# Authors:
#   Jason Gerard DeRose <jderose@redhat.com>
#   Rob Crittenden <rcritten@redhat.com>
#   Pavel Zuna <pzuna@redhat.com>
#
# Copyright (C) 2008  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; version 2 only
#
# 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, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
"""
Services

A IPA service represents a service that runs on a host. The IPA service
record can store a Kerberos principal, an SSL certificate, or both.

An IPA service can be managed directly from a machine, provided that
machine has been given the correct permission. This is true even for
machines other than the one the service is associated with. For example,
requesting an SSL certificate using the host service principal credentials
of the host. To manage a services using a host credentials you need to
kinit as the host:

 # kinit -kt /etc/krb5.keytab host/ipa.example.com@EXAMPLE.COM

Adding an IPA service allows the associated service to request an SSL
certificate or keytab, but this is performed as a separate step; they
are not produced as a result of adding the service.

Only the public aspect of a certificate is stored in a service record;
the private key is not stored.

EXAMPLES:

 Add a new IPA service:
   ipa service-add HTTP/web.example.com

 Allow a host to manage an IPA service certificate:
  ipa service-add-host --hosts=web.example.com HTTP/web.example.com
  ipa rolegroup-add-member --hosts=web.example.com certadmin

 Delete an IPA service:
   ipa service-del HTTP/web.example.com

 Find all IPA services assicated with a host:
   ipa service-find web.example.com

 Find all HTTP services:
   ipa service-find HTTP

 Disable a service Kerberos key:
   ipa service-disable HTTP/web.example.com

 Request a certificate for an IPA service:
   ipa cert-request --principal=HTTP/web.example.com example.csr

 Generate and retrieve a keytab for an IPA service:
   ipa-getkeytab -s ipa.example.com -p HTTP/web.example.com -k /etc/httpd/httpd.keytab

"""
import base64

from ipalib import api, errors, util
from ipalib import Str, Flag, Bytes
from ipalib.plugins.baseldap import *
from ipalib import x509
from ipalib import _, ngettext
from ipalib import util
import nss.nss as nss
from nss.error import NSPRError


output_params = (
    Flag('has_keytab',
        label=_('Keytab'),
    ),
    Str('managedby_host',
        label='Managed by',
    ),
)

def split_principal(principal):
    service = hostname = realm = None

    # Break down the principal into its component parts, which may or
    # may not include the realm.
    sp = principal.split('/')
    if len(sp) != 2:
        raise errors.MalformedServicePrincipal(reason='missing service')

    service = sp[0]
    sr = sp[1].split('@')
    if len(sr) > 2:
        raise errors.MalformedServicePrincipal(
            reason='unable to determine realm'
        )

    hostname = sr[0].lower()
    if len(sr) == 2:
        realm = sr[1].upper()
        # At some point we'll support multiple realms
        if realm != api.env.realm:
            raise errors.RealmMismatch()
    else:
        realm = api.env.realm

    # Note that realm may be None.
    return (service, hostname, realm)

def validate_principal(ugettext, principal):
    (service, hostname, principal) = split_principal(principal)
    return None

def normalize_principal(principal):
    # The principal is already validated when it gets here
    (service, hostname, realm) = split_principal(principal)
    # Put the principal back together again
    principal = '%s/%s@%s' % (service, hostname, realm)
    return unicode(principal)

def validate_certificate(ugettext, cert):
    """
    For now just verify that it is properly base64-encoded.
    """
    if cert and util.isvalid_base64(cert):
        try:
            base64.b64decode(cert)
        except Exception, e:
            raise errors.Base64DecodeError(reason=str(e))
    else:
        # We'll assume this is DER data
        pass

def normalize_certificate(cert):
    """
    Incoming certificates should be DER-encoded.

    Note that this can't be a normalizer on the Param because only unicode
    variables are normalized.
    """
    if not cert:
        return cert

    if util.isvalid_base64(cert):
        try:
            cert = base64.b64decode(cert)
        except Exception, e:
            raise errors.Base64DecodeError(reason=str(e))

