Initial commit
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commit
d2e3722772
1
.gitignore
vendored
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1
.gitignore
vendored
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Build
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248
asan_example.cpp
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248
asan_example.cpp
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#include <sanitizer/asan_interface.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <assert.h>
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#include <string.h>
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#define IsPowerOfTwo(value, pot) ((((size_t)value) & (((size_t)pot) - 1)) == 0)
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#define AsanAlignment 8
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#define PrintByteSpacing(space) \
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if (index) \
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printf(space); \
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if (index && (index % 8 == 0)) \
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printf("| ")
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static void PrintByteArray(char const *array, size_t array_size)
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{
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printf(" Byte Array ");
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for (size_t index = 0 ; index < array_size; index++) {
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PrintByteSpacing(" ");
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printf("%02zu", index);
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}
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printf("\n");
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}
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static void PrintPoisonedBytes(int step, char const *array, size_t array_size)
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{
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printf("%d. __asan_address_is_poisoned ", step);
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for (size_t index = 0 ; index < array_size; index++) {
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PrintByteSpacing(" ");
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printf("%c", __asan_address_is_poisoned(array + index) ? 'x' : ' ');
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}
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printf("\n");
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}
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static void PrintPoisonMemoryIndex(int step, char const *array, size_t array_size, size_t poison_index)
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{
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printf("%d. __asan_poison_memory_region ", step);
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for (size_t index = 0; index < array_size; index++) {
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PrintByteSpacing(" ");
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printf("%c ", index == poison_index ? 'x' : ' ');
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}
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printf("\n");
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}
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static void PrintPoisonMemoryRegion(int step, char const *array, size_t array_size, size_t poison_start_index, size_t poison_end_index)
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{
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printf("%d. __asan_poison_memory_region ", step);
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for (size_t index = 0; index < array_size; index++) {
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PrintByteSpacing(" ");
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printf("%c ", index >= poison_start_index && index <= poison_end_index ? 'x' : ' ');
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}
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printf("\n");
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}
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int main()
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{
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printf(
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"# ASAN Manual Poisoning\n"
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"\n"
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"## TLDR\n"
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"\n"
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"`__asan_poison_memory_region(ptr, size)`\n"
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"\n"
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"Poisons the byte region `[ptr, AlignDown(ptr+size, 8))`\n"
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"\n"
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"`__asan_unpoison_memory_region(ptr, size)`\n"
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"\n"
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"Unpoisons the byte region `[AlignDown(ptr, 8), ptr+size)`\n"
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"\n"
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"Use the provided macros that are conditionally enabled if ASAN is\n"
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"defined from `<sanitizer/asan_interface.h>`.\n"
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"\n"
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"```\n"
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"ASAN_POISON_MEMORY_REGION(addr, size)\n"
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"ASAN_UNPOISON_MEMORY_REGION(addr, size)\n"
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"```\n"
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"\n"
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"If in doubt, use `__asan_address_is_poisoned` to sanity check the\n"
|
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"ranges requested to be un/poisoned to avoid potential gaps in\n"
|
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"marked-up memory that may lead to undetected read/writes.\n"
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"\n"
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"## Overview\n"
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"\n"
|
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"ASAN provides a way to manually markup ranges of bytes to\n"
|
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"prohibit or permit reads to those addresses. There's a short\n"
|
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"foot-note in Google's "
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"[AddressSanitizerManualPoisoning](https://github.com/google/"
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"sanitizers/wiki/AddressSanitizerManualPoisoning)\n"
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"documentation that states:\n"
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"\n"
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"```\n"
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"If you have a custom allocation arena, the typical workflow would be\n"
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"to poison the entire arena first, and then unpoison allocated chunks\n"
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"of memory leaving poisoned redzones between them. The allocated\n"
|
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"chunks should start with 8-aligned addresses.\n"
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"```\n"
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"\n"
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"This repository runs some simple tests to clarify the behaviour of\n"
|
||||
"the API on un/aligned addresses at various sizes without having\n"
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"to dig into source code or read the [ASAN paper](https://static."
