/* american fuzzy lop++ - LLVM instrumentation bootstrap --------------------------------------------------- Written by Laszlo Szekeres and Michal Zalewski LLVM integration design comes from Laszlo Szekeres. Copyright 2015, 2016 Google Inc. All rights reserved. Copyright 2019-2020 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 code is the rewrite of afl-as.h's main_payload. */ #ifdef __ANDROID__ #include "android-ashmem.h" #endif #include "config.h" #include "types.h" #include "cmplog.h" #include "llvm-ngram-coverage.h" #include #include #include #include #include #include #include #include #include #include #include #include /* This is a somewhat ugly hack for the experimental 'trace-pc-guard' mode. Basically, we need to make sure that the forkserver is initialized after the LLVM-generated runtime initialization pass, not before. */ #ifdef USE_TRACE_PC #define CONST_PRIO 5 #else #define CONST_PRIO 0 #endif /* ^USE_TRACE_PC */ #include #include /* Globals needed by the injected instrumentation. The __afl_area_initial region is used for instrumentation output before __afl_map_shm() has a chance to run. It will end up as .comm, so it shouldn't be too wasteful. */ u8 __afl_area_initial[MAP_SIZE]; u8 *__afl_area_ptr = __afl_area_initial; #ifdef __ANDROID__ PREV_LOC_T __afl_prev_loc[NGRAM_SIZE_MAX]; u32 __afl_final_loc; #else __thread PREV_LOC_T __afl_prev_loc[NGRAM_SIZE_MAX]; __thread u32 __afl_final_loc; #endif struct cmp_map *__afl_cmp_map; __thread u32 __afl_cmp_counter; /* Running in persistent mode? */ static u8 is_persistent; /* SHM setup. */ static void __afl_map_shm(void) { u8 *id_str = getenv(SHM_ENV_VAR); /* If we're running under AFL, attach to the appropriate region, replacing the early-stage __afl_area_initial region that is needed to allow some really hacky .init code to work correctly in projects such as OpenSSL. */ if (id_str) { #ifdef USEMMAP const char * shm_file_path = id_str; int shm_fd = -1; unsigned char *shm_base = NULL; /* create the shared memory segment as if it was a file */ shm_fd = shm_open(shm_file_path, O_RDWR, 0600); if (shm_fd == -1) { fprintf(stderr, "shm_open() failed\n"); exit(1); } /* map the shared memory segment to the address space of the process */ shm_base = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, shm_fd, 0); if (shm_base == MAP_FAILED) { close(shm_fd); shm_fd = -1; fprintf(stderr, "mmap() failed\n"); exit(2); } __afl_area_ptr = shm_base; #else u32 shm_id = atoi(id_str); __afl_area_ptr = shmat(shm_id, NULL, 0); #endif /* Whooooops. */ if (__afl_area_ptr == (void *)-1) _exit(1); /* Write something into the bitmap so that even with low AFL_INST_RATIO, our parent doesn't give up on us. */ __afl_area_ptr[0] = 1; } id_str = getenv(CMPLOG_SHM_ENV_VAR); if (id_str) { #ifdef USEMMAP const char * shm_file_path = id_str; int shm_fd = -1; unsigned char *shm_base = NULL; /* create the shared memory segment as if it was a file */ shm_fd = shm_open(shm_file_path, O_RDWR, 0600); if (shm_fd == -1) { fprintf(stderr, "shm_open() failed\n"); exit(1); } /* map the shared memory segment to the address space of the process */ shm_base = mmap(0, sizeof(struct cmp_map), PROT_READ | PROT_WRITE, MAP_SHARED, shm_fd, 0); if (shm_base == MAP_FAILED) { close(shm_fd); shm_fd = -1; fprintf(stderr, "mmap() failed\n"); exit(2); } __afl_cmp_map = shm_base; #else u32 shm_id = atoi(id_str); __afl_cmp_map = shmat(shm_id, NULL, 0); #endif if (__afl_cmp_map == (void *)-1) _exit(1); } } /* Fork server logic. */ static void __afl_start_forkserver(void) { static u8 tmp[4]; s32 child_pid; u8 child_stopped = 0; void (*old_sigchld_handler)(int) = 0; // = signal(SIGCHLD, SIG_DFL); /* Phone home and tell the parent that we're OK. If parent isn't there, assume we're not running in forkserver mode and just execute program. */ if (write(FORKSRV_FD + 1, tmp, 4) != 4) return; while (1) { u32 was_killed; int status; /* Wait for parent by reading from the pipe. Abort if read fails. */ if (read(FORKSRV_FD, &was_killed, 4) != 4) _exit(1); /* If we stopped the child in persistent mode, but there was a race condition and afl-fuzz already issued SIGKILL, write off the old process. */ if (child_stopped && was_killed) { child_stopped = 0; if (waitpid(child_pid, &status, 0) < 0) _exit(1); } if (!child_stopped) { /* Once woken up, create a clone of our process. */ child_pid = fork(); if (child_pid < 0) _exit(1); /* In child process: close fds, resume execution. */ if (!child_pid) { signal(SIGCHLD, old_sigchld_handler); close(FORKSRV_FD); close(FORKSRV_FD + 1); return; } } else { /* Special handling for persistent mode: if the child is alive but currently stopped, simply restart it with SIGCONT. */ kill(child_pid, SIGCONT); child_stopped = 0; } /* In parent process: write PID to pipe, then wait for child. */ if (write(FORKSRV_FD + 1, &child_pid, 4) != 4) _exit(1); if (waitpid(child_pid, &status, is_persistent ? WUNTRACED : 0) < 0) _exit(1); /* In persistent mode, the child stops itself with SIGSTOP to indicate a successful run. In this case, we want to wake it up without forking again. */ if (WIFSTOPPED(status)) child_stopped = 1; /* Relay wait status to pipe, then loop back. */ if (write(FORKSRV_FD + 1, &status, 4) != 4) _exit(1); } } /* A simplified persistent mode handler, used as explained in * llvm_mode/README.md. */ int __afl_persistent_loop(unsigned int max_cnt) { static u8 first_pass = 1; static u32 cycle_cnt; if (first_pass) { /* Make sure that every iteration of __AFL_LOOP() starts with a clean slate. On subsequent calls, the parent will take care of that, but on the first iteration, it's our job to erase any trace of whatever happened before the loop. */ if (is_persistent) { memset(__afl_area_ptr, 0, MAP_SIZE); __afl_area_ptr[0] = 1; memset(__afl_prev_loc, 0, NGRAM_SIZE_MAX * sizeof(PREV_LOC_T)); } cycle_cnt = max_cnt; first_pass = 0; return 1; } if (is_persistent) { if (--cycle_cnt) { raise(SIGSTOP); __afl_area_ptr[0] = 1; memset(__afl_prev_loc, 0, NGRAM_SIZE_MAX * sizeof(PREV_LOC_T)); return 1; } else { /* When exiting __AFL_LOOP(), make sure that the subsequent code that follows the loop is not traced. We do that by pivoting back to the dummy output region. */ __afl_area_ptr = __afl_area_initial; } } return 0; } /* This one