crypto/gcm.c - kernel/msm - Gitiles

 /*
  * GCM: Galois/Counter Mode.
  *
  * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi>
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 as published
  * by the Free Software Foundation.
  */

 #include <crypto/algapi.h>
 #include <crypto/gf128mul.h>
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/slab.h>

 #include "scatterwalk.h"

 struct gcm_instance_ctx {
 	struct crypto_spawn ctr;
 };

 struct crypto_gcm_ctx {
 	struct crypto_ablkcipher *ctr;
 	struct gf128mul_4k *gf128;
 };

 struct crypto_gcm_ghash_ctx {
 	u32 bytes;
 	u32 flags;
 	struct gf128mul_4k *gf128;
 	u8 buffer[16];
 };

 struct crypto_gcm_req_priv_ctx {
 	u8 auth_tag[16];
 	u8 counter[16];
 	struct crypto_gcm_ghash_ctx ghash;
 };

 static void crypto_gcm_ghash_init(struct crypto_gcm_ghash_ctx *ctx, u32 flags,
 				  struct gf128mul_4k *gf128)
 {
 	ctx->bytes = 0;
 	ctx->flags = flags;
 	ctx->gf128 = gf128;
 	memset(ctx->buffer, 0, 16);
 }

 static void crypto_gcm_ghash_update(struct crypto_gcm_ghash_ctx *ctx,
 				    const u8 *src, unsigned int srclen)
 {
 	u8 *dst = ctx->buffer;

 	if (ctx->bytes) {
 		int n = min(srclen, ctx->bytes);
 		u8 *pos = dst + (16 - ctx->bytes);

 		ctx->bytes -= n;
 		srclen -= n;

 		while (n--)
 			*pos++ ^= *src++;

 		if (!ctx->bytes)
 			gf128mul_4k_lle((be128 *)dst, ctx->gf128);
 	}

 	while (srclen >= 16) {
 		crypto_xor(dst, src, 16);
 		gf128mul_4k_lle((be128 *)dst, ctx->gf128);
 		src += 16;
 		srclen -= 16;
 	}

 	if (srclen) {
 		ctx->bytes = 16 - srclen;
 		while (srclen--)
 			*dst++ ^= *src++;
 	}
 }

 static void crypto_gcm_ghash_update_sg(struct crypto_gcm_ghash_ctx *ctx,
 				       struct scatterlist *sg, int len)
 {
 	struct scatter_walk walk;
 	u8 *src;
 	int n;

 	scatterwalk_start(&walk, sg);

 	while (len) {
 		n = scatterwalk_clamp(&walk, len);

 		if (!n) {
 			scatterwalk_start(&walk, sg_next(walk.sg));
 			n = scatterwalk_clamp(&walk, len);
 		}

 		src = scatterwalk_map(&walk, 0);

 		crypto_gcm_ghash_update(ctx, src, n);
 		len -= n;

 		scatterwalk_unmap(src, 0);
 		scatterwalk_advance(&walk, n);
 		scatterwalk_done(&walk, 0, len);
 		if (len)
 			crypto_yield(ctx->flags);
 	}
 }

 static void crypto_gcm_ghash_flush(struct crypto_gcm_ghash_ctx *ctx)
 {
 	u8 *dst = ctx->buffer;

 	if (ctx->bytes) {
 		u8 *tmp = dst + (16 - ctx->bytes);

 		while (ctx->bytes--)
 			*tmp++ ^= 0;

 		gf128mul_4k_lle((be128 *)dst, ctx->gf128);
 	}

 	ctx->bytes = 0;
 }

 static void crypto_gcm_ghash_final_xor(struct crypto_gcm_ghash_ctx *ctx,
 				       unsigned int authlen,
 				       unsigned int cryptlen, u8 *dst)
 {
 	u8 *buf = ctx->buffer;
 	u128 lengths;

