Passwords cracking

Password cracking is the process of recovering passwords from data that have been stored in or transmitted in a hashed form by a computer system.

Passwords cracking can be attempted using a:

  • Brute-force attack, in which all possible passwords are exhaustively tried. Past a certain password length and complexity, brute force attack become ineffective

  • Dictionary attack rely on a wordlist to guess passwords

  • Rainbow table attack use a precomputed table of hashes reducing the computer processing time required

The time to crack a password is related to the password strength and the hashing function used.

Wordlist

The following word list can be used for passwords cracking:

NameEntry countDescription

darkweb2017-top

10/100/1000/10000

Top X passwords.

rockyou.txt

14 millions

Usually considered sufficient for any CTF purpose, coupled if necessary with cracking rules.

CrackStation’s 15GB

1.5 billion

The publicly available most complete password wordlist to date.

kwprocessor

kwprocessor is a keyboard-walk generator utility, with configurable basechars, keymap and routes. Keyboard-walk sequences correspond to a sequence of juxtaposed keyboard keys, such as "qwerty" or "azerty" for example.

The basechars characters list consist of every characters that will be used as a starting point for the keyboard-walking sequences. The tiny.base list includes very limited, QWERTY keyboard based, starting points: 1q!Q. The full.base file provides a more comprehensive basechars list and its use is recommended.

The keymap correspond to a keyboard layout, representing the physical disposition of the keyboard keys. A keymap file should consist of 12 lines: 4 complete physical keyboard lines, represented as of (azertyuiop^$), and if pressed in combination with the modifier keys Shift (AZERTYUIOP¨£) and AltGr (€¤). Various keymaps (en-us, en-gb, fr, es, de, ru, etc.) are provided on the kwprocessor GitHub.

The route corresponds to the patterns used to generate the keyboard-walking sequences. A route is composed of a sequence of number(s), each number representing the number of pressed keys in the same geographical directions (north, south, west and east by default, extendable to north-west, north-east, south-west, south-east and repeat in place). For example, the route 1, for the h key starting point and with the default kwprocessor configuration, would generate the following words: hn, hg, hj and hy. For more information and explanation on route, refer to the kwprocessor GitHub documentation: https://github.com/hashcat/kwprocessor

# -s: include characters reachable by holding Shift. Default to false.
# -a: include characters reachable by holding AltGr. Default to false.
# -n: minimum allowed distance between keys. Default to 1.
# -x: maximum allowed distance between keys. Default to 1.
# --keywalk-all: enable all --keywalk-* directions (keywalk-north, keywalk-south, keywalk-west, keywalk-east, keywalk-north-west, keywalk-north-east, keywalk-south-west, keywalk-south-east and keywalk-repeat).
# Default keywalk routes are the cardinal geographic directions: north, south, west and east, with out repetition.

kwp -s 1 -a 1 ./basechars/full.base <KEYBOARD_LAYOUT_FILE> <ROUTES> > <OUTPUT_FILE>

Python EXREX

The Python EXREX module can be used to generate wordlists from the specified regular expression.

# pip install exrex

import exrex

# Example regex to generate variation around the password keyword:
# ((p|P)(a|A|@)(s|S|\$){2}(w|W)(o|O|0)(r|R)(d|D)\d{0,3}!{0,3})

print '\n'.join(exrex.generate('<REGEX>'))

Hash types

The hashid Python utility can be used to determine the hash type and its corresponding hashcat and john modules:

hashid -m -j "<HASH | HASH_FILE>"

Additionally, the hashcat documentation may be directly used as well in order to identify the hash type and its corresponding hashcat mode:

https://hashcat.net/wiki/doku.php?id=example_hashes

Passwords cracking tools

It is recommended to use the cracking tools on the native operating system, as opposed to a virtual system, as the performance can greatly improve.

John should be used for quick passwords cracking attempts while hashcat allows for better performance and more complex attacks for serious needs.

John-the-Ripper & magnumripper John-the-Ripper

John, also abbreviated JrT, is a password cracking tool, available notably on Linux and Windows and supporting a wide range of hashes type.

