#!/usr/bin/python2 -E
#
# Authors:
#   Jan Cholasta <jcholast@redhat.com>
#
# Copyright (C) 2013  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/>.

from __future__ import print_function

import os
# Prevent garbage from readline on standard output
# (see https://fedorahosted.org/freeipa/ticket/4064)
if not os.isatty(1):
    os.environ['TERM'] = 'dumb'
import sys
import syslog
import traceback
import tempfile
import shutil
import base64
import contextlib
import json

import six

from ipapython import ipautil
from ipapython.dn import DN
from ipalib import api, errors, x509
from ipaplatform.paths import paths
from ipaserver.plugins.ldap2 import ldap2
from ipaserver.install import cainstance, dsinstance, certs

# This is a certmonger CA helper script for IPA CA subsystem cert renewal. See
# https://git.fedorahosted.org/cgit/certmonger.git/tree/doc/submit.txt for more
# info on certmonger CA helper scripts.

# Return codes. Names of the constants are taken from
# https://git.fedorahosted.org/cgit/certmonger.git/tree/src/submit-e.h
ISSUED = 0
WAIT = 1
REJECTED = 2
UNREACHABLE = 3
UNCONFIGURED = 4
WAIT_WITH_DELAY = 5
OPERATION_NOT_SUPPORTED_BY_HELPER = 6

if six.PY3:
    unicode = str


IPA_CA_NICKNAME = 'caSigningCert cert-pki-ca'

def get_nickname():
    subject = os.environ.get('CERTMONGER_REQ_SUBJECT')
    if not subject:
        return None

    subject_base = dsinstance.DsInstance().find_subject_base()
    if not subject_base:
        return None

    nickname_by_subject_dn = {
        DN('CN=Certificate Authority', subject_base):
            'caSigningCert cert-pki-ca',
        DN('CN=CA Audit', subject_base): 'auditSigningCert cert-pki-ca',
        DN('CN=OCSP Subsystem', subject_base): 'ocspSigningCert cert-pki-ca',
        DN('CN=CA Subsystem', subject_base): 'subsystemCert cert-pki-ca',
        DN('CN=KRA Audit', subject_base): 'auditSigningCert cert-pki-kra',
        DN('CN=KRA Transport Certificate', subject_base):
            'transportCert cert-pki-kra',
        DN('CN=KRA Storage Certificate', subject_base):
            'storageCert cert-pki-kra',
        DN('CN=IPA RA', subject_base): 'ipaCert',
    }

    try:
        return nickname_by_subject_dn[DN(subject)]
    except KeyError:
        cas = api.Command.ca_find(ipacasubjectdn=DN(subject))['result']
        if len(cas) == 0:
            return None
        return 'caSigningCert cert-pki-ca {}'.format(cas[0]['ipacaid'][0])


def is_lightweight_ca():
    nickname = get_nickname() or ''
    return nickname != IPA_CA_NICKNAME and nickname.startswith(IPA_CA_NICKNAME)

def is_renewable():
    cert = os.environ.get('CERTMONGER_CERTIFICATE')
    if not cert:
        return False
    else:
        return x509.is_self_signed(cert) or is_lightweight_ca()


@contextlib.contextmanager
def ldap_connect():
    conn = None
    try:
        conn = ldap2(api)
        conn.connect(autobind=True)
        yield conn
    finally:
        if conn is not None and conn.isconnected():
            conn.disconnect()

def call_handler(_handler, *args, **kwargs):
    """
    Request handler call wrapper

    Before calling the handler, get the original profile name and cookie from
    the provided cookie, if there is one. If the profile name does not match
    the requested profile name, drop the cookie and restart the request.

    After calling the handler, put the requested profile name and cookie
    returned by the handler in a new cookie and return it.
    """
    operation = os.environ['CERTMONGER_OPERATION']
    if operation == 'POLL':
        cookie = os.environ.pop('CERTMONGER_CA_COOKIE', None)
        if cookie is not None:
            try:
                context = json.loads(cookie)
                if not isinstance(context, dict):
                    raise TypeError
            except (TypeError, ValueError):
                return (UNCONFIGURED, "Invalid cookie: %r" % cookie)
        else:
            return (UNCONFIGURED, "Cookie not provided")

        if 'profile' in context:
            profile = context.pop('profile')
            try:
                if profile is not None:
                    if not isinstance(profile, unicode):
                        raise TypeError
                    profile = profile.encode('raw_unicode_escape')
            except (TypeError, UnicodeEncodeError):
                return (UNCONFIGURED,
                        "Invalid 'profile' in cookie: %r" % profile)
        else:
            return (UNCONFIGURED, "No 'profile' in cookie")

