/*
   * 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 file is derived from algif_skcipher.c.
   *
   * 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/scatterwalk.h>
  #include <crypto/if_alg.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_sg_list {
  	unsigned int cur;
  	struct scatterlist sg[ALG_MAX_PAGES];
  };
  
  struct aead_ctx {
  	struct aead_sg_list tsgl;
  	/*
  	 * RSGL_MAX_ENTRIES is an artificial limit where user space at maximum
  	 * can cause the kernel to allocate RSGL_MAX_ENTRIES * ALG_MAX_PAGES

  	 * pages

  	 */
  #define RSGL_MAX_ENTRIES ALG_MAX_PAGES
  	struct af_alg_sgl rsgl[RSGL_MAX_ENTRIES];
  
  	void *iv;
  
  	struct af_alg_completion completion;
  
  	unsigned long used;
  
  	unsigned int len;
  	bool more;
  	bool merge;
  	bool enc;
  
  	size_t aead_assoclen;
  	struct aead_request aead_req;
  };
  
  static inline int aead_sndbuf(struct sock *sk)
  {
  	struct alg_sock *ask = alg_sk(sk);
  	struct aead_ctx *ctx = ask->private;
  
  	return max_t(int, max_t(int, sk->sk_sndbuf & PAGE_MASK, PAGE_SIZE) -
  			  ctx->used, 0);
  }
  
  static inline bool aead_writable(struct sock *sk)
  {
  	return PAGE_SIZE <= aead_sndbuf(sk);
  }
  
  static inline bool aead_sufficient_data(struct aead_ctx *ctx)
  {
  	unsigned as = crypto_aead_authsize(crypto_aead_reqtfm(&ctx->aead_req));
  
  	return (ctx->used >= (ctx->aead_assoclen + (ctx->enc ? 0 : as)));
  }
  
  static void aead_put_sgl(struct sock *sk)
  {
  	struct alg_sock *ask = alg_sk(sk);
  	struct aead_ctx *ctx = ask->private;
  	struct aead_sg_list *sgl = &ctx->tsgl;
  	struct scatterlist *sg = sgl->sg;
  	unsigned int i;
  
  	for (i = 0; i < sgl->cur; i++) {
  		if (!sg_page(sg + i))
  			continue;
  
  		put_page(sg_page(sg + i));
  		sg_assign_page(sg + i, NULL);
  	}
  	sgl->cur = 0;
  	ctx->used = 0;
  	ctx->more = 0;
  	ctx->merge = 0;
  }
  
  static void aead_wmem_wakeup(struct sock *sk)
  {
  	struct socket_wq *wq;
  
  	if (!aead_writable(sk))
  		return;
  
  	rcu_read_lock();
  	wq = rcu_dereference(sk->sk_wq);
  	if (wq_has_sleeper(wq))
  		wake_up_interruptible_sync_poll(&wq->wait, POLLIN |
  							   POLLRDNORM |
  							   POLLRDBAND);
