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![Ard Biesheuvel](/assets/img/avatar_default.png)
Instead of unconditionally forcing 4 byte alignment for all generic chaining modes that rely on crypto_xor() or crypto_inc() (which may result in unnecessary copying of data when the underlying hardware can perform unaligned accesses efficiently), make those functions deal with unaligned input explicitly, but only if the Kconfig symbol HAVE_EFFICIENT_UNALIGNED_ACCESS is set. This will allow us to drop the alignmasks from the CBC, CMAC, CTR, CTS, PCBC and SEQIV drivers. For crypto_inc(), this simply involves making the 4-byte stride conditional on HAVE_EFFICIENT_UNALIGNED_ACCESS being set, given that it typically operates on 16 byte buffers. For crypto_xor(), an algorithm is implemented that simply runs through the input using the largest strides possible if unaligned accesses are allowed. If they are not, an optimal sequence of memory accesses is emitted that takes the relative alignment of the input buffers into account, e.g., if the relative misalignment of dst and src is 4 bytes, the entire xor operation will be completed using 4 byte loads and stores (modulo unaligned bits at the start and end). Note that all expressions involving misalign are simply eliminated by the compiler when HAVE_EFFICIENT_UNALIGNED_ACCESS is defined. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
321 lines
7.7 KiB
C
321 lines
7.7 KiB
C
/*
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* CMAC: Cipher Block Mode for Authentication
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*
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* Copyright © 2013 Jussi Kivilinna <jussi.kivilinna@iki.fi>
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*
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* Based on work by:
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* Copyright © 2013 Tom St Denis <tstdenis@elliptictech.com>
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* Based on crypto/xcbc.c:
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* Copyright © 2006 USAGI/WIDE Project,
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* Author: Kazunori Miyazawa <miyazawa@linux-ipv6.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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*/
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#include <crypto/internal/hash.h>
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#include <linux/err.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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/*
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* +------------------------
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* | <parent tfm>
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* +------------------------
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* | cmac_tfm_ctx
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* +------------------------
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* | consts (block size * 2)
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* +------------------------
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*/
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struct cmac_tfm_ctx {
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struct crypto_cipher *child;
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u8 ctx[];
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};
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/*
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* +------------------------
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* | <shash desc>
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* +------------------------
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* | cmac_desc_ctx
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* +------------------------
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* | odds (block size)
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* +------------------------
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* | prev (block size)
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* +------------------------
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*/
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struct cmac_desc_ctx {
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unsigned int len;
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u8 ctx[];
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};
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static int crypto_cmac_digest_setkey(struct crypto_shash *parent,
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const u8 *inkey, unsigned int keylen)
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{
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unsigned long alignmask = crypto_shash_alignmask(parent);
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struct cmac_tfm_ctx *ctx = crypto_shash_ctx(parent);
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unsigned int bs = crypto_shash_blocksize(parent);
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__be64 *consts = PTR_ALIGN((void *)ctx->ctx,
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(alignmask | (__alignof__(__be64) - 1)) + 1);
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u64 _const[2];
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int i, err = 0;
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u8 msb_mask, gfmask;
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err = crypto_cipher_setkey(ctx->child, inkey, keylen);
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if (err)
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return err;
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/* encrypt the zero block */
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memset(consts, 0, bs);
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crypto_cipher_encrypt_one(ctx->child, (u8 *)consts, (u8 *)consts);
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switch (bs) {
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case 16:
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gfmask = 0x87;
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_const[0] = be64_to_cpu(consts[1]);
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_const[1] = be64_to_cpu(consts[0]);
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/* gf(2^128) multiply zero-ciphertext with u and u^2 */
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for (i = 0; i < 4; i += 2) {
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msb_mask = ((s64)_const[1] >> 63) & gfmask;
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_const[1] = (_const[1] << 1) | (_const[0] >> 63);
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_const[0] = (_const[0] << 1) ^ msb_mask;
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consts[i + 0] = cpu_to_be64(_const[1]);
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consts[i + 1] = cpu_to_be64(_const[0]);
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}
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break;
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case 8:
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gfmask = 0x1B;
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_const[0] = be64_to_cpu(consts[0]);
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/* gf(2^64) multiply zero-ciphertext with u and u^2 */
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for (i = 0; i < 2; i++) {
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msb_mask = ((s64)_const[0] >> 63) & gfmask;
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_const[0] = (_const[0] << 1) ^ msb_mask;
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consts[i] = cpu_to_be64(_const[0]);
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}
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break;
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}
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return 0;
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}
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static int crypto_cmac_digest_init(struct shash_desc *pdesc)
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{
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unsigned long alignmask = crypto_shash_alignmask(pdesc->tfm);
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struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
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int bs = crypto_shash_blocksize(pdesc->tfm);
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u8 *prev = PTR_ALIGN((void *)ctx->ctx, alignmask + 1) + bs;
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ctx->len = 0;
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memset(prev, 0, bs);
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return 0;
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}
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static int crypto_cmac_digest_update(struct shash_desc *pdesc, const u8 *p,
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unsigned int len)
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{
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struct crypto_shash *parent = pdesc->tfm;
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unsigned long alignmask = crypto_shash_alignmask(parent);
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struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
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struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
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struct crypto_cipher *tfm = tctx->child;
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int bs = crypto_shash_blocksize(parent);
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u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
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u8 *prev = odds + bs;
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/* checking the data can fill the block */
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if ((ctx->len + len) <= bs) {
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memcpy(odds + ctx->len, p, len);
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ctx->len += len;
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return 0;
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}
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/* filling odds with new data and encrypting it */
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memcpy(odds + ctx->len, p, bs - ctx->len);
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len -= bs - ctx->len;
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p += bs - ctx->len;
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crypto_xor(prev, odds, bs);
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crypto_cipher_encrypt_one(tfm, prev, prev);
