/*

   +----------------------------------------------------------------------+

   | 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;

}