There isn't really an off-the-shelf way to do this, at least without a pretty complicated mask rule in hashcat, but it's trivial to write up some code to do it.
Here's some C# that very quickly builds a wordlist using the scheme you described:
interface IMutator
{
IEnumerable<string> Mutate(string input);
}
static class MutatorExtensions
{
public static IEnumerable<string> ChainMutator(this IEnumerable<string> input, IMutator m)
{
foreach (string si in input)
{
var output = m.Mutate(si);
foreach (string so in output)
{
yield return so;
}
}
}
}
class CapsMutator : IMutator
{
public IEnumerable<string> Mutate(string input)
{
if (input.Length > 64)
throw new ArgumentOutOfRangeException(nameof(input), "Input must be 64 characters long or less.");
UInt64 maskLimit = 1UL << input.Length;
char[] lowercase = input.ToLowerInvariant().ToCharArray();
char[] uppercase = input.ToUpperInvariant().ToCharArray();
char[] output = new char[input.Length];
for (UInt64 mask = 0; mask < maskLimit; mask++)
{
for (int n = 0; n < input.Length; n++)
{
output[n] = ((mask & (1UL << n)) == 0) ? lowercase[n] : uppercase[n];
}
yield return new string(output);
}
}
}
class PrependAppendMutator : IMutator
{
public string CharacterSet { get; }
private char[] _characters;
public PrependAppendMutator(string characterSet)
{
CharacterSet = characterSet;
_characters = characterSet.ToCharArray();
}
public IEnumerable<string> Mutate(string input)
{
for (int i = 0; i < _characters.Length; i++)
{
yield return input + _characters[i];
yield return _characters[i] + input;
}
}
}
class RepeatMutator : IMutator
{
public IMutator Mutator { get; }
public int MinimumCount { get; }
public int MaximumCount { get; }
public RepeatMutator(IMutator mutator, int minCount, int maxCount)
{
Mutator = mutator;
MinimumCount = minCount;
MaximumCount = maxCount;
}
public IEnumerable<string> Mutate(string input)
{
for (int c = MinimumCount; c <= MaximumCount; c++)
{
var strings = new List<string>();
strings.Add(input);
for (int i = 0; i < c; i++)
{
var nextStrings = new List<string>();
foreach (string s in strings)
{
nextStrings.AddRange(Mutator.Mutate(s));
}
strings = nextStrings;
}
foreach (string s in strings)
{
yield return s;
}
}
}
}
void Main()
{
MainAsync().GetAwaiter().GetResult();
}
async Task MainAsync()
{
// mutates a string into any combination of lower/upper
var capsMutator = new CapsMutator();
// adds any character from the given set to the start or end of the string
var numericMutator = new PrependAppendMutator("123456");
// repeats the numeric mutator 1-5 times (5 chosen because yjb + alpha = 4 chars, and password length limit is 9)
var numericRepeatMutator = new RepeatMutator(numericMutator, 1, 5);
// adds any character from the given set to the start or end of the string
var alphaMutator = new PrependAppendMutator("qwertyasdfghzxcvb");
// two mutator chains: one for the letter on the outside (yjB123x), one for the letter on the inside (yjBx123)
var letterOnOutsideList = capsMutator.Mutate("yjb").ChainMutator(numericRepeatMutator).ChainMutator(alphaMutator);
var letterOnInsideList = capsMutator.Mutate("yjb").ChainMutator(alphaMutator).ChainMutator(numericRepeatMutator);
// write all the words
using (var sw = new StreamWriter(@"X:\path\to\wordlist.txt"))
{
foreach (string word in letterOnOutsideList)
{
await sw.WriteLineAsync(word);
}
foreach (string word in letterOnInsideList)
{
await sw.WriteLineAsync(word);
}
// ensure everything was written
sw.Flush();
}
Console.WriteLine("Done!");
}
You can run this in LinqPad.
This takes around 25 seconds to execute on my system, and produces a 1.5GB wordlist containing around 147 million lines. The shortest password is 5 characters, not 4, because you can trivially bruteforce the 4-character space anyway and it simplifies the code.
If you're cracking the password on a GPU, I'd recommend removing the caps mutator from the wordlist generation, i.e. change the mutator chain definitions to:
var letterOnOutsideList = numericRepeatMutator.Mutate("yjb").ChainMutator(alphaMutator);
var letterOnInsideList = numericRepeatMutator.Mutate("yjb").ChainMutator(alphaMutator);
You can then use the built-in rule functionality in hashcat to do the caps mutation for you. This reduces the wordlist build time to just 2-3 seconds, producing a much more manageable 196MB wordlist with 18 million lines. This also results in a faster cracking rate because it's faster to get the GPU to produce the caps mutations than it is to transfer them from system memory to GPU memory.
If you want to modify the rules, the code should be pretty explanatory.
As an addendum, I highly recommend practicing building little programs like this. This took me about 10 minutes to write, including testing, which is far less time than it would've taken me to read through the hashcat docs and come up with a mask attack string and mutator ruleset that did what I wanted. It's not uncommon to run into situations where using the standard/ideal tool for the job isn't actually the best use of your time, especially if it's one you only occasionally use. Don't be afraid to take the quick and hacky solution for one-off cases like this.
