Re: [RFC 1/7] crypto: Add GHASH digest algorithm for GCM

[Huang Ying]

On Thu, 2009-06-18 at 04:04 +0800, Sebastian Andrzej Siewior wrote:
> * Huang Ying | 2009-06-11 15:10:26 [+0800]:
> 
> >GHASH is implemented as a shash algorithm. The actual implementation
> >is copied from gcm.c. This makes it possible to add
> >architecture/hardware accelerated GHASH implementation.
> >
> >Signed-off-by: Huang Ying <ying.huang@xxxxxxxxx>
> >
> >---
> > crypto/Kconfig         |    7 +
> > crypto/Makefile        |    2 
> > crypto/ghash-generic.c |  179 +++++++++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 188 insertions(+)
> >
> >--- /dev/null
> >+++ b/crypto/ghash-generic.c
> >@@ -0,0 +1,179 @@
> >+/*
> >+ * GHASH: digest algorithm for GCM (Galois/Counter Mode).
> >+ *
> >+ * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@xxxxxx>
> >+ * Copyright (c) 2009 Intel Corp.
> >+ *   Author: Huang Ying <ying.huang@xxxxxxxxx>
> >+ *
> >+ * The algorithm implementation is copied from gcm.c.
> >+ *
> >+ * This program is free software; you can redistribute it and/or modify it
> >+ * under the terms of the GNU General Public License version 2 as published
> >+ * by the Free Software Foundation.
> >+ */
> >+
> >+#include <linux/module.h>
> >+#include <linux/init.h>
> >+#include <linux/kernel.h>
> >+#include <linux/crypto.h>
> >+#include <crypto/gf128mul.h>
> >+#include <crypto/algapi.h>
> >+#include <crypto/internal/hash.h>
> Do you mind to sort them?

Sorry, can you tell me what is the better order?

> >+
> >+#define GHASH_BLOCK_SIZE	16
> >+#define GHASH_DIGEST_SIZE	16
> >+
> >+struct ghash_ctx {
> >+	struct gf128mul_4k *gf128;
> >+};
> >+
> >+struct ghash_desc_ctx {
> >+	u8 buffer[16];
> >+	u32 bytes;
> >+};
> >+
> >+static int ghash_init(struct shash_desc *desc)
> >+{
> >+	struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
> >+
> >+	dctx->bytes = 0;
> >+	memset(dctx->buffer, 0, 16);
> >+
> you could memset() the whole struct at once

Yes. That is better, you are right.

> >+	return 0;
> >+}
> >+
> >+static int ghash_setkey(struct crypto_shash *tfm,
> >+			const u8 *key, unsigned int keylen)
> >+{
> >+	struct ghash_ctx *ctx = crypto_shash_ctx(tfm);
> >+
> >+	if (keylen != 16) {
> >+		crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
> >+		return -EINVAL;
> >+	}
> >+
> >+	if (ctx->gf128)
> >+		gf128mul_free_4k(ctx->gf128);
> >+	ctx->gf128 = gf128mul_init_4k_lle((be128 *)key);
> >+	if (!ctx->gf128)
> >+		return -ENOMEM;
> >+
> >+	return 0;
> >+}
> >+
> >+static int ghash_update(struct shash_desc *desc,
> >+			 const u8 *src, unsigned int srclen)
> >+{
> >+	struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
> >+	struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
> >+	u8 *dst = dctx->buffer;
> >+
> >+	if (dctx->bytes) {
> >+		int n = min(srclen, dctx->bytes);
> >+		u8 *pos = dst + (16 - dctx->bytes);
> >+
> >+		dctx->bytes -= n;
> >+		srclen -= n;
> >+
> >+		while (n--)
> >+			*pos++ ^= *src++;
> >+
> >+		if (!dctx->bytes)
> >+			gf128mul_4k_lle((be128 *)dst, ctx->gf128);
> >+	}
> >+
> >+	while (srclen >= 16) {
> >+		crypto_xor(dst, src, 16);
> >+		gf128mul_4k_lle((be128 *)dst, ctx->gf128);
> >+		src += 16;
> >+		srclen -= 16;
> >+	}
> >+
> >+	if (srclen) {
> >+		dctx->bytes = 16 - srclen;
> >+		while (srclen--)
> >+			*dst++ ^= *src++;
> >+	}
> >+
> 16 here looks like GHASH_BLOCK_SIZE to me

Yes. I will change most 16 to corresponding symbol name.

