# Authors: Simo Sorce <ssorce@redhat.com>
#
# Copyright (C) 2007  Red Hat
# see file 'COPYING' for use and warranty information
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

import socket
import os
import logging
import ipapython.dnsclient
import tempfile
import ldap
from ldap import LDAPError
from ipapython.ipautil import run, CalledProcessError, valid_ip


NOT_FQDN = -1
NO_LDAP_SERVER = -2
REALM_NOT_FOUND = -3
NOT_IPA_SERVER = -4
BAD_HOST_CONFIG = -10

class IPADiscovery:

    def __init__(self):
        self.realm = None
        self.domain = None
        self.server = None
        self.basedn = None

    def __get_resolver_domains(self):
        """
        Read /etc/resolv.conf and return all the domains found in domain and
        search.

        Returns a list
        """
        domains = []
        domain = None
        try:
            fp = open('/etc/resolv.conf', 'r')
            lines = fp.readlines()
            fp.close()

            for line in lines:
                if line.lower().startswith('domain'):
                    domain = line.split(None)[-1]
                elif line.lower().startswith('search'):
                    domains = domains + line.split(None)[1:]
        except:
            pass
        if domain and not domain in domains:
            domains = [domain] + domains
        return domains

    def getServerName(self):
        return self.server

    def getDomainName(self):
        return self.domain

    def getRealmName(self):
        return self.realm

    def getKDCName(self):
        return self.kdc

    def getBaseDN(self):
        return self.basedn

    def check_domain(self, domain):
        """
        Given a domain search it for SRV records, breaking it down to search
        all subdomains too.

        Returns a tuple (server, domain) or (None,None) if a SRV record
        isn't found.
        """
        server = None
        while not server:
            logging.debug("[ipadnssearchldap("+domain+")]")
            server = self.ipadnssearchldap(domain)
            if server:
                return (server, domain)
            else:
                p = domain.find(".")
                if p == -1: #no ldap server found and last component of the domain already tested
                    return (None, None)
                domain = domain[p+1:]
        return (None, None)

    def search(self, domain = "", server = "", hostname=None):
        qname = ""
        results = []
        result = []
        krbret = []
        ldapret = []

        if not server:

            if not domain: #domain not provided do full DNS discovery

                # get the local host name
                if not hostname:
                    hostname = socket.getfqdn()
                if not hostname:
                    return BAD_HOST_CONFIG

                if valid_ip(hostname):
                    return NOT_FQDN

                # first, check for an LDAP server for the local domain
                p = hostname.find(".")
                if p == -1: #no domain name
                    return NOT_FQDN
                domain = hostname[p+1:]

                # Get the list of domains from /etc/resolv.conf, we'll search
                # them all. We search the domain of our hostname first though,
                # even if that means searching it twice. This is to avoid the
                # situation where domain isn't set in /etc/resolv.conf and
                # the search list has the hostname domain not first. We could
                # end up with the wrong SRV record.
                domains = self.__get_resolver_domains()
                domains = [domain] + domains
                for domain in domains:
                    (server, domain) = self.check_domain(domain)
                    if server:
                        self.server = server
                        self.domain = domain
                        break
                if not self.domain: #no ldap server found
                    return NO_LDAP_SERVER
            else:
                logging.debug("[ipadnssearchldap]")
                self.server = self.ipadnssearchldap(domain)
                if self.server:
                    self.domain = domain
                else:
                    return NO_LDAP_SERVER

        else: #server forced on us, this means DNS doesn't work :/

            self.domain = domain
            self.server = server

        #search for kerberos
        logging.debug("[ipadnssearchkrb]")
        krbret = self.ipadnssearchkrb(self.domain)
        if not server and not krbret[0]:
            return REALM_NOT_FOUND

        self.realm = krbret[0]
        self.kdc = krbret[1]

        logging.debug("[ipacheckldap]")
        # check ldap now
        ldapret = self.ipacheckldap(self.server, self.realm)

        if not ldapret:
            return NOT_IPA_SERVER

        self.server = ldapret[0]
        self.realm = ldapret[1]

        return 0

    def ipacheckldap(self, thost, trealm):
        """
        Given a host and kerberos realm verify that it is an IPA LDAP
        server hosting the realm. The connection is an SSL connection
        so the remote IPA CA cert must be available at
        http://HOST/ipa/config/ca.crt

        Returns a list [host, realm] or an empty list on error.
        """

        lret = []
        lres = []
        lattr = ""
        linfo = ""
        lrealms = []

        i = 0

        # Get the CA certificate
        try:
            # Create TempDir
            temp_ca_dir = tempfile.mkdtemp()
        except OSError, e:
            raise RuntimeError("Creating temporary directory failed: %s" % str(e))

        try:
            run(["/usr/bin/wget", "-O", "%s/ca.crt" % temp_ca_dir, "http://%s/ipa/config/ca.crt" % thost])
        except CalledProcessError, e:
            logging.debug('Retrieving CA from %s failed.\n%s' % (thost, str(e)))
            return []

