/*
   * Poly1305 authenticator algorithm, RFC7539
   *
   * Copyright (C) 2015 Martin Willi
   *
   * Based on public domain code by Andrew Moon and Daniel J. Bernstein.
   *
   * 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/algapi.h>
  #include <crypto/internal/hash.h>

  #include <crypto/internal/poly1305.h>

  #include <linux/crypto.h>
  #include <linux/kernel.h>
  #include <linux/module.h>

  #include <asm/unaligned.h>

  static int crypto_poly1305_init(struct shash_desc *desc)

  {
  	struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);

  	poly1305_core_init(&dctx->h);

  	dctx->buflen = 0;

  	dctx->rset = 0;

  	dctx->sset = false;

  
  	return 0;
  }

  static unsigned int crypto_poly1305_setdesckey(struct poly1305_desc_ctx *dctx,
  					       const u8 *src, unsigned int srclen)
  {
  	if (!dctx->sset) {
  		if (!dctx->rset && srclen >= POLY1305_BLOCK_SIZE) {
  			poly1305_core_setkey(&dctx->core_r, src);
  			src += POLY1305_BLOCK_SIZE;
  			srclen -= POLY1305_BLOCK_SIZE;
  			dctx->rset = 2;
  		}
  		if (srclen >= POLY1305_BLOCK_SIZE) {
  			dctx->s[0] = get_unaligned_le32(src +  0);
  			dctx->s[1] = get_unaligned_le32(src +  4);
  			dctx->s[2] = get_unaligned_le32(src +  8);
  			dctx->s[3] = get_unaligned_le32(src + 12);
  			src += POLY1305_BLOCK_SIZE;
  			srclen -= POLY1305_BLOCK_SIZE;
  			dctx->sset = true;
  		}
  	}
  	return srclen;
  }

  static void poly1305_blocks(struct poly1305_desc_ctx *dctx, const u8 *src,
  			    unsigned int srclen)

  {
  	unsigned int datalen;
  
  	if (unlikely(!dctx->sset)) {
  		datalen = crypto_poly1305_setdesckey(dctx, src, srclen);
  		src += srclen - datalen;
  		srclen = datalen;
  	}

  	poly1305_core_blocks(&dctx->h, &dctx->core_r, src,

  			     srclen / POLY1305_BLOCK_SIZE, 1);

  }

  static int crypto_poly1305_update(struct shash_desc *desc,
  				  const u8 *src, unsigned int srclen)

  {
  	struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);

  	unsigned int bytes;
  
  	if (unlikely(dctx->buflen)) {
  		bytes = min(srclen, POLY1305_BLOCK_SIZE - dctx->buflen);
  		memcpy(dctx->buf + dctx->buflen, src, bytes);
  		src += bytes;
  		srclen -= bytes;
  		dctx->buflen += bytes;
  
  		if (dctx->buflen == POLY1305_BLOCK_SIZE) {

  			poly1305_blocks(dctx, dctx->buf,

  					POLY1305_BLOCK_SIZE);

  			dctx->buflen = 0;
  		}
  	}
  
  	if (likely(srclen >= POLY1305_BLOCK_SIZE)) {

  		poly1305_blocks(dctx, src, srclen);

  		src += srclen - (srclen % POLY1305_BLOCK_SIZE);
  		srclen %= POLY1305_BLOCK_SIZE;

  	}
  
  	if (unlikely(srclen)) {
  		dctx->buflen = srclen;
  		memcpy(dctx->buf, src, srclen);
  	}
  
  	return 0;
  }

  static int crypto_poly1305_final(struct shash_desc *desc, u8 *dst)

  {
  	struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);

  
  	if (unlikely(!dctx->sset))
  		return -ENOKEY;

  	poly1305_final_generic(dctx, dst);

  	return 0;
  }
  
  static struct shash_alg poly1305_alg = {
  	.digestsize	= POLY1305_DIGEST_SIZE,

  	.init		= crypto_poly1305_init,
  	.update		= crypto_poly1305_update,
  	.final		= crypto_poly1305_final,

  	.descsize	= sizeof(struct poly1305_desc_ctx),
  	.base		= {
  		.cra_name		= "poly1305",
  		.cra_driver_name	= "poly1305-generic",
  		.cra_priority		= 100,

  		.cra_blocksize		= POLY1305_BLOCK_SIZE,

  		.cra_module		= THIS_MODULE,
  	},
  };
  
  static int __init poly1305_mod_init(void)
  {
  	return crypto_register_shash(&poly1305_alg);
  }
  
  static void __exit poly1305_mod_exit(void)
  {
  	crypto_unregister_shash(&poly1305_alg);
  }

  subsys_initcall(poly1305_mod_init);

  module_exit(poly1305_mod_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
  MODULE_DESCRIPTION("Poly1305 authenticator");
  MODULE_ALIAS_CRYPTO("poly1305");
  MODULE_ALIAS_CRYPTO("poly1305-generic");