整体逻辑框架

src/AFLplusplus-stable/src/afl-as.c

@@ -0,0 +1,671 @@
+/*
+   american fuzzy lop++ - wrapper for GNU as
+   -----------------------------------------
+
+   Originally written by Michal Zalewski
+
+   Now maintained by Marc Heuse <mh@mh-sec.de>,
+                        Heiko Eissfeldt <heiko.eissfeldt@hexco.de> and
+                        Andrea Fioraldi <andreafioraldi@gmail.com>
+
+   Copyright 2016, 2017 Google Inc. All rights reserved.
+   Copyright 2019-2024 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
+
+   The sole purpose of this wrapper is to preprocess assembly files generated
+   by GCC / clang and inject the instrumentation bits included from afl-as.h. It
+   is automatically invoked by the toolchain when compiling programs using
+   afl-gcc / afl-clang.
+
+   Note that it's an explicit non-goal to instrument hand-written assembly,
+   be it in separate .s files or in __asm__ blocks. The only aspiration this
+   utility has right now is to be able to skip them gracefully and allow the
+   compilation process to continue.
+
+   That said, see utils/clang_asm_normalize/ for a solution that may
+   allow clang users to make things work even with hand-crafted assembly. Just
+   note that there is no equivalent for GCC.
+
+ */
+
+#define AFL_MAIN
+
+#include "config.h"
+#include "types.h"
+#include "debug.h"
+#include "alloc-inl.h"
+
+#include "afl-as.h"
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <limits.h>
+#include <ctype.h>
+#include <fcntl.h>
+
+#include <sys/wait.h>
+#include <sys/time.h>
+
+static u8 **as_params;              /* Parameters passed to the real 'as'   */
+
+static u8 *input_file;              /* Originally specified input file      */
+static u8 *modified_file;           /* Instrumented file for the real 'as'  */
+
+static u8 be_quiet,                 /* Quiet mode (no stderr output)        */
+    clang_mode,                     /* Running in clang mode?               */
+    pass_thru,                      /* Just pass data through?              */
+    just_version,                   /* Just show version?                   */
+    sanitizer;                      /* Using ASAN / MSAN                    */
+
+static u32 inst_ratio = 100,        /* Instrumentation probability (%)      */
+    as_par_cnt = 1;                 /* Number of params to 'as'             */
+
+/* If we don't find --32 or --64 in the command line, default to
+   instrumentation for whichever mode we were compiled with. This is not
+   perfect, but should do the trick for almost all use cases. */
+
+#ifdef WORD_SIZE_64
+
+static u8 use_64bit = 1;
+
+#else
+
+static u8 use_64bit = 0;
+
+  #ifdef __APPLE__
+    #error "Sorry, 32-bit Apple platforms are not supported."
+  #endif                                                       /* __APPLE__ */
+
+#endif                                                     /* ^WORD_SIZE_64 */
+
+/* Examine and modify parameters to pass to 'as'. Note that the file name
+   is always the last parameter passed by GCC, so we exploit this property
+   to keep the code simple. */
+
+static void edit_params(int argc, char **argv) {
+
+  u8 *tmp_dir = getenv("TMPDIR"), *afl_as = getenv("AFL_AS");
+  u32 i, input_index;
+
+#ifdef __APPLE__
+
+  u8 use_clang_as = 0;
+
+  /* On MacOS X, the Xcode cctool 'as' driver is a bit stale and does not work
+     with the code generated by newer versions of clang that are hand-built
+     by the user. See the thread here: https://goo.gl/HBWDtn.
+
+     To work around this, when using clang and running without AFL_AS
+     specified, we will actually call 'clang -c' instead of 'as -q' to
+     compile the assembly file.
+
+     The tools aren't cmdline-compatible, but at least for now, we can
+     seemingly get away with this by making only very minor tweaks. Thanks
+     to Nico Weber for the idea. */
+
+  if (clang_mode && !afl_as) {
+
+    use_clang_as = 1;
+
+    afl_as = getenv("AFL_CC");
+    if (!afl_as) afl_as = getenv("AFL_CXX");
+    if (!afl_as) afl_as = "clang";
+
+  }
+
+#endif                                                         /* __APPLE__ */
+
+  /* Although this is not documented, GCC also uses TEMP and TMP when TMPDIR
+     is not set. We need to check these non-standard variables to properly
+     handle the pass_thru logic later on. */
+
+  if (!tmp_dir) { tmp_dir = getenv("TEMP"); }
+  if (!tmp_dir) { tmp_dir = getenv("TMP"); }
+  if (!tmp_dir) { tmp_dir = "/tmp"; }
+
+  as_params = ck_alloc((argc + 32) * sizeof(u8 *));
+  if (unlikely((INT_MAX - 32) < argc || !as_params)) {
+
+    FATAL("Too many parameters passed to as");
+
+  }
+
+  as_params[0] = afl_as ? afl_as : (u8 *)"as";
+
+  as_params[argc] = 0;
+
+  /* Find the input file.  It's usually located near the end.
