/*
   * Copyright 2013 Freescale Semiconductor, Inc.
   * Copyright 2017 NXP Semiconductor, Inc.
   *
   * 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/aead.h>
  #include <crypto/internal/hash.h>
  #include <crypto/internal/skcipher.h>
  #include <crypto/authenc.h>
  #include <crypto/null.h>
  #include <crypto/scatterwalk.h>
  #include <linux/err.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/rtnetlink.h>
  
  struct tls_instance_ctx {
  	struct crypto_ahash_spawn auth;
  	struct crypto_skcipher_spawn enc;
  };
  
  struct crypto_tls_ctx {
  	unsigned int reqoff;
  	struct crypto_ahash *auth;
  	struct crypto_skcipher *enc;
  	struct crypto_sync_skcipher *null;
  };
  
  struct tls_request_ctx {
  	/*
  	 * cryptlen holds the payload length in the case of encryption or
  	 * payload_len + icv_len + padding_len in case of decryption
  	 */
  	unsigned int cryptlen;
  	/* working space for partial results */
  	struct scatterlist tmp[2];
  	struct scatterlist cipher[2];
  	struct scatterlist dst[2];
  	char tail[];
  };
  
  struct async_op {
  	struct completion completion;
  	int err;
  };
  
  static void tls_async_op_done(struct crypto_async_request *req, int err)
  {
  	struct async_op *areq = req->data;
  
  	if (err == -EINPROGRESS)
  		return;
  
  	areq->err = err;
  	complete(&areq->completion);
  }
  
  static int crypto_tls_setkey(struct crypto_aead *tls, const u8 *key,
  			     unsigned int keylen)
  {
  	struct crypto_tls_ctx *ctx = crypto_aead_ctx(tls);
  	struct crypto_ahash *auth = ctx->auth;
  	struct crypto_skcipher *enc = ctx->enc;
  	struct crypto_authenc_keys keys;
  	int err = -EINVAL;
  
  	if (crypto_authenc_extractkeys(&keys, key, keylen) != 0)
  		goto out;
  
  	crypto_ahash_clear_flags(auth, CRYPTO_TFM_REQ_MASK);
  	crypto_ahash_set_flags(auth, crypto_aead_get_flags(tls) &
  				    CRYPTO_TFM_REQ_MASK);
  	err = crypto_ahash_setkey(auth, keys.authkey, keys.authkeylen);
  	if (err)
  		goto out;
  
  	crypto_skcipher_clear_flags(enc, CRYPTO_TFM_REQ_MASK);
  	crypto_skcipher_set_flags(enc, crypto_aead_get_flags(tls) &
  					 CRYPTO_TFM_REQ_MASK);
  	err = crypto_skcipher_setkey(enc, keys.enckey, keys.enckeylen);
  
  out:
  	memzero_explicit(&keys, sizeof(keys));
  	return err;
  }
  
  /**
   * crypto_tls_genicv - Calculate hmac digest for a TLS record
   * @hash:	(output) buffer to save the digest into
   * @src:	(input) scatterlist with the assoc and payload data
   * @srclen:	(input) size of the source buffer (assoclen + cryptlen)
   * @req:	(input) aead request
   **/
  static int crypto_tls_genicv(u8 *hash, struct scatterlist *src,
  			     unsigned int srclen, struct aead_request *req)
  {
  	struct crypto_aead *tls = crypto_aead_reqtfm(req);
  	struct crypto_tls_ctx *ctx = crypto_aead_ctx(tls);
  	struct tls_request_ctx *treq_ctx = aead_request_ctx(req);
  	struct async_op ahash_op;
  	struct ahash_request *ahreq = (void *)(treq_ctx->tail + ctx->reqoff);
  	unsigned int flags = CRYPTO_TFM_REQ_MAY_SLEEP;
  	int err = -EBADMSG;
  
  	 /* Bail out if the request assoc len is 0 */
  	if (!req->assoclen)
  		return err;
  
  	init_completion(&ahash_op.completion);
  
  	/* the hash transform to be executed comes from the original request */
  	ahash_request_set_tfm(ahreq, ctx->auth);
  	/* prepare the hash request with input data and result pointer */
  	ahash_request_set_crypt(ahreq, src, hash, srclen);
  	/* set the notifier for when the async hash function returns */
  	ahash_request_set_callback(ahreq, aead_request_flags(req) & flags,
  				   tls_async_op_done, &ahash_op);
  
