/* american fuzzy lop++ - forkserver code -------------------------------------- Originally written by Michal Zalewski Forkserver design by Jann Horn Now maintained by Marc Heuse , Heiko Eißfeldt and Andrea Fioraldi and Dominik Maier Copyright 2016, 2017 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: https://www.apache.org/licenses/LICENSE-2.0 Shared code that implements a forkserver. This is used by the fuzzer as well the other components like afl-tmin. */ #include "config.h" #include "types.h" #include "debug.h" #include "common.h" #include "list.h" #include "forkserver.h" #include "hash.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include /** * The correct fds for reading and writing pipes */ /* Describe integer as memory size. */ static list_t fsrv_list = {.element_prealloc_count = 0}; static void fsrv_exec_child(afl_forkserver_t *fsrv, char **argv) { if (fsrv->qemu_mode || fsrv->cs_mode) { setenv("AFL_DISABLE_LLVM_INSTRUMENTATION", "1", 0); } execv(fsrv->target_path, argv); WARNF("Execv failed in forkserver."); } /* Initializes the struct */ void afl_fsrv_init(afl_forkserver_t *fsrv) { #ifdef __linux__ fsrv->nyx_handlers = NULL; fsrv->out_dir_path = NULL; fsrv->nyx_mode = 0; fsrv->nyx_parent = false; fsrv->nyx_standalone = false; fsrv->nyx_runner = NULL; fsrv->nyx_id = 0xFFFFFFFF; fsrv->nyx_bind_cpu_id = 0xFFFFFFFF; #endif // this structure needs default so we initialize it if this was not done // already fsrv->out_fd = -1; fsrv->out_dir_fd = -1; fsrv->dev_null_fd = -1; fsrv->dev_urandom_fd = -1; /* Settings */ fsrv->use_stdin = true; fsrv->no_unlink = false; fsrv->exec_tmout = EXEC_TIMEOUT; fsrv->init_tmout = EXEC_TIMEOUT * FORK_WAIT_MULT; fsrv->mem_limit = MEM_LIMIT; fsrv->out_file = NULL; fsrv->kill_signal = SIGKILL; /* exec related stuff */ fsrv->child_pid = -1; fsrv->map_size = get_map_size(); fsrv->real_map_size = fsrv->map_size; fsrv->use_fauxsrv = false; fsrv->last_run_timed_out = false; fsrv->debug = false; fsrv->uses_crash_exitcode = false; fsrv->uses_asan = false; fsrv->init_child_func = fsrv_exec_child; list_append(&fsrv_list, fsrv); } /* Initialize a new forkserver instance, duplicating "global" settings */ void afl_fsrv_init_dup(afl_forkserver_t *fsrv_to, afl_forkserver_t *from) { fsrv_to->use_stdin = from->use_stdin; fsrv_to->dev_null_fd = from->dev_null_fd; fsrv_to->exec_tmout = from->exec_tmout; fsrv_to->init_tmout = from->init_tmout; fsrv_to->mem_limit = from->mem_limit; fsrv_to->map_size = from->map_size; fsrv_to->real_map_size = from->real_map_size; fsrv_to->support_shmem_fuzz = from->support_shmem_fuzz; fsrv_to->out_file = from->out_file; fsrv_to->dev_urandom_fd = from->dev_urandom_fd; fsrv_to->out_fd = from->out_fd; // not sure this is a good idea fsrv_to->no_unlink = from->no_unlink; fsrv_to->uses_crash_exitcode = from->uses_crash_exitcode; fsrv_to->crash_exitcode = from->crash_exitcode; fsrv_to->kill_signal = from->kill_signal; fsrv_to->debug = from->debug; // These are forkserver specific. fsrv_to->out_dir_fd = -1; fsrv_to->child_pid = -1; fsrv_to->use_fauxsrv = 0; fsrv_to->last_run_timed_out = 0; fsrv_to->init_child_func = from->init_child_func; // Note: do not copy ->add_extra_func or ->persistent_record* list_append(&fsrv_list, fsrv_to); } /* Wrapper for select() and read(), reading a 32 bit var. Returns the time passed to read. If the wait times out, returns timeout_ms + 1; Returns 0 if an error occurred (fd closed, signal, ...); */ static u32 __attribute__((hot)) read_s32_timed(s32 fd, s32 *buf, u32 timeout_ms, volatile u8 *stop_soon_p) { fd_set readfds; FD_ZERO(&readfds); FD_SET(fd, &readfds); struct timeval timeout; int sret; ssize_t len_read; timeout.tv_sec = (timeout_ms / 1000); timeout.tv_usec = (timeout_ms % 1000) * 1000; #if !defined(__linux__) u32 read_start = get_cur_time_us(); #endif /* set exceptfds as well to return when a child exited/closed the pipe. */ restart_select: sret = select(fd + 1, &readfds, NULL, NULL, &timeout); if (likely(sret > 0)) { restart_read: if (*stop_soon_p) { // Early return - the user wants to quit. return 0; } len_read = read(fd, (u8 *)buf, 4); if (likely(len_read == 4)) { // for speed we put this first #if defined(__linux__) u32 exec_ms = MIN( timeout_ms, ((u64)timeout_ms - (timeout.tv_sec * 1000 + timeout.tv_usec / 1000))); #else u32 exec_ms = MIN(timeout_ms, (get_cur_time_us() - read_start) / 1000); #endif // ensure to report 1 ms has passed (0 is an error) return exec_ms > 0 ? exec_ms : 1; } else if (unlikely(len_read == -1 && errno == EINTR)) { goto