240 lines
7.1 KiB
C
240 lines
7.1 KiB
C
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#include <stdio.h>
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#include <string.h>
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#define SHORTEN_PREAMBLE_TO_32 0
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typedef unsigned char byte;
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typedef unsigned short uint16;
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uint16 crc(byte *data, int len)
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{
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byte i, x, crcdata;
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uint16 crcReg = 0xFFFF;
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for (x = 0; x < len; x++)
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{
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crcdata = data[x];
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for (i = 0; i < 8; i++)
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{
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if (((crcReg & 0x8000) >> 8) ^ (crcdata & 0x80))
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crcReg = (crcReg << 1) ^ 0x8005;
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else
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crcReg = (crcReg << 1);
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crcdata <<= 1;
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}
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}
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return crcReg;
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}
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byte str2byte(char str[8])
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{
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int ret = 0, i;
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for(i = 0; i < 8; i++)
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if (str[i]=='1') ret |= (1<<(7-i));
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return ret;
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}
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void print_binary(byte inpt)
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{
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int i;
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for(i = 0; i < 8; i++)
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if (inpt & (1<<(7-i))) putchar('1');
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else putchar('0');
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}
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void print_preamble_nibbles(int count)
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{
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int i;
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for (i = 0; i < count; i++)
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printf("1010");
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}
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int find_preamble_start_in_bit(char *string, int len)
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{
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char homematic_sync[] = "11101001110010101110100111001010";
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for(int i = 0, j = 0; i < len; i++)
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{
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if(string[i] == homematic_sync[j])
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{
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j++;
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if(j == 32 && i>= 63) return i-63;
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}
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else j = 0;
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}
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return -1; //not found
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}
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void xor_lfsr(char *string)
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{
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int i, j, x, len = strlen(string);
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byte polynomial[9] = {0, 0, 0, 1, 0, 0, 0, 0, 1};
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byte lfsr_state[9];
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byte first_bit;
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// Init with 8x 1 Bit
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memset(lfsr_state, 1, 9);
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for(j = 0; j < 8; j++)
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if(string[j]=='1')
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string[j]='0';
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else
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string[j]='1';
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for(x = 8; x < len-7; x += 8)
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{
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for(i = 0; i < 8; i++)
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{
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first_bit = 255;
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for(j = 8; j >= 0; j--)
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if(polynomial[j] && lfsr_state[j])
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{
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if(first_bit == 255)
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first_bit = 1;
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else
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first_bit = (first_bit==1) ? 0 : 1;
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}
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if(first_bit == 255)
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first_bit = 0;
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// Clock
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for(j = 8; j >= 0; j--)
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lfsr_state[j] = lfsr_state[j-1];
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lfsr_state[0] = first_bit;
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}
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// Xor
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for(j = 0; j < 8; j++)
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if(lfsr_state[j+1] == 1)
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if(string[x+j]=='1')
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string[x+j]='0';
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else
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string[x+j]='1';
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}
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}
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int main(int argc, char **argv)
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{
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int i, j, max, offset, len, preamble_additional_length;
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byte dec[1024]={0}, enc[1024]={0}, crc_ok;
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char string[65536]={0};
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uint16 crcvalue;
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offset = 8; // Preamble + Sync
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// Copy data (argv[2]) to string if length is ok, shorten to multiple of 8 bit
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if (strlen(argv[2]) > 8192*8 || strlen(argv[2]) < 4) return -1;
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len = strlen(argv[2]);
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i = find_preamble_start_in_bit(argv[2], len);