 	lengths.a = cpu_to_be64(authlen * 8);
 	lengths.b = cpu_to_be64(cryptlen * 8);

 	crypto_gcm_ghash_flush(ctx);
 	crypto_xor(buf, (u8 *)&lengths, 16);
 	gf128mul_4k_lle((be128 *)buf, ctx->gf128);
 	crypto_xor(dst, buf, 16);
 }

 static inline void crypto_gcm_set_counter(u8 *counterblock, u32 value)
 {
 	*((u32 *)&counterblock[12]) = cpu_to_be32(value);
 }

 static int crypto_gcm_encrypt_counter(struct crypto_aead *aead, u8 *block,
 				       u32 value, const u8 *iv)
 {
 	struct crypto_gcm_ctx *ctx = crypto_aead_ctx(aead);
 	struct crypto_ablkcipher *ctr = ctx->ctr;
 	struct ablkcipher_request req;
 	struct scatterlist sg;
 	u8 counterblock[16];

 	if (iv == NULL)
 		memset(counterblock, 0, 12);
 	else
 		memcpy(counterblock, iv, 12);

 	crypto_gcm_set_counter(counterblock, value);

 	sg_init_one(&sg, block, 16);
 	ablkcipher_request_set_tfm(&req, ctr);
 	ablkcipher_request_set_crypt(&req, &sg, &sg, 16, counterblock);
 	ablkcipher_request_set_callback(&req, 0, NULL, NULL);
 	memset(block, 0, 16);
 	return crypto_ablkcipher_encrypt(&req);
 }

 static int crypto_gcm_setkey(struct crypto_aead *aead, const u8 *key,
 			     unsigned int keylen)
 {
 	struct crypto_gcm_ctx *ctx = crypto_aead_ctx(aead);
 	struct crypto_ablkcipher *ctr = ctx->ctr;
 	int alignmask = crypto_ablkcipher_alignmask(ctr);
 	u8 alignbuf[16+alignmask];
 	u8 *hash = (u8 *)ALIGN((unsigned long)alignbuf, alignmask+1);
 	int err = 0;

 	crypto_ablkcipher_clear_flags(ctr, CRYPTO_TFM_REQ_MASK);
 	crypto_ablkcipher_set_flags(ctr, crypto_aead_get_flags(aead) &
 				   CRYPTO_TFM_REQ_MASK);

 	err = crypto_ablkcipher_setkey(ctr, key, keylen);
 	if (err)
 		goto out;

 	crypto_aead_set_flags(aead, crypto_ablkcipher_get_flags(ctr) &
 				       CRYPTO_TFM_RES_MASK);

 	err = crypto_gcm_encrypt_counter(aead, hash, -1, NULL);
 	if (err)
 		goto out;

 	if (ctx->gf128 != NULL)
 		gf128mul_free_4k(ctx->gf128);

 	ctx->gf128 = gf128mul_init_4k_lle((be128 *)hash);

 	if (ctx->gf128 == NULL)
 		err = -ENOMEM;

  out:
 	return err;
 }

 static int crypto_gcm_init_crypt(struct ablkcipher_request *ablk_req,
 				  struct aead_request *req,
 				  void (*done)(struct crypto_async_request *,
 					       int))
 {
 	struct crypto_aead *aead = crypto_aead_reqtfm(req);
 	struct crypto_gcm_ctx *ctx = crypto_aead_ctx(aead);
 	struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
 	u32 flags = req->base.tfm->crt_flags;
 	u8 *auth_tag = pctx->auth_tag;
 	u8 *counter = pctx->counter;
 	struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;
 	int err = 0;

 	ablkcipher_request_set_tfm(ablk_req, ctx->ctr);
 	ablkcipher_request_set_callback(ablk_req, aead_request_flags(req),
 					done, req);
 	ablkcipher_request_set_crypt(ablk_req, req->src, req->dst,
 				     req->cryptlen, counter);