  	/* Calculate the digest on the given data. The result is put in hash */
  	err = crypto_ahash_digest(ahreq);
  	if (err == -EINPROGRESS) {
  		err = wait_for_completion_interruptible(&ahash_op.completion);
  		if (!err)
  			err = ahash_op.err;
  	}
  
  	return err;
  }
  
  /**
   * crypto_tls_gen_padicv - Calculate and pad hmac digest for a TLS record
   * @hash:	(output) buffer to save the digest and padding into
   * @phashlen:	(output) the size of digest + padding
   * @req:	(input) aead request
   **/
  static int crypto_tls_gen_padicv(u8 *hash, unsigned int *phashlen,
  				 struct aead_request *req)
  {
  	struct crypto_aead *tls = crypto_aead_reqtfm(req);
  	unsigned int hash_size = crypto_aead_authsize(tls);
  	unsigned int block_size = crypto_aead_blocksize(tls);
  	unsigned int srclen = req->cryptlen + hash_size;
  	unsigned int icvlen = req->cryptlen + req->assoclen;
  	unsigned int padlen;
  	int err;
  
  	err = crypto_tls_genicv(hash, req->src, icvlen, req);
  	if (err)
  		goto out;
  
  	/* add padding after digest */
  	padlen = block_size - (srclen % block_size);
  	memset(hash + hash_size, padlen - 1, padlen);
  
  	*phashlen = hash_size + padlen;
  out:
  	return err;
  }
  
  static int crypto_tls_copy_data(struct aead_request *req,
  				struct scatterlist *src,
  				struct scatterlist *dst,
  				unsigned int len)
  {
  	struct crypto_aead *tls = crypto_aead_reqtfm(req);
  	struct crypto_tls_ctx *ctx = crypto_aead_ctx(tls);
  	SYNC_SKCIPHER_REQUEST_ON_STACK(skreq, ctx->null);
  
  	skcipher_request_set_sync_tfm(skreq, ctx->null);
  	skcipher_request_set_callback(skreq, aead_request_flags(req),
  				      NULL, NULL);
  	skcipher_request_set_crypt(skreq, src, dst, len, NULL);
  
  	return crypto_skcipher_encrypt(skreq);
  }
  
  static int crypto_tls_encrypt(struct aead_request *req)
  {
  	struct crypto_aead *tls = crypto_aead_reqtfm(req);
  	struct crypto_tls_ctx *ctx = crypto_aead_ctx(tls);
  	struct tls_request_ctx *treq_ctx = aead_request_ctx(req);
  	struct skcipher_request *skreq;
  	struct scatterlist *cipher = treq_ctx->cipher;
  	struct scatterlist *tmp = treq_ctx->tmp;
  	struct scatterlist *sg, *src, *dst;
  	unsigned int cryptlen, phashlen;
  	u8 *hash = treq_ctx->tail;
  	int err;
  
  	/*
  	 * The hash result is saved at the beginning of the tls request ctx
  	 * and is aligned as required by the hash transform. Enough space was
  	 * allocated in crypto_tls_init_tfm to accommodate the difference. The
  	 * requests themselves start later at treq_ctx->tail + ctx->reqoff so
  	 * the result is not overwritten by the second (cipher) request.
  	 */
  	hash = (u8 *)ALIGN((unsigned long)hash +
  			   crypto_ahash_alignmask(ctx->auth),
  			   crypto_ahash_alignmask(ctx->auth) + 1);
  
  	/*
  	 * STEP 1: create ICV together with necessary padding
  	 */
  	err = crypto_tls_gen_padicv(hash, &phashlen, req);
  	if (err)
  		return err;
  
  	/*
  	 * STEP 2: Hash and padding are combined with the payload
  	 * depending on the form it arrives. Scatter tables must have at least
  	 * one page of data before chaining with another table and can't have
  	 * an empty data page. The following code addresses these requirements.
  	 *
  	 * If the payload is empty, only the hash is encrypted, otherwise the
  	 * payload scatterlist is merged with the hash. A special merging case
  	 * is when the payload has only one page of data. In that case the
  	 * payload page is moved to another scatterlist and prepared there for
  	 * encryption.
  	 */
  	if (req->cryptlen) {
  		src = scatterwalk_ffwd(tmp, req->src, req->assoclen);
  