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/* clearing the length */
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ctx->len = 0;
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/* encrypting the rest of data */
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while (len > bs) {
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crypto_xor(prev, p, bs);
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crypto_cipher_encrypt_one(tfm, prev, prev);
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p += bs;
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len -= bs;
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}
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/* keeping the surplus of blocksize */
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if (len) {
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memcpy(odds, p, len);
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ctx->len = len;
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}
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return 0;
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}
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static int crypto_cmac_digest_final(struct shash_desc *pdesc, u8 *out)
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{
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struct crypto_shash *parent = pdesc->tfm;
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unsigned long alignmask = crypto_shash_alignmask(parent);
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struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
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struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
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struct crypto_cipher *tfm = tctx->child;
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int bs = crypto_shash_blocksize(parent);
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u8 *consts = PTR_ALIGN((void *)tctx->ctx,
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(alignmask | (__alignof__(__be64) - 1)) + 1);
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u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
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u8 *prev = odds + bs;
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unsigned int offset = 0;
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if (ctx->len != bs) {
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unsigned int rlen;
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u8 *p = odds + ctx->len;
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*p = 0x80;
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p++;
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rlen = bs - ctx->len - 1;
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if (rlen)
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memset(p, 0, rlen);
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offset += bs;
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}
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crypto_xor(prev, odds, bs);
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crypto_xor(prev, consts + offset, bs);
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crypto_cipher_encrypt_one(tfm, out, prev);
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return 0;
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}
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static int cmac_init_tfm(struct crypto_tfm *tfm)
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{
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struct crypto_cipher *cipher;
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struct crypto_instance *inst = (void *)tfm->__crt_alg;
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struct crypto_spawn *spawn = crypto_instance_ctx(inst);
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struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
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cipher = crypto_spawn_cipher(spawn);
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if (IS_ERR(cipher))
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return PTR_ERR(cipher);
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ctx->child = cipher;
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return 0;
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};
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static void cmac_exit_tfm(struct crypto_tfm *tfm)
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{
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struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
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crypto_free_cipher(ctx->child);
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}
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static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
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{
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struct shash_instance *inst;
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struct crypto_alg *alg;
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unsigned long alignmask;
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int err;
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err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);
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if (err)
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return err;
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alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
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CRYPTO_ALG_TYPE_MASK);
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if (IS_ERR(alg))
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return PTR_ERR(alg);
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switch (alg->cra_blocksize) {
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case 16:
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case 8:
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break;
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default:
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err = -EINVAL;
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goto out_put_alg;
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}
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inst = shash_alloc_instance("cmac", alg);
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err = PTR_ERR(inst);
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if (IS_ERR(inst))
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goto out_put_alg;
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err = crypto_init_spawn(shash_instance_ctx(inst), alg,
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shash_crypto_instance(inst),
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CRYPTO_ALG_TYPE_MASK);
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if (err)
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goto out_free_inst;
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alignmask = alg->cra_alignmask;
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inst->alg.base.cra_alignmask = alignmask;
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inst->alg.base.cra_priority = alg->cra_priority;
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inst->alg.base.cra_blocksize = alg->cra_blocksize;
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inst->alg.digestsize = alg->cra_blocksize;
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inst->alg.descsize =
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ALIGN(sizeof(struct cmac_desc_ctx), crypto_tfm_ctx_alignment())
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+ (alignmask & ~(crypto_tfm_ctx_alignment() - 1))
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+ alg->cra_blocksize * 2;
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inst->alg.base.cra_ctxsize =
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ALIGN(sizeof(struct cmac_tfm_ctx), crypto_tfm_ctx_alignment())
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+ ((alignmask | (__alignof__(__be64) - 1)) &
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~(crypto_tfm_ctx_alignment() - 1))
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+ alg->cra_blocksize * 2;
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inst->alg.base.cra_init = cmac_init_tfm;
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inst->alg.base.cra_exit = cmac_exit_tfm;
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inst->alg.init = crypto_cmac_digest_init;
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inst->alg.update = crypto_cmac_digest_update;
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inst->alg.final = crypto_cmac_digest_final;
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inst->alg.setkey = crypto_cmac_digest_setkey;
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err = shash_register_instance(tmpl, inst);
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if (err) {
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out_free_inst:
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shash_free_instance(shash_crypto_instance(inst));
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}
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out_put_alg:
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crypto_mod_put(alg);
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return err;
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}
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static struct crypto_template crypto_cmac_tmpl = {
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.name = "cmac",
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.create = cmac_create,
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.free = shash_free_instance,
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.module = THIS_MODULE,
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};
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static int __init crypto_cmac_module_init(void)
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{
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return crypto_register_template(&crypto_cmac_tmpl);
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}
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static void __exit crypto_cmac_module_exit(void)
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{
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crypto_unregister_template(&crypto_cmac_tmpl);
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}
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module_init(crypto_cmac_module_init);
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module_exit(crypto_cmac_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("CMAC keyed hash algorithm");
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MODULE_ALIAS_CRYPTO("cmac");
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