epan/crypt/dot11decrypt_gcmp.c

   1 /* dot11decrypt_gcmp.c
   2  *
   3  * Wireshark - Network traffic analyzer
   4  * By Gerald Combs <gerald@wireshark.org>
   5  * Copyright 1998 Gerald Combs
   6  *
   7  * SPDX-License-Identifier: GPL-2.0-or-later
   8  */
   9
  10 /****************************************************************************/
  11 /* File includes                                                                */
  12 #include "config.h"
  13
  14 #include "dot11decrypt_debug.h"
  15 #include "dot11decrypt_int.h"
  16 #include "dot11decrypt_system.h"
  17 #include "dot11decrypt_util.h"
  18
  19 #include <wsutil/wsgcrypt.h>
  20
  21 /****************************************************************************/
  22 /*      Internal definitions                                                    */
  23
  24 /****************************************************************************/
  25 /* Internal macros                                                              */
  26
  27 #define READ_6(b0, b1, b2, b3, b4, b5) \
  28         ((((uint64_t)((uint16_t)((b4 << 0) | (b5 << 8)))) << 32) | \
  29             ((uint32_t)((b0 << 0) | (b1 << 8) | (b2 << 16) | (b3 << 24))))
  30
  31 /****************************************************************************/
  32 /* Internal function prototypes declarations                                    */
  33
  34 /****************************************************************************/
  35 /* Function definitions                                                 */
  36
  37 /* From IEEE 802.11 2016 Chapter 12.5.5.3.4 Construct GCM nonce */
  38 static void
  39 gcmp_construct_nonce(
  40         PDOT11DECRYPT_MAC_FRAME wh,
  41         uint64_t pn,
  42         uint8_t nonce[12])
  43 {
  44         /* Nonce: A2 | PN */
  45         DOT11DECRYPT_ADDR_COPY(nonce, wh->addr2);
  46         nonce[6] = (uint8_t)(pn >> 40);
  47         nonce[7] = (uint8_t)(pn >> 32);
  48         nonce[8] = (uint8_t)(pn >> 24);
  49         nonce[9] = (uint8_t)(pn >> 16);
  50         nonce[10] = (uint8_t)(pn >> 8);
  51         nonce[11] = (uint8_t)(pn >> 0);
  52 }
  53
  54 int Dot11DecryptGcmpDecrypt(
  55         uint8_t *m,
  56         int mac_header_len,
  57         int len,
  58         uint8_t *TK1,
  59         int tk_len)
  60 {
  61         PDOT11DECRYPT_MAC_FRAME wh;
  62         uint8_t aad[30];
  63         uint8_t nonce[12];
  64         uint8_t mic[16];
  65         ssize_t data_len;
  66         size_t aad_len;
  67         int z = mac_header_len;
  68         gcry_cipher_hd_t handle;
  69         uint64_t pn;
  70         uint8_t *ivp = m + z;
  71
  72         wh = (PDOT11DECRYPT_MAC_FRAME )m;
  73         data_len = len - (z + DOT11DECRYPT_GCMP_HEADER + sizeof(mic));
  74         if (data_len < 1) {
  75                 return 0;
  76         }
  77
  78         memcpy(mic, m + len - sizeof(mic), sizeof(mic));
  79         pn = READ_6(ivp[0], ivp[1], ivp[4], ivp[5], ivp[6], ivp[7]);
  80         gcmp_construct_nonce(wh, pn, nonce);
  81         dot11decrypt_construct_aad(wh, aad, &aad_len);
  82
  83         if (gcry_cipher_open(&handle, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_GCM, 0)) {
  84                 return 1;
  85         }
  86         if (gcry_cipher_setkey(handle, TK1, tk_len)) {
  87                 goto err_out;
  88         }
  89         if (gcry_cipher_setiv(handle, nonce, sizeof(nonce))) {
  90                 goto err_out;
  91         }
  92         if (gcry_cipher_authenticate(handle, aad, aad_len)) {
  93                 goto err_out;
  94         }
  95         if (gcry_cipher_decrypt(handle, m + z + DOT11DECRYPT_GCMP_HEADER, data_len, NULL, 0)) {
  96                 goto err_out;
  97         }
  98         if (gcry_cipher_checktag(handle, mic, sizeof(mic))) {
  99                 goto err_out;
 100         }
 101
 102         /* TODO replay check    (IEEE 802.11i-2004, pg. 62)                     */
 103         /* TODO PN must be incremental (IEEE 802.11i-2004, pg. 62)              */
 104
 105         gcry_cipher_close(handle);
 106         return 0;
 107 err_out:
 108         gcry_cipher_close(handle);
 109         return 1;
 110 }