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

Source
/*
   +----------------------------------------------------------------------+
   | Copyright © The PHP Group and Contributors.                          |
   +----------------------------------------------------------------------+
   | This source file is subject to the Modified BSD License that is      |
   | bundled with this package in the file LICENSE, and is available      |
   | through the World Wide Web at <https://www.php.net/license/>.        |
   |                                                                      |
   | SPDX-License-Identifier: BSD-3-Clause                                |
   +----------------------------------------------------------------------+
   | 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"
#include "zend_vm.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;

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) {

#ifdef ZEND_CHECK_STACK_LIMIT
  if (UNEXPECTED(zend_call_stack_overflowed(EG(stack_limit)))) {
    zend_call_stack_size_error();
    /* No opline was executed before exception */
    EG(opline_before_exception) = NULL;
    /* Fall through to handle exception below. */
  }
#endif /* ZEND_CHECK_STACK_LIMIT */

  const zend_op *opline = EX(opline);

  while (1) {
    fuzzer_step();
    opline = ((zend_vm_opcode_handler_func_t) zend_get_opcode_handler_func(opline))(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_object *exception = EG(exception);
  EG(exception) = NULL;
  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);
  EG(exception) = exception;
}

Coverage Report

Created: 2026-06-13 07:01