trust-fetch-domains: make sure we use right KDC when --server is specified

Since we are authenticating against AD DC before talking to it (by using
trusted domain object's credentials), we need to override krb5.conf
configuration in case --server option is specified.

The context is a helper which is launched out of process with the help
of oddjobd. The helper takes existing trusted domain object, uses its
credentials to authenticate and then runs LSA RPC calls against that
trusted domain's domain controller. Previous code directed Samba
bindings to use the correct domain controller. However, if a DC visible
to MIT Kerberos is not reachable, we would not be able to obtain TGT and
the whole process will fail.

trust_add.execute() was calling out to the D-Bus helper without passing
the options (e.g. --server) so there was no chance to get that option
visible by the oddjob helper.

Also we need to make errors in the oddjob helper more visible to
error_log. Thus, move error reporting for a normal communication up from
the exception catching.

Resolves: https://pagure.io/freeipa/issue/7895
Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>
Reviewed-By: Sergey Orlov <sorlov@redhat.com>
This commit is contained in:
Alexander Bokovoy 2019-06-27 15:17:07 +03:00 committed by Florence Blanc-Renaud
parent 37ab150cc7
commit 6c9fcccfbc
2 changed files with 193 additions and 66 deletions

View File

@ -8,9 +8,12 @@ from ipapython.dn import DN
from ipapython.dnsutil import DNSName
from ipaplatform.constants import constants
from ipaplatform.paths import paths
import io
import sys
import os
import pwd
import tempfile
import textwrap
import six
import gssapi
@ -23,17 +26,38 @@ if six.PY3:
def parse_options():
usage = "%prog <trusted domain name>\n"
parser = config.IPAOptionParser(usage=usage,
formatter=config.IPAFormatter())
parser = config.IPAOptionParser(
usage=usage, formatter=config.IPAFormatter()
)
parser.add_option("-d", "--debug", action="store_true", dest="debug",
help="Display debugging information")
parser.add_option("-s", "--server", action="store", dest="server",
help="Domain controller for the Active Directory domain (optional)")
parser.add_option("-a", "--admin", action="store", dest="admin",
help="Active Directory administrator (optional)")
parser.add_option("-p", "--password", action="store", dest="password",
help="Display debugging information")
parser.add_option(
"-d",
"--debug",
action="store_true",
dest="debug",
help="Display debugging information",
)
parser.add_option(
"-s",
"--server",
action="store",
dest="server",
help="Domain controller for the Active Directory domain (optional)",
)
parser.add_option(
"-a",
"--admin",
action="store",
dest="admin",
help="Active Directory administrator (optional)",
)
parser.add_option(
"-p",
"--password",
action="store",
dest="password",
help="Display debugging information",
)
options, args = parser.parse_args()
safe_options = parser.get_safe_opts(options)
@ -50,17 +74,26 @@ def parse_options():
raise ScriptError("You must specify a valid trusted domain name", 2)
return safe_options, options, trusted_domain
def retrieve_keytab(api, ccache_name, oneway_keytab_name, oneway_principal):
getkeytab_args = ["/usr/sbin/ipa-getkeytab",
"-s", api.env.host,
"-p", oneway_principal,
"-k", oneway_keytab_name,
"-r"]
getkeytab_args = [
"/usr/sbin/ipa-getkeytab",
"-s",
api.env.host,
"-p",
oneway_principal,
"-k",
oneway_keytab_name,
"-r",
]
if os.path.isfile(oneway_keytab_name):
os.unlink(oneway_keytab_name)
ipautil.run(getkeytab_args, env={'KRB5CCNAME': ccache_name, 'LANG': 'C'},
raiseonerr=False)
ipautil.run(
getkeytab_args,
env={"KRB5CCNAME": ccache_name, "LANG": "C"},
raiseonerr=False,
)
# Make sure SSSD is able to read the keytab
try:
sssd = pwd.getpwnam(constants.SSSD_USER)
@ -72,8 +105,7 @@ def retrieve_keytab(api, ccache_name, oneway_keytab_name, oneway_principal):
def get_forest_root_domain(api_instance, trusted_domain, server=None):
"""
retrieve trusted forest root domain for given domain name
