/*

   * Cryptographic API.
   *
   * CRC32C chksum
   *

   *@Article{castagnoli-crc,
   * author =       { Guy Castagnoli and Stefan Braeuer and Martin Herrman},
   * title =        {{Optimization of Cyclic Redundancy-Check Codes with 24
   *                 and 32 Parity Bits}},
   * journal =      IEEE Transactions on Communication,
   * year =         {1993},
   * volume =       {41},
   * number =       {6},
   * pages =        {},
   * month =        {June},
   *}
   * Used by the iSCSI driver, possibly others, and derived from the
   * the iscsi-crc.c module of the linux-iscsi driver at
   * http://linux-iscsi.sourceforge.net.

   *

   * Following the example of lib/crc32, this function is intended to be
   * flexible and useful for all users.  Modules that currently have their
   * own crc32c, but hopefully may be able to use this one are:
   *  net/sctp (please add all your doco to here if you change to
   *            use this one!)
   *  <endoflist>
   *
   * Copyright (c) 2004 Cisco Systems, Inc.

   * Copyright (c) 2008 Herbert Xu <herbert@gondor.apana.org.au>
   *

   * 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/module.h>
  #include <linux/string.h>

  #include <linux/kernel.h>

  #define CHKSUM_BLOCK_SIZE	1

  #define CHKSUM_DIGEST_SIZE	4
  
  struct chksum_ctx {

  	u32 key;

  };

  struct chksum_desc_ctx {
  	u32 crc;
  };

  /*

   * This is the CRC-32C table
   * Generated with:
   * width = 32 bits
   * poly = 0x1EDC6F41
   * reflect input bytes = true
   * reflect output bytes = true
   */
  
