Solver for Flareon5 challenge 6, "dirty" version

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace ConsoleApplication1
{
    class Program
    {
        //rc4
        public static byte[] RC4(byte[] data, byte[] pwd)
        {
            int a, i, j, k, tmp;
            int[] key, box;
            byte[] cipher;

            key = new int[256];
            box = new int[256];
            cipher = new byte[data.Length];

            for (i = 0; i < 256; i++)
            {
                key[i] = pwd[i % pwd.Length];
                box[i] = i;
            }
            for (j = i = 0; i < 256; i++)
            {
                j = (j + box[i] + key[i]) % 256;
                tmp = box[i];
                box[i] = box[j];
                box[j] = tmp;
            }
            for (a = j = i = 0; i < data.Length; i++)
            {
                a++;
                a %= 256;
                j += box[a];
                j %= 256;
                tmp = box[a];
                box[a] = box[j];
                box[j] = tmp;
                k = box[((box[a] + box[j]) % 256)];
                cipher[i] = (byte)(data[i] ^ k);
            }
            return cipher;
        }

        // Table for CRC calculation
        static readonly uint[] crcTable = new uint[256] {  
            0x00000000u, 0x77073096u, 0xee0e612cu, 0x990951bau, 0x076dc419u,
            0x706af48fu, 0xe963a535u, 0x9e6495a3u, 0x0edb8832u, 0x79dcb8a4u,
            0xe0d5e91eu, 0x97d2d988u, 0x09b64c2bu, 0x7eb17cbdu, 0xe7b82d07u,
            0x90bf1d91u, 0x1db71064u, 0x6ab020f2u, 0xf3b97148u, 0x84be41deu,
            0x1adad47du, 0x6ddde4ebu, 0xf4d4b551u, 0x83d385c7u, 0x136c9856u,
            0x646ba8c0u, 0xfd62f97au, 0x8a65c9ecu, 0x14015c4fu, 0x63066cd9u,
            0xfa0f3d63u, 0x8d080df5u, 0x3b6e20c8u, 0x4c69105eu, 0xd56041e4u,
            0xa2677172u, 0x3c03e4d1u, 0x4b04d447u, 0xd20d85fdu, 0xa50ab56bu,
            0x35b5a8fau, 0x42b2986cu, 0xdbbbc9d6u, 0xacbcf940u, 0x32d86ce3u,
            0x45df5c75u, 0xdcd60dcfu, 0xabd13d59u, 0x26d930acu, 0x51de003au,
            0xc8d75180u, 0xbfd06116u, 0x21b4f4b5u, 0x56b3c423u, 0xcfba9599u,
            0xb8bda50fu, 0x2802b89eu, 0x5f058808u, 0xc60cd9b2u, 0xb10be924u,
            0x2f6f7c87u, 0x58684c11u, 0xc1611dabu, 0xb6662d3du, 0x76dc4190u,
            0x01db7106u, 0x98d220bcu, 0xefd5102au, 0x71b18589u, 0x06b6b51fu,
            0x9fbfe4a5u, 0xe8b8d433u, 0x7807c9a2u, 0x0f00f934u, 0x9609a88eu,
            0xe10e9818u, 0x7f6a0dbbu, 0x086d3d2du, 0x91646c97u, 0xe6635c01u,
            0x6b6b51f4u, 0x1c6c6162u, 0x856530d8u, 0xf262004eu, 0x6c0695edu,
            0x1b01a57bu, 0x8208f4c1u, 0xf50fc457u, 0x65b0d9c6u, 0x12b7e950u,
            0x8bbeb8eau, 0xfcb9887cu, 0x62dd1ddfu, 0x15da2d49u, 0x8cd37cf3u,
            0xfbd44c65u, 0x4db26158u, 0x3ab551ceu, 0xa3bc0074u, 0xd4bb30e2u,
            0x4adfa541u, 0x3dd895d7u, 0xa4d1c46du, 0xd3d6f4fbu, 0x4369e96au,
            0x346ed9fcu, 0xad678846u, 0xda60b8d0u, 0x44042d73u, 0x33031de5u,
            0xaa0a4c5fu, 0xdd0d7cc9u, 0x5005713cu, 0x270241aau, 0xbe0b1010u,
