Generate the readme from the example
This commit is contained in:
parent
591956471e
commit
1f5070f456
103
asan_example.cpp
103
asan_example.cpp
@ -1,10 +1,9 @@
|
||||
|
||||
#define WIN32_MEAN_AND_LEAN
|
||||
#include <Windows.h>
|
||||
#include <sanitizer/asan_interface.h>
|
||||
#include <stdint.h>
|
||||
#include <stdio.h>
|
||||
#include <assert.h>
|
||||
#include <sanitizer/asan_interface.h>
|
||||
#include <string.h>
|
||||
|
||||
#define IsPowerOfTwo(value, pot) ((((size_t)value) & (((size_t)pot) - 1)) == 0)
|
||||
#define AsanAlignment 8
|
||||
@ -57,15 +56,81 @@ static void PrintPoisonMemoryRegion(int step, char const *array, size_t array_si
|
||||
|
||||
int main()
|
||||
{
|
||||
printf("Here we demonstrate that ASAN poison-ing will only poison the\n"
|
||||
"byte region if the region meets an 8 byte boundary. It will only\n"
|
||||
"poison bytes upto the 8 byte boundary, any bytes that straddle\n"
|
||||
"the boundary that do not hit the next 8 byte boundary are not\n"
|
||||
"poison-ed.\n\n");
|
||||
printf(
|
||||
"# ASAN Manual Poisoning\n"
|
||||
"\n"
|
||||
"## TLDR\n"
|
||||
"\n"
|
||||
"`__asan_poison_memory_region(ptr, size)`\n"
|
||||
"\n"
|
||||
"Poisons the byte region `[ptr, AlignDown(ptr+size, 8))`\n"
|
||||
"\n"
|
||||
"`__asan_unpoison_memory_region(ptr, size)`\n"
|
||||
"\n"
|
||||
"Unpoisons the byte region `[AlignDown(ptr, 8), ptr+size)`\n"
|
||||
"\n"
|
||||
"Use the provided macros that are conditionally enabled if ASAN is\n"
|
||||
"defined from `<sanitizer/asan_interface.h>`.\n"
|
||||
"\n"
|
||||
"```\n"
|
||||
"ASAN_POISON_MEMORY_REGION(addr, size)\n"
|
||||
"ASAN_UNPOISON_MEMORY_REGION(addr, size)\n"
|
||||
"```\n"
|
||||
"\n"
|
||||
"If in doubt, use `__asan_address_is_poisoned` to sanity check the\n"
|
||||
"ranges requested to be un/poisoned to avoid potential gaps in\n"
|
||||
"marked-up memory that may lead to undetected read/writes.\n"
|
||||
"\n"
|
||||
"## Overview\n"
|
||||
"\n"
|
||||
"ASAN provides a way to manually markup ranges of bytes to\n"
|
||||
"prohibit or permit reads to those addresses. There's a short\n"
|
||||
"foot-note in Google's "
|
||||
"[AddressSanitizerManualPoisoning](https://github.com/google/"
|
||||
"sanitizers/wiki/AddressSanitizerManualPoisoning)\n"
|
||||
"documentation that states:\n"
|
||||
"\n"
|
||||
"```\n"
|
||||
"If you have a custom allocation arena, the typical workflow would be\n"
|
||||
"to poison the entire arena first, and then unpoison allocated chunks\n"
|
||||
"of memory leaving poisoned redzones between them. The allocated\n"
|
||||
"chunks should start with 8-aligned addresses.\n"
|
||||
"```\n"
|
||||
"\n"
|
||||
"This repository runs some simple tests to clarify the behaviour of\n"
|
||||
"the API on un/aligned addresses at various sizes without having\n"
|
||||
"to dig into source code or read the [ASAN paper](https://static."