  static const u32 crc32c_table[256] = {
  	0x00000000L, 0xF26B8303L, 0xE13B70F7L, 0x1350F3F4L,
  	0xC79A971FL, 0x35F1141CL, 0x26A1E7E8L, 0xD4CA64EBL,
  	0x8AD958CFL, 0x78B2DBCCL, 0x6BE22838L, 0x9989AB3BL,
  	0x4D43CFD0L, 0xBF284CD3L, 0xAC78BF27L, 0x5E133C24L,
  	0x105EC76FL, 0xE235446CL, 0xF165B798L, 0x030E349BL,
  	0xD7C45070L, 0x25AFD373L, 0x36FF2087L, 0xC494A384L,
  	0x9A879FA0L, 0x68EC1CA3L, 0x7BBCEF57L, 0x89D76C54L,
  	0x5D1D08BFL, 0xAF768BBCL, 0xBC267848L, 0x4E4DFB4BL,
  	0x20BD8EDEL, 0xD2D60DDDL, 0xC186FE29L, 0x33ED7D2AL,
  	0xE72719C1L, 0x154C9AC2L, 0x061C6936L, 0xF477EA35L,
  	0xAA64D611L, 0x580F5512L, 0x4B5FA6E6L, 0xB93425E5L,
  	0x6DFE410EL, 0x9F95C20DL, 0x8CC531F9L, 0x7EAEB2FAL,
  	0x30E349B1L, 0xC288CAB2L, 0xD1D83946L, 0x23B3BA45L,
  	0xF779DEAEL, 0x05125DADL, 0x1642AE59L, 0xE4292D5AL,
  	0xBA3A117EL, 0x4851927DL, 0x5B016189L, 0xA96AE28AL,
  	0x7DA08661L, 0x8FCB0562L, 0x9C9BF696L, 0x6EF07595L,
  	0x417B1DBCL, 0xB3109EBFL, 0xA0406D4BL, 0x522BEE48L,
  	0x86E18AA3L, 0x748A09A0L, 0x67DAFA54L, 0x95B17957L,
  	0xCBA24573L, 0x39C9C670L, 0x2A993584L, 0xD8F2B687L,
  	0x0C38D26CL, 0xFE53516FL, 0xED03A29BL, 0x1F682198L,
  	0x5125DAD3L, 0xA34E59D0L, 0xB01EAA24L, 0x42752927L,
  	0x96BF4DCCL, 0x64D4CECFL, 0x77843D3BL, 0x85EFBE38L,
  	0xDBFC821CL, 0x2997011FL, 0x3AC7F2EBL, 0xC8AC71E8L,
  	0x1C661503L, 0xEE0D9600L, 0xFD5D65F4L, 0x0F36E6F7L,
  	0x61C69362L, 0x93AD1061L, 0x80FDE395L, 0x72966096L,
  	0xA65C047DL, 0x5437877EL, 0x4767748AL, 0xB50CF789L,
  	0xEB1FCBADL, 0x197448AEL, 0x0A24BB5AL, 0xF84F3859L,
  	0x2C855CB2L, 0xDEEEDFB1L, 0xCDBE2C45L, 0x3FD5AF46L,
  	0x7198540DL, 0x83F3D70EL, 0x90A324FAL, 0x62C8A7F9L,
  	0xB602C312L, 0x44694011L, 0x5739B3E5L, 0xA55230E6L,
  	0xFB410CC2L, 0x092A8FC1L, 0x1A7A7C35L, 0xE811FF36L,
  	0x3CDB9BDDL, 0xCEB018DEL, 0xDDE0EB2AL, 0x2F8B6829L,
  	0x82F63B78L, 0x709DB87BL, 0x63CD4B8FL, 0x91A6C88CL,
  	0x456CAC67L, 0xB7072F64L, 0xA457DC90L, 0x563C5F93L,
  	0x082F63B7L, 0xFA44E0B4L, 0xE9141340L, 0x1B7F9043L,
  	0xCFB5F4A8L, 0x3DDE77ABL, 0x2E8E845FL, 0xDCE5075CL,
  	0x92A8FC17L, 0x60C37F14L, 0x73938CE0L, 0x81F80FE3L,
  	0x55326B08L, 0xA759E80BL, 0xB4091BFFL, 0x466298FCL,
  	0x1871A4D8L, 0xEA1A27DBL, 0xF94AD42FL, 0x0B21572CL,
  	0xDFEB33C7L, 0x2D80B0C4L, 0x3ED04330L, 0xCCBBC033L,
  	0xA24BB5A6L, 0x502036A5L, 0x4370C551L, 0xB11B4652L,
  	0x65D122B9L, 0x97BAA1BAL, 0x84EA524EL, 0x7681D14DL,
  	0x2892ED69L, 0xDAF96E6AL, 0xC9A99D9EL, 0x3BC21E9DL,
  	0xEF087A76L, 0x1D63F975L, 0x0E330A81L, 0xFC588982L,
  	0xB21572C9L, 0x407EF1CAL, 0x532E023EL, 0xA145813DL,
  	0x758FE5D6L, 0x87E466D5L, 0x94B49521L, 0x66DF1622L,
  	0x38CC2A06L, 0xCAA7A905L, 0xD9F75AF1L, 0x2B9CD9F2L,
  	0xFF56BD19L, 0x0D3D3E1AL, 0x1E6DCDEEL, 0xEC064EEDL,
  	0xC38D26C4L, 0x31E6A5C7L, 0x22B65633L, 0xD0DDD530L,
  	0x0417B1DBL, 0xF67C32D8L, 0xE52CC12CL, 0x1747422FL,
  	0x49547E0BL, 0xBB3FFD08L, 0xA86F0EFCL, 0x5A048DFFL,
  	0x8ECEE914L, 0x7CA56A17L, 0x6FF599E3L, 0x9D9E1AE0L,
  	0xD3D3E1ABL, 0x21B862A8L, 0x32E8915CL, 0xC083125FL,
  	0x144976B4L, 0xE622F5B7L, 0xF5720643L, 0x07198540L,
  	0x590AB964L, 0xAB613A67L, 0xB831C993L, 0x4A5A4A90L,
  	0x9E902E7BL, 0x6CFBAD78L, 0x7FAB5E8CL, 0x8DC0DD8FL,
  	0xE330A81AL, 0x115B2B19L, 0x020BD8EDL, 0xF0605BEEL,
  	0x24AA3F05L, 0xD6C1BC06L, 0xC5914FF2L, 0x37FACCF1L,
  	0x69E9F0D5L, 0x9B8273D6L, 0x88D28022L, 0x7AB90321L,
  	0xAE7367CAL, 0x5C18E4C9L, 0x4F48173DL, 0xBD23943EL,
  	0xF36E6F75L, 0x0105EC76L, 0x12551F82L, 0xE03E9C81L,
  	0x34F4F86AL, 0xC69F7B69L, 0xD5CF889DL, 0x27A40B9EL,
  	0x79B737BAL, 0x8BDCB4B9L, 0x988C474DL, 0x6AE7C44EL,
  	0xBE2DA0A5L, 0x4C4623A6L, 0x5F16D052L, 0xAD7D5351L
  };
  
