/* $OpenBSD: cmac.c,v 1.11 2021/12/12 21:30:13 tb Exp $ */
/* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
 * project.
 */
/* ====================================================================
 * Copyright (c) 2010 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
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 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    licensing@OpenSSL.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
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 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
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 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <openssl/cmac.h>

#include "evp_locl.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, unsigned char *l, int bl)
{
        int i;

        /* Shift block to left, including carry */
        for (i = 0; i < bl; i++) {
                k1[i] = l[i] << 1;
                if (i < bl - 1 && l[i + 1] & 0x80)
                        k1[i] |= 1;
        }
        /* If MSB set fixup with R */
        if (l[0] & 0x80)
                k1[bl - 1] ^= bl == 16 ? 0x87 : 0x1b;
}

CMAC_CTX *
CMAC_CTX_new(void)
{
        CMAC_CTX *ctx;

        ctx = malloc(sizeof(CMAC_CTX));
        if (!ctx)
                return NULL;
        EVP_CIPHER_CTX_init(&ctx->cctx);
        ctx->nlast_block = -1;
        return ctx;
}

void
CMAC_CTX_cleanup(CMAC_CTX *ctx)
{
        EVP_CIPHER_CTX_cleanup(&ctx->cctx);
        explicit_bzero(ctx->tbl, EVP_MAX_BLOCK_LENGTH);
        explicit_bzero(ctx->k1, EVP_MAX_BLOCK_LENGTH);
        explicit_bzero(ctx->k2, EVP_MAX_BLOCK_LENGTH);
        explicit_bzero(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 == NULL)
                return;

        CMAC_CTX_cleanup(ctx);
        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 unsigned char zero_iv[EVP_MAX_BLOCK_LENGTH];

        /* 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;
        }
        /* Initialiase context */
        if (cipher && !EVP_EncryptInit_ex(&ctx->cctx, cipher, impl, NULL, NULL))
                return 0;
        /* Non-NULL key means initialisation complete */
        if (key) {
                int bl;

                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))
                        return 0;
                make_kn(ctx->k1, ctx->tbl, bl);
                make_kn(ctx->k2, ctx->k1, bl);
                explicit_bzero(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))
                        return 0;
        }
        /* Encrypt all but one of the complete blocks left */
        while (dlen > bl) {
                if (!EVP_Cipher(&ctx->cctx, ctx->tbl, data, bl))
                        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)) {
                explicit_bzero(out, bl);
                return 0;
        }
        return 1;
}

int
CMAC_resume(CMAC_CTX *ctx)
{
        if (ctx->nlast_block == -1)
                return 0;
        /* The buffer "tbl" containes 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);
}