crypto/cmac/cmac.c

   1 /*
   2  * Copyright 2010-2021 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 struct CMAC_CTX_st {
  24     /* Cipher context to use */
  25     EVP_CIPHER_CTX *cctx;
  26     /* Keys k1 and k2 */
  27     unsigned char k1[EVP_MAX_BLOCK_LENGTH];
  28     unsigned char k2[EVP_MAX_BLOCK_LENGTH];
  29     /* Temporary block */
  30     unsigned char tbl[EVP_MAX_BLOCK_LENGTH];
  31     /* Last (possibly partial) block */
  32     unsigned char last_block[EVP_MAX_BLOCK_LENGTH];
  33     /* Number of bytes in last block: -1 means context not initialised */
  34     int nlast_block;
  35 };
  36
  37 /* Make temporary keys K1 and K2 */
  38
  39 static void make_kn(unsigned char *k1, const unsigned char *l, int bl)
  40 {
  41     int i;
  42     unsigned char c = l[0], carry = c >> 7, cnext;
  43
  44     /* Shift block to left, including carry */
  45     for (i = 0; i < bl - 1; i++, c = cnext)
  46         k1[i] = (c << 1) | ((cnext = l[i + 1]) >> 7);
  47
  48     /* If MSB set fixup with R */
  49     k1[i] = (c << 1) ^ ((0 - carry) & (bl == 16 ? 0x87 : 0x1b));
  50 }
  51
  52 CMAC_CTX *CMAC_CTX_new(void)
  53 {
  54     CMAC_CTX *ctx;
  55
  56     if ((ctx = OPENSSL_malloc(sizeof(*ctx))) == NULL)
  57         return NULL;
  58     ctx->cctx = EVP_CIPHER_CTX_new();
  59     if (ctx->cctx == NULL) {
  60         OPENSSL_free(ctx);
  61         return NULL;
  62     }
  63     ctx->nlast_block = -1;
  64     return ctx;
  65 }
  66
  67 void CMAC_CTX_cleanup(CMAC_CTX *ctx)
  68 {
  69     EVP_CIPHER_CTX_reset(ctx->cctx);
  70     OPENSSL_cleanse(ctx->tbl, EVP_MAX_BLOCK_LENGTH);
  71     OPENSSL_cleanse(ctx->k1, EVP_MAX_BLOCK_LENGTH);
  72     OPENSSL_cleanse(ctx->k2, EVP_MAX_BLOCK_LENGTH);
  73     OPENSSL_cleanse(ctx->last_block, EVP_MAX_BLOCK_LENGTH);
  74     ctx->nlast_block = -1;
  75 }
  76
  77 EVP_CIPHER_CTX *CMAC_CTX_get0_cipher_ctx(CMAC_CTX *ctx)
  78 {
  79     return ctx->cctx;
  80 }
  81
  82 void CMAC_CTX_free(CMAC_CTX *ctx)
  83 {
  84     if (!ctx)
  85         return;
  86     CMAC_CTX_cleanup(ctx);
  87     EVP_CIPHER_CTX_free(ctx->cctx);
  88     OPENSSL_free(ctx);
  89 }
  90
  91 int CMAC_CTX_copy(CMAC_CTX *out, const CMAC_CTX *in)
  92 {
  93     int bl;
  94
  95     if (in->nlast_block == -1)
  96         return 0;
  97     if ((bl = EVP_CIPHER_CTX_get_block_size(in->cctx)) < 0)
  98         return 0;
  99     if (!EVP_CIPHER_CTX_copy(out->cctx, in->cctx))
 100         return 0;
 101     memcpy(out->k1, in->k1, bl);
 102     memcpy(out->k2, in->k2, bl);
 103     memcpy(out->tbl, in->tbl, bl);
 104     memcpy(out->last_block, in->last_block, bl);
 105     out->nlast_block = in->nlast_block;
 106     return 1;
 107 }
 108
 109 int CMAC_Init(CMAC_CTX *ctx, const void *key, size_t keylen,
 110               const EVP_CIPHER *cipher, ENGINE *impl)
 111 {
 112     static const unsigned char zero_iv[EVP_MAX_BLOCK_LENGTH] = { 0 };
 113
 114     /* All zeros means restart */
 115     if (!key && !cipher && !impl && keylen == 0) {
 116         /* Not initialised */
 117         if (ctx->nlast_block == -1)
 118             return 0;
 119         if (!EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, NULL, zero_iv))
 120             return 0;
 121         memset(ctx->tbl, 0, EVP_CIPHER_CTX_get_block_size(ctx->cctx));
 122         ctx->nlast_block = 0;
 123         return 1;
 124     }
 125     /* Initialise context */
 126     if (cipher != NULL) {
 127         /* Ensure we can't use this ctx until we also have a key */
 128         ctx->nlast_block = -1;
 129         if (!EVP_EncryptInit_ex(ctx->cctx, cipher, impl, NULL, NULL))
 130             return 0;
 131     }
 132     /* Non-NULL key means initialisation complete */
 133     if (key != NULL) {
 134         int bl;
 135
 136         /* If anything fails then ensure we can't use this ctx */
 137         ctx->nlast_block = -1;
