/src/php-src/sapi/fuzzer/fuzzer-execute-common.h

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/*
   +----------------------------------------------------------------------+
   | Copyright (c) The PHP Group                                          |
   +----------------------------------------------------------------------+
   | This source file is subject to version 3.01 of the PHP license,      |
   | that is bundled with this package in the file LICENSE, and is        |
   | available through the world-wide-web at the following url:           |
   | https://www.php.net/license/3_01.txt                                 |
   | If you did not receive a copy of the PHP license and are unable to   |
   | obtain it through the world-wide-web, please send a note to          |
   | license@php.net so we can mail you a copy immediately.               |
   +----------------------------------------------------------------------+
   | Authors: Nikita Popov <nikic@php.net>                                |
   +----------------------------------------------------------------------+
 */

#include <main/php.h>

#if defined(__FreeBSD__)
# include <sys/sysctl.h>
#endif

#include "fuzzer.h"
#include "fuzzer-sapi.h"
#include "zend_exceptions.h"

#define FILE_NAME "/tmp/fuzzer.php"
#define MAX_STEPS 1000
#define MAX_SIZE (8 * 1024)
#define ZEND_VM_ENTER_BIT 1ULL

static uint32_t steps_left;
static bool bailed_out = false;

/* Because the fuzzer is always compiled with clang,
 * we can assume that we don't use global registers / hybrid VM. */
typedef zend_op *(ZEND_FASTCALL *opcode_handler_t)(zend_execute_data *, const zend_op *);

static zend_always_inline void fuzzer_bailout(void) {
  bailed_out = true;
  zend_bailout();
}

static zend_always_inline void fuzzer_step(void) {
  if (--steps_left == 0) {
    /* Reset steps before bailing out, so code running after bailout (e.g. in
     * destructors) will get another MAX_STEPS, rather than UINT32_MAX steps. */
    steps_left = MAX_STEPS;
    fuzzer_bailout();
  }
}

static void (*orig_execute_ex)(zend_execute_data *execute_data);

static void fuzzer_execute_ex(zend_execute_data *execute_data) {
  const zend_op *opline = EX(opline);
  while (1) {
    fuzzer_step();
    opline = ((opcode_handler_t) opline->handler)(execute_data, opline);
    if ((uintptr_t) opline & ZEND_VM_ENTER_BIT) {
      opline = (const zend_op *) ((uintptr_t) opline & ~ZEND_VM_ENTER_BIT);
      if (opline) {
        execute_data = EG(current_execute_data);
      } else {
        return;
      }
    }
  }
}

static zend_op_array *(*orig_compile_string)(
    zend_string *source_string, const char *filename, zend_compile_position position);

static zend_op_array *fuzzer_compile_string(
    zend_string *str, const char *filename, zend_compile_position position) {
  if (ZSTR_LEN(str) > MAX_SIZE) {
    /* Avoid compiling huge inputs via eval(). */
    fuzzer_bailout();
  }

  return orig_compile_string(str, filename, position);
}

static void (*orig_execute_internal)(zend_execute_data *execute_data, zval *return_value);

static void fuzzer_execute_internal(zend_execute_data *execute_data, zval *return_value) {
  fuzzer_step();

  uint32_t num_args = ZEND_CALL_NUM_ARGS(execute_data);
  for (uint32_t i = 0; i < num_args; i++) {
    /* Some internal functions like preg_replace() may be slow on large inputs.
     * Limit the maximum size of string inputs. */
    zval *arg = ZEND_CALL_VAR_NUM(execute_data, i);
    if (Z_TYPE_P(arg) == IS_STRING && Z_STRLEN_P(arg) > MAX_SIZE) {
      fuzzer_bailout();
    }
  }

  orig_execute_internal(execute_data, return_value);
}

static void fuzzer_init_php_for_execute(const char *extra_ini) {
  /* Compilation will often trigger fatal errors.
   * Use tracked allocation mode to avoid leaks in that case. */
  putenv("USE_TRACKED_ALLOC=1");

  /* Just like other SAPIs, ignore SIGPIPEs. */
  signal(SIGPIPE, SIG_IGN);

  fuzzer_init_php(extra_ini);

  orig_execute_ex = zend_execute_ex;
  zend_execute_ex = fuzzer_execute_ex;
  orig_execute_internal = zend_execute_internal ? zend_execute_internal : execute_internal;
  zend_execute_internal = fuzzer_execute_internal;
  orig_compile_string = zend_compile_string;
  zend_compile_string = fuzzer_compile_string;
}

ZEND_ATTRIBUTE_UNUSED static void create_file(void) {
  /* For opcache_invalidate() to work, the dummy file name used for fuzzing needs to
   * actually exist. */
  FILE *f = fopen(FILE_NAME, "w");
  fclose(f);
}

ZEND_ATTRIBUTE_UNUSED static void opcache_invalidate(void) {
  steps_left = MAX_STEPS;
  zend_exception_save();
  zval retval, args[2];
  zend_function *fn = zend_hash_str_find_ptr(CG(function_table), ZEND_STRL("opcache_invalidate"));
  ZEND_ASSERT(fn != NULL);

  ZVAL_STRING(&args[0], FILE_NAME);
  ZVAL_TRUE(&args[1]);
  zend_call_known_function(fn, NULL, NULL, &retval, 2, args, NULL);
  ZEND_ASSERT(Z_TYPE(retval) == IS_TRUE);
  zval_ptr_dtor(&args[0]);
  zval_ptr_dtor(&retval);
  zend_exception_restore();
}

ZEND_ATTRIBUTE_UNUSED char *get_opcache_path(void) {
  /* Try relative to cwd. */
  char *p = realpath("modules/opcache.so", NULL);
  if (p) {
    return p;
  }

  /* Try relative to binary location. */
  char path[MAXPATHLEN];
#if defined(__FreeBSD__)
  size_t pathlen = sizeof(path);
  int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
  if (sysctl(mib, 4, path, &pathlen, NULL, 0) < 0) {
#else
  if (readlink("/proc/self/exe", path, sizeof(path)) < 0) {
#endif
    ZEND_ASSERT(0 && "Failed to get binary path");
    return NULL;
  }

  /* Get basename. */
  char *last_sep = strrchr(path, '/');
  if (last_sep) {
    *last_sep = '\0';
  }

  strlcat(path, "/modules/opcache.so", sizeof(path));
  return realpath(path, NULL);
}

Coverage Report

Created: 2025-07-23 06:33