/* 
   * Cryptographic API.
   *
   * MD5 Message Digest Algorithm (RFC1321).
   *
   * Derived from cryptoapi implementation, originally based on the
   * public domain implementation written by Colin Plumb in 1993.
   *
   * Copyright (c) Cryptoapi developers.
   * Copyright (c) 2002 James Morris <jmorris@intercode.com.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 <linux/init.h>
  #include <linux/module.h>
  #include <linux/string.h>
  #include <linux/crypto.h>

  #include <linux/types.h>

  #include <asm/byteorder.h>
  
  #define MD5_DIGEST_SIZE		16
  #define MD5_HMAC_BLOCK_SIZE	64
  #define MD5_BLOCK_WORDS		16
  #define MD5_HASH_WORDS		4
  
  #define F1(x, y, z)	(z ^ (x & (y ^ z)))
  #define F2(x, y, z)	F1(z, x, y)
  #define F3(x, y, z)	(x ^ y ^ z)
  #define F4(x, y, z)	(y ^ (x | ~z))
  
  #define MD5STEP(f, w, x, y, z, in, s) \
  	(w += f(x, y, z) + in, w = (w<<s | w>>(32-s)) + x)
  
  struct md5_ctx {
  	u32 hash[MD5_HASH_WORDS];
  	u32 block[MD5_BLOCK_WORDS];
  	u64 byte_count;
  };
  
  static void md5_transform(u32 *hash, u32 const *in)
  {
  	u32 a, b, c, d;
  
  	a = hash[0];
  	b = hash[1];
  	c = hash[2];
  	d = hash[3];
  
  	MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
  	MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
  	MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
  	MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
  	MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
  	MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
  	MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
  	MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
  	MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
  	MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
  	MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
  	MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
  	MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
  	MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
  	MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
  	MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);
  
  	MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
  	MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
  	MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
  	MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
  	MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
  	MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
  	MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
  	MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
  	MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
  	MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
  	MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
  	MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
  	MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
  	MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
  	MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
  	MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);
  
  	MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
  	MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
  	MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
  	MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
  	MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
  	MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
  	MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
  	MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
  	MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
  	MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
  	MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
  	MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
  	MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
  	MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
  	MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
  	MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);
  
  	MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
  	MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
  	MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
  	MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
  	MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
  	MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
  	MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
  	MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
  	MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
  	MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
  	MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
  	MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
  	MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
  	MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
  	MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
  	MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);
  
  	hash[0] += a;
  	hash[1] += b;
  	hash[2] += c;
  	hash[3] += d;
  }
  
  /* XXX: this stuff can be optimized */
  static inline void le32_to_cpu_array(u32 *buf, unsigned int words)
  {
  	while (words--) {
  		__le32_to_cpus(buf);
  		buf++;
  	}
  }
  
  static inline void cpu_to_le32_array(u32 *buf, unsigned int words)
  {
  	while (words--) {
  		__cpu_to_le32s(buf);
  		buf++;
  	}
  }
  
  static inline void md5_transform_helper(struct md5_ctx *ctx)
  {
  	le32_to_cpu_array(ctx->block, sizeof(ctx->block) / sizeof(u32));
  	md5_transform(ctx->hash, ctx->block);
  }

  static void md5_init(struct crypto_tfm *tfm)

  {

  	struct md5_ctx *mctx = crypto_tfm_ctx(tfm);

  
  	mctx->hash[0] = 0x67452301;
  	mctx->hash[1] = 0xefcdab89;
  	mctx->hash[2] = 0x98badcfe;
  	mctx->hash[3] = 0x10325476;
  	mctx->byte_count = 0;
  }

  static void md5_update(struct crypto_tfm *tfm, const u8 *data, unsigned int len)

  {

  	struct md5_ctx *mctx = crypto_tfm_ctx(tfm);

  	const u32 avail = sizeof(mctx->block) - (mctx->byte_count & 0x3f);
  
  	mctx->byte_count += len;
  
  	if (avail > len) {
  		memcpy((char *)mctx->block + (sizeof(mctx->block) - avail),
  		       data, len);
  		return;
  	}
  
  	memcpy((char *)mctx->block + (sizeof(mctx->block) - avail),
  	       data, avail);
  
  	md5_transform_helper(mctx);
  	data += avail;
  	len -= avail;
  
  	while (len >= sizeof(mctx->block)) {
  		memcpy(mctx->block, data, sizeof(mctx->block));
  		md5_transform_helper(mctx);
  		data += sizeof(mctx->block);
  		len -= sizeof(mctx->block);
  	}
  
  	memcpy(mctx->block, data, len);
  }

  static void md5_final(struct crypto_tfm *tfm, u8 *out)

  {

  	struct md5_ctx *mctx = crypto_tfm_ctx(tfm);

  	const unsigned int offset = mctx->byte_count & 0x3f;
  	char *p = (char *)mctx->block + offset;
  	int padding = 56 - (offset + 1);
  
  	*p++ = 0x80;
  	if (padding < 0) {
  		memset(p, 0x00, padding + sizeof (u64));
  		md5_transform_helper(mctx);
  		p = (char *)mctx->block;
  		padding = 56;
  	}
  
  	memset(p, 0, padding);
  	mctx->block[14] = mctx->byte_count << 3;
  	mctx->block[15] = mctx->byte_count >> 29;
  	le32_to_cpu_array(mctx->block, (sizeof(mctx->block) -
  	                  sizeof(u64)) / sizeof(u32));
  	md5_transform(mctx->hash, mctx->block);
  	cpu_to_le32_array(mctx->hash, sizeof(mctx->hash) / sizeof(u32));
  	memcpy(out, mctx->hash, sizeof(mctx->hash));
  	memset(mctx, 0, sizeof(*mctx));
  }
  
  static struct crypto_alg alg = {
  	.cra_name	=	"md5",
  	.cra_flags	=	CRYPTO_ALG_TYPE_DIGEST,
  	.cra_blocksize	=	MD5_HMAC_BLOCK_SIZE,
  	.cra_ctxsize	=	sizeof(struct md5_ctx),
  	.cra_module	=	THIS_MODULE,
  	.cra_list	=	LIST_HEAD_INIT(alg.cra_list),
  	.cra_u		=	{ .digest = {
  	.dia_digestsize	=	MD5_DIGEST_SIZE,
  	.dia_init   	= 	md5_init,
  	.dia_update 	=	md5_update,
  	.dia_final  	=	md5_final } }
  };

  static int __init md5_mod_init(void)

  {
  	return crypto_register_alg(&alg);
  }

  static void __exit md5_mod_fini(void)

  {
  	crypto_unregister_alg(&alg);
  }

  module_init(md5_mod_init);
  module_exit(md5_mod_fini);

  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("MD5 Message Digest Algorithm");