 138         if (EVP_CIPHER_CTX_get0_cipher(ctx->cctx) == NULL)
 139             return 0;
 140         if (EVP_CIPHER_CTX_set_key_length(ctx->cctx, keylen) <= 0)
 141             return 0;
 142         if (!EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, key, zero_iv))
 143             return 0;
 144         if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) < 0)
 145             return 0;
 146         if (EVP_Cipher(ctx->cctx, ctx->tbl, zero_iv, bl) <= 0)
 147             return 0;
 148         make_kn(ctx->k1, ctx->tbl, bl);
 149         make_kn(ctx->k2, ctx->k1, bl);
 150         OPENSSL_cleanse(ctx->tbl, bl);
 151         /* Reset context again ready for first data block */
 152         if (!EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, NULL, zero_iv))
 153             return 0;
 154         /* Zero tbl so resume works */
 155         memset(ctx->tbl, 0, bl);
 156         ctx->nlast_block = 0;
 157     }
 158     return 1;
 159 }
 160
 161 int CMAC_Update(CMAC_CTX *ctx, const void *in, size_t dlen)
 162 {
 163     const unsigned char *data = in;
 164     int bl;
 165
 166     if (ctx->nlast_block == -1)
 167         return 0;
 168     if (dlen == 0)
 169         return 1;
 170     if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) < 0)
 171         return 0;
 172     /* Copy into partial block if we need to */
 173     if (ctx->nlast_block > 0) {
 174         size_t nleft;
 175
 176         nleft = bl - ctx->nlast_block;
 177         if (dlen < nleft)
 178             nleft = dlen;
 179         memcpy(ctx->last_block + ctx->nlast_block, data, nleft);
 180         dlen -= nleft;
 181         ctx->nlast_block += nleft;
 182         /* If no more to process return */
 183         if (dlen == 0)
 184             return 1;
 185         data += nleft;
 186         /* Else not final block so encrypt it */
 187         if (EVP_Cipher(ctx->cctx, ctx->tbl, ctx->last_block, bl) <= 0)
 188             return 0;
 189     }
 190     /* Encrypt all but one of the complete blocks left */
 191     while (dlen > (size_t)bl) {
 192         if (EVP_Cipher(ctx->cctx, ctx->tbl, data, bl) <= 0)
 193             return 0;
 194         dlen -= bl;
 195         data += bl;
 196     }
 197     /* Copy any data left to last block buffer */
 198     memcpy(ctx->last_block, data, dlen);
 199     ctx->nlast_block = dlen;
 200     return 1;
 201
 202 }
 203
 204 int CMAC_Final(CMAC_CTX *ctx, unsigned char *out, size_t *poutlen)
 205 {
 206     int i, bl, lb;
 207
 208     if (ctx->nlast_block == -1)
 209         return 0;
 210     if ((bl = EVP_CIPHER_CTX_get_block_size(ctx->cctx)) < 0)
 211         return 0;
 212     if (poutlen != NULL)
 213         *poutlen = (size_t)bl;
 214     if (!out)
 215         return 1;
 216     lb = ctx->nlast_block;
 217     /* Is last block complete? */
 218     if (lb == bl) {
 219         for (i = 0; i < bl; i++)
 220             out[i] = ctx->last_block[i] ^ ctx->k1[i];
 221     } else {
 222         ctx->last_block[lb] = 0x80;
 223         if (bl - lb > 1)
 224             memset(ctx->last_block + lb + 1, 0, bl - lb - 1);
 225         for (i = 0; i < bl; i++)
 226             out[i] = ctx->last_block[i] ^ ctx->k2[i];
 227     }
 228     if (EVP_Cipher(ctx->cctx, out, out, bl) <= 0) {
 229         OPENSSL_cleanse(out, bl);
 230         return 0;
 231     }
 232     return 1;
 233 }
 234
 235 int CMAC_resume(CMAC_CTX *ctx)
 236 {
 237     if (ctx->nlast_block == -1)
 238         return 0;
 239     /*
 240      * The buffer "tbl" contains the last fully encrypted block which is the
 241      * last IV (or all zeroes if no last encrypted block). The last block has
 242      * not been modified since CMAC_final(). So reinitialising using the last
 243      * decrypted block will allow CMAC to continue after calling
 244      * CMAC_Final().
 245      */
 246     return EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, NULL, ctx->tbl);
 247 }