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/*
* Copyright 2010-2020 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "internal/cryptlib.h"
#include <openssl/cmac.h>
#include <openssl/err.h>
struct CMAC_CTX_st {
/* Cipher context to use */
EVP_CIPHER_CTX *cctx;
/* Keys k1 and k2 */
unsigned char k1[EVP_MAX_BLOCK_LENGTH];
unsigned char k2[EVP_MAX_BLOCK_LENGTH];
/* Temporary block */
unsigned char tbl[EVP_MAX_BLOCK_LENGTH];
/* Last (possibly partial) block */
unsigned char last_block[EVP_MAX_BLOCK_LENGTH];
/* Number of bytes in last block: -1 means context not initialised */
int nlast_block;
};
/* Make temporary keys K1 and K2 */
static void make_kn(unsigned char *k1, const unsigned char *l, int bl)
{
int i;
unsigned char c = l[0], carry = c >> 7, cnext;
/* Shift block to left, including carry */
for (i = 0; i < bl - 1; i++, c = cnext)
k1[i] = (c << 1) | ((cnext = l[i + 1]) >> 7);
/* If MSB set fixup with R */
k1[i] = (c << 1) ^ ((0 - carry) & (bl == 16 ? 0x87 : 0x1b));
}
CMAC_CTX *CMAC_CTX_new(void)
{
CMAC_CTX *ctx;
if ((ctx = OPENSSL_malloc(sizeof(*ctx))) == NULL) {
CRYPTOerr(CRYPTO_F_CMAC_CTX_NEW, ERR_R_MALLOC_FAILURE);
return NULL;
}
ctx->cctx = EVP_CIPHER_CTX_new();
if (ctx->cctx == NULL) {
OPENSSL_free(ctx);
return NULL;
}
ctx->nlast_block = -1;
return ctx;
}
void CMAC_CTX_cleanup(CMAC_CTX *ctx)
{
EVP_CIPHER_CTX_reset(ctx->cctx);
OPENSSL_cleanse(ctx->tbl, EVP_MAX_BLOCK_LENGTH);
OPENSSL_cleanse(ctx->k1, EVP_MAX_BLOCK_LENGTH);
OPENSSL_cleanse(ctx->k2, EVP_MAX_BLOCK_LENGTH);
OPENSSL_cleanse(ctx->last_block, EVP_MAX_BLOCK_LENGTH);
ctx->nlast_block = -1;
}
EVP_CIPHER_CTX *CMAC_CTX_get0_cipher_ctx(CMAC_CTX *ctx)
{
return ctx->cctx;
}
void CMAC_CTX_free(CMAC_CTX *ctx)
{
if (!ctx)
return;
CMAC_CTX_cleanup(ctx);
EVP_CIPHER_CTX_free(ctx->cctx);
OPENSSL_free(ctx);
}
int CMAC_CTX_copy(CMAC_CTX *out, const CMAC_CTX *in)
{
int bl;
if (in->nlast_block == -1)
return 0;
if (!EVP_CIPHER_CTX_copy(out->cctx, in->cctx))
return 0;
bl = EVP_CIPHER_CTX_block_size(in->cctx);
memcpy(out->k1, in->k1, bl);
memcpy(out->k2, in->k2, bl);
memcpy(out->tbl, in->tbl, bl);
memcpy(out->last_block, in->last_block, bl);
out->nlast_block = in->nlast_block;
return 1;
}
int CMAC_Init(CMAC_CTX *ctx, const void *key, size_t keylen,
const EVP_CIPHER *cipher, ENGINE *impl)
{
static const unsigned char zero_iv[EVP_MAX_BLOCK_LENGTH] = { 0 };
/* All zeros means restart */
if (!key && !cipher && !impl && keylen == 0) {
/* Not initialised */
if (ctx->nlast_block == -1)
return 0;
if (!EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, NULL, zero_iv))
return 0;
memset(ctx->tbl, 0, EVP_CIPHER_CTX_block_size(ctx->cctx));
ctx->nlast_block = 0;
return 1;
}
/* Initialise context */
if (cipher != NULL) {
/* Ensure we can't use this ctx until we also have a key */
ctx->nlast_block = -1;
if (!EVP_EncryptInit_ex(ctx->cctx, cipher, impl, NULL, NULL))