        #now verify the server is really an IPA server
        try:
            logging.debug("Init ldap with: ldap://"+thost+":389")
            lh = ldap.initialize("ldap://"+thost+":389")
            ldap.set_option(ldap.OPT_X_TLS_REQUIRE_CERT, True)
            ldap.set_option(ldap.OPT_X_TLS_CACERTFILE, "%s/ca.crt" % temp_ca_dir)
            lh.set_option(ldap.OPT_PROTOCOL_VERSION, 3)
            lh.set_option(ldap.OPT_X_TLS_DEMAND, True)
            lh.start_tls_s()
            lh.simple_bind_s("","")

            logging.debug("Search rootdse")
            lret = lh.search_s("", ldap.SCOPE_BASE, "(objectClass=*)")
            for lattr in lret[0][1]:
                if lattr.lower() == "namingcontexts":
                    self.basedn = lret[0][1][lattr][0]

            logging.debug("Search for (info=*) in "+self.basedn+"(base)")
            lret = lh.search_s(self.basedn, ldap.SCOPE_BASE, "(info=IPA*)")
            if not lret:
                return []
            logging.debug("Found: "+str(lret))

            for lattr in lret[0][1]:
                if lattr.lower() == "info":
                    linfo = lret[0][1][lattr][0].lower()
                    break

            if not linfo or linfo.lower() != 'ipa v2.0':
                return []

            #search and return known realms
            logging.debug("Search for (objectClass=krbRealmContainer) in "+self.basedn+"(sub)")
            lret = lh.search_s("cn=kerberos,"+self.basedn, ldap.SCOPE_SUBTREE, "(objectClass=krbRealmContainer)")
            if not lret:
                #something very wrong
                return []
            logging.debug("Found: "+str(lret))

            for lres in lret:
                for lattr in lres[1]:
                    if lattr.lower() == "cn":
                        lrealms.append(lres[1][lattr][0])


            if trealm:
                for r in lrealms:
                    if trealm == r:
                        return [thost, trealm]
                # must match or something is very wrong
                return []
            else:
                if len(lrealms) != 1:
                    #which one? we can't attach to a multi-realm server without DNS working
                    return []
                else:
                    return [thost, lrealms[0]]

            #we shouldn't get here
            return []

        except LDAPError, err:
            if not isinstance(err, ldap.TIMEOUT):
                logging.error("LDAP Error: %s: %s" %
                   (err.args[0]['desc'], err.args[0].get('info', '')))
            else:
                logging.error("LDAP Error: timeout")
            return []

        finally:
            os.remove("%s/ca.crt" % temp_ca_dir)
            os.removedirs(temp_ca_dir)


    def ipadnssearchldap(self, tdomain):
        servers = ""
        rserver = ""

        qname = "_ldap._tcp."+tdomain
        # terminate the name
        if not qname.endswith("."):
            qname += "."
        results = ipapython.dnsclient.query(qname, ipapython.dnsclient.DNS_C_IN, ipapython.dnsclient.DNS_T_SRV)

        for result in results:
            if result.dns_type == ipapython.dnsclient.DNS_T_SRV:
                rserver = result.rdata.server.rstrip(".")
                if result.rdata.port and result.rdata.port != 389:
                    rserver += ":" + str(result.rdata.port)
                if servers:
                    servers += "," + rserver
                else:
                    servers = rserver
                break

        return servers

    def ipadnssearchkrb(self, tdomain):
        realm = ""
        kdc = ""
        # now, check for a Kerberos realm the local host or domain is in
        qname = "_kerberos." + tdomain
        # terminate the name
        if not qname.endswith("."):
            qname += "."
        results = ipapython.dnsclient.query(qname, ipapython.dnsclient.DNS_C_IN, ipapython.dnsclient.DNS_T_TXT)

        for result in results:
            if result.dns_type == ipapython.dnsclient.DNS_T_TXT:
                realm = result.rdata.data
                if realm:
                    break

        if realm:
            # now fetch server information for the realm
            qname = "_kerberos._udp." + realm.lower()
            # terminate the name
            if not qname.endswith("."):
                qname += "."
            results = ipapython.dnsclient.query(qname, ipapython.dnsclient.DNS_C_IN, ipapython.dnsclient.DNS_T_SRV)
            for result in results:
                if result.dns_type == ipapython.dnsclient.DNS_T_SRV:
                    qname = result.rdata.server.rstrip(".")
                    if result.rdata.port and result.rdata.port != 88:
                        qname += ":" + str(result.rdata.port)
                    if kdc:
                        kdc += "," + qname
                    else:
                        kdc = qname

            if not kdc:
                logging.debug("SRV record for KDC not found! Realm: %s, SRV record: %s" % (realm, qname))

        return [realm, kdc]