lib/crypto/aes_ccm_128.c

   1 /*
   2    AES-CCM-128 (rfc 3610)
   3
   4    Copyright (C) Stefan Metzmacher 2012
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include "replace.h"
  21 #include "../lib/crypto/crypto.h"
  22 #include "lib/util/byteorder.h"
  23
  24 #define M_ ((AES_CCM_128_M - 2) / 2)
  25 #define L_ (AES_CCM_128_L - 1)
  26
  27 void aes_ccm_128_init(struct aes_ccm_128_context *ctx,
  28                       const uint8_t K[AES_BLOCK_SIZE],
  29                       const uint8_t N[AES_CCM_128_NONCE_SIZE],
  30                       size_t a_total, size_t m_total)
  31 {
  32         ZERO_STRUCTP(ctx);
  33
  34         AES_set_encrypt_key(K, 128, &ctx->aes_key);
  35         memcpy(ctx->nonce, N, AES_CCM_128_NONCE_SIZE);
  36         ctx->a_remain = a_total;
  37         ctx->m_remain = m_total;
  38
  39         /*
  40          * prepare B_0
  41          */
  42         ctx->B_i[0]  = L_;
  43         ctx->B_i[0] += 8 * M_;
  44         if (a_total > 0) {
  45                 ctx->B_i[0] += 64;
  46         }
  47         memcpy(&ctx->B_i[1], ctx->nonce, AES_CCM_128_NONCE_SIZE);
  48         RSIVAL(ctx->B_i, (AES_BLOCK_SIZE - AES_CCM_128_L), m_total);
  49
  50         /*
  51          * prepare X_1
  52          */
  53         AES_encrypt(ctx->B_i, ctx->X_i, &ctx->aes_key);
  54
  55         /*
  56          * prepare B_1
  57          */
  58         ZERO_STRUCT(ctx->B_i);
  59         if (a_total >= UINT32_MAX) {
  60                 RSSVAL(ctx->B_i, 0, 0xFFFF);
  61                 RSBVAL(ctx->B_i, 2, (uint64_t)a_total);
  62                 ctx->B_i_ofs = 10;
  63         } else if (a_total >= 0xFF00) {
  64                 RSSVAL(ctx->B_i, 0, 0xFFFE);
  65                 RSIVAL(ctx->B_i, 2, a_total);
  66                 ctx->B_i_ofs = 6;
  67         } else if (a_total > 0) {
  68                 RSSVAL(ctx->B_i, 0, a_total);
  69                 ctx->B_i_ofs = 2;
  70         }
  71
  72         /*
  73          * prepare A_i
  74          */
  75         ctx->A_i[0]  = L_;
  76         memcpy(&ctx->A_i[1], ctx->nonce, AES_CCM_128_NONCE_SIZE);
  77
  78         ctx->S_i_ofs = AES_BLOCK_SIZE;
  79 }
  80
  81 void aes_ccm_128_update(struct aes_ccm_128_context *ctx,
  82                         const uint8_t *v, size_t v_len)
  83 {
  84         size_t *remain;
  85
  86         if (v_len == 0) {
  87                 return;
  88         }
  89
  90         if (ctx->a_remain > 0) {
  91                 remain = &ctx->a_remain;
  92         } else {
  93                 remain = &ctx->m_remain;
  94         }
  95
  96         if (unlikely(v_len > *remain)) {
  97                 abort();
  98         }
  99
 100         if (ctx->B_i_ofs > 0) {
 101                 size_t n = MIN(AES_BLOCK_SIZE - ctx->B_i_ofs, v_len);
 102
 103                 memcpy(&ctx->B_i[ctx->B_i_ofs], v, n);
 104                 v += n;
 105                 v_len -= n;
 106                 ctx->B_i_ofs += n;
 107                 *remain -= n;
 108         }
 109
 110         if ((ctx->B_i_ofs == AES_BLOCK_SIZE) || (*remain == 0)) {
 111                 aes_block_xor(ctx->X_i, ctx->B_i, ctx->B_i);
 112                 AES_encrypt(ctx->B_i, ctx->X_i, &ctx->aes_key);
 113                 ctx->B_i_ofs = 0;
 114         }
 115
 116         while (v_len >= AES_BLOCK_SIZE) {
 117                 aes_block_xor(ctx->X_i, v, ctx->B_i);
 118                 AES_encrypt(ctx->B_i, ctx->X_i, &ctx->aes_key);
 119                 v += AES_BLOCK_SIZE;
 120                 v_len -= AES_BLOCK_SIZE;
 121                 *remain -= AES_BLOCK_SIZE;
 122         }
 123
 124         if (v_len > 0) {
 125                 ZERO_STRUCT(ctx->B_i);
 126                 memcpy(ctx->B_i, v, v_len);
 127                 ctx->B_i_ofs += v_len;
 128                 *remain -= v_len;
 129                 v = NULL;
 130                 v_len = 0;
 131         }
 132
 133         if (*remain > 0) {
 134                 return;
 135         }
 136
 137         if (ctx->B_i_ofs > 0) {
 138                 aes_block_xor(ctx->X_i, ctx->B_i, ctx->B_i);
 139                 AES_encrypt(ctx->B_i, ctx->X_i, &ctx->aes_key);
 140                 ctx->B_i_ofs = 0;
 141         }
 142 }
 143
 144 static inline void aes_ccm_128_S_i(struct aes_ccm_128_context *ctx,
 145                                    uint8_t S_i[AES_BLOCK_SIZE],
 146                                    size_t i)
 147 {
 148         RSIVAL(ctx->A_i, (AES_BLOCK_SIZE - AES_CCM_128_L), i);
 149         AES_encrypt(ctx->A_i, S_i, &ctx->aes_key);
 150 }
 151
 152 void aes_ccm_128_crypt(struct aes_ccm_128_context *ctx,
 153                        uint8_t *m, size_t m_len)
 154 {
 155         while (m_len > 0) {
 156                 if (ctx->S_i_ofs == AES_BLOCK_SIZE) {
 157                         ctx->S_i_ctr += 1;
 158                         aes_ccm_128_S_i(ctx, ctx->S_i, ctx->S_i_ctr);
 159                         ctx->S_i_ofs = 0;
 160                 }
 161
 162                 if (likely(ctx->S_i_ofs == 0 && m_len >= AES_BLOCK_SIZE)) {
 163                         aes_block_xor(m, ctx->S_i, m);
 164                         m += AES_BLOCK_SIZE;
 165                         m_len -= AES_BLOCK_SIZE;
 166                         ctx->S_i_ctr += 1;
 167                         aes_ccm_128_S_i(ctx, ctx->S_i, ctx->S_i_ctr);
 168                         continue;
 169                 }
 170
 171                 m[0] ^= ctx->S_i[ctx->S_i_ofs];
 172                 m += 1;
 173                 m_len -= 1;
 174                 ctx->S_i_ofs += 1;
 175         }
 176 }
 177
 178 void aes_ccm_128_digest(struct aes_ccm_128_context *ctx,
 179                         uint8_t digest[AES_BLOCK_SIZE])
 180 {
 181         if (unlikely(ctx->a_remain != 0)) {
 182                 abort();
 183         }
 184         if (unlikely(ctx->m_remain != 0)) {
 185                 abort();
 186         }
 187
 188         /* prepare S_0 */
 189         aes_ccm_128_S_i(ctx, ctx->S_i, 0);
 190
 191         /*
 192          * note X_i is T here
 193          */
 194         aes_block_xor(ctx->X_i, ctx->S_i, digest);
 195
 196         ZERO_STRUCTP(ctx);
 197 }