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"googleusercontent.com/media/research.google.com/en/pubs/archive/"
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"37752.pdf).\n"
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"\n"
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"We use a stack-allocated 16 byte array and test un/poisoning\n"
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"various ranges of bytes from different alignments to clarify the\n"
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"poisoning behaviour of the API.\n"
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"\n"
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"This reveals that calling the API haphazardly, unaligned or\n"
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"straddling boundaries can lead to gaps in poisoned memory and hide\n"
|
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"potential leaks (as also demonstrated in [Manual ASAN poisoning and\n"
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"alignment](https://github.com/mcgov/asan_alignment_example)).\n"
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"\n"
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"## References\n"
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"\n"
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"- [Manual ASAN poisoning and alignment](https://github.com/mcgov/asan_alignment_example) example by `mcgov`\n"
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"- [Address Sanitizer: A Fast Address Sanity Checker](https://static.googleusercontent.com/media/research.google.com/en/pubs/archive/37752.pdf)\n"
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"- [sanitizer/asan_interface.h](https://github.com/llvm-mirror/compiler-rt/blob/master/include/sanitizer/asan_interface.h)\n"
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"\n"
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"## Raw Test Results\n"
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"\n"
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"Here we poison a sliding window of 7 bytes to demonstrate that ASAN\n"
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"poisoning will only poison the byte region if the region meets an 8\n"
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"byte aligned address. It will only poison bytes up to the boundary,\n"
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"any bytes that straddle the boundary that do not hit the next 8 byte\n"
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"boundary are not poisoned.\n"
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"\n");
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uint32_t const ASAN_ALIGNMENT = 8;
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uint32_t const REGION_WINDOW = 7;
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char array[16] = {};
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printf("```\n");
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for (size_t poison_index = 0; poison_index < sizeof(array) - (REGION_WINDOW - 1); poison_index++) {
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assert(IsPowerOfTwo(array, ASAN_ALIGNMENT));
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// NOTE: Print byte array ==================================================================
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PrintByteArray(array, sizeof(array));
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// NOTE: Poison the array ==================================================================
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__asan_poison_memory_region(&array[poison_index], REGION_WINDOW);
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PrintPoisonMemoryRegion(1 /*step*/, array, sizeof(array), poison_index, poison_index + (REGION_WINDOW - 1));
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// NOTE: Print the poison-ed bytes =========================================================
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PrintPoisonedBytes(2 /*step*/, array, sizeof(array));
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// NOTE: Cleanup ===========================================================================
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__asan_unpoison_memory_region(array, sizeof(array));
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printf("\n");
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}
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printf("```\n");
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printf(
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"Now we demonstrate that unpoisoning 1 byte in the 8 byte window\n"
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"will unpoison all bytes prior to it up until the previous 8 byte \n"
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"boundary.\n"
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"\n");
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printf("```\n");
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for (size_t unpoison_index = 0; unpoison_index < sizeof(array); unpoison_index++) {
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assert(IsPowerOfTwo(array, ASAN_ALIGNMENT));
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// NOTE: Print byte array ==================================================================
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PrintByteArray(array, sizeof(array));
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// NOTE: Poison the array ==================================================================
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__asan_poison_memory_region(array, sizeof(array));
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PrintPoisonMemoryRegion(1 /*step*/, array, sizeof(array), 0, sizeof(array) - 1);
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// NOTE: Print the poison-ed bytes =========================================================
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PrintPoisonedBytes(2 /*step*/, array, sizeof(array));
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// NOTE: Unpoison byte at each position separately =========================================
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printf("3. __asan_unpoison_memory_region ");
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__asan_unpoison_memory_region(array + unpoison_index, 1);
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for (size_t index = 0 ; index < sizeof(array); index++) {
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PrintByteSpacing(" ");
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printf("%c", index == unpoison_index ? 'x' : ' ');
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}
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printf("\n");
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// NOTE: Print the poison-ed bytes =========================================================
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printf("4. __asan_address_is_poisoned ");
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for (size_t index = 0 ; index < sizeof(array); index++) {