        # If profile has changed between SUBMIT and POLL, restart request
        if os.environ.get('CERTMONGER_CA_PROFILE') != profile:
            os.environ['CERTMONGER_OPERATION'] = 'SUBMIT'
            context = {}

        if 'cookie' in context:
            cookie = context.pop('cookie')
            try:
                if not isinstance(cookie, unicode):
                    raise TypeError
                cookie = cookie.encode('raw_unicode_escape')
            except (TypeError, UnicodeEncodeError):
                return (UNCONFIGURED,
                        "Invalid 'cookie' in cookie: %r" % cookie)
            os.environ['CERTMONGER_CA_COOKIE'] = cookie
    else:
        context = {}

    result = _handler(*args, **kwargs)

    if result[0] in (WAIT, WAIT_WITH_DELAY):
        context['cookie'] = result[-1].decode('raw_unicode_escape')

    profile = os.environ.get('CERTMONGER_CA_PROFILE')
    if profile is not None:
        profile = profile.decode('raw_unicode_escape')
    context['profile'] = profile

    cookie = json.dumps(context)
    os.environ['CERTMONGER_CA_COOKIE'] = cookie
    if result[0] in (WAIT, WAIT_WITH_DELAY):
        result = result[:-1] + (cookie,)

    return result

def request_cert():
    """
    Request certificate from IPA CA.
    """
    syslog.syslog(syslog.LOG_NOTICE,
                  "Forwarding request to dogtag-ipa-renew-agent")

    path = paths.DOGTAG_IPA_RENEW_AGENT_SUBMIT
    args = [path] + sys.argv[1:] + ['--submit-option', "requestor_name=IPA"]
    if os.environ.get('CERTMONGER_CA_PROFILE') == 'caCACert':
        args += ['-N', '-O', 'bypassCAnotafter=true']
    result = ipautil.run(args, raiseonerr=False, env=os.environ,
                        capture_output=True)
    if six.PY2:
        sys.stderr.write(result.raw_error_output)
    else:
        # Write bytes directly
        sys.stderr.buffer.write(result.raw_error_output)  #pylint: disable=no-member
    sys.stderr.flush()

    syslog.syslog(syslog.LOG_NOTICE,
                  "dogtag-ipa-renew-agent returned %d" % result.returncode)

    stdout = result.output
    if stdout.endswith('\n'):
        stdout = stdout[:-1]

    rc = result.returncode
    if rc == WAIT_WITH_DELAY:
        delay, _sep, cookie = stdout.partition('\n')
        return (rc, delay, cookie)
    else:
        return (rc, stdout)

def store_cert():
    """
    Store certificate in LDAP.
    """
    operation = os.environ.get('CERTMONGER_OPERATION')
    if operation == 'SUBMIT':
        attempts = 0
    elif operation == 'POLL':
        cookie = os.environ.get('CERTMONGER_CA_COOKIE')
        if not cookie:
            return (UNCONFIGURED, "Cookie not provided")

        try:
            attempts = int(cookie)
        except ValueError:
            return (UNCONFIGURED, "Invalid cookie: %r" % cookie)
    else:
        return (OPERATION_NOT_SUPPORTED_BY_HELPER,)

    nickname = get_nickname()
    if not nickname:
        return (REJECTED, "Nickname could not be determined")

    cert = os.environ.get('CERTMONGER_CERTIFICATE')
    if not cert:
        return (REJECTED, "New certificate requests not supported")

    if is_lightweight_ca():
        # Lightweight CAs are updated in Dogtag's NSSDB
        # by Dogtag itself, so do not store it
        return (ISSUED, cert)

    dercert = x509.normalize_certificate(cert)

    dn = DN(('cn', nickname), ('cn', 'ca_renewal'),
            ('cn', 'ipa'), ('cn', 'etc'), api.env.basedn)
    try:
        with ldap_connect() as conn:
            try:
                entry = conn.get_entry(dn, ['usercertificate'])
                entry['usercertificate'] = [dercert]
                conn.update_entry(entry)
            except errors.NotFound:
                entry = conn.make_entry(
                    dn,
                    objectclass=['top', 'pkiuser', 'nscontainer'],
                    cn=[nickname],
                    usercertificate=[dercert])
                conn.add_entry(entry)
            except errors.EmptyModlist:
                pass
    except Exception as e:
        attempts += 1
        if attempts < 10:
            syslog.syslog(
                syslog.LOG_ERR,
                "Updating renewal certificate failed: %s. Sleeping 30s" % e)
            return (WAIT_WITH_DELAY, 30, str(attempts))
        else:
            syslog.syslog(
                syslog.LOG_ERR,
                "Giving up. To retry storing the certificate, resubmit the "
                "request with profile \"ipaStorage\"")