+     Assume there won't be any arguments referring to files after the input
+     file, e.g. as input.s -o output.o */
+  for (input_index = argc - 1; input_index > 0; input_index--) {
+
+    input_file = argv[input_index];
+    /* Clang may add debug arguments after the input file. */
+    if (strncmp(input_file, "-g", 2)) break;
+
+  }
+
+  if (input_index == 0)
+    FATAL("Could not find input file (not called through afl-gcc?)");
+
+  for (i = 1; (s32)i < argc; i++) {
+
+    if (i == input_index) continue;
+
+    if (!strcmp(argv[i], "--64")) {
+
+      use_64bit = 1;
+
+    } else if (!strcmp(argv[i], "--32")) {
+
+      use_64bit = 0;
+
+    }
+
+#ifdef __APPLE__
+
+    /* The Apple case is a bit different... */
+
+    if (!strcmp(argv[i], "-arch") && i + 1 < (u32)argc) {
+
+      if (!strcmp(argv[i + 1], "x86_64"))
+        use_64bit = 1;
+      else if (!strcmp(argv[i + 1], "i386"))
+        FATAL("Sorry, 32-bit Apple platforms are not supported.");
+
+    }
+
+    /* Strip options that set the preference for a particular upstream
+       assembler in Xcode. */
+
+    if (clang_mode && (!strcmp(argv[i], "-q") || !strcmp(argv[i], "-Q")))
+      continue;
+
+#endif                                                         /* __APPLE__ */
+
+    as_params[as_par_cnt++] = argv[i];
+
+  }
+
+#ifdef __APPLE__
+
+  /* When calling clang as the upstream assembler, append -c -x assembler
+     and hope for the best. */
+
+  if (use_clang_as) {
+
+    as_params[as_par_cnt++] = "-c";
+    as_params[as_par_cnt++] = "-x";
+    as_params[as_par_cnt++] = "assembler";
+
+  }
+
+#endif                                                         /* __APPLE__ */
+
+  if (input_file[0] == '-') {
+
+    if (!strcmp(input_file + 1, "-version")) {
+
+      just_version = 1;
+      modified_file = input_file;
+      goto wrap_things_up;
+
+    }
+
+    if (input_file[1]) {
+
+      FATAL("Incorrect use (not called through afl-gcc?)");
+
+    } else {
+
+      input_file = NULL;
+
+    }
+
+  } else {
+
+    /* Check if this looks like a standard invocation as a part of an attempt
+       to compile a program, rather than using gcc on an ad-hoc .s file in
+       a format we may not understand. This works around an issue compiling
+       NSS. */
+
+    if (strncmp(input_file, tmp_dir, strlen(tmp_dir)) &&
+        strncmp(input_file, "/var/tmp/", 9) &&
+        strncmp(input_file, "/tmp/", 5) &&
+        getenv("AFL_AS_FORCE_INSTRUMENT") == NULL) {
+
+      pass_thru = 1;
+
+    } else if (getenv("AFL_AS_FORCE_INSTRUMENT")) {
+
+      unsetenv("AFL_AS_FORCE_INSTRUMENT");
+
+    }
+
+  }
+
+  modified_file = alloc_printf("%s/.afl-%u-%u-%u.s", tmp_dir, (u32)getpid(),
+                               (u32)time(NULL), (u32)random());
+
+wrap_things_up:
+
+  as_params[as_par_cnt++] = modified_file;
+  as_params[as_par_cnt] = NULL;
+
+}
+
+/* Process input file, generate modified_file. Insert instrumentation in all
+   the appropriate places. */
+
+static void add_instrumentation(void) {
+
+  static u8 line[MAX_LINE];
+
+  FILE *inf;
+  FILE *outf;
+  s32   outfd;
+  u32   ins_lines = 0;
+
+  u8 instr_ok = 0, skip_csect = 0, skip_next_label = 0, skip_intel = 0,
+     skip_app = 0, instrument_next = 0;
+
+#ifdef __APPLE__
+
+  u8 *colon_pos;
+
+#endif                                                         /* __APPLE__ */
+
+  if (input_file) {
+
+    inf = fopen(input_file, "r");
+    if (!inf) { PFATAL("Unable to read '%s'", input_file); }
+
+  } else {
+
+    inf = stdin;
+
+  }
+
+  outfd = open(modified_file, O_WRONLY | O_EXCL | O_CREAT, DEFAULT_PERMISSION);
+
+  if (outfd < 0) { PFATAL("Unable to write to '%s'", modified_file); }
+
+  outf = fdopen(outfd, "w");