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PrintByteSpacing(" ");
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printf("%c", __asan_address_is_poisoned(array + index) ? 'x' : ' ');
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}
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printf("\n\n");
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// NOTE: Cleanup ===========================================================================
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__asan_unpoison_memory_region(array, sizeof(array));
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}
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printf("```\n");
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printf(
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"Unpoisoning across 8 byte boundaries may lead to undesired\n"
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"behaviour, with all bytes on the left side of the boundary being\n"
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"unpoisoned\n\n");
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printf("```\n");
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{
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// NOTE: Print byte array ==================================================================
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char array[16] = {};
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PrintByteArray(array, sizeof(array));
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// NOTE: Poison the array ==================================================================
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__asan_poison_memory_region(array, sizeof(array));
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PrintPoisonMemoryRegion(1 /*step*/, array, sizeof(array), 0, sizeof(array) - 1);
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// NOTE: Print the poison-ed bytes =========================================================
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PrintPoisonedBytes(2 /*step*/, array, sizeof(array));
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// NOTE: Unpoison across the 8 byte boundary ===============================================
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printf("3. __asan_unpoison_memory_region ");
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uint32_t const start_poison_index = 7;
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uint32_t const bytes_to_unpoison = 2;
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uint32_t const end_poison_index = start_poison_index + (bytes_to_unpoison - 1);
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__asan_unpoison_memory_region(array + start_poison_index, bytes_to_unpoison);
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for (size_t index = 0 ; index < sizeof(array); index++) {
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PrintByteSpacing(" ");
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printf("%c", index >= start_poison_index && index <= end_poison_index ? 'x' : ' ');
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}
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printf("\n");
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// NOTE: Print the poison-ed bytes =========================================================
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PrintPoisonedBytes(4 /*step*/, array, sizeof(array));
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}
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printf("```\n");
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return 0;
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}
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8
build.bat
Normal file
8
build.bat
Normal file
@ -0,0 +1,8 @@
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@echo off
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set script_dir_backslash=%~dp0
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set script_dir=%script_dir_backslash:~0,-1%
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|
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if not exist %script_dir%\Build mkdir %script_dir%\Build
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pushd %script_dir%\Build
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cl %script_dir%\asan_example.cpp -Zi -fsanitize=address -nologo -link || exit /b 1
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popd
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9
build.sh
Normal file
9
build.sh
Normal file
@ -0,0 +1,9 @@
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#!/bin/bash
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script_dir=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
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mkdir -p ${script_dir}/Build
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pushd ${script_dir}/Build
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gcc ${script_dir}/asan_example.cpp -g -fsanitize=address -o asan_example
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popd
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220
readme.md
Normal file
220
readme.md
Normal file
@ -0,0 +1,220 @@
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# ASAN Manual Poisoning
|
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|
||||
## TLDR
|
||||
|
||||
`__asan_poison_memory_region(ptr, size)`
|
||||
|
||||
Poisons the byte region `[ptr, AlignDown(ptr+size, 8))`
|
||||
|
||||
`__asan_unpoison_memory_region(ptr, size)`
|
||||
|
||||
Unpoisons the byte region `[AlignDown(ptr, 8), ptr+size)`
|
||||
|
||||
Use the provided macros that are conditionally enabled if ASAN is
|
||||
defined from `<sanitizer/asan_interface.h>`.
|
||||
|
||||
```
|
||||
ASAN_POISON_MEMORY_REGION(addr, size)
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ASAN_UNPOISON_MEMORY_REGION(addr, size)
|
||||
```
|
||||
|
||||
If in doubt, use `__asan_address_is_poisoned` to sanity check the
|
||||
ranges requested to be un/poisoned to avoid potential gaps in
|
||||
marked-up memory that may lead to undetected read/writes.
|
||||
|
||||
## Overview
|
||||
|
||||
ASAN provides a way to manually markup ranges of bytes to
|
||||
prohibit or permit reads to those addresses. There's a short
|
||||
foot-note in Google's [AddressSanitizerManualPoisoning](https://github.com/google/sanitizers/wiki/AddressSanitizerManualPoisoning)
|
||||
documentation that states:
|
||||
|
||||
```
|
||||
If you have a custom allocation arena, the typical workflow would be
|
||||
to poison the entire arena first, and then unpoison allocated chunks
|
||||
of memory leaving poisoned redzones between them. The allocated
|
||||
chunks should start with 8-aligned addresses.
|
||||
```
|
||||
|
||||
This repository runs some simple tests to clarify the behaviour of
|
||||
the API on un/aligned addresses at various sizes without having
|
||||
to dig into source code or read the [ASAN paper](https://static.googleusercontent.com/media/research.google.com/en/pubs/archive/37752.pdf).
|
||||
|
||||
We use a stack-allocated 16 byte array and test un/poisoning
|
||||
various ranges of bytes from different alignments to clarify the
|
||||
poisoning behaviour of the API.
