121 lines
2.8 KiB
C
121 lines
2.8 KiB
C
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/* $OpenBSD: cmac.c,v 1.3 2017/05/02 17:07:06 mikeb Exp $ */
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/*-
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* Copyright (c) 2008 Damien Bergamini <damien.bergamini@free.fr>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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/*
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* This code implements the CMAC (Cipher-based Message Authentication)
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* algorithm described in FIPS SP800-38B using the AES-128 cipher.
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <crypto/aes.h>
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#include <crypto/cmac.h>
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#define LSHIFT(v, r) do { \
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int i; \
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for (i = 0; i < 15; i++) \
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(r)[i] = (v)[i] << 1 | (v)[i + 1] >> 7; \
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(r)[15] = (v)[15] << 1; \
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} while (0)
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#define XOR(v, r) do { \
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int i; \
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for (i = 0; i < 16; i++) \
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(r)[i] ^= (v)[i]; \
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} while (0)
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void
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AES_CMAC_Init(AES_CMAC_CTX *ctx)
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{
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memset(ctx->X, 0, sizeof ctx->X);
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ctx->M_n = 0;
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}
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void
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AES_CMAC_SetKey(AES_CMAC_CTX *ctx, const u_int8_t key[AES_CMAC_KEY_LENGTH])
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{
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AES_Setkey(&ctx->aesctx, key, 16);
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}
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void
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AES_CMAC_Update(AES_CMAC_CTX *ctx, const u_int8_t *data, u_int len)
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{
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u_int mlen;
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if (ctx->M_n > 0) {
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mlen = MIN(16 - ctx->M_n, len);
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memcpy(ctx->M_last + ctx->M_n, data, mlen);
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ctx->M_n += mlen;
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if (ctx->M_n < 16 || len == mlen)
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return;
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XOR(ctx->M_last, ctx->X);
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AES_Encrypt(&ctx->aesctx, ctx->X, ctx->X);
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data += mlen;
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len -= mlen;
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}
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while (len > 16) { /* not last block */
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XOR(data, ctx->X);
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AES_Encrypt(&ctx->aesctx, ctx->X, ctx->X);
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data += 16;
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len -= 16;
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}
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/* potential last block, save it */
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memcpy(ctx->M_last, data, len);
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ctx->M_n = len;
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}
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void
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AES_CMAC_Final(u_int8_t digest[AES_CMAC_DIGEST_LENGTH], AES_CMAC_CTX *ctx)
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{
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u_int8_t K[16];
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/* generate subkey K1 */
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memset(K, 0, sizeof K);
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AES_Encrypt(&ctx->aesctx, K, K);
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if (K[0] & 0x80) {
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LSHIFT(K, K);
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K[15] ^= 0x87;
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} else
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LSHIFT(K, K);
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if (ctx->M_n == 16) {
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/* last block was a complete block */
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XOR(K, ctx->M_last);
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} else {
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/* generate subkey K2 */
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if (K[0] & 0x80) {
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LSHIFT(K, K);
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K[15] ^= 0x87;
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} else
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LSHIFT(K, K);
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/* padding(M_last) */
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ctx->M_last[ctx->M_n] = 0x80;
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while (++ctx->M_n < 16)
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ctx->M_last[ctx->M_n] = 0;
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XOR(K, ctx->M_last);
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}
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XOR(ctx->M_last, ctx->X);
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AES_Encrypt(&ctx->aesctx, ctx->X, digest);
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explicit_bzero(K, sizeof K);
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}
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