The Jumbo version of John the Ripper is a community-enhanced version of John that can be found on the magnumripper GitHub repository. It notably supports more hash types.

John will try to automatically detect the hash type of the provided hashes. John stores the cracked passwords in a "pot" file, located in ~/.john/john.pot.

John-the-Ripper usage:

john [OPTIONS] [HASH_FILE]

# Supported hash types
john --list=formats

# Show cracked passwords
john --show <HASH_FILE>
cat ~/.john/john.pot

# With out the --format option, John will automatically attempt to determine the hash type.
john --wordlist=<WORDLIST> <HASH_FILE>
john --wordlist=<WORDLIST> --format=<HASH_FORMAT> <HASH_FILE>

# Default rules.
john --wordlist=<WORDLIST> --rules --format=<HASH_FORMAT> <HASH_FILE>

# Specified rule.
john --wordlist=<WORDLIST> --rules=<Jumbo | KoreLogic | All | RULE_NAME> --format=<HASH_FORMAT> <HASH_FILE>

hashcat

hashcat is an advanced cracking tool that generally offer better performance than John and is considered to be among the world's fastest password cracking tool.

Multi-OS (Windows, Linux, etc.) and multi-platforms (CPU, GPU, etc.), hashcat supports more than 200 different hash types.

Moreover, hashcat introduced rule-based attack, which is one of the most complicated of all the passwords cracking attack modes. The rule-based attack is like a programming language designed for password candidate generation. It has functions to modify, cut or extend words and has conditional operators.

The OneRuleToRuleThemAll or its newer version OneRuleToRuleThemStill rule aggregate multiples rule sets with the aim of maximizing efficiency (success rates versus number of total candidates).

The following attack modes can be used, specified by the -a / --attack-mode option:

  • 0: dictionary attack

  • 1: combinator attack, concatenating words from multiple wordlists

  • 3: mask attack, trying all combinations from a given keyspace, defined using a mask

  • 6/7: hybrid attack, combining wordlists+masks (mode 6) and masks+wordlists (mode 7)

hashcat usage:

# Supported hash types, with a hash example
# -m 500 for md5crypt
# https://hashcat.net/wiki/doku.php?id=example_hashes
hashcat --example-hashes

# -w: Sets workload profile, with may have significant performance and power consumption impacts. 1 = Low, 2 = Default, 3 = High, and 4 = Nightmare.
# --hwmon-temp-abort <TEMP_DEGRE_CELSIUS>: Defines a maximum temperature in place of the default 90° celsius.
hashcat [options] <HASH | HASH_FILE> [<WORDLIST | MASK>]

# Dictionary attack
hashcat -w 3 -m <HASH_TYPE> -a 0 -o <OUTPUT_FILE> <HASH | HASH_FILE> <WORDLIST>
hashcat -w 3 -m <HASH_TYPE> -a 0 -r <best64.rule | OneRuleToRuleThemAll.rule | RULE_FILE> -o <OUTPUT_FILE> <HASH | HASH_FILE> <WORDLIST>

# Mask attack
# A mask is a string that configures the keyspace of the password candidate
# Built-in mask charsets
    ?l = abcdefghijklmnopqrstuvwxyz
    ?u = ABCDEFGHIJKLMNOPQRSTUVWXYZ
    ?d = 0123456789
    ?h = 0123456789abcdef
    ?H = 0123456789ABCDEF
    ?s = «space»!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~
    ?a = ?l?u?d?s
    ?b = 0x00 - 0xff

hashcat -w 3 -m <HASH_TYPE> -a 3 --increment -o <OUTPUT_FILE> <HASH | HASH_FILE> "?a?a?a?a?a?a?a?a"
hashcat -w 3 -m <HASH_TYPE> -a 3 --increment --increment-min=4 -o <OUTPUT_FILE> <HASH | HASH_FILE> "?a?a?a?a?a?a?a?a"

Misc

Firefox / Thunderbird stored passwords

Firefox and Thunderbird save the password registered by the user in the user profile:

~/.mozilla/firefox/$profile$.default/
~/.thunderbird/$profile$.default/

The passwords are stored in the following files:

Key3.db
signons.sqlite3 / logins.json

A master password can be set in either program and this affects key3.db. By default no password is set.

