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# Authors: Karl MacMillan <kmacmillan@mentalrootkit.com>
#
# Copyright (C) 2006 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
#
import re
import sys
from . import refpolicy
from . import access
from . import util
# Convenience functions
def get_audit_boot_msgs():
"""Obtain all of the avc and policy load messages from the audit
log. This function uses ausearch and requires that the current
process have sufficient rights to run ausearch.
Returns:
string contain all of the audit messages returned by ausearch.
"""
import subprocess
import time
fd=open("/proc/uptime", "r")
off=float(fd.read().split()[0])
fd.close
s = time.localtime(time.time() - off)
bootdate = time.strftime("%x", s)
boottime = time.strftime("%X", s)
output = subprocess.Popen(["/sbin/ausearch", "-m", "AVC,USER_AVC,MAC_POLICY_LOAD,DAEMON_START,SELINUX_ERR", "-ts", bootdate, boottime],
stdout=subprocess.PIPE).communicate()[0]
if util.PY3:
output = util.decode_input(output)
return output
def get_audit_msgs():
"""Obtain all of the avc and policy load messages from the audit
log. This function uses ausearch and requires that the current
process have sufficient rights to run ausearch.
Returns:
string contain all of the audit messages returned by ausearch.
"""
import subprocess
output = subprocess.Popen(["/sbin/ausearch", "-m", "AVC,USER_AVC,MAC_POLICY_LOAD,DAEMON_START,SELINUX_ERR"],
stdout=subprocess.PIPE).communicate()[0]
if util.PY3:
output = util.decode_input(output)
return output
def get_dmesg_msgs():
"""Obtain all of the avc and policy load messages from /bin/dmesg.
Returns:
string contain all of the audit messages returned by dmesg.
"""
import subprocess
output = subprocess.Popen(["/bin/dmesg"],
stdout=subprocess.PIPE).communicate()[0]
if util.PY3:
output = util.decode_input(output)
return output
# Classes representing audit messages
class AuditMessage:
"""Base class for all objects representing audit messages.
AuditMessage is a base class for all audit messages and only
provides storage for the raw message (as a string) and a
parsing function that does nothing.
"""
def __init__(self, message):
self.message = message
self.header = ""
def from_split_string(self, recs):
"""Parse a string that has been split into records by space into
an audit message.
This method should be overridden by subclasses. Error reporting
should be done by raise ValueError exceptions.
"""
for msg in recs:
fields = msg.split("=")
if len(fields) != 2:
if msg[:6] == "audit(":
self.header = msg
return
else:
continue
if fields[0] == "msg":
self.header = fields[1]
return
class InvalidMessage(AuditMessage):
"""Class representing invalid audit messages. This is used to differentiate
between audit messages that aren't recognized (that should return None from
the audit message parser) and a message that is recognized but is malformed
in some way.
"""
def __init__(self, message):
AuditMessage.__init__(self, message)
class PathMessage(AuditMessage):
"""Class representing a path message"""
def __init__(self, message):
AuditMessage.__init__(self, message)
self.path = ""
def from_split_string(self, recs):
AuditMessage.from_split_string(self, recs)
for msg in recs:
fields = msg.split("=")
if len(fields) != 2:
continue
if fields[0] == "path":
self.path = fields[1][1:-1]
return
import selinux.audit2why as audit2why
avcdict = {}
class AVCMessage(AuditMessage):
"""AVC message representing an access denial or granted message.
This is a very basic class and does not represent all possible fields
in an avc message. Currently the fields are:
scontext - context for the source (process) that generated the message
tcontext - context for the target
tclass - object class for the target (only one)
comm - the process name
exe - the on-disc binary
path - the path of the target
access - list of accesses that were allowed or denied
denial - boolean indicating whether this was a denial (True) or granted
(False) message.
An example audit message generated from the audit daemon looks like (line breaks
added):
'type=AVC msg=audit(1155568085.407:10877): avc: denied { search } for
pid=677 comm="python" name="modules" dev=dm-0 ino=13716388
scontext=user_u:system_r:setroubleshootd_t:s0
tcontext=system_u:object_r:modules_object_t:s0 tclass=dir'
An example audit message stored in syslog (not processed by the audit daemon - line
breaks added):
'Sep 12 08:26:43 dhcp83-5 kernel: audit(1158064002.046:4): avc: denied { read }
for pid=2 496 comm="bluez-pin" name=".gdm1K3IFT" dev=dm-0 ino=3601333
scontext=user_u:system_r:bluetooth_helper_t:s0-s0:c0
tcontext=system_u:object_r:xdm_tmp_t:s0 tclass=file
"""
def __init__(self, message):
AuditMessage.__init__(self, message)
self.scontext = refpolicy.SecurityContext()
self.tcontext = refpolicy.SecurityContext()
self.tclass = ""
self.comm = ""
self.exe = ""
self.path = ""
self.name = ""
self.ino = ""
self.accesses = []
self.denial = True
self.type = audit2why.TERULE
def __parse_access(self, recs, start):