 	err = crypto_gcm_encrypt_counter(aead, auth_tag, 0, req->iv);
 	if (err)
 		goto out;

 	memcpy(counter, req->iv, 12);
 	crypto_gcm_set_counter(counter, 1);

 	crypto_gcm_ghash_init(ghash, flags, ctx->gf128);

 	if (req->assoclen) {
 		crypto_gcm_ghash_update_sg(ghash, req->assoc, req->assoclen);
 		crypto_gcm_ghash_flush(ghash);
 	}

  out:
 	return err;
 }

 static void crypto_gcm_encrypt_done(struct crypto_async_request *areq, int err)
 {
 	struct aead_request *req = areq->data;
 	struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
 	u8 *auth_tag = pctx->auth_tag;
 	struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;

 	crypto_gcm_ghash_update_sg(ghash, req->dst, req->cryptlen);
 	crypto_gcm_ghash_final_xor(ghash, req->assoclen, req->cryptlen,
 				   auth_tag);

 	aead_request_complete(req, err);
 }

 static int crypto_gcm_encrypt(struct aead_request *req)
 {
 	struct ablkcipher_request abreq;
 	struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
 	u8 *auth_tag = pctx->auth_tag;
 	struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;
 	int err = 0;

 	err = crypto_gcm_init_crypt(&abreq, req, crypto_gcm_encrypt_done);
 	if (err)
 		return err;

 	if (req->cryptlen) {
 		err = crypto_ablkcipher_encrypt(&abreq);
 		if (err)
 			return err;

 		crypto_gcm_ghash_update_sg(ghash, req->dst, req->cryptlen);
 	}

 	crypto_gcm_ghash_final_xor(ghash, req->assoclen, req->cryptlen,
 				   auth_tag);

 	return err;
 }

 static void crypto_gcm_decrypt_done(struct crypto_async_request *areq, int err)
 {
 	aead_request_complete(areq->data, err);
 }

 static int crypto_gcm_decrypt(struct aead_request *req)
 {
 	struct ablkcipher_request abreq;
 	struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
 	u8 *auth_tag = pctx->auth_tag;
 	struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;
 	u8 tag[16];
 	int err;

 	if (!req->cryptlen)
 		return -EINVAL;

 	memcpy(tag, auth_tag, 16);
 	err = crypto_gcm_init_crypt(&abreq, req, crypto_gcm_decrypt_done);
 	if (err)
 		return err;

 	crypto_gcm_ghash_update_sg(ghash, req->src, req->cryptlen);
 	crypto_gcm_ghash_final_xor(ghash, req->assoclen, req->cryptlen,
 				   auth_tag);

 	if (memcmp(tag, auth_tag, 16))
 		return -EINVAL;

 	return crypto_ablkcipher_decrypt(&abreq);
 }

 static int crypto_gcm_init_tfm(struct crypto_tfm *tfm)
 {
 	struct crypto_instance *inst = (void *)tfm->__crt_alg;
 	struct gcm_instance_ctx *ictx = crypto_instance_ctx(inst);
 	struct crypto_gcm_ctx *ctx = crypto_tfm_ctx(tfm);
 	struct crypto_ablkcipher *ctr;
 	unsigned long align;
 	int err;

 	ctr = crypto_spawn_ablkcipher(&ictx->ctr);
 	err = PTR_ERR(ctr);
 	if (IS_ERR(ctr))
 		return err;

 	ctx->ctr = ctr;
 	ctx->gf128 = NULL;

 	align = max_t(unsigned long, crypto_ablkcipher_alignmask(ctr),
 		      __alignof__(u32) - 1);
 	align &= ~(crypto_tfm_ctx_alignment() - 1);
 	tfm->crt_aead.reqsize = align + sizeof(struct crypto_gcm_req_priv_ctx);

 	return 0;
 }

 static void crypto_gcm_exit_tfm(struct crypto_tfm *tfm)
 {
 	struct crypto_gcm_ctx *ctx = crypto_tfm_ctx(tfm);

 	if (ctx->gf128 != NULL)
 		gf128mul_free_4k(ctx->gf128);

 	crypto_free_ablkcipher(ctx->ctr);
 }

 static struct crypto_instance *crypto_gcm_alloc(struct rtattr **tb)
 {
 	struct crypto_instance *inst;
 	struct crypto_alg *ctr;
 	struct crypto_alg *cipher;
 	struct gcm_instance_ctx *ctx;
 	int err;
 	char ctr_name[CRYPTO_MAX_ALG_NAME];

