# Authors:
#   Andrew Wnuk <awnuk@redhat.com>
#   Jason Gerard DeRose <jderose@redhat.com>
#
# Copyright (C) 2009  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

"""
Command plugins for IPA-RA certificate operations.
"""

from ipalib import api, SkipPluginModule
if api.env.enable_ra is not True:
    # In this case, abort loading this plugin module...
    raise SkipPluginModule(reason='env.enable_ra is not True')
from ipalib import Command, Str, Int, Bytes, Flag, File
from ipalib import errors
from ipalib import pkcs10
from ipalib import x509
from ipalib.plugins.virtual import *
from ipalib.plugins.service import split_principal
import base64
from ipalib.request import context
from ipapython import dnsclient
from pyasn1.error import PyAsn1Error
import logging
import traceback

def get_serial(certificate):
    """
    Given a certificate, return the serial number in that cert

    In theory there should be only one cert per object so even if we get
    passed in a list/tuple only return the first one.
    """
    if type(certificate) in (list, tuple):
        certificate = certificate[0]
    try:
        serial = str(x509.get_serial_number(certificate))
    except PyAsn1Error:
        raise errors.GenericError(format='Unable to decode certificate in entry')

    return serial

def get_csr_hostname(csr):
    """
    Return the value of CN in the subject of the request
    """
    try:
        request = pkcs10.load_certificate_request(csr)
        sub = request.get_subject().get_components()
        for s in sub:
            if s[0].lower() == "cn":
                return s[1]
    except PyAsn1Error:
        # The ASN.1 decoding errors tend to be long and involved and the
        # last bit is generally not interesting. We need the whole traceback.
        logging.error('Unable to decode CSR\n%s', traceback.format_exc())
        raise errors.GenericError(format='Failure decoding Certificate Signing Request')

    return None

def get_subjectaltname(csr):
    """
    Return the value of the subject alt name, if any
    """
    try:
        request = pkcs10.load_certificate_request(csr)
    except PyAsn1Error:
        # The ASN.1 decoding errors tend to be long and involved and the
        # last bit is generally not interesting. We need the whole traceback.
        logging.error('Unable to decode CSR\n%s', traceback.format_exc())
        raise errors.GenericError(format='Failure decoding Certificate Signing Request')
    return request.get_subjectaltname()

def validate_csr(ugettext, csr):
    """
    Ensure the CSR is base64-encoded and can be decoded by our PKCS#10
    parser.
    """
    try:
        request = pkcs10.load_certificate_request(csr)

        # Explicitly request the attributes. This fires off additional
        # decoding to get things like the subjectAltName.
        attrs = request.get_attributes()
    except TypeError, e:
        raise errors.Base64DecodeError(reason=str(e))
    except PyAsn1Error:
        raise errors.GenericError(format='Failure decoding Certificate Signing Request')
    except Exception, e:
        raise errors.GenericError(format='Failure decoding Certificate Signing Request: %s' % str(e))


class cert_request(VirtualCommand):
    """
    Submit a certificate signing request.
    """

    takes_args = (
        File('csr', validate_csr,
            cli_name='csr_file',
        ),
    )
    operation="request certificate"

    takes_options = (
        Str('principal',
            doc="service principal for this certificate (e.g. HTTP/test.example.com)",
        ),
        Str('request_type',
            default=u'pkcs10',
            autofill=True,
        ),
        Flag('add',
            doc="automatically add the principal if it doesn't exist",
            default=False,
            autofill=True
        ),
    )

    def execute(self, csr, **kw):
        ldap = self.api.Backend.ldap2
        principal = kw.get('principal')
        add = kw.get('add')
        del kw['principal']
        del kw['add']
        service = None

        """
        Access control is partially handled by the ACI titled
        'Hosts can modify service userCertificate'. This is for the case
        where a machine binds using a host/ prinicpal. It can only do the
        request if the target hostname is in the managedBy attribute which
        is managed using the add/del member commands.