restart_read; } else if (unlikely(len_read < 4)) { return 0; } } else if (unlikely(!sret)) { *buf = -1; return timeout_ms + 1; } else if (unlikely(sret < 0)) { if (likely(errno == EINTR)) goto restart_select; *buf = -1; return 0; } return 0; // not reached } /* Internal forkserver for non_instrumented_mode=1 and non-forkserver mode runs. It execvs for each fork, forwarding exit codes and child pids to afl. */ static void afl_fauxsrv_execv(afl_forkserver_t *fsrv, char **argv) { unsigned char tmp[4] = {0, 0, 0, 0}; pid_t child_pid; if (!be_quiet) { ACTF("Using Fauxserver:"); } /* 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) { abort(); // TODO: Abort? } void (*old_sigchld_handler)(int) = signal(SIGCHLD, SIG_DFL); while (1) { uint32_t was_killed; int status; /* Wait for parent by reading from the pipe. Exit if read fails. */ if (read(FORKSRV_FD, &was_killed, 4) != 4) { exit(0); } /* Create a clone of our process. */ child_pid = fork(); if (child_pid < 0) { PFATAL("Fork failed"); } /* In child process: close fds, resume execution. */ if (!child_pid) { // New child close(fsrv->out_dir_fd); close(fsrv->dev_null_fd); close(fsrv->dev_urandom_fd); if (fsrv->plot_file != NULL) { fclose(fsrv->plot_file); fsrv->plot_file = NULL; } // enable terminating on sigpipe in the childs struct sigaction sa; memset((char *)&sa, 0, sizeof(sa)); sa.sa_handler = SIG_DFL; sigaction(SIGPIPE, &sa, NULL); signal(SIGCHLD, old_sigchld_handler); // FORKSRV_FD is for communication with AFL, we don't need it in the // child close(FORKSRV_FD); close(FORKSRV_FD + 1); // finally: exec... execv(fsrv->target_path, argv); /* Use a distinctive bitmap signature to tell the parent about execv() falling through. */ *(u32 *)fsrv->trace_bits = EXEC_FAIL_SIG; WARNF("Execv failed in fauxserver."); break; } /* In parent process: write PID to AFL. */ if (write(FORKSRV_FD + 1, &child_pid, 4) != 4) { exit(0); } /* after child exited, get and relay exit status to parent through waitpid. */ if (waitpid(child_pid, &status, 0) < 0) { // Zombie Child could not be collected. Scary! WARNF("Fauxserver could not determine child's exit code. "); } /* Relay wait status to AFL pipe, then loop back. */ if (write(FORKSRV_FD + 1, &status, 4) != 4) { exit(1); } } } /* Report on the error received via the forkserver controller and exit */ static void report_error_and_exit(int error) { switch (error) { case FS_ERROR_MAP_SIZE: FATAL( "AFL_MAP_SIZE is not set and fuzzing target reports that the " "required size is very large. Solution: Run the fuzzing target " "stand-alone with the environment variable AFL_DEBUG=1 set and set " "the value for __afl_final_loc in the AFL_MAP_SIZE environment " "variable for afl-fuzz."); break; case FS_ERROR_MAP_ADDR: FATAL( "the fuzzing target reports that hardcoded map address might be the " "reason the mmap of the shared memory failed. Solution: recompile " "the target with either afl-clang-lto and do not set " "AFL_LLVM_MAP_ADDR or recompile with afl-clang-fast."); break; case FS_ERROR_SHM_OPEN: FATAL("the fuzzing target reports that the shm_open() call failed."); break; case FS_ERROR_SHMAT: FATAL("the fuzzing target reports that the shmat() call failed."); break; case FS_ERROR_MMAP: FATAL( "the fuzzing target reports that the mmap() call to the shared " "memory failed."); break; case FS_ERROR_OLD_CMPLOG: FATAL( "the -c cmplog target was instrumented with an too old afl++ " "version, you need to recompile it."); break; case FS_ERROR_OLD_CMPLOG_QEMU: FATAL( "The AFL++ QEMU/FRIDA loaders are from an older version, for -c you " "need to recompile it.\n"); break; default: FATAL("unknown error code %d from fuzzing target!", error); } } /* Spins up fork server. The idea is explained here: https://lcamtuf.blogspot.com/2014/10/fuzzing-binaries-without-execve.html In essence, the instrumentation allows us to skip execve(), and just keep cloning a stopped child. So, we just execute once, and then send commands through a pipe. The other part of this logic is in afl-as.h / llvm_mode */ void afl_fsrv_start(afl_forkserver_t *fsrv, char **argv, volatile u8 *stop_soon_p, u8 debug_child_output) { int st_pipe[2], ctl_pipe[2]; s32 status; s32 rlen; char *ignore_autodict = getenv("AFL_NO_AUTODICT"); #ifdef __linux__ if (unlikely(fsrv->nyx_mode)) { if (fsrv->nyx_runner != NULL) { return; } if (!be_quiet) { ACTF("Spinning up the NYX backend..."); } if (fsrv->out_dir_path == NULL) { FATAL("Nyx workdir path not found..."); } char *x = alloc_printf("%s/workdir", fsrv->out_dir_path); if (fsrv->nyx_id == 0xFFFFFFFF) { FATAL("Nyx ID is not set..."); } if (fsrv->nyx_bind_cpu_id == 0xFFFFFFFF) { FATAL("Nyx CPU ID is not set..."); } if (fsrv->nyx_standalone) { fsrv->nyx_runner = fsrv->nyx_handlers->nyx_new( fsrv->target_path, x, fsrv->nyx_bind_cpu_id, MAX_FILE, true); } else { if (fsrv->nyx_parent) { fsrv->nyx_runner = fsrv->nyx_handlers->nyx_new_parent( fsrv->target_path, x, fsrv->nyx_bind_cpu_id, MAX_FILE, true); } else { fsrv->nyx_runner = fsrv->nyx_handlers->nyx_new_child( fsrv->target_path, x, fsrv->nyx_bind_cpu_id, fsrv->nyx_id); } } ck_free(x); if (fsrv->nyx_runner == NULL) { FATAL("Something went wrong ..."); } u32 tmp_map_size = fsrv->nyx_handlers->nyx_get_bitmap_buffer_size(fsrv->nyx_runner); fsrv->real_map_size = tmp_map_size; fsrv->map_size = (((tmp_map_size + 63) >> 6) << 6); if (!be_quiet) { ACTF("Target map size: %u", fsrv->real_map_size); } fsrv->trace_bits = fsrv->nyx_handlers->nyx_get_bitmap_buffer(fsrv->nyx_runner); fsrv->nyx_handlers->nyx_option_set_reload_mode( fsrv->nyx_runner, getenv("NYX_DISABLE_SNAPSHOT_MODE") == NULL); fsrv->nyx_handlers->nyx_option_apply(fsrv->nyx_runner); fsrv->nyx_handlers->nyx_option_set_timeout(fsrv->nyx_runner, 2, 0); fsrv->nyx_handlers->nyx_option_apply(fsrv->nyx_runner); fsrv->nyx_aux_string = malloc(0x1000); memset(fsrv->nyx_aux_string, 0, 0x1000); /* dry run */ fsrv->nyx_handlers->nyx_set_afl_input(fsrv->nyx_runner, "INIT", 4); switch (fsrv->nyx_handlers->nyx_exec(fsrv->nyx_runner)) { case Abort: fsrv->nyx_handlers->nyx_shutdown(fsrv->nyx_runner); FATAL("Error: Nyx abort occured..."); break; case IoError: FATAL("Error: QEMU-Nyx has died..."); break; case Error: fsrv->nyx_handlers->nyx_shutdown(fsrv->nyx_runner); FATAL("Error: Nyx runtime error has occured..."); break; default: break; } /* autodict in Nyx mode */ if (!ignore_autodict) { x = alloc_printf("%s/workdir/dump/afl_autodict.txt", fsrv->out_dir_path); int nyx_autodict_fd = open(x, O_RDONLY); ck_free(x); if (nyx_autodict_fd >= 0) { struct stat st; if (fstat(nyx_autodict_fd, &st) >= 0) { u32 f_len = st.st_size; u8 *dict = ck_alloc(f_len); if (dict == NULL) { FATAL("Could not allocate %u bytes of autodictionary memory", f_len); } u32 offset = 0, count = 0; u32 len = f_len; while (len != 0) { rlen = read(nyx_autodict_fd, dict + offset, len); if (rlen > 0) { len -= rlen; offset += rlen; } else { FATAL( "Reading autodictionary fail at position %u with %u bytes " "left.", offset, len); } } offset = 0; while (offset < (u32)f_len && (u8)dict[offset] + offset < (u32)f_len) { fsrv->add_extra_func(fsrv->afl_ptr, dict + offset + 1, (u8)dict[offset]); offset += (1 + dict[offset]); count++; } if (!be_quiet) { ACTF("Loaded %u autodictionary entries", count); } ck_free(dict); } close(nyx_autodict_fd); } } return; } #endif if (!be_quiet) { ACTF("Spinning up the fork server..."); } #ifdef AFL_PERSISTENT_RECORD if (unlikely(fsrv->persistent_record)) { fsrv->persistent_record_data = (u8 **)ck_alloc(fsrv->persistent_record * sizeof(u8 *)); fsrv->persistent_record_len = (u32 *)ck_alloc(fsrv->persistent_record * sizeof(u32)); if (!fsrv->persistent_record_data || !fsrv->persistent_record_len) { FATAL("Unable to allocate memory for persistent replay."); } } #endif if (fsrv->use_fauxsrv) { /* TODO: Come up with some nice way to initialize this all */ if (fsrv->init_child_func != fsrv_exec_child) { FATAL("Different forkserver not compatible with fauxserver"); } if (!be_quiet) { ACTF("Using AFL++ faux forkserver..."); } fsrv->init_child_func = afl_fauxsrv_execv; } if (pipe(st_pipe) || pipe(ctl_pipe)) { PFATAL("pipe() failed"); } fsrv->last_run_timed_out = 0; fsrv->fsrv_pid = fork(); if (fsrv->fsrv_pid < 0) { PFATAL("fork() failed"); } if (!fsrv->fsrv_pid) { /* CHILD PROCESS */ // enable terminating on sigpipe in the childs struct sigaction sa; memset((char *)&sa, 0, sizeof(sa)); sa.sa_handler = SIG_DFL; sigaction(SIGPIPE, &sa, NULL); struct rlimit r; if (!fsrv->cmplog_binary) { unsetenv(CMPLOG_SHM_ENV_VAR); // we do not want that in non-cmplog fsrv } /* Umpf. On OpenBSD, the default fd limit for root users is set to soft 128. Let's try to fix that... */ if (!getrlimit(RLIMIT_NOFILE, &r) && r.rlim_cur < FORKSRV_FD + 2) { r.rlim_cur = FORKSRV_FD + 2; setrlimit(RLIMIT_NOFILE, &r); /* Ignore errors */ } if (fsrv->mem_limit) { r.rlim_max = r.rlim_cur = ((rlim_t)fsrv->mem_limit) << 20; #ifdef RLIMIT_AS setrlimit(RLIMIT_AS, &r); /* Ignore errors */ #else /* This takes care of OpenBSD, which doesn't have RLIMIT_AS, but according to reliable sources, RLIMIT_DATA covers anonymous maps - so we should be getting good protection against OOM bugs. */ setrlimit(RLIMIT_DATA, &r); /* Ignore errors */ #endif /* ^RLIMIT_AS */ } /* Dumping cores is slow and can lead to anomalies if SIGKILL is delivered before the dump is complete. */ if (!fsrv->debug) { r.rlim_max = r.rlim_cur = 0; setrlimit(RLIMIT_CORE, &r); /* Ignore errors */ } /* Isolate the process and configure standard descriptors. If out_file is specified, stdin is /dev/null; otherwise, out_fd is cloned instead. */ setsid(); if (!