John-the-Ripper can be used to crack the master password:

# First extract the master password hash
python mozilla2john.py key3.db > john_key3.hash

# Crack it with john
john --show john_key3.hash

The passwords can then be extracted from the Firefox / Thunderbird profile:

python firefox_decrypt/firefox_decrypt.py <PATH_TO_PROFILE>

ZIP and RAR protected archives

The Linux utilities zip2john and rar2john, packaged with the John the Ripper Jumbo community version, can be used to extract the hash of the password protecting the archive.

zip2john <ZIP_FILE> > <ZIP_HASH_FILE>
rar2john <RAR_FILE> > <RAR_HASH_FILE>

Jumbo john can then be used to crack the extracted hash.

# Detected hash type should be "PKZIP [32/64]"
john --wordlist=<WORDLIST> <ZIP_HASH_FILE>
john --wordlist=<WORDLIST> <RAR_HASH_FILE>

The Linux utility fcrackzip may be used as well and works directly on the ZIP archive.

# -u (–use-unzip): use unzip to weed out wrong passwords
# -D and -p: use dictionary with the specified wordlist
fcrackzip -u -D -p <WORDLIST> <ZIP_FILE>

Password protected PDF

The Linux utility pdfcrack can be used to crack password protecting PDF files.

pdfcrack -w <WORDLIST> -f <PDF_FILE>

Encrypted SSH private keys

The Linux utilities ssh2john, packaged with the John the Ripper Jumbo community version, can be used to convert an encrypted SSH private key to a crackable hash by john.

ssh2john <SSH_PRIVKEY_ENC_FILE> > <SSH_HASH_FILE>

Jumbo john can then be used to crack the extracted hash.

john --wordlist=<WORDLIST> <SSH_HASH_FILE>

Linux Unified Key Setup (LUKS)

hashcat and bruteforce-luks can be used to crack LUKS encrypted disks:

dd if=<DISK | FILE> of=tmp_luks_header bs=512 count=4097
# dd if=<DISK | FILE> of=tmp_luks_header bs=1M count=10
hashcat --force -m 14600 -a 0 -w 3 tmp_luks_header <WORDLIST>
bruteforce-luks -t 4 -f <WORDLIST> tmp_luks_header

Once the password is retrieved, the Linux utility cryptsetup can be used to create a device that can be mounted:

cryptsetup  open --type luks <LUKS_FILE> <DEVICE_NAME>
mount /dev/mapper/<DEVICE_NAME> /mnt

PKCS#12 certificate

The Linux utilities pfx2john, packaged with the John the Ripper Jumbo community version, can be used to convert a password protected PKCS12 certificate to a hash crackable by john.

pfx2john <PKCS12_CERTIFICATE> > <PKCS12_HASH_FILE>

john --wordlist=<WORDLIST> <PKCS12_HASH_FILE>

mRemoteNG

mRemoteNG is an open source multi-protocol remote connections manager. The connections information, including usernames and passwords, are stored encrypted in confCons.xml files.

On older versions of mRemoteNG, the passwords were encrypted in AES-128-CBC using the md5 of mR3m as the secret key and storing the IV in the 16 first bytes of the passwords hash.

The clear-text passwords can be retrieved on all mRemoteNG versions directly through the GUI application by creating an external tool:

Tools -> External Tools -> New External Tool
  Display Name: Print password
  Filename: cmd
  Arguments: /k echo %password%

After the confCons.xml is loaded, the created external tool can be used to retrieve the passwords
Connections -> <CONNECTION> -> External Tools -> Print pasword

References

https://github.com/hashcat/kwprocessor http://cosine-security.blogspot.com/2011/06/stealing-password-from-mremote.html https://robszar.wordpress.com/2012/08/07/view-mremote-passwords-4/

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