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Diffstat (limited to 'utils/libdislocator/libdislocator.so.c')
| -rw-r--r-- | utils/libdislocator/libdislocator.so.c | 572 |
1 files changed, 572 insertions, 0 deletions
diff --git a/utils/libdislocator/libdislocator.so.c b/utils/libdislocator/libdislocator.so.c new file mode 100644 index 00000000..bd08a678 --- /dev/null +++ b/utils/libdislocator/libdislocator.so.c @@ -0,0 +1,572 @@ +/* + + american fuzzy lop++ - dislocator, an abusive allocator + ----------------------------------------------------- + + Originally written by Michal Zalewski + + Copyright 2016 Google Inc. All rights reserved. + Copyright 2019-2022 AFLplusplus Project. All rights reserved. + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at: + + http://www.apache.org/licenses/LICENSE-2.0 + + This is a companion library that can be used as a drop-in replacement + for the libc allocator in the fuzzed binaries. See README.dislocator.md for + more info. + + */ + +#define _GNU_SOURCE +#include <stdio.h> +#include <stdlib.h> +#include <stddef.h> +#include <string.h> +#include <limits.h> +#include <errno.h> +#include <sys/mman.h> + +#ifdef __APPLE__ + #include <mach/vm_statistics.h> +#endif + +#ifdef __FreeBSD__ + #include <sys/param.h> +#endif + +#if (defined(__linux__) && !defined(__ANDROID__)) || defined(__HAIKU__) + #include <unistd.h> + #include <sys/prctl.h> + #ifdef __linux__ + #include <sys/syscall.h> + #include <malloc.h> + #endif + #ifdef __NR_getrandom + #define arc4random_buf(p, l) \ + do { \ + \ + ssize_t rd = syscall(__NR_getrandom, p, l, 0); \ + if (rd != l) DEBUGF("getrandom failed"); \ + \ + } while (0) + + #else + #include <time.h> + #define arc4random_buf(p, l) \ + do { \ + \ + srand(time(NULL)); \ + u32 i; \ + u8 *ptr = (u8 *)p; \ + for (i = 0; i < l; i++) \ + ptr[i] = rand() % INT_MAX; \ + \ + } while (0) + + #endif + #ifndef PR_SET_VMA + #define PR_SET_VMA 0x53564d41 + #define PR_SET_VMA_ANON_NAME 0 + #endif +#endif + +#include "config.h" +#include "types.h" + +#if __STDC_VERSION__ < 201112L || \ + (defined(__FreeBSD__) && __FreeBSD_version < 1200000) +// use this hack if not C11 +typedef struct { + + long long __ll; + long double __ld; + +} max_align_t; + +#endif + +#define ALLOC_ALIGN_SIZE (_Alignof(max_align_t)) + +#ifndef PAGE_SIZE + #define PAGE_SIZE 4096 +#endif /* !PAGE_SIZE */ + +#ifndef MAP_ANONYMOUS + #define MAP_ANONYMOUS MAP_ANON +#endif /* !MAP_ANONYMOUS */ + +#define SUPER_PAGE_SIZE 1 << 21 + +/* Error / message handling: */ + +#define DEBUGF(_x...) \ + do { \ + \ + if (alloc_verbose) { \ + \ + if (++call_depth == 1) { \ + \ + fprintf(stderr, "[AFL] " _x); \ + fprintf(stderr, "\n"); \ + \ + } \ + call_depth--; \ + \ + } \ + \ + } while (0) + +#define FATAL(_x...) \ + do { \ + \ + if (++call_depth == 1) { \ + \ + fprintf(stderr, "*** [AFL] " _x); \ + fprintf(stderr, " ***\n"); \ + abort(); \ + \ + } \ + call_depth--; \ + \ + } while (0) + +/* Macro to count the number of pages needed to store a buffer: */ + +#define PG_COUNT(_l) (((_l) + (PAGE_SIZE - 1)) / PAGE_SIZE) + +/* Canary & clobber bytes: */ + +#define ALLOC_CANARY 0xAACCAACC +#define ALLOC_CLOBBER 0xCC + +#define TAIL_ALLOC_CANARY 0xAC + +#define PTR_C(_p) (((u32 *)(_p))[-1]) +#define PTR_L(_p) (((u32 *)(_p))[-2]) + +/* Configurable stuff (use AFL_LD_* to set): */ + +static size_t max_mem = MAX_ALLOC; /* Max heap usage to permit */ +static u8 alloc_verbose, /* Additional debug messages */ + hard_fail, /* abort() when max_mem exceeded? */ + no_calloc_over, /* abort() on calloc() overflows? */ + align_allocations; /* Force alignment to sizeof(void*) */ + +#if defined __OpenBSD__ || defined __APPLE__ + #define __thread + #warning no thread support available +#endif +static _Atomic size_t total_mem; /* Currently allocated mem */ + +static __thread u32 call_depth; /* To avoid recursion via fprintf() */ +static u32 alloc_canary; + +/* This is the main alloc function. It allocates one page more than necessary, + sets that tailing page to PROT_NONE, and then increments the return address + so that it is right-aligned to that boundary. Since it always uses mmap(), + the returned memory will be zeroed. */ + +static void *__dislocator_alloc(size_t len) { + + u8 * ret, *base; + size_t tlen; + int flags, protflags, fd, sp; + + if (total_mem + len > max_mem || total_mem + len < total_mem) { + + if (hard_fail) FATAL("total allocs exceed %zu MB", max_mem / 1024 / 1024); + + DEBUGF("total allocs exceed %zu MB, returning NULL", max_mem / 1024 / 1024); + + return NULL; + + } + + size_t rlen; + if (align_allocations && (len & (ALLOC_ALIGN_SIZE - 1))) + rlen = (len & ~(ALLOC_ALIGN_SIZE - 1)) + ALLOC_ALIGN_SIZE; + else + rlen = len; + + /* We will also store buffer length and a canary below the actual buffer, so + let's add 8 bytes for that. */ + + base = NULL; + tlen = (1 + PG_COUNT(rlen + 8)) * PAGE_SIZE; + protflags = PROT_READ | PROT_WRITE; + flags = MAP_PRIVATE | MAP_ANONYMOUS; + fd = -1; +#if defined(PROT_MAX) + // apply when sysctl vm.imply_prot_max is set to 1 + // no-op otherwise + protflags |= PROT_MAX(PROT_READ | PROT_WRITE); +#endif +#if defined(USEHUGEPAGE) + sp = (rlen >= SUPER_PAGE_SIZE && !(rlen % SUPER_PAGE_SIZE)); + + #if defined(__APPLE__) + if (sp) fd = VM_FLAGS_SUPERPAGE_SIZE_2MB; + #elif defined(__linux__) + if (sp) flags |= MAP_HUGETLB; + #elif defined(__FreeBSD__) + if (sp) flags |= MAP_ALIGNED_SUPER; + #elif defined(__sun) + if (sp) { + + base = (void *)(caddr_t)(1 << 21); + flags |= MAP_ALIGN; + + } + + #endif +#else + (void)sp; +#endif + + ret = (u8 *)mmap(base, tlen, protflags, flags, fd, 0); +#if defined(USEHUGEPAGE) + /* We try one more time with regular call */ + if (ret == MAP_FAILED) { + + #if defined(__APPLE__) + fd = -1; + #elif defined(__linux__) + flags &= -MAP_HUGETLB; + #elif defined(__FreeBSD__) + flags &= -MAP_ALIGNED_SUPER; + #elif defined(__sun) + flags &= -MAP_ALIGN; + #endif + ret = (u8 *)mmap(NULL, tlen, protflags, flags, fd, 0); + + } + +#endif + + if (ret == MAP_FAILED) { + + if (hard_fail) FATAL("mmap() failed on alloc (OOM?)"); + + DEBUGF("mmap() failed on alloc (OOM?)"); + + return NULL; + + } + +#if defined(USENAMEDPAGE) + #if defined(__linux__) + // in the /proc/<pid>/maps file, the anonymous page appears as + // `<start>-<end> ---p 00000000 00:00 0 [anon:libdislocator]` + if (prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, (unsigned