  		sg_init_table(cipher, 2);
  		sg_set_buf(cipher + 1, hash, phashlen);
  
  		if (sg_is_last(src)) {
  			sg_set_page(cipher, sg_page(src), req->cryptlen,
  				    src->offset);
  			src = cipher;
  		} else {
  			unsigned int rem_len = req->cryptlen;
  
  			for (sg = src; rem_len > sg->length; sg = sg_next(sg))
  				rem_len -= min(rem_len, sg->length);
  
  			sg_set_page(cipher, sg_page(sg), rem_len, sg->offset);
  			sg_chain(sg, 1, cipher);
  		}
  	} else {
  		sg_init_one(cipher, hash, phashlen);
  		src = cipher;
  	}
  
  	/**
  	 * If src != dst copy the associated data from source to destination.
  	 * In both cases fast-forward passed the associated data in the dest.
  	 */
  	if (req->src != req->dst) {
  		err = crypto_tls_copy_data(req, req->src, req->dst,
  					   req->assoclen);
  		if (err)
  			return err;
  	}
  	dst = scatterwalk_ffwd(treq_ctx->dst, req->dst, req->assoclen);
  
  	/*
  	 * STEP 3: encrypt the frame and return the result
  	 */
  	cryptlen = req->cryptlen + phashlen;
  
  	/*
  	 * The hash and the cipher are applied at different times and their
  	 * requests can use the same memory space without interference
  	 */
  	skreq = (void *)(treq_ctx->tail + ctx->reqoff);
  	skcipher_request_set_tfm(skreq, ctx->enc);
  	skcipher_request_set_crypt(skreq, src, dst, cryptlen, req->iv);
  	skcipher_request_set_callback(skreq, aead_request_flags(req),
  				      req->base.complete, req->base.data);
  	/*
  	 * Apply the cipher transform. The result will be in req->dst when the
  	 * asynchronuous call terminates
  	 */
  	err = crypto_skcipher_encrypt(skreq);
  
  	return err;
  }
  
  static int crypto_tls_decrypt(struct aead_request *req)
  {
  	struct crypto_aead *tls = crypto_aead_reqtfm(req);
  	struct crypto_tls_ctx *ctx = crypto_aead_ctx(tls);
  	struct tls_request_ctx *treq_ctx = aead_request_ctx(req);
  	unsigned int cryptlen = req->cryptlen;
  	unsigned int hash_size = crypto_aead_authsize(tls);
  	unsigned int block_size = crypto_aead_blocksize(tls);
  	struct skcipher_request *skreq = (void *)(treq_ctx->tail + ctx->reqoff);
  	struct scatterlist *tmp = treq_ctx->tmp;
  	struct scatterlist *src, *dst;
  
  	u8 padding[255]; /* padding can be 0-255 bytes */
  	u8 pad_size;
  	u16 *len_field;
  	u8 *ihash, *hash = treq_ctx->tail;
  
  	int paderr = 0;
  	int err = -EINVAL;
  	int i;
  	struct async_op ciph_op;
  
  	/*
  	 * Rule out bad packets. The input packet length must be at least one
  	 * byte more than the hash_size
  	 */
  	if (cryptlen <= hash_size || cryptlen % block_size)
  		goto out;
  
  	/*
  	 * Step 1 - Decrypt the source. Fast-forward past the associated data
  	 * to the encrypted data. The result will be overwritten in place so
  	 * that the decrypted data will be adjacent to the associated data. The
  	 * last step (computing the hash) will have it's input data already
  	 * prepared and ready to be accessed at req->src.
  	 */
  	src = scatterwalk_ffwd(tmp, req->src, req->assoclen);
  	dst = src;
  
  	init_completion(&ciph_op.completion);
  	skcipher_request_set_tfm(skreq, ctx->enc);
  	skcipher_request_set_callback(skreq, aead_request_flags(req),
  				      tls_async_op_done, &ciph_op);
  	skcipher_request_set_crypt(skreq, src, dst, cryptlen, req->iv);
  	err = crypto_skcipher_decrypt(skreq);
  	if (err == -EINPROGRESS) {
  		err = wait_for_completion_interruptible(&ciph_op.completion);
  		if (!err)
  			err = ciph_op.err;
  	}
  	if (err)
  		goto out;
  
  	/*
  	 * Step 2 - Verify padding
  	 * Retrieve the last byte of the payload; this is the padding size.
  	 */
  	cryptlen -= 1;
  	scatterwalk_map_and_copy(&pad_size, dst, cryptlen, 1, 0);
  
