/* phatsig v0.1 by bushing and rmini
 * This software is in the public domain -- take it and make something useful!
 * 
 * Requires two public-domain libraries:
 * libtomcrypt -- http://libtomcrypt.org/
 * libtommath  -- http://math.libtomcrypt.org/
 *
 * To build:
 * wget http://math.libtomcrypt.org/files/ltm-0.36.tar.bz2
 * wget http://libtomcrypt.org/files/crypt-1.06.tar.bz2
 * tar xjvf ltm-0.36.tar.bz2
 * tar xjvf crypt-1.06.tar.bz2
 * cd libtommath-0.36/;make;cd ..
 * cd libtomcrypt-1.06/;CFLAGS="-DLTM_DESC -I../libtommath-0.36" EXTRALIBS="-L../libtommath-0.36 -ltommath" make;cd ..
 * gcc -Llibtommath-0.36/ -Llibtomcrypt-1.06/ -Wall -I libtomcrypt-1.06/src/headers/ -o phatsig phatsig.c -ltomcrypt -ltommath
 * 
 * This code should be portable to any platform that can compile libtomcrypt
 * (which is apparently practically anything).  However, the sig_struct_tag assumes
 * that an unsigned int is 32 bits, using little-endian byte ordering.  Modify
 * appropriately if your architecture is different.
 */

 /* Win32 Port - Visual Studio 6.0 using C++ Service Pack 5
  * Modified by: VorTechS
  * Modified date: May 4th 2007
  * Major help: sbingner, preparing for use as DLL
  * More help: Grimthorpe, preparing for use as importable unmanaged DLL
  */
 
#define LTM_DESC
#define SIG_BUF_LEN 400

#include <string.h>
#include <stdio.h>
#include <assert.h>
#include <tomcrypt.h>
#include <sys/stat.h>
#include <wtypes.h>

void scramble_loop(int input_byte, unsigned char *real_sig_buf, int *c, 
		   unsigned char *bitmask1, unsigned char *bitmask2);
int get_md5_hash_for_file(char *filename, unsigned char *hash_buf);
int get_file_size(char *filename);
int bizarro_scramble(unsigned char *input, unsigned int length, unsigned char *output);