can be called from user code when deferred forkserver mode is enabled. */ void __afl_manual_init(void) { static u8 init_done; if (!init_done) { __afl_map_shm(); __afl_start_forkserver(); init_done = 1; } } /* Proper initialization routine. */ __attribute__((constructor(CONST_PRIO))) void __afl_auto_init(void) { is_persistent = !!getenv(PERSIST_ENV_VAR); if (getenv(DEFER_ENV_VAR)) return; __afl_manual_init(); } /* The following stuff deals with supporting -fsanitize-coverage=trace-pc-guard. It remains non-operational in the traditional, plugin-backed LLVM mode. For more info about 'trace-pc-guard', see llvm_mode/README.md. The first function (__sanitizer_cov_trace_pc_guard) is called back on every edge (as opposed to every basic block). */ void __sanitizer_cov_trace_pc_guard(uint32_t *guard) { __afl_area_ptr[*guard]++; } /* Init callback. Populates instrumentation IDs. Note that we're using ID of 0 as a special value to indicate non-instrumented bits. That may still touch the bitmap, but in a fairly harmless way. */ void __sanitizer_cov_trace_pc_guard_init(uint32_t *start, uint32_t *stop) { u32 inst_ratio = 100; u8 *x; if (start == stop || *start) return; x = getenv("AFL_INST_RATIO"); if (x) inst_ratio = atoi(x); if (!inst_ratio || inst_ratio > 100) { fprintf(stderr, "[-] ERROR: Invalid AFL_INST_RATIO (must be 1-100).\n"); abort(); } /* Make sure that the first element in the range is always set - we use that to avoid duplicate calls (which can happen as an artifact of the underlying implementation in LLVM). */ *(start++) = R(MAP_SIZE - 1) + 1; while (start < stop) { if (R(100) < inst_ratio) *start = R(MAP_SIZE - 1) + 1; else *start = 0; start++; } } ///// CmpLog instrumentation void __cmplog_ins_hook1(uint8_t Arg1, uint8_t Arg2) { return; } void __cmplog_ins_hook2(uint16_t Arg1, uint16_t Arg2) { if (!__afl_cmp_map) return; uintptr_t k = (uintptr_t)__builtin_return_address(0); k = (k >> 4) ^ (k << 8); k &= CMP_MAP_W - 1; __afl_cmp_map->headers[k].type = CMP_TYPE_INS; u32 hits = __afl_cmp_map->headers[k].hits; __afl_cmp_map->headers[k].hits = hits + 1; // if (!__afl_cmp_map->headers[k].cnt) // __afl_cmp_map->headers[k].cnt = __afl_cmp_counter++; __afl_cmp_map->headers[k].shape = 1; //__afl_cmp_map->headers[k].type = CMP_TYPE_INS; hits &= CMP_MAP_H - 1; __afl_cmp_map->log[k][hits].v0 = Arg1; __afl_cmp_map->log[k][hits].v1 = Arg2; } void __cmplog_ins_hook4(uint32_t Arg1, uint32_t Arg2) { if (!__afl_cmp_map) return; uintptr_t k = (uintptr_t)__builtin_return_address(0); k = (k >> 4) ^ (k << 8); k &= CMP_MAP_W - 1; __afl_cmp_map->headers[k].type = CMP_TYPE_INS; u32 hits = __afl_cmp_map->headers[k].hits; __afl_cmp_map->headers[k].hits = hits + 1; __afl_cmp_map->headers[k].shape = 3; hits &= CMP_MAP_H - 1; __afl_cmp_map->log[k][hits].v0 = Arg1; __afl_cmp_map->log[k][hits].v1 = Arg2; } void __cmplog_ins_hook8(uint64_t Arg1, uint64_t Arg2) { if (!