#include<stdio.h>
#include<stdlib.h>

/* https://github.com/kokke/tiny-AES-c */

#include "aes.h"
#include "aes.c"

#define __cdecl __attribute__((__cdecl__))
/*
Ref -> RFC 3602
*/
unsigned char AES_KEY[16] = {
    0x56, 0xE4, 0x7A, 0x38, 0xC5, 0x59, 0x89, 0x74, 0xBC, 0x46, 0x90, 0x3D,
    0xBA, 0x29, 0x03, 0x49
};

unsigned char CTR_IV[16] = {
    0x8C, 0xE8, 0x2E, 0xEF, 0xBE, 0xA0, 0xDA, 0x3C, 0x44, 0x69, 0x9E, 0xD7,
    0xDB, 0x51, 0xB7, 0xD9
};


unsigned char SubTable[256] = {
    0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B,
    0x1C, 0x1D, 0x1E, 0x1F, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
    0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x50, 0x51, 0x52, 0x53,
    0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5A, 0x5B, 0x5C, 0x5D, 0x5E, 0x5F,
    0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7A, 0x7B,
    0x7C, 0x7D, 0x7E, 0x7F, 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
    0x98, 0x99, 0x9A, 0x9B, 0x9C, 0x9D, 0x9E, 0x9F, 0xB0, 0xB1, 0xB2, 0xB3,
    0xB4, 0xB5, 0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xBB, 0xBC, 0xBD, 0xBE, 0xBF,
    0xD0, 0xD1, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xDB,
    0xDC, 0xDD, 0xDE, 0xDF, 0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7,
    0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFF, 0xE0, 0xE1, 0xE2, 0xE3,
    0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9, 0xEA, 0xEB, 0xEC, 0xED, 0xEE, 0xEF,
    0xC0, 0xC1, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xCB,
    0xCC, 0xCD, 0xCE, 0xCF, 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7,
    0xA8, 0xA9, 0xAA, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF, 0x80, 0x81, 0x82, 0x83,
    0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E, 0x8F,
    0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6A, 0x6B,
    0x6C, 0x6D, 0x6E, 0x6F, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
    0x48, 0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F, 0x20, 0x21, 0x22, 0x23,
    0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F,
    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B,
    0x0C, 0x0D, 0x0E, 0x0F
};

unsigned char InvSubTable[256];

void __cdecl incr_iv(unsigned __int8 *a1) {
    signed int i; // [esp+Ch] [ebp-4h]

    for ( i = 15; i > 11; --i ) {
        if ( ++a1[i] )
            break;
    }
}

void cc_aes_ctr(struct AES_ctx *ctx,uint8_t* buf, uint32_t length) {
    uintptr_t i;

    unsigned char s[16];
    memcpy(s,ctx->Iv,12);
    memset(&s[12],0,4);

    unsigned char tmp[16];
    memcpy(tmp,s,16);

    for (i = 0; i < length; i += AES_BLOCKLEN) {
        memcpy(s,tmp,16);
        incr_iv((unsigned __int8 *)s);
        memcpy(tmp,s,16);
        Cipher((state_t*)s,ctx->RoundKey);


        unsigned int max = 16;
        if ( i + 16 > length )
            max = length & 0xF;

        for(int j=0; j<max; j++)
            buf[i+j] = (buf[i+j] ^ s[j]);
    }
}

void Decrypt(const char *srcfile,const char *dstfile) {
    for(int i=0; i<256; i++)
        InvSubTable[SubTable[i]] = i;
    FILE *fp=fopen(srcfile,"rb");

    fseek(fp, 0, SEEK_END);
    unsigned int Len = ftell(fp);
    unsigned char *buf = (unsigned char *)malloc(Len);
    memset(buf, 0, Len);
    fseek(fp, 0, SEEK_SET);
    fread(buf, 1, Len, fp);
    fclose(fp);

    struct AES_ctx ctx;

    for(int i=0; i<Len; i+=0x200) {
        AES_init_ctx_iv(&ctx, AES_KEY, CTR_IV);
        cc_aes_ctr(&ctx,buf+i,(Len - i) > 0x200 ? 0x200: (Len-i));
    }

    for(int i=0; i<Len; i++) {
        buf[i] = InvSubTable[buf[i]];
    }

    FILE *fp2=fopen(dstfile,"wb");
    fwrite(buf,1,Len,fp2);
    fclose(fp2);

    free(buf);
    buf = NULL;
    return;
}

int main(void) {
    Decrypt("DSRD.enc","DSRD.dec");
}