  /*
   * Steps through buffer one byte at at time, calculates reflected
   * crc using table.
   */
  
  static u32 crc32c(u32 crc, const u8 *data, unsigned int length)
  {
  	while (length--)
  		crc = crc32c_table[(crc ^ *data++) & 0xFFL] ^ (crc >> 8);
  
  	return crc;
  }
  
  /*

   * Steps through buffer one byte at at time, calculates reflected

   * crc using table.
   */

  static int chksum_init(struct shash_desc *desc)

  {

  	struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);
  	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
  
  	ctx->crc = mctx->key;

  	return 0;

  }
  
  /*
   * Setting the seed allows arbitrary accumulators and flexible XOR policy
   * If your algorithm starts with ~0, then XOR with ~0 before you set
   * the seed.
   */

  static int chksum_setkey(struct crypto_shash *tfm, const u8 *key,

  			 unsigned int keylen)

  {

  	struct chksum_ctx *mctx = crypto_shash_ctx(tfm);

  	if (keylen != sizeof(mctx->key)) {
  		crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);

  		return -EINVAL;
  	}

  	mctx->key = le32_to_cpu(*(__le32 *)key);

  	return 0;
  }

  static int chksum_update(struct shash_desc *desc, const u8 *data,
  			 unsigned int length)

  {

  	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);

  	ctx->crc = crc32c(ctx->crc, data, length);

  	return 0;

  }

  static int chksum_final(struct shash_desc *desc, u8 *out)

  {

  	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);

  	*(__le32 *)out = ~cpu_to_le32p(&ctx->crc);

  	return 0;
  }

  static int __chksum_finup(u32 *crcp, const u8 *data, unsigned int len, u8 *out)

  {

  	*(__le32 *)out = ~cpu_to_le32(crc32c(*crcp, data, len));

  	return 0;
  }

  static int chksum_finup(struct shash_desc *desc, const u8 *data,
  			unsigned int len, u8 *out)

  {

  	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);

  	return __chksum_finup(&ctx->crc, data, len, out);

  }

  static int chksum_digest(struct shash_desc *desc, const u8 *data,
  			 unsigned int length, u8 *out)

  {

  	struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);

  	return __chksum_finup(&mctx->key, data, length, out);

  }
  
  static int crc32c_cra_init(struct crypto_tfm *tfm)
  {

  	struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);

  	mctx->key = ~0;

  	return 0;
  }

  static struct shash_alg alg = {
  	.digestsize		=	CHKSUM_DIGEST_SIZE,
  	.setkey			=	chksum_setkey,

  	.init		=	chksum_init,
  	.update		=	chksum_update,
  	.final		=	chksum_final,
  	.finup		=	chksum_finup,
  	.digest		=	chksum_digest,

  	.descsize		=	sizeof(struct chksum_desc_ctx),
  	.base			=	{
  		.cra_name		=	"crc32c",
  		.cra_driver_name	=	"crc32c-generic",
  		.cra_priority		=	100,
  		.cra_blocksize		=	CHKSUM_BLOCK_SIZE,
  		.cra_alignmask		=	3,
  		.cra_ctxsize		=	sizeof(struct chksum_ctx),
  		.cra_module		=	THIS_MODULE,
  		.cra_init		=	crc32c_cra_init,

  	}
  };

  static int __init crc32c_mod_init(void)

  {

  	return crypto_register_shash(&alg);

  }

  static void __exit crc32c_mod_fini(void)

  {

  	crypto_unregister_shash(&alg);

  }

  module_init(crc32c_mod_init);
  module_exit(crc32c_mod_fini);

  
  MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
  MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
  MODULE_LICENSE("GPL");