/*
   * Modified to interface to the Linux kernel
   * Copyright (c) 2009, Intel Corporation.
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms and conditions of the GNU General Public License,
   * version 2, as published by the Free Software Foundation.
   *
   * This program is distributed in the hope it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
   * more details.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
   * Place - Suite 330, Boston, MA 02111-1307 USA.
   */
  
  /* --------------------------------------------------------------------------
   * VMAC and VHASH Implementation by Ted Krovetz (tdk@acm.org) and Wei Dai.
   * This implementation is herby placed in the public domain.
   * The authors offers no warranty. Use at your own risk.
   * Please send bug reports to the authors.
   * Last modified: 17 APR 08, 1700 PDT
   * ----------------------------------------------------------------------- */
  
  #include <linux/init.h>
  #include <linux/types.h>
  #include <linux/crypto.h>

  #include <linux/module.h>

  #include <linux/scatterlist.h>
  #include <asm/byteorder.h>
  #include <crypto/scatterwalk.h>
  #include <crypto/vmac.h>
  #include <crypto/internal/hash.h>
  
  /*
   * Constants and masks
   */
  #define UINT64_C(x) x##ULL

  static const u64 p64   = UINT64_C(0xfffffffffffffeff);	/* 2^64 - 257 prime  */
  static const u64 m62   = UINT64_C(0x3fffffffffffffff);	/* 62-bit mask       */
  static const u64 m63   = UINT64_C(0x7fffffffffffffff);	/* 63-bit mask       */
  static const u64 m64   = UINT64_C(0xffffffffffffffff);	/* 64-bit mask       */
  static const u64 mpoly = UINT64_C(0x1fffffff1fffffff);	/* Poly key mask     */

  #define pe64_to_cpup le64_to_cpup		/* Prefer little endian */

  #ifdef __LITTLE_ENDIAN
  #define INDEX_HIGH 1
  #define INDEX_LOW 0
  #else
  #define INDEX_HIGH 0
  #define INDEX_LOW 1
  #endif
  
  /*
   * The following routines are used in this implementation. They are
   * written via macros to simulate zero-overhead call-by-reference.
   *
   * MUL64: 64x64->128-bit multiplication
   * PMUL64: assumes top bits cleared on inputs
   * ADD128: 128x128->128-bit addition
   */
  
  #define ADD128(rh, rl, ih, il)						\
  	do {								\
  		u64 _il = (il);						\
  		(rl) += (_il);						\
  		if ((rl) < (_il))					\
  			(rh)++;						\
  		(rh) += (ih);						\
  	} while (0)
  
  #define MUL32(i1, i2)	((u64)(u32)(i1)*(u32)(i2))
  
  #define PMUL64(rh, rl, i1, i2)	/* Assumes m doesn't overflow */	\
  	do {								\
  		u64 _i1 = (i1), _i2 = (i2);				\
  		u64 m = MUL32(_i1, _i2>>32) + MUL32(_i1>>32, _i2);	\
  		rh = MUL32(_i1>>32, _i2>>32);				\
  		rl = MUL32(_i1, _i2);					\
  		ADD128(rh, rl, (m >> 32), (m << 32));			\
  	} while (0)
  
  #define MUL64(rh, rl, i1, i2)						\
  	do {								\
  		u64 _i1 = (i1), _i2 = (i2);				\
  		u64 m1 = MUL32(_i1, _i2>>32);				\
  		u64 m2 = MUL32(_i1>>32, _i2);				\
  		rh = MUL32(_i1>>32, _i2>>32);				\
  		rl = MUL32(_i1, _i2);					\
  		ADD128(rh, rl, (m1 >> 32), (m1 << 32));			\
  		ADD128(rh, rl, (m2 >> 32), (m2 << 32));			\
  	} while (0)
  
  /*
   * For highest performance the L1 NH and L2 polynomial hashes should be

   * carefully implemented to take advantage of one's target architecture.

