ghash_s390.c

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/*
 * Cryptographic API.
 *
 * s390 implementation of the GHASH algorithm for GCM (Galois/Counter Mode).
 *
 * Copyright IBM Corp. 2011
 * Author(s): Gerald Schaefer <[email protected]>
 */

#include <crypto/internal/hash.h>
#include <linux/module.h>

#include "crypt_s390.h"

#define GHASH_BLOCK_SIZE    16
#define GHASH_DIGEST_SIZE   16

struct ghash_ctx {
    u8 icv[16];
    u8 key[16];
};

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;
    }

    memcpy(ctx->key, key, GHASH_BLOCK_SIZE);
    memset(ctx->icv, 0, GHASH_BLOCK_SIZE);

    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);
    unsigned int n;
    u8 *buf = dctx->buffer;
    int ret;

    if (dctx->bytes) {
        u8 *pos = buf + (GHASH_BLOCK_SIZE - dctx->bytes);

        n = min(srclen, dctx->bytes);
        dctx->bytes -= n;
        srclen -= n;

        memcpy(pos, src, n);
        src += n;

        if (!dctx->bytes) {
            ret = crypt_s390_kimd(KIMD_GHASH, ctx, buf,
                          GHASH_BLOCK_SIZE);
            BUG_ON(ret != GHASH_BLOCK_SIZE);
        }
    }

    n = srclen & ~(GHASH_BLOCK_SIZE - 1);
    if (n) {
        ret = crypt_s390_kimd(KIMD_GHASH, ctx, src, n);
        BUG_ON(ret != n);
        src += n;
        srclen -= n;
    }

    if (srclen) {
        dctx->bytes = GHASH_BLOCK_SIZE - srclen;
        memcpy(buf, src, srclen);
    }

    return 0;
}

static void ghash_flush(struct ghash_ctx *ctx, struct ghash_desc_ctx *dctx)
{
    u8 *buf = dctx->buffer;
    int ret;

    if (dctx->bytes) {
        u8 *pos = buf + (GHASH_BLOCK_SIZE - dctx->bytes);

        memset(pos, 0, dctx->bytes);

        ret = crypt_s390_kimd(KIMD_GHASH, ctx, buf, GHASH_BLOCK_SIZE);
        BUG_ON(ret != GHASH_BLOCK_SIZE);
    }

    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);

    ghash_flush(ctx, dctx);
    memcpy(dst, ctx->icv, GHASH_BLOCK_SIZE);

    return 0;
}

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-s390",
        .cra_priority       = CRYPT_S390_PRIORITY,
        .cra_flags      = CRYPTO_ALG_TYPE_SHASH,
        .cra_blocksize      = GHASH_BLOCK_SIZE,
        .cra_ctxsize        = sizeof(struct ghash_ctx),
        .cra_module     = THIS_MODULE,
    },
};

static int __init ghash_mod_init(void)
{
    if (!crypt_s390_func_available(KIMD_GHASH,
                       CRYPT_S390_MSA | CRYPT_S390_MSA4))
        return -EOPNOTSUPP;

    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_ALIAS("ghash");

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("GHASH Message Digest Algorithm, s390 implementation");