yara.c

/*
Copyright (c) 2007-2013. The YARA Authors. All Rights Reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation and/or
other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its contributors
may be used to endorse or promote products derived from this software without
specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#if !defined(_WIN32) && !defined(__CYGWIN__)

#include <sys/stat.h>
#include <dirent.h>
#include <unistd.h>
#include <inttypes.h>

#else

#include <windows.h>

#define PRIx64 "I64x"
#define PRId64 "I64d"

#endif

#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#include <yara.h>

#include "args.h"
#include "threading.h"
#include "config.h"


#define ERROR_COULD_NOT_CREATE_THREAD  100

#ifndef MAX_PATH
#define MAX_PATH 256
#endif

#ifndef min
#define min(x, y)  ((x < y) ? (x) : (y))
#endif

#ifdef _MSC_VER
#define snprintf _snprintf
#define strdup _strdup
#endif

#define MAX_QUEUED_FILES 64


typedef struct _MODULE_DATA
{
  const char* module_name;
  YR_MAPPED_FILE mapped_file;
  struct _MODULE_DATA* next;

} MODULE_DATA;

typedef struct _THREAD_ARGS
{
  YR_RULES* rules;
  time_t start_time;

} THREAD_ARGS;


typedef struct _QUEUED_FILE {

  char* path;

} QUEUED_FILE;


#define MAX_ARGS_TAG            32
#define MAX_ARGS_IDENTIFIER     32
#define MAX_ARGS_EXT_VAR        32
#define MAX_ARGS_MODULE_DATA    32

char* tags[MAX_ARGS_TAG + 1];
char* identifiers[MAX_ARGS_IDENTIFIER + 1];
char* ext_vars[MAX_ARGS_EXT_VAR + 1];
char* modules_data[MAX_ARGS_EXT_VAR + 1];

int recursive_search = FALSE;
int show_module_data = FALSE;
int show_tags = FALSE;
int show_specified_tags = FALSE;
int show_specified_rules = FALSE;
int show_strings = FALSE;
int show_meta = FALSE;
int show_namespace = FALSE;
int show_version = FALSE;
int show_help = FALSE;
int ignore_warnings = FALSE;
int fast_scan = FALSE;
int negate = FALSE;
int count = 0;
int limit = 0;
int timeout = 1000000;
int stack_size = DEFAULT_STACK_SIZE;
int threads = 8;


#define USAGE_STRING \
    "Usage: yara [OPTION]... RULES_FILE FILE | DIR | PID"


args_option_t options[] =
{
  OPT_STRING_MULTI('t', "tag", &tags, MAX_ARGS_TAG,
      "print only rules tagged as TAG", "TAG"),

  OPT_STRING_MULTI('i', "identifier", &identifiers, MAX_ARGS_IDENTIFIER,
      "print only rules named IDENTIFIER", "IDENTIFIER"),

  OPT_BOOLEAN('n', "negate", &negate,
      "print only not satisfied rules (negate)", NULL),

  OPT_BOOLEAN('D', "print-module-data", &show_module_data,
      "print module data"),

  OPT_BOOLEAN('g', "print-tags", &show_tags,
      "print tags"),

  OPT_BOOLEAN('m', "print-meta", &show_meta,
      "print metadata"),

  OPT_BOOLEAN('s', "print-strings", &show_strings,
      "print matching strings"),

  OPT_BOOLEAN('e', "print-namespace", &show_namespace,
      "print rules' namespace"),

  OPT_INTEGER('p', "threads", &threads,
      "use the specified NUMBER of threads to scan a directory", "NUMBER"),

  OPT_INTEGER('l', "max-rules", &limit,
      "abort scanning after matching a NUMBER of rules", "NUMBER"),

  OPT_STRING_MULTI('d', NULL, &ext_vars, MAX_ARGS_EXT_VAR,
      "define external variable", "VAR=VALUE"),

  OPT_STRING_MULTI('x', NULL, &modules_data, MAX_ARGS_MODULE_DATA,
      "pass FILE's content as extra data to MODULE", "MODULE=FILE"),