 	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_AEAD);
 	if (err)
 		return ERR_PTR(err);

 	cipher = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
 			      CRYPTO_ALG_TYPE_MASK);

 	inst = ERR_PTR(PTR_ERR(cipher));
 	if (IS_ERR(cipher))
 		return inst;

 	inst = ERR_PTR(ENAMETOOLONG);
 	if (snprintf(
 		    ctr_name, CRYPTO_MAX_ALG_NAME,
 		    "ctr(%s,0,16,4)", cipher->cra_name) >= CRYPTO_MAX_ALG_NAME)
 		return inst;

 	ctr = crypto_alg_mod_lookup(ctr_name, CRYPTO_ALG_TYPE_BLKCIPHER,
 				    CRYPTO_ALG_TYPE_MASK);

 	if (IS_ERR(ctr))
 		return ERR_PTR(PTR_ERR(ctr));

 	if (cipher->cra_blocksize != 16)
 		goto out_put_ctr;

 	inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
 	err = -ENOMEM;
 	if (!inst)
 		goto out_put_ctr;

 	err = -ENAMETOOLONG;
 	if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
 		     "gcm(%s)", cipher->cra_name) >= CRYPTO_MAX_ALG_NAME ||
 	    snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
 		     "gcm(%s)", cipher->cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
 		goto err_free_inst;


 	ctx = crypto_instance_ctx(inst);
 	err = crypto_init_spawn(&ctx->ctr, ctr, inst, CRYPTO_ALG_TYPE_MASK);
 	if (err)
 		goto err_free_inst;

 	inst->alg.cra_flags = CRYPTO_ALG_TYPE_AEAD | CRYPTO_ALG_ASYNC;
 	inst->alg.cra_priority = ctr->cra_priority;
 	inst->alg.cra_blocksize = 16;
 	inst->alg.cra_alignmask = __alignof__(u32) - 1;
 	inst->alg.cra_type = &crypto_aead_type;
 	inst->alg.cra_aead.ivsize = 12;
 	inst->alg.cra_aead.authsize = 16;
 	inst->alg.cra_ctxsize = sizeof(struct crypto_gcm_ctx);
 	inst->alg.cra_init = crypto_gcm_init_tfm;
 	inst->alg.cra_exit = crypto_gcm_exit_tfm;
 	inst->alg.cra_aead.setkey = crypto_gcm_setkey;
 	inst->alg.cra_aead.encrypt = crypto_gcm_encrypt;
 	inst->alg.cra_aead.decrypt = crypto_gcm_decrypt;

 out:
 	crypto_mod_put(ctr);
 	return inst;
 err_free_inst:
 	kfree(inst);
 out_put_ctr:
 	inst = ERR_PTR(err);
 	goto out;
 }

 static void crypto_gcm_free(struct crypto_instance *inst)
 {
 	struct gcm_instance_ctx *ctx = crypto_instance_ctx(inst);

 	crypto_drop_spawn(&ctx->ctr);
 	kfree(inst);
 }

 static struct crypto_template crypto_gcm_tmpl = {
 	.name = "gcm",
 	.alloc = crypto_gcm_alloc,
 	.free = crypto_gcm_free,
 	.module = THIS_MODULE,
 };

 static int __init crypto_gcm_module_init(void)
 {
 	return crypto_register_template(&crypto_gcm_tmpl);
 }

 static void __exit crypto_gcm_module_exit(void)
 {
 	crypto_unregister_template(&crypto_gcm_tmpl);
 }

 module_init(crypto_gcm_module_init);
 module_exit(crypto_gcm_module_exit);