+
+  if (!outf) { PFATAL("fdopen() failed"); }
+
+  while (fgets(line, MAX_LINE, inf)) {
+
+    /* In some cases, we want to defer writing the instrumentation trampoline
+       until after all the labels, macros, comments, etc. If we're in this
+       mode, and if the line starts with a tab followed by a character, dump
+       the trampoline now. */
+
+    if (!pass_thru && !skip_intel && !skip_app && !skip_csect && instr_ok &&
+        instrument_next && line[0] == '\t' && isalpha(line[1])) {
+
+      fprintf(outf, use_64bit ? trampoline_fmt_64 : trampoline_fmt_32,
+              R(MAP_SIZE));
+
+      instrument_next = 0;
+      ins_lines++;
+
+    }
+
+    /* Output the actual line, call it a day in pass-thru mode. */
+
+    fputs(line, outf);
+
+    if (pass_thru) { continue; }
+
+    /* All right, this is where the actual fun begins. For one, we only want to
+       instrument the .text section. So, let's keep track of that in processed
+       files - and let's set instr_ok accordingly. */
+
+    if (line[0] == '\t' && line[1] == '.') {
+
+      /* OpenBSD puts jump tables directly inline with the code, which is
+         a bit annoying. They use a specific format of p2align directives
+         around them, so we use that as a signal. */
+
+      if (!clang_mode && instr_ok && !strncmp(line + 2, "p2align ", 8) &&
+          isdigit(line[10]) && line[11] == '\n') {
+
+        skip_next_label = 1;
+
+      }
+
+      if (!strncmp(line + 2, "text\n", 5) ||
+          !strncmp(line + 2, "section\t.text", 13) ||
+          !strncmp(line + 2, "section\t__TEXT,__text", 21) ||
+          !strncmp(line + 2, "section __TEXT,__text", 21)) {
+
+        instr_ok = 1;
+        continue;
+
+      }
+
+      if (!strncmp(line + 2, "section\t", 8) ||
+          !strncmp(line + 2, "section ", 8) || !strncmp(line + 2, "bss\n", 4) ||
+          !strncmp(line + 2, "data\n", 5)) {
+
+        instr_ok = 0;
+        continue;
+
+      }
+
+    }
+
+    /* Detect off-flavor assembly (rare, happens in gdb). When this is
+       encountered, we set skip_csect until the opposite directive is
+       seen, and we do not instrument. */
+
+    if (strstr(line, ".code")) {
+
+      if (strstr(line, ".code32")) { skip_csect = use_64bit; }
+      if (strstr(line, ".code64")) { skip_csect = !use_64bit; }
+
+    }
+
+    /* Detect syntax changes, as could happen with hand-written assembly.
+       Skip Intel blocks, resume instrumentation when back to AT&T. */
+
+    if (strstr(line, ".intel_syntax")) { skip_intel = 1; }
+    if (strstr(line, ".att_syntax")) { skip_intel = 0; }
+
+    /* Detect and skip ad-hoc __asm__ blocks, likewise skipping them. */
+
+    if (line[0] == '#' || line[1] == '#') {
+
+      if (strstr(line, "#APP")) { skip_app = 1; }
+      if (strstr(line, "#NO_APP")) { skip_app = 0; }
+
+    }
+
+    /* If we're in the right mood for instrumenting, check for function
+       names or conditional labels. This is a bit messy, but in essence,
+       we want to catch:
+
+         ^main:      - function entry point (always instrumented)
+         ^.L0:       - GCC branch label
+         ^.LBB0_0:   - clang branch label (but only in clang mode)
+         ^\tjnz foo  - conditional branches
+
+       ...but not:
+
+         ^# BB#0:    - clang comments
+         ^ # BB#0:   - ditto
+         ^.Ltmp0:    - clang non-branch labels
+         ^.LC0       - GCC non-branch labels
+         ^.LBB0_0:   - ditto (when in GCC mode)
+         ^\tjmp foo  - non-conditional jumps
+
+       Additionally, clang and GCC on MacOS X follow a different convention
+       with no leading dots on labels, hence the weird maze of #ifdefs
+       later on.