  OPT_INTEGER('a', "timeout", &timeout,
      "abort scanning after the given number of SECONDS", "SECONDS"),

  OPT_INTEGER('k', "stack-size", &stack_size,
      "set maximum stack size (default=16384)", "SLOTS"),

  OPT_BOOLEAN('r', "recursive", &recursive_search,
      "recursively search directories"),

  OPT_BOOLEAN('f', "fast-scan", &fast_scan,
      "fast matching mode"),

  OPT_BOOLEAN('w', "no-warnings", &ignore_warnings,
      "disable warnings"),

  OPT_BOOLEAN('v', "version", &show_version,
      "show version information"),

  OPT_BOOLEAN('h', "help", &show_help,
      "show this help and exit"),

  OPT_END()
};


// file_queue is size-limited queue stored as a circular array, files are
// removed from queue_head position and new files are added at queue_tail
// position. The array has room for one extra element to avoid queue_head
// being equal to queue_tail in a full queue. The only situation where
// queue_head == queue_tail is when queue is empty.

QUEUED_FILE file_queue[MAX_QUEUED_FILES + 1];

int queue_head;
int queue_tail;

SEMAPHORE used_slots;
SEMAPHORE unused_slots;

MUTEX queue_mutex;
MUTEX output_mutex;

MODULE_DATA* modules_data_list = NULL;


int file_queue_init()
{
  int result;

  queue_tail = 0;
  queue_head = 0;

  result = mutex_init(&queue_mutex);

  if (result != 0)
    return result;

  result = semaphore_init(&used_slots, 0);

  if (result != 0)
    return result;

 return semaphore_init(&unused_slots, MAX_QUEUED_FILES);
}


void file_queue_destroy()
{
  mutex_destroy(&queue_mutex);
  semaphore_destroy(&unused_slots);
  semaphore_destroy(&used_slots);
}


void file_queue_finish()
{
  int i;

  for (i = 0; i < MAX_THREADS; i++)
    semaphore_release(&used_slots);
}


void file_queue_put(
    const char* file_path)
{
  semaphore_wait(&unused_slots);
  mutex_lock(&queue_mutex);

  file_queue[queue_tail].path = strdup(file_path);
  queue_tail = (queue_tail + 1) % (MAX_QUEUED_FILES + 1);

  mutex_unlock(&queue_mutex);
  semaphore_release(&used_slots);
}


char* file_queue_get()
{
  char* result;

  semaphore_wait(&used_slots);
  mutex_lock(&queue_mutex);

  if (queue_head == queue_tail) // queue is empty
  {
    result = NULL;
  }
  else
  {
    result = file_queue[queue_head].path;
    queue_head = (queue_head + 1) % (MAX_QUEUED_FILES + 1);
  }

  mutex_unlock(&queue_mutex);
  semaphore_release(&unused_slots);

  return result;
}


#if defined(_WIN32) || defined(__CYGWIN__)

int is_directory(
    const char* path)
{
  DWORD attributes = GetFileAttributes(path);

  if (attributes != INVALID_FILE_ATTRIBUTES &&
	  attributes & FILE_ATTRIBUTE_DIRECTORY)
    return TRUE;
  else
    return FALSE;
}

void scan_dir(
    const char* dir,
    int recursive,
    time_t start_time,
    YR_RULES* rules,
    YR_CALLBACK_FUNC callback)
{
  static char path_and_mask[MAX_PATH];

  snprintf(path_and_mask, sizeof(path_and_mask), "%s\\*", dir);

  WIN32_FIND_DATA FindFileData;
  HANDLE hFind = FindFirstFile(path_and_mask, &FindFileData);

  if (hFind != INVALID_HANDLE_VALUE)
  {
    do
    {
      char full_path[MAX_PATH];

      snprintf(full_path, sizeof(full_path), "%s\\%s",
               dir, FindFileData.cFileName);

      if (!(FindFileData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY))
      {
        file_queue_put(full_path);
      }
      else if (recursive &&
               strcmp(FindFileData.cFileName, ".") != 0 &&
               strcmp(FindFileData.cFileName, "..") != 0)
      {
        scan_dir(full_path, recursive, start_time, rules, callback);
      }

