yarabuilder

Python module to create Yara rules.

Installation

yarabuilder requires Python 3+:

pip install yarabuilder

Usage

Creating and printing a rule

>>> import yarabuilder
>>> import pprint
>>>
>>> yara_builder = yarabuilder.YaraBuilder()
>>>
>>> yara_builder.create_rule("my_rule")
>>> yara_builder.add_meta("my_rule", "description", "Generated by yarabuilder")
>>> yara_builder.add_import("my_rule", "pe")
>>> yara_builder.add_tag("my_rule", "yarabuilder")
>>> yara_builder.add_text_string("my_rule", "Anonymous string")
>>> yara_builder.add_text_string("my_rule", "Named string", name="str", modifiers=["ascii", "wide"])
>>> yara_builder.add_string_comment("my_rule", "str", "example comment")
>>> yara_builder.add_hex_string("my_rule", "DE AD BE EF")
>>> yara_builder.add_regex_string("my_rule", "regex[0-9]{2}")
>>> yara_builder.add_regex_string("my_rule", "/regex_with_flags/i")
>>> yara_builder.add_condition("my_rule", "any of them")
>>>
>>> rule = yara_builder.build_rules()
>>> print(rule)
import "pe"

rule my_rule : yarabuilder {
    meta:
        description = "Generated by yarabuilder"

    strings:
        $ = "Anonymous string"
        $str = "Named string" ascii wide // example comment
        $ = {DE AD BE EF}
        $ = /regex[0-9]{2}/
        $ = /regex_with_flags/i

    condition:
        any of them
}
>>>

Converting a YaraBuilder object to lists and dictionaries (and back again)

>>> dict_yara_rules = yara_builder.get_yara_rules()
>>> pprint.pprint(dict_yara_rules)
[{'condition': 'any of them',
'imports': ['pe'],
'meta': OrderedDict([('description',
                        [{'meta_type': 'text',
                        'name': 'description',
                        'position': 0,
                        'value': 'Generated by yarabuilder'}])]),
'rule_name': 'my_rule',
'strings': OrderedDict([('@anon0',
                        {'is_anonymous': True,
                            'name': '@anon0',
                            'str_type': 'text',
                            'value': 'Anonymous string'}),
                        ('str',
                        {'comment': {'inline': 'example comment'},
                            'is_anonymous': False,
                            'modifiers': ['ascii', 'wide'],
                            'name': 'str',
                            'str_type': 'text',
                            'value': 'Named string'}),
                        ('@anon1',
                        {'is_anonymous': True,
                            'name': '@anon1',
                            'str_type': 'hex',
                            'value': 'DE AD BE EF'}),
                        ('@anon2',
                        {'is_anonymous': True,
                            'name': '@anon2',
                            'str_type': 'regex',
                            'value': 'regex[0-9]{2}'}),
                        ('@anon3',
                        {'is_anonymous': True,
                            'name': '@anon3',
                            'regex_flags': 'i',
                            'str_type': 'regex',
                            'value': 'regex_with_flags'})]),
'tags': ['yarabuilder']}]
>>>
>>> new_builder = yarabuilder.YaraBuilder()
>>> new_builder.set_yara_rules(dict_yara_rules)
>>>

TODO

• More logging in the classes
• Add optional validation for building YARA rules (e.g. checking imports are valid, and more longer term check the condition is valid)