Searching for Buffer-Overflow vulnerabilities
This notebook allows to search for potential Buffer-Overflow vulnerabilities in a Reven trace.
Prerequisites
- This notebook should be run in a jupyter notebook server equipped with a Reven python kernel.
Reven comes with a jupyter notebook server accessible with the
Open Pythonbutton in theAnalyzepage of any scenario. - This notebook depends on
capstonebeing installed in the Reven python kernel. To install capstone in the current environment, please execute the capstone cell of this notebook.
Running the notebook
Fill out the parameters in the Parameters cell below, then run all the cells of this notebook.
Note
Although the script is designed to limit false positive results, you may still encounter a few ones. Please check the results and feel free to report any issue, be it a false positive or a false negative ;-).
Source
# -*- coding: utf-8 -*-
# ---
# jupyter:
# jupytext:
# formats: ipynb,py:percent
# text_representation:
# extension: .py
# format_name: percent
# kernelspec:
# display_name: reven
# language: python
# name: reven-python3
# ---
# %% [markdown]
# # Searching for Buffer-Overflow vulnerabilities
#
# This notebook allows to search for potential Buffer-Overflow vulnerabilities in a Reven trace.
#
# ## Prerequisites
#
# - This notebook should be run in a jupyter notebook server equipped with a Reven python kernel.
# Reven comes with a jupyter notebook server accessible with the `Open Python` button in the `Analyze` page of any
# scenario.
#
# - This notebook depends on `capstone` being installed in the Reven python kernel.
# To install capstone in the current environment, please execute the [capstone cell](#Capstone-Installation) of this
# notebook.
#
#
# ## Running the notebook
#
# Fill out the parameters in the [Parameters cell](#Parameters) below, then run all the cells of this notebook.
#
#
# ## Note
#
# Although the script is designed to limit false positive results, you may still encounter a few ones. Please check
# the results and feel free to report any issue, be it a false positive or a false negative ;-).
# %% [markdown]
# # Capstone Installation
#
# Check for capstone's presence. If missing, attempt to get it from pip
# %%
try:
import capstone
print("capstone already installed")
except ImportError:
print("Could not find capstone, attempting to install it from pip")
import sys
import subprocess
command = [f"{sys.executable}", "-m", "pip", "install", "capstone"]
p = subprocess.run(command)
if int(p.returncode) != 0:
raise RuntimeError("Error installing capstone")
import capstone # noqa
print("Successfully installed capstone")
# %% [markdown]
# # Parameters
# %%
# Server connection
# Host of the Reven server running the scenario.
# When running this notebook from the Project Manager, '127.0.0.1' should be the correct value.
reven_backend_host = '127.0.0.1'
