the-tree/crypto/cmac.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  * CMAC: Cipher Block Mode for Authentication
0004  *
0005  * Copyright © 2013 Jussi Kivilinna <jussi.kivilinna@iki.fi>
0006  *
0007  * Based on work by:
0008  *  Copyright © 2013 Tom St Denis <tstdenis@elliptictech.com>
0009  * Based on crypto/xcbc.c:
0010  *  Copyright © 2006 USAGI/WIDE Project,
0011  *   Author: Kazunori Miyazawa <miyazawa@linux-ipv6.org>
0012  */
0013
0014 #include <crypto/internal/cipher.h>
0015 #include <crypto/internal/hash.h>
0016 #include <linux/err.h>
0017 #include <linux/kernel.h>
0018 #include <linux/module.h>
0019
0020 /*
0021  * +------------------------
0022  * | <parent tfm>
0023  * +------------------------
0024  * | cmac_tfm_ctx
0025  * +------------------------
0026  * | consts (block size * 2)
0027  * +------------------------
0028  */
0029 struct cmac_tfm_ctx {
0030     struct crypto_cipher *child;
0031     u8 ctx[];
0032 };
0033
0034 /*
0035  * +------------------------
0036  * | <shash desc>
0037  * +------------------------
0038  * | cmac_desc_ctx
0039  * +------------------------
0040  * | odds (block size)
0041  * +------------------------
0042  * | prev (block size)
0043  * +------------------------
0044  */
0045 struct cmac_desc_ctx {
0046     unsigned int len;
0047     u8 ctx[];
0048 };
0049
0050 static int crypto_cmac_digest_setkey(struct crypto_shash *parent,
0051                      const u8 *inkey, unsigned int keylen)
0052 {
0053     unsigned long alignmask = crypto_shash_alignmask(parent);
0054     struct cmac_tfm_ctx *ctx = crypto_shash_ctx(parent);
0055     unsigned int bs = crypto_shash_blocksize(parent);
0056     __be64 *consts = PTR_ALIGN((void *)ctx->ctx,
0057                    (alignmask | (__alignof__(__be64) - 1)) + 1);
0058     u64 _const[2];
0059     int i, err = 0;
0060     u8 msb_mask, gfmask;
0061
0062     err = crypto_cipher_setkey(ctx->child, inkey, keylen);
0063     if (err)
0064         return err;
0065
0066     /* encrypt the zero block */
0067     memset(consts, 0, bs);
0068     crypto_cipher_encrypt_one(ctx->child, (u8 *)consts, (u8 *)consts);
0069
0070     switch (bs) {
0071     case 16:
0072         gfmask = 0x87;
0073         _const[0] = be64_to_cpu(consts[1]);
0074         _const[1] = be64_to_cpu(consts[0]);
0075
0076         /* gf(2^128) multiply zero-ciphertext with u and u^2 */
0077         for (i = 0; i < 4; i += 2) {
0078             msb_mask = ((s64)_const[1] >> 63) & gfmask;
0079             _const[1] = (_const[1] << 1) | (_const[0] >> 63);
0080             _const[0] = (_const[0] << 1) ^ msb_mask;
0081
0082             consts[i + 0] = cpu_to_be64(_const[1]);
0083             consts[i + 1] = cpu_to_be64(_const[0]);
0084         }
0085
0086         break;
0087     case 8:
0088         gfmask = 0x1B;
0089         _const[0] = be64_to_cpu(consts[0]);
0090
0091         /* gf(2^64) multiply zero-ciphertext with u and u^2 */
0092         for (i = 0; i < 2; i++) {
0093             msb_mask = ((s64)_const[0] >> 63) & gfmask;
0094             _const[0] = (_const[0] << 1) ^ msb_mask;
0095
0096             consts[i] = cpu_to_be64(_const[0]);
0097         }
0098
0099         break;
0100     }
0101
0102     return 0;
0103 }
0104
0105 static int crypto_cmac_digest_init(struct shash_desc *pdesc)
0106 {
0107     unsigned long alignmask = crypto_shash_alignmask(pdesc->tfm);
0108     struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
0109     int bs = crypto_shash_blocksize(pdesc->tfm);
0110     u8 *prev = PTR_ALIGN((void *)ctx->ctx, alignmask + 1) + bs;
0111
0112     ctx->len = 0;
0113     memset(prev, 0, bs);
0114
0115     return 0;
0116 }
0117
0118 static int crypto_cmac_digest_update(struct shash_desc *pdesc, const u8 *p,
0119                      unsigned int len)
0120 {
0121     struct crypto_shash *parent = pdesc->tfm;
0122     unsigned long alignmask = crypto_shash_alignmask(parent);
0123     struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
0124     struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
0125     struct crypto_cipher *tfm = tctx->child;
0126     int bs = crypto_shash_blocksize(parent);
0127     u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
0128     u8 *prev = odds + bs;
0129
0130     /* checking the data can fill the block */
0131     if ((ctx->len + len) <= bs) {
0132         memcpy(odds + ctx->len, p, len);
0133         ctx->len += len;
0134         return 0;
0135     }
0136
0137     /* filling odds with new data and encrypting it */
0138     memcpy(odds + ctx->len, p, bs - ctx->len);
0139     len -= bs - ctx->len;
0140     p += bs - ctx->len;
0141
0142     crypto_xor(prev, odds, bs);
0143     crypto_cipher_encrypt_one(tfm, prev, prev);
0144
0145     /* clearing the length */
0146     ctx->len = 0;
0147
0148     /* encrypting the rest of data */
0149     while (len > bs) {
0150         crypto_xor(prev, p, bs);
0151         crypto_cipher_encrypt_one(tfm, prev, prev);
0152         p += bs;
0153         len -= bs;
0154     }
0155
0156     /* keeping the surplus of blocksize */
