crypto: ghash - Add GHASH digest algorithm for GCM

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@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 170 insertions, 0 deletions

diff --git a/crypto/ghash-generic.c b/crypto/ghash-generic.c
new file mode 100644
index 000000000000..be4425616931
--- /dev/null
+++ b/crypto/ghash-generic.c
@@ -0,0 +1,170 @@
+/*
+ * GHASH: digest algorithm for GCM (Galois/Counter Mode).
+ *
+ * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi>
+ * Copyright (c) 2009 Intel Corp.
+ *   Author: Huang Ying <ying.huang@intel.com>
+ *
+ * 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 <crypto/algapi.h>
+#include <crypto/gf128mul.h>
+#include <crypto/internal/hash.h>
+#include <linux/crypto.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#define GHASH_BLOCK_SIZE        16
+#define GHASH_DIGEST_SIZE       16
+
+struct ghash_ctx {
+        struct gf128mul_4k *gf128;
+};
+
+struct ghash_desc_ctx {
+        u8 buffer[GHASH_BLOCK_SIZE];
+        u32 bytes;
+};
+
+static int ghash_init(struct shash_desc *desc)
+{
+        struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
+
+        memset(dctx, 0, sizeof(*dctx));
+
+        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 != GHASH_BLOCK_SIZE) {
+                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 + (GHASH_BLOCK_SIZE - dctx->bytes);
+
+                dctx->bytes -= n;
+                srclen -= n;
+
+                while (n--)
+                        *pos++ ^= *src++;
+
+                if (!dctx->bytes)
+                        gf128mul_4k_lle((be128 *)dst, ctx->gf128);
+        }
+
+        while (srclen >= GHASH_BLOCK_SIZE) {
+                crypto_xor(dst, src, GHASH_BLOCK_SIZE);
+                gf128mul_4k_lle((be128 *)dst, ctx->gf128);
+                src += GHASH_BLOCK_SIZE;
+                srclen -= GHASH_BLOCK_SIZE;
+        }
+
+        if (srclen) {
+                dctx->bytes = GHASH_BLOCK_SIZE - srclen;
+                while (srclen--)
+                        *dst++ ^= *src++;
+        }
+
+        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 + (GHASH_BLOCK_SIZE - 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, GHASH_BLOCK_SIZE);
+
+        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_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");