long)ret, tlen, + (unsigned long)"libdislocator") < 0) { + + DEBUGF("prctl() failed"); + + } + + #endif +#endif + + /* Set PROT_NONE on the last page. */ + + if (mprotect(ret + PG_COUNT(rlen + 8) * PAGE_SIZE, PAGE_SIZE, PROT_NONE)) + FATAL("mprotect() failed when allocating memory"); + + /* Offset the return pointer so that it's right-aligned to the page + boundary. */ + + ret += PAGE_SIZE * PG_COUNT(rlen + 8) - rlen - 8; + + /* Store allocation metadata. */ + + ret += 8; + + PTR_L(ret) = len; + PTR_C(ret) = alloc_canary; + + total_mem += len; + + if (rlen != len) { + + size_t i; + for (i = len; i < rlen; ++i) + ret[i] = TAIL_ALLOC_CANARY; + + } + + return ret; + +} + +/* The "user-facing" wrapper for calloc(). This just checks for overflows and + displays debug messages if requested. */ + +void *calloc(size_t elem_len, size_t elem_cnt) { + + void *ret; + + size_t len = elem_len * elem_cnt; + + /* Perform some sanity checks to detect obvious issues... */ + + if (elem_cnt && len / elem_cnt != elem_len) { + + if (no_calloc_over) { + + DEBUGF("calloc(%zu, %zu) would overflow, returning NULL", elem_len, + elem_cnt); + return NULL; + + } + + FATAL("calloc(%zu, %zu) would overflow", elem_len, elem_cnt); + + } + + ret = __dislocator_alloc(len); + + DEBUGF("calloc(%zu, %zu) = %p [%zu total]", elem_len, elem_cnt, ret, + total_mem); + + return ret; + +} + +/* The wrapper for malloc(). Roughly the same, also clobbers the returned + memory (unlike calloc(), malloc() is not guaranteed to return zeroed + memory). */ + +void *malloc(size_t len) { + + void *ret; + + ret = __dislocator_alloc(len); + + DEBUGF("malloc(%zu) = %p [%zu total]", len, ret, total_mem); + + if (ret && len) memset(ret, ALLOC_CLOBBER, len); + + return ret; + +} + +/* The wrapper for free(). This simply marks the entire region as PROT_NONE. + If the region is already freed, the code will segfault during the attempt to + read the canary. Not very graceful, but works, right? */ + +void free(void *ptr) { + + u32 len; + + DEBUGF("free(%p)", ptr); + + if (!ptr) return; + + if (PTR_C(ptr) != alloc_canary) FATAL("bad allocator canary on free()"); + + len = PTR_L(ptr); + + total_mem -= len; + u8 *ptr_ = ptr; + + if (align_allocations && (len & (ALLOC_ALIGN_SIZE - 1))) { + + size_t rlen = (len & ~(ALLOC_ALIGN_SIZE - 1)) + ALLOC_ALIGN_SIZE; + for (; len < rlen; ++len) + if (ptr_[len] != TAIL_ALLOC_CANARY) + FATAL("bad tail allocator canary on free()"); + + } + + /* Protect everything. Note that the extra page at the end is already + set as PROT_NONE, so we don't need to touch that. */ + + ptr_ -= PAGE_SIZE * PG_COUNT(len + 8) - len - 8; + + if (mprotect(ptr_ - 8, PG_COUNT(len + 8) * PAGE_SIZE, PROT_NONE)) + FATAL("mprotect() failed when freeing memory"); + + ptr = ptr_; + + /* Keep the mapping; this is wasteful, but prevents ptr reuse. */ + +} + +/* Realloc is pretty straightforward, too. We forcibly reallocate the buffer, + move data, and then free (aka mprotect()) the original one. */ + +void *realloc(void *ptr, size_t len) { + + void *ret; + + ret = malloc(len); + + if (ret && ptr) { + + if (PTR_C(ptr) != alloc_canary) FATAL("bad allocator canary on realloc()"); + // Here the tail canary check is delayed