unsigned char private_key_der[]={  // i found this written on scrap of paper, up the street...
  0x30,0x82,0x02,0x5c,0x02,0x01,0x00,0x02,0x81,0x81,0x00,0xed,0x37,0xfb,0x9d,0x19,
  0xe7,0x3e,0xa6,0xf1,0x1d,0xae,0xa2,0x15,0x3a,0x0f,0x6d,0x89,0xda,0xb7,0xb4,0x95,
  0xd2,0x3d,0x8a,0xd3,0xdb,0x37,0x92,0xed,0x33,0x32,0x25,0xf3,0x30,0xea,0xdc,0xe7,
  0xb4,0x48,0xb3,0xaa,0xf8,0x2a,0x6c,0x40,0xd5,0x1b,0x5d,0xfb,0x71,0x08,0x74,0x1e,
  0xfe,0x45,0x13,0xf8,0x2d,0xbc,0x26,0x31,0x04,0x1e,0x0e,0x58,0xac,0x04,0xdb,0xbd,
  0x97,0xd8,0x08,0x7a,0x0e,0x03,0xf6,0xdf,0x60,0x78,0xfe,0x02,0x22,0xc8,0x95,0xbb,
  0x9d,0xf8,0x67,0xdb,0x44,0x6b,0x5f,0x53,0x58,0xb2,0x15,0xcd,0x5c,0xcb,0xaa,0xd4,
  0xa1,0x5a,0xd9,0xed,0xca,0x1e,0xd1,0xe3,0xe7,0x6b,0x1f,0x8e,0x0c,0xfc,0x54,0xb0,
  0x37,0x91,0x06,0x01,0x4d,0x81,0xcc,0x7f,0xcc,0x14,0xab,0x02,0x03,0x01,0x00,0x01,
  0x02,0x81,0x80,0x1b,0x2a,0x4b,0x0d,0x1d,0x97,0x46,0xac,0x75,0x76,0x31,0xb6,0x6b,
  0xf9,0xdf,0x24,0x6b,0x21,0xf9,0xe1,0x9b,0x3a,0x9d,0x43,0x95,0xa9,0x47,0xfe,0xf2,
  0x5c,0xe7,0x84,0x43,0x0a,0x3a,0x0b,0x1c,0x19,0xa0,0x2d,0xbb,0x09,0x7a,0x4a,0x35,
  0x4e,0x72,0x38,0xdb,0xff,0x80,0xb9,0x53,0x87,0x48,0xbf,0xd5,0xae,0xdf,0x19,0xfc,
  0x88,0xfd,0x2b,0xec,0xf7,0xcc,0x56,0x30,0xc7,0xf8,0x6a,0x53,0x4d,0xe6,0x15,0xfe,
  0x12,0xfd,0xcd,0x29,0x8f,0xd2,0x8c,0xf6,0x1b,0x42,0x3b,0x6f,0xff,0x97,0xb6,0x72,
  0x08,0x05,0x94,0xfe,0x7e,0x66,0x7d,0x8e,0x6f,0x62,0x49,0x24,0x11,0x3e,0x32,0xa4,
  0x3b,0xe0,0x24,0x60,0xd2,0xba,0xb5,0xa7,0x88,0x5e,0xa8,0xd0,0x2c,0xda,0x9e,0x7c,
  0x46,0xad,0x41,0x02,0x41,0x00,0xf9,0x34,0xef,0xe7,0x03,0x84,0xb6,0xaf,0x9d,0x42,
  0x2d,0x90,0xf7,0xc4,0x44,0x87,0x36,0x07,0xac,0xbb,0x1d,0x88,0x71,0x7c,0xd9,0x82,
  0x36,0xc1,0xcf,0xa8,0xf9,0x32,0x3a,0xfc,0x28,0x78,0x98,0x7d,0x61,0xf3,0xe1,0x7a,
  0x92,0xb9,0x8b,0x54,0x25,0x24,0xea,0xf0,0xd8,0x8b,0x68,0x07,0xb7,0x65,0x65,0xe0,
  0x51,0x92,0xdf,0x8e,0x3b,0x4b,0x02,0x41,0x00,0xf3,0xaf,0x63,0x57,0xad,0x7b,0x80,
  0x81,0x6d,0xf6,0x99,0x4f,0x48,0xb0,0x81,0x46,0x9e,0xe8,0xed,0xa4,0x39,0x0a,0x7f,
  0x6c,0x8d,0x10,0xb4,0x30,0x07,0x33,0x6f,0xb8,0x9f,0xbc,0x42,0x52,0xd8,0xe1,0x77,
  0x54,0x25,0x21,0x51,0x7f,0x3e,0x30,0xae,0x50,0x90,0x1b,0x4d,0x8f,0x03,0x48,0x5e,
  0x7b,0x5d,0x2f,0xa0,0x32,0xd7,0x6d,0x50,0x21,0x02,0x40,0x46,0x41,0x72,0x50,0xc2,
  0x61,0x2b,0xcf,0x9e,0x9a,0x05,0x96,0x95,0x03,0x33,0xfe,0x9a,0x70,0xd7,0x75,0x79,
  0x01,0xfa,0x5c,0xa4,0x45,0x5d,0x82,0x8e,0x34,0xa8,0xec,0x4c,0x4c,0xc2,0x6c,0x1d,
  0x31,0x5b,0xe8,0x11,0x6d,0x28,0xe8,0x3e,0x2b,0x5e,0xbd,0x65,0xae,0xb8,0x9d,0xb4,
  0x9a,0x58,0x4d,0xb1,0xc6,0xe7,0xb8,0x6c,0x66,0x00,0xb9,0x02,0x41,0x00,0xca,0xcf,
  0x5d,0xce,0xcb,0x03,0xce,0x9f,0xe9,0xf5,0x23,0x03,0x69,0x6b,0xfd,0x2b,0xd9,0x75,
  0xe2,0xd2,0x9a,0xe6,0xb1,0xc6,0x96,0x61,0x20,0x96,0x18,0x68,0x26,0xc3,0x71,0xae,
  0x2d,0x44,0xe6,0x5c,0x40,0x04,0x38,0x22,0xd2,0xc1,0x23,0xf1,0x40,0x22,0xac,0xcd,
  0x0c,0x6f,0xca,0x3b,0xa0,0xe6,0xeb,0x57,0x87,0xec,0xc8,0x7e,0xa2,0x01,0x02,0x40,
  0x02,0x1f,0x0d,0x66,0xf3,0xbd,0x46,0x90,0x62,0x01,0x96,0x5d,0x1c,0x7c,0x46,0x2b,
  0xd6,0xc2,0x91,0xa9,0xcd,0x86,0xdc,0xd1,0x9c,0x70,0xe2,0x14,0xbc,0x5c,0x82,0xae,
  0x71,0x0e,0x1c,0x64,0xc9,0x05,0x70,0x5c,0xf6,0xc8,0x82,0x87,0xbb,0xcd,0xa6,0x39,
  0x9c,0x14,0x9e,0xcd,0xb5,0x92,0x68,0x3d,0x50,0x1f,0x72,0x2c,0xc8,0xeb,0xc9,0x7d};