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if(i < 0) return 0; // preamble+sync not found or wrong length
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preamble_additional_length = i;
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len = (len-i)-(len-i)%8;
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memcpy(string, argv[2]+i, len);
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if (argc>2)
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{
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if (argv[1][0]=='d')
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{
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// Apply datawhitening
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xor_lfsr(string+64);
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// Pack to bytes
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for (i = 0; i < strlen(string)-3; i+=8)
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enc[i/8] = str2byte(&string[i]);
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max = i/8;
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memcpy(&dec, &enc, 1024);
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// Check CRC
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crcvalue = crc(&dec[8], max-2-8);
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crc_ok = 0;
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if( ((crcvalue >> 8) & 0xFF) == dec[max-2] && (crcvalue & 0xFF) == dec[max-1]) crc_ok = 1;
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/*
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* byte[] Dec = new byte[Enc.Length];
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* Dec[0] = Enc[0]; //Packet length
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* Dec[1] = (byte)((~Enc[1]) ^ 0x89);
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* int j;
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* for (j = 2; j < Dec[0]; j++)
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* Dec[j] = (byte)((Enc[j-1] + 0xdc) ^ Enc[j]);
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* Dec[j] = (byte)(Enc[j] ^ Dec[2]);
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*/
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// Decrypt
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dec[offset+0] = enc[offset+0];
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dec[offset+1] = (~enc[offset+1])^0x89;
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for(i = offset + 2; i < max - 3; i++)
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dec[i] = (enc[i-1]+0xdc) ^ enc[i];
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dec[i] = enc[i] ^ dec[offset+2];
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// Recompute CRC and overwrite with FAKE-CRC, if CRC was OK before
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if(crc_ok)
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{
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crcvalue = crc(&dec[8], max-2-8);
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dec[max-1] = crcvalue & 0xFF;
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dec[max-2] = (crcvalue >> 8) & 0xFF;
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}
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else
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{
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dec[max-1] = 0x0F; // Set magic code for wrong CRC
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dec[max-2] = 0xD0;
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}
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// Prepend preamble longer than 32 bits
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if(0 == SHORTEN_PREAMBLE_TO_32 && preamble_additional_length > 0)
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print_preamble_nibbles(preamble_additional_length/4);
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for(i = 0; i < max; i++)
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print_binary(dec[i]);
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}
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else
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{
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// Pack to bytes
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for (i = 0; i < strlen(string)-3; i+=8)
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dec[i/8] = str2byte(&string[i]);
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max = i/8;
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memcpy(&enc, &dec, 1024);
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/*
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* byte[] Dec = new byte[Enc.Length];
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* Dec[0] = Enc[0]; //Packet length
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* Dec[1] = (byte)((~Enc[1]) ^ 0x89);
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* int j;
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* for (j = 2; j < Dec[0]; j++)
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* Dec[j] = (byte)((Enc[j-1] + 0xdc) ^ Enc[j]);
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* Dec[j] = (byte)(Enc[j] ^ Dec[2]);
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*/
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// Encrypt
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enc[offset+0] = dec[offset+0];
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enc[offset+1] = ~(dec[offset+1])^0x89;
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for(i = offset + 2; i < max - 3; i++)
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enc[i] = (enc[i-1]+0xdc) ^ dec[i];
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enc[i] = dec[i] ^ dec[offset+2];
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// Overwrite with correct CRC
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crcvalue = crc(&enc[8], max-2-8);
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enc[max-1] = crcvalue & 0xFF;
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enc[max-2] = (crcvalue >> 8) & 0xFF;
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// Convert to string
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memset(string, 0, 65536);
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for(i = 0; i < max; i++)
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{
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for(j = 0; j < 8; j++)
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if(enc[i] & (1<<(7-j))) string[i*8+j]='1';
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else string[i*8+j]='0';
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}
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// Apply datawhitening
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xor_lfsr(string+64);
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// Prepend preamble longer than 32 bits
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if(0 == SHORTEN_PREAMBLE_TO_32 && preamble_additional_length > 0) // Add preamble longer than 32 bits
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print_preamble_nibbles(preamble_additional_length/4);
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// Print bits and duplicate last bit
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printf("%s%c\n", string, string[strlen(string)-1]);
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}
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}
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else printf("Usage: %s <d/e> <bit sequence>\n\td - decode\n\te - encode\n\tbit sequence as string of 0 and 1.\n", argv[0]);
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return 0;
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}
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