        Binding with a user principal one needs to be in the request_certs
        taskgroup (directly or indirectly via role membership).
        """

        # Can this user request certs?
        self.check_access()

        # FIXME: add support for subject alt name

        # Ensure that the hostname in the CSR matches the principal
        subject_host = get_csr_hostname(csr)
        (servicename, hostname, realm) = split_principal(principal)
        if subject_host.lower() != hostname.lower():
            raise errors.ACIError(info="hostname in subject of request '%s' does not match principal hostname '%s'" % (subject_host, hostname))

        dn = None
        service = None
        # See if the service exists and punt if it doesn't and we aren't
        # going to add it
        try:
            (dn, service) = api.Command['service_show'](principal, all=True, raw=True)
            if 'usercertificate' in service:
                # FIXME, what to do here? Do we revoke the old cert?
                raise errors.GenericError(format='entry already has a certificate, serial number %s' % get_serial(base64.b64encode(service['usercertificate'][0])))
        except errors.NotFound, e:
            if not add:
                raise errors.NotFound(reason="The service principal for this request doesn't exist.")
            try:
                (dn, service) = api.Command['service_add'](principal, **{})
            except errors.ACIError:
                raise errors.ACIError(info='You need to be a member of the serviceadmin role to add services')

        # We got this far so the service entry exists, can we write it?
        if not ldap.can_write(dn, "usercertificate"):
            raise errors.ACIError(info="Insufficient 'write' privilege to the 'userCertificate' attribute of entry '%s'." % dn)

        # Validate the subject alt name, if any
        subjectaltname = get_subjectaltname(csr)
        if subjectaltname is not None:
            for name in subjectaltname:
                try:
                    (hostdn, hostentry) = api.Command['host_show'](name, all=True, raw=True)
                except errors.NotFound:
                    # We don't want to issue any certificates referencing
                    # machines we don't know about. Nothing is stored in this
                    # host record related to this certificate.
                    raise errors.NotFound(reason='no host record for subject alt name %s in certificate request' % name)
                authprincipal = getattr(context, 'principal')
                if authprincipal.startswith("host/"):
                    if not hostdn in service.get('managedby', []):
                        raise errors.ACIError(info="Insufficient privilege to create a certificate with subject alt name '%s'." % name)

        # Request the certificate
        result = self.Backend.ra.request_certificate(csr, **kw)

        # Success? Then add it to the service entry.
        if result.get('status') == 0:
            skw = {"usercertificate": str(result.get('certificate'))}
            api.Command['service_mod'](principal, **skw)

        return result

    def output_for_cli(self, textui, result, *args, **kw):
        if isinstance(result, dict) and len(result) > 0:
            textui.print_entry(result, 0)
        else:
            textui.print_plain('Failed to submit a certificate request.')

api.register(cert_request)


class cert_status(VirtualCommand):
    """
    Check status of a certificate signing request.
    """

    takes_args = ('request_id')
    operation = "certificate status"


    def execute(self, request_id, **kw):
        self.check_access()
        return self.Backend.ra.check_request_status(request_id)

    def output_for_cli(self, textui, result, *args, **kw):
        if isinstance(result, dict) and len(result) > 0:
            textui.print_entry(result, 0)
        else:
            textui.print_plain('Failed to retrieve a request status.')

api.register(cert_status)


class cert_get(VirtualCommand):
    """
    Retrieve an existing certificate.
    """

    takes_args = ('serial_number')
    operation="retrieve certificate"

    def execute(self, serial_number):
        self.check_access()
        return self.Backend.ra.get_certificate(serial_number)

    def output_for_cli(self, textui, result, *args, **kw):
        if isinstance(result, dict) and len(result) > 0:
            textui.print_entry(result, 0)
        else:
            textui.print_plain('Failed to obtain a certificate.')

api.register(cert_get)


class cert_revoke(VirtualCommand):
    """
    Revoke a certificate.
    """

    takes_args = ('serial_number')
    operation = "revoke certificate"

    # FIXME: The default is 0.  Is this really an Int param?
    takes_options = (
        Int('revocation_reason?',
            doc='Reason for revoking the certificate (0-10)',
            minvalue=0,
            maxvalue=10,
            default=0,
        ),
    )


    def execute(self, serial_number, **kw):
        self.check_access()
        return self.Backend.ra.revoke_certificate(serial_number, **kw)

    def output_for_cli(self, textui, result, *args, **kw):
        if isinstance(result, dict) and len(result) > 0:
            textui.print_entry(result, 0)
        else:
            textui.print_plain('Failed to revoke a certificate.')

api.register(cert_revoke)


class cert_remove_hold(VirtualCommand):
    """
    Take a revoked certificate off hold.
    """

    takes_args = ('serial_number')
    operation = "certificate remove hold"

    def execute(self, serial_number, **kw):
        self.check_access()
        return self.Backend.ra.take_certificate_off_hold(serial_number)

    def output_for_cli(self, textui, result, *args, **kw):
        if isinstance(result, dict) and len(result) > 0:
            textui.print_entry(result, 0)
        else:
            textui.print_plain('Failed to take a revoked certificate off hold.')

api.register(cert_remove_hold)