/*
 * Cryptographic API.
 *
 * SHA1 Secure Hash Algorithm.
 *
 * Derived from cryptoapi implementation, adapted for in-place
 * scatterlist interface.
 *
 * Copyright (c) Alan Smithee.
 * Copyright (c) Andrew McDonald <andrew@mcdonald.org.uk>
 * Copyright (c) Jean-Francois Dive <jef@linuxbe.org>
 *
 * 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/internal/hash.h>
#include <linux/init.h>
#include <linux/cryptohash.h>
#include <linux/types.h>
#include <crypto/sha.h>
#include <asm/byteorder.h>

static int sha1_init(struct shash_desc* desc) {
  struct sha1_state* sctx = shash_desc_ctx(desc);

  *sctx = (struct sha1_state){
      .state = {SHA1_H0, SHA1_H1, SHA1_H2, SHA1_H3, SHA1_H4},
  };

  return 0;
}

static int sha1_update(struct shash_desc* desc,
                       const u8* data,
                       unsigned int len) {
  struct sha1_state* sctx = shash_desc_ctx(desc);
  unsigned int partial, done;
  const u8* src;

  partial = sctx->count & 0x3f;
  sctx->count += len;
  done = 0;
  src = data;

  if ((partial + len) > 63) {
    u32 temp[SHA_WORKSPACE_WORDS];

    if (partial) {
      done = -partial;
      memcpy(sctx->buffer + partial, data, done + 64);
      src = sctx->buffer;
    }

    do {
      sha_transform(sctx->state, src, temp);
      done += 64;
      src = data + done;
    } while (done + 63 < len);

    memset(temp, 0, sizeof(temp));
    partial = 0;
  }
  memcpy(sctx->buffer + partial, src, len - done);

  return 0;
}

/* Add padding and return the message digest. */
static int sha1_final(struct shash_desc* desc, u8* out) {
  struct sha1_state* sctx = shash_desc_ctx(desc);
  __be32* dst = (__be32*)out;
  u32 i, index, padlen;
  __be64 bits;
  static const u8 padding[64] = {
      0x80,
  };

  bits = __cpu_to_be64(sctx->count << 3);

  /* Pad out to 56 mod 64 */
  index = sctx->count & 0x3f;
  padlen = (index < 56) ? (56 - index) : ((64 + 56) - index);
  sha1_update(desc, padding, padlen);

  /* Append length */
  sha1_update(desc, (const u8*)&bits, sizeof(bits));

  /* Store state in digest */
  for (i = 0; i < 5; i++)
    dst[i] = __cpu_to_be32(sctx->state[i]);

  /* Wipe context */
  memset(sctx, 0, sizeof *sctx);

  return 0;
}

static int sha1_export(struct shash_desc* desc, void* out) {
  struct sha1_state* sctx = shash_desc_ctx(desc);

  memcpy(out, sctx, sizeof(*sctx));
  return 0;
}

static int sha1_import(struct shash_desc* desc, const void* in) {
  struct sha1_state* sctx = shash_desc_ctx(desc);

  memcpy(sctx, in, sizeof(*sctx));
  return 0;
}

static struct shash_alg alg = {.digestsize = SHA1_DIGEST_SIZE,
                               .init = sha1_init,
                               .update = sha1_update,
                               .final = sha1_final,
                               .export = sha1_export,
                               .import = sha1_import,
                               .descsize = sizeof(struct sha1_state),
                               .statesize = sizeof(struct sha1_state),
                               .base = {
                                   .cra_name = "sha1",
                                   .cra_driver_name = "sha1-generic",
                                   .cra_flags = CRYPTO_ALG_TYPE_SHASH,
                                   .cra_blocksize = SHA1_BLOCK_SIZE,
                                   .cra_module = NULL,
                               }};

static int __init sha1_generic_mod_init(void) {
  return crypto_register_shash(&alg);
}

static void __exit sha1_generic_mod_fini(void) {
  crypto_unregister_shash(&alg);
}

module_init(sha1_generic_mod_init);
module_exit(sha1_generic_mod_fini);