  	/* RFC recommendation for invalid padding size. */
  	if (cryptlen < pad_size + hash_size) {
  		pad_size = 0;
  		paderr = -EBADMSG;
  	}
  	cryptlen -= pad_size;
  	scatterwalk_map_and_copy(padding, dst, cryptlen, pad_size, 0);
  
  	/* Padding content must be equal with pad_size. We verify it all */
  	for (i = 0; i < pad_size; i++)
  		if (padding[i] != pad_size)
  			paderr = -EBADMSG;
  
  	/*
  	 * Step 3 - Verify hash
  	 * Align the digest result as required by the hash transform. Enough
  	 * space was allocated in crypto_tls_init_tfm
  	 */
  	hash = (u8 *)ALIGN((unsigned long)hash +
  			   crypto_ahash_alignmask(ctx->auth),
  			   crypto_ahash_alignmask(ctx->auth) + 1);
  	/*
  	 * Two bytes at the end of the associated data make the length field.
  	 * It must be updated with the length of the cleartext message before
  	 * the hash is calculated.
  	 */
  	len_field = sg_virt(req->src) + req->assoclen - 2;
  	cryptlen -= hash_size;
  	*len_field = htons(cryptlen);
  
  	/* This is the hash from the decrypted packet. Save it for later */
  	ihash = hash + hash_size;
  	scatterwalk_map_and_copy(ihash, dst, cryptlen, hash_size, 0);
  
  	/* Now compute and compare our ICV with the one from the packet */
  	err = crypto_tls_genicv(hash, req->src, cryptlen + req->assoclen, req);
  	if (!err)
  		err = memcmp(hash, ihash, hash_size) ? -EBADMSG : 0;
  
  	if (req->src != req->dst) {
  		err = crypto_tls_copy_data(req, req->src, req->dst, cryptlen +
  					   req->assoclen);
  		if (err)
  			goto out;
  	}
  
  	/* return the first found error */
  	if (paderr)
  		err = paderr;
  
  out:
  	aead_request_complete(req, err);
  	return err;
  }
  
  static int crypto_tls_init_tfm(struct crypto_aead *tfm)
  {
  	struct aead_instance *inst = aead_alg_instance(tfm);
  	struct tls_instance_ctx *ictx = aead_instance_ctx(inst);
  	struct crypto_tls_ctx *ctx = crypto_aead_ctx(tfm);
  	struct crypto_ahash *auth;
  	struct crypto_skcipher *enc;
  	struct crypto_sync_skcipher *null;
  	int err;
  
  	auth = crypto_spawn_ahash(&ictx->auth);
  	if (IS_ERR(auth))
  		return PTR_ERR(auth);
  
  	enc = crypto_spawn_skcipher(&ictx->enc);
  	err = PTR_ERR(enc);
  	if (IS_ERR(enc))
  		goto err_free_ahash;
  
  	null = crypto_get_default_null_skcipher();
  	err = PTR_ERR(null);
  	if (IS_ERR(null))
  		goto err_free_skcipher;
  
  	ctx->auth = auth;
  	ctx->enc = enc;
  	ctx->null = null;
  
  	/*
  	 * Allow enough space for two digests. The two digests will be compared
  	 * during the decryption phase. One will come from the decrypted packet
  	 * and the other will be calculated. For encryption, one digest is
  	 * padded (up to a cipher blocksize) and chained with the payload
  	 */
  	ctx->reqoff = ALIGN(crypto_ahash_digestsize(auth) +
  			    crypto_ahash_alignmask(auth),
  			    crypto_ahash_alignmask(auth) + 1) +
  			    max(crypto_ahash_digestsize(auth),
  				crypto_skcipher_blocksize(enc));
  
  	crypto_aead_set_reqsize(tfm,
  				sizeof(struct tls_request_ctx) +
  				ctx->reqoff +
  				max_t(unsigned int,
  				      crypto_ahash_reqsize(auth) +
  				      sizeof(struct ahash_request),
  				      crypto_skcipher_reqsize(enc) +
  				      sizeof(struct skcipher_request)));
  
  	return 0;
  
  err_free_skcipher:
  	crypto_free_skcipher(enc);
  err_free_ahash:
  	crypto_free_ahash(auth);
  	return err;
  }
  