# Port of the Reven server running the scenario.
# After starting a Reven server on your scenario, you can get its port on the Analyze page of that scenario.
reven_backend_port = 13370
# Range control
# First transition considered for the detection of allocation/deallocation pairs
# If set to None, then the first transition of the trace
bof_from_tr = None
# bof_from_tr = 5300000 # ex: CVE-2020-17087 scenario
# First transition **not** considered for the detection of allocation/deallocation pairs
# If set to None, then the last transition of the trace
bof_to_tr = None
# bof_to_tr = 6100000 # ex: CVE-2020-17087 scenario
# Filter control
# Beware that, when filtering, if an allocation happens in the specified process and/or binary,
# the script will fail if the deallocation happens in a different process and/or binary.
# This issue should only happen for allocations in the kernel.
# Specify on which PID the allocation/deallocation pairs should be kept.
# Set a value of None to not filter on the PID.
faulty_process_pid = None
# faulty_process_pid = 756 # ex: CVE-2020-17087 scenario
# faulty_process_pid = 466 # ex: CVE-2021-3156 scenario
# Specify on which process name the allocation/deallocation pairs should be kept.
# Set a value of None to not filter on the process name.
# If both a process PID and a process name are specified, please make sure that they both
# refer to the same process, otherwise all allocations will be filtered and no results
# will be produced.
faulty_process_name = None
# faulty_process_name = "cve-2020-17087.exe" # ex: CVE-2020-17087 scenario
# faulty_process_name = "sudoedit" # ex: CVE-2021-3156 scenario
# Specify on which binary name the allocation/deallocation pairs should be kept.
# Set a value of None to not filter on the binary name.
# Only allocation/deallocation taking place in the binaries whose filename,
# path or name contain the specified value are kept.
# If filtering on both a process and a binary, please make sure that there are
# allocations taking place in that binary in the selected process, otherwise all
# allocations will be filtered and no result will be produced.
faulty_binary = None
# faulty_binary = "cng.sys" # ex: CVE-2020-17087 scenario
# faulty_binary = "sudoers.so" # ex: CVE-2021-3156 scenario
# Address control
# Specify a **physical** address suspected of being faulty here,
# to only test BoF for this specific address, instead of all (filtered) allocations.
# The address should still be returned by an allocation/deallocation pair.
# To get a physical address from a virtual address, find a context where the address
# is mapped, then use `virtual_address.translate(ctx)`.
bof_faulty_physical_address = None
# bof_faulty_physical_address = 0x7c5a1450 # ex: CVE-2020-17087 scenario
# bof_faulty_physical_address = 0x132498cd0 # ex: CVE-2021-3156 scenario
# Allocator control
# The script can use two allocators to find allocation/deallocation pairs.
# The following booleans allow to enable the search for allocations by these
# allocators for a scenario.
# Generally it is expected to have only a single allocator enabled for a given
# scenario.
# To add your own allocator, please look at how the two provided allocators were
# added.
# Whether or not to look for windows malloc/free allocation/deallocation pairs.
search_windows_malloc = True
# search_windows_malloc = False # ex: CVE-2020-17087 scenario
# search_windows_malloc = False # ex: CVE-2021-3156 scenario
# Whether or not to look for ExAllocatePoolWithTag/ExFreePoolWithTag
# allocation/deallocation pairs.
# This allocator is used by the Windows kernel.
search_pool_allocation = True
# search_pool_allocation = True # ex: CVE-2020-17087 scenario, kernel scenario
# search_pool_allocation = False # ex: CVE-2021-3156 scenario
# Whether or not to look for linux malloc/free allocation/deallocation pairs.
search_linux_malloc = False