 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("Galois/Counter Mode");
 MODULE_AUTHOR("Mikko Herranen <mh1@iki.fi>");
	/*
	* GCM: Galois/Counter Mode.
	*
	* Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi>
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 as published
	* by the Free Software Foundation.
	*/

	#include <crypto/algapi.h>
	#include <crypto/gf128mul.h>
	#include <linux/err.h>
	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/slab.h>

	#include "scatterwalk.h"

	struct gcm_instance_ctx {
	struct crypto_spawn ctr;
	};

	struct crypto_gcm_ctx {
	struct crypto_ablkcipher *ctr;
	struct gf128mul_4k *gf128;
	};

	struct crypto_gcm_ghash_ctx {
	u32 bytes;
	u32 flags;
	struct gf128mul_4k *gf128;
	u8 buffer[16];
	};

	struct crypto_gcm_req_priv_ctx {
	u8 auth_tag[16];
	u8 counter[16];
	struct crypto_gcm_ghash_ctx ghash;
	};

	static void crypto_gcm_ghash_init(struct crypto_gcm_ghash_ctx *ctx, u32 flags,
	struct gf128mul_4k *gf128)
	{
	ctx->bytes = 0;
	ctx->flags = flags;
	ctx->gf128 = gf128;
	memset(ctx->buffer, 0, 16);
	}

	static void crypto_gcm_ghash_update(struct crypto_gcm_ghash_ctx *ctx,
	const u8 *src, unsigned int srclen)
	{
	u8 *dst = ctx->buffer;

	if (ctx->bytes) {
	int n = min(srclen, ctx->bytes);
	u8 *pos = dst + (16 - ctx->bytes);

	ctx->bytes -= n;
	srclen -= n;

	while (n--)
	pos++ ^= src++;

	if (!ctx->bytes)
	gf128mul_4k_lle((be128 *)dst, ctx->gf128);
	}

	while (srclen >= 16) {
	crypto_xor(dst, src, 16);
	gf128mul_4k_lle((be128 *)dst, ctx->gf128);
	src += 16;
	srclen -= 16;
	}

	if (srclen) {
	ctx->bytes = 16 - srclen;
	while (srclen--)
	dst++ ^= src++;
	}
	}

	static void crypto_gcm_ghash_update_sg(struct crypto_gcm_ghash_ctx *ctx,
	struct scatterlist *sg, int len)
	{
	struct scatter_walk walk;
	u8 *src;
	int n;

	scatterwalk_start(&walk, sg);

	while (len) {
	n = scatterwalk_clamp(&walk, len);

	if (!n) {
	scatterwalk_start(&walk, sg_next(walk.sg));
	n = scatterwalk_clamp(&walk, len);
	}

	src = scatterwalk_map(&walk, 0);

	crypto_gcm_ghash_update(ctx, src, n);
	len -= n;

	scatterwalk_unmap(src, 0);
	scatterwalk_advance(&walk, n);
	scatterwalk_done(&walk, 0, len);
	if (len)
	crypto_yield(ctx->flags);
	}
	}

	static void crypto_gcm_ghash_flush(struct crypto_gcm_ghash_ctx *ctx)
	{
	u8 *dst = ctx->buffer;

	if (ctx->bytes) {
	u8 *tmp = dst + (16 - ctx->bytes);

	while (ctx->bytes--)
	*tmp++ ^= 0;

	gf128mul_4k_lle((be128 *)dst, ctx->gf128);
	}

	ctx->bytes = 0;
	}

	static void crypto_gcm_ghash_final_xor(struct crypto_gcm_ghash_ctx *ctx,
	unsigned int authlen,
	unsigned int cryptlen, u8 *dst)
	{
	u8 *buf = ctx->buffer;
	u128 lengths;

