/usr/lib/python2.7/dist-packages/rekall/plugins/darwin/checks.py is in python-rekall-core 1.6.0+dfsg-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#
# Copyright 2013 Google Inc. All Rights Reserved.
#
# 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 2 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, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
"""Plugins for checking internal consistancy of pointers."""
__author__ = "Michael Cohen <scudette@google.com>"
from rekall import obj
from rekall import scan
from rekall import utils
from rekall.plugins.darwin import common
class DarwinFindSysent(common.AbstractDarwinParameterHook):
"""Find sysent by scanning around nsysent.
The production kernel no longer ships with the 'sysent' symbol,
which is the address of the syscall switch table. However, because
sysent and nsysent are initialized around the same time it works out that
they are always near each other.
This is an old technique, documented around the internet, for example here:
https://reverse.put.as/2010/11/27/a-semi-automated-way-to-find-sysent/
"""
name = "sysent_scan"
# Start looking 2560 pages below nsysent.
SYSENT_REL_OFFSET = -0x1000 * 0x1000
# Scan at most 2560 pages below and above.
LIMIT = 0x2000 * 0x1000
def scan(self, start, limit):
scanner = scan.FastStructScanner(
session=self.session,
profile=self.session.profile,
type_name="sysent",
expected_values=[
{"sy_arg_bytes": 0, "sy_narg": 0},
{"sy_arg_bytes": 4, "sy_narg": 1},
{"sy_arg_bytes": 0, "sy_narg": 0},
{"sy_arg_bytes": 12, "sy_narg": 3}],
address_space=self.session.default_address_space)
for hit in scanner.scan(offset=start, maxlen=limit):
return hit
def calculate(self):
nsysent_off = self.session.profile.get_constant(
"_nsysent", is_address=True)
if not nsysent_off:
return
return self.scan(start=nsysent_off + self.SYSENT_REL_OFFSET,
limit=self.LIMIT)
class DarwinCheckSysCalls(common.AbstractDarwinCommand):
"""Checks the syscall table."""
__name = "check_syscalls"
def CheckSyscallTables(self):
sysenter = self.profile.get_constant_object(
"_sysent",
target="Array",
target_args=dict(
count=self.profile.get_constant_object(
"_nsysent", "unsigned int"),
target="sysent"
)
)
# Resolve which kernel module or symbol the entry point is to.
resolver = self.session.address_resolver
for entry in sysenter:
call = entry.sy_call.deref()
yield entry, call, resolver.format_address(call)
def render(self, renderer):
renderer.table_header(
[("Index", "index", "6"),
("Address", "address", "[addrpad]"),
("Target", "target", "[addrpad]"),
("Symbol", "symbol", "")])
for i, (entry, call, symbol) in enumerate(self.CheckSyscallTables()):
renderer.table_row(i, entry, call, symbol)
class OIDInfo(object):
def __init__(self, oidp, names=None, numbers=None):
self.oidp = oidp
self._names = names or []
self._numbers = numbers or []
self.handler = None
def __iter__(self):
oidp = self.oidp
while oidp:
if oidp.oid_name:
yield OIDInfo(oidp, self._names, self._numbers)
oidp = oidp.oid_link.sle_next
@utils.safe_property
def perms(self):
return (("R" if self.oidp.oid_perms.CTLFLAG_RD else "-") +
("W" if self.oidp.oid_perms.CTLFLAG_WR else "-") +
("L" if self.oidp.oid_perms.CTLFLAG_LOCKED else "-"))
@utils.safe_property
def arg(self):
"""Decode the arg according to its type."""
if self.oidp.oid_kind_type == "CTLTYPE_NODE":
if self.oidp.oid_handler:
return "Node"
else:
names = self._names[:]
names.append(self.oidp.oid_name.deref())
numbers = self._numbers[:]
numbers.append(self.oidp.oid_number)
oid = self.oidp.oid_arg1.dereference_as("sysctl_oid_list")
return OIDInfo(oid.slh_first, names, numbers)
elif self.oidp.oid_kind_type == "CTLTYPE_INT":
return self.oidp.oid_arg1.dereference_as("int")
elif self.oidp.oid_kind_type == "CTLTYPE_STRING":
return self.oidp.oid_arg1.dereference_as("String")
elif self.oidp.oid_kind_type == "CTLTYPE_QUAD":
return self.oidp.oid_arg1.dereference_as("long long int")
elif self.oidp.oid_kind_type == "CTLTYPE_OPAQUE":
return self.oidp.oid_arg1.dereference_as("Void")
return obj.NoneObject("Unknown arg type")
@utils.safe_property
def name(self):
names = self._names[:]
names.append(self.oidp.oid_name.deref())
return ".".join(["%s" % x for x in names])
@utils.safe_property
def number(self):
numbers = self._numbers[:]
numbers.append(self.oidp.oid_number)
return ".".join(["%s" % x for x in numbers])
class DarwinSysctl(common.AbstractDarwinCommand):
"""Dumps the sysctl database.