|
||||
|
||||
This reveals that calling the API haphazardly, unaligned or
|
||||
straddling boundaries can lead to gaps in poisoned memory and hide
|
||||
potential leaks (as also demonstrated in [Manual ASAN poisoning and
|
||||
alignment](https://github.com/mcgov/asan_alignment_example) example
|
||||
by `mcgov`.
|
||||
|
||||
## References
|
||||
|
||||
- [Manual ASAN poisoning and alignment](https://github.com/mcgov/asan_alignment_example) example by `mcgov`
|
||||
- [Address Sanitizer: A Fast Address Sanity Checker](https://static.googleusercontent.com/media/research.google.com/en/pubs/archive/37752.pdf)
|
||||
- [sanitizer/asan_interface.h](https://github.com/llvm-mirror/compiler-rt/blob/master/include/sanitizer/asan_interface.h)
|
||||
|
||||
## Raw Test Results
|
||||
Here we demonstrate that ASAN poison-ing will only poison the
|
||||
byte region if the region meets an 8 byte boundary. It will only
|
||||
poison bytes upto the 8 byte boundary, any bytes that straddle
|
||||
the boundary that do not hit the next 8 byte boundary are not
|
||||
poison-ed.
|
||||
|
||||
```
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x |
|
||||
2. __asan_address_is_poisoned |
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x |
|
||||
2. __asan_address_is_poisoned x x x x x x x |
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x | x
|
||||
2. __asan_address_is_poisoned x x x x x x |
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x | x x
|
||||
2. __asan_address_is_poisoned x x x x x |
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x | x x x
|
||||
2. __asan_address_is_poisoned x x x x |
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x | x x x x
|
||||
2. __asan_address_is_poisoned x x x |
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x | x x x x x
|
||||
2. __asan_address_is_poisoned x x |
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x | x x x x x x
|
||||
2. __asan_address_is_poisoned x |
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region | x x x x x x x
|
||||
2. __asan_address_is_poisoned |
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region | x x x x x x x
|
||||
2. __asan_address_is_poisoned | x x x x x x x
|
||||
|
||||
```
|
||||
Now we demonstrate that unpoisoning 1 byte in the 8 byte window
|
||||
will unpoison all bytes prior to it up until the previous 8 byte
|
||||
boundary.
|
||||
|
||||
```
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region x |
|
||||
4. __asan_address_is_poisoned x x x x x x x | x x x x x x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region x |
|
||||
4. __asan_address_is_poisoned x x x x x x | x x x x x x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region x |
|
||||
4. __asan_address_is_poisoned x x x x x | x x x x x x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region x |
|
||||
4. __asan_address_is_poisoned x x x x | x x x x x x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region x |
|
||||
4. __asan_address_is_poisoned x x x | x x x x x x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region x |
|
||||
4. __asan_address_is_poisoned x x | x x x x x x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region x |
|
||||
4. __asan_address_is_poisoned x | x x x x x x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region x |
|
||||
4. __asan_address_is_poisoned | x x x x x x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region | x
|
||||
4. __asan_address_is_poisoned x x x x x x x x | x x x x x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region | x
|
||||
4. __asan_address_is_poisoned x x x x x x x x | x x x x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region | x
|
||||
4. __asan_address_is_poisoned x x x x x x x x | x x x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region | x
|
||||
4. __asan_address_is_poisoned x x x x x x x x | x x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region | x
|
||||
4. __asan_address_is_poisoned x x x x x x x x | x x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region | x
|
||||
4. __asan_address_is_poisoned x x x x x x x x | x x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region | x
|
||||
4. __asan_address_is_poisoned x x x x x x x x | x
|
||||
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region | x
|
||||
4. __asan_address_is_poisoned x x x x x x x x |
|
||||
|
||||
```
|
||||
Unpoisoning across 8 byte boundaries may lead to undesired
|
||||
behaviour, with all bytes on the left side of the boundary being
|
||||
unpoisoned
|
||||
|
||||
```
|
||||
Byte Array 00 01 02 03 04 05 06 07 | 08 09 10 11 12 13 14 15
|
||||
1. __asan_poison_memory_region x x x x x x x x | x x x x x x x x
|
||||
2. __asan_address_is_poisoned x x x x x x x x | x x x x x x x x
|
||||
3. __asan_unpoison_memory_region x | x
|
||||
4. __asan_address_is_poisoned | x x x x x x x
|
||||
```
|
||||
Loading…
Reference in New Issue
Block a user