/* * CMAC: Cipher Block Mode for Authentication * * Copyright © 2013 Jussi Kivilinna <jussi.kivilinna@iki.fi> * * Based on work by: * Copyright © 2013 Tom St Denis <tstdenis@elliptictech.com> * Based on crypto/xcbc.c: * Copyright © 2006 USAGI/WIDE Project, * Author: Kazunori Miyazawa <miyazawa@linux-ipv6.org> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * */ #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 + 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 + 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_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_alg *alg; unsigned long alignmask; int err; err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH); if (err) return err; alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, CRYPTO_ALG_TYPE_MASK); if (IS_ERR(alg)) return PTR_ERR(alg); switch (alg->cra_blocksize) { case 16: case 8: break; default: goto out_put_alg; } inst = shash_alloc_instance("cmac", alg); err = PTR_ERR(inst); if (IS_ERR(inst)) goto out_put_alg; err = crypto_init_spawn(shash_instance_ctx(inst), alg, shash_crypto_instance(inst), CRYPTO_ALG_TYPE_MASK); if (err) goto out_free_inst; alignmask = alg->cra_alignmask | (sizeof(long) - 1); 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), alignmask + 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; err = shash_register_instance(tmpl, inst); if (err) { out_free_inst: shash_free_instance(shash_crypto_instance(inst)); } out_put_alg: crypto_mod_put(alg); return err; } static struct crypto_template crypto_cmac_tmpl = { .name = "cmac", .create = cmac_create, .free = shash_free_instance, .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); } module_init(crypto_cmac_module_init); module_exit(crypto_cmac_module_exit); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("CMAC keyed hash algorithm");