On OSX the kernel is configured through the sysctl mechanism. This is
analogous to /proc or /sysfs on Linux. The configuration space is broken
into MIBs - or hierarchical namespace.
https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man8/sysctl.8.html
For example:
net.inet.ip.subnets_are_local
net.inet.ip.ttl
net.inet.ip.use_route_genid
This is implemented via a singly linked list of sysctl_oid structs. The
structs can be on the following types:
- CTLTYPE_INT means this MIB will handle an int.
- CTLTYPE_STRING means this MIB will handle a string.
- CTLTYPE_QUAD means this MIB will handle a long long int.
- CTLTYPE_NODE means this is a node which handles a sublevel of MIBs. It is
actually a pointer to a new sysctl_oid_list which handles the sublevel.
"""
__name = "sysctl"
def CheckSysctl(self):
sysctrl_list = self.profile.get_constant_object(
"_sysctl__children", "sysctl_oid_list")
oidinfo = OIDInfo(sysctrl_list.slh_first)
for oid in self._process(oidinfo):
yield oid
def _process(self, oidinfo):
# Output in sorted order since its eaiser to read.
for oid in sorted(oidinfo, key=lambda x: x.name):
if isinstance(oid.arg, OIDInfo):
for x in self._process(oid.arg):
yield x
else:
yield oid
table_header = [
dict(name="name", width=45),
dict(name="mib", width=16),
dict(name="perms", width=6),
dict(name="handler", style="address"),
dict(name="symbol", width=40),
dict(name="value")
]
def column_types(self):
return dict(name="",
mib="101.101.104",
perms="RWL",
handler=self.session.profile.Pointer(),
symbol=utils.FormattedAddress(
self.session.address_resolver, 0),
value="")
def collect(self):
for oid in self.CheckSysctl():
# Format the value nicely.
value = oid.arg
if isinstance(value, obj.Pointer):
value = "@ 0x%X" % int(value)
elif not value == None:
try:
value = int(value)
value = "0x%X (%d)" % (value, value)
except (ValueError, AttributeError):
pass
yield (oid.name,
oid.number,
oid.perms,
oid.oidp.oid_handler,
utils.FormattedAddress(
self.session.address_resolver,
oid.oidp.oid_handler),
value)
class CheckTrapTable(common.AbstractDarwinCommand):
"""Checks the traps table for hooks."""
__name = "check_trap_table"
def __init__(self, **kwargs):
super(CheckTrapTable, self).__init__(**kwargs)
# The mach_trap_t struct is not exported in debug symbols, but can be
# found here xnu-2422.1.72/bsd/dev/dtrace/systrace.c:
# typedef struct {
# int mach_trap_arg_count;
# kern_return_t (*mach_trap_function)(void *);
# #if defined(__x86_64__)
# mach_munge_t *mach_trap_arg_munge32;
# #endif
# int mach_trap_u32_words;
# #if MACH_ASSERT
# const char *mach_trap_name;
# #endif /* MACH_ASSERT */
# } mach_trap_t;
# We only really care about the mach_trap_function here.
if self.profile.metadata("arch") == "I386":
offset = 4
else:
offset = 8
self.profile.add_types({
"mach_trap": [16, {
"mach_trap_function": [offset, ["Pointer", dict(
target="Function"
)]]
}],
})
def CheckTrapTables(self):
# The trap table is simply an array of pointers to functions.
table = self.profile.get_constant_object(
"_mach_trap_table",
target="Array",
target_args=dict(
count=self.profile.get_constant_object(
"_mach_trap_count", "unsigned int"),
target="mach_trap",
)
)
resolver = self.session.address_resolver
for i, entry in enumerate(table):
call = entry.mach_trap_function.deref()
yield i, entry, call, resolver.format_address(call)
def render(self, renderer):
renderer.table_header([
("Index", "index", "[addr]"),
("Address", "address", "[addrpad]"),
("Target", "target", "[addrpad]"),
("Symbol", "symbol", "")])
for i, entry, call, sym_name in self.CheckTrapTables():
if call == None:
continue
renderer.table_row(i, entry, call, sym_name or "Unknown",
highlight=None if sym_name else "important")
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