"""Retrieve trusted forest root domain for given domain name
:param api_instance: IPA API instance
:param trusted_domain: trusted domain name
@ -81,18 +113,51 @@ def get_forest_root_domain(api_instance, trusted_domain, server=None):
:returns: forest root domain DNS name
"""
trustconfig_show = api_instance.Command.trustconfig_show
flatname = trustconfig_show()['result']['ipantflatname'][0]
flatname = trustconfig_show()["result"]["ipantflatname"][0]
remote_domain = dcerpc.retrieve_remote_domain(
api_instance.env.host, flatname, trusted_domain,
realm_server=server)
api_instance.env.host, flatname, trusted_domain, realm_server=server
)
return remote_domain.info["dns_forest"]
def generate_krb5_config(realm, server):
"""Generate override krb5 config file for trusted domain DC access
:param realm: realm of the trusted AD domain
:param server: server to override KDC to
:returns: tuple (temporary config file name, KRB5_CONFIG string)
"""
cfg = paths.KRB5_CONF
tcfg = None
if server:
content = textwrap.dedent(u"""
[realms]
%s = {
kdc = %s
}
""") % (
realm.upper(),
server,
)
(fd, tcfg) = tempfile.mkstemp(dir="/var/run/ipa",
prefix="krb5conf", text=True)
with io.open(fd, mode='w', encoding='utf-8') as o:
o.write(content)
cfg = ":".join([tcfg, cfg])
return (tcfg, cfg)
return remote_domain.info['dns_forest']
if not is_ipa_configured():
# LSB status code 6: program is not configured
raise ScriptError("IPA is not configured " +
"(see man pages of ipa-server-install for help)", 6)
raise ScriptError(
"IPA is not configured "
+ "(see man pages of ipa-server-install for help)",
6,
)
if not os.getegid() == 0:
# LSB status code 4: user had insufficient privilege
@ -100,8 +165,9 @@ if not os.getegid() == 0:
safe_options, options, trusted_domain = parse_options()
api.bootstrap(in_server=True, log=None,
context='server', confdir=paths.ETC_IPA)
api.bootstrap(
in_server=True, log=None, context="server", confdir=paths.ETC_IPA
)
api.finalize()
# Only import trust plugin after api is initialized or internal imports
@ -121,12 +187,12 @@ from ipaserver.plugins import trust
# and retrieve our own NetBIOS domain name and use cifs/ipa.master@IPA.REALM to
# retrieve the keys to oneway_keytab_name.
keytab_name = '/etc/samba/samba.keytab'
keytab_name = "/etc/samba/samba.keytab"
principal = str('cifs/' + api.env.host)
principal = str("cifs/" + api.env.host)
oneway_ccache_name = '/var/run/ipa/krb5cc_oddjob_trusts_fetch'
ccache_name = '/var/run/ipa/krb5cc_oddjob_trusts'
oneway_ccache_name = "/var/run/ipa/krb5cc_oddjob_trusts_fetch"
ccache_name = "/var/run/ipa/krb5cc_oddjob_trusts"
# Standard sequence:
# - check if ccache exists
@ -140,33 +206,45 @@ try:
cred = kinit_keytab(principal, keytab_name, ccache_name)
if cred.lifetime > 0:
have_ccache = True
except gssapi.exceptions.ExpiredCredentialsError:
except (gssapi.exceptions.ExpiredCredentialsError, gssapi.raw.misc.GSSError):
pass
if not have_ccache:
# delete stale ccache and try again
if os.path.exists(oneway_ccache_name):
if os.path.exists(ccache_name):
os.unlink(ccache_name)
cred = kinit_keytab(principal, keytab_name, ccache_name)
old_ccache = os.environ.get('KRB5CCNAME')
old_ccache = os.environ.get("KRB5CCNAME")
old_config = os.environ.get("KRB5_CONFIG")
api.Backend.ldap2.connect(ccache_name)
# Retrieve own NetBIOS name and trusted forest's name.
# We use script's input to retrieve the trusted forest's name to sanitize input
# for file-level access as we might need to wipe out keytab in /var/lib/sss/keytabs
own_trust_dn = DN(('cn', api.env.domain),('cn','ad'), ('cn', 'etc'), api.env.basedn)
own_trust_entry = api.Backend.ldap2.get_entry(own_trust_dn, ['ipantflatname'])
own_trust_flatname = own_trust_entry.single_value.get('ipantflatname').upper()
trusted_domain_dn = DN(('cn', trusted_domain.lower()), api.env.container_adtrusts, api.env.basedn)
trusted_domain_entry = api.Backend.ldap2.get_entry(trusted_domain_dn, ['cn'])
trusted_domain = trusted_domain_entry.single_value.get('cn').lower()
own_trust_dn = DN(