    } while (FindNextFile(hFind, &FindFileData));

    FindClose(hFind);
  }
}

#else

int is_directory(
    const char* path)
{
  struct stat st;

  if (stat(path,&st) == 0)
    return S_ISDIR(st.st_mode);

  return 0;
}


void scan_dir(
    const char* dir,
    int recursive,
    time_t start_time,
    YR_RULES* rules,
    YR_CALLBACK_FUNC callback)
{
  DIR* dp = opendir(dir);

  if (dp)
  {
    struct dirent* de = readdir(dp);

    while (de && difftime(time(NULL), start_time) < timeout)
    {
      char full_path[MAX_PATH];
      struct stat st;

      snprintf(full_path, sizeof(full_path), "%s/%s", dir, de->d_name);

      int err = lstat(full_path, &st);

      if (err == 0)
      {
        if(S_ISREG(st.st_mode))
        {
          file_queue_put(full_path);
        }
        else if(recursive &&
                S_ISDIR(st.st_mode) &&
                !S_ISLNK(st.st_mode) &&
                strcmp(de->d_name, ".") != 0 &&
                strcmp(de->d_name, "..") != 0)
        {
          scan_dir(full_path, recursive, start_time, rules, callback);
        }
      }

      de = readdir(dp);
    }

    closedir(dp);
  }
}

#endif

void print_string(
    uint8_t* data,
    int length)
{
  char* str = (char*) (data);

  for (int i = 0; i < length; i++)
  {
    if (str[i] >= 32 && str[i] <= 126)
      printf("%c", str[i]);
    else
      printf("\\x%02X", (uint8_t) str[i]);
  }

  printf("\n");
}


static char cescapes[] =
{
  0  , 0  , 0  , 0  , 0  , 0  , 0  , 'a',
  'b', 't', 'n', 'v', 'f', 'r', 0  , 0  ,
  0  , 0  , 0  , 0  , 0  , 0  , 0  , 0  ,
  0  , 0  , 0  , 0  , 0  , 0  , 0  , 0  ,
};


void print_escaped(
    uint8_t* data,
    size_t length)
{
  size_t i;

  for (i = 0; i < length; i++)
  {
    switch (data[i])
    {
      case '\"':
      case '\'':
      case '\\':
        printf("\\%c", data[i]);
        break;

      default:
        if (data[i] >= 127)
          printf("\\%03o", data[i]);
        else if (data[i] >= 32)
          putchar(data[i]);
        else if (cescapes[data[i]] != 0)
          printf("\\%c", cescapes[data[i]]);
        else
          printf("\\%03o", data[i]);
    }
  }
}


void print_hex_string(
    uint8_t* data,
    int length)
{
  for (int i = 0; i < min(32, length); i++)
    printf("%02X ", (uint8_t) data[i]);

  if (length > 32)
    printf("...");

  printf("\n");
}


void print_scanner_error(
    int error)
{
  switch (error)
  {
    case ERROR_SUCCESS:
      break;
    case ERROR_COULD_NOT_ATTACH_TO_PROCESS:
      fprintf(stderr, "can not attach to process (try running as root)\n");
      break;
    case ERROR_INSUFICIENT_MEMORY:
      fprintf(stderr, "not enough memory\n");
      break;
    case ERROR_SCAN_TIMEOUT:
      fprintf(stderr, "scanning timed out\n");
      break;
    case ERROR_COULD_NOT_OPEN_FILE:
      fprintf(stderr, "could not open file\n");
      break;
    case ERROR_UNSUPPORTED_FILE_VERSION:
      fprintf(stderr, "rules were compiled with a newer version of YARA.\n");
      break;
    case ERROR_CORRUPT_FILE:
      fprintf(stderr, "corrupt compiled rules file.\n");
      break;
    case ERROR_EXEC_STACK_OVERFLOW:
      fprintf(stderr, "stack overflow while evaluating condition "
                      "(see --stack-size argument).\n");
      break;
    case ERROR_INVALID_EXTERNAL_VARIABLE_TYPE:
      fprintf(stderr, "invalid type for external variable.\n");
      break;
    default:
      fprintf(stderr, "internal error: %d\n", error);
      break;
  }
}


