ATJ first stage bootloader scrambler, mostly

rb_atj_crypt.c

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

unsigned char xor_key[512] =
{
    0x9b, 0x94, 0xf6, 0x9e, 0x2f, 0x0a, 0x40, 0xfd, 0x9a, 0x78, 0x2c, 0xdd, 0x4f, 0x96, 0x5e, 0xdd, 
    0xc9, 0x01, 0xd3, 0x9d, 0x71, 0x8f, 0xda, 0xbb, 0xc1, 0xdf, 0x5f, 0x01, 0xaa, 0x35, 0x6f, 0xdc, 
    0x33, 0x85, 0xf9, 0x10, 0x64, 0xce, 0xd2, 0xab, 0x62, 0xaa, 0xfc, 0x37, 0xdb, 0x22, 0x28, 0x34, 
    0xa4, 0xc6, 0x79, 0xc6, 0xa1, 0xfe, 0x8b, 0xaa, 0xe6, 0x9b, 0xb4, 0x6e, 0x1b, 0xb1, 0x8a, 0xe2, 
    0x25, 0xa9, 0xa5, 0xca, 0x03, 0x92, 0xa6, 0xd5, 0xf5, 0xb8, 0x77, 0xd3, 0xe4, 0x78, 0xd5, 0x22, 
    0xfe, 0x52, 0x0c, 0x69, 0xa1, 0x40, 0x02, 0x89, 0x7a, 0x46, 0x77, 0xd1, 0xee, 0x4b, 0x8b, 0x72, 
    0xb8, 0x27, 0x81, 0x32, 0xd4, 0xfd, 0xc2, 0x64, 0x9c, 0xcb, 0x25, 0x17, 0x32, 0x3f, 0x6d, 0x8e, 
    0x1d, 0xcd, 0x14, 0xf0, 0x37, 0xfe, 0x47, 0x41, 0xc6, 0x0b, 0x31, 0x91, 0xe9, 0xaa, 0x7c, 0x73, 
    0x36, 0x28, 0x15, 0xb1, 0xa1, 0xb8, 0x30, 0x3e, 0x9f, 0x0b, 0x8d, 0x6c, 0x8c, 0x20, 0xf9, 0x5f, 
    0x4a, 0x5e, 0x17, 0xc2, 0x2c, 0xe0, 0x60, 0xb8, 0x12, 0x10, 0x69, 0x16, 0xd5, 0x77, 0x64, 0xcf, 
    0xe5, 0xd3, 0xea, 0xb0, 0x30, 0x6a, 0xf8, 0x4d, 0x46, 0x9f, 0x37, 0x3b, 0xbb, 0xc3, 0x80, 0x7f, 
    0xcd, 0x2d, 0x9f, 0x47, 0x47, 0x8d, 0x57, 0xd8, 0xa6, 0x7d, 0xa7, 0xc8, 0x79, 0x59, 0x4c, 0x6d, 
    0x0e, 0x51, 0x87, 0x95, 0x4a, 0xbc, 0x20, 0x77, 0xd9, 0xaf, 0xab, 0xea, 0x88, 0xcf, 0x0a, 0xd5, 
    0xee, 0x63, 0x33, 0xe7, 0x52, 0xae, 0x34, 0x88, 0xc9, 0x7b, 0x74, 0x0f, 0x9f, 0xf9, 0x3b, 0x35, 
    0xf8, 0xc9, 0x74, 0xc9, 0xb7, 0x56, 0xb2, 0xa6, 0x9f, 0x65, 0x72, 0xe3, 0xb8, 0xed, 0xa0, 0x49, 
    0xf5, 0x28, 0x5c, 0x0a, 0x13, 0xea, 0xfd, 0xaf, 0xc4, 0x32, 0x56, 0x53, 0x0d, 0xfe, 0x39, 0x0f, 
    0xed, 0x64, 0x3a, 0xb5, 0x3f, 0xdf, 0xb5, 0xc1, 0xe1, 0xe7, 0x13, 0x8c, 0x16, 0xc4, 0x48, 0xc3, 
    0x29, 0xa3, 0xa0, 0x18, 0x54, 0xea, 0xbc, 0x37, 0xdf, 0xc9, 0xd7, 0xfc, 0x8c, 0x11, 0x4f, 0xe3, 
    0x33, 0x4a, 0x60, 0xc0, 0xaa, 0x00, 0x32, 0xb0, 0xe7, 0x5d, 0x16, 0x4f, 0x69, 0xfd, 0x0c, 0x2b, 
    0xd4, 0xfd, 0x8a, 0x79, 0xdb, 0x55, 0x78, 0x07, 0x62, 0x68, 0x7f, 0x72, 0xe4, 0xda, 0x83, 0x99, 
    0x13, 0xa2, 0x6e, 0x51, 0xbf, 0x60, 0x30, 0x5b, 0xf9, 0xf0, 0x04, 0x93, 0x78, 0x3f, 0xf4, 0x69, 
    0x3c, 0x5d, 0x9f, 0x95, 0x70, 0xd4, 0x3a, 0x07, 0x95, 0x39, 0xd5, 0x1d, 0xdd, 0x00, 0xdf, 0x19, 
    0xd5, 0x94, 0xed, 0xd2, 0x47, 0xa8, 0xb7, 0xaa, 0x5f, 0xc7, 0x63, 0xbf, 0x0c, 0x33, 0x07, 0x66, 
    0xa9, 0xec, 0x69, 0xd5, 0xdd, 0x0f, 0x09, 0x1f, 0xc0, 0x61, 0x61, 0x66, 0x3f, 0x2c, 0x6b, 0x4b, 
    0xc1, 0x4a, 0x64, 0xaa, 0x0b, 0x7f, 0xd0, 0x85, 0x60, 0x0c, 0xbe, 0x3d, 0xed, 0x80, 0x4d, 0x08, 
    0x65, 0xd2, 0x6f, 0x9f, 0xe9, 0xad, 0xed, 0x37, 0x2a, 0x0b, 0xab, 0x00, 0xd1, 0x05, 0x2e, 0x18, 
    0x1f, 0xe9, 0x5b, 0x41, 0xd0, 0x8e, 0x81, 0xd4, 0x46, 0xe4, 0x9a, 0x74, 0xe3, 0xcf, 0xce, 0x38, 
    0xb7, 0x36, 0x39, 0x5c, 0x5b, 0x57, 0xee, 0x37, 0x1c, 0x5d, 0x3c, 0x6d, 0x5c, 0x34, 0x30, 0x66, 
    0x36, 0x9c, 0x5a, 0xff, 0x61, 0x7c, 0xd4, 0x7f, 0x57, 0x79, 0x81, 0xcc, 0xb6, 0xc8, 0x93, 0xdf, 
    0xe6, 0x40, 0x50, 0x75, 0xfc, 0xb4, 0x15, 0x07, 0xde, 0x7f, 0x9b, 0xfd, 0xa8, 0x60, 0x79, 0x1f, 
    0x4f, 0x89, 0xea, 0x4c, 0x85, 0xf2, 0xd1, 0x6e, 0xdc, 0xf3, 0xfa, 0xad, 0x2d, 0x12, 0xa3, 0xe3, 
    0x3b, 0x1a, 0x3b, 0x50, 0x94, 0x6d, 0x69, 0x90, 0xb8, 0x9a, 0x50, 0xc9, 0x7d, 0x32, 0x12, 0x29,
};