("cn", api.env.domain), ("cn", "ad"), ("cn", "etc"), api.env.basedn
)
own_trust_entry = api.Backend.ldap2.get_entry(own_trust_dn, ["ipantflatname"])
own_trust_flatname = own_trust_entry.single_value.get("ipantflatname").upper()
trusted_domain_dn = DN(
("cn", trusted_domain.lower()), api.env.container_adtrusts, api.env.basedn
)
trusted_domain_entry = api.Backend.ldap2.get_entry(trusted_domain_dn, ["cn"])
trusted_domain = trusted_domain_entry.single_value.get("cn").lower()
# At this point if we didn't find trusted forest name, an exception will be raised
# and script will quit. This is actually intended.
# Generate MIT Kerberos configuration file that potentially overlays
# the KDC to connect to for a trusted domain to allow --server option
# to take precedence.
cfg_file, cfg = generate_krb5_config(trusted_domain, options.server)
if not (options.admin and options.password):
oneway_keytab_name = '/var/lib/sss/keytabs/' + trusted_domain + '.keytab'
oneway_principal = str('%s$@%s' % (own_trust_flatname, trusted_domain.upper()))
oneway_keytab_name = "/var/lib/sss/keytabs/" + trusted_domain + ".keytab"
oneway_principal = str(
"%s$@%s" % (own_trust_flatname, trusted_domain.upper())
)
# If keytab does not exist, retrieve it
if not os.path.isfile(oneway_keytab_name):
@ -176,39 +254,78 @@ if not (options.admin and options.password):
have_ccache = False
try:
# The keytab may have stale key material (from older trust-add run)
cred = kinit_keytab(oneway_principal, oneway_keytab_name, oneway_ccache_name)
cred = kinit_keytab(
oneway_principal,
oneway_keytab_name,
oneway_ccache_name,
config=cfg,
)
if cred.lifetime > 0:
have_ccache = True
except gssapi.exceptions.ExpiredCredentialsError:
except (gssapi.exceptions.ExpiredCredentialsError, gssapi.raw.misc.GSSError):
pass
if not have_ccache:
if os.path.exists(oneway_ccache_name):
os.unlink(oneway_ccache_name)
kinit_keytab(oneway_principal, oneway_keytab_name, oneway_ccache_name)
except gssapi.exceptions.GSSError:
kinit_keytab(
oneway_principal,
oneway_keytab_name,
oneway_ccache_name,
config=cfg,
)
except (gssapi.exceptions.GSSError, gssapi.raw.misc.GSSError):
# If there was failure on using keytab, assume it is stale and retrieve again
retrieve_keytab(api, ccache_name, oneway_keytab_name, oneway_principal)
if os.path.exists(oneway_ccache_name):
os.unlink(oneway_ccache_name)
kinit_keytab(oneway_principal, oneway_keytab_name, oneway_ccache_name)
cred = kinit_keytab(
oneway_principal,
oneway_keytab_name,
oneway_ccache_name,
config=cfg,
)
else:
cred = kinit_password(options.admin, options.password,
oneway_ccache_name,
canonicalize=True, enterprise=True)
cred = kinit_password(
options.admin,
options.password,
oneway_ccache_name,
canonicalize=True,
enterprise=True,
config=cfg,
)
if cred and cred.lifetime > 0:
have_ccache = True
if not have_ccache:
sys.exit(1)
# We are done: we have ccache with TDO credentials and can fetch domains
ipa_domain = api.env.domain
os.environ['KRB5CCNAME'] = oneway_ccache_name
os.environ["KRB5CCNAME"] = oneway_ccache_name
os.environ["KRB5_CONFIG"] = cfg
# retrieve the forest root domain name and contact it to retrieve trust
# topology info
forest_root = get_forest_root_domain(api, trusted_domain, server=options.server)
domains = dcerpc.fetch_domains(api, ipa_domain, forest_root, creds=True, server=options.server)
trust_domain_object = api.Command.trust_show(trusted_domain, raw=True)['result']
trust.add_new_domains_from_trust(api, None, trust_domain_object, domains)
forest_root = get_forest_root_domain(
api, trusted_domain, server=options.server
)
domains = dcerpc.fetch_domains(
api, ipa_domain, forest_root, creds=True, server=options.server
)
if old_ccache:
os.environ['KRB5CCNAME'] = old_ccache
os.environ["KRB5CCNAME"] = old_ccache
if old_config:
os.environ["KRB5_CONFIG"] = old_config
if cfg_file:
os.remove(cfg_file)
trust_domain_object = api.Command.trust_show(trusted_domain, raw=True)[
"result"
]
trust.add_new_domains_from_trust(api, None, trust_domain_object, domains)
sys.exit(0)