void print_compiler_error(
    int error_level,
    const char* file_name,
    int line_number,
    const char* message,
    void* user_data)
{
  if (error_level == YARA_ERROR_LEVEL_ERROR)
  {
    fprintf(stderr, "%s(%d): error: %s\n", file_name, line_number, message);
  }
  else
  {
    if (!ignore_warnings)
      fprintf(stderr, "%s(%d): warning: %s\n", file_name, line_number, message);
  }
}


int handle_message(
    int message,
    YR_RULE* rule,
    void* data)
{
  const char* tag;
  int show = TRUE;

  if (tags[0] != NULL)
  {
    // The user specified one or more -t <tag> arguments, let's show this rule
    // only if it's tagged with some of the specified tags.

    show = FALSE;

    for (int i = 0; !show && tags[i] != NULL; i++)
    {
      yr_rule_tags_foreach(rule, tag)
      {
        if (strcmp(tag, tags[i]) == 0)
        {
          show = TRUE;
          break;
        }
      }
    }
  }

  if (identifiers[0] != NULL)
  {
    // The user specified one or more -i <identifier> arguments, let's show
    // this rule only if it's identifier is among of the provided ones.

    show = FALSE;

    for (int i = 0; !show && identifiers[i] != NULL; i++)
    {
      if (strcmp(identifiers[i], rule->identifier) == 0)
      {
        show = TRUE;
        break;
      }
    }
  }

  int is_matching = (message == CALLBACK_MSG_RULE_MATCHING);

  show = show && ((!negate && is_matching) || (negate && !is_matching));

  if (show)
  {
    mutex_lock(&output_mutex);

    if (show_namespace)
      printf("%s:", rule->ns->name);

    printf("%s ", rule->identifier);

    if (show_tags)
    {
      printf("[");

      yr_rule_tags_foreach(rule, tag)
      {
        // print a comma except for the first tag
        if (tag != rule->tags)
          printf(",");

        printf("%s", tag);
      }

      printf("] ");
    }

    // Show meta-data.

    if (show_meta)
    {
      YR_META* meta;

      printf("[");

      yr_rule_metas_foreach(rule, meta)
      {
        if (meta != rule->metas)
          printf(",");

        if (meta->type == META_TYPE_INTEGER)
        {
          printf("%s=%" PRId64, meta->identifier, meta->integer);
        }
        else if (meta->type == META_TYPE_BOOLEAN)
        {
          printf("%s=%s", meta->identifier, meta->integer ? "true" : "false");
        }
        else
        {
          printf("%s=\"", meta->identifier);
          print_escaped((uint8_t*) (meta->string), strlen(meta->string));
          putchar('"');
        }
      }

      printf("] ");
    }

    printf("%s\n", (char*) data);

    // Show matched strings.

    if (show_strings)
    {
      YR_STRING* string;

      yr_rule_strings_foreach(rule, string)
      {
        YR_MATCH* match;

        yr_string_matches_foreach(string, match)
        {
          printf("0x%" PRIx64 ":%s: ",
              match->base + match->offset,
              string->identifier);

          if (STRING_IS_HEX(string))
            print_hex_string(match->data, match->data_length);
          else
            print_string(match->data, match->data_length);
        }
      }
    }

    mutex_unlock(&output_mutex);
  }

  if (is_matching)
    count++;

  if (limit != 0 && count >= limit)
    return CALLBACK_ABORT;

  return CALLBACK_CONTINUE;
}


int callback(
    int message,
    void* message_data,
    void* user_data)
{
  YR_MODULE_IMPORT* mi;
  YR_OBJECT* object;
  MODULE_DATA* module_data;

  switch(message)
  {
    case CALLBACK_MSG_RULE_MATCHING:
    case CALLBACK_MSG_RULE_NOT_MATCHING:
      return handle_message(message, (YR_RULE*) message_data, user_data);