            0xc90c2086u, 0x5768b525u, 0x206f85b3u, 0xb966d409u, 0xce61e49fu,
            0x5edef90eu, 0x29d9c998u, 0xb0d09822u, 0xc7d7a8b4u, 0x59b33d17u,
            0x2eb40d81u, 0xb7bd5c3bu, 0xc0ba6cadu, 0xedb88320u, 0x9abfb3b6u,
            0x03b6e20cu, 0x74b1d29au, 0xead54739u, 0x9dd277afu, 0x04db2615u,
            0x73dc1683u, 0xe3630b12u, 0x94643b84u, 0x0d6d6a3eu, 0x7a6a5aa8u,
            0xe40ecf0bu, 0x9309ff9du, 0x0a00ae27u, 0x7d079eb1u, 0xf00f9344u,
            0x8708a3d2u, 0x1e01f268u, 0x6906c2feu, 0xf762575du, 0x806567cbu,
            0x196c3671u, 0x6e6b06e7u, 0xfed41b76u, 0x89d32be0u, 0x10da7a5au,
            0x67dd4accu, 0xf9b9df6fu, 0x8ebeeff9u, 0x17b7be43u, 0x60b08ed5u,
            0xd6d6a3e8u, 0xa1d1937eu, 0x38d8c2c4u, 0x4fdff252u, 0xd1bb67f1u,
            0xa6bc5767u, 0x3fb506ddu, 0x48b2364bu, 0xd80d2bdau, 0xaf0a1b4cu,
            0x36034af6u, 0x41047a60u, 0xdf60efc3u, 0xa867df55u, 0x316e8eefu,
            0x4669be79u, 0xcb61b38cu, 0xbc66831au, 0x256fd2a0u, 0x5268e236u,
            0xcc0c7795u, 0xbb0b4703u, 0x220216b9u, 0x5505262fu, 0xc5ba3bbeu,
            0xb2bd0b28u, 0x2bb45a92u, 0x5cb36a04u, 0xc2d7ffa7u, 0xb5d0cf31u,
            0x2cd99e8bu, 0x5bdeae1du, 0x9b64c2b0u, 0xec63f226u, 0x756aa39cu,
            0x026d930au, 0x9c0906a9u, 0xeb0e363fu, 0x72076785u, 0x05005713u,
            0x95bf4a82u, 0xe2b87a14u, 0x7bb12baeu, 0x0cb61b38u, 0x92d28e9bu,
            0xe5d5be0du, 0x7cdcefb7u, 0x0bdbdf21u, 0x86d3d2d4u, 0xf1d4e242u,
            0x68ddb3f8u, 0x1fda836eu, 0x81be16cdu, 0xf6b9265bu, 0x6fb077e1u,
            0x18b74777u, 0x88085ae6u, 0xff0f6a70u, 0x66063bcau, 0x11010b5cu,
            0x8f659effu, 0xf862ae69u, 0x616bffd3u, 0x166ccf45u, 0xa00ae278u,
            0xd70dd2eeu, 0x4e048354u, 0x3903b3c2u, 0xa7672661u, 0xd06016f7u,
            0x4969474du, 0x3e6e77dbu, 0xaed16a4au, 0xd9d65adcu, 0x40df0b66u,
            0x37d83bf0u, 0xa9bcae53u, 0xdebb9ec5u, 0x47b2cf7fu, 0x30b5ffe9u,
            0xbdbdf21cu, 0xcabac28au, 0x53b39330u, 0x24b4a3a6u, 0xbad03605u,
            0xcdd70693u, 0x54de5729u, 0x23d967bfu, 0xb3667a2eu, 0xc4614ab8u,
            0x5d681b02u, 0x2a6f2b94u, 0xb40bbe37u, 0xc30c8ea1u, 0x5a05df1bu,
            0x2d02ef8du
        };

        // Calculate CRC based on the old CRC and the new bytes 
        // See RFC1952 for details.
        static public uint UpdateCrc32(byte[] buffer, int length)
        {
            uint crc32 = 0xffffffffU;
            for (int i = 0;i<length;i++)
            {
                crc32 = crcTable[(crc32 ^ buffer[i]) & 0xFF] ^ (crc32 >> 8);
            }
            crc32 ^= 0xffffffffU;
            return crc32;
        }
        static byte[] SolveCrc(UInt32 target, uint count1)
        {
            byte[] result = null;
            for (UInt64 xx = 0; xx < 0x100000000; xx++)
            {
                result = BitConverter.GetBytes((UInt32)xx);
                uint calcCrc = UpdateCrc32(result, (int)count1);
                if (calcCrc == target)
                    break;
            }
            return result;
        }