   * Here these two hash functions are defined multiple time; once for
   * 64-bit architectures, once for 32-bit SSE2 architectures, and once
   * for the rest (32-bit) architectures.
   * For each, nh_16 *must* be defined (works on multiples of 16 bytes).
   * Optionally, nh_vmac_nhbytes can be defined (for multiples of
   * VMAC_NHBYTES), and nh_16_2 and nh_vmac_nhbytes_2 (versions that do two
   * NH computations at once).
   */
  
  #ifdef CONFIG_64BIT
  
  #define nh_16(mp, kp, nw, rh, rl)					\
  	do {								\
  		int i; u64 th, tl;					\
  		rh = rl = 0;						\
  		for (i = 0; i < nw; i += 2) {				\

  			MUL64(th, tl, pe64_to_cpup((mp)+i)+(kp)[i],	\
  				pe64_to_cpup((mp)+i+1)+(kp)[i+1]);	\

  			ADD128(rh, rl, th, tl);				\
  		}							\
  	} while (0)
  
  #define nh_16_2(mp, kp, nw, rh, rl, rh1, rl1)				\
  	do {								\
  		int i; u64 th, tl;					\
  		rh1 = rl1 = rh = rl = 0;				\
  		for (i = 0; i < nw; i += 2) {				\

  			MUL64(th, tl, pe64_to_cpup((mp)+i)+(kp)[i],	\
  				pe64_to_cpup((mp)+i+1)+(kp)[i+1]);	\

  			ADD128(rh, rl, th, tl);				\

  			MUL64(th, tl, pe64_to_cpup((mp)+i)+(kp)[i+2],	\
  				pe64_to_cpup((mp)+i+1)+(kp)[i+3]);	\

  			ADD128(rh1, rl1, th, tl);			\
  		}							\
  	} while (0)
  
  #if (VMAC_NHBYTES >= 64) /* These versions do 64-bytes of message at a time */
  #define nh_vmac_nhbytes(mp, kp, nw, rh, rl)				\
  	do {								\
  		int i; u64 th, tl;					\
  		rh = rl = 0;						\
  		for (i = 0; i < nw; i += 8) {				\

  			MUL64(th, tl, pe64_to_cpup((mp)+i)+(kp)[i],	\
  				pe64_to_cpup((mp)+i+1)+(kp)[i+1]);	\

  			ADD128(rh, rl, th, tl);				\

  			MUL64(th, tl, pe64_to_cpup((mp)+i+2)+(kp)[i+2],	\
  				pe64_to_cpup((mp)+i+3)+(kp)[i+3]);	\

  			ADD128(rh, rl, th, tl);				\

  			MUL64(th, tl, pe64_to_cpup((mp)+i+4)+(kp)[i+4],	\
  				pe64_to_cpup((mp)+i+5)+(kp)[i+5]);	\

  			ADD128(rh, rl, th, tl);				\

  			MUL64(th, tl, pe64_to_cpup((mp)+i+6)+(kp)[i+6],	\
  				pe64_to_cpup((mp)+i+7)+(kp)[i+7]);	\

  			ADD128(rh, rl, th, tl);				\
  		}							\
  	} while (0)
  
  #define nh_vmac_nhbytes_2(mp, kp, nw, rh, rl, rh1, rl1)			\
  	do {								\
  		int i; u64 th, tl;					\
  		rh1 = rl1 = rh = rl = 0;				\
  		for (i = 0; i < nw; i += 8) {				\

  			MUL64(th, tl, pe64_to_cpup((mp)+i)+(kp)[i],	\
  				pe64_to_cpup((mp)+i+1)+(kp)[i+1]);	\

  			ADD128(rh, rl, th, tl);				\

  			MUL64(th, tl, pe64_to_cpup((mp)+i)+(kp)[i+2],	\
  				pe64_to_cpup((mp)+i+1)+(kp)[i+3]);	\

  			ADD128(rh1, rl1, th, tl);			\

  			MUL64(th, tl, pe64_to_cpup((mp)+i+2)+(kp)[i+2],	\
  				pe64_to_cpup((mp)+i+3)+(kp)[i+3]);	\

  			ADD128(rh, rl, th, tl);				\

  			MUL64(th, tl, pe64_to_cpup((mp)+i+2)+(kp)[i+4],	\
  				pe64_to_cpup((mp)+i+3)+(kp)[i+5]);	\

  			ADD128(rh1, rl1, th, tl);			\

  			MUL64(th, tl, pe64_to_cpup((mp)+i+4)+(kp)[i+4],	\
  				pe64_to_cpup((mp)+i+5)+(kp)[i+5]);	\

  			ADD128(rh, rl, th, tl);				\

  			MUL64(th, tl, pe64_to_cpup((mp)+i+4)+(kp)[i+6],	\
  				pe64_to_cpup((mp)+i+5)+(kp)[i+7]);	\