static unsigned char *read_it(const char *filename, int *length)
{
    FILE *fp = fopen(filename, "rb");
    if(fp == NULL)
    {
        printf("Cannot open file for reading: %m\n");
        return NULL;
    }
    fseek(fp, 0, SEEK_END);
    *length = ftell(fp);
    fseek(fp, 0, SEEK_SET);
    unsigned char *data = malloc(*length);
    fread(data, 1, *length, fp);
    fclose(fp);
    return data;
}

static int write_it(const char *filename, unsigned char *data, int length)
{
    FILE *fp = fopen(filename, "wb");
    if(fp == NULL)
    {
        printf("Cannot open file for writing: %m\n");
        return 2;
    }
    fwrite(data, 1, length, fp);
    fclose(fp);
    return 0;
}

static void perm_it(unsigned char *data, int length)
{
    for(int i = 0; (i + 12) < length; i += 12)
    {
        unsigned char perm[8];
        perm[0] = data[i + 1];
        perm[1] = data[i + 7];
        perm[2] = data[i + 2];
        perm[3] = data[i + 4];
        perm[4] = data[i + 0];
        perm[5] = data[i + 6];
        perm[6] = data[i + 3];
        perm[7] = data[i + 5];
        for(int j = 0; j < 8; j++)
            data[i + j] = perm[j];
    }
}

static void unperm_it(unsigned char *data, int length)
{
    for(int i = 0; (i + 12) < length; i += 12)
    {
        unsigned char perm[8];
        perm[0] = data[i + 4];
        perm[1] = data[i + 0];
        perm[2] = data[i + 2];
        perm[3] = data[i + 6];
        perm[4] = data[i + 3];
        perm[5] = data[i + 7];
        perm[6] = data[i + 5];
        perm[7] = data[i + 1];
        for(int j = 0; j < 8; j++)
            data[i + j] = perm[j];
    }
}

static void xor_it(unsigned char *data, int length)
{
    for(int i = 0; i < length; i += 4)
    {
        unsigned char Ekey = xor_key[xor_key[data[i]] + 256];
        for(int j = 1; j < 4; j++)
            data[i + j] ^= Ekey;
    }
}

static void unxor_it(unsigned char *data, int length)
{
    xor_it(data, length);
}

static int encrypt(const char *in_file, const char *out_file)
{
    // read file
    int length;
    unsigned char *data = read_it(in_file, &length);
    if(data == NULL) 
        return 1;
    int rounded_len = ( (length + 511) / 512 ) * 512;
    data = realloc(data, rounded_len + 10);
    // random padding
    for(int i = length; i < rounded_len; i++)
        data[i] = rand();
    // XOR the file
    xor_it(data, rounded_len);
    // apply permutation
    perm_it(data, rounded_len);
    // write file
    return write_it(out_file, data, rounded_len);
}

int decrypt(const char *in_file, const char *out_file)
{
    // read file
    int length;
    unsigned char *data = read_it(in_file, &length);
    if(data == NULL) 
        return 1;
    if(length % 512)
        printf("Warning: file size is not a multiple of 512!");
    // apply permutation
    unperm_it(data, length);
    // XOR the file
    unxor_it(data, length);
    // write file
    return write_it(out_file, data, length);
}

int usage(void)
{
    printf("usage: rb_atj_crypt [-e|-d] in_file out_file\n");
    return 1;
}

int main(int argc, char **argv)
{
    srand(time(NULL));
    if(argc != 4)
        return usage();
    if(strcmp(argv[1], "-e") == 0)
        return encrypt(argv[2], argv[3]);
    if(strcmp(argv[1], "-d") == 0)
        return decrypt(argv[2], argv[3]);
    printf("Unknown command '%s'\n", argv[1]);
    return 1;
}