	lengths.a = cpu_to_be64(authlen * 8);
	lengths.b = cpu_to_be64(cryptlen * 8);

	crypto_gcm_ghash_flush(ctx);
	crypto_xor(buf, (u8 *)&lengths, 16);
	gf128mul_4k_lle((be128 *)buf, ctx->gf128);
	crypto_xor(dst, buf, 16);
	}

	static inline void crypto_gcm_set_counter(u8 *counterblock, u32 value)
	{
	((u32 )&counterblock[12]) = cpu_to_be32(value);
	}

	static int crypto_gcm_encrypt_counter(struct crypto_aead aead, u8 block,
	u32 value, const u8 *iv)
	{
	struct crypto_gcm_ctx *ctx = crypto_aead_ctx(aead);
	struct crypto_ablkcipher *ctr = ctx->ctr;
	struct ablkcipher_request req;
	struct scatterlist sg;
	u8 counterblock[16];

	if (iv == NULL)
	memset(counterblock, 0, 12);
	else
	memcpy(counterblock, iv, 12);

	crypto_gcm_set_counter(counterblock, value);

	sg_init_one(&sg, block, 16);
	ablkcipher_request_set_tfm(&req, ctr);
	ablkcipher_request_set_crypt(&req, &sg, &sg, 16, counterblock);
	ablkcipher_request_set_callback(&req, 0, NULL, NULL);
	memset(block, 0, 16);
	return crypto_ablkcipher_encrypt(&req);
	}

	static int crypto_gcm_setkey(struct crypto_aead aead, const u8 key,
	unsigned int keylen)
	{
	struct crypto_gcm_ctx *ctx = crypto_aead_ctx(aead);
	struct crypto_ablkcipher *ctr = ctx->ctr;
	int alignmask = crypto_ablkcipher_alignmask(ctr);
	u8 alignbuf[16+alignmask];
	u8 hash = (u8 )ALIGN((unsigned long)alignbuf, alignmask+1);
	int err = 0;

	crypto_ablkcipher_clear_flags(ctr, CRYPTO_TFM_REQ_MASK);
	crypto_ablkcipher_set_flags(ctr, crypto_aead_get_flags(aead) &
	CRYPTO_TFM_REQ_MASK);

	err = crypto_ablkcipher_setkey(ctr, key, keylen);
	if (err)
	goto out;

	crypto_aead_set_flags(aead, crypto_ablkcipher_get_flags(ctr) &
	CRYPTO_TFM_RES_MASK);

	err = crypto_gcm_encrypt_counter(aead, hash, -1, NULL);
	if (err)
	goto out;

	if (ctx->gf128 != NULL)
	gf128mul_free_4k(ctx->gf128);

	ctx->gf128 = gf128mul_init_4k_lle((be128 *)hash);

	if (ctx->gf128 == NULL)
	err = -ENOMEM;

	out:
	return err;
	}

	static int crypto_gcm_init_crypt(struct ablkcipher_request *ablk_req,
	struct aead_request *req,
	void (done)(struct crypto_async_request ,
	int))
	{
	struct crypto_aead *aead = crypto_aead_reqtfm(req);
	struct crypto_gcm_ctx *ctx = crypto_aead_ctx(aead);
	struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
	u32 flags = req->base.tfm->crt_flags;
	u8 *auth_tag = pctx->auth_tag;
	u8 *counter = pctx->counter;
	struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;
	int err = 0;

	ablkcipher_request_set_tfm(ablk_req, ctx->ctr);
	ablkcipher_request_set_callback(ablk_req, aead_request_flags(req),
	done, req);
	ablkcipher_request_set_crypt(ablk_req, req->src, req->dst,
	req->cryptlen, counter);

	err = crypto_gcm_encrypt_counter(aead, auth_tag, 0, req->iv);
	if (err)
	goto out;