    case CALLBACK_MSG_IMPORT_MODULE:

      mi = (YR_MODULE_IMPORT*) message_data;
      module_data = modules_data_list;

      while (module_data != NULL)
      {
        if (strcmp(module_data->module_name, mi->module_name) == 0)
        {
          mi->module_data = module_data->mapped_file.data;
          mi->module_data_size = module_data->mapped_file.size;
          break;
        }

        module_data = module_data->next;
      }

      return CALLBACK_CONTINUE;

    case CALLBACK_MSG_MODULE_IMPORTED:

      if (show_module_data)
      {
        object = (YR_OBJECT*) message_data;

        mutex_lock(&output_mutex);

        yr_object_print_data(object, 0, 1);
        printf("\n");

        mutex_unlock(&output_mutex);
      }

      return CALLBACK_CONTINUE;
  }

  return CALLBACK_ERROR;
}


#if defined(_WIN32) || defined(__CYGWIN__)
DWORD WINAPI scanning_thread(LPVOID param)
#else
void* scanning_thread(void* param)
#endif
{
  int result = ERROR_SUCCESS;
  THREAD_ARGS* args = (THREAD_ARGS*) param;
  char* file_path = file_queue_get();

  int flags = 0;

  if (fast_scan)
    flags |= SCAN_FLAGS_FAST_MODE;

  while (file_path != NULL)
  {
    int elapsed_time = (int) difftime(time(NULL), args->start_time);

    if (elapsed_time < timeout)
    {
      result = yr_rules_scan_file(
          args->rules,
          file_path,
          flags,
          callback,
          file_path,
          timeout - elapsed_time);

      if (result != ERROR_SUCCESS)
      {
        mutex_lock(&output_mutex);
        fprintf(stderr, "error scanning %s: ", file_path);
        print_scanner_error(result);
        mutex_unlock(&output_mutex);
      }

      free(file_path);
      file_path = file_queue_get();
    }
    else
    {
      file_path = NULL;
    }
  }

  yr_finalize_thread();

  return 0;
}


int is_integer(
    const char *str)
{
  if (*str == '-')
    str++;

  while(*str)
  {
    if (!isdigit(*str))
      return FALSE;
    str++;
  }

  return TRUE;
}


int is_float(
    const char *str)
{
  int has_dot = FALSE;

  if (*str == '-')      // skip the minus sign if present
    str++;

  if (*str == '.')      // float can't start with a dot
    return FALSE;

  while(*str)
  {
    if (*str == '.')
    {
      if (has_dot)      // two dots, not a float
        return FALSE;

      has_dot = TRUE;
    }
    else if (!isdigit(*str))
    {
      return FALSE;
    }

    str++;
  }

  return has_dot; // to be float must contain a dot
}


int define_external_variables(
    YR_RULES* rules,
    YR_COMPILER* compiler)
{
  int result = ERROR_SUCCESS;

  for (int i = 0; ext_vars[i] != NULL; i++)
  {
    char* equal_sign = strchr(ext_vars[i], '=');

    if (!equal_sign)
    {
      fprintf(stderr, "error: wrong syntax for `-d` option.\n");
      return ERROR_SUCCESS;
    }

    // Replace the equal sign with null character to split the external
    // variable definition (i.e: myvar=somevalue) in two strings: identifier
    // and value.

    *equal_sign = '\0';

    char* identifier = ext_vars[i];
    char* value = equal_sign + 1;

    if (is_float(value))
    {
      if (rules != NULL)
        result = yr_rules_define_float_variable(
            rules,
            identifier,
            atof(value));

      if (compiler != NULL)
        result = yr_compiler_define_float_variable(
            compiler,
            identifier,
            atof(value));
    }
    else if (is_integer(value))
    {
      if (rules != NULL)
        result = yr_rules_define_integer_variable(
            rules,
            identifier,
            atoi(value));