# This is kind of sucky - the access that is in a space separated
# list like '{ read write }'. This doesn't fit particularly well with splitting
# the string on spaces. This function takes the list of recs and a starting
# position one beyond the open brace. It then adds the accesses until it finds
# the close brace or the end of the list (which is an error if reached without
# seeing a close brace).
found_close = False
i = start
if i == (len(recs) - 1):
raise ValueError("AVC message in invalid format [%s]\n" % self.message)
while i < len(recs):
if recs[i] == "}":
found_close = True
break
self.accesses.append(recs[i])
i = i + 1
if not found_close:
raise ValueError("AVC message in invalid format [%s]\n" % self.message)
return i + 1
def from_split_string(self, recs):
AuditMessage.from_split_string(self, recs)
# FUTURE - fully parse avc messages and store all possible fields
# Required fields
found_src = False
found_tgt = False
found_class = False
found_access = False
for i in range(len(recs)):
if recs[i] == "{":
i = self.__parse_access(recs, i + 1)
found_access = True
continue
elif recs[i] == "granted":
self.denial = False
fields = recs[i].split("=")
if len(fields) != 2:
continue
if fields[0] == "scontext":
self.scontext = refpolicy.SecurityContext(fields[1])
found_src = True
elif fields[0] == "tcontext":
self.tcontext = refpolicy.SecurityContext(fields[1])
found_tgt = True
elif fields[0] == "tclass":
self.tclass = fields[1]
found_class = True
elif fields[0] == "comm":
self.comm = fields[1][1:-1]
elif fields[0] == "exe":
self.exe = fields[1][1:-1]
elif fields[0] == "name":
self.name = fields[1][1:-1]
elif fields[0] == "path":
self.path = fields[1][1:-1]
elif fields[0] == "ino":
self.ino = fields[1]
if not found_src or not found_tgt or not found_class or not found_access:
raise ValueError("AVC message in invalid format [%s]\n" % self.message)
self.analyze()
def analyze(self):
tcontext = self.tcontext.to_string()
scontext = self.scontext.to_string()
access_tuple = tuple( self.accesses)
self.data = []
if (scontext, tcontext, self.tclass, access_tuple) in avcdict.keys():
self.type, self.data = avcdict[(scontext, tcontext, self.tclass, access_tuple)]
else:
self.type, self.data = audit2why.analyze(scontext, tcontext, self.tclass, self.accesses);
if self.type == audit2why.NOPOLICY:
self.type = audit2why.TERULE
if self.type == audit2why.BADTCON:
raise ValueError("Invalid Target Context %s\n" % tcontext)
if self.type == audit2why.BADSCON:
raise ValueError("Invalid Source Context %s\n" % scontext)
if self.type == audit2why.BADSCON:
raise ValueError("Invalid Type Class %s\n" % self.tclass)
if self.type == audit2why.BADPERM:
raise ValueError("Invalid permission %s\n" % " ".join(self.accesses))
if self.type == audit2why.BADCOMPUTE:
raise ValueError("Error during access vector computation")
if self.type == audit2why.CONSTRAINT:
self.data = [ self.data ]
if self.scontext.user != self.tcontext.user:
self.data.append(("user (%s)" % self.scontext.user, 'user (%s)' % self.tcontext.user))
if self.scontext.role != self.tcontext.role and self.tcontext.role != "object_r":
self.data.append(("role (%s)" % self.scontext.role, 'role (%s)' % self.tcontext.role))
if self.scontext.level != self.tcontext.level:
self.data.append(("level (%s)" % self.scontext.level, 'level (%s)' % self.tcontext.level))
avcdict[(scontext, tcontext, self.tclass, access_tuple)] = (self.type, self.data)
class PolicyLoadMessage(AuditMessage):
"""Audit message indicating that the policy was reloaded."""
def __init__(self, message):
AuditMessage.__init__(self, message)
class DaemonStartMessage(AuditMessage):
"""Audit message indicating that a daemon was started."""
def __init__(self, message):
AuditMessage.__init__(self, message)
self.auditd = False
def from_split_string(self, recs):
AuditMessage.from_split_string(self, recs)
if "auditd" in recs:
self.auditd = True
class ComputeSidMessage(AuditMessage):
"""Audit message indicating that a sid was not valid.