  			ADD128(rh1, rl1, th, tl);			\

  			MUL64(th, tl, pe64_to_cpup((mp)+i+6)+(kp)[i+6],	\
  				pe64_to_cpup((mp)+i+7)+(kp)[i+7]);	\

  			ADD128(rh, rl, th, tl);				\

  			MUL64(th, tl, pe64_to_cpup((mp)+i+6)+(kp)[i+8],	\
  				pe64_to_cpup((mp)+i+7)+(kp)[i+9]);	\

  			ADD128(rh1, rl1, th, tl);			\
  		}							\
  	} while (0)
  #endif
  
  #define poly_step(ah, al, kh, kl, mh, ml)				\
  	do {								\
  		u64 t1h, t1l, t2h, t2l, t3h, t3l, z = 0;		\
  		/* compute ab*cd, put bd into result registers */	\
  		PMUL64(t3h, t3l, al, kh);				\
  		PMUL64(t2h, t2l, ah, kl);				\
  		PMUL64(t1h, t1l, ah, 2*kh);				\
  		PMUL64(ah, al, al, kl);					\
  		/* add 2 * ac to result */				\
  		ADD128(ah, al, t1h, t1l);				\
  		/* add together ad + bc */				\
  		ADD128(t2h, t2l, t3h, t3l);				\
  		/* now (ah,al), (t2l,2*t2h) need summing */		\
  		/* first add the high registers, carrying into t2h */	\
  		ADD128(t2h, ah, z, t2l);				\
  		/* double t2h and add top bit of ah */			\
  		t2h = 2 * t2h + (ah >> 63);				\
  		ah &= m63;						\
  		/* now add the low registers */				\
  		ADD128(ah, al, mh, ml);					\
  		ADD128(ah, al, z, t2h);					\
  	} while (0)
  
  #else /* ! CONFIG_64BIT */
  
  #ifndef nh_16
  #define nh_16(mp, kp, nw, rh, rl)					\
  	do {								\
  		u64 t1, t2, m1, m2, t;					\
  		int i;							\
  		rh = rl = t = 0;					\
  		for (i = 0; i < nw; i += 2)  {				\

  			t1 = pe64_to_cpup(mp+i) + kp[i];		\
  			t2 = pe64_to_cpup(mp+i+1) + kp[i+1];		\

  			m2 = MUL32(t1 >> 32, t2);			\
  			m1 = MUL32(t1, t2 >> 32);			\
  			ADD128(rh, rl, MUL32(t1 >> 32, t2 >> 32),	\
  				MUL32(t1, t2));				\
  			rh += (u64)(u32)(m1 >> 32)			\
  				+ (u32)(m2 >> 32);			\
  			t += (u64)(u32)m1 + (u32)m2;			\
  		}							\
  		ADD128(rh, rl, (t >> 32), (t << 32));			\
  	} while (0)
  #endif
  
  static void poly_step_func(u64 *ahi, u64 *alo,
  			const u64 *kh, const u64 *kl,
  			const u64 *mh, const u64 *ml)
  {
  #define a0 (*(((u32 *)alo)+INDEX_LOW))
  #define a1 (*(((u32 *)alo)+INDEX_HIGH))
  #define a2 (*(((u32 *)ahi)+INDEX_LOW))
  #define a3 (*(((u32 *)ahi)+INDEX_HIGH))
  #define k0 (*(((u32 *)kl)+INDEX_LOW))
  #define k1 (*(((u32 *)kl)+INDEX_HIGH))
  #define k2 (*(((u32 *)kh)+INDEX_LOW))
  #define k3 (*(((u32 *)kh)+INDEX_HIGH))
  
  	u64 p, q, t;
  	u32 t2;
  