(debug_child_output)) { dup2(fsrv->dev_null_fd, 1); dup2(fsrv->dev_null_fd, 2); } if (!fsrv->use_stdin) { dup2(fsrv->dev_null_fd, 0); } else { dup2(fsrv->out_fd, 0); close(fsrv->out_fd); } /* Set up control and status pipes, close the unneeded original fds. */ if (dup2(ctl_pipe[0], FORKSRV_FD) < 0) { PFATAL("dup2() failed"); } if (dup2(st_pipe[1], FORKSRV_FD + 1) < 0) { PFATAL("dup2() failed"); } close(ctl_pipe[0]); close(ctl_pipe[1]); close(st_pipe[0]); close(st_pipe[1]); close(fsrv->out_dir_fd); close(fsrv->dev_null_fd); close(fsrv->dev_urandom_fd); if (fsrv->plot_file != NULL) { fclose(fsrv->plot_file); fsrv->plot_file = NULL; } /* This should improve performance a bit, since it stops the linker from doing extra work post-fork(). */ if (!getenv("LD_BIND_LAZY")) { setenv("LD_BIND_NOW", "1", 1); } /* Set sane defaults for ASAN if nothing else is specified. */ if (!getenv("ASAN_OPTIONS")) setenv("ASAN_OPTIONS", "abort_on_error=1:" "detect_leaks=0:" "malloc_context_size=0:" "symbolize=0:" "allocator_may_return_null=1:" "detect_odr_violation=0:" "handle_segv=0:" "handle_sigbus=0:" "handle_abort=0:" "handle_sigfpe=0:" "handle_sigill=0", 1); /* Set sane defaults for UBSAN if nothing else is specified. */ if (!getenv("UBSAN_OPTIONS")) setenv("UBSAN_OPTIONS", "halt_on_error=1:" "abort_on_error=1:" "malloc_context_size=0:" "allocator_may_return_null=1:" "symbolize=0:" "handle_segv=0:" "handle_sigbus=0:" "handle_abort=0:" "handle_sigfpe=0:" "handle_sigill=0", 1); /* Envs for QASan */ setenv("QASAN_MAX_CALL_STACK", "0", 0); setenv("QASAN_SYMBOLIZE", "0", 0); /* MSAN is tricky, because it doesn't support abort_on_error=1 at this point. So, we do this in a very hacky way. */ if (!getenv("MSAN_OPTIONS")) setenv("MSAN_OPTIONS", "exit_code=" STRINGIFY(MSAN_ERROR) ":" "symbolize=0:" "abort_on_error=1:" "malloc_context_size=0:" "allocator_may_return_null=1:" "msan_track_origins=0:" "handle_segv=0:" "handle_sigbus=0:" "handle_abort=0:" "handle_sigfpe=0:" "handle_sigill=0", 1); /* LSAN, too, does not support abort_on_error=1. */ if (!getenv("LSAN_OPTIONS")) setenv("LSAN_OPTIONS", "exitcode=" STRINGIFY(LSAN_ERROR) ":" "fast_unwind_on_malloc=0:" "symbolize=0:" "print_suppressions=0", 1); fsrv->init_child_func(fsrv, argv); /* Use a distinctive bitmap signature to tell the parent about execv() falling through. */ *(u32 *)fsrv->trace_bits = EXEC_FAIL_SIG; FATAL("Error: execv to target failed\n"); } /* PARENT PROCESS */ char pid_buf[16]; sprintf(pid_buf, "%d", fsrv->fsrv_pid); if (fsrv->cmplog_binary) setenv("__AFL_TARGET_PID2", pid_buf, 1); else setenv("__AFL_TARGET_PID1", pid_buf, 1); /* Close the unneeded endpoints. */ close(ctl_pipe[0]); close(st_pipe[1]); fsrv->fsrv_ctl_fd = ctl_pipe[1]; fsrv->fsrv_st_fd = st_pipe[0]; /* Wait for the fork server to come up, but don't wait too long. */ rlen = 0; if (fsrv->init_tmout) { u32 time_ms = read_s32_timed(fsrv->fsrv_st_fd, &status, fsrv->init_tmout, stop_soon_p); if (!time_ms) { s32 tmp_pid = fsrv->fsrv_pid; if (tmp_pid > 0) { kill(tmp_pid, fsrv->kill_signal); fsrv->fsrv_pid = -1; } } else if (time_ms > fsrv->init_tmout) { fsrv->last_run_timed_out = 1; s32 tmp_pid = fsrv->fsrv_pid; if (tmp_pid > 0) { kill(tmp_pid, fsrv->kill_signal); fsrv->fsrv_pid = -1; } } else { rlen = 4; } } else { rlen = read(fsrv->fsrv_st_fd, &status, 4); } /* If we have a four-byte "hello" message from the server, we're all set. Otherwise, try to figure out what went wrong. */ if (rlen == 4) { if (!be_quiet) { OKF("All right - fork server is up."); } if (getenv("AFL_DEBUG")) { ACTF("Extended forkserver functions received (%08x).", status); } if ((status & FS_OPT_ERROR) == FS_OPT_ERROR) report_error_and_exit(FS_OPT_GET_ERROR(status)); if ((status & FS_OPT_ENABLED) == FS_OPT_ENABLED) { // workaround for recent afl++ versions if ((status & FS_OPT_OLD_AFLPP_WORKAROUND) == FS_OPT_OLD_AFLPP_WORKAROUND) status = (status & 0xf0ffffff); if ((status & FS_OPT_NEWCMPLOG) == 0 && fsrv->cmplog_binary) { if (fsrv->qemu_mode || fsrv->frida_mode) { report_error_and_exit(FS_ERROR_OLD_CMPLOG_QEMU); } else { report_error_and_exit(FS_ERROR_OLD_CMPLOG); } } if ((status & FS_OPT_SNAPSHOT) == FS_OPT_SNAPSHOT) { fsrv->snapshot = 1; if (!be_quiet) { ACTF("Using SNAPSHOT feature."); } } if ((status & FS_OPT_SHDMEM_FUZZ) == FS_OPT_SHDMEM_FUZZ) { if (fsrv->support_shmem_fuzz) { fsrv->use_shmem_fuzz = 1; if (!be_quiet) { ACTF("Using SHARED MEMORY FUZZING feature."); } if ((status & FS_OPT_AUTODICT) == 0 || ignore_autodict) { u32 send_status = (FS_OPT_ENABLED | FS_OPT_SHDMEM_FUZZ); if (write(fsrv->fsrv_ctl_fd, &send_status, 4) != 4) { FATAL("Writing to forkserver failed."); } } } else { FATAL( "Target requested sharedmem fuzzing, but we failed to enable " "it."); } } if ((status & FS_OPT_MAPSIZE) == FS_OPT_MAPSIZE) { u32 tmp_map_size = FS_OPT_GET_MAPSIZE(status); if (!fsrv->map_size) { fsrv->map_size = MAP_SIZE; } fsrv->real_map_size = tmp_map_size; if (tmp_map_size % 64) { tmp_map_size = (((tmp_map_size + 63) >> 6) << 6); } if (!be_quiet) { ACTF("Target map size: %u", fsrv->real_map_size); } if (tmp_map_size > fsrv->map_size) { FATAL( "Target's coverage map size of %u is larger than the one this " "afl++ is set with (%u). Either set AFL_MAP_SIZE=%u and restart " " afl-fuzz, or change MAP_SIZE_POW2 in config.h and recompile " "afl-fuzz", tmp_map_size, fsrv->map_size, tmp_map_size); } fsrv->map_size = tmp_map_size; } if ((status & FS_OPT_AUTODICT) == FS_OPT_AUTODICT) { if (!ignore_autodict) { if (fsrv->add_extra_func == NULL || fsrv->afl_ptr == NULL) { // this is not afl-fuzz - or it is cmplog - we deny and return if (fsrv->use_shmem_fuzz) { status = (FS_OPT_ENABLED | FS_OPT_SHDMEM_FUZZ); } else { status = (FS_OPT_ENABLED); } if (write(fsrv->fsrv_ctl_fd, &status, 4) != 4) { FATAL("Writing to forkserver failed."); } return; } if (!be_quiet) { ACTF("Using AUTODICT feature."); } if (fsrv->use_shmem_fuzz) { status = (FS_OPT_ENABLED | FS_OPT_AUTODICT | FS_OPT_SHDMEM_FUZZ); } else { status = (FS_OPT_ENABLED | FS_OPT_AUTODICT); } if (write(fsrv->fsrv_ctl_fd, &status, 4) != 4) { FATAL("Writing to forkserver failed."); } if (read(fsrv->fsrv_st_fd, &status, 4) != 4) { FATAL("Reading from forkserver failed."); } if (status < 2 || (u32)status > 0xffffff) { FATAL("Dictionary has an illegal size: %d", status); } u32 offset = 0, count = 0; u32 len = status; u8 *dict = ck_alloc(len); if (dict == NULL) { FATAL("Could not allocate %u bytes of autodictionary memory", len); } while (len != 0) { rlen = read(fsrv->fsrv_st_fd, dict + offset, len); if (rlen > 0) { len -= rlen; offset += rlen; } else { FATAL( "Reading autodictionary fail at position %u with %u bytes " "left.", offset, len); } } offset = 0; while (offset < (u32)status && (u8)dict[offset] + offset < (u32)status) { fsrv->add_extra_func(fsrv->afl_ptr, dict + offset + 1, (u8)dict[offset]); offset += (1 + dict[offset]); count++; } if (!be_quiet) { ACTF("Loaded %u autodictionary entries", count); } ck_free(dict); } } } return; } if (fsrv->last_run_timed_out) { FATAL( "Timeout while initializing fork server (setting " "AFL_FORKSRV_INIT_TMOUT may help)"); } if (waitpid(fsrv->fsrv_pid, &status, 0) <= 0) { PFATAL("waitpid() failed"); } if (WIFSIGNALED(status)) { if (fsrv->mem_limit && fsrv->mem_limit < 500 && fsrv->uses_asan) { SAYF("\n" cLRD "[-] " cRST "Whoops, the target binary crashed suddenly, " "before receiving any input\n" " from the fuzzer! Since it seems to be built with ASAN and you " "have a\n" " restrictive memory limit configured, this is expected; please " "run with '-m 0'.\n"); } else if (!fsrv->mem_limit) { SAYF("\n" cLRD "[-] " cRST "Whoops, the target binary crashed suddenly, " "before receiving any input\n" " from the fuzzer! You can try the following:\n\n" " - The target binary crashes because necessary runtime " "conditions it needs\n" " are not met. Try to:\n" " 1. Run again with AFL_DEBUG=1 set and check the output of " "the target\n" " binary for clues.\n" " 2. Run again with AFL_DEBUG=1 and 'ulimit -c unlimited' and " "analyze the\n" " generated core dump.\n\n" " - Possibly the target requires a huge coverage map and has " "CTORS.\n" " Retry with setting AFL_MAP_SIZE=10000000.\n\n" MSG_FORK_ON_APPLE " - Less likely, there is a horrible bug in the fuzzer. If other " "options\n" " fail, poke for troubleshooting " "tips.