git.zerfleddert.de Git - hmcfgusb/blob - hm.c

   1 /* HomeMatic protocol-functions
   2  *
   3  * Copyright (c) 2014-15 Michael Gernoth <michael@gernoth.net>
   4  *
   5  * Permission is hereby granted, free of charge, to any person obtaining a copy
   6  * of this software and associated documentation files (the "Software"), to
   7  * deal in the Software without restriction, including without limitation the
   8  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
   9  * sell copies of the Software, and to permit persons to whom the Software is
  10  * furnished to do so, subject to the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be included in
  13  * all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  18  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <unistd.h>
  27 #include <stdint.h>
  28 #include <string.h>
  29 #include <strings.h>
  30 #include <errno.h>
  31 #include <sys/types.h>
  32 #include <sys/time.h>
  33
  34 #include "aes.h"
  35 #include "hexdump.h"
  36 #include "hm.h"
  37
  38 static int debug = 0;
  39
  40 uint8_t* hm_sign(uint8_t *key, uint8_t *challenge, uint8_t *m_frame, uint8_t *exp_auth, uint8_t *resp)
  41 {
  42         uint8_t signkey[16];
  43         WORD ks[60];
  44         struct timeval tv;
  45         int i;
  46
  47         printf("AES-request with challenge: %02x%02x%02x%02x%02x%02x\n",
  48                         challenge[0], challenge[1], challenge[2],
  49                         challenge[3], challenge[4], challenge[5]);
  50
  51         /*
  52          * Build signing key by XORing the first 6 bytes of
  53          * the key with the challenge.
  54          */
  55         memcpy(signkey, key, sizeof(signkey));
  56         for (i = 0; i < 6; i++) {
  57                 signkey[i] ^= challenge[i];
  58         }
  59         aes_key_setup(signkey, ks, 128);
  60
  61         /*
  62          * Generate payload for first encryption.
  63          */
  64         gettimeofday(&tv, NULL);
  65         resp[0] = tv.tv_sec >> 24 & 0xff;
  66         resp[1] = tv.tv_sec >> 16 & 0xff;
  67         resp[2] = tv.tv_sec >> 8 & 0xff;
  68         resp[3] = tv.tv_sec & 0xff;
  69         resp[4] = tv.tv_usec >> 8 & 0xff;
  70         resp[5] = tv.tv_usec & 0xff;
  71         memcpy(&(resp[6]), &(m_frame[MSGID]), 10);
  72
  73         if (debug)
  74                 hexdump(resp, 16, "P   > ");
  75
  76         aes_encrypt(resp, resp, ks, 128);
  77
  78         if (debug)
  79                 hexdump(resp, 16, "Pe  > ");
  80
  81         /*
  82          * Device has to answer with the first 4 bytes of the
  83          * encrypted payload to authenticate, so pass them to
  84          * the caller.
  85          */
  86
  87         if (exp_auth) {
  88                 memcpy(exp_auth, resp, 4);
  89         }
  90
  91         /*
  92          * XOR parameters of the m_frame to the payload.
  93          */
  94         for (i = 0; i < PAYLOADLEN(m_frame) - 1; i++) {
  95                 if (i == 16) {
  96                         break;
  97                 }
  98
  99                 resp[i] ^= m_frame[PAYLOAD + 1+ i];
 100         }
 101
 102         if (debug)
 103                 hexdump(resp, 16, "Pe^ > ");
 104
 105         /*
 106          * Encrypt payload again
 107          */
 108         aes_encrypt(resp, resp, ks, 128);
 109
 110         if (debug)
 111                 hexdump(resp, 16, "Pe^e> ");
 112
 113         return resp;
 114 }