A quick and short python script to deobfuscate JNDI payloads that are used in log4j exploitation which leverage on default value assignment, character manipulation syntaxes & other methods, licensed under GNU LGPLv3

JNDIPayloadDeobfuscator.py

import re

class DeobfuscatorException(Exception):
    """
    DeobfuscatorException class to be raised
    """
    pass

class JNDIPayloadDeobfuscator:

    def __init__(self, payload: str = None) -> None:
        """
        JNDIPayloadDeobfuscator class constructor

                Args:
                    payload (str): Raw JNDI payload string

                Returns:
                    None
                    
                Raises:
                    DeobfuscatorException: If `payload` is empty or invalid
        """
        if not payload or len(payload) == 0:
            raise DeobfuscatorException('Payload cannot be empty')

        if not payload.startswith('${'):
            raise DeobfuscatorException('Payload does not seem to be a JNDI lookup string')

        self.payload = payload

    def _deobfuscate(self, payload: str) -> str:
        """
        JNDI string deobfuscator function

                Args:
                    payload (str): Raw JNDI payload string

                Returns:
                    result (str): The deobfuscated JNDI string
        """
        result = payload
        matches = re.findall('\$\{(?:[^{}])*\}', payload)
        for match in matches:
            inner = re.search('\$\{(.*)\}', match).group(1)
            if ':-' in inner:
                result = payload.replace(match, inner.split(':-', 1)[-1])
            elif inner.startswith('upper'):
                result = payload.replace(match, inner.split(':', 1)[-1].upper())
            elif inner.startswith('lower'):
                result = payload.replace(match, inner.split(':', 1)[-1].lower())
            elif inner.startswith('date'):
                result = payload.replace(match, inner.split(':', 1)[-1].replace("'", ""))
            else:
                break
        return result

    def get_deobfuscated(self) -> str:
        """
        Returns the fully deobfuscated JNDI string

                Args:
                    None

                Returns:
                    result (str): The fully deobfuscated JNDI string
        """
        for _ in range(self.payload.count('$')):
            self.payload = self._deobfuscate(self.payload)

        result = self.payload

        if '://' not in result:
            return result

        raw_host = result.split('://')[1].split('/')[0]

        if '#' in result and len(raw_host.split('#')) > 1:
            host = raw_host.split('#')[1]

            return result.replace(raw_host, host)
        else:
            return result

LICENSE

                   GNU LESSER GENERAL PUBLIC LICENSE
                       Version 3, 29 June 2007

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