      if (compiler != NULL)
        result = yr_compiler_define_integer_variable(
            compiler,
            identifier,
            atoi(value));
    }
    else if (strcmp(value, "true") == 0 || strcmp(value, "false") == 0)
    {
      if (rules != NULL)
        result = yr_rules_define_boolean_variable(
            rules,
            identifier,
            strcmp(value, "true") == 0);

      if (compiler != NULL)
        result = yr_compiler_define_boolean_variable(
            compiler,
            identifier,
            strcmp(value, "true") == 0);
    }
    else
    {
      if (rules != NULL)
        result = yr_rules_define_string_variable(
            rules,
            identifier,
            value);

      if (compiler != NULL)
        result = yr_compiler_define_string_variable(
            compiler,
            identifier,
            value);
    }
  }

  return result;
}


int load_modules_data()
{
  for (int i = 0; modules_data[i] != NULL; i++)
  {
    char* equal_sign = strchr(modules_data[i], '=');

    if (!equal_sign)
    {
      fprintf(stderr, "error: wrong syntax for `-x` option.\n");
      return FALSE;
    }

    *equal_sign = '\0';

    MODULE_DATA* module_data = (MODULE_DATA*) malloc(sizeof(MODULE_DATA));

    if (module_data != NULL)
    {
      module_data->module_name = modules_data[i];

      int result = yr_filemap_map(equal_sign + 1, &module_data->mapped_file);

      if (result != ERROR_SUCCESS)
      {
        free(module_data);
        fprintf(stderr, "error: could not open file \"%s\".\n", equal_sign + 1);
        return FALSE;
      }

      module_data->next = modules_data_list;
      modules_data_list = module_data;
    }
  }

  return TRUE;
}


void unload_modules_data()
{
  MODULE_DATA* module_data = modules_data_list;

  while(module_data != NULL)
  {
    MODULE_DATA* next_module_data = module_data->next;

    yr_filemap_unmap(&module_data->mapped_file);
    free(module_data);

    module_data = next_module_data;
  }

  modules_data_list = NULL;
}


#define exit_with_code(code) { result = code; goto _exit; }

int main(
    int argc,
    const char** argv)
{
  YR_COMPILER* compiler = NULL;
  YR_RULES* rules = NULL;

  int result, i;

  argc = args_parse(options, argc, argv);

  if (show_version)
  {
    printf("%s\n", PACKAGE_STRING);
    return EXIT_SUCCESS;
  }

  if (show_help)
  {
    printf(
      "YARA %s, the pattern matching swiss army knife.\n"
      "%s\n\n"
      "Mandatory arguments to long options are mandatory for "
      "short options too.\n\n", PACKAGE_VERSION, USAGE_STRING);

    args_print_usage(options, 35);
    printf("\nSend bug reports and suggestions to: %s.\n", PACKAGE_BUGREPORT);

    return EXIT_SUCCESS;
  }

  if (threads > MAX_THREADS)
  {
    fprintf(stderr, "maximum number of threads is %d\n", MAX_THREADS);
    return EXIT_FAILURE;
  }

  if (argc != 2)
  {
    // After parsing the command-line options we expect two additional
    // arguments, the rules file and the target file, directory or pid to
    // be scanned.

    fprintf(stderr, "yara: wrong number of arguments\n");
    fprintf(stderr, "%s\n\n", USAGE_STRING);
    fprintf(stderr, "Try `--help` for more options\n");

    return EXIT_FAILURE;
  }

  if (!load_modules_data())
    exit_with_code(EXIT_FAILURE);

  result = yr_initialize();

  if (result != ERROR_SUCCESS)
  {
    fprintf(stderr, "error: initialization error (%d)\n", result);
    exit_with_code(EXIT_FAILURE);
  }

  if (stack_size != DEFAULT_STACK_SIZE)
  {
    // If the user chose a different stack size than default,
    // modify the yara config here.

    yr_set_configuration(YR_CONFIG_STACK_SIZE, &stack_size);
  }

  // Try to load the rules file as a binary file containing
  // compiled rules first

  result = yr_rules_load(argv[0], &rules);