	memcpy(counter, req->iv, 12);
	crypto_gcm_set_counter(counter, 1);

	crypto_gcm_ghash_init(ghash, flags, ctx->gf128);

	if (req->assoclen) {
	crypto_gcm_ghash_update_sg(ghash, req->assoc, req->assoclen);
	crypto_gcm_ghash_flush(ghash);
	}

	out:
	return err;
	}

	static void crypto_gcm_encrypt_done(struct crypto_async_request *areq, int err)
	{
	struct aead_request *req = areq->data;
	struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
	u8 *auth_tag = pctx->auth_tag;
	struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;

	crypto_gcm_ghash_update_sg(ghash, req->dst, req->cryptlen);
	crypto_gcm_ghash_final_xor(ghash, req->assoclen, req->cryptlen,
	auth_tag);

	aead_request_complete(req, err);
	}

	static int crypto_gcm_encrypt(struct aead_request *req)
	{
	struct ablkcipher_request abreq;
	struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
	u8 *auth_tag = pctx->auth_tag;
	struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;
	int err = 0;

	err = crypto_gcm_init_crypt(&abreq, req, crypto_gcm_encrypt_done);
	if (err)
	return err;

	if (req->cryptlen) {
	err = crypto_ablkcipher_encrypt(&abreq);
	if (err)
	return err;

	crypto_gcm_ghash_update_sg(ghash, req->dst, req->cryptlen);
	}

	crypto_gcm_ghash_final_xor(ghash, req->assoclen, req->cryptlen,
	auth_tag);

	return err;
	}

	static void crypto_gcm_decrypt_done(struct crypto_async_request *areq, int err)
	{
	aead_request_complete(areq->data, err);
	}

	static int crypto_gcm_decrypt(struct aead_request *req)
	{
	struct ablkcipher_request abreq;
	struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
	u8 *auth_tag = pctx->auth_tag;
	struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;
	u8 tag[16];
	int err;

	if (!req->cryptlen)
	return -EINVAL;

	memcpy(tag, auth_tag, 16);
	err = crypto_gcm_init_crypt(&abreq, req, crypto_gcm_decrypt_done);
	if (err)
	return err;

	crypto_gcm_ghash_update_sg(ghash, req->src, req->cryptlen);
	crypto_gcm_ghash_final_xor(ghash, req->assoclen, req->cryptlen,
	auth_tag);

	if (memcmp(tag, auth_tag, 16))
	return -EINVAL;

	return crypto_ablkcipher_decrypt(&abreq);
	}

	static int crypto_gcm_init_tfm(struct crypto_tfm *tfm)
	{
	struct crypto_instance inst = (void )tfm->__crt_alg;
	struct gcm_instance_ctx *ictx = crypto_instance_ctx(inst);
	struct crypto_gcm_ctx *ctx = crypto_tfm_ctx(tfm);
	struct crypto_ablkcipher *ctr;
	unsigned long align;
	int err;

	ctr = crypto_spawn_ablkcipher(&ictx->ctr);
	err = PTR_ERR(ctr);
	if (IS_ERR(ctr))
	return err;

	ctx->ctr = ctr;
	ctx->gf128 = NULL;

	align = max_t(unsigned long, crypto_ablkcipher_alignmask(ctr),
	__alignof__(u32) - 1);
	align &= ~(crypto_tfm_ctx_alignment() - 1);
	tfm->crt_aead.reqsize = align + sizeof(struct crypto_gcm_req_priv_ctx);

	return 0;
	}

	static void crypto_gcm_exit_tfm(struct crypto_tfm *tfm)
	{
	struct crypto_gcm_ctx *ctx = crypto_tfm_ctx(tfm);

	if (ctx->gf128 != NULL)
	gf128mul_free_4k(ctx->gf128);

	crypto_free_ablkcipher(ctx->ctr);
	}

	static struct crypto_instance crypto_gcm_alloc(struct rtattr *tb)
	{
	struct crypto_instance *inst;
	struct crypto_alg *ctr;
	struct crypto_alg *cipher;
	struct gcm_instance_ctx *ctx;
	int err;
	char ctr_name[CRYPTO_MAX_ALG_NAME];

