crypto/cmac/cmac.c

   1 /*
   2  * Copyright 2010-2024 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 /*
  11  * CMAC low level APIs are deprecated for public use, but still ok for internal
  12  * use.
  13  */
  14 #include "internal/deprecated.h"
  15
  16 #include <stdio.h>
  17 #include <stdlib.h>
  18 #include <string.h>
  19 #include "internal/cryptlib.h"
  20 #include <openssl/cmac.h>
  21 #include <openssl/err.h>
  22
  23 #define LOCAL_BUF_SIZE 2048
  24 struct CMAC_CTX_st {
  25     /* Cipher context to use */
  26     EVP_CIPHER_CTX *cctx;
  27     /* Keys k1 and k2 */
  28     unsigned char k1[EVP_MAX_BLOCK_LENGTH];
  29     unsigned char k2[EVP_MAX_BLOCK_LENGTH];
  30     /* Temporary block */
  31     unsigned char tbl[EVP_MAX_BLOCK_LENGTH];
  32     /* Last (possibly partial) block */
  33     unsigned char last_block[EVP_MAX_BLOCK_LENGTH];
  34     /* Number of bytes in last block: -1 means context not initialised */
  35     int nlast_block;
  36 };
  37
  38 /* Make temporary keys K1 and K2 */
  39
  40 static void make_kn(unsigned char *k1, const unsigned char *l, int bl)
  41 {
  42     int i;
  43     unsigned char c = l[0], carry = c >> 7, cnext;
  44
  45     /* Shift block to left, including carry */
  46     for (i = 0; i < bl - 1; i++, c = cnext)
  47         k1[i] = (c << 1) | ((cnext = l[i + 1]) >> 7);
  48
  49     /* If MSB set fixup with R */
  50     k1[i] = (c << 1) ^ ((0 - carry) & (bl == 16 ? 0x87 : 0x1b));
  51 }
  52
  53 CMAC_CTX *CMAC_CTX_new(void)
  54 {
  55     CMAC_CTX *ctx;
  56
  57     if ((ctx = OPENSSL_malloc(sizeof(*ctx))) == NULL)
  58         return NULL;
  59     ctx->cctx = EVP_CIPHER_CTX_new();
  60     if (ctx->cctx == NULL) {
  61         OPENSSL_free(ctx);
  62         return NULL;
  63     }
  64     ctx->nlast_block = -1;
  65     return ctx;
  66 }
  67
  68 void CMAC_CTX_cleanup(CMAC_CTX *ctx)
  69 {
  70     EVP_CIPHER_CTX_reset(ctx->cctx);
  71     OPENSSL_cleanse(ctx->tbl, EVP_MAX_BLOCK_LENGTH);
  72     OPENSSL_cleanse(ctx->k1, EVP_MAX_BLOCK_LENGTH);
  73     OPENSSL_cleanse(ctx->k2, EVP_MAX_BLOCK_LENGTH);
  74     OPENSSL_cleanse(ctx->last_block, EVP_MAX_BLOCK_LENGTH);
  75     ctx->nlast_block = -1;
  76 }
  77
  78 EVP_CIPHER_CTX *CMAC_CTX_get0_cipher_ctx(CMAC_CTX *ctx)
  79 {
  80     return ctx->cctx;
  81 }
  82
  83 void CMAC_CTX_free(CMAC_CTX *ctx)
  84 {
  85     if (!ctx)
  86         return;
  87     CMAC_CTX_cleanup(ctx);
  88     EVP_CIPHER_CTX_free(ctx->cctx);
  89     OPENSSL_free(ctx);
  90 }
  91
  92 int CMAC_CTX_copy(CMAC_CTX *out, const CMAC_CTX *in)
  93 {
  94     int bl;
  95
  96     if (in->nlast_block == -1)
  97         return 0;
  98     if ((bl = EVP_CIPHER_CTX_get_block_size(in->cctx)) == 0)
  99         return 0;
 100     if (!EVP_CIPHER_CTX_copy(out->cctx, in->cctx))
 101         return 0;
 102     memcpy(out->k1, in->k1, bl);
 103     memcpy(out->k2, in->k2, bl);
 104     memcpy(out->tbl, in->tbl, bl);
 105     memcpy(out->last_block, in->last_block, bl);
 106     out->nlast_block = in->nlast_block;
 107     return 1;
 108 }
 109
 110 int CMAC_Init(CMAC_CTX *ctx, const void *key, size_t keylen,
 111               const EVP_CIPHER *cipher, ENGINE *impl)
 112 {
 113     static const unsigned char zero_iv[EVP_MAX_BLOCK_LENGTH] = { 0 };
 114     int block_len;
 115
 116     /* All zeros means restart */
 117     if (!key && !cipher && !impl && keylen == 0) {
 118         /* Not initialised */
 119         if (ctx->nlast_block == -1)
 120             return 0;
 121         if (!EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, NULL, zero_iv))
 122             return 0;
 123         block_len = EVP_CIPHER_CTX_get_block_size(ctx->cctx);
 124         if (block_len == 0)
 125             return 0;
 126         memset(ctx->tbl, 0, block_len);
 127         ctx->nlast_block = 0;
 128         return 1;
 129     }
 130     /* Initialise context */
 131     if (cipher != NULL) {
 132         /* Ensure we can't use this ctx until we also have a key */
 133         ctx->nlast_block = -1;
 134         if (!EVP_EncryptInit_ex(ctx->cctx, cipher, impl, NULL, NULL))
 135             return 0;
 136     }
 137     /* Non-NULL key means initialisation complete */
 138     if (key != NULL) {
 139         int bl;
 140
 141         /* If anything fails then ensure we can't use this ctx */
 142         ctx->nlast_block = -1;
 143         if (EVP_CIPHER_CTX_get0_cipher(ctx->cctx) == NULL)
 144             return 0;
 145         if (EVP_CIPHER_CTX_set_key_length(ctx->cctx, keylen) <= 0)
 146             return 0;
 147         if (!EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, key, zero_iv))
 148             return 0;