  // Accepted result are ERROR_SUCCESS or ERROR_INVALID_FILE
  // if we are passing the rules in source form, if result is
  // different from those exit with error.

  if (result != ERROR_SUCCESS &&
      result != ERROR_INVALID_FILE)
  {
    print_scanner_error(result);
    exit_with_code(EXIT_FAILURE);
  }

  if (result == ERROR_SUCCESS)
  {
    result = define_external_variables(rules, NULL);

    if (result != ERROR_SUCCESS)
    {
      print_scanner_error(result);
      exit_with_code(EXIT_FAILURE);
    }
  }
  else
  {
    // Rules file didn't contain compiled rules, let's handle it
    // as a text file containing rules in source form.

    if (yr_compiler_create(&compiler) != ERROR_SUCCESS)
      exit_with_code(EXIT_FAILURE);

    result = define_external_variables(NULL, compiler);

    if (result != ERROR_SUCCESS)
    {
      print_scanner_error(result);
      exit_with_code(EXIT_FAILURE);
    }

    yr_compiler_set_callback(compiler, print_compiler_error, NULL);

    FILE* rule_file = fopen(argv[0], "r");

    if (rule_file == NULL)
    {
      fprintf(stderr, "error: could not open file: %s\n", argv[0]);
      exit_with_code(EXIT_FAILURE);
    }

    int errors = yr_compiler_add_file(compiler, rule_file, NULL, argv[0]);

    fclose(rule_file);

    if (errors > 0)
      exit_with_code(EXIT_FAILURE);

    result = yr_compiler_get_rules(compiler, &rules);

    yr_compiler_destroy(compiler);

    compiler = NULL;

    if (result != ERROR_SUCCESS)
      exit_with_code(EXIT_FAILURE);
  }

  mutex_init(&output_mutex);

  if (is_integer(argv[1]))
  {
    int pid = atoi(argv[1]);
    int flags = 0;

    if (fast_scan)
      flags |= SCAN_FLAGS_FAST_MODE;

    result = yr_rules_scan_proc(
        rules,
        pid,
        flags,
        callback,
        (void*) argv[1],
        timeout);

    if (result != ERROR_SUCCESS)
    {
      print_scanner_error(result);
      exit_with_code(EXIT_FAILURE);
    }
  }
  else if (is_directory(argv[1]))
  {
    if (file_queue_init() != 0)
    {
      print_scanner_error(ERROR_INTERNAL_FATAL_ERROR);
      exit_with_code(EXIT_FAILURE);
    }

    THREAD thread[MAX_THREADS];
    THREAD_ARGS thread_args;

    time_t start_time = time(NULL);

    thread_args.rules = rules;
    thread_args.start_time = start_time;

    for (i = 0; i < threads; i++)
    {
      if (create_thread(&thread[i], scanning_thread, (void*) &thread_args))
      {
        print_scanner_error(ERROR_COULD_NOT_CREATE_THREAD);
        exit_with_code(EXIT_FAILURE);
      }
    }

    scan_dir(
        argv[1],
        recursive_search,
        start_time,
        rules,
        callback);

    file_queue_finish();

    // Wait for scan threads to finish
    for (i = 0; i < threads; i++)
      thread_join(&thread[i]);

    file_queue_destroy();
  }
  else
  {
    int flags = 0;

    if (fast_scan)
      flags |= SCAN_FLAGS_FAST_MODE;

    result = yr_rules_scan_file(
        rules,
        argv[1],
        flags,
        callback,
        (void*) argv[1],
        timeout);

    if (result != ERROR_SUCCESS)
    {
      fprintf(stderr, "error scanning %s: ", argv[1]);
      print_scanner_error(result);
      exit_with_code(EXIT_FAILURE);
    }
  }

  #ifdef PROFILING_ENABLED
  yr_rules_print_profiling_info(rules);
  #endif

  result = EXIT_SUCCESS;

_exit:

  unload_modules_data();

  if (compiler != NULL)
    yr_compiler_destroy(compiler);

  if (rules != NULL)
    yr_rules_destroy(rules);

  yr_finalize();

  return result;
}