#!/usr/bin/env python
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# to you under the Apache License, Version 2.0 (the
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#
#     http://www.apache.org/licenses/LICENSE-2.0
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import logging
import subprocess
import sys
import time
from desktop.supervisor import DjangoCommandSupervisee
from desktop.conf import KERBEROS as CONF

LOG = logging.getLogger(__name__)
SPEC = DjangoCommandSupervisee("kt_renewer")

NEED_KRB181_WORKAROUND=None

def renew_from_kt():
  cmdv = [CONF.KINIT_PATH.get(),
          "-k", # host ticket
          "-t", CONF.HUE_KEYTAB.get(), # specify keytab
          "-c", CONF.CCACHE_PATH.get(), # specify credentials cache
          CONF.HUE_PRINCIPAL.get()]
  LOG.info("Reinitting kerberos from keytab: " +
           " ".join(cmdv))
  ret = subprocess.call(cmdv)
  if ret != 0:
    LOG.error("Couldn't reinit from keytab!")
    sys.exit(ret)

  global NEED_KRB181_WORKAROUND
  if NEED_KRB181_WORKAROUND is None:
    NEED_KRB181_WORKAROUND = detect_conf_var()
  if NEED_KRB181_WORKAROUND:
    # HUE-640. Kerberos clock have seconds level granularity. Make sure we
    # renew the ticket after the initial valid time.
    time.sleep(1.5)
    perform_krb181_workaround()

def perform_krb181_workaround():
  cmdv = [CONF.KINIT_PATH.get(),
          "-R",
          "-c", CONF.CCACHE_PATH.get()]
  LOG.info("Renewing kerberos ticket to work around kerberos 1.8.1: " +
           " ".join(cmdv))
  ret = subprocess.call(cmdv)
  if ret != 0:
    fmt_dict = dict(princ=CONF.HUE_PRINCIPAL.get(),
                    ccache=CONF.CCACHE_PATH.get())
    LOG.error("Couldn't renew kerberos ticket in order to work around "
              "Kerberos 1.8.1 issue. Please check that the ticket for "
              "'%(princ)s' is still renewable:\n"
              "  $ kinit -f -c %(ccache)s\n"
              "If the 'renew until' date is the same as the 'valid starting' "
              "date, the ticket cannot be renewed. Please check your KDC "
              "configuration, and the ticket renewal policy (maxrenewlife) "
              "for the '%(princ)s' and `krbtgt' principals." % fmt_dict)
    sys.exit(ret)

def detect_conf_var():
  """Return true if the ticket cache contains "conf" information as is found
  in ticket caches of Kerboers 1.8.1 or later. This is incompatible with the
  Sun Java Krb5LoginModule in Java6, so we need to take an action to work
  around it.
  """
  try:
    f = file(CONF.CCACHE_PATH.get(), "rb")
    data = f.read()
    return "X-CACHECONF:" in data
  finally:
    f.close()

def run():
  if CONF.HUE_KEYTAB.get() is None:
    LOG.debug("Keytab renewer not starting, no keytab configured")
    sys.exit(0)

  while True:
    renew_from_kt()
    time.sleep(CONF.KEYTAB_REINIT_FREQUENCY.get())