\n"); } else { u8 val_buf[STRINGIFY_VAL_SIZE_MAX]; SAYF("\n" cLRD "[-] " cRST "Whoops, the target binary crashed suddenly, " "before receiving any input\n" " from the fuzzer! You can try the following:\n\n" " - The target binary crashes because necessary runtime " "conditions it needs\n" " are not met. Try to:\n" " 1. Run again with AFL_DEBUG=1 set and check the output of " "the target\n" " binary for clues.\n" " 2. Run again with AFL_DEBUG=1 and 'ulimit -c unlimited' and " "analyze the\n" " generated core dump.\n\n" " - The current memory limit (%s) is too restrictive, causing " "the\n" " target to hit an OOM condition in the dynamic linker. Try " "bumping up\n" " the limit with the -m setting in the command line. A simple " "way confirm\n" " this diagnosis would be:\n\n" MSG_ULIMIT_USAGE " /path/to/fuzzed_app )\n\n" " Tip: you can use https://jwilk.net/software/recidivm to\n" " estimate the required amount of virtual memory for the " "binary.\n\n" MSG_FORK_ON_APPLE " - Possibly the target requires a huge coverage map and has " "CTORS.\n" " Retry with setting AFL_MAP_SIZE=10000000.\n\n" " - Less likely, there is a horrible bug in the fuzzer. If other " "options\n" " fail, poke for troubleshooting " "tips.\n", stringify_mem_size(val_buf, sizeof(val_buf), fsrv->mem_limit << 20), fsrv->mem_limit - 1); } FATAL("Fork server crashed with signal %d", WTERMSIG(status)); } if (*(u32 *)fsrv->trace_bits == EXEC_FAIL_SIG) { FATAL("Unable to execute target application ('%s')", argv[0]); } if (fsrv->mem_limit && fsrv->mem_limit < 500 && fsrv->uses_asan) { SAYF("\n" cLRD "[-] " cRST "Hmm, looks like the target binary terminated " "before we could complete a\n" " handshake with the injected code. Since it seems to be built " "with ASAN and\n" " you have a restrictive memory limit configured, this is " "expected; please\n" " run with '-m 0'.\n"); } else if (!fsrv->mem_limit) { SAYF("\n" cLRD "[-] " cRST "Hmm, looks like the target binary terminated before we could complete" " a\n" "handshake with the injected code. You can try the following:\n\n" " - The target binary crashes because necessary runtime conditions " "it needs\n" " are not met. Try to:\n" " 1. Run again with AFL_DEBUG=1 set and check the output of the " "target\n" " binary for clues.\n" " 2. Run again with AFL_DEBUG=1 and 'ulimit -c unlimited' and " "analyze the\n" " generated core dump.\n\n" " - Possibly the target requires a huge coverage map and has " "CTORS.\n" " Retry with setting AFL_MAP_SIZE=10000000.\n\n" "Otherwise there is a horrible bug in the fuzzer.\n" "Poke for troubleshooting tips.\n"); } else { u8 val_buf[STRINGIFY_VAL_SIZE_MAX]; SAYF( "\n" cLRD "[-] " cRST "Hmm, looks like the target binary terminated " "before we could complete a\n" " handshake with the injected code. You can try the following:\n\n" "%s" " - The target binary crashes because necessary runtime conditions " "it needs\n" " are not met. Try to:\n" " 1. Run again with AFL_DEBUG=1 set and check the output of the " "target\n" " binary for clues.\n" " 2. Run again with AFL_DEBUG=1 and 'ulimit -c unlimited' and " "analyze the\n" " generated core dump.\n\n" " - Possibly the target requires a huge coverage map and has " "CTORS.\n" " Retry with setting AFL_MAP_SIZE=10000000.\n\n" " - The current memory limit (%s) is too restrictive, causing an " "OOM\n" " fault in the dynamic linker. This can be fixed with the -m " "option. A\n" " simple way to confirm the diagnosis may be:\n\n" MSG_ULIMIT_USAGE " /path/to/fuzzed_app )\n\n" " Tip: you can use https://jwilk.net/software/recidivm to\n" " estimate the required amount of virtual memory for the " "binary.\n\n" " - The target was compiled with afl-clang-lto and a constructor " "was\n" " instrumented, recompiling without AFL_LLVM_MAP_ADDR might solve " "your \n" " problem\n\n" " - Less likely, there is a horrible bug in the fuzzer. If other " "options\n" " fail, poke for troubleshooting " "tips.\n", getenv(DEFER_ENV_VAR) ? " - You are using deferred forkserver, but __AFL_INIT() is " "never\n" " reached before the program terminates.