/*
   * algif_aead: User-space interface for AEAD algorithms
   *
   * Copyright (C) 2014, Stephan Mueller <smueller@chronox.de>
   *
   * This file provides the user-space API for AEAD ciphers.
   *

   * 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.

   *
   * The following concept of the memory management is used:
   *
   * The kernel maintains two SGLs, the TX SGL and the RX SGL. The TX SGL is
   * filled by user space with the data submitted via sendpage/sendmsg. Filling
   * up the TX SGL does not cause a crypto operation -- the data will only be
   * tracked by the kernel. Upon receipt of one recvmsg call, the caller must
   * provide a buffer which is tracked with the RX SGL.
   *
   * During the processing of the recvmsg operation, the cipher request is
   * allocated and prepared. As part of the recvmsg operation, the processed
   * TX buffers are extracted from the TX SGL into a separate SGL.
   *
   * After the completion of the crypto operation, the RX SGL and the cipher
   * request is released. The extracted TX SGL parts are released together with
   * the RX SGL release.

   */

  #include <crypto/internal/aead.h>

  #include <crypto/scatterwalk.h>
  #include <crypto/if_alg.h>

  #include <crypto/skcipher.h>
  #include <crypto/null.h>

  #include <linux/init.h>
  #include <linux/list.h>
  #include <linux/kernel.h>
  #include <linux/mm.h>
  #include <linux/module.h>
  #include <linux/net.h>
  #include <net/sock.h>

  struct aead_tfm {
  	struct crypto_aead *aead;
  	bool has_key;

  	struct crypto_skcipher *null_tfm;

  };

  static inline bool aead_sufficient_data(struct sock *sk)
  {
  	struct alg_sock *ask = alg_sk(sk);
  	struct sock *psk = ask->parent;
  	struct alg_sock *pask = alg_sk(psk);

  	struct af_alg_ctx *ctx = ask->private;

  	struct aead_tfm *aeadc = pask->private;
  	struct crypto_aead *tfm = aeadc->aead;
  	unsigned int as = crypto_aead_authsize(tfm);

  	/*
  	 * The minimum amount of memory needed for an AEAD cipher is
  	 * the AAD and in case of decryption the tag.
  	 */
  	return ctx->used >= ctx->aead_assoclen + (ctx->enc ? 0 : as);

  }

  static int aead_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)

  {
  	struct sock *sk = sock->sk;
  	struct alg_sock *ask = alg_sk(sk);

  	struct sock *psk = ask->parent;
  	struct alg_sock *pask = alg_sk(psk);

  	struct aead_tfm *aeadc = pask->private;
  	struct crypto_aead *tfm = aeadc->aead;
  	unsigned int ivsize = crypto_aead_ivsize(tfm);

  	return af_alg_sendmsg(sock, msg, size, ivsize);

  }

  static int crypto_aead_copy_sgl(struct crypto_skcipher *null_tfm,
  				struct scatterlist *src,
  				struct scatterlist *dst, unsigned int len)
  {
  	SKCIPHER_REQUEST_ON_STACK(skreq, null_tfm);
  
  	skcipher_request_set_tfm(skreq, null_tfm);
  	skcipher_request_set_callback(skreq, CRYPTO_TFM_REQ_MAY_BACKLOG,
  				      NULL, NULL);
  	skcipher_request_set_crypt(skreq, src, dst, len, NULL);
  
  	return crypto_skcipher_encrypt(skreq);
  }

  static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
  			 size_t ignored, int flags)

  {
  	struct sock *sk = sock->sk;
  	struct alg_sock *ask = alg_sk(sk);

  	struct sock *psk = ask->parent;
  	struct alg_sock *pask = alg_sk(psk);

  	struct af_alg_ctx *ctx = ask->private;

  	struct aead_tfm *aeadc = pask->private;
  	struct crypto_aead *tfm = aeadc->aead;

  	struct crypto_skcipher *null_tfm = aeadc->null_tfm;

  	unsigned int i, as = crypto_aead_authsize(tfm);

  	struct af_alg_async_req *areq;

  	struct af_alg_tsgl *tsgl, *tmp;
  	struct scatterlist *rsgl_src, *tsgl_src = NULL;

  	int err = 0;
  	size_t used = 0;		/* [in]  TX bufs to be en/decrypted */
  	size_t outlen = 0;		/* [out] RX bufs produced by kernel */
  	size_t usedpages = 0;		/* [in]  RX bufs to be used from user */
  	size_t processed = 0;		/* [in]  TX bufs to be consumed */

  	if (!ctx->used) {
  		err = af_alg_wait_for_data(sk, flags);
  		if (err)
  			return err;
  	}

  	/*

  	 * Data length provided by caller via sendmsg/sendpage that has not
  	 * yet been processed.