View File

@ -424,11 +424,11 @@ def fetch_trusted_domains_over_dbus(myapi, *keys, **options):
forest_name = keys[0]
method_options = []
if 'realm_server' in options:
if options.get('realm_server', None):
method_options.extend(['--server', options['realm_server']])
if 'realm_admin' in options:
if options.get('realm_admin', None):
method_options.extend(['--admin', options['realm_admin']])
if 'realm_passwd' in options:
if options.get('realm_passwd', None):
method_options.extend(['--password', options['realm_passwd']])
# Calling oddjobd-activated service via DBus has some quirks:
@ -458,11 +458,15 @@ def fetch_trusted_domains_over_dbus(myapi, *keys, **options):
except dbus.DBusException as e:
logger.error('Failed to call %s.fetch_domains helper.'
'DBus exception is %s.', DBUS_IFACE_TRUST, str(e))
if _ret != 0:
logger.error('Helper was called for forest %s, return code is %d',
forest_name, _ret)
logger.error('Standard output from the helper:\n%s---\n', _stdout)
logger.error('Error output from the helper:\n%s--\n', _stderr)
_ret = 2
_stdout = '<not available>'
_stderr = '<not available>'
if _ret != 0:
logger.error('Helper fetch_domains was called for forest %s, '
'return code is %d', forest_name, _ret)
logger.error('Standard output from the helper:\n%s---\n', _stdout)
logger.error('Error output from the helper:\n%s--\n', _stderr)
raise errors.ServerCommandError(
server=myapi.env.host,
error=_('Fetching domains from trusted forest failed. '
@ -801,7 +805,13 @@ ipa idrange-del before retrying the command with the desired range type.
# object credentials to authenticate to AD with Kerberos,
# run DCE RPC calls to do discovery and will call
# add_new_domains_from_trust() on its own.
fetch_trusted_domains_over_dbus(self.api, result['value'])
# We only pass through the realm_server option because we need
# to reach the specified Active Directory domain controller
# No need to pass through admin credentials as we have TDO
# credentials at this point already
fetch_trusted_domains_over_dbus(self.api, result['value'],
realm_server=options.get(
'realm_server', None))
# Format the output into human-readable values unless `--raw` is given
self._format_trust_attrs(result, **options)