	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_AEAD);
	if (err)
	return ERR_PTR(err);

	cipher = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
	CRYPTO_ALG_TYPE_MASK);

	inst = ERR_PTR(PTR_ERR(cipher));
	if (IS_ERR(cipher))
	return inst;

	inst = ERR_PTR(ENAMETOOLONG);
	if (snprintf(
	ctr_name, CRYPTO_MAX_ALG_NAME,
	"ctr(%s,0,16,4)", cipher->cra_name) >= CRYPTO_MAX_ALG_NAME)
	return inst;

	ctr = crypto_alg_mod_lookup(ctr_name, CRYPTO_ALG_TYPE_BLKCIPHER,
	CRYPTO_ALG_TYPE_MASK);

	if (IS_ERR(ctr))
	return ERR_PTR(PTR_ERR(ctr));

	if (cipher->cra_blocksize != 16)
	goto out_put_ctr;

	inst = kzalloc(sizeof(inst) + sizeof(ctx), GFP_KERNEL);
	err = -ENOMEM;
	if (!inst)
	goto out_put_ctr;

	err = -ENAMETOOLONG;
	if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
	"gcm(%s)", cipher->cra_name) >= CRYPTO_MAX_ALG_NAME \|\|
	snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
	"gcm(%s)", cipher->cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
	goto err_free_inst;


	ctx = crypto_instance_ctx(inst);
	err = crypto_init_spawn(&ctx->ctr, ctr, inst, CRYPTO_ALG_TYPE_MASK);
	if (err)
	goto err_free_inst;

	inst->alg.cra_flags = CRYPTO_ALG_TYPE_AEAD \| CRYPTO_ALG_ASYNC;
	inst->alg.cra_priority = ctr->cra_priority;
	inst->alg.cra_blocksize = 16;
	inst->alg.cra_alignmask = __alignof__(u32) - 1;
	inst->alg.cra_type = &crypto_aead_type;
	inst->alg.cra_aead.ivsize = 12;
	inst->alg.cra_aead.authsize = 16;
	inst->alg.cra_ctxsize = sizeof(struct crypto_gcm_ctx);
	inst->alg.cra_init = crypto_gcm_init_tfm;
	inst->alg.cra_exit = crypto_gcm_exit_tfm;
	inst->alg.cra_aead.setkey = crypto_gcm_setkey;
	inst->alg.cra_aead.encrypt = crypto_gcm_encrypt;
	inst->alg.cra_aead.decrypt = crypto_gcm_decrypt;

	out:
	crypto_mod_put(ctr);
	return inst;
	err_free_inst:
	kfree(inst);
	out_put_ctr:
	inst = ERR_PTR(err);
	goto out;
	}

	static void crypto_gcm_free(struct crypto_instance *inst)
	{
	struct gcm_instance_ctx *ctx = crypto_instance_ctx(inst);

	crypto_drop_spawn(&ctx->ctr);
	kfree(inst);
	}

	static struct crypto_template crypto_gcm_tmpl = {
	.name = "gcm",
	.alloc = crypto_gcm_alloc,
	.free = crypto_gcm_free,
	.module = THIS_MODULE,
	};

	static int __init crypto_gcm_module_init(void)
	{
	return crypto_register_template(&crypto_gcm_tmpl);
	}

	static void __exit crypto_gcm_module_exit(void)
	{
	crypto_unregister_template(&crypto_gcm_tmpl);
	}

	module_init(crypto_gcm_module_init);
	module_exit(crypto_gcm_module_exit);

	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("Galois/Counter Mode");
	MODULE_AUTHOR("Mikko Herranen <mh1@iki.fi>");