Etherblob-Explorer - Search And Extract Blob Files On The Ethereum Blockchain Network

Etherblob-Explorer – Search And Extract Blob Files On The Ethereum Blockchain Network

[*]

Search and extract blob files on the Ethereum network using Etherscan.io API.

Introduction

EtherBlob Explorer is a tool intended for researchers, analysts, CTF players or anyone curious enough wanting to search for different kinds of files or any meaningful human-supplied data on the Ethereum Blockchain Network. It searches over a user-supplied range of block IDs or UNIX timestamps on any of the 5 available networks: MainNet, Görli, Kovan, Rinkeby and Ropsten.

For a real-life case you can read this experiment made on 2017. The immutability of the blockchain can truly be a double-edged sword.

Installation

Run the following command:

$ pip install git+https://github.com/litneet64/etherblob-explorer.git

Now it’s ready to use from your CLI, you can find some common usage examples below!

Features
Networks

Search on any of the five Ethereum Networks:

  • MainNet
  • Görli
  • Kovan
  • Rinkeby
  • Ropsten

Search Locations

This tool can search on the following locations, either separately or combining any of these on the same run:

  • Transaction Input Data: search inside transaction’s input data (default location).
  • Block Input Data: search inside block’s input data.
  • Contract Storage: search inside a contract’s storage array on the first N 32-byte sized positions, treating it all as one big data string.
  • To Addresses: search appending ‘to’ addresses as the possible input [*] (checking first for file headers and re-checking when all data is harvested using binwalk).

[*] Storing data on ‘to’ addresses is possible on the Ethereum network as there’s no verification if sending to an address that has no associated account keys. Meaning you can make transactions to arbitrary addresses to craft a payload over several 20-byte sized transactions (it’s very rare but so are some CTF challenges).

Search and Extraction Methods

All of these methods can be used either separately or in any combination:

  • Embedded Files: search for files embedded inside data using binwalk.
  • File Headers / Magic Bytes: search using headers + magic bytes via levaraging the Linux util file (default method).
  • ASCII String Dump: search for ASCII strings inside data.
  • Entropy-Based Search: use Shannon’s Entropy as a measure tool to search for natural language text (e.g. UTF-8 Unicode), encrypted/compressed files or anything the user seems viable with user-supplied entropy limits.

IMPORTANT: The order showed here is used under-the-hood for discarding searches with other methods (e.g. if file is found via embedded files then it won’t attempt to search using file headers, ascii string dump nor entropy) as it’s not likely to find anything meaningful if previous methods were already successful.

Misc

  • Accepts UNIX timestamps (instead of block IDs) that get resolved into the closest block IDs commited at those times.
  • Save all data from visited transactions into file for later reviewing.
  • Store CLI-displayed logs into file for later extracted-file analysis.
  • Ignore user-supplied file formats (case-insensitive) for extraction and accepts substrings of the complete file format for blacklisting.
  • Print general progress metrics (e.g. how many blocks / transactions have been parsed, how many blocks are left) every minute and also display some interesting metrics at the end of the current run.
  • More useful features found on the manual (-h)!

Usage

Common use cases

  • Standard search (search inside transactions via file headers) on MainNet with API key on default location (.api-key) and between these two block IDs (inclusive):
$ etherblob 4081599 4081600
  • More “in-through” search (search for embedded files + regular search method) on goerli network with key inside arbitrary file:
$ etherblob -K api.key 3134050 3145570 -M -H --network goerli
  • Search over block headers and transactions at the same time and save extracted files to ‘extracted’:
$ etherblob 4081599 4081600 --blocks --transactions -D extracted/
  • Search only inside ‘to’ addresses in range from blocks commited between Jan 25 2021 19:00:00 and Jan 26 2021 19:00:00:
$ etherblob -t 1611601200 1611687600 --addresses
  • Search strings only on contracts’ storage and for the first 4 storage array positions (128 bytes worth of data):
$ etherblob 3911697 3912697 -S --contracts -C 4
  • Search only inside transactions for encrypted/compressed data (ignoring any other file format):
$ etherblob 4081599 4081600 --encrypted
  • Search inside transactions for custom entropy files while saving transactions into file:
$ etherblob  3911697 3912697 -E 4.0 5.0 -s
  • Only dump ASCII strings over blocks and transactions made on Christmas Eve (between the 24th and 25th):
$ etherblob -t 1608836400 1608922800 --blocks --transactions --strings
  • Full-blown search (slow, expect many false-positives):
$ etherblob 4081599 4081600 -U -S -M -H --blocks --transactions --addresses --contracts

Advanced Use Cases

There are more explanations for advanced usage cases and the things found with them on the wiki!