        static byte SolveFibo(UInt64 target)
        {
            UInt64 result1 = 1;
            UInt64 result2 = 1;
            int i = 0;
            while (result1 != target)
            {
                i++;
                UInt64 q = result2;
                result2 = result1+result2;
                result1 = q;
            }
            return (byte)i;
        }

        static void TestB64()
        {

            byte[] lookupTable = new byte[] {
0x2A,0x39,0x5F,0x64,0xC2,0xA7,0x46,0x23,0x53,0x6B,0x74,0x47,0x28,0x4D,0x70,0x42,0x49,0x25,0x52,0x6A,0x62,0x38,0x40,0x4A,0x69,0x45,0x44,0x59,0x2D,0x31,0x24,0x50,0x67,0x79,0x54,0x21,0x4C,0x76,0x71,0x66,0x2B,0x63,0x68,0x6D,0x51,0x57,0x4F,0x30,0x65,0x4E,0x5A,0x34,0x75,0x6E,0x33,0x6C,0x37,0x48,0x26,0x32,0x77,0x61,0x7A,0x4B,0x56
                        };
            UInt64 buf = 0;
            int count1 = 3;
            byte[] expect = new byte[] { 0x53, 0x23, 0x76, 0x30 };
            byte[] output = new byte[] { 0, 0, 0, 0 };
            for (int j = 0; j <= count1; j++)
            {
                buf <<= 6;
                byte b3 = (byte)expect[j];
                uint i3 = (uint)Array.IndexOf(lookupTable, b3);        //53->8;
                buf |= i3;
            }
            if (count1 == 3)
            {
                output[2] = (byte)(buf & 0xFF);
                buf >>= 8;
                output[1] = (byte)(buf & 0xFF);
                buf >>= 8;
                output[0] = (byte)(buf & 0xFF);
            }
            else if (count1 == 2)
            {
                buf >>= 2;
                output[1] = (byte)(buf & 0xFF);
                buf >>= 8;
                output[0] = (byte)(buf & 0xFF);
            }
            else if (count1 == 1)
            {
                buf >>= 4;
                output[0] = (byte)(buf & 0xFF);
            }
            else
                throw new Exception("crap");
      
        }

        static void Main(string[] args)
        {
            TestB64();

            //Console.WriteLine("{0:X}", SolveFibo(0x12062F76909038C5));
            
            //byte[] data = File.ReadAllBytes(@"F:\flare2018\06-magic\core.11288");
            byte[] data = File.ReadAllBytes(args[0]);
            //int dataOffset = 0x5100;
            //uint rva2offText = 0;
            //uint rva2offData = 0;
            //int dataOffset = 0x6C10;    //in core.11288
            //int dataOffset = 0x1F44;    //in core.11288
            uint rva2offText = 0xB10;
            uint rva2offData = 0x5B10-0x4000;
            int dataOffset = 0;
            /*
            // decode methods. DONT NEED!
            for (int i = 0; i < 0x21; i++)
            {
                UInt32 offset = BitConverter.ToUInt32(data, dataOffset + i * 0x120 + 0);
                offset -= 0x400000;
                offset += rva2offText;
                UInt32 size = BitConverter.ToUInt32(data, dataOffset + i * 0x120 + 8);
                UInt32 keyOffset = BitConverter.ToUInt32(data, dataOffset + i * 0x120 + 0x18);
                keyOffset -= 0x600000;
                keyOffset += rva2offData;
                Console.WriteLine("decrypting adr={0:X} size={1:X} key={2:X}", offset, size, keyOffset);

                for (int j = 0; j < size; j++)
                {
                    data[offset+j] ^= data[keyOffset + j];
                }
            }
            File.WriteAllBytes(@"F:\flare2018\06-magic\core.11288-dec", data);
            */

            Dictionary<UInt32, string> methods = new Dictionary<UInt32, string>();
            methods.Add(0x84, "xor2A");
            methods.Add(0x7C, "memcpy");
            methods.Add(0x147, "fibo");
            methods.Add(0x326, "base64");
            methods.Add(0x8F, "plusD");
            methods.Add(0x2FE, "rc4-2FE");
            methods.Add(0xB3, "crc");