  	 */

  	used = ctx->used;
  
  	/*
  	 * Make sure sufficient data is present -- note, the same check is
  	 * is also present in sendmsg/sendpage. The checks in sendpage/sendmsg
  	 * shall provide an information to the data sender that something is
  	 * wrong, but they are irrelevant to maintain the kernel integrity.
  	 * We need this check here too in case user space decides to not honor
  	 * the error message in sendmsg/sendpage and still call recvmsg. This
  	 * check here protects the kernel integrity.
  	 */

  	if (!aead_sufficient_data(sk))
  		return -EINVAL;

  	/*
  	 * Calculate the minimum output buffer size holding the result of the
  	 * cipher operation. When encrypting data, the receiving buffer is
  	 * larger by the tag length compared to the input buffer as the
  	 * encryption operation generates the tag. For decryption, the input
  	 * buffer provides the tag which is consumed resulting in only the
  	 * plaintext without a buffer for the tag returned to the caller.
  	 */
  	if (ctx->enc)
  		outlen = used + as;
  	else
  		outlen = used - as;

  	/*
  	 * The cipher operation input data is reduced by the associated data
  	 * length as this data is processed separately later on.
  	 */

  	used -= ctx->aead_assoclen;

  	/* Allocate cipher request for current operation. */

  	areq = af_alg_alloc_areq(sk, sizeof(struct af_alg_async_req) +
  				     crypto_aead_reqsize(tfm));
  	if (IS_ERR(areq))
  		return PTR_ERR(areq);

  
  	/* convert iovecs of output buffers into RX SGL */

  	err = af_alg_get_rsgl(sk, msg, flags, areq, outlen, &usedpages);
  	if (err)
  		goto free;

  	/*
  	 * Ensure output buffer is sufficiently large. If the caller provides
  	 * less buffer space, only use the relative required input size. This
  	 * allows AIO operation where the caller sent all data to be processed
  	 * and the AIO operation performs the operation on the different chunks
  	 * of the input data.
  	 */

  	if (usedpages < outlen) {

  		size_t less = outlen - usedpages;

  		if (used < less) {
  			err = -EINVAL;
  			goto free;
  		}
  		used -= less;
  		outlen -= less;
  	}

  	processed = used + ctx->aead_assoclen;

  	list_for_each_entry_safe(tsgl, tmp, &ctx->tsgl_list, list) {
  		for (i = 0; i < tsgl->cur; i++) {
  			struct scatterlist *process_sg = tsgl->sg + i;
  
  			if (!(process_sg->length) || !sg_page(process_sg))
  				continue;
  			tsgl_src = process_sg;
  			break;
  		}
  		if (tsgl_src)
  			break;
  	}
  	if (processed && !tsgl_src) {
  		err = -EFAULT;
  		goto free;
  	}

  	/*

  	 * Copy of AAD from source to destination
  	 *
  	 * The AAD is copied to the destination buffer without change. Even
  	 * when user space uses an in-place cipher operation, the kernel
  	 * will copy the data as it does not see whether such in-place operation
  	 * is initiated.
  	 *
  	 * To ensure efficiency, the following implementation ensure that the
  	 * ciphers are invoked to perform a crypto operation in-place. This
  	 * is achieved by memory management specified as follows.

  	 */

  
  	/* Use the RX SGL as source (and destination) for crypto op. */

  	rsgl_src = areq->first_rsgl.sgl.sg;

  
  	if (ctx->enc) {
  		/*
  		 * Encryption operation - The in-place cipher operation is
  		 * achieved by the following operation:
  		 *

  		 * TX SGL: AAD || PT

  		 *	    |	   |
  		 *	    | copy |
  		 *	    v	   v

  		 * RX SGL: AAD || PT || Tag

  		 */

  		err = crypto_aead_copy_sgl(null_tfm, tsgl_src,

  					   areq->first_rsgl.sgl.sg, processed);
  		if (err)
  			goto free;

  		af_alg_pull_tsgl(sk, processed, NULL, 0);