# search_linux_malloc = False # ex: CVE-2020-17087 scenario, kernel scenario
# search_linux_malloc = True # ex: CVE-2021-3156 scenario
# Taint control
# Technical parameter: number of accesses in a taint after which the script gives up on
# that particular taint.
# As long taints degrade the performance of the script significantly, it is recommended to
# give up on a taint after it exceeds a certain number of operations.
# If you experience missing results, try increasing the value.
# If you experience a very long runtime for the script, try decreasing the value.
# The default value should be appropriate for most cases.
taint_max_length = 100000
# Technical parameter: number of bytes that we consider around an allocated buffer to determine if an access if a BoF
# (or underflow).
# Adjust this value to limit the number of false positives.
bof_overflow_limit = 1024
# %%
from collections import OrderedDict # noqa: E402
from typing import Dict, List # noqa: E402
import reven2 # noqa: E402
import reven2.preview.taint # noqa: E402
# %%
# Python script to connect to this scenario:
server = reven2.RevenServer(reven_backend_host, reven_backend_port)
print(server.trace.transition_count)
# %%
class MemoryRange:
page_size = 4096
page_mask = ~(page_size - 1)
def __init__(self, logical_address, size):
self.logical_address = logical_address
self.size = size
self.pages = [{
'logical_address': self.logical_address,
'size': self.size,
'physical_address': None,
'ctx_physical_address_mapped': None,
}]
# Compute the pages
while (((self.pages[-1]['logical_address'] & ~MemoryRange.page_mask) + self.pages[-1]['size'] - 1)
>= MemoryRange.page_size):
# Compute the size of the new page
new_page_size = ((self.pages[-1]['logical_address'] & ~MemoryRange.page_mask) + self.pages[-1]['size']
- MemoryRange.page_size)
# Reduce the size of the previous page and create the new one
self.pages[-1]['size'] -= new_page_size
self.pages.append({
'logical_address': self.pages[-1]['logical_address'] + self.pages[-1]['size'],
'size': new_page_size,
'physical_address': None,
'ctx_physical_address_mapped': None,
})
def try_translate_first_page(self, ctx):
if self.pages[0]['physical_address'] is not None:
return True
physical_address = reven2.address.LogicalAddress(self.pages[0]['logical_address']).translate(ctx)
if physical_address is None:
return False
self.pages[0]['physical_address'] = physical_address.offset
self.pages[0]['ctx_physical_address_mapped'] = ctx
return True
def try_translate_all_pages(self, ctx):
return_value = True
for page in self.pages:
if page['physical_address'] is not None:
continue
physical_address = reven2.address.LogicalAddress(page['logical_address']).translate(ctx)
if physical_address is None:
return_value = False
continue
page['physical_address'] = physical_address.offset
page['ctx_physical_address_mapped'] = ctx
return return_value
def is_physical_address_range_in_translated_pages(self, physical_address, size):
for page in self.pages:
if page['physical_address'] is None:
continue
if (
physical_address >= page['physical_address']
and physical_address + size <= page['physical_address'] + page['size']
):
return True
return False
def __repr__(self):
return "MemoryRange(0x%x, %d)" % (self.logical_address, self.size)
# Utils to translate the physical address of an address allocated just now
# - ctx should be the ctx where the address is located in `rax`
# - memory_range should be the range of memory of the newly allocated buffer
#
# We are using the translate API to translate it but sometimes just after the allocation
# the address isn't mapped yet. For that we are using the slicing and for all slice access
# we are trying to translate the address.
def translate_first_page_of_allocation(ctx, memory_range):