    # At this point we should have a certificate, either because the data
    # was base64-encoded and now its not or it came in as DER format.
    # Let's decode it and see. Fetching the serial number will pass the
    # certificate through the NSS DER parser.
    try:
        serial = unicode(x509.get_serial_number(cert, x509.DER))
    except NSPRError, nsprerr:
        if nsprerr.errno == -8183: # SEC_ERROR_BAD_DER
            raise errors.CertificateFormatError(error='improperly formatted DER-encoded certificate')
        else:
            raise errors.CertificateFormatError(error=str(nsprerr))

    return cert


class service(LDAPObject):
    """
    Service object.
    """
    container_dn = api.env.container_service
    object_name = 'service'
    object_name_plural = 'services'
    object_class = [
        'krbprincipal', 'krbprincipalaux', 'krbticketpolicyaux', 'ipaobject',
        'ipaservice', 'pkiuser'
    ]
    search_attributes = ['krbprincipalname', 'managedby']
    default_attributes = ['krbprincipalname', 'usercertificate', 'managedby', 'krblastpwdchange']
    uuid_attribute = 'ipauniqueid'
    attribute_members = {
        'managedby': ['host'],
    }

    label = _('Services')

    takes_params = (
        Str('krbprincipalname', validate_principal,
            cli_name='principal',
            label=_('Principal'),
            doc=_('Service principal'),
            primary_key=True,
            normalizer=lambda value: normalize_principal(value),
        ),
        Bytes('usercertificate?', validate_certificate,
            cli_name='certificate',
            label=_('Certificate'),
            doc=_('Base-64 encoded server certificate'),
        )
    )

api.register(service)


class service_add(LDAPCreate):
    """
    Add a new IPA new service.
    """
    msg_summary = _('Added service "%(value)s"')
    member_attributes = ['managedby']
    has_output_params = LDAPCreate.has_output_params + output_params
    takes_options = (
        Flag('force',
            doc=_('force principal name even if not in DNS'),
        ),
    )
    def pre_callback(self, ldap, dn, entry_attrs, attrs_list, *keys, **options):
        (service, hostname, realm) = split_principal(keys[-1])
        if service.lower() == 'host' and not options['force']:
            raise errors.HostService()

        try:
            hostresult = api.Command['host_show'](hostname)['result']
        except errors.NotFound:
            raise errors.NotFound(reason="The host '%s' does not exist to add a service to." % hostname)

        cert = options.get('usercertificate')
        if cert:
            entry_attrs['usercertificate'] = normalize_certificate(cert)

        if not options.get('force', False):
             # We know the host exists if we've gotten this far but we
             # really want to discourage creating services for hosts that
             # don't exist in DNS.
             util.validate_host_dns(self.log, hostname)
        if not 'managedby' in entry_attrs:
             entry_attrs['managedby'] = hostresult['dn']

        return dn

api.register(service_add)


class service_del(LDAPDelete):
    """
    Delete an IPA service.
    """
    msg_summary = _('Deleted service "%(value)s"')
    member_attributes = ['managedby']
    def pre_callback(self, ldap, dn, *keys, **options):
        if self.api.env.enable_ra:
            (dn, entry_attrs) = ldap.get_entry(dn, ['usercertificate'])
            cert = entry_attrs.get('usercertificate')
            if cert:
                cert = cert[0]
                try:
                    serial = unicode(x509.get_serial_number(cert, x509.DER))
                    try:
                        result = api.Command['cert_show'](unicode(serial))['result']
                        if 'revocation_reason' not in result:
                            try:
                                api.Command['cert_revoke'](unicode(serial), revocation_reason=4)
                            except errors.NotImplementedError:
                                # some CA's might not implement revoke
                                pass
                    except errors.NotImplementedError:
                        # some CA's might not implement revoke
                        pass
                except NSPRError, nsprerr:
                    if nsprerr.errno == -8183:
                        # If we can't decode the cert them proceed with
                        # removing the service.
                        self.log.info("Problem decoding certificate %s" % nsprerr.args[1])
                    else:
                        raise nsprerr
        return dn

api.register(service_del)


class service_mod(LDAPUpdate):
    """
    Modify an existing IPA service.
    """
    msg_summary = _('Modified service "%(value)s"')
    takes_options = LDAPUpdate.takes_options
    has_output_params = LDAPUpdate.has_output_params + output_params

    member_attributes = ['managedby']

    def pre_callback(self, ldap, dn, entry_attrs, *keys, **options):
        if 'usercertificate' in options:
            cert = options.get('usercertificate')
            cert = normalize_certificate(cert)
            if cert:
                (dn, entry_attrs_old) = ldap.get_entry(dn, ['usercertificate'])
                if 'usercertificate' in entry_attrs_old:
                    # FIXME: what to do here? do we revoke the old cert?
                    fmt = 'entry already has a certificate, serial number: %s' % (
                        x509.get_serial_number(entry_attrs_old['usercertificate'][0], x509.DER)
                    )
                    raise errors.GenericError(format=fmt)
                entry_attrs['usercertificate'] = cert
            else:
                entry_attrs['usercertificate'] = None
        return dn