Manual

usage: etherblob [-h] [--transactions] [--blocks] [--addresses] [--contracts]
[--network {main,goerli,kovan,rinkeby,ropsten}] [-H] [-M] [-U] [-E CUSTOM_ENTROPY CUSTOM_ENTROPY]
[--encrypted] [-S] [-C CONTRACT_POSITION] [-t] [-K API_KEY_PATH] [-k API_KEY] [-D OUTPUT_DIR]
[-o OUT_LOG] [-s] [-i [IGNORED_FMT [IGNORED_FMT ...]]] [--version]
start_block end_block

Tool to search and extract blob files on the Ethereum Network.

positional arguments:
start_block Start of block id range.
end_block End of block id range.

optional arguments:
-h, --help show this help message and exit
--transactions Search for blob files on transaction inputs. Default search mode.
--blocks Search for blob files on block inputs. If enabled then transaction input check is disabled unless
explicitly enabled.
--addresses Search for blob files on 'to' transaction addresses, as on Ethereum anyone can make transactions
to an arbitrary address even if it has no related owner (still not very common). If enabled then
transaction's input check is disabled unless explicitly enabled.
--contracts Search for blob files on contract's storage. If enabled then transaction input check is disabled
unless explicitly enabled.
--network {main,goerli,kovan,rinkeby,ropsten}, -N {main,goerli,kovan,rinkeby,ropsten}
Choose blockchain network to search in. Available choices are Main, Goerli (Görli), Kovan, Rinkeby
and Ropsten. MainNet is the default network. Case-insensitive.
-H, --file-header If enabled, search for file formats via magic bytes/file headers on data (from blocks,
transactions or addresses). Enabled by default unless another method is enabled too.
-M, --embedded If enabled, search for embedded files on data (from blocks, transactions or addresses) via
binwalk. Disabled by default as parsing now takes longer.
-U, --unicode If enabled, attempt to search and dump files containing UTF-8 text from harvested data (blocks,
transactions, addresses) using Shannon's Entropy (between 3.5 and 5.0) if no other discernible
file is found first on that data. Yields many false positives.
-E CUSTOM_ENTROPY CUSTOM_ENTROPY, --custom-entropy CUSTOM_ENTROPY CUSTOM_ENTROPY
Define your own entropy limits (min and max) to search for files/data on harvested data.
--encrypted If enabled, attempt to sear ch and dump encrypted/compressed data found via different search
methods (blocks, transactions, addresses) using Shannon's Entropy (between 7.0 and 8.0) if no
other discernible file is found first on that data.
-S, --strings If enabled, attempt to search and dump ASCII strings into files found inside harvested data
(blocks, transactions, addresses) if no other discernible file is found first on that data.
-C CONTRACT_POSITION, --contract-position CONTRACT_POSITION
Search inside contract's data until reaching the (N-1)th position on its storage array. Positions
contain 32 bytes worth of data. Count starts at 0 and default pos is the 15th pos (16 indexes in
total) if no custom position is given.
-t, --timestamps If enabled, then start and end block IDs are interpreted as UNIX timestamps th at are then resolved
to the closest commited blocks for those specific times.
-K API_KEY_PATH, --api-key-path API_KEY_PATH
Path to file with Etherscan API key for queries. Default search location is '.api-key'.
-k API_KEY, --api-key API_KEY
Etherscan API key as parameter. If given then '--api-key-path' is ignored.
-D OUTPUT_DIR, --output-dir OUTPUT_DIR
Out-dir for extracted files. Default is 'ext_{start block}-{end block}'.
-o OUT_LOG, --out-log OUT_LOG
Out-file for logs. Default is 'etherblob_{start block}-{end block}.log'.
-s, --save-transactions
If enabled, all transactions and their info are stored at file 'transactions_{start-block}-{end-
block}.txt'
-i [IGNORED_FMT [IGNORED_FMT ...]], --ignored-fmt [IGNORED_FMT [IGNORED_FMT ...]]
Ignored file formats for extraction. Default ignored/common file formats are 'ISO-8859 text' and
'Non-ISO extended-ASCII text'. The 'data' file format is always ignored. Accepts file format
substrings and makes case-insensitive matches. '*' is a wildcard to ignore all file formats.
--version show program's version number and exit

Official GitHub repo 'https://github.com/litneet64/etherblob-explorer'

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