crypto: add CMAC support to CryptoAPI

Patch adds support for NIST recommended block cipher mode CMAC to CryptoAPI.

This work is based on Tom St Denis' earlier patch,
 http://marc.info/?l=linux-crypto-vger&m=135877306305466&w=2

Cc: Tom St Denis <tstdenis@elliptictech.com>
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 315 insertions, 0 deletions

diff --git a/crypto/cmac.c b/crypto/cmac.c
new file mode 100644
index 0000000..50880cf
--- /dev/null
+++ b/crypto/cmac.c
@@ -0,0 +1,315 @@
+/*
+ * 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");