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# Utility methods for security descriptor manipulation
#
# Copyright Nadezhda Ivanova 2010 <nivanova@samba.org>
#
# 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/>.
#
"""Utility methods for security descriptor manipulation."""
import samba
from ldb import Message, MessageElement, Dn
from ldb import FLAG_MOD_REPLACE, SCOPE_BASE
from samba.ndr import ndr_pack, ndr_unpack, ndr_deepcopy
from samba.dcerpc import security
from samba.ntstatus import (
NT_STATUS_OBJECT_NAME_NOT_FOUND,
)
class SDUtils(object):
"""Some utilities for manipulation of security descriptors on objects."""
def __init__(self, samdb):
self.ldb = samdb
self.domain_sid = security.dom_sid(self.ldb.get_domain_sid())
def modify_sd_on_dn(self, object_dn, sd, controls=None):
"""Modify security descriptor using either SDDL string
or security.descriptor object
"""
m = Message()
if isinstance(object_dn, Dn):
m.dn = object_dn
else:
m.dn = Dn(self.ldb, object_dn)
assert(isinstance(sd, str) or isinstance(sd, security.descriptor))
if isinstance(sd, str):
tmp_desc = security.descriptor.from_sddl(sd, self.domain_sid)
elif isinstance(sd, security.descriptor):
tmp_desc = sd
m["nTSecurityDescriptor"] = MessageElement(ndr_pack(tmp_desc),
FLAG_MOD_REPLACE,
"nTSecurityDescriptor")
self.ldb.modify(m, controls)
def read_sd_on_dn(self, object_dn, controls=None):
res = self.ldb.search(object_dn, SCOPE_BASE, None,
["nTSecurityDescriptor"], controls=controls)
desc = res[0]["nTSecurityDescriptor"][0]
return ndr_unpack(security.descriptor, desc)
def get_object_sid(self, object_dn):
res = self.ldb.search(object_dn)
return ndr_unpack(security.dom_sid, res[0]["objectSid"][0])
def update_aces_in_dacl(self, dn, del_aces=None, add_aces=None,
sddl_attr=None, controls=None):
if del_aces is None:
del_aces=[]
if add_aces is None:
add_aces=[]
def ace_from_sddl(ace_sddl):
ace_sd = security.descriptor.from_sddl("D:" + ace_sddl, self.domain_sid)
assert(len(ace_sd.dacl.aces)==1)
return ace_sd.dacl.aces[0]
if sddl_attr is None:
if controls is None:
controls=["sd_flags:1:%d" % security.SECINFO_DACL]
sd = self.read_sd_on_dn(dn, controls=controls)
if not sd.type & security.SEC_DESC_DACL_PROTECTED:
# if the DACL is not protected remove all
# inherited aces, as they will be re-inherited
# on the server, we need a ndr_deepcopy in order
# to avoid reference problems while deleting
# the aces while looping over them
dacl_copy = ndr_deepcopy(sd.dacl)
for ace in dacl_copy.aces:
if ace.flags & security.SEC_ACE_FLAG_INHERITED_ACE:
try:
sd.dacl_del_ace(ace)
except samba.NTSTATUSError as err:
if err.args[0] != NT_STATUS_OBJECT_NAME_NOT_FOUND:
raise err
# dacl_del_ace may remove more than
# one ace, so we may not find it anymore
pass
else:
if controls is None:
controls=[]
res = self.ldb.search(dn, SCOPE_BASE, None,
[sddl_attr], controls=controls)
old_sddl = str(res[0][sddl_attr][0])
sd = security.descriptor.from_sddl(old_sddl, self.domain_sid)
num_changes = 0
del_ignored = []
add_ignored = []
inherited_ignored = []
for ace in del_aces:
if isinstance(ace, str):
ace = ace_from_sddl(ace)
assert(isinstance(ace, security.ace))
if ace.flags & security.SEC_ACE_FLAG_INHERITED_ACE:
inherited_ignored.append(ace)
continue
if ace not in sd.dacl.aces:
del_ignored.append(ace)
continue
sd.dacl_del_ace(ace)
num_changes += 1
for ace in add_aces:
add_idx = -1
if isinstance(ace, dict):
if "idx" in ace:
add_idx = ace["idx"]
ace = ace["ace"]
if isinstance(ace, str):
ace = ace_from_sddl(ace)
assert(isinstance(ace, security.ace))
if ace.flags & security.SEC_ACE_FLAG_INHERITED_ACE:
inherited_ignored.append(ace)
continue
if ace in sd.dacl.aces:
add_ignored.append(ace)
continue
sd.dacl_add(ace, add_idx)
num_changes += 1
if num_changes == 0:
return del_ignored, add_ignored, inherited_ignored
if sddl_attr is None:
self.modify_sd_on_dn(dn, sd, controls=controls)
else:
new_sddl = sd.as_sddl(self.domain_sid)
m = Message()
m.dn = dn
m[sddl_attr] = MessageElement(new_sddl.encode('ascii'),
FLAG_MOD_REPLACE,
sddl_attr)
self.ldb.modify(m, controls=controls)
return del_ignored, add_ignored, inherited_ignored
def dacl_prepend_aces(self, object_dn, aces, controls=None):
"""Prepend an ACE (or more) to an objects security descriptor
"""
ace_sd = security.descriptor.from_sddl("D:" + aces, self.domain_sid)
add_aces = []
add_idx = 0
for ace in ace_sd.dacl.aces:
add_aces.append({"idx": add_idx, "ace": ace})
add_idx += 1
_,ai,ii = self.update_aces_in_dacl(object_dn, add_aces=add_aces,
controls=controls)
return ai, ii
def dacl_add_ace(self, object_dn, ace):
"""Add an ACE (or more) to an objects security descriptor
"""
_,_ = self.dacl_prepend_aces(object_dn, ace,
controls=["show_deleted:1"])
def dacl_append_aces(self, object_dn, aces, controls=None):
"""Append an ACE (or more) to an objects security descriptor
"""
ace_sd = security.descriptor.from_sddl("D:" + aces, self.domain_sid)
add_aces = []
for ace in ace_sd.dacl.aces:
add_aces.append(ace)
_,ai,ii = self.update_aces_in_dacl(object_dn, add_aces=add_aces,
controls=controls)
return ai, ii
def dacl_delete_aces(self, object_dn, aces, controls=None):
"""Delete an ACE (or more) to an objects security descriptor
"""
del_sd = security.descriptor.from_sddl("D:" + aces, self.domain_sid)
del_aces = []
for ace in del_sd.dacl.aces:
del_aces.append(ace)
di,_,ii = self.update_aces_in_dacl(object_dn, del_aces=del_aces,
controls=controls)
return di, ii
def get_sd_as_sddl(self, object_dn, controls=None):
"""Return object nTSecurityDescriptor in SDDL format
"""
if controls is None:
controls = []
desc = self.read_sd_on_dn(object_dn, controls + ["show_deleted:1"])
return desc.as_sddl(self.domain_sid)
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