> >+	return 0;
> >+}
> >+
> >+static void ghash_flush(struct ghash_ctx *ctx, struct ghash_desc_ctx *dctx)
> >+{
> >+	u8 *dst = dctx->buffer;
> >+
> >+	if (dctx->bytes) {
> >+		u8 *tmp = dst + (16 - dctx->bytes);
> >+
> >+		while (dctx->bytes--)
> >+			*tmp++ ^= 0;
> >+
> >+		gf128mul_4k_lle((be128 *)dst, ctx->gf128);
> >+	}
> >+
> >+	dctx->bytes = 0;
> >+}
> >+
> >+static int ghash_final(struct shash_desc *desc, u8 *dst)
> >+{
> >+	struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
> >+	struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
> >+	u8 *buf = dctx->buffer;
> >+
> >+	ghash_flush(ctx, dctx);
> >+	memcpy(dst, buf, 16);
> >+
> >+	return 0;
> >+}
> >+
> >+static int ghash_init_tfm(struct crypto_tfm *tfm)
> >+{
> >+	struct ghash_ctx *ctx = crypto_tfm_ctx(tfm);
> >+	ctx->gf128 = NULL;
> 
> Unless I'm mistaken, this is called once on allocation and this ctx is
> allocated via kzalloc().

Yes. it is alloced via kzalloc. Can we just rely on this? Should we add
that assumption to somewhere such as document of comments.

> >+	return 0;
> >+}
> >+
> >+static void ghash_exit_tfm(struct crypto_tfm *tfm)
> >+{
> >+	struct ghash_ctx *ctx = crypto_tfm_ctx(tfm);
> >+	if (ctx->gf128)
> >+		gf128mul_free_4k(ctx->gf128);
> >+}
> >+
> >+static struct shash_alg ghash_alg = {
> >+	.digestsize	= GHASH_DIGEST_SIZE,
> >+	.init		= ghash_init,
> >+	.update		= ghash_update,
> >+	.final		= ghash_final,
> >+	.setkey		= ghash_setkey,
> >+	.descsize	= sizeof(struct ghash_desc_ctx),
> >+	.base		= {
> >+		.cra_name		= "ghash",
> >+		.cra_driver_name	= "ghash-generic",
> >+		.cra_priority		= 100,
> >+		.cra_flags		= CRYPTO_ALG_TYPE_SHASH,
> >+		.cra_blocksize		= GHASH_BLOCK_SIZE,
> >+		.cra_ctxsize		= sizeof(struct ghash_ctx),
> >+		.cra_module		= THIS_MODULE,
> >+		.cra_list		= LIST_HEAD_INIT(ghash_alg.base.cra_list),
> >+		.cra_init		= ghash_init_tfm,
> >+		.cra_exit		= ghash_exit_tfm,
> >+	},
> >+};
> >+
> >+static int __init ghash_mod_init(void)
> >+{
> >+	return crypto_register_shash(&ghash_alg);
> >+}
> >+
> >+static void __exit ghash_mod_exit(void)
> >+{
> >+	crypto_unregister_shash(&ghash_alg);
> >+}
> >+
> >+module_init(ghash_mod_init);
> >+module_exit(ghash_mod_exit);
> >+
> >+MODULE_LICENSE("GPL");
> >+MODULE_DESCRIPTION("GHASH Message Digest Algorithm");
> >+MODULE_ALIAS("ghash");
> >--- a/crypto/Kconfig
> >+++ b/crypto/Kconfig
> >@@ -419,6 +419,13 @@ config CRYPTO_WP512
> > 	  See also:
> > 	  <http://planeta.terra.com.br/informatica/paulobarreto/WhirlpoolPage.html>
> > 
> >+config CRYPTO_GHASH
> >+	tristate "GHASH digest algorithm"
> >+	select CRYPTO_SHASH
> >+	select CRYPTO_GF128MUL
> >+	help
> >+	  GHASH is message digest algorithm for GCM (Galois/Counter Mode).
> >+
> Could you please move it to the 'G' section

OK. I will do this.

> > comment "Ciphers"
> > 
> > config CRYPTO_AES
> >--- a/crypto/Makefile
> >+++ b/crypto/Makefile
> >@@ -83,6 +83,8 @@ obj-$(CONFIG_CRYPTO_RNG2) += rng.o
> > obj-$(CONFIG_CRYPTO_RNG2) += krng.o
> > obj-$(CONFIG_CRYPTO_ANSI_CPRNG) += ansi_cprng.o
> > obj-$(CONFIG_CRYPTO_TEST) += tcrypt.o
> >+obj-$(CONFIG_CRYPTO_MD5) += md5.o
> md5?

Sorry, I will remove this, and move GHASH line to appropriate position.

> >+obj-$(CONFIG_CRYPTO_GHASH) += ghash-generic.o
> > 
> > #
> > # generic algorithms and the async_tx api
> >
> >

Best Regards,
Huang Ying

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