How to generate password_hash for RabbitMQ Management HTTP API

The beloved RabbitMQ Management Plugin has a HTTP API to manage the RabbitMQ through plain HTTP requests.

We need to create users programatically, and the HTTP API was the chosen way to go. The documentation is scarce, but the API it's pretty simple and intuitive.

Concerned about the security, we don't want to pass the user password in plain text, and the API offers a field to send the password hash instead. Quote from there:

[ GET | PUT | DELETE ] /api/users/name

An individual user. To PUT a user, you will need a body looking something like this:

{"password":"secret","tags":"administrator"}

or:

{"password_hash":"2lmoth8l4H0DViLaK9Fxi6l9ds8=", "tags":"administrator"}

The tags key is mandatory. Either password or password_hash must be set.

So far, so good, the problem is: how to correctly generate the password_hash?

The password hashing algorithm is configured in RabbitMQ's configuration file, and our is configured as the default SHA256.

I'm using C#, and the following code to generate the hash:

var cr = new SHA256Managed();
var simplestPassword = "1";
var bytes = cr.ComputeHash(Encoding.UTF8.GetBytes(simplestPassword));
var sb = new StringBuilder();
foreach (var b in bytes) sb.Append(b.ToString("x2"));
var hash = sb.ToString();

This doesn't work. Testing in some online tools for SHA256 encryption, the code is generating the expected output. However, if we go to the management page and set the user password manually to "1" then it works like a charm.

This answer led me to export the configurations and take a look at the hashes RabbitMQ are generating, and I realized a few things:

• hash example of "1": "y4xPTRVfzXg68sz9ALqeQzARam3CwnGo53xS752cDV5+Utzh"
• all the user's hashes have fixed length
• the hashes change every time (even if the password is the same). I know PB2K also do this to passwords, but don't know the name of this cryptographic property.
• if I pass the password_hash the RabbitMQ stores it without changes

I'm accepting suggestions in another programming languages as well, not just C#.

Solution 1:

And for the fun the bash version !

#!/bin/bash

function encode_password()
{
    SALT=$(od -A n -t x -N 4 /dev/urandom)
    PASS=$SALT$(echo -n $1 | xxd -ps | tr -d '\n' | tr -d ' ')
    PASS=$(echo -n $PASS | xxd -r -p | sha256sum | head -c 128)
    PASS=$(echo -n $SALT$PASS | xxd -r -p | base64 | tr -d '\n')
    echo $PASS
}

encode_password "some-password"

Solution 2:

From: http://rabbitmq.1065348.n5.nabble.com/Password-Hashing-td276.html

However, the algorithm is quite simple if you want to implement it yourself. Here's a worked example:

Generate a random 32 bit salt:

CA D5 08 9B

Concatenate that with the UTF-8 representation of the password (in this case "simon"):

CA D5 08 9B 73 69 6D 6F 6E

Take the MD5 hash:

CB 37 02 72 AC 5D 08 E9 B6 99 4A 17 2B 5F 57 12

Concatenate the salt again:

CA D5 08 9B CB 37 02 72 AC 5D 08 E9 B6 99 4A 17 2B 5F 57 12

And convert to base64 encoding:

ytUIm8s3AnKsXQjptplKFytfVxI=

you should be able to modify your code to follow this process

Solution 3:

For lazy people (like me ;) ), there is the code for computing RabbitMq password with Sha512 for the framework .Net Core.

public static class RabbitMqPasswordHelper
{
    public static string EncodePassword(string password)
    {
        using (RandomNumberGenerator rand = RandomNumberGenerator.Create())
        using (var sha512 = SHA512.Create())
        {
            byte[] salt = new byte[4];

            rand.GetBytes(salt);

            byte[] saltedPassword = MergeByteArray(salt, Encoding.UTF8.GetBytes(password));
            byte[] saltedPasswordHash = sha512.ComputeHash(saltedPassword);

            return Convert.ToBase64String(MergeByteArray(salt, saltedPasswordHash));
        }
    }

    private static byte[] MergeByteArray(byte[] array1, byte[] array2)
    {
        byte[] merge = new byte[array1.Length + array2.Length];
        array1.CopyTo(merge, 0);
        array2.CopyTo(merge, array1.Length);

        return merge;
    }
}

Solution 4:

Here is a small python script I stumbled across some time ago (attribution is in the script) that is great for quick hash generation. It doesn't do any error checking, so is quite simple:

#!/usr/bin/env python3

# rabbitMQ password hashing algo as laid out in:
# http://lists.rabbitmq.com/pipermail/rabbitmq-discuss/2011-May/012765.html

from __future__ import print_function
import base64
import os
import hashlib
import struct
import sys

# This is the password we wish to encode
password = sys.argv[1]

# 1.Generate a random 32 bit salt:
# This will generate 32 bits of random data:
salt = os.urandom(4)

# 2.Concatenate that with the UTF-8 representation of the plaintext password
tmp0 = salt + password.encode('utf-8')

# 3. Take the SHA256 hash and get the bytes back
tmp1 = hashlib.sha256(tmp0).digest()

# 4. Concatenate the salt again:
salted_hash = salt + tmp1

# 5. convert to base64 encoding:
pass_hash = base64.b64encode(salted_hash)

print(pass_hash.decode("utf-8"))

Solution 5:

Just in case, full code from Waldo should be next

//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Security.Cryptography;
using System.Text;

namespace Rextester
{
    public static class RabbitMqPasswordHelper
{
    public static string EncodePassword(string password)
    {
        using (RandomNumberGenerator rand = RandomNumberGenerator.Create())
        using (var sha256 = SHA256.Create())
        {
            byte[] salt = new byte[4];

            rand.GetBytes(salt);

            byte[] saltedPassword = MergeByteArray(salt, Encoding.UTF8.GetBytes(password));
            byte[] saltedPasswordHash = sha256.ComputeHash(saltedPassword);

            return Convert.ToBase64String(MergeByteArray(salt, saltedPasswordHash));
        }
    }

    private static byte[] MergeByteArray(byte[] array1, byte[] array2)
    {
        byte[] merge = new byte[array1.Length + array2.Length];
        array1.CopyTo(merge, 0);
        array2.CopyTo(merge, array1.Length);

        return merge;
    }
}

    public class Program
    {
        public static void Main(string[] args)
        {
            //Your code goes here
            Console.WriteLine(Rextester.RabbitMqPasswordHelper.EncodePassword("MyPassword"));
        }
    }
}

You can run it online on http://rextester.com/. Output of program will contain your hash.

Python version by christianclinton (https://gist.github.com/christianclinton/faa1aef119a0919aeb2e)

#!/bin/env/python
import hashlib
import binascii

# Utility methods for generating and comparing RabbitMQ user password hashes.
#
# Rabbit Password Hash Algorithm:
# 
# Generate a random 32 bit salt: 
# CA D5 08 9B 

# Concatenate that with the UTF-8 representation of the password (in this 
# case "simon"): 
# CA D5 08 9B 73 69 6D 6F 6E 

# Take the MD5 hash: 
# CB 37 02 72 AC 5D 08 E9 B6 99 4A 17 2B 5F 57 12 

# Concatenate the salt again: 
# CA D5 08 9B CB 37 02 72 AC 5D 08 E9 B6 99 4A 17 2B 5F 57 12 

# And convert to base64 encoding: 
# ytUIm8s3AnKsXQjptplKFytfVxI= 
# 
# Sources:
# http://rabbitmq.1065348.n5.nabble.com/Password-Hashing-td276.html
# http://hg.rabbitmq.com/rabbitmq-server/file/df7aa5d114ae/src/rabbit_auth_backend_internal.erl#l204 

# Test Case:
#   print encode_rabbit_password_hash('CAD5089B', "simon")
#   print decode_rabbit_password_hash('ytUIm8s3AnKsXQjptplKFytfVxI=')
#   print check_rabbit_password('simon','ytUIm8s3AnKsXQjptplKFytfVxI=')

def encode_rabbit_password_hash(salt, password):
    salt_and_password = salt + password.encode('utf-8').encode('hex')
    salt_and_password = bytearray.fromhex(salt_and_password)
    salted_md5 = hashlib.md5(salt_and_password).hexdigest()
    password_hash = bytearray.fromhex(salt + salted_md5)
    password_hash = binascii.b2a_base64(password_hash).strip()
    return password_hash

def decode_rabbit_password_hash(password_hash):
    password_hash = binascii.a2b_base64(password_hash)
    decoded_hash = password_hash.encode('hex')
    return (decoded_hash[0:8], decoded_hash[8:])

def check_rabbit_password(test_password, password_hash):
    salt, hash_md5sum = decode_rabbit_password_hash(password_hash)
    test_password_hash = encode_rabbit_password_hash(salt, test_password)
    return test_password_hash == password_hash

Have fun!