  	} else {
  		/*
  		 * Decryption operation - To achieve an in-place cipher
  		 * operation, the following  SGL structure is used:
  		 *
  		 * TX SGL: AAD || CT || Tag
  		 *	    |	   |	 ^
  		 *	    | copy |	 | Create SGL link.
  		 *	    v	   v	 |
  		 * RX SGL: AAD || CT ----+
  		 */
  
  		 /* Copy AAD || CT to RX SGL buffer for in-place operation. */

  		err = crypto_aead_copy_sgl(null_tfm, tsgl_src,

  					   areq->first_rsgl.sgl.sg, outlen);
  		if (err)
  			goto free;
  
  		/* Create TX SGL for tag and chain it to RX SGL. */

  		areq->tsgl_entries = af_alg_count_tsgl(sk, processed,
  						       processed - as);

  		if (!areq->tsgl_entries)
  			areq->tsgl_entries = 1;
  		areq->tsgl = sock_kmalloc(sk, sizeof(*areq->tsgl) *
  					      areq->tsgl_entries,
  					  GFP_KERNEL);
  		if (!areq->tsgl) {
  			err = -ENOMEM;
  			goto free;
  		}
  		sg_init_table(areq->tsgl, areq->tsgl_entries);
  
  		/* Release TX SGL, except for tag data and reassign tag data. */

  		af_alg_pull_tsgl(sk, processed, areq->tsgl, processed - as);

  
  		/* chain the areq TX SGL holding the tag with RX SGL */

  		if (usedpages) {

  			/* RX SGL present */

  			struct af_alg_sgl *sgl_prev = &areq->last_rsgl->sgl;

  
  			sg_unmark_end(sgl_prev->sg + sgl_prev->npages - 1);
  			sg_chain(sgl_prev->sg, sgl_prev->npages + 1,
  				 areq->tsgl);
  		} else
  			/* no RX SGL present (e.g. authentication only) */

  			rsgl_src = areq->tsgl;

  	}

  
  	/* Initialize the crypto operation */

  	aead_request_set_crypt(&areq->cra_u.aead_req, rsgl_src,

  			       areq->first_rsgl.sgl.sg, used, ctx->iv);

  	aead_request_set_ad(&areq->cra_u.aead_req, ctx->aead_assoclen);
  	aead_request_set_tfm(&areq->cra_u.aead_req, tfm);

  
  	if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) {
  		/* AIO operation */

  		sock_hold(sk);

  		areq->iocb = msg->msg_iocb;

  
  		/* Remember output size that will be generated. */
  		areq->outlen = outlen;

  		aead_request_set_callback(&areq->cra_u.aead_req,

  					  CRYPTO_TFM_REQ_MAY_BACKLOG,

  					  af_alg_async_cb, areq);
  		err = ctx->enc ? crypto_aead_encrypt(&areq->cra_u.aead_req) :
  				 crypto_aead_decrypt(&areq->cra_u.aead_req);

  
  		/* AIO operation in progress */

  		if (err == -EINPROGRESS || err == -EBUSY)

  			return -EIOCBQUEUED;

  
  		sock_put(sk);

  	} else {
  		/* Synchronous operation */

  		aead_request_set_callback(&areq->cra_u.aead_req,

  					  CRYPTO_TFM_REQ_MAY_BACKLOG,
  					  af_alg_complete, &ctx->completion);
  		err = af_alg_wait_for_completion(ctx->enc ?

  				crypto_aead_encrypt(&areq->cra_u.aead_req) :
  				crypto_aead_decrypt(&areq->cra_u.aead_req),
  						 &ctx->completion);

  	}

  
  free:

  	af_alg_free_resources(areq);

  
  	return err ? err : outlen;
  }

  static int aead_recvmsg(struct socket *sock, struct msghdr *msg,
  			size_t ignored, int flags)

  {

  	struct sock *sk = sock->sk;
  	int ret = 0;
  
  	lock_sock(sk);
  	while (msg_data_left(msg)) {
  		int err = _aead_recvmsg(sock, msg, ignored, flags);
  
  		/*
  		 * This error covers -EIOCBQUEUED which implies that we can
  		 * only handle one AIO request. If the caller wants to have
  		 * multiple AIO requests in parallel, he must make multiple
  		 * separate AIO calls.

  		 *
  		 * Also return the error if no data has been processed so far.

