ifaces = set()

        for row in data["Interface"].rows.itervalues():
            if not self.is_tunneling_type_supported(row.type):
                continue
            if not self.is_ipsec_required(row.options):
                continue
            if row.name in self.tunnels:
                self.update_tunnel(row.name, row)
            else:
                self.add_tunnel(row.name, row)
            ifaces.add(row.name)

        # Mark for removal those tunnels that just disappeared from OVSDB
        for tunnel in self.tunnels.keys():
            if tunnel not in ifaces:
                self.del_tunnel(tunnel)

    def read_ovsdb(self, data):
        """This function reads all configuration from OVSDB that
        ovs-monitor-ipsec is interested in."""
        self.read_ovsdb_open_vswitch_table(data)
        self.read_ovsdb_interface_table(data)

    def show(self, unix_conn, policies, securities):
        """This function prints all tunnel state in 'unix_conn'.
        It uses 'policies' and securities' received from Linux Kernel
        to show if tunnels were actually configured by the IKE deamon."""
        if not self.tunnels:
            unix_conn.reply("No tunnels configured with IPsec")
            return
        s = ""
        conns = self.ike_helper.get_active_conns()
        for name, tunnel in self.tunnels.iteritems():
            s += tunnel.show(policies, securities, conns)
        unix_conn.reply(s)

    def run(self):
        """This function runs state machine that represents whole
        IPsec configuration (i.e. merged together from individual
        tunnel state machines).  It creates configuration files and
        tells IKE daemon to update configuration."""
        needs_refresh = False
        removed_tunnels = []

        self.ike_helper.config_init()

        if self.ike_helper.config_global(self):
            needs_refresh = True

        for name, tunnel in self.tunnels.iteritems():
            if tunnel.last_refreshed_version != tunnel.version:
                tunnel.last_refreshed_version = tunnel.version
                needs_refresh = True

            if tunnel.state == "REMOVED" or tunnel.state == "INVALID":
                removed_tunnels.append(name)
            elif tunnel.state == "CONFIGURED":
                self.ike_helper.config_tunnel(self.tunnels[name])

        self.ike_helper.config_fini()

        for name in removed_tunnels:
            # LibreSwan needs to clear state from database
            if hasattr(self.ike_helper, "clear_tunnel_state"):
                self.ike_helper.clear_tunnel_state(self.tunnels[name])
            del self.tunnels[name]

        if needs_refresh:
            self.ike_helper.refresh(self)

    def _get_cn_from_cert(self, cert):
        try:
            proc = subprocess.Popen(['openssl', 'x509', '-noout', '-subject',
                                    '-nameopt', 'RFC2253', '-in', cert],
                                    stdout=subprocess.PIPE,
                                    stderr=subprocess.PIPE)
            proc.wait()
            if proc.returncode:
                raise Exception(proc.stderr.read())
            m = re.search(r"CN=(.+?),", proc.stdout.readline())
            if not m:
                raise Exception("No CN in the certificate subject.")
        except Exception as e:
            vlog.warn(str(e))
            return None

        return m.group(1)


def unixctl_xfrm_policies(conn, unused_argv, unused_aux):
    global xfrm
    policies = xfrm.get_policies()
    conn.reply(str(policies))


def unixctl_xfrm_state(conn, unused_argv, unused_aux):
    global xfrm
    securities = xfrm.get_securities()
    conn.reply(str(securities))


def unixctl_ipsec_status(conn, unused_argv, unused_aux):
    global monitor
    conns = monitor.ike_helper.get_active_conns()
    conn.reply(str(conns))


def unixctl_show(conn, unused_argv, unused_aux):
    global monitor
    global xfrm
    policies = xfrm.get_policies()
    securities = xfrm.get_securities()
    monitor.show(conn, policies, securities)


def unixctl_refresh(conn, unused_argv, unused_aux):
    global monitor
    monitor.ike_helper.refresh(monitor)
    conn.reply(None)


def unixctl_exit(conn, unused_argv, unused_aux):
    global monitor
    global exiting
    exiting = True

    # Make sure persistent global states are cleared
    monitor.update_conf([None, None, None, None], None)
    # Make sure persistent tunnel states are cleared
    for tunnel in monitor.tunnels.keys():
        monitor.del_tunnel(tunnel)
    monitor.run()

    conn.reply(None)


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("database", metavar="DATABASE",
                        help="A socket on which ovsdb-server is listening.")
    parser.add_argument("--root-prefix", metavar="DIR",
                        help="Use DIR as alternate root directory"
                        " (for testing).")
    parser.add_argument("--ike-daemon", metavar="IKE-DAEMON",
                        help="The IKE daemon used for IPsec tunnels"
                        " (either libreswan or strongswan).")

    ovs.vlog.add_args(parser)
    ovs.daemon.add_args(parser)
    args = parser.parse_args()
    ovs.vlog.handle_args(args)
    ovs.daemon.handle_args(args)

    global monitor
    global xfrm

    root_prefix = args.root_prefix if args.root_prefix else ""
    xfrm = XFRM(root_prefix)
    monitor = IPsecMonitor(root_prefix, args.ike_daemon)

    remote = args.database
    schema_helper = ovs.db.idl.SchemaHelper()
    schema_helper.register_columns("Interface",
                                   ["name", "type", "options", "cfm_fault",
                                    "ofport"])
    schema_helper.register_columns("Open_vSwitch", ["other_config"])
    idl = ovs.db.idl.Idl(remote, schema_helper)

    ovs.daemon.daemonize()

    ovs.unixctl.command_register("xfrm/policies", "", 0, 0,
                                 unixctl_xfrm_policies, None)
    ovs.unixctl.command_register("xfrm/state", "", 0, 0,
                                 unixctl_xfrm_state, None)
    ovs.unixctl.command_register("ipsec/status", "", 0, 0,
                                 unixctl_ipsec_status, None)
    ovs.unixctl.command_register("tunnels/show", "", 0, 0,
                                 unixctl_show, None)
    ovs.unixctl.command_register("refresh", "", 0, 0, unixctl_refresh, None)
    ovs.unixctl.command_register("exit", "", 0, 0, unixctl_exit, None)

    error, unixctl_server = ovs.unixctl.server.UnixctlServer.create(None)
    if error:
        ovs.util.ovs_fatal(error, "could not create unixctl server", vlog)

    # Sequence number when OVSDB was processed last time
    seqno = idl.change_seqno

    while True:
        unixctl_server.run()
        if exiting:
            break

        idl.run()
        if seqno != idl.change_seqno:
            monitor.read_ovsdb(idl.tables)
            seqno = idl.change_seqno

        monitor.run()

        poller = ovs.poller.Poller()
        unixctl_server.wait(poller)
        idl.wait(poller)
        poller.block()

    unixctl_server.close()
    idl.close()


if __name__ == '__main__':
    try:
        main()
    except SystemExit:
        # Let system.exit() calls complete normally
        raise
    except:
        vlog.exception("traceback")
        sys.exit(ovs.daemon.RESTART_EXIT_CODE)