  	p = MUL32(a3, k3);
  	p += p;
  	p += *(u64 *)mh;
  	p += MUL32(a0, k2);
  	p += MUL32(a1, k1);
  	p += MUL32(a2, k0);
  	t = (u32)(p);
  	p >>= 32;
  	p += MUL32(a0, k3);
  	p += MUL32(a1, k2);
  	p += MUL32(a2, k1);
  	p += MUL32(a3, k0);
  	t |= ((u64)((u32)p & 0x7fffffff)) << 32;
  	p >>= 31;
  	p += (u64)(((u32 *)ml)[INDEX_LOW]);
  	p += MUL32(a0, k0);
  	q =  MUL32(a1, k3);
  	q += MUL32(a2, k2);
  	q += MUL32(a3, k1);
  	q += q;
  	p += q;
  	t2 = (u32)(p);
  	p >>= 32;
  	p += (u64)(((u32 *)ml)[INDEX_HIGH]);
  	p += MUL32(a0, k1);
  	p += MUL32(a1, k0);
  	q =  MUL32(a2, k3);
  	q += MUL32(a3, k2);
  	q += q;
  	p += q;
  	*(u64 *)(alo) = (p << 32) | t2;
  	p >>= 32;
  	*(u64 *)(ahi) = p + t;
  
  #undef a0
  #undef a1
  #undef a2
  #undef a3
  #undef k0
  #undef k1
  #undef k2
  #undef k3
  }
  
  #define poly_step(ah, al, kh, kl, mh, ml)				\
  	poly_step_func(&(ah), &(al), &(kh), &(kl), &(mh), &(ml))
  
  #endif  /* end of specialized NH and poly definitions */
  
  /* At least nh_16 is defined. Defined others as needed here */
  #ifndef nh_16_2
  #define nh_16_2(mp, kp, nw, rh, rl, rh2, rl2)				\
  	do { 								\
  		nh_16(mp, kp, nw, rh, rl);				\
  		nh_16(mp, ((kp)+2), nw, rh2, rl2);			\
  	} while (0)
  #endif
  #ifndef nh_vmac_nhbytes
  #define nh_vmac_nhbytes(mp, kp, nw, rh, rl)				\
  	nh_16(mp, kp, nw, rh, rl)
  #endif
  #ifndef nh_vmac_nhbytes_2
  #define nh_vmac_nhbytes_2(mp, kp, nw, rh, rl, rh2, rl2)			\
  	do {								\
  		nh_vmac_nhbytes(mp, kp, nw, rh, rl);			\
  		nh_vmac_nhbytes(mp, ((kp)+2), nw, rh2, rl2);		\
  	} while (0)
  #endif
  
  static void vhash_abort(struct vmac_ctx *ctx)
  {
  	ctx->polytmp[0] = ctx->polykey[0] ;
  	ctx->polytmp[1] = ctx->polykey[1] ;
  	ctx->first_block_processed = 0;
  }

  static u64 l3hash(u64 p1, u64 p2, u64 k1, u64 k2, u64 len)

  {
  	u64 rh, rl, t, z = 0;
  
  	/* fully reduce (p1,p2)+(len,0) mod p127 */
  	t = p1 >> 63;
  	p1 &= m63;
  	ADD128(p1, p2, len, t);
  	/* At this point, (p1,p2) is at most 2^127+(len<<64) */
  	t = (p1 > m63) + ((p1 == m63) && (p2 == m64));
  	ADD128(p1, p2, z, t);
  	p1 &= m63;
  
  	/* compute (p1,p2)/(2^64-2^32) and (p1,p2)%(2^64-2^32) */
  	t = p1 + (p2 >> 32);
  	t += (t >> 32);
  	t += (u32)t > 0xfffffffeu;
  	p1 += (t >> 32);
  	p2 += (p1 << 32);
  
  	/* compute (p1+k1)%p64 and (p2+k2)%p64 */
  	p1 += k1;
  	p1 += (0 - (p1 < k1)) & 257;
  	p2 += k2;
  	p2 += (0 - (p2 < k2)) & 257;
  
  	/* compute (p1+k1)*(p2+k2)%p64 */
  	MUL64(rh, rl, p1, p2);
  	t = rh >> 56;
  	ADD128(t, rl, z, rh);
  	rh <<= 8;
  	ADD128(t, rl, z, rh);
  	t += t << 8;
  	rl += t;
  	rl += (0 - (rl < t)) & 257;
  	rl += (0 - (rl > p64-1)) & 257;
  	return rl;
  }
  
  static void vhash_update(const unsigned char *m,
  			unsigned int mbytes, /* Pos multiple of VMAC_NHBYTES */
  			struct vmac_ctx *ctx)
  {
  	u64 rh, rl, *mptr;
  	const u64 *kptr = (u64 *)ctx->nhkey;
  	int i;
  	u64 ch, cl;
  	u64 pkh = ctx->polykey[0];
  	u64 pkl = ctx->polykey[1];

  	if (!mbytes)
  		return;
  
