# 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

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 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 = ""
        qname = ""
        results = []
        result = []
        krbret = []
        ldapret = []

        if not server:

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

                # get the local host name
                hostname = socket.getfqdn()
                if not hostname:
                    return -10 #bad host configuration

                # first, check for an LDAP server for the local domain
                p = hostname.find(".")
                if p == -1: #no domain name
                    return -1
                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 -1
            else:
                logging.debug("[ipadnssearchldap]")
                self.server = self.ipadnssearchldap(domain)
                if self.server:
                    self.domain = domain
                else:
                    return -2 #no ldap server found


            #search for kerberos TODO: move this after ipacheckldap()
            logging.debug("[ipadnssearchkrb]")
            krbret = self.ipadnssearchkrb(self.domain)
            if not krbret:
                return -3 #no krb server found

            self.realm = krbret[0]

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

            self.domain = domain
            self.server = server

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

        if not ldapret:
            return -4 # not an IPA server (or broken config)

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

        return 0

    def ipacheckldap(self, thost, trealm):

        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:
            raise RuntimeError('Retrieving CA from %s failed.\n%s' % (thost, str(e)))

        #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:
                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." + 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:
                    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

        return [realm, kdc]