__afl_cmp_map) return; uintptr_t k = (uintptr_t)__builtin_return_address(0); k = (k >> 4) ^ (k << 8); k &= CMP_MAP_W - 1; __afl_cmp_map->headers[k].type = CMP_TYPE_INS; u32 hits = __afl_cmp_map->headers[k].hits; __afl_cmp_map->headers[k].hits = hits + 1; __afl_cmp_map->headers[k].shape = 7; hits &= CMP_MAP_H - 1; __afl_cmp_map->log[k][hits].v0 = Arg1; __afl_cmp_map->log[k][hits].v1 = Arg2; } #if defined(__APPLE__) #pragma weak __sanitizer_cov_trace_const_cmp1 = __cmplog_ins_hook1 #pragma weak __sanitizer_cov_trace_const_cmp2 = __cmplog_ins_hook2 #pragma weak __sanitizer_cov_trace_const_cmp4 = __cmplog_ins_hook4 #pragma weak __sanitizer_cov_trace_const_cmp8 = __cmplog_ins_hook8 #pragma weak __sanitizer_cov_trace_cmp1 = __cmplog_ins_hook1 #pragma weak __sanitizer_cov_trace_cmp2 = __cmplog_ins_hook2 #pragma weak __sanitizer_cov_trace_cmp4 = __cmplog_ins_hook4 #pragma weak __sanitizer_cov_trace_cmp8 = __cmplog_ins_hook8 #else void __sanitizer_cov_trace_const_cmp1(uint8_t Arg1, uint8_t Arg2) __attribute__((alias("__cmplog_ins_hook1"))); void __sanitizer_cov_trace_const_cmp2(uint16_t Arg1, uint16_t Arg2) __attribute__((alias("__cmplog_ins_hook2"))); void __sanitizer_cov_trace_const_cmp4(uint32_t Arg1, uint32_t Arg2) __attribute__((alias("__cmplog_ins_hook4"))); void __sanitizer_cov_trace_const_cmp8(uint64_t Arg1, uint64_t Arg2) __attribute__((alias("__cmplog_ins_hook8"))); void __sanitizer_cov_trace_cmp1(uint8_t Arg1, uint8_t Arg2) __attribute__((alias("__cmplog_ins_hook1"))); void __sanitizer_cov_trace_cmp2(uint16_t Arg1, uint16_t Arg2) __attribute__((alias("__cmplog_ins_hook2"))); void __sanitizer_cov_trace_cmp4(uint32_t Arg1, uint32_t Arg2) __attribute__((alias("__cmplog_ins_hook4"))); void __sanitizer_cov_trace_cmp8(uint64_t Arg1, uint64_t Arg2) __attribute__((alias("__cmplog_ins_hook8"))); #endif /* defined(__APPLE__) */ void __sanitizer_cov_trace_switch(uint64_t Val, uint64_t *Cases) { for (uint64_t i = 0; i < Cases[0]; i++) { uintptr_t k = (uintptr_t)__builtin_return_address(0) + i; k = (k >> 4) ^ (k << 8); k &= CMP_MAP_W - 1; __afl_cmp_map->headers[k].type = CMP_TYPE_INS; u32 hits = __afl_cmp_map->headers[k].hits; __afl_cmp_map->headers[k].hits = hits + 1; __afl_cmp_map->headers[k].shape = 7; hits &= CMP_MAP_H - 1; __afl_cmp_map->log[k][hits].v0 = Val; __afl_cmp_map->log[k][hits].v1 = Cases[i + 2]; } } // POSIX shenanigan to see if an area is mapped. // If it is mapped as X-only, we have a problem, so maybe we should add a check // to avoid to call it on .text addresses static int area_is_mapped(void *ptr, size_t len) { char *p = ptr; char *page = (char *)((uintptr_t)p & ~(sysconf(_SC_PAGE_SIZE) - 1)); int r = msync(page, (p - page) + len, MS_ASYNC); if (r < 0) return errno != ENOMEM; return 1; } void __cmplog_rtn_hook(void *ptr1, void *ptr2) { if (!__afl_cmp_map) return; if (!area_is_mapped(ptr1, 32) || !area_is_mapped(ptr2, 32)) return; uintptr_t k = (uintptr_t)__builtin_return_address(0); k = (k >> 4) ^ (k << 8); k &= CMP_MAP_W - 1; __afl_cmp_map->headers[k].type = CMP_TYPE_RTN; u32 hits = __afl_cmp_map->headers[k].hits; __afl_cmp_map->headers[k].hits = hits + 1; __afl_cmp_map->headers[k].shape = 31; hits &= CMP_MAP_RTN_H - 1; __builtin_memcpy(((struct cmpfn_operands *)__afl_cmp_map->log[k])[hits].v0, ptr1, 32); __builtin_memcpy(((struct cmpfn_operands *)__afl_cmp_map->log[k])[hits].v1, ptr2, 32); }