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- // SPDX-License-Identifier: GPL-2.0-or-later
- /*
- * CMAC: Cipher Block Mode for Authentication
- *
- * Copyright © 2013 Jussi Kivilinna <[email protected]>
- *
- * Based on work by:
- * Copyright © 2013 Tom St Denis <[email protected]>
- * Based on crypto/xcbc.c:
- * Copyright © 2006 USAGI/WIDE Project,
- * Author: Kazunori Miyazawa <[email protected]>
- */
- #include <crypto/internal/cipher.h>
- #include <crypto/internal/hash.h>
- #include <linux/err.h>
- #include <linux/kernel.h>
- #include <linux/module.h>
- /*
- * +------------------------
- * | <parent tfm>
- * +------------------------
- * | cmac_tfm_ctx
- * +------------------------
- * | consts (block size * 2)
- * +------------------------
- */
- struct cmac_tfm_ctx {
- struct crypto_cipher *child;
- u8 ctx[];
- };
- /*
- * +------------------------
- * | <shash desc>
- * +------------------------
- * | cmac_desc_ctx
- * +------------------------
- * | odds (block size)
- * +------------------------
- * | prev (block size)
- * +------------------------
- */
- struct cmac_desc_ctx {
- unsigned int len;
- u8 ctx[];
- };
- static int crypto_cmac_digest_setkey(struct crypto_shash *parent,
- const u8 *inkey, unsigned int keylen)
- {
- unsigned long alignmask = crypto_shash_alignmask(parent);
- struct cmac_tfm_ctx *ctx = crypto_shash_ctx(parent);
- unsigned int bs = crypto_shash_blocksize(parent);
- __be64 *consts = PTR_ALIGN((void *)ctx->ctx,
- (alignmask | (__alignof__(__be64) - 1)) + 1);
- u64 _const[2];
- int i, err = 0;
- u8 msb_mask, gfmask;
- err = crypto_cipher_setkey(ctx->child, inkey, keylen);
- if (err)
- return err;
- /* encrypt the zero block */
- memset(consts, 0, bs);
- crypto_cipher_encrypt_one(ctx->child, (u8 *)consts, (u8 *)consts);
- switch (bs) {
- case 16:
- gfmask = 0x87;
- _const[0] = be64_to_cpu(consts[1]);
- _const[1] = be64_to_cpu(consts[0]);
- /* gf(2^128) multiply zero-ciphertext with u and u^2 */
- for (i = 0; i < 4; i += 2) {
- msb_mask = ((s64)_const[1] >> 63) & gfmask;
- _const[1] = (_const[1] << 1) | (_const[0] >> 63);
- _const[0] = (_const[0] << 1) ^ msb_mask;
- consts[i + 0] = cpu_to_be64(_const[1]);
- consts[i + 1] = cpu_to_be64(_const[0]);
- }
- break;
- case 8:
- gfmask = 0x1B;
- _const[0] = be64_to_cpu(consts[0]);
- /* gf(2^64) multiply zero-ciphertext with u and u^2 */
- for (i = 0; i < 2; i++) {
- msb_mask = ((s64)_const[0] >> 63) & gfmask;
- _const[0] = (_const[0] << 1) ^ msb_mask;
- consts[i] = cpu_to_be64(_const[0]);
- }
- break;
- }
- return 0;
- }
- static int crypto_cmac_digest_init(struct shash_desc *pdesc)
- {
- unsigned long alignmask = crypto_shash_alignmask(pdesc->tfm);
- struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
- int bs = crypto_shash_blocksize(pdesc->tfm);
- u8 *prev = PTR_ALIGN((void *)ctx->ctx, alignmask + 1) + bs;
- ctx->len = 0;
- memset(prev, 0, bs);
- return 0;
- }
- static int crypto_cmac_digest_update(struct shash_desc *pdesc, const u8 *p,
- unsigned int len)
- {
- struct crypto_shash *parent = pdesc->tfm;
- unsigned long alignmask = crypto_shash_alignmask(parent);
- struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
- struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
- struct crypto_cipher *tfm = tctx->child;
- int bs = crypto_shash_blocksize(parent);
- u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
- u8 *prev = odds + bs;
- /* checking the data can fill the block */
- if ((ctx->len + len) <= bs) {
- memcpy(odds + ctx->len, p, len);
- ctx->len += len;
- return 0;
- }
- /* filling odds with new data and encrypting it */
- memcpy(odds + ctx->len, p, bs - ctx->len);
- len -= bs - ctx->len;
- p += bs - ctx->len;
- crypto_xor(prev, odds, bs);
- crypto_cipher_encrypt_one(tfm, prev, prev);
- /* clearing the length */
- ctx->len = 0;
- /* encrypting the rest of data */
- while (len > bs) {
- crypto_xor(prev, p, bs);
- crypto_cipher_encrypt_one(tfm, prev, prev);
- p += bs;
- len -= bs;
- }
- /* keeping the surplus of blocksize */
- if (len) {