Compute sid messages are generated on attempting to create a security
context that is not valid. Security contexts are invalid if the role is
not authorized for the user or the type is not authorized for the role.
This class does not store all of the fields from the compute sid message -
just the type and role.
"""
def __init__(self, message):
AuditMessage.__init__(self, message)
self.invalid_context = refpolicy.SecurityContext()
self.scontext = refpolicy.SecurityContext()
self.tcontext = refpolicy.SecurityContext()
self.tclass = ""
def from_split_string(self, recs):
AuditMessage.from_split_string(self, recs)
if len(recs) < 10:
raise ValueError("Split string does not represent a valid compute sid message")
try:
self.invalid_context = refpolicy.SecurityContext(recs[5])
self.scontext = refpolicy.SecurityContext(recs[7].split("=")[1])
self.tcontext = refpolicy.SecurityContext(recs[8].split("=")[1])
self.tclass = recs[9].split("=")[1]
except:
raise ValueError("Split string does not represent a valid compute sid message")
def output(self):
return "role %s types %s;\n" % (self.role, self.type)
# Parser for audit messages
class AuditParser:
"""Parser for audit messages.
This class parses audit messages and stores them according to their message
type. This is not a general purpose audit message parser - it only extracts
selinux related messages.
Each audit messages are stored in one of four lists:
avc_msgs - avc denial or granted messages. Messages are stored in
AVCMessage objects.
comput_sid_messages - invalid sid messages. Messages are stored in
ComputSidMessage objects.
invalid_msgs - selinux related messages that are not valid. Messages
are stored in InvalidMessageObjects.
policy_load_messages - policy load messages. Messages are stored in
PolicyLoadMessage objects.
These lists will be reset when a policy load message is seen if
AuditParser.last_load_only is set to true. It is assumed that messages
are fed to the parser in chronological order - time stamps are not
parsed.
"""
def __init__(self, last_load_only=False):
self.__initialize()
self.last_load_only = last_load_only
def __initialize(self):
self.avc_msgs = []
self.compute_sid_msgs = []
self.invalid_msgs = []
self.policy_load_msgs = []
self.path_msgs = []
self.by_header = { }
self.check_input_file = False
self.inode_dict = { }
self.__store_base_types()
# Low-level parsing function - tries to determine if this audit
# message is an SELinux related message and then parses it into
# the appropriate AuditMessage subclass. This function deliberately
# does not impose policy (e.g., on policy load message) or store
# messages to make as simple and reusable as possible.
#
# Return values:
# None - no recognized audit message found in this line
#
# InvalidMessage - a recognized but invalid message was found.
#
# AuditMessage (or subclass) - object representing a parsed
# and valid audit message.
def __parse_line(self, line):
# strip("\x1c\x1d\x1e\x85") is only needed for python2
# since str.split() in python3 already does this
rec = [x.strip("\x1c\x1d\x1e\x85") for x in line.split()]
for i in rec:
found = False
if i == "avc:" or i == "message=avc:" or i == "msg='avc:":
msg = AVCMessage(line)
found = True
elif i == "security_compute_sid:":
msg = ComputeSidMessage(line)
found = True
elif i == "type=MAC_POLICY_LOAD" or i == "type=1403":
msg = PolicyLoadMessage(line)
found = True
elif i == "type=AVC_PATH":
msg = PathMessage(line)
found = True
elif i == "type=DAEMON_START":
msg = DaemonStartMessage(list)
found = True
if found:
self.check_input_file = True
try:
msg.from_split_string(rec)
except ValueError:
msg = InvalidMessage(line)
return msg
return None
# Higher-level parse function - take a line, parse it into an
# AuditMessage object, and store it in the appropriate list.
# This function will optionally reset all of the lists when
# it sees a load policy message depending on the value of
# self.last_load_only.
def __parse(self, line):
msg = self.__parse_line(line)
if msg is None:
return
# Append to the correct list
if isinstance(msg, PolicyLoadMessage):
if self.last_load_only:
self.__initialize()
elif isinstance(msg, DaemonStartMessage):
# We initialize every time the auditd is started. This
# is less than ideal, but unfortunately it is the only
# way to catch reboots since the initial policy load
# by init is not stored in the audit log.
if msg.auditd and self.last_load_only:
self.__initialize()
self.policy_load_msgs.append(msg)
elif isinstance(msg, AVCMessage):
self.avc_msgs.append(msg)
elif isinstance(msg, ComputeSidMessage):
self.compute_sid_msgs.append(msg)
elif isinstance(msg, InvalidMessage):
self.invalid_msgs.append(msg)
elif isinstance(msg, PathMessage):
self.path_msgs.append(msg)
# Group by audit header
if msg.header != "":
if msg.header in self.by_header:
self.by_header[msg.header].append(msg)
else:
self.by_header[msg.header] = [msg]
# Post processing will add additional information from AVC messages
# from related messages - only works on messages generated by
# the audit system.
def __post_process(self):
for value in self.by_header.values():
avc = []
path = None
for msg in value:
if isinstance(msg, PathMessage):
path = msg
elif isinstance(msg, AVCMessage):
avc.append(msg)
if len(avc) > 0 and path:
for a in avc:
a.path = path.path
def parse_file(self, input):
"""Parse the contents of a file object. This method can be called
multiple times (along with parse_string)."""