  	BUG_ON(mbytes % VMAC_NHBYTES);

  	mptr = (u64 *)m;
  	i = mbytes / VMAC_NHBYTES;  /* Must be non-zero */
  
  	ch = ctx->polytmp[0];
  	cl = ctx->polytmp[1];
  
  	if (!ctx->first_block_processed) {
  		ctx->first_block_processed = 1;
  		nh_vmac_nhbytes(mptr, kptr, VMAC_NHBYTES/8, rh, rl);
  		rh &= m62;
  		ADD128(ch, cl, rh, rl);
  		mptr += (VMAC_NHBYTES/sizeof(u64));
  		i--;
  	}
  
  	while (i--) {
  		nh_vmac_nhbytes(mptr, kptr, VMAC_NHBYTES/8, rh, rl);
  		rh &= m62;
  		poly_step(ch, cl, pkh, pkl, rh, rl);
  		mptr += (VMAC_NHBYTES/sizeof(u64));
  	}
  
  	ctx->polytmp[0] = ch;
  	ctx->polytmp[1] = cl;
  }
  
  static u64 vhash(unsigned char m[], unsigned int mbytes,
  			u64 *tagl, struct vmac_ctx *ctx)
  {
  	u64 rh, rl, *mptr;
  	const u64 *kptr = (u64 *)ctx->nhkey;
  	int i, remaining;
  	u64 ch, cl;
  	u64 pkh = ctx->polykey[0];
  	u64 pkl = ctx->polykey[1];
  
  	mptr = (u64 *)m;
  	i = mbytes / VMAC_NHBYTES;
  	remaining = mbytes % VMAC_NHBYTES;
  
  	if (ctx->first_block_processed) {
  		ch = ctx->polytmp[0];
  		cl = ctx->polytmp[1];
  	} else if (i) {
  		nh_vmac_nhbytes(mptr, kptr, VMAC_NHBYTES/8, ch, cl);
  		ch &= m62;
  		ADD128(ch, cl, pkh, pkl);
  		mptr += (VMAC_NHBYTES/sizeof(u64));
  		i--;
  	} else if (remaining) {
  		nh_16(mptr, kptr, 2*((remaining+15)/16), ch, cl);
  		ch &= m62;
  		ADD128(ch, cl, pkh, pkl);
  		mptr += (VMAC_NHBYTES/sizeof(u64));
  		goto do_l3;
  	} else {/* Empty String */
  		ch = pkh; cl = pkl;
  		goto do_l3;
  	}
  
  	while (i--) {
  		nh_vmac_nhbytes(mptr, kptr, VMAC_NHBYTES/8, rh, rl);
  		rh &= m62;
  		poly_step(ch, cl, pkh, pkl, rh, rl);
  		mptr += (VMAC_NHBYTES/sizeof(u64));
  	}
  	if (remaining) {
  		nh_16(mptr, kptr, 2*((remaining+15)/16), rh, rl);
  		rh &= m62;
  		poly_step(ch, cl, pkh, pkl, rh, rl);
  	}
  
  do_l3:
  	vhash_abort(ctx);
  	remaining *= 8;
  	return l3hash(ch, cl, ctx->l3key[0], ctx->l3key[1], remaining);
  }
  
  static u64 vmac(unsigned char m[], unsigned int mbytes,

  			const unsigned char n[16], u64 *tagl,

  			struct vmac_ctx_t *ctx)
  {
  	u64 *in_n, *out_p;
  	u64 p, h;
  	int i;
  
  	in_n = ctx->__vmac_ctx.cached_nonce;
  	out_p = ctx->__vmac_ctx.cached_aes;
  
  	i = n[15] & 1;
  	if ((*(u64 *)(n+8) != in_n[1]) || (*(u64 *)(n) != in_n[0])) {
  		in_n[0] = *(u64 *)(n);
  		in_n[1] = *(u64 *)(n+8);
  		((unsigned char *)in_n)[15] &= 0xFE;
  		crypto_cipher_encrypt_one(ctx->child,
  			(unsigned char *)out_p, (unsigned char *)in_n);
  
  		((unsigned char *)in_n)[15] |= (unsigned char)(1-i);
  	}
  	p = be64_to_cpup(out_p + i);
  	h = vhash(m, mbytes, (u64 *)0, &ctx->__vmac_ctx);

  	return le64_to_cpu(p + h);