            // now process all entries, print type and etc..
            char[] key = new char[0x45];
            for (int i = 0; i < 0x45; i++)
            {
                key[i] = '?';
            }

            for (int i = 0; i < 0x21; i++)
            {
                UInt32 size = BitConverter.ToUInt32(data, dataOffset + i * 0x120 + 8);
                UInt32 idx1 = BitConverter.ToUInt32(data, dataOffset + i * 0x120 + 0xC);
                UInt32 count1 = BitConverter.ToUInt32(data, dataOffset + i * 0x120 + 0x10);
                //Console.WriteLine("method{0:X2} = {1}({2:X},{3:X})", i, methods[size], idx1, count1);
                switch (size)
                {
                    case 0x7C:
                        //copy
                        for (int j = 0; j < count1; j++)
                        {
                            byte b = (byte)(data[dataOffset + i * 0x120 + 0x20 + j]);
                            key[idx1 + j] = (char)b;
                        }
                        break;
                    case 0x84:
                        // xor2a
                        for (int j = 0; j < count1; j++)
                        {
                            byte b = (byte)(data[dataOffset + i * 0x120 + 0x20 + j] ^ 0x2A);
                            key[idx1 + j] = (char)b;
                        }
                        break;
                    case 0x8F:
                        for (int j = 0; j < count1; j++)
                        {
                            byte b = (byte)(data[dataOffset + i * 0x120 + 0x20 + j] - 0xD);
                            key[idx1 + j] = (char)b;
                        }
                        break;
                    case 0xB3:
                        //crc
                        UInt32 target = BitConverter.ToUInt32(data, dataOffset + i * 0x120 + 0x20);
                        byte[] bb = SolveCrc(target, count1);
                        for (int j = 0; j < count1; j++)
                        {
                            key[idx1 + j] = (char)bb[j];
                        }
                        break;
                    case 0x147:
                        //fibo
                        for (int j = 0; j < count1; j++)
                        {
                            UInt64 target2 = BitConverter.ToUInt64(data, dataOffset + i * 0x120 + 0x20 + j * 8);
                            byte b = SolveFibo(target2);
                            key[idx1 + j] = (char)b;
                        }
                        break;
                    case 0x2FE:
                        //rc4
                        byte[] zeroes= new byte[0x256];
                        byte[] rc4key = Encoding.ASCII.GetBytes("Tis but a scratch.");
                        byte[] enczeroes = RC4(zeroes, rc4key);
                        for (int j = 0; j < count1; j++)
                        {
                            byte b = (byte)(data[dataOffset + i * 0x120 + 0x20 + j] ^ enczeroes[j]);
                            key[idx1 + j] = (char)b;
                        }
                        break;
                    case 0x326:
                        //custom base64
                        byte[] lookupTable = new byte[] {
0x2A,0x39,0x5F,0x64,0xC2,0xA7,0x46,0x23,0x53,0x6B,0x74,0x47,0x28,0x4D,0x70,0x42,0x49,0x25,0x52,0x6A,0x62,0x38,0x40,0x4A,0x69,0x45,0x44,0x59,0x2D,0x31,0x24,0x50,0x67,0x79,0x54,0x21,0x4C,0x76,0x71,0x66,0x2B,0x63,0x68,0x6D,0x51,0x57,0x4F,0x30,0x65,0x4E,0x5A,0x34,0x75,0x6E,0x33,0x6C,0x37,0x48,0x26,0x32,0x77,0x61,0x7A,0x4B,0x56
                        };
                        UInt64 buf = 0;

                        for (int j = 0; j <= count1; j++)
                        {
                            buf <<= 6;
                            byte b3 = (byte)(data[dataOffset + i * 0x120 + 0x20 + j]);
                            uint i3 = (uint)Array.IndexOf(lookupTable, b3);        //53->8;
                            buf |= i3;
                        }
                        if (count1 == 3)
                        {
                            key[idx1 + 2] = (char)(buf & 0xFF);
                            buf >>= 8;
                            key[idx1 + 1] = (char)(buf & 0xFF);
                            buf >>= 8;
                            key[idx1 + 0] = (char)(buf & 0xFF);
                        }
                        else if (count1 == 2)
                        {
                            buf >>= 2;
                            key[idx1 + 1] = (char)(buf & 0xFF);
                            buf >>= 8;
                            key[idx1 + 0] = (char)(buf & 0xFF);
                        }
                        else if (count1 == 1)
                        {
                            buf >>= 4;
                            key[idx1 + 0] = (char)(buf & 0xFF);
                        }
                        else
                            throw new Exception("crap");

                        break;

                }
            }
            Console.Write(new string(key) + '\xA' + '\x0') ;
        }
    }
}