- memcpy(odds, p, len);
- ctx->len = len;
- }
- return 0;
- }
- static int crypto_cmac_digest_final(struct shash_desc *pdesc, u8 *out)
- {
- struct crypto_shash *parent = pdesc->tfm;
- unsigned long alignmask = crypto_shash_alignmask(parent);
- struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
- struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
- struct crypto_cipher *tfm = tctx->child;
- int bs = crypto_shash_blocksize(parent);
- u8 *consts = PTR_ALIGN((void *)tctx->ctx,
- (alignmask | (__alignof__(__be64) - 1)) + 1);
- u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
- u8 *prev = odds + bs;
- unsigned int offset = 0;
- if (ctx->len != bs) {
- unsigned int rlen;
- u8 *p = odds + ctx->len;
- *p = 0x80;
- p++;
- rlen = bs - ctx->len - 1;
- if (rlen)
- memset(p, 0, rlen);
- offset += bs;
- }
- crypto_xor(prev, odds, bs);
- crypto_xor(prev, consts + offset, bs);
- crypto_cipher_encrypt_one(tfm, out, prev);
- return 0;
- }
- static int cmac_init_tfm(struct crypto_tfm *tfm)
- {
- struct crypto_cipher *cipher;
- struct crypto_instance *inst = (void *)tfm->__crt_alg;
- struct crypto_cipher_spawn *spawn = crypto_instance_ctx(inst);
- struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
- cipher = crypto_spawn_cipher(spawn);
- if (IS_ERR(cipher))
- return PTR_ERR(cipher);
- ctx->child = cipher;
- return 0;
- };
- static void cmac_exit_tfm(struct crypto_tfm *tfm)
- {
- struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
- crypto_free_cipher(ctx->child);
- }
- static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
- {
- struct shash_instance *inst;
- struct crypto_cipher_spawn *spawn;
- struct crypto_alg *alg;
- unsigned long alignmask;
- u32 mask;
- int err;
- err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH, &mask);
- if (err)
- return err;
- inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
- if (!inst)
- return -ENOMEM;
- spawn = shash_instance_ctx(inst);
- err = crypto_grab_cipher(spawn, shash_crypto_instance(inst),
- crypto_attr_alg_name(tb[1]), 0, mask);
- if (err)
- goto err_free_inst;
- alg = crypto_spawn_cipher_alg(spawn);
- switch (alg->cra_blocksize) {
- case 16:
- case 8:
- break;
- default:
- err = -EINVAL;
- goto err_free_inst;
- }
- err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg);
- if (err)
- goto err_free_inst;
- alignmask = alg->cra_alignmask;
- inst->alg.base.cra_alignmask = alignmask;
- inst->alg.base.cra_priority = alg->cra_priority;
- inst->alg.base.cra_blocksize = alg->cra_blocksize;
- inst->alg.digestsize = alg->cra_blocksize;
- inst->alg.descsize =
- ALIGN(sizeof(struct cmac_desc_ctx), crypto_tfm_ctx_alignment())
- + (alignmask & ~(crypto_tfm_ctx_alignment() - 1))
- + alg->cra_blocksize * 2;
- inst->alg.base.cra_ctxsize =
- ALIGN(sizeof(struct cmac_tfm_ctx), crypto_tfm_ctx_alignment())
- + ((alignmask | (__alignof__(__be64) - 1)) &
- ~(crypto_tfm_ctx_alignment() - 1))
- + alg->cra_blocksize * 2;
- inst->alg.base.cra_init = cmac_init_tfm;
- inst->alg.base.cra_exit = cmac_exit_tfm;
- inst->alg.init = crypto_cmac_digest_init;
- inst->alg.update = crypto_cmac_digest_update;
- inst->alg.final = crypto_cmac_digest_final;
- inst->alg.setkey = crypto_cmac_digest_setkey;
- inst->free = shash_free_singlespawn_instance;
- err = shash_register_instance(tmpl, inst);
- if (err) {
- err_free_inst:
- shash_free_singlespawn_instance(inst);
- }
- return err;
- }
- static struct crypto_template crypto_cmac_tmpl = {
- .name = "cmac",
- .create = cmac_create,
- .module = THIS_MODULE,
- };
- static int __init crypto_cmac_module_init(void)
- {
- return crypto_register_template(&crypto_cmac_tmpl);
- }
- static void __exit crypto_cmac_module_exit(void)
- {
- crypto_unregister_template(&crypto_cmac_tmpl);
- }
- subsys_initcall(crypto_cmac_module_init);
- module_exit(crypto_cmac_module_exit);
- MODULE_LICENSE("GPL");
- MODULE_DESCRIPTION("CMAC keyed hash algorithm");
- MODULE_ALIAS_CRYPTO("cmac");
- MODULE_IMPORT_NS(CRYPTO_INTERNAL);
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