  }
  
  static int vmac_set_key(unsigned char user_key[], struct vmac_ctx_t *ctx)
  {
  	u64 in[2] = {0}, out[2];
  	unsigned i;
  	int err = 0;
  
  	err = crypto_cipher_setkey(ctx->child, user_key, VMAC_KEY_LEN);
  	if (err)
  		return err;
  
  	/* Fill nh key */
  	((unsigned char *)in)[0] = 0x80;
  	for (i = 0; i < sizeof(ctx->__vmac_ctx.nhkey)/8; i += 2) {
  		crypto_cipher_encrypt_one(ctx->child,
  			(unsigned char *)out, (unsigned char *)in);
  		ctx->__vmac_ctx.nhkey[i] = be64_to_cpup(out);
  		ctx->__vmac_ctx.nhkey[i+1] = be64_to_cpup(out+1);
  		((unsigned char *)in)[15] += 1;
  	}
  
  	/* Fill poly key */
  	((unsigned char *)in)[0] = 0xC0;
  	in[1] = 0;
  	for (i = 0; i < sizeof(ctx->__vmac_ctx.polykey)/8; i += 2) {
  		crypto_cipher_encrypt_one(ctx->child,
  			(unsigned char *)out, (unsigned char *)in);
  		ctx->__vmac_ctx.polytmp[i] =
  			ctx->__vmac_ctx.polykey[i] =
  				be64_to_cpup(out) & mpoly;
  		ctx->__vmac_ctx.polytmp[i+1] =
  			ctx->__vmac_ctx.polykey[i+1] =
  				be64_to_cpup(out+1) & mpoly;
  		((unsigned char *)in)[15] += 1;
  	}
  
  	/* Fill ip key */
  	((unsigned char *)in)[0] = 0xE0;
  	in[1] = 0;
  	for (i = 0; i < sizeof(ctx->__vmac_ctx.l3key)/8; i += 2) {
  		do {
  			crypto_cipher_encrypt_one(ctx->child,
  				(unsigned char *)out, (unsigned char *)in);
  			ctx->__vmac_ctx.l3key[i] = be64_to_cpup(out);
  			ctx->__vmac_ctx.l3key[i+1] = be64_to_cpup(out+1);
  			((unsigned char *)in)[15] += 1;
  		} while (ctx->__vmac_ctx.l3key[i] >= p64
  			|| ctx->__vmac_ctx.l3key[i+1] >= p64);
  	}
  
  	/* Invalidate nonce/aes cache and reset other elements */
  	ctx->__vmac_ctx.cached_nonce[0] = (u64)-1; /* Ensure illegal nonce */
  	ctx->__vmac_ctx.cached_nonce[1] = (u64)0;  /* Ensure illegal nonce */
  	ctx->__vmac_ctx.first_block_processed = 0;
  
  	return err;
  }
  
  static int vmac_setkey(struct crypto_shash *parent,
  		const u8 *key, unsigned int keylen)
  {
  	struct vmac_ctx_t *ctx = crypto_shash_ctx(parent);
  
  	if (keylen != VMAC_KEY_LEN) {
  		crypto_shash_set_flags(parent, CRYPTO_TFM_RES_BAD_KEY_LEN);
  		return -EINVAL;
  	}
  
  	return vmac_set_key((u8 *)key, ctx);
  }
  
  static int vmac_init(struct shash_desc *pdesc)
  {

  	return 0;
  }
  
  static int vmac_update(struct shash_desc *pdesc, const u8 *p,
  		unsigned int len)
  {
  	struct crypto_shash *parent = pdesc->tfm;
  	struct vmac_ctx_t *ctx = crypto_shash_ctx(parent);

  	int expand;
  	int min;
  
  	expand = VMAC_NHBYTES - ctx->partial_size > 0 ?
  			VMAC_NHBYTES - ctx->partial_size : 0;
  
  	min = len < expand ? len : expand;
  
  	memcpy(ctx->partial + ctx->partial_size, p, min);
  	ctx->partial_size += min;
  
  	if (len < expand)
  		return 0;

  	vhash_update(ctx->partial, VMAC_NHBYTES, &ctx->__vmac_ctx);
  	ctx->partial_size = 0;
  
  	len -= expand;
  	p += expand;
  
  	if (len % VMAC_NHBYTES) {
  		memcpy(ctx->partial, p + len - (len % VMAC_NHBYTES),
  			len % VMAC_NHBYTES);
  		ctx->partial_size = len % VMAC_NHBYTES;
  	}
  
  	vhash_update(p, len - len % VMAC_NHBYTES, &ctx->__vmac_ctx);

  
  	return 0;
  }
  
  static int vmac_final(struct shash_desc *pdesc, u8 *out)
  {
  	struct crypto_shash *parent = pdesc->tfm;
  	struct vmac_ctx_t *ctx = crypto_shash_ctx(parent);
  	vmac_t mac;
  	u8 nonce[16] = {};