if memory_range.try_translate_first_page(ctx):
return
tainter = reven2.preview.taint.Tainter(server.trace)
taint = tainter.simple_taint(
tag0="rax",
from_context=ctx,
to_context=None,
is_forward=True
)
for access in taint.accesses(changes_only=False).all():
if memory_range.try_translate_first_page(access.transition.context_after()):
taint.cancel()
return
raise RuntimeError("Couldn't find the physical address of the first page")
# %%
class AllocEvent:
def __init__(self, memory_range, tr_begin, tr_end):
self.memory_range = memory_range
self.tr_begin = tr_begin
self.tr_end = tr_end
class FreeEvent:
def __init__(self, logical_address, tr_begin, tr_end):
self.logical_address = logical_address
self.tr_begin = tr_begin
self.tr_end = tr_end
def retrieve_events_for_symbol(
alloc_dict,
event_class,
symbol,
retrieve_event_info,
event_filter=None,
):
for ctx in server.trace.search.symbol(
symbol,
from_context=None if bof_from_tr is None else server.trace.context_before(bof_from_tr),
to_context=None if bof_to_tr is None else server.trace.context_before(bof_to_tr)
):
# We don't want hit on exception (code pagefault, hardware interrupts, etc)
if ctx.transition_after().exception is not None:
continue
previous_location = (ctx - 1).ossi.location()
previous_process = (ctx - 1).ossi.process()
# Filter by process pid/process name/binary name
# Filter by process pid
if faulty_process_pid is not None and previous_process.pid != faulty_process_pid:
continue
# Filter by process name
if faulty_process_name is not None and previous_process.name != faulty_process_name:
continue
# Filter by binary name / filename / path
if faulty_binary is not None and faulty_binary not in [
previous_location.binary.name,
previous_location.binary.filename,
previous_location.binary.path
]:
continue
# Filter the event with the argument filter
if event_filter is not None:
if event_filter(ctx.ossi.location(), previous_location):
continue
# Retrieve the call/ret
# The heuristic is that the ret is the end of our function
# - If the call is inlined it should be at the end of the caller function, so the ret is the ret of our
# function
# - If the call isn't inlined, the ret should be the ret of our function
ctx_call = next(ctx.stack.frames()).creation_transition.context_after()
ctx_ret = ctx_call.transition_before().find_inverse().context_before()
# Build the event by reading the needed registers
if event_class == AllocEvent:
current_address, size = retrieve_event_info(ctx, ctx_ret)
# Filter the alloc failing
if current_address == 0x0:
continue
memory_range = MemoryRange(current_address, size)
try:
translate_first_page_of_allocation(ctx_ret, memory_range)
except RuntimeError:
# If we can't translate the first page we assume that the buffer isn't used because
# the heuristic to detect the call/ret failed
continue
if memory_range.pages[0]['physical_address'] not in alloc_dict:
alloc_dict[memory_range.pages[0]['physical_address']] = []
alloc_dict[memory_range.pages[0]['physical_address']].append(
AllocEvent(
memory_range,
ctx.transition_after(), ctx_ret.transition_after()
)
)
elif event_class == FreeEvent:
current_address = retrieve_event_info(ctx, ctx_ret)
# Filter the free of NULL
if current_address == 0x0:
continue
current_physical_address = reven2.address.LogicalAddress(current_address).translate(ctx).offset
if current_physical_address not in alloc_dict:
alloc_dict[current_physical_address] = []
alloc_dict[current_physical_address].append(
FreeEvent(
current_address,
ctx.transition_after(), ctx_ret.transition_after()
)
)
else:
raise RuntimeError("Unknown event class: %s" % event_class.__name__)
# %%
# %%time
alloc_dict: Dict = {}
# Basic functions to retrieve the arguments
# They are working for the allocations/frees functions but won't work for all functions
# Particularly because on x86 we don't handle the size of the arguments
# nor if they are pushed left to right or right to left
def retrieve_first_argument(ctx):