  static void crypto_tls_exit_tfm(struct crypto_aead *tfm)
  {
  	struct crypto_tls_ctx *ctx = crypto_aead_ctx(tfm);
  
  	crypto_free_ahash(ctx->auth);
  	crypto_free_skcipher(ctx->enc);
  	crypto_put_default_null_skcipher();
  }
  
  static void crypto_tls_free(struct aead_instance *inst)
  {
  	struct tls_instance_ctx *ctx = aead_instance_ctx(inst);
  
  	crypto_drop_skcipher(&ctx->enc);
  	crypto_drop_ahash(&ctx->auth);
  	kfree(inst);
  }
  
  static int crypto_tls_create(struct crypto_template *tmpl, struct rtattr **tb)
  {
  	struct crypto_attr_type *algt;
  	struct aead_instance *inst;
  	struct hash_alg_common *auth;
  	struct crypto_alg *auth_base;
  	struct skcipher_alg *enc;
  	struct tls_instance_ctx *ctx;
  	u32 mask;
  	int err;
  
  	algt = crypto_get_attr_type(tb);
  	if (IS_ERR(algt))
  		return PTR_ERR(algt);
  
  	if ((algt->type ^ CRYPTO_ALG_TYPE_AEAD) & algt->mask)
  		return -EINVAL;
  
  	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_AEAD, &mask);
  	if (err)
  		return err;
  
  	inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
  	if (!inst)
  		return -ENOMEM;
  	ctx = aead_instance_ctx(inst);
  
  	err = crypto_grab_ahash(&ctx->auth, aead_crypto_instance(inst),
  				crypto_attr_alg_name(tb[1]), 0, mask);
  	if (err)
  		goto err_free_inst;
  	auth = crypto_spawn_ahash_alg(&ctx->auth);
  	auth_base = &auth->base;
  
  	err = crypto_grab_skcipher(&ctx->enc, aead_crypto_instance(inst),
  				   crypto_attr_alg_name(tb[2]), 0, mask);
  	if (err)
  		goto err_free_inst;
  	enc = crypto_spawn_skcipher_alg(&ctx->enc);
  
  	err = -ENAMETOOLONG;
  	if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
  		     "tls10(%s,%s)", auth_base->cra_name,
  		     enc->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
  		goto err_free_inst;
  
  	if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
  		     "tls10(%s,%s)", auth_base->cra_driver_name,
  		     enc->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
  		goto err_free_inst;
  
  	inst->alg.base.cra_flags = (auth_base->cra_flags |
  					enc->base.cra_flags) & CRYPTO_ALG_ASYNC;
  	inst->alg.base.cra_priority = enc->base.cra_priority * 10 +
  					auth_base->cra_priority;
  	inst->alg.base.cra_blocksize = enc->base.cra_blocksize;
  	inst->alg.base.cra_alignmask = auth_base->cra_alignmask |
  					enc->base.cra_alignmask;
  	inst->alg.base.cra_ctxsize = sizeof(struct crypto_tls_ctx);
  
  	inst->alg.ivsize = crypto_skcipher_alg_ivsize(enc);
  	inst->alg.chunksize = crypto_skcipher_alg_chunksize(enc);
  	inst->alg.maxauthsize = auth->digestsize;
  
  	inst->alg.init = crypto_tls_init_tfm;
  	inst->alg.exit = crypto_tls_exit_tfm;
  
  	inst->alg.setkey = crypto_tls_setkey;
  	inst->alg.encrypt = crypto_tls_encrypt;
  	inst->alg.decrypt = crypto_tls_decrypt;
  
  	inst->free = crypto_tls_free;
  
  	err = aead_register_instance(tmpl, inst);
  	if (err) {
  err_free_inst:
  		crypto_tls_free(inst);
  	}
  
  	return err;
  }
  
  static struct crypto_template crypto_tls_tmpl = {
  	.name = "tls10",
  	.create = crypto_tls_create,
  	.module = THIS_MODULE,
  };
  
  static int __init crypto_tls_module_init(void)
  {
  	return crypto_register_template(&crypto_tls_tmpl);
  }
  
  static void __exit crypto_tls_module_exit(void)
  {
  	crypto_unregister_template(&crypto_tls_tmpl);
  }
  
  module_init(crypto_tls_module_init);
  module_exit(crypto_tls_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("TLS 1.0 record encryption");
  MODULE_ALIAS_CRYPTO("tls10");