api.register(service_mod)


class service_find(LDAPSearch):
    """
    Search for IPA services.
    """
    msg_summary = ngettext(
        '%(count)d service matched', '%(count)d services matched'
    )
    member_attributes = ['managedby']
    takes_options = LDAPSearch.takes_options
    has_output_params = LDAPSearch.has_output_params + output_params
    def pre_callback(self, ldap, filter, attrs_list, base_dn, *args, **options):
        # lisp style!
        custom_filter = '(&(objectclass=ipaService)' \
                          '(!(objectClass=posixAccount))' \
                          '(!(|(krbprincipalname=kadmin/*)' \
                              '(krbprincipalname=K/M@*)' \
                              '(krbprincipalname=krbtgt/*))' \
                          ')' \
                        ')'
        return ldap.combine_filters(
            (custom_filter, filter), rules=ldap.MATCH_ALL
        )

    def post_callback(self, ldap, entries, truncated, *args, **options):
        for entry in entries:
            entry_attrs = entry[1]
            if 'krblastpwdchange' in entry_attrs:
                entry_attrs['has_keytab'] = True
                if not options.get('all', False):
                    del entry_attrs['krblastpwdchange']
            else:
                entry_attrs['has_keytab'] = False

api.register(service_find)


class service_show(LDAPRetrieve):
    """
    Display information about an IPA service.
    """
    member_attributes = ['managedby']
    takes_options = LDAPRetrieve.takes_options

    has_output_params = LDAPRetrieve.has_output_params + output_params + (
        Str('subject',
            label=_('Subject'),
        ),
        Str('serial_number',
            label=_('Serial Number'),
        ),
        Str('issuer',
            label=_('Issuer'),
        ),
        Str('valid_not_before',
            label=_('Not Before'),
        ),
        Str('valid_not_after',
            label=_('Not After'),
        ),
        Str('md5_fingerprint',
            label=_('Fingerprint (MD5)'),
        ),
        Str('sha1_fingerprint',
            label=_('Fingerprint (SHA1)'),
        ),
        Str('revocation_reason?',
            label=_('Revocation reason'),
        )
    )

    def post_callback(self, ldap, dn, entry_attrs, *keys, **options):
        if 'krblastpwdchange' in entry_attrs:
            entry_attrs['has_keytab'] = True
            if not options.get('all', False):
                del entry_attrs['krblastpwdchange']
        else:
            entry_attrs['has_keytab'] = False

        if 'usercertificate' in entry_attrs:
            cert = x509.load_certificate(entry_attrs['usercertificate'][0], datatype=x509.DER)
            entry_attrs['subject'] = unicode(cert.subject)
            entry_attrs['serial_number'] = unicode(cert.serial_number)
            entry_attrs['issuer'] = unicode(cert.issuer)
            entry_attrs['valid_not_before'] = unicode(cert.valid_not_before_str)
            entry_attrs['valid_not_after'] = unicode(cert.valid_not_after_str)
            entry_attrs['md5_fingerprint'] = unicode(nss.data_to_hex(nss.md5_digest(cert.der_data), 64)[0])
            entry_attrs['sha1_fingerprint'] = unicode(nss.data_to_hex(nss.sha1_digest(cert.der_data), 64)[0])

        return dn

api.register(service_show)

class service_add_host(LDAPAddMember):
    """
    Add hosts that can manage this service.
    """
    member_attributes = ['managedby']
    has_output_params = LDAPAddMember.has_output_params + output_params

api.register(service_add_host)


class service_remove_host(LDAPRemoveMember):
    """
    Remove hosts that can manage this service.
    """
    member_attributes = ['managedby']
    has_output_params = LDAPRemoveMember.has_output_params + output_params

api.register(service_remove_host)


class service_disable(LDAPQuery):
    """
    Disable the Kerberos key of a service.
    """
    has_output = output.standard_value
    msg_summary = _('Removed kerberos key from "%(value)s"')
    has_output_params = LDAPQuery.has_output_params + output_params

    def execute(self, *keys, **options):
        ldap = self.obj.backend

        dn = self.obj.get_dn(*keys, **options)
        (dn, entry_attrs) = ldap.get_entry(dn, ['krblastpwdchange'])

        if 'krblastpwdchange' not in entry_attrs:
            error_msg = _('Service principal has no kerberos key')
            raise errors.NotFound(reason=error_msg)

        ldap.remove_principal_key(dn)

        return dict(
            result=True,
            value=keys[0],
        )

api.register(service_disable)