if ctx.is64b():
return ctx.read(reven2.arch.x64.rcx)
else:
esp = ctx.read(reven2.arch.x64.esp)
return ctx.read(reven2.address.LogicalAddress(esp + 4, reven2.arch.x64.ss), 4)
def retrieve_second_argument(ctx):
if ctx.is64b():
return ctx.read(reven2.arch.x64.rdx)
else:
esp = ctx.read(reven2.arch.x64.esp)
return ctx.read(reven2.address.LogicalAddress(esp + 8, reven2.arch.x64.ss), 4)
def retrieve_first_argument_linux(ctx):
if ctx.is64b():
return ctx.read(reven2.arch.x64.rdi)
else:
raise NotImplementedError("Linux 32bits")
def retrieve_second_argument_linux(ctx):
if ctx.is64b():
return ctx.read(reven2.arch.x64.rsi)
else:
raise NotImplementedError("Linux 32bits")
def retrieve_return_value(ctx):
if ctx.is64b():
return ctx.read(reven2.arch.x64.rax)
else:
return ctx.read(reven2.arch.x64.eax)
def retrieve_alloc_info_with_size_as_first_argument(ctx_begin, ctx_end):
return (
retrieve_return_value(ctx_end),
retrieve_first_argument(ctx_begin)
)
def retrieve_alloc_info_with_size_as_first_argument_linux(ctx_begin, ctx_end):
return (
retrieve_return_value(ctx_end),
retrieve_first_argument_linux(ctx_begin)
)
def retrieve_alloc_info_with_size_as_second_argument(ctx_begin, ctx_end):
return (
retrieve_return_value(ctx_end),
retrieve_second_argument(ctx_begin)
)
def retrieve_alloc_info_with_size_as_second_argument_linux(ctx_begin, ctx_end):
return (
retrieve_return_value(ctx_end),
retrieve_second_argument_linux(ctx_begin)
)
def retrieve_alloc_info_for_calloc(ctx_begin, ctx_end):
return (
retrieve_return_value(ctx_end),
retrieve_first_argument(ctx_begin) * retrieve_second_argument(ctx_begin)
)
def retrieve_alloc_info_for_calloc_linux(ctx_begin, ctx_end):
return (
retrieve_return_value(ctx_end),
retrieve_first_argument_linux(ctx_begin) * retrieve_second_argument_linux(ctx_begin)
)
def retrieve_free_info_with_address_as_first_argument(ctx_begin, ctx_end):
return retrieve_first_argument(ctx_begin)
def retrieve_free_info_with_address_as_first_argument_linux(ctx_begin, ctx_end):
return retrieve_first_argument_linux(ctx_begin)
if search_windows_malloc:
def filter_in_realloc(location, caller_location):
return location.binary == caller_location.binary and caller_location.symbol.name == "realloc"
# Search for allocations with malloc
for symbol in server.ossi.symbols(r'^_?malloc$', binary_hint=r'msvcrt.dll'):
retrieve_events_for_symbol(alloc_dict, AllocEvent, symbol, retrieve_alloc_info_with_size_as_first_argument,
filter_in_realloc)
# Search for allocations with calloc
for symbol in server.ossi.symbols(r'^_?calloc(_crt)?$', binary_hint=r'msvcrt.dll'):
retrieve_events_for_symbol(alloc_dict, AllocEvent, symbol, retrieve_alloc_info_for_calloc)
# Search for deallocations with free
for symbol in server.ossi.symbols(r'^_?free$', binary_hint=r'msvcrt.dll'):
retrieve_events_for_symbol(alloc_dict, FreeEvent, symbol, retrieve_free_info_with_address_as_first_argument,
filter_in_realloc)
# Search for re-allocations with realloc
for symbol in server.ossi.symbols(r'^_?realloc$', binary_hint=r'msvcrt.dll'):
retrieve_events_for_symbol(alloc_dict, AllocEvent, symbol, retrieve_alloc_info_with_size_as_second_argument)
retrieve_events_for_symbol(alloc_dict, FreeEvent, symbol, retrieve_free_info_with_address_as_first_argument)
if search_pool_allocation:
# Search for allocations with ExAllocatePool...
def filter_ex_allocate_pool(location, caller_location):
return location.binary == caller_location.binary and caller_location.symbol.name.startswith("ExAllocatePool")
for symbol in server.ossi.symbols(r'^ExAllocatePool', binary_hint=r'ntoskrnl.exe'):
retrieve_events_for_symbol(alloc_dict, AllocEvent, symbol, retrieve_alloc_info_with_size_as_second_argument,
filter_ex_allocate_pool)
