# Authors:
#   Andrew Wnuk <awnuk@redhat.com>
#   Jason Gerard DeRose <jderose@redhat.com>
#   John Dennis <jdennis@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 pyasn1.error import PyAsn1Error
import logging
import traceback
from ipalib.text import _
from ipalib.request import context
from ipalib.output import Output

def get_serial(certificate):
    """
    Given a certificate, return the serial number in that cert
    as a Python long object.

    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:
        certificate = base64.b64decode(certificate)
    except Exception, e:
        pass
    try:

        serial = x509.get_serial_number(certificate, x509.DER)
    except PyAsn1Error:
        raise errors.CertificateOperationError(error=_('Unable to decode certificate in entry'))

    return serial

def get_subject(certificate):
    """
    Given a certificate, return the subject

    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:
        certificate = base64.b64decode(certificate)
    except Exception, e:
        pass
    try:
        sub = list(x509.get_subject_components(certificate, type=x509.DER))
        sub.reverse()
    except PyAsn1Error:
        raise errors.CertificateOperationError(error=_('Unable to decode certificate in entry'))

    subject = ""
    for s in sub:
        subject = subject + "%s=%s," % (s[0], s[1])

    return subject[:-1]

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.CertificateOperationError(error=_('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.CertificateOperationError(error=_('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.CertificateOperationError(error=_('Failure decoding Certificate Signing Request'))
    except Exception, e:
        raise errors.CertificateOperationError(error=_('Failure decoding Certificate Signing Request: %s') % str(e))

def normalize_csr(csr):
    """
    Strip any leading and trailing cruft around the BEGIN/END block
    """
    end_len = 37
    s = csr.find('-----BEGIN NEW CERTIFICATE REQUEST-----')
    if s == -1:
        s = csr.find('-----BEGIN CERTIFICATE REQUEST-----')
    e = csr.find('-----END NEW CERTIFICATE REQUEST-----')
    if e == -1:
        e = csr.find('-----END CERTIFICATE REQUEST-----')
        if e != -1:
            end_len = 33

    if s > -1 and e > -1:
        # We're normalizing here, not validating
        csr = csr[s:e+end_len]

    return csr

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

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

    takes_options = (
        Str('principal',
            label=_('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
        ),
        Str('certificate?',
            label=_('Certificate'),
            flags=['no_create', 'no_update', 'no_search'],
        ),
        Str('subject?',
            label=_('Subject'),
            flags=['no_create', 'no_update', 'no_search'],
        ),
        Str('serial_number?',
            label=_('Serial number'),
            flags=['no_create', 'no_update', 'no_search'],
        ),
    )

    has_output = (
        Output('result',
            type=dict,
            doc=_('Dictionary mapping variable name to value'),
        ),
    )

    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).
        """

        bind_principal = getattr(context, 'principal')
        # Can this user request certs?
        if not bind_principal.startswith('host/'):
            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:
            if not principal.startswith('host/'):
                service = api.Command['service_show'](principal, all=True, raw=True)['result']
                dn = service['dn']
            else:
                realm = principal.find('@')
                if realm == -1:
                    realm = len(principal)
                hostname = principal[5:realm]

                service = api.Command['host_show'](hostname, all=True, raw=True)['result']
                dn = service['dn']
        except errors.NotFound, e:
            if not add:
                raise errors.NotFound(reason="The service principal for this request doesn't exist.")
            try:
                service = api.Command['service_add'](principal, **{})['result']
                dn = service['dn']
            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:
                    hostentry = api.Command['host_show'](name, all=True, raw=True)['result']
                    hostdn = hostentry['dn']
                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)

        if 'usercertificate' in service:
            serial = get_serial(base64.b64encode(service['usercertificate'][0]))
            # revoke the certificate and remove it from the service
            # entry before proceeding. First we retrieve the certificate to
            # see if it is already revoked, if not then we revoke it.
            try:
                result = api.Command['cert_get'](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 get
                pass
            api.Command['service_mod'](principal, usercertificate=None)

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

        # Success? Then add it to the service entry.
        if 'certificate' in result:
            if not principal.startswith('host/'):
                skw = {"usercertificate": str(result.get('certificate'))}
                api.Command['service_mod'](principal, **skw)
            else:
                realm = principal.find('@')
                if realm == -1:
                    realm = len(principal)
                hostname = principal[5:realm]
                skw = {"usercertificate": str(result.get('certificate'))}
                api.Command['host_mod'](hostname, **skw)

        return dict(
            result=result
        )

api.register(cert_request)


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

    takes_args = (
        Str('request_id',
            label=_('Request id'),
            flags=['no_create', 'no_update', 'no_search'],
        ),
    )
    takes_options = (
        Str('cert_request_status?',
            label=_('Request status'),
            flags=['no_create', 'no_update', 'no_search'],
        ),
    )
    operation = "certificate status"


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

api.register(cert_status)


_serial_number = Str('serial_number',
    label=_('Serial number'),
    doc=_('Serial number in decimal or if prefixed with 0x in hexadecimal'),
)

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

    takes_args = _serial_number

    takes_options = (
        Str('certificate?',
            label=_('Certificate'),
            flags=['no_create', 'no_update', 'no_search'],
        ),
        Str('subject?',
            label=_('Subject'),
            flags=['no_create', 'no_update', 'no_search'],
        ),
        Str('revocation_reason?',
            label=_('Revocation reason'),
            flags=['no_create', 'no_update', 'no_search'],
        ),
    )

    operation="retrieve certificate"

    def execute(self, serial_number):
        self.check_access()
        result=self.Backend.ra.get_certificate(serial_number)
        result['subject'] = get_subject(result['certificate'])
        return dict(result=result)

api.register(cert_get)


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

    takes_args = _serial_number

    takes_options = (
        Flag('revoked?',
            label=_('Revoked'),
            flags=['no_create', 'no_update', 'no_search'],
        ),
    )
    operation = "revoke certificate"

    # FIXME: The default is 0.  Is this really an Int param?
    takes_options = (
        Int('revocation_reason?',
            label=_('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 dict(
            result=self.Backend.ra.revoke_certificate(serial_number, **kw)
        )

api.register(cert_revoke)


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

    takes_args = _serial_number

    takes_options = (
        Flag('unrevoked?',
            label=_('Unrevoked'),
            flags=['no_create', 'no_update', 'no_search'],
        ),
        Str('error_string?',
            label=_('Error'),
            flags=['no_create', 'no_update', 'no_search'],
        ),
    )
    operation = "certificate remove hold"

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

api.register(cert_remove_hold)