dnsmule 0.1.0

Rule based dependency scanning and service fingerprinting via DNS

DNSMule

Package for rule based dependency scanning and service fingerprinting via DNS.

This package provides utilities for writing and evaluating verbose and easy to read rule definitions in YAML-format. There are two builtin rule formats with more available as plugins.

Current State

States (Complete, Testing, Developing, Refining) for every feature planned at this moment.

• (Complete) Backends
  • (Complete) DNSPythonBackend
  • (Complete) YAML definition
• (Complete) Rules
  • (Complete) Builtin types
  • (Complete) Custom rules
  • (Complete) Custom rule factories
  • (Complete) YAML definition
• (Testing) Plugins
  • (Complete) Registration in program
  • (Complete) Registration in YAML
  • (Complete) YAML definition
  • (Developing) Increasing test coverage
• (Refining) Result Storage
  • (Refining) Registration in program
  • (Refining) Registration in YAML
  • (Refining) YAML definition
• (Developing) DNSMule
  • (Complete) Rules from YAML
  • (Complete) Backend from YAML
  • (Testing) Plugins from YAML
  • (Developing) Processing and gathering results
  • (Refining) Result storage
  • (Refining) Result storage from YAML
  • (Refining) Combined YAML definition

Example server

The repo has a Dockerfile for easily running the tool using an example server in Docker:

$ ./build-image
$ ./run-server

Notice

This package is under active development.

Additional

• RnD Scripts under scripts
• Example server under server

Rules

Summary

The tool configuration is done through one or multiple rule configuration files. The file structure is defined in the schema file. In addition to some builtin rule types, it is possible to create new types by registering handlers or rules programmatically.

Rules support registration per DNS record type and priority for controlling invocation order.

version: '0.0.1'
rules:
  - o365:
    priority: 10
    type: dns.regex
    record: txt
    pattern: '^MS=ms'
    identification: MICROSOFT::O365
  - ses:
    type: dns.regex
    record: txt
    pattern: '^amazonses:'
    identification: AMAZON::SES

Example

from dnsmule.definitions import Record, Result
from dnsmule.rules import Rules, Rule

rules: Rules

...


@rules.add.A[10]
async def my_scan(record: Record) -> Result:
    from dnsmule.config import get_logger
    get_logger().info('Address %s', record)
    return record.identify('MY::SCAN')


@rules.register('my.rule')
def create_my_rule(**arguments) -> Rule:
    ...

Here the add is used to directly register a new rule into the ruleset with a given priority. The register call creates a new handler for rules of type my.rule. Any future my.rule creations from yml or code would be routed to this factory function.

Editor Support

Type Hints and JSON Schema (IntelliJ IDEA, PyCharm, etc.)

It is possible to register the schema file as a custom JSON schema in IntelliJ editors. This will give access to typehints and schema validation inside rule files and is especially nice for dynamic rule definitions as you get full editor features for python inside the snippets.

• settings...
• Languages & Frameworks > Schemas and DTDs > JSON Schema Mappings
• Add a new mapping with the schema file and specified file or pattern

This is configured in the schema using the custom intellij language injection tag:

x-intellij-language-injection:
  language: Python
  prefix: |+0
    from dnsmule.rules.entities import Type, Record, Result

    def add_rule(record_type: Any, rule_type: str, name: str, priority: int = 0, **options) -> None:
        pass

  suffix: ''

Currently, this supports dns.regex pattern regex language injection and dns.dynamic rule code language injection. Type hints and quick documentation are available.

Builtin types

Regex rules

Regex rules can be defined with either one pattern or multiple patterns. An example is in the following snippet:

rules:
  - test:
    type: dns.regex
    record: txt
    pattern: '^.*\.hello_world\.'
    identification: HELLO::WORLD
    flags:
      - UNICODE
      - DOTALL
  - generic_verification:
    type: dns.regex
    record: txt
    priority: 10
    name: Generic Site Regex Collection
    patterns:
      - '^(.+)(?:-(?:site|domain))?-verification='
      - '^(.+)(?:site|domain)verification'
      - '^(.+)_verify_'
      - '^(\w+)-code:'
    group: 1

The full definition is available from the schema file.

Dynamic Rules

Dynamic rules are defined as code snippets with one or two methods

An init method that is invoked once after creation

def init() -> None:
    add_rule(...)

A process function that is invoked once for each record

def process(record: Record) -> Result:
    add_rule(...)
    return record.result()

Both of these functions have access to the following rule creation method:

def add_rule(
        record_type: Any,
        rule_type: str,
        name: str,
        priority: int = 0,
        **options,
) -> None:
    """
    :param record_type: Valid DNS record type as text, int, or type
    :param rule_type:   Valid rule type factory e.g. dns.regex
    :param name:        Name of the created rule
    :param priority:    Priority for the created rule, default 0
    :param options:     Any additional options for the rule factory
    """
    pass

The only globals passed to these methods are:

• __builtins__
• from dnsmule.definitions import RRType, Record, Result, Rule, DynamicRule
• add_rule
• Any additional globals created by the code itself

When the code is exec'd the result is inspected for:

• init function without parameters
• process function with a single parameter

Some notes:

• The init function is invoked exactly once.
• The process function is invoked exactly once for every single Record.
• Any rules created from the init method will be invoked for every suitable record.
• Any rules created from the process method will be invoked for suitable records found after creation.
• Creating DynamicRules from init or process is considered undefined behaviour and care should be taken
  • The user should call init manually and include fail-safes for only calling it once
  • The add_rule callback might not be available so you need to pass it manually to the rule