# Search for deallocations with ExFreePool...
def filter_ex_free_pool(location, caller_location):
return location.binary == caller_location.binary and caller_location.symbol.name == "ExFreePool"
for symbol in server.ossi.symbols(r'^ExFreePool', binary_hint=r'ntoskrnl.exe'):
retrieve_events_for_symbol(alloc_dict, FreeEvent, symbol, retrieve_free_info_with_address_as_first_argument,
filter_ex_free_pool)
if search_linux_malloc:
def filter_in_realloc(location, caller_location):
return (location.binary == caller_location.binary
and caller_location.symbol is not None
and caller_location.symbol.name in ["realloc", "__GI___libc_realloc"])
# Search for allocations with malloc
for symbol in server.ossi.symbols(r'^((__GI___libc_malloc)|(__libc_malloc))$', binary_hint=r'libc-.*.so'):
retrieve_events_for_symbol(alloc_dict, AllocEvent, symbol,
retrieve_alloc_info_with_size_as_first_argument_linux, filter_in_realloc)
# Search for allocations with calloc
for symbol in server.ossi.symbols(r'^((__calloc)|(__libc_calloc))$', binary_hint=r'libc-.*.so'):
retrieve_events_for_symbol(alloc_dict, AllocEvent, symbol, retrieve_alloc_info_for_calloc_linux)
# Search for deallocations with free
for symbol in server.ossi.symbols(r'^((__GI___libc_free)|(cfree))$', binary_hint=r'libc-.*.so'):
retrieve_events_for_symbol(alloc_dict, FreeEvent, symbol,
retrieve_free_info_with_address_as_first_argument_linux, filter_in_realloc)
# Search for re-allocations with realloc
for symbol in server.ossi.symbols(r'^((__GI___libc_realloc)|(realloc))$', binary_hint=r'libc-.*.so'):
retrieve_events_for_symbol(alloc_dict, AllocEvent, symbol,
retrieve_alloc_info_with_size_as_second_argument_linux)
retrieve_events_for_symbol(alloc_dict, FreeEvent, symbol,
retrieve_free_info_with_address_as_first_argument_linux)
# Sort the events per address and event type
for physical_address in alloc_dict.keys():
alloc_dict[physical_address] = list(sorted(
alloc_dict[physical_address],
key=lambda event: (event.tr_begin.id, 0 if isinstance(event, FreeEvent) else 1)
))
# Sort the dict by address
alloc_dict = OrderedDict(sorted(alloc_dict.items()))
# %%
def get_alloc_free_pairs(events, errors=None):
previous_event = None
for event in events:
if isinstance(event, AllocEvent):
if previous_event is None:
pass
elif isinstance(previous_event, AllocEvent):
if errors is not None:
errors.append("Two consecutives allocs found")
elif isinstance(event, FreeEvent):
if previous_event is None:
continue
elif isinstance(previous_event, FreeEvent):
if errors is not None:
errors.append("Two consecutives frees found")
elif isinstance(previous_event, AllocEvent):
yield (previous_event, event)
else:
assert 0, ("Unknown event type: %s" % type(event))
previous_event = event
if isinstance(previous_event, AllocEvent):
yield (previous_event, None)
# %%
# %%time
# Basic checks of the events
for physical_address, events in alloc_dict.items():
for event in events:
if not isinstance(event, AllocEvent) and not isinstance(event, FreeEvent):
raise RuntimeError("Unknown event type: %s" % type(event))
errors: List[str] = []
for (alloc_event, free_event) in get_alloc_free_pairs(events, errors):
# Check the uniformity of the logical address between the alloc and the free
if free_event is not None and alloc_event.memory_range.logical_address != free_event.logical_address:
errors.append("Phys:0x%x: Alloc #%d - Free #%d with different logical address: 0x%x != 0x%x" % (
physical_address,
alloc_event.tr_begin.id, free_event.tr_begin.id,
alloc_event.memory_range.logical_address, free_event.logical_address))
# Check size of 0x0
if alloc_event.memory_range.size == 0x0 or alloc_event.memory_range.size is None:
if free_event is None:
errors.append("Phys:0x%x: Alloc #%d - Free N/A with weird size %s" % (
physical_address,
alloc_event.tr_begin.id,
alloc_event.memory_range.size))
else:
errors.append("Phys:0x%x: Alloc #%d - Free #%d with weird size %s" % (
physical_address,
alloc_event.tr_begin.id, free_event.tr_begin.id,
alloc_event.memory_range.size))
if len(errors) > 0:
print("Phys:0x%x: Error(s) detected:" % (physical_address))
for error in errors:
print(" - %s" % error)
# %%
# Print the events
for physical_address, events in alloc_dict.items():
print("Phys:0x%x" % (physical_address))
print(" Events:")
for event in events:
if isinstance(event, AllocEvent):
print(" - Alloc at #%d (0x%x of size 0x%x)" % (event.tr_begin.id,
event.memory_range.logical_address, event.memory_range.size))
elif isinstance(event, FreeEvent):
print(" - Free at #%d (0x%x)" % (event.tr_begin.id, event.logical_address))
print(" Pairs:")
for (alloc_event, free_event) in get_alloc_free_pairs(events):
if free_event is None:
print(" - Allocated at #%d (0x%x of size 0x%x) and freed at N/A" % (alloc_event.tr_begin.id,
alloc_event.memory_range.logical_address, alloc_event.memory_range.size))
else:
print(" - Allocated at #%d (0x%x of size 0x%x) and freed at #%d (0x%x)" % (alloc_event.tr_begin.id,
alloc_event.memory_range.logical_address, alloc_event.memory_range.size, free_event.tr_begin.id,
free_event.logical_address))
print()
# %%
# Capstone utilities
def get_reven_register_from_name(name):
for reg in reven2.arch.helpers.x64_registers():
if reg.name == name:
return reg
raise RuntimeError("Unknown register: %s" % name)
def compute_dereferenced_address(ctx, cs_insn, cs_op):
dereferenced_address = 0
if cs_op.value.mem.base != 0:
dereferenced_address += ctx.read(get_reven_register_from_name(cs_insn.reg_name(cs_op.value.mem.base)))
if cs_op.value.mem.index != 0:
dereferenced_address += (cs_op.value.mem.scale
* ctx.read(get_reven_register_from_name(cs_insn.reg_name(cs_op.value.mem.index))))
dereferenced_address += cs_op.value.mem.disp
return dereferenced_address & 0xFFFFFFFFFFFFFFFF
# %%
# Function to compute the range of the intersection between two ranges
def range_intersect(r1, r2):
return range(max(r1.start, r2.start), min(r1.stop, r2.stop)) or None
def bof_analyze_function(physical_address, alloc_events):
bof_count = 0
# Setup capstone
md_64 = capstone.Cs(capstone.CS_ARCH_X86, capstone.CS_MODE_64)
md_64.detail = True
md_32 = capstone.Cs(capstone.CS_ARCH_X86, capstone.CS_MODE_32)
md_32.detail = True
errors = []
for (alloc_event, free_event) in get_alloc_free_pairs(alloc_events, errors):
# Setup the first taint [alloc; free]
tainter = reven2.preview.taint.Tainter(server.trace)
taint = tainter.simple_taint(
tag0="rax" if alloc_event.tr_end.context_before().is64b() else "eax",
from_context=alloc_event.tr_end.context_before(),
to_context=free_event.tr_begin.context_before() + 1 if free_event is not None else None,
is_forward=True
)
# Iterate on the slice
access_count = 0
for access in taint.accesses(changes_only=False).all():
access_count += 1
if access_count > taint_max_length:
if free_event is None:
print("Phys:0x%x: Allocated at #%d (0x%x of size 0x%x) and freed at N/A" % (physical_address,
alloc_event.tr_begin.id, alloc_event.memory_range.logical_address,
alloc_event.memory_range.size))
else:
print("Phys:0x%x: Allocated at #%d (0x%x of size 0x%x) and freed at #%d (0x%x)"
% (physical_address, alloc_event.tr_begin.id, alloc_event.memory_range.logical_address,
alloc_event.memory_range.size, free_event.tr_begin.id, free_event.logical_address))
print(" Warning: Allocation skipped: taint stopped after %d accesses" % access_count)
print()
break
ctx = access.transition.context_before()
md = md_64 if ctx.is64b() else md_32
cs_insn = next(md.disasm(access.transition.instruction.raw, access.transition.instruction.size))
# Skip `lea` instructions are they are not really memory read/write and the taint
# will propagate the taint anyway so that we will see the dereference of the computed value
if cs_insn.mnemonic == "lea":
continue
registers_in_state = {}