0157     if (len) {
0158         memcpy(odds, p, len);
0159         ctx->len = len;
0160     }
0161
0162     return 0;
0163 }
0164
0165 static int crypto_cmac_digest_final(struct shash_desc *pdesc, u8 *out)
0166 {
0167     struct crypto_shash *parent = pdesc->tfm;
0168     unsigned long alignmask = crypto_shash_alignmask(parent);
0169     struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
0170     struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
0171     struct crypto_cipher *tfm = tctx->child;
0172     int bs = crypto_shash_blocksize(parent);
0173     u8 *consts = PTR_ALIGN((void *)tctx->ctx,
0174                    (alignmask | (__alignof__(__be64) - 1)) + 1);
0175     u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
0176     u8 *prev = odds + bs;
0177     unsigned int offset = 0;
0178
0179     if (ctx->len != bs) {
0180         unsigned int rlen;
0181         u8 *p = odds + ctx->len;
0182
0183         *p = 0x80;
0184         p++;
0185
0186         rlen = bs - ctx->len - 1;
0187         if (rlen)
0188             memset(p, 0, rlen);
0189
0190         offset += bs;
0191     }
0192
0193     crypto_xor(prev, odds, bs);
0194     crypto_xor(prev, consts + offset, bs);
0195
0196     crypto_cipher_encrypt_one(tfm, out, prev);
0197
0198     return 0;
0199 }
0200
0201 static int cmac_init_tfm(struct crypto_tfm *tfm)
0202 {
0203     struct crypto_cipher *cipher;
0204     struct crypto_instance *inst = (void *)tfm->__crt_alg;
0205     struct crypto_cipher_spawn *spawn = crypto_instance_ctx(inst);
0206     struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
0207
0208     cipher = crypto_spawn_cipher(spawn);
0209     if (IS_ERR(cipher))
0210         return PTR_ERR(cipher);
0211
0212     ctx->child = cipher;
0213
0214     return 0;
0215 };
0216
0217 static void cmac_exit_tfm(struct crypto_tfm *tfm)
0218 {
0219     struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
0220     crypto_free_cipher(ctx->child);
0221 }
0222
0223 static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
0224 {
0225     struct shash_instance *inst;
0226     struct crypto_cipher_spawn *spawn;
0227     struct crypto_alg *alg;
0228     unsigned long alignmask;
0229     u32 mask;
0230     int err;
0231
0232     err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH, &mask);
0233     if (err)
0234         return err;
0235
0236     inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
0237     if (!inst)
0238         return -ENOMEM;
0239     spawn = shash_instance_ctx(inst);
0240
0241     err = crypto_grab_cipher(spawn, shash_crypto_instance(inst),
0242                  crypto_attr_alg_name(tb[1]), 0, mask);
0243     if (err)
0244         goto err_free_inst;
0245     alg = crypto_spawn_cipher_alg(spawn);
0246
0247     switch (alg->cra_blocksize) {
0248     case 16:
0249     case 8:
0250         break;
0251     default:
0252         err = -EINVAL;
0253         goto err_free_inst;
0254     }
0255
0256     err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg);
0257     if (err)
0258         goto err_free_inst;
0259
0260     alignmask = alg->cra_alignmask;
0261     inst->alg.base.cra_alignmask = alignmask;
0262     inst->alg.base.cra_priority = alg->cra_priority;
0263     inst->alg.base.cra_blocksize = alg->cra_blocksize;
0264
0265     inst->alg.digestsize = alg->cra_blocksize;
0266     inst->alg.descsize =
0267         ALIGN(sizeof(struct cmac_desc_ctx), crypto_tfm_ctx_alignment())
0268         + (alignmask & ~(crypto_tfm_ctx_alignment() - 1))
0269         + alg->cra_blocksize * 2;
0270
0271     inst->alg.base.cra_ctxsize =
0272         ALIGN(sizeof(struct cmac_tfm_ctx), crypto_tfm_ctx_alignment())
0273         + ((alignmask | (__alignof__(__be64) - 1)) &
0274            ~(crypto_tfm_ctx_alignment() - 1))
0275         + alg->cra_blocksize * 2;
0276
0277     inst->alg.base.cra_init = cmac_init_tfm;
0278     inst->alg.base.cra_exit = cmac_exit_tfm;
0279
0280     inst->alg.init = crypto_cmac_digest_init;
0281     inst->alg.update = crypto_cmac_digest_update;
0282     inst->alg.final = crypto_cmac_digest_final;
0283     inst->alg.setkey = crypto_cmac_digest_setkey;
0284
0285     inst->free = shash_free_singlespawn_instance;
0286
0287     err = shash_register_instance(tmpl, inst);
0288     if (err) {
0289 err_free_inst:
0290         shash_free_singlespawn_instance(inst);
0291     }
0292     return err;
0293 }
0294
0295 static struct crypto_template crypto_cmac_tmpl = {
0296     .name = "cmac",
0297     .create = cmac_create,
0298     .module = THIS_MODULE,
0299 };
0300
0301 static int __init crypto_cmac_module_init(void)
0302 {
0303     return crypto_register_template(&crypto_cmac_tmpl);
0304 }
0305
0306 static void __exit crypto_cmac_module_exit(void)
0307 {
0308     crypto_unregister_template(&crypto_cmac_tmpl);
0309 }
0310
0311 subsys_initcall(crypto_cmac_module_init);
0312 module_exit(crypto_cmac_module_exit);
0313
0314 MODULE_LICENSE("GPL");
0315 MODULE_DESCRIPTION("CMAC keyed hash algorithm");
0316 MODULE_ALIAS_CRYPTO("cmac");
0317 MODULE_IMPORT_NS(CRYPTO_INTERNAL);