+
+     */
+
+    if (skip_intel || skip_app || skip_csect || !instr_ok || line[0] == '#' ||
+        line[0] == ' ') {
+
+      continue;
+
+    }
+
+    /* Conditional branch instruction (jnz, etc). We append the instrumentation
+       right after the branch (to instrument the not-taken path) and at the
+       branch destination label (handled later on). */
+
+    if (line[0] == '\t') {
+
+      if (line[1] == 'j' && line[2] != 'm' && R(100) < (long)inst_ratio) {
+
+        fprintf(outf, use_64bit ? trampoline_fmt_64 : trampoline_fmt_32,
+                R(MAP_SIZE));
+
+        ins_lines++;
+
+      }
+
+      continue;
+
+    }
+
+    /* Label of some sort. This may be a branch destination, but we need to
+       read carefully and account for several different formatting
+       conventions. */
+
+#ifdef __APPLE__
+
+    /* Apple: L<whatever><digit>: */
+
+    if ((colon_pos = strstr(line, ":"))) {
+
+      if (line[0] == 'L' && isdigit(*(colon_pos - 1))) {
+
+#else
+
+    /* Everybody else: .L<whatever>: */
+
+    if (strstr(line, ":")) {
+
+      if (line[0] == '.') {
+
+#endif                                                         /* __APPLE__ */
+
+        /* .L0: or LBB0_0: style jump destination */
+
+#ifdef __APPLE__
+
+        /* Apple: L<num> / LBB<num> */
+
+        if ((isdigit(line[1]) || (clang_mode && !strncmp(line, "LBB", 3))) &&
+            R(100) < (long)inst_ratio) {
+
+#else
+
+        /* Apple: .L<num> / .LBB<num> */
+
+        if ((isdigit(line[2]) ||
+             (clang_mode && !strncmp(line + 1, "LBB", 3))) &&
+            R(100) < (long)inst_ratio) {
+
+#endif                                                         /* __APPLE__ */
+
+          /* An optimization is possible here by adding the code only if the
+             label is mentioned in the code in contexts other than call / jmp.
+             That said, this complicates the code by requiring two-pass
+             processing (messy with stdin), and results in a speed gain
+             typically under 10%, because compilers are generally pretty good
+             about not generating spurious intra-function jumps.
+
+             We use deferred output chiefly to avoid disrupting
+             .Lfunc_begin0-style exception handling calculations (a problem on
+             MacOS X). */
+
+          if (!skip_next_label) {
+
+            instrument_next = 1;
+
+          } else {
+
+            skip_next_label = 0;
+
+          }
+
+        }
+
+      } else {
+
+        /* Function label (always instrumented, deferred mode). */
+
+        instrument_next = 1;
+
+      }
+
+    }
+
+  }
+
+  if (ins_lines) { fputs(use_64bit ? main_payload_64 : main_payload_32, outf); }
+
+  if (input_file) { fclose(inf); }
+  fclose(outf);
+
+  if (!be_quiet) {
+
+    if (!ins_lines) {
+
+      WARNF("No instrumentation targets found%s.",
+            pass_thru ? " (pass-thru mode)" : "");
+
+    } else {
+
+      char modeline[100];
+      snprintf(modeline, sizeof(modeline), "%s%s%s%s%s%s",
+               getenv("AFL_HARDEN") ? "hardened" : "non-hardened",
+               getenv("AFL_USE_ASAN") ? ", ASAN" : "",
+               getenv("AFL_USE_MSAN") ? ", MSAN" : "",
+               getenv("AFL_USE_TSAN") ? ", TSAN" : "",
+               getenv("AFL_USE_UBSAN") ? ", UBSAN" : "",
+               getenv("AFL_USE_LSAN") ? ", LSAN" : "");
+
+      OKF("Instrumented %u locations (%s-bit, %s mode, ratio %u%%).", ins_lines,