for reg_slice, _ in access.state_before().tainted_registers():
registers_in_state[reg_slice.register.name] = reg_slice
for cs_op in cs_insn.operands:
if cs_op.type != capstone.x86.X86_OP_MEM:
continue
bof_reg = None
if cs_op.value.mem.base != 0:
base_reg_name = cs_insn.reg_name(cs_op.value.mem.base)
if base_reg_name in registers_in_state:
bof_reg = registers_in_state[base_reg_name]
if bof_reg is None and cs_op.value.mem.index != 0:
index_reg_name = cs_insn.reg_name(cs_op.value.mem.index)
if index_reg_name in registers_in_state:
bof_reg = registers_in_state[index_reg_name]
if bof_reg is None:
continue
dereferenced_address = compute_dereferenced_address(ctx, cs_insn, cs_op)
# We only check on the translated pages as the taint won't return an access with a pagefault
# so the dereferenced address should be translated
dereferenced_physical_address = reven2.address.LogicalAddress(dereferenced_address).translate(ctx)
if dereferenced_physical_address is None:
continue
operand_range = range(dereferenced_address, dereferenced_address + cs_op.size)
before_buffer_range = range(alloc_event.memory_range.logical_address - bof_overflow_limit,
alloc_event.memory_range.logical_address)
after_buffer_range = range(alloc_event.memory_range.logical_address + alloc_event.memory_range.size,
alloc_event.memory_range.logical_address + alloc_event.memory_range.size
+ bof_overflow_limit)
if (range_intersect(operand_range, before_buffer_range) is None
and range_intersect(operand_range, after_buffer_range) is None):
continue
if free_event is None:
print("Phys:0x%x: Allocated at #%d (0x%x of size 0x%x) and freed at N/A" % (physical_address,
alloc_event.tr_begin.id, alloc_event.memory_range.logical_address,
alloc_event.memory_range.size))
else:
print("Phys:0x%x: Allocated at #%d (0x%x of size 0x%x) and freed at #%d (0x%x)"
% (physical_address, alloc_event.tr_begin.id, alloc_event.memory_range.logical_address,
alloc_event.memory_range.size, free_event.tr_begin.id, free_event.logical_address))
print(" BOF coming from reg %s[%d-%d] leading to dereferenced address = 0x%x"
% (bof_reg.register.name, bof_reg.begin, bof_reg.end, dereferenced_address))
print(" ", end="")
print(access.transition, end=" ")
print(ctx.ossi.location())
print()
bof_count += 1
if len(errors) > 0:
print("Phys:0x%x: Error(s) detected:" % (physical_address))
for error in errors:
print(" - %s" % error)
return bof_count
# %%
# %%time
bof_count = 0
if bof_faulty_physical_address is None:
for physical_address, alloc_events in alloc_dict.items():
bof_count += bof_analyze_function(physical_address, alloc_events)
else:
if bof_faulty_physical_address not in alloc_dict:
raise KeyError("The passed physical address was not detected during the allocation search")
bof_count += bof_analyze_function(bof_faulty_physical_address, alloc_dict[bof_faulty_physical_address])
print("---------------------------------------------------------------------------------")
bof_begin_range = "the beginning of the trace" if bof_from_tr is None else "#{}".format(bof_to_tr)
bof_end_range = "the end of the trace" if bof_to_tr is None else "#{}".format(bof_to_tr)
bof_range = ("on the whole trace" if bof_from_tr is None and bof_to_tr is None else
"between {} and {}".format(bof_begin_range, bof_end_range))
bof_range_size = server.trace.transition_count
if bof_from_tr is not None:
bof_range_size -= bof_from_tr
if bof_to_tr is not None:
bof_range_size -= server.trace.transition_count - bof_to_tr
if bof_faulty_physical_address is None:
searched_memory_addresses = "with {} searched memory addresses".format(len(alloc_dict))
else:
searched_memory_addresses = "on {:#x}".format(bof_faulty_physical_address)
print("{} BOF(s) found {} ({} transitions) {}".format(
bof_count, bof_range, bof_range_size, searched_memory_addresses
))
print("---------------------------------------------------------------------------------")