  		 */
  		if (err <= 0) {

  			if (err == -EIOCBQUEUED || err == -EBADMSG || !ret)

  				ret = err;
  			goto out;
  		}
  
  		ret += err;
  	}
  
  out:

  	af_alg_wmem_wakeup(sk);

  	release_sock(sk);
  	return ret;

  }

  static struct proto_ops algif_aead_ops = {
  	.family		=	PF_ALG,
  
  	.connect	=	sock_no_connect,
  	.socketpair	=	sock_no_socketpair,
  	.getname	=	sock_no_getname,
  	.ioctl		=	sock_no_ioctl,
  	.listen		=	sock_no_listen,
  	.shutdown	=	sock_no_shutdown,
  	.getsockopt	=	sock_no_getsockopt,
  	.mmap		=	sock_no_mmap,
  	.bind		=	sock_no_bind,
  	.accept		=	sock_no_accept,
  	.setsockopt	=	sock_no_setsockopt,
  
  	.release	=	af_alg_release,
  	.sendmsg	=	aead_sendmsg,

  	.sendpage	=	af_alg_sendpage,

  	.recvmsg	=	aead_recvmsg,

  	.poll		=	af_alg_poll,

  };

  static int aead_check_key(struct socket *sock)
  {
  	int err = 0;
  	struct sock *psk;
  	struct alg_sock *pask;
  	struct aead_tfm *tfm;
  	struct sock *sk = sock->sk;
  	struct alg_sock *ask = alg_sk(sk);
  
  	lock_sock(sk);
  	if (ask->refcnt)
  		goto unlock_child;
  
  	psk = ask->parent;
  	pask = alg_sk(ask->parent);
  	tfm = pask->private;
  
  	err = -ENOKEY;
  	lock_sock_nested(psk, SINGLE_DEPTH_NESTING);
  	if (!tfm->has_key)
  		goto unlock;
  
  	if (!pask->refcnt++)
  		sock_hold(psk);
  
  	ask->refcnt = 1;
  	sock_put(psk);
  
  	err = 0;
  
  unlock:
  	release_sock(psk);
  unlock_child:
  	release_sock(sk);
  
  	return err;
  }
  
  static int aead_sendmsg_nokey(struct socket *sock, struct msghdr *msg,
  				  size_t size)
  {
  	int err;
  
  	err = aead_check_key(sock);
  	if (err)
  		return err;
  
  	return aead_sendmsg(sock, msg, size);
  }
  
  static ssize_t aead_sendpage_nokey(struct socket *sock, struct page *page,
  				       int offset, size_t size, int flags)
  {
  	int err;
  
  	err = aead_check_key(sock);
  	if (err)
  		return err;

  	return af_alg_sendpage(sock, page, offset, size, flags);

  }
  
  static int aead_recvmsg_nokey(struct socket *sock, struct msghdr *msg,
  				  size_t ignored, int flags)
  {
  	int err;
  
  	err = aead_check_key(sock);
  	if (err)
  		return err;
  
  	return aead_recvmsg(sock, msg, ignored, flags);
  }
  
  static struct proto_ops algif_aead_ops_nokey = {
  	.family		=	PF_ALG,
  
  	.connect	=	sock_no_connect,
  	.socketpair	=	sock_no_socketpair,
  	.getname	=	sock_no_getname,
  	.ioctl		=	sock_no_ioctl,
  	.listen		=	sock_no_listen,
  	.shutdown	=	sock_no_shutdown,
  	.getsockopt	=	sock_no_getsockopt,
  	.mmap		=	sock_no_mmap,
  	.bind		=	sock_no_bind,
  	.accept		=	sock_no_accept,
  	.setsockopt	=	sock_no_setsockopt,
  
  	.release	=	af_alg_release,
  	.sendmsg	=	aead_sendmsg_nokey,
  	.sendpage	=	aead_sendpage_nokey,
  	.recvmsg	=	aead_recvmsg_nokey,

  	.poll		=	af_alg_poll,

  };

  static void *aead_bind(const char *name, u32 type, u32 mask)
  {

  	struct aead_tfm *tfm;
  	struct crypto_aead *aead;

  	struct crypto_skcipher *null_tfm;

  
  	tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
  	if (!tfm)
  		return ERR_PTR(-ENOMEM);
  
  	aead = crypto_alloc_aead(name, type, mask);
  	if (IS_ERR(aead)) {
  		kfree(tfm);
  		return ERR_CAST(aead);
  	}

  	null_tfm = crypto_get_default_null_skcipher2();
  	if (IS_ERR(null_tfm)) {
  		crypto_free_aead(aead);
  		kfree(tfm);
  		return ERR_CAST(null_tfm);
  	}

  	tfm->aead = aead;

  	tfm->null_tfm = null_tfm;

  
  	return tfm;