+          use_64bit ? "64" : "32", modeline, inst_ratio);
+
+    }
+
+  }
+
+}
+
+/* Main entry point */
+
+int main(int argc, char **argv) {
+
+  s32 pid;
+  u32 rand_seed, i, j;
+  int status;
+  u8 *inst_ratio_str = getenv("AFL_INST_RATIO");
+
+  struct timeval  tv;
+  struct timezone tz;
+
+  clang_mode = !!getenv(CLANG_ENV_VAR);
+
+  if ((isatty(2) && !getenv("AFL_QUIET")) || getenv("AFL_DEBUG") != NULL) {
+
+    SAYF(cCYA "afl-as" VERSION cRST " by Michal Zalewski\n");
+
+  } else {
+
+    be_quiet = 1;
+
+  }
+
+  if (argc < 2 || (argc == 2 && strcmp(argv[1], "-h") == 0)) {
+
+    fprintf(
+        stdout,
+        "afl-as" VERSION
+        " by Michal Zalewski\n"
+        "\n%s [-h]\n\n"
+        "This is a helper application for afl-fuzz. It is a wrapper around GNU "
+        "'as',\n"
+        "executed by the toolchain whenever using afl-gcc or afl-clang. You "
+        "probably\n"
+        "don't want to run this program directly.\n\n"
+
+        "Rarely, when dealing with extremely complex projects, it may be "
+        "advisable\n"
+        "to set AFL_INST_RATIO to a value less than 100 in order to reduce "
+        "the\n"
+        "odds of instrumenting every discovered branch.\n\n"
+        "Environment variables used:\n"
+        "AFL_AS: path to assembler to use for instrumented files\n"
+        "AFL_CC: fall back path to assembler\n"
+        "AFL_CXX: fall back path to assembler\n"
+        "TMPDIR: directory to use for temporary files\n"
+        "TEMP: fall back path to directory for temporary files\n"
+        "TMP: fall back path to directory for temporary files\n"
+        "AFL_INST_RATIO: user specified instrumentation ratio\n"
+        "AFL_QUIET: suppress verbose output\n"
+        "AFL_KEEP_ASSEMBLY: leave instrumented assembly files\n"
+        "AFL_AS_FORCE_INSTRUMENT: force instrumentation for asm sources\n"
+        "AFL_HARDEN, AFL_USE_ASAN, AFL_USE_MSAN, AFL_USE_UBSAN, AFL_USE_LSAN:\n"
+        "  used in the instrumentation summary message\n",
+        argv[0]);
+
+    exit(1);
+
+  }
+
+  gettimeofday(&tv, &tz);
+
+  rand_seed = tv.tv_sec ^ tv.tv_usec ^ getpid();
+  // in fast systems where pids can repeat in the same seconds we need this
+  for (i = 1; (s32)i < argc; i++)
+    for (j = 0; j < strlen(argv[i]); j++)
+      rand_seed += argv[i][j];
+
+  srandom(rand_seed);
+
+  edit_params(argc, argv);
+
+  if (inst_ratio_str) {
+
+    if (sscanf(inst_ratio_str, "%u", &inst_ratio) != 1 || inst_ratio > 100) {
+
+      FATAL("Bad value of AFL_INST_RATIO (must be between 0 and 100)");
+
+    }
+
+  }
+
+  if (getenv(AS_LOOP_ENV_VAR)) {
+
+    FATAL("Endless loop when calling 'as' (remove '.' from your PATH)");
+
+  }
+
+  setenv(AS_LOOP_ENV_VAR, "1", 1);
+
+  /* When compiling with ASAN, we don't have a particularly elegant way to skip
+     ASAN-specific branches. But we can probabilistically compensate for
+     that... */
+
+  if (getenv("AFL_USE_ASAN") || getenv("AFL_USE_MSAN")) {
+
+    sanitizer = 1;
+    if (!getenv("AFL_INST_RATIO")) { inst_ratio /= 3; }
+
+  }
+
+  if (!just_version) { add_instrumentation(); }
+
+  if (!(pid = fork())) {
+
+    execvp(as_params[0], (char **)as_params);
+    FATAL("Oops, failed to execute '%s' - check your PATH", as_params[0]);
+
+  }
+
+  if (pid < 0) { PFATAL("fork() failed"); }
+
+  if (waitpid(pid, &status, 0) <= 0) { PFATAL("waitpid() failed"); }
+
+  if (!getenv("AFL_KEEP_ASSEMBLY")) { unlink(modified_file); }
+
+  exit(WEXITSTATUS(status));
+
+}
+