FreeBSD/Linux Kernel Cross Reference
sys/crypto/ghash-generic.c

     /*
      * 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 (!ctx->gf128)
                    return -ENOKEY;
    
            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;
   
           if (!ctx->gf128)
                   return -ENOKEY;
   
           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_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");

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