 149         if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) < 0)
 150             return 0;
 151         if (EVP_Cipher(ctx->cctx, ctx->tbl, zero_iv, bl) <= 0)
 152             return 0;
 153         make_kn(ctx->k1, ctx->tbl, bl);
 154         make_kn(ctx->k2, ctx->k1, bl);
 155         OPENSSL_cleanse(ctx->tbl, bl);
 156         /* Reset context again ready for first data block */
 157         if (!EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, NULL, zero_iv))
 158             return 0;
 159         /* Zero tbl so resume works */
 160         memset(ctx->tbl, 0, bl);
 161         ctx->nlast_block = 0;
 162     }
 163     return 1;
 164 }
 165
 166 int CMAC_Update(CMAC_CTX *ctx, const void *in, size_t dlen)
 167 {
 168     const unsigned char *data = in;
 169     int bl;
 170     size_t max_burst_blocks, cipher_blocks;
 171     unsigned char buf[LOCAL_BUF_SIZE];
 172
 173     if (ctx->nlast_block == -1)
 174         return 0;
 175     if (dlen == 0)
 176         return 1;
 177     if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) == 0)
 178         return 0;
 179     /* Copy into partial block if we need to */
 180     if (ctx->nlast_block > 0) {
 181         size_t nleft;
 182
 183         nleft = bl - ctx->nlast_block;
 184         if (dlen < nleft)
 185             nleft = dlen;
 186         memcpy(ctx->last_block + ctx->nlast_block, data, nleft);
 187         dlen -= nleft;
 188         ctx->nlast_block += nleft;
 189         /* If no more to process return */
 190         if (dlen == 0)
 191             return 1;
 192         data += nleft;
 193         /* Else not final block so encrypt it */
 194         if (EVP_Cipher(ctx->cctx, ctx->tbl, ctx->last_block, bl) <= 0)
 195             return 0;
 196     }
 197     /* Encrypt all but one of the complete blocks left */
 198
 199     max_burst_blocks = LOCAL_BUF_SIZE / bl;
 200     cipher_blocks = (dlen - 1) / bl;
 201     if (max_burst_blocks == 0) {
 202         /*
 203          * When block length is greater than local buffer size,
 204          * use ctx->tbl as cipher output.
 205          */
 206         while (dlen > (size_t)bl) {
 207             if (EVP_Cipher(ctx->cctx, ctx->tbl, data, bl) <= 0)
 208                 return 0;
 209             dlen -= bl;
 210             data += bl;
 211         }
 212     } else {
 213         while (cipher_blocks > max_burst_blocks) {
 214             if (EVP_Cipher(ctx->cctx, buf, data, max_burst_blocks * bl) <= 0)
 215                 return 0;
 216             dlen -= max_burst_blocks * bl;
 217             data += max_burst_blocks * bl;
 218             cipher_blocks -= max_burst_blocks;
 219         }
 220         if (cipher_blocks > 0) {
 221             if (EVP_Cipher(ctx->cctx, buf, data, cipher_blocks * bl) <= 0)
 222                 return 0;
 223             dlen -= cipher_blocks * bl;
 224             data += cipher_blocks * bl;
 225             memcpy(ctx->tbl, &buf[(cipher_blocks - 1) * bl], bl);
 226         }
 227     }
 228     /* Copy any data left to last block buffer */
 229     memcpy(ctx->last_block, data, dlen);
 230     ctx->nlast_block = dlen;
 231     return 1;
 232
 233 }
 234
 235 int CMAC_Final(CMAC_CTX *ctx, unsigned char *out, size_t *poutlen)
 236 {
 237     int i, bl, lb;
 238
 239     if (ctx->nlast_block == -1)
 240         return 0;
 241     if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) == 0)
 242         return 0;
 243     if (poutlen != NULL)
 244         *poutlen = (size_t)bl;
 245     if (!out)
 246         return 1;
 247     lb = ctx->nlast_block;
 248     /* Is last block complete? */
 249     if (lb == bl) {
 250         for (i = 0; i < bl; i++)
 251             out[i] = ctx->last_block[i] ^ ctx->k1[i];
 252     } else {
 253         ctx->last_block[lb] = 0x80;
 254         if (bl - lb > 1)
 255             memset(ctx->last_block + lb + 1, 0, bl - lb - 1);
 256         for (i = 0; i < bl; i++)
 257             out[i] = ctx->last_block[i] ^ ctx->k2[i];
 258     }
 259     if (EVP_Cipher(ctx->cctx, out, out, bl) <= 0) {
 260         OPENSSL_cleanse(out, bl);
 261         return 0;
 262     }
 263     return 1;
 264 }
 265
 266 int CMAC_resume(CMAC_CTX *ctx)
 267 {
 268     if (ctx->nlast_block == -1)
 269         return 0;
 270     /*
 271      * The buffer "tbl" contains the last fully encrypted block which is the
 272      * last IV (or all zeroes if no last encrypted block). The last block has
 273      * not been modified since CMAC_final(). So reinitialising using the last
 274      * decrypted block will allow CMAC to continue after calling
 275      * CMAC_Final().
 276      */
 277     return EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, NULL, ctx->tbl);
 278 }