return 0;
}
/* Non-NULL key means initialisation complete */
if (key != NULL) {
int bl;
/* If anything fails then ensure we can't use this ctx */
ctx->nlast_block = -1;
if (!EVP_CIPHER_CTX_cipher(ctx->cctx))
return 0;
if (!EVP_CIPHER_CTX_set_key_length(ctx->cctx, keylen))
return 0;
if (!EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, key, zero_iv))
return 0;
bl = EVP_CIPHER_CTX_block_size(ctx->cctx);
if (EVP_Cipher(ctx->cctx, ctx->tbl, zero_iv, bl) <= 0)
return 0;
make_kn(ctx->k1, ctx->tbl, bl);
make_kn(ctx->k2, ctx->k1, bl);
OPENSSL_cleanse(ctx->tbl, bl);
/* Reset context again ready for first data block */
if (!EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, NULL, zero_iv))
return 0;
/* Zero tbl so resume works */
memset(ctx->tbl, 0, bl);
ctx->nlast_block = 0;
}
return 1;
}
int CMAC_Update(CMAC_CTX *ctx, const void *in, size_t dlen)
{
const unsigned char *data = in;
size_t bl;
if (ctx->nlast_block == -1)
return 0;
if (dlen == 0)
return 1;
bl = EVP_CIPHER_CTX_block_size(ctx->cctx);
/* Copy into partial block if we need to */
if (ctx->nlast_block > 0) {
size_t nleft;
nleft = bl - ctx->nlast_block;
if (dlen < nleft)
nleft = dlen;
memcpy(ctx->last_block + ctx->nlast_block, data, nleft);
dlen -= nleft;
ctx->nlast_block += nleft;
/* If no more to process return */
if (dlen == 0)
return 1;
data += nleft;
/* Else not final block so encrypt it */
if (EVP_Cipher(ctx->cctx, ctx->tbl, ctx->last_block, bl) <= 0)
return 0;
}
/* Encrypt all but one of the complete blocks left */
while (dlen > bl) {
if (EVP_Cipher(ctx->cctx, ctx->tbl, data, bl) <= 0)
return 0;
dlen -= bl;
data += bl;
}
/* Copy any data left to last block buffer */
memcpy(ctx->last_block, data, dlen);
ctx->nlast_block = dlen;
return 1;
}
int CMAC_Final(CMAC_CTX *ctx, unsigned char *out, size_t *poutlen)
{
int i, bl, lb;
if (ctx->nlast_block == -1)
return 0;
bl = EVP_CIPHER_CTX_block_size(ctx->cctx);
*poutlen = (size_t)bl;
if (!out)
return 1;
lb = ctx->nlast_block;
/* Is last block complete? */
if (lb == bl) {
for (i = 0; i < bl; i++)
out[i] = ctx->last_block[i] ^ ctx->k1[i];
} else {
ctx->last_block[lb] = 0x80;
if (bl - lb > 1)
memset(ctx->last_block + lb + 1, 0, bl - lb - 1);
for (i = 0; i < bl; i++)
out[i] = ctx->last_block[i] ^ ctx->k2[i];
}
if (!EVP_Cipher(ctx->cctx, out, out, bl)) {
OPENSSL_cleanse(out, bl);
return 0;
}
return 1;
}
int CMAC_resume(CMAC_CTX *ctx)
{
if (ctx->nlast_block == -1)
return 0;
/*
* The buffer "tbl" contains the last fully encrypted block which is the
* last IV (or all zeroes if no last encrypted block). The last block has
* not been modified since CMAC_final(). So reinitialising using the last
* decrypted block will allow CMAC to continue after calling
* CMAC_Final().
*/
return EVP_EncryptInit_ex(ctx->cctx, NULL, NULL, NULL, ctx->tbl);
}
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