from __future__ import print_function
from argparse import ArgumentParser, ArgumentDefaultsHelpFormatter
import os
import csv
import yara

"""
MIT License

Copyright (c) 2017 Chapin Bryce, Preston Miller

Please share comments and questions at:
    https://github.com/PythonForensics/PythonForensicsCookbook
    or email pyforcookbook@gmail.com

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
"""

__authors__ = ["Chapin Bryce", "Preston Miller"]
__date__ = 20170815
__description__ = "Utility to scan for matching patterns within files"


def process_directory(yrules, folder_path):
    match_info = []
    for root, _, files in os.walk(folder_path):
        for entry in files:
            file_entry = os.path.join(root, entry)
            match_info += process_file(yrules, file_entry)
    return match_info


def process_file(yrules, file_path):
    match = yrules.match(file_path)
    match_info = []
    for rule_set in match:
        for hit in rule_set.strings:
            match_info.append({
                'file_name': file_path,
                'rule_name': rule_set.rule,
                'rule_tag': ",".join(rule_set.tags),
                'hit_offset': hit[0],
                'rule_string': hit[1],
                'hit_value': hit[2]
            })
    return match_info


def write_csv(outfile, fieldnames, data):
    with open(outfile, 'w', newline="") as open_outfile:
        csvfile = csv.DictWriter(open_outfile, fieldnames)
        csvfile.writeheader()
        csvfile.writerows(data)


def write_stdout(columns, match_info):
    for entry in match_info:
        for col in columns:
            print("{}: {}".format(col, entry[col]))
        print("=" * 30)


def main(yara_rules, path_to_scan, output):
    if os.path.isdir(yara_rules):
        yrules = yara.compile(yara_rules)
    else:
        yrules = yara.compile(filepath=yara_rules)

    if os.path.isdir(path_to_scan):
        match_info = process_directory(yrules, path_to_scan)
    else:
        match_info = process_file(yrules, path_to_scan)

    columns = ['rule_name', 'hit_value', 'hit_offset', 'file_name',
               'rule_string', 'rule_tag']

    if output is None:
        write_stdout(columns, match_info)
    else:
        write_csv(output, columns, match_info)


if __name__ == '__main__':
    parser = ArgumentParser(
        description=__description__,
        formatter_class=ArgumentDefaultsHelpFormatter,
        epilog="Developed by {} on {}".format(
            ", ".join(__authors__), __date__)
    )
    parser.add_argument(
        'yara_rules',
        help="Path to Yara rule to scan with. May be file or folder path.")
    parser.add_argument(
        'path_to_scan',
        help="Path to file or folder to scan")
    parser.add_argument(
        '--output',
        help="Path to output a CSV report of scan results")
    args = parser.parse_args()

    main(args.yara_rules, args.path_to_scan, args.output)