unsigned char asn1_block[128] = // this block means "i am an MD5 hash..."
  {0x00,0x01,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
   0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
   0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
   0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
   0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
   0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0x00,0x30,0x20,
   0x30,0x0c,0x06,0x08,0x2a,0x86,0x48,0x86,0xf7,0x0d,0x02,0x05,0x05,0x00,0x04,0x10,
   0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff};

struct sig_struct_tag {
  unsigned int id1, id2, id3, hash_type, reserved, length;
  unsigned char rsa_sig[128];
  unsigned int footer;
} unscrambled_sig;

rsa_key key;
int hash_idx, prng_idx;

int init_crypto() {
  /* register prng/hash */
  if (register_prng(&sprng_desc) == -1)
    return 0;

  /* register a math library (in this case LibTomMath)  */
  ltc_mp = ltm_desc;
  if (register_hash(&md5_desc) == -1)
    return 0;
  
  hash_idx = find_hash("md5");
  prng_idx = find_prng("sprng");

  rsa_import(private_key_der,sizeof(private_key_der),&key);
  return 1;
}


DWORD sign_file(char *file_name, char *sig_file_name) {
  int output_length_in_bits;
  unsigned long out_len=128;
  unsigned char file_hash[16];
  unsigned char * unscrambled_sig_ptr=(unsigned char *)&unscrambled_sig;
  unsigned char sig_buf[SIG_BUF_LEN];
  FILE *outfile;

  if(file_name==NULL || sig_file_name==NULL)
    return 0;

  memset(sig_buf, 0, SIG_BUF_LEN);

  init_crypto();
  
  if(!get_md5_hash_for_file(file_name,file_hash))
    return 0;

  memcpy(asn1_block+128-16,file_hash,16);

  unscrambled_sig.id1=1;  // these 3 numbers identify the key somehow out of a database
  unscrambled_sig.id2=2;
  unscrambled_sig.id3=2;
  unscrambled_sig.hash_type=5; // md5?
  unscrambled_sig.footer=0x80; // ?
  unscrambled_sig.length=get_file_size(file_name);

  rsa_exptmod(asn1_block,128,(unsigned char *)&unscrambled_sig.rsa_sig,&out_len,PK_PRIVATE,&key);

  output_length_in_bits=bizarro_scramble(unscrambled_sig_ptr,sizeof(unscrambled_sig),sig_buf);
  output_length_in_bits+=2;
  
  outfile=fopen(sig_file_name,"wb");
  fwrite(&output_length_in_bits,1,4,outfile);
  if((output_length_in_bits%8)!=0) output_length_in_bits+=8-(output_length_in_bits%8); // round up
  fwrite(sig_buf,1,(output_length_in_bits/8),outfile);
  fclose(outfile);
  return 1;
}

int get_md5_hash_for_file(char *filename, unsigned char *hash_buf) {
  FILE *infile;
  unsigned char read_buffer[1024];
  int bytes_read;
  hash_state md;
  
  if(!(infile=fopen(filename,"rb")))
    return 0;