line = input.readline()
while line:
self.__parse(line)
line = input.readline()
if not self.check_input_file:
sys.stderr.write("Nothing to do\n")
sys.exit(0)
self.__post_process()
def parse_string(self, input):
"""Parse a string containing audit messages - messages should
be separated by new lines. This method can be called multiple
times (along with parse_file)."""
lines = input.split('\n')
for l in lines:
self.__parse(l)
self.__post_process()
def to_role(self, role_filter=None):
"""Return RoleAllowSet statements matching the specified filter
Filter out types that match the filer, or all roles
Params:
role_filter - [optional] Filter object used to filter the
output.
Returns:
Access vector set representing the denied access in the
audit logs parsed by this object.
"""
role_types = access.RoleTypeSet()
for cs in self.compute_sid_msgs:
if not role_filter or role_filter.filter(cs):
role_types.add(cs.invalid_context.role, cs.invalid_context.type)
return role_types
def __restore_path(self, name, inode):
import subprocess
import os
path = ""
# Optimizing
if name == "" or inode == "":
return path
for d in self.inode_dict:
if d == inode and self.inode_dict[d] == name:
return path
if d == inode and self.inode_dict[d] != name:
return self.inode_dict[d]
if inode not in self.inode_dict.keys():
self.inode_dict[inode] = name
command = "locate -b '\%s'" % name
try:
output = subprocess.check_output(command,
stderr=subprocess.STDOUT,
shell=True,
universal_newlines=True)
try:
ino = int(inode)
except ValueError:
pass
for file in output.split("\n"):
try:
if int(os.lstat(file).st_ino) == ino:
self.inode_dict[inode] = path = file
return path
except:
pass
except subprocess.CalledProcessError as e:
pass
return path
def __store_base_types(self):
import sepolicy
self.base_types = sepolicy.get_types_from_attribute("base_file_type")
def __get_base_type(self, tcontext, scontext):
import sepolicy
# Prevent unnecessary searching
if (self.old_scontext == scontext and
self.old_tcontext == tcontext):
return
self.old_scontext = scontext
self.old_tcontext = tcontext
for btype in self.base_types:
if btype == tcontext:
for writable in sepolicy.get_writable_files(scontext):
if writable.endswith(tcontext) and writable.startswith(scontext.rstrip("_t")):
return writable
return 0
def to_access(self, avc_filter=None, only_denials=True):
"""Convert the audit logs access into a an access vector set.
Convert the audit logs into an access vector set, optionally
filtering the restults with the passed in filter object.
Filter objects are object instances with a .filter method
that takes and access vector and returns True if the message
should be included in the final output and False otherwise.
Params:
avc_filter - [optional] Filter object used to filter the
output.
Returns:
Access vector set representing the denied access in the
audit logs parsed by this object.
"""
av_set = access.AccessVectorSet()
self.old_scontext = ""
self.old_tcontext = ""
for avc in self.avc_msgs:
if avc.denial != True and only_denials:
continue
base_type = self.__get_base_type(avc.tcontext.type, avc.scontext.type)
if avc.path == "":
avc.path = self.__restore_path(avc.name, avc.ino)
if avc_filter:
if avc_filter.filter(avc):
av_set.add(avc.scontext.type, avc.tcontext.type, avc.tclass,
avc.accesses, avc.path, base_type, avc,
avc_type=avc.type, data=avc.data)
else:
av_set.add(avc.scontext.type, avc.tcontext.type, avc.tclass,
avc.accesses, avc.path, base_type, avc,
avc_type=avc.type, data=avc.data)
return av_set
class AVCTypeFilter:
def __init__(self, regex):
self.regex = re.compile(regex)
def filter(self, avc):
if self.regex.match(avc.scontext.type):
return True
if self.regex.match(avc.tcontext.type):
return True
return False
class ComputeSidTypeFilter:
def __init__(self, regex):
self.regex = re.compile(regex)
def filter(self, avc):
if self.regex.match(avc.invalid_context.type):
return True
if self.regex.match(avc.scontext.type):
return True
if self.regex.match(avc.tcontext.type):
return True
return False