|
||||
"googleusercontent.com/media/research.google.com/en/pubs/archive/"
|
||||
"37752.pdf).\n"
|
||||
"\n"
|
||||
"We use a stack-allocated 16 byte array and test un/poisoning\n"
|
||||
"various ranges of bytes from different alignments to clarify the\n"
|
||||
"poisoning behaviour of the API.\n"
|
||||
"\n"
|
||||
"This reveals that calling the API haphazardly, unaligned or\n"
|
||||
"straddling boundaries can lead to gaps in poisoned memory and hide\n"
|
||||
"potential leaks (as also demonstrated in [Manual ASAN poisoning and\n"
|
||||
"alignment](https://github.com/mcgov/asan_alignment_example)).\n"
|
||||
"\n"
|
||||
"## References\n"
|
||||
"\n"
|
||||
"- [Manual ASAN poisoning and alignment](https://github.com/mcgov/asan_alignment_example) example by `mcgov`\n"
|
||||
"- [Address Sanitizer: A Fast Address Sanity Checker](https://static.googleusercontent.com/media/research.google.com/en/pubs/archive/37752.pdf)\n"
|
||||
"- [sanitizer/asan_interface.h](https://github.com/llvm-mirror/compiler-rt/blob/master/include/sanitizer/asan_interface.h)\n"
|
||||
"\n"
|
||||
"## Raw Test Results\n"
|
||||
"Here we demonstrate that ASAN poison-ing will only poison the\n"
|
||||
"byte region if the region meets an 8 byte boundary. It will only\n"
|
||||
"poison bytes upto the 8 byte boundary, any bytes that straddle\n"
|
||||
"the boundary that do not hit the next 8 byte boundary are not\n"
|
||||
"poison-ed.\n"
|
||||
"\n");
|
||||
|
||||
uint32_t const ASAN_ALIGNMENT = 8;
|
||||
uint32_t const REGION_WINDOW = 7;
|
||||
char array[16] = {};
|
||||
|
||||
printf("```\n");
|
||||
for (size_t poison_index = 0; poison_index < sizeof(array) - (REGION_WINDOW - 1); poison_index++) {
|
||||
assert(IsPowerOfTwo(array, ASAN_ALIGNMENT));
|
||||
|
||||
@ -87,12 +152,15 @@ int main()
|
||||
__asan_unpoison_memory_region(array, sizeof(array));
|
||||
printf("\n");
|
||||
}
|
||||
printf("```\n");
|
||||
|
||||
printf(
|
||||
"Now we demonstrate that unpoison-ing 1 byte in the 8 byte window\n"
|
||||
"will unpoison all bytes prior to it up until the start of the window\n"
|
||||
"until the previous 8 byte boundary.\n\n");
|
||||
"Now we demonstrate that unpoisoning 1 byte in the 8 byte window\n"
|
||||
"will unpoison all bytes prior to it up until the previous 8 byte \n"
|
||||
"boundary.\n"
|
||||
"\n");
|
||||
|
||||
printf("```\n");
|
||||
for (size_t unpoison_index = 0; unpoison_index < sizeof(array); unpoison_index++) {
|
||||
assert(IsPowerOfTwo(array, ASAN_ALIGNMENT));
|
||||
|
||||
@ -133,11 +201,14 @@ int main()
|
||||
|
||||
__asan_unpoison_memory_region(array, sizeof(array));
|
||||
}
|
||||
printf("```\n");
|
||||
|
||||
printf(
|
||||
"Unpoison-ing across 8 byte boundaries may lead to undesired\n"
|
||||
"Unpoisoning across 8 byte boundaries may lead to undesired\n"
|
||||
"behaviour, with all bytes on the left side of the boundary being\n"
|
||||
"unpoisoned\n\n");
|
||||
|
||||
printf("```\n");
|
||||
{
|
||||
// NOTE: Print byte array ==================================================================
|
||||
|
||||
@ -171,12 +242,6 @@ int main()
|
||||
|
||||
PrintPoisonedBytes(4 /*step*/, array, sizeof(array));
|
||||
}
|
||||
|
||||
printf("\n\nTLDR:\n"
|
||||
" __asan_poison_memory_region(ptr, size)\n"
|
||||
" Poisons the byte region [ptr, AlignDown(ptr+size, 8))\n\n"
|
||||
" __asan_unpoison_memory_region(ptr, size)\n"
|
||||
" Unpoisons the byte region [AlignDown(ptr, 8), ptr+size)\n\n"
|
||||
);
|
||||
printf("```\n");
|
||||
return 0;
|
||||
}
|
||||
|
||||
220
readme.md
Normal file
220
readme.md
Normal file
@ -0,0 +1,220 @@
|
||||
# ASAN Manual Poisoning
|
||||
|
||||
## 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)
|
||||
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