  	/* vmac() ends up accessing outside the array bounds that
  	 * we specify.  In appears to access up to the next 2-word
  	 * boundary.  We'll just be uber cautious and zero the
  	 * unwritten bytes in the buffer.
  	 */
  	if (ctx->partial_size) {
  		memset(ctx->partial + ctx->partial_size, 0,
  			VMAC_NHBYTES - ctx->partial_size);
  	}
  	mac = vmac(ctx->partial, ctx->partial_size, nonce, NULL, ctx);

  	memcpy(out, &mac, sizeof(vmac_t));
  	memset(&mac, 0, sizeof(vmac_t));
  	memset(&ctx->__vmac_ctx, 0, sizeof(struct vmac_ctx));

  	ctx->partial_size = 0;

  	return 0;
  }
  
  static int vmac_init_tfm(struct crypto_tfm *tfm)
  {
  	struct crypto_cipher *cipher;
  	struct crypto_instance *inst = (void *)tfm->__crt_alg;
  	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
  	struct vmac_ctx_t *ctx = crypto_tfm_ctx(tfm);
  
  	cipher = crypto_spawn_cipher(spawn);
  	if (IS_ERR(cipher))
  		return PTR_ERR(cipher);
  
  	ctx->child = cipher;
  	return 0;
  }
  
  static void vmac_exit_tfm(struct crypto_tfm *tfm)
  {
  	struct vmac_ctx_t *ctx = crypto_tfm_ctx(tfm);
  	crypto_free_cipher(ctx->child);
  }
  
  static int vmac_create(struct crypto_template *tmpl, struct rtattr **tb)
  {
  	struct shash_instance *inst;
  	struct crypto_alg *alg;
  	int err;
  
  	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);
  	if (err)
  		return err;
  
  	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
  			CRYPTO_ALG_TYPE_MASK);
  	if (IS_ERR(alg))
  		return PTR_ERR(alg);
  
  	inst = shash_alloc_instance("vmac", alg);
  	err = PTR_ERR(inst);
  	if (IS_ERR(inst))
  		goto out_put_alg;
  
  	err = crypto_init_spawn(shash_instance_ctx(inst), alg,
  			shash_crypto_instance(inst),
  			CRYPTO_ALG_TYPE_MASK);
  	if (err)
  		goto out_free_inst;
  
  	inst->alg.base.cra_priority = alg->cra_priority;
  	inst->alg.base.cra_blocksize = alg->cra_blocksize;
  	inst->alg.base.cra_alignmask = alg->cra_alignmask;
  
  	inst->alg.digestsize = sizeof(vmac_t);
  	inst->alg.base.cra_ctxsize = sizeof(struct vmac_ctx_t);
  	inst->alg.base.cra_init = vmac_init_tfm;
  	inst->alg.base.cra_exit = vmac_exit_tfm;
  
  	inst->alg.init = vmac_init;
  	inst->alg.update = vmac_update;
  	inst->alg.final = vmac_final;
  	inst->alg.setkey = vmac_setkey;
  
  	err = shash_register_instance(tmpl, inst);
  	if (err) {
  out_free_inst:
  		shash_free_instance(shash_crypto_instance(inst));
  	}
  
  out_put_alg:
  	crypto_mod_put(alg);
  	return err;
  }
  
  static struct crypto_template vmac_tmpl = {
  	.name = "vmac",
  	.create = vmac_create,
  	.free = shash_free_instance,
  	.module = THIS_MODULE,
  };
  
  static int __init vmac_module_init(void)
  {
  	return crypto_register_template(&vmac_tmpl);
  }
  
  static void __exit vmac_module_exit(void)
  {
  	crypto_unregister_template(&vmac_tmpl);
  }
  
  module_init(vmac_module_init);
  module_exit(vmac_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("VMAC hash algorithm");