  }
  
  static void aead_release(void *private)
  {

  	struct aead_tfm *tfm = private;
  
  	crypto_free_aead(tfm->aead);

  	crypto_put_default_null_skcipher2();

  	kfree(tfm);

  }
  
  static int aead_setauthsize(void *private, unsigned int authsize)
  {

  	struct aead_tfm *tfm = private;
  
  	return crypto_aead_setauthsize(tfm->aead, authsize);

  }
  
  static int aead_setkey(void *private, const u8 *key, unsigned int keylen)
  {

  	struct aead_tfm *tfm = private;
  	int err;
  
  	err = crypto_aead_setkey(tfm->aead, key, keylen);
  	tfm->has_key = !err;
  
  	return err;

  }
  
  static void aead_sock_destruct(struct sock *sk)
  {
  	struct alg_sock *ask = alg_sk(sk);

  	struct af_alg_ctx *ctx = ask->private;

  	struct sock *psk = ask->parent;
  	struct alg_sock *pask = alg_sk(psk);
  	struct aead_tfm *aeadc = pask->private;
  	struct crypto_aead *tfm = aeadc->aead;
  	unsigned int ivlen = crypto_aead_ivsize(tfm);

  	af_alg_pull_tsgl(sk, ctx->used, NULL, 0);

  	sock_kzfree_s(sk, ctx->iv, ivlen);
  	sock_kfree_s(sk, ctx, ctx->len);
  	af_alg_release_parent(sk);
  }

  static int aead_accept_parent_nokey(void *private, struct sock *sk)

  {

  	struct af_alg_ctx *ctx;

  	struct alg_sock *ask = alg_sk(sk);

  	struct aead_tfm *tfm = private;
  	struct crypto_aead *aead = tfm->aead;

  	unsigned int len = sizeof(*ctx);

  	unsigned int ivlen = crypto_aead_ivsize(aead);

  
  	ctx = sock_kmalloc(sk, len, GFP_KERNEL);
  	if (!ctx)
  		return -ENOMEM;
  	memset(ctx, 0, len);
  
  	ctx->iv = sock_kmalloc(sk, ivlen, GFP_KERNEL);
  	if (!ctx->iv) {
  		sock_kfree_s(sk, ctx, len);
  		return -ENOMEM;
  	}
  	memset(ctx->iv, 0, ivlen);

  	INIT_LIST_HEAD(&ctx->tsgl_list);

  	ctx->len = len;
  	ctx->used = 0;

  	atomic_set(&ctx->rcvused, 0);

  	ctx->more = 0;
  	ctx->merge = 0;
  	ctx->enc = 0;

  	ctx->aead_assoclen = 0;
  	af_alg_init_completion(&ctx->completion);

  
  	ask->private = ctx;

  	sk->sk_destruct = aead_sock_destruct;
  
  	return 0;
  }

  static int aead_accept_parent(void *private, struct sock *sk)
  {
  	struct aead_tfm *tfm = private;
  
  	if (!tfm->has_key)
  		return -ENOKEY;
  
  	return aead_accept_parent_nokey(private, sk);
  }

  static const struct af_alg_type algif_type_aead = {
  	.bind		=	aead_bind,
  	.release	=	aead_release,
  	.setkey		=	aead_setkey,
  	.setauthsize	=	aead_setauthsize,
  	.accept		=	aead_accept_parent,

  	.accept_nokey	=	aead_accept_parent_nokey,

  	.ops		=	&algif_aead_ops,

  	.ops_nokey	=	&algif_aead_ops_nokey,

  	.name		=	"aead",
  	.owner		=	THIS_MODULE
  };
  
  static int __init algif_aead_init(void)
  {
  	return af_alg_register_type(&algif_type_aead);
  }
  
  static void __exit algif_aead_exit(void)
  {
  	int err = af_alg_unregister_type(&algif_type_aead);
  	BUG_ON(err);
  }
  
  module_init(algif_aead_init);
  module_exit(algif_aead_exit);
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
  MODULE_DESCRIPTION("AEAD kernel crypto API user space interface");