    return (ISSUED, cert)

def request_and_store_cert():
    """
    Request certificate from IPA CA and store it in LDAP.
    """
    operation = os.environ.get('CERTMONGER_OPERATION')
    if operation == 'SUBMIT':
        state = 'request'
        cookie = None
    elif operation == 'POLL':
        cookie = os.environ.get('CERTMONGER_CA_COOKIE')
        if not cookie:
            return (UNCONFIGURED, "Cookie not provided")

        state, _sep, cookie = cookie.partition(':')
        if state not in ('request', 'store'):
            return (UNCONFIGURED,
                    "Invalid cookie: %r" % os.environ['CERTMONGER_CA_COOKIE'])
    else:
        return (OPERATION_NOT_SUPPORTED_BY_HELPER,)

    if state == 'request':
        if cookie is None:
            os.environ['CERTMONGER_OPERATION'] = 'SUBMIT'
        else:
            os.environ['CERTMONGER_CA_COOKIE'] = cookie

        result = call_handler(request_cert)
        if result[0] == WAIT:
            return (result[0], 'request:%s' % result[1])
        elif result[0] == WAIT_WITH_DELAY:
            return (result[0], result[1], 'request:%s' % result[2])
        elif result[0] != ISSUED:
            return result
        else:
            cert = result[1]
            cookie = None
    else:
        cert, _sep, cookie = cookie.partition(':')

    if cookie is None:
        os.environ['CERTMONGER_OPERATION'] = 'SUBMIT'
    else:
        os.environ['CERTMONGER_CA_COOKIE'] = cookie
    os.environ['CERTMONGER_CERTIFICATE'] = cert

    result = call_handler(store_cert)
    if result[0] == WAIT:
        return (result[0], 'store:%s:%s' % (cert, result[1]))
    elif result[0] == WAIT_WITH_DELAY:
        return (result[0], result[1], 'store:%s:%s' % (cert, result[2]))
    else:
        return result

def retrieve_or_reuse_cert():
    """
    Retrieve certificate from LDAP. If the certificate is not available, reuse
    the old certificate.
    """
    nickname = get_nickname()
    if not nickname:
        return (REJECTED, "Nickname could not be determined")

    cert = os.environ.get('CERTMONGER_CERTIFICATE')
    if not cert:
        return (REJECTED, "New certificate requests not supported")

    with ldap_connect() as conn:
        try:
            entry = conn.get_entry(
                DN(('cn', nickname), ('cn', 'ca_renewal'),
                   ('cn', 'ipa'), ('cn', 'etc'), api.env.basedn),
                ['usercertificate'])
        except errors.NotFound:
            pass
        else:
            cert = entry.single_value['usercertificate']
            cert = base64.b64encode(cert)
            cert = x509.make_pem(cert)

    return (ISSUED, cert)

def retrieve_cert_continuous():
    """
    Retrieve new certificate from LDAP. Repeat every eight hours until the
    certificate is available.
    """
    old_cert = os.environ.get('CERTMONGER_CERTIFICATE')
    if old_cert:
        old_cert = x509.normalize_certificate(old_cert)

    if is_lightweight_ca():
        # Lightweight CAs are updated in Dogtag's NSSDB
        # by Dogtag itself, so do not try to retrieve it.
        # Everything is fine as is.
        return (ISSUED, os.environ.get('CERTMONGER_CERTIFICATE'))

    result = call_handler(retrieve_or_reuse_cert)
    if result[0] != ISSUED:
        return result

    new_cert = x509.normalize_certificate(result[1])
    if new_cert == old_cert:
        syslog.syslog(syslog.LOG_INFO, "Updated certificate not available")
        # No cert available yet, tell certmonger to wait another 8 hours
        return (WAIT_WITH_DELAY, 8 * 60 * 60, '')

    return result

def retrieve_cert():
    """
    Retrieve new certificate from LDAP.
    """
    result = call_handler(retrieve_cert_continuous)
    if result[0] == WAIT_WITH_DELAY:
        return (REJECTED, "Updated certificate not available")