to free() + + memcpy(ret, ptr, MIN(len, PTR_L(ptr))); + free(ptr); + + } + + DEBUGF("realloc(%p, %zu) = %p [%zu total]", ptr, len, ret, total_mem); + + return ret; + +} + +/* posix_memalign we mainly check the proper alignment argument + if the requested size fits within the alignment we do + a normal request */ + +int posix_memalign(void **ptr, size_t align, size_t len) { + + // if (*ptr == NULL) return EINVAL; // (andrea) Why? I comment it out for now + if ((align % 2) || (align % sizeof(void *))) return EINVAL; + if (len == 0) { + + *ptr = NULL; + return 0; + + } + + size_t rem = len % align; + if (rem) len += align - rem; + + *ptr = __dislocator_alloc(len); + + if (*ptr && len) memset(*ptr, ALLOC_CLOBBER, len); + + DEBUGF("posix_memalign(%p %zu, %zu) [*ptr = %p]", ptr, align, len, *ptr); + + return 0; + +} + +/* just the non-posix fashion */ + +void *memalign(size_t align, size_t len) { + + void *ret = NULL; + + if (posix_memalign(&ret, align, len)) { + + DEBUGF("memalign(%zu, %zu) failed", align, len); + + } + + return ret; + +} + +/* sort of C11 alias of memalign only more severe, alignment-wise */ + +void *aligned_alloc(size_t align, size_t len) { + + void *ret = NULL; + + if ((len % align)) return NULL; + + if (posix_memalign(&ret, align, len)) { + + DEBUGF("aligned_alloc(%zu, %zu) failed", align, len); + + } + + return ret; + +} + +/* specific BSD api mainly checking possible overflow for the size */ + +void *reallocarray(void *ptr, size_t elem_len, size_t elem_cnt) { + + const size_t elem_lim = 1UL << (sizeof(size_t) * 4); + const size_t elem_tot = elem_len * elem_cnt; + void * ret = NULL; + + if ((elem_len >= elem_lim || elem_cnt >= elem_lim) && elem_len > 0 && + elem_cnt > (SIZE_MAX / elem_len)) { + + DEBUGF("reallocarray size overflow (%zu)", elem_tot); + + } else { + + ret = realloc(ptr, elem_tot); + + } + + return ret; + +} + +#if !defined(__ANDROID__) +size_t malloc_usable_size(void *ptr) { + +#else +size_t malloc_usable_size(const void *ptr) { + +#endif + + return ptr ? PTR_L(ptr) : 0; + +} + +__attribute__((constructor)) void __dislocator_init(void) { + + char *tmp = getenv("AFL_LD_LIMIT_MB"); + + if (tmp) { + + char * tok; + unsigned long long mmem = strtoull(tmp, &tok, 10); + if (*tok != '\0' || errno == ERANGE || mmem > SIZE_MAX / 1024 / 1024) + FATAL("Bad value for AFL_LD_LIMIT_MB"); + max_mem = mmem * 1024 * 1024; + + } + + alloc_canary = ALLOC_CANARY; + tmp = getenv("AFL_RANDOM_ALLOC_CANARY"); + + if (tmp) arc4random_buf(&alloc_canary, sizeof(alloc_canary)); + + alloc_verbose = !!getenv("AFL_LD_VERBOSE"); + hard_fail = !!getenv("AFL_LD_HARD_FAIL"); + no_calloc_over = !!getenv("AFL_LD_NO_CALLOC_OVER"); + align_allocations = !!getenv("AFL_ALIGNED_ALLOC"); + +} + +/* NetBSD fault handler specific api subset */ + +void (*esetfunc(void (*fn)(int, const char *, ...)))(int, const char *, ...) { + + /* Might not be meaningful to implement; upper calls already report errors */ + return NULL; + +} + +void *emalloc(size_t len) { + + return malloc(len); + +} + +void *ecalloc(size_t elem_len, size_t elem_cnt) { + + return calloc(elem_len, elem_cnt); + +} + +void *erealloc(void *ptr, size_t len) { + + return realloc(ptr, len); + +} + |