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21 April 2016

Cracking MongoDB Passwords

by {"name"=>"Stephen Haywood", "url"=>"https://twitter.com/averagesecguy"}

On a recent penetration test I came across a number of MongoDB servers that allowed unauthenticated access. Using this access, I was able to download the MongoDB user accounts and their associated password hashes. MongoDB uses two password hashing schemes. The first is called MONGODB-CR, which is a simple MD5 hash of the string username:mongo:password. This password hashing algorithm is no longer used and has been replaced by a much stronger password hashing algorithm based on SCRAM-SHA-1. When MongoDB introduced the SCRAM-SHA-1 algorithm they didn’t update the older user accounts to use the new hashing algorithm so you will still find servers that use the older MONGODB-CR format.

I wrote two scripts to crack these passwords. The first, mongodb_cr_crack.py, is a Python script for cracking MONGODB-CR passwords that is multithreaded and can process a large number of passwords quickly because MD5 password hashes are easily calculated. This script uses Python3 and the standard libraries. To use this script run ./mongodb_cr_crack.py hashfile wordfile, where hashfile is file containing a list of colon (:) separated usernames and password hashes (one per line) and wordfile is a list of password candidates.

The second script, mongoscram.go, is written in Go, which worked much faster than Python for calculating the SCRAM-SHA-1 passwords. Since the SCRAM algorithm uses PBKDF2 with 10,000 iterations, cracking these passwords is compute intensive and takes a lot of time. The mongoscram.go script can test over 300 passwords per second for one user. To use the script you will need to install the latest version of the Go language and you will need to install the PBKDF2 library using go get http://golang.org/x/crypto/pbkdf2. You will also need to define the environment variable GOPATH (On Linux or Mac add export GOPATH=$HOME/go to your .bash_profile file.).

When running the mongoscram.go script you will need to provide the username, password_file, salt, and stored_key. The username, salt, and stored_key can be obtained from the MongoDB server. The password_file is the list of passwords you want to test.

As always, if you have any trouble running the scripts or getting them to work please let me know and I will be happy to help.