    return result

def export_csr():
    """
    This does not actually renew the cert, it just writes the CSR provided
    by certmonger to /var/lib/ipa/ca.csr and returns the existing cert.
    """
    operation = os.environ.get('CERTMONGER_OPERATION')
    if operation != 'SUBMIT':
        return (OPERATION_NOT_SUPPORTED_BY_HELPER,)

    csr = os.environ.get('CERTMONGER_CSR')
    if not csr:
        return (UNCONFIGURED, "Certificate request not provided")

    cert = os.environ.get('CERTMONGER_CERTIFICATE')
    if not cert:
        return (REJECTED, "New certificate requests not supported")

    csr_file = paths.IPA_CA_CSR
    try:
        with open(csr_file, 'wb') as f:
            f.write(csr)
    except Exception as e:
        return (UNREACHABLE, "Failed to write %s: %s" % (csr_file, e))

    return (ISSUED, cert)

def renew_ca_cert():
    """
    This is used for automatic CA certificate renewal.
    """
    cert = os.environ.get('CERTMONGER_CERTIFICATE')
    if not cert:
        return (REJECTED, "New certificate requests not supported")

    operation = os.environ.get('CERTMONGER_OPERATION')
    if operation == 'SUBMIT':
        state = 'retrieve'

        if is_renewable():
            ca = cainstance.CAInstance(host_name=api.env.host)
            if ca.is_renewal_master():
                state = 'request'
    elif operation == 'POLL':
        cookie = os.environ.get('CERTMONGER_CA_COOKIE')
        if not cookie:
            return (UNCONFIGURED, "Cookie not provided")

        state, _sep, cookie = cookie.partition(':')
        if state not in ('retrieve', 'request'):
            return (UNCONFIGURED,
                    "Invalid cookie: %r" % os.environ['CERTMONGER_CA_COOKIE'])

        os.environ['CERTMONGER_CA_COOKIE'] = cookie
    else:
        return (OPERATION_NOT_SUPPORTED_BY_HELPER,)

    if state == 'retrieve':
        result = call_handler(retrieve_cert)
        if result[0] == REJECTED and not is_renewable():
            syslog.syslog(syslog.LOG_ALERT,
                          "Certificate with subject '%s' is about to expire, "
                          "use ipa-cacert-manage to renew it"
                          % (os.environ.get("CERTMONGER_REQ_SUBJECT"),))
    elif state == 'request':
        profile = os.environ['CERTMONGER_CA_PROFILE']
        os.environ['CERTMONGER_CA_PROFILE'] = 'caCACert'
        result = call_handler(request_and_store_cert)
        os.environ['CERTMONGER_CA_PROFILE'] = profile

    if result[0] == WAIT:
        return (result[0], '%s:%s' % (state, result[1]))
    elif result[0] == WAIT_WITH_DELAY:
        return (result[0], result[1], '%s:%s' % (state, result[2]))
    else:
        return result

def main():
    handlers = {
        'ipaStorage':           store_cert,
        'ipaRetrievalOrReuse':  retrieve_or_reuse_cert,
        'ipaRetrieval':         retrieve_cert,
        'ipaCSRExport':         export_csr,
        'ipaCACertRenewal':     renew_ca_cert,
    }

    api.bootstrap(in_server=True, context='renew')
    api.finalize()
    api.Backend.ldap2.connect()

    operation = os.environ.get('CERTMONGER_OPERATION')
    if operation not in ('SUBMIT', 'POLL'):
        return OPERATION_NOT_SUPPORTED_BY_HELPER

    tmpdir = tempfile.mkdtemp(prefix="tmp-")
    certs.renewal_lock.acquire()
    try:
        profile = os.environ.get('CERTMONGER_CA_PROFILE')
        if profile:
            handler = handlers.get(profile, request_and_store_cert)
        else:
            ca = cainstance.CAInstance(host_name=api.env.host)
            if ca.is_renewal_master():
                handler = request_and_store_cert
            else:
                handler = retrieve_cert_continuous

        res = call_handler(handler)
        for item in res[1:]:
            print(item)
        return res[0]
    finally:
        certs.renewal_lock.release()
        shutil.rmtree(tmpdir)
        api.Backend.ldap2.disconnect()


try:
    sys.exit(main())
except Exception as e:
    syslog.syslog(syslog.LOG_ERR, traceback.format_exc())
    print("Internal error")
    sys.exit(UNREACHABLE)