\n\n" : "", stringify_int(val_buf, sizeof(val_buf), fsrv->mem_limit << 20), fsrv->mem_limit - 1); } FATAL("Fork server handshake failed"); } /* Stop the forkserver and child */ void afl_fsrv_kill(afl_forkserver_t *fsrv) { if (fsrv->child_pid > 0) { kill(fsrv->child_pid, fsrv->kill_signal); } if (fsrv->fsrv_pid > 0) { kill(fsrv->fsrv_pid, fsrv->kill_signal); if (waitpid(fsrv->fsrv_pid, NULL, 0) <= 0) { WARNF("error waitpid\n"); } } close(fsrv->fsrv_ctl_fd); close(fsrv->fsrv_st_fd); fsrv->fsrv_pid = -1; fsrv->child_pid = -1; #ifdef __linux__ if (fsrv->nyx_mode) { free(fsrv->nyx_aux_string); fsrv->nyx_handlers->nyx_shutdown(fsrv->nyx_runner); } #endif } /* Get the map size from the target forkserver */ u32 afl_fsrv_get_mapsize(afl_forkserver_t *fsrv, char **argv, volatile u8 *stop_soon_p, u8 debug_child_output) { afl_fsrv_start(fsrv, argv, stop_soon_p, debug_child_output); return fsrv->map_size; } /* Delete the current testcase and write the buf to the testcase file */ void __attribute__((hot)) afl_fsrv_write_to_testcase(afl_forkserver_t *fsrv, u8 *buf, size_t len) { #ifdef __linux__ if (unlikely(fsrv->nyx_mode)) { fsrv->nyx_handlers->nyx_set_afl_input(fsrv->nyx_runner, buf, len); return; } #endif #ifdef AFL_PERSISTENT_RECORD if (unlikely(fsrv->persistent_record)) { fsrv->persistent_record_len[fsrv->persistent_record_idx] = len; fsrv->persistent_record_data[fsrv->persistent_record_idx] = afl_realloc( (void **)&fsrv->persistent_record_data[fsrv->persistent_record_idx], len); if (unlikely(!fsrv->persistent_record_data[fsrv->persistent_record_idx])) { FATAL("allocating replay memory failed."); } memcpy(fsrv->persistent_record_data[fsrv->persistent_record_idx], buf, len); if (unlikely(++fsrv->persistent_record_idx >= fsrv->persistent_record)) { fsrv->persistent_record_idx = 0; } } #endif if (likely(fsrv->use_shmem_fuzz)) { if (unlikely(len > MAX_FILE)) len = MAX_FILE; *fsrv->shmem_fuzz_len = len; memcpy(fsrv->shmem_fuzz, buf, len); #ifdef _DEBUG if (getenv("AFL_DEBUG")) { fprintf(stderr, "FS crc: %016llx len: %u\n", hash64(fsrv->shmem_fuzz, *fsrv->shmem_fuzz_len, HASH_CONST), *fsrv->shmem_fuzz_len); fprintf(stderr, "SHM :"); for (u32 i = 0; i < *fsrv->shmem_fuzz_len; i++) fprintf(stderr, "%02x", fsrv->shmem_fuzz[i]); fprintf(stderr, "\nORIG:"); for (u32 i = 0; i < *fsrv->shmem_fuzz_len; i++) fprintf(stderr, "%02x", buf[i]); fprintf(stderr, "\n"); } #endif } else { s32 fd = fsrv->out_fd; if (!fsrv->use_stdin && fsrv->out_file) { if (unlikely(fsrv->no_unlink)) { fd = open(fsrv->out_file, O_WRONLY | O_CREAT | O_TRUNC, DEFAULT_PERMISSION); } else { unlink(fsrv->out_file); /* Ignore errors. */ fd = open(fsrv->out_file, O_WRONLY | O_CREAT | O_EXCL, DEFAULT_PERMISSION); } if (fd < 0) { PFATAL("Unable to create '%s'", fsrv->out_file); } } else if (unlikely(fd <= 0)) { // We should have a (non-stdin) fd at this point, else we got a problem. FATAL( "Nowhere to write output to (neither out_fd nor out_file set (fd is " "%d))", fd); } else { lseek(fd, 0, SEEK_SET); } // fprintf(stderr, "WRITE %d %u\n", fd, len); ck_write(fd, buf, len, fsrv->out_file); if (fsrv->use_stdin) { if (ftruncate(fd, len)) { PFATAL("ftruncate() failed"); } lseek(fd, 0, SEEK_SET); } else { close(fd); } } } /* Execute target application, monitoring for timeouts. Return status information. The called program will update afl->fsrv->trace_bits. */ fsrv_run_result_t __attribute__((hot)) afl_fsrv_run_target(afl_forkserver_t *fsrv, u32 timeout, volatile u8 *stop_soon_p) { s32 res; u32 exec_ms; u32 write_value = fsrv->last_run_timed_out; #ifdef __linux__ if (fsrv->nyx_mode) { static uint32_t last_timeout_value = 0; if (last_timeout_value != timeout) { fsrv->nyx_handlers->nyx_option_set_timeout( fsrv->nyx_runner, timeout / 1000, (timeout % 1000) * 1000); fsrv->nyx_handlers->nyx_option_apply(fsrv->nyx_runner); last_timeout_value = timeout; } enum NyxReturnValue ret_val = fsrv->nyx_handlers->nyx_exec(fsrv->nyx_runner); fsrv->total_execs++; switch (ret_val) { case Normal: return FSRV_RUN_OK; case Crash: case Asan: return FSRV_RUN_CRASH; case Timout: return FSRV_RUN_TMOUT; case InvalidWriteToPayload: /* ??? */ FATAL("FixMe: Nyx InvalidWriteToPayload handler is missing"); break; case Abort: fsrv->nyx_handlers->nyx_shutdown(fsrv->nyx_runner); FATAL("Error: Nyx abort occured..."); case IoError: if (*stop_soon_p) { return 0; } else { FATAL("Error: QEMU-Nyx has died..."); } break; case Error: FATAL("Error: Nyx runtime error has occured..."); break; } return FSRV_RUN_OK; } #endif /* After this memset, fsrv->trace_bits[] are effectively volatile, so we must prevent any earlier operations from venturing into that territory. */ #ifdef __linux__ if (!fsrv->nyx_mode) { memset(fsrv->trace_bits, 0, fsrv->map_size); MEM_BARRIER(); } #else memset(fsrv->trace_bits, 0, fsrv->map_size); MEM_BARRIER(); #endif /* we have the fork server (or faux server) up and running First, tell it if the previous run timed out. */ if ((res = write(fsrv->fsrv_ctl_fd, &write_value, 4)) != 4) { if (*stop_soon_p) { return 0; } RPFATAL(res, "Unable to request new process from fork server (OOM?)"); } fsrv->last_run_timed_out = 0; if ((res = read(fsrv->fsrv_st_fd, &fsrv->child_pid, 4)) != 4) { if (*stop_soon_p) { return 0; } RPFATAL(res, "Unable to request new process from fork server (OOM?)"); } #ifdef AFL_PERSISTENT_RECORD // end of persistent loop? if (unlikely(fsrv->persistent_record && fsrv->persistent_record_pid != fsrv->child_pid)) { fsrv->persistent_record_pid = fsrv->child_pid; u32 idx, val; if (unlikely(!fsrv->persistent_record_idx)) idx = fsrv->persistent_record - 1; else idx = fsrv->persistent_record_idx - 1; val = fsrv->persistent_record_len[idx]; memset((void *)fsrv->persistent_record_len, 0, fsrv->persistent_record * sizeof(u32)); fsrv->persistent_record_len[idx] = val; } #endif if (fsrv->child_pid <= 0) { if (*stop_soon_p) { return 0; } if ((fsrv->child_pid & FS_OPT_ERROR) && FS_OPT_GET_ERROR(fsrv->child_pid) == FS_ERROR_SHM_OPEN) FATAL( "Target reported shared memory access failed (perhaps increase " "shared memory available)."); FATAL("Fork server is misbehaving (OOM?)"); } exec_ms = read_s32_timed(fsrv->fsrv_st_fd, &fsrv->child_status, timeout, stop_soon_p); if (exec_ms > timeout) { /* If there was no response from forkserver after timeout seconds, we kill the child. The forkserver should inform us afterwards */ s32 tmp_pid = fsrv->child_pid; if (tmp_pid > 0) { kill(tmp_pid, fsrv->kill_signal); fsrv->child_pid = -1; } fsrv->last_run_timed_out = 1; if (read(fsrv->fsrv_st_fd, &fsrv->child_status, 4) < 4) { exec_ms = 0; } } if (!exec_ms) { if (*stop_soon_p) { return 0; } SAYF("\n" cLRD "[-] " cRST "Unable to communicate with fork server. Some possible reasons:\n\n" " - You've run out of memory. Use -m to increase the the memory " "limit\n" " to something higher than %llu.\n" " - The binary or one of the libraries it uses manages to " "create\n" " threads before the forkserver initializes.\n" " - The binary, at least in some circumstances, exits in a way " "that\n" " also kills the parent process - raise() could be the " "culprit.\n" " - If using persistent mode with QEMU, " "AFL_QEMU_PERSISTENT_ADDR " "is\n" " probably not valid (hint: add the base address in case of " "PIE)" "\n\n" "If all else fails you can disable the fork server via " "AFL_NO_FORKSRV=1.\n", fsrv->mem_limit); RPFATAL(res, "Unable to communicate with fork server"); } if (!WIFSTOPPED(fsrv->child_status)) { fsrv->child_pid = -1; } fsrv->total_execs++; /* Any subsequent operations on fsrv->trace_bits must not be moved by the compiler below this point. Past this location, fsrv->trace_bits[] behave very normally and do not have to be treated as volatile. */ MEM_BARRIER(); /* Report outcome to caller. */ /* Was the run unsuccessful? */ if (unlikely(*(u32 *)fsrv->trace_bits == EXEC_FAIL_SIG)) { return FSRV_RUN_ERROR; } /* Did we timeout? */ if (unlikely(fsrv->last_run_timed_out)) { fsrv->last_kill_signal = fsrv->kill_signal; return FSRV_RUN_TMOUT; } /* Did we crash? In a normal case, (abort) WIFSIGNALED(child_status) will be set. MSAN in uses_asan mode uses a special exit code as it doesn't support abort_on_error. On top, a user may specify a custom AFL_CRASH_EXITCODE. Handle all three cases here. */ if (unlikely( /* A normal crash/abort */ (WIFSIGNALED(fsrv->child_status)) || /* special handling for msan and lsan */ (fsrv->uses_asan && (WEXITSTATUS(fsrv->child_status) == MSAN_ERROR || WEXITSTATUS(fsrv->child_status) == LSAN_ERROR)) || /* the custom crash_exitcode was returned by the target */ (fsrv->uses_crash_exitcode && WEXITSTATUS(fsrv->child_status) == fsrv->crash_exitcode))) { #ifdef AFL_PERSISTENT_RECORD if (unlikely(fsrv->persistent_record)) { char fn[PATH_MAX]; u32 i, writecnt = 0; for (i = 0; i < fsrv->persistent_record; ++i) { u32 entry = (i + fsrv->persistent_record_idx) % fsrv->persistent_record; u8 *data = fsrv->persistent_record_data[entry]; u32 len = fsrv->persistent_record_len[entry]; if (likely(len && data)) { snprintf(fn, sizeof(fn), "%s/RECORD:%06u,cnt:%06u", fsrv->persistent_record_dir, fsrv->persistent_record_cnt, writecnt++); int fd = open(fn, O_CREAT | O_TRUNC | O_WRONLY, 0644); if (fd >= 0) { ck_write(fd, data, len, fn); close(fd); } } } ++fsrv->persistent_record_cnt; } #endif /* For a proper crash, set last_kill_signal to WTERMSIG, else set it to 0 */ fsrv->last_kill_signal = WIFSIGNALED(fsrv->child_status) ? WTERMSIG(fsrv->child_status) : 0; return FSRV_RUN_CRASH; } /* success :) */ return FSRV_RUN_OK; } void afl_fsrv_killall() { LIST_FOREACH(&fsrv_list, afl_forkserver_t, { afl_fsrv_kill(el); }); } void afl_fsrv_deinit(afl_forkserver_t *fsrv) { afl_fsrv_kill(fsrv); list_remove(&fsrv_list, fsrv); }