  md5_init(&md);
  /* add the data */
  while(!feof(infile)) {
    bytes_read=fread(read_buffer,1,1024,infile);
    md5_process(&md, read_buffer, bytes_read);
  }
  fclose(infile);
  /* get the hash in out[0..15] */
  md5_done(&md, hash_buf);
  return 1;
}

int get_file_size(char *filename) {
  struct stat stat_struct;
  stat(filename,&stat_struct);
  return stat_struct.st_size;
}

unsigned char bitmask_0[4] =        { 0x00, 0x00, 0x00, 0x00 };
unsigned char bitmask_01041040[4] = { 0x01, 0x04, 0x10, 0x40 };
unsigned char bitmask_030c30c0[4] = { 0x03, 0x0c, 0x30, 0xc0 };
unsigned char bitmask_02082080[4] = { 0x02, 0x08, 0x20, 0x80 };
unsigned char bitmask_fcf3cf3f[4] = { 0xfc, 0xf3, 0xcf, 0x3f }; 


#define BUF_IDX(i) ((i) / 8)
#define BIT_IDX(i) (((i) / 2) % 4)

/* This code came to me in a dream ... or a nightmare ... */
int bizarro_scramble(unsigned char *input, unsigned int length, unsigned char *output) {
    int sign_bit;
    unsigned int i;
    int c;
    int null_count;
    int buf_idx, bit_idx;
    int cur_char;

    null_count = 0;
    c = 0;

    if ( length <= 0 )
        return 0;

    for ( i = 0; i < length; i++ ) {

        if ( input[i] == 0 ) {
            null_count++;
            continue;
        }

        if ( null_count > 0 ) {
            scramble_loop(null_count, output, &c, bitmask_02082080, bitmask_030c30c0);

            if ( (null_count & 1) == 0 ) {
                c -= 2;

                output[BUF_IDX(c)] &= bitmask_fcf3cf3f[BIT_IDX(c)];
            }

            null_count = 0;
        }

        cur_char = (unsigned char)input[i];
        sign_bit = 0;
        if ( cur_char < 0 ) {
            sign_bit = 1;
            cur_char = -cur_char;
        }

        scramble_loop(cur_char + 1, output, &c, bitmask_01041040, bitmask_0);

        c -= 2;

        buf_idx = BUF_IDX(c);
        bit_idx = BIT_IDX(c);

        output[buf_idx] &= bitmask_fcf3cf3f[bit_idx];

        if ( sign_bit ) {
            output[buf_idx] |= bitmask_030c30c0[bit_idx];
        } else {
            output[buf_idx] |= bitmask_02082080[bit_idx];
        }
        c += 2;

    }

    if ( null_count > 0 ) {
        scramble_loop(null_count, output, &c, bitmask_02082080, bitmask_030c30c0);
        null_count++;
	if ( (null_count & 1) == 0 ) c -= 2;
  	//        if ( null_count & 1 == 0 ) c -= 2;
    }

    return c;
}

void scramble_loop(int input_byte, unsigned char *real_sig_buf, int *c, unsigned char *bitmask1, unsigned char *bitmask2) {
    int bit_idx, buf_idx;

    //    printf("scramble_loop(%d,%x,%x,%x,%x)\n",input_byte,real_sig_buf,*c,bitmask1,bitmask2);
    /*  printf("scramble_loop(%d,%x,%x,%x,%x)\n",input_byte,real_sig_buf,*c,*((unsigned int *)bitmask1),
     *((unsigned int *)bitmask2)); */

    while ( input_byte ) {
        buf_idx = BUF_IDX(*c);
        bit_idx = BIT_IDX(*c);

        if ( input_byte & 1 ) {
            real_sig_buf[buf_idx] |= bitmask1[bit_idx];
        } else {
            real_sig_buf[buf_idx] |= bitmask2[bit_idx];
        }

        *c += 2;
        input_byte >>= 1; // signed shift
    }
}

DWORD PASCAL phatsig_sign(const char *filename, const char *sigfilename)
  {
    return sign_file((char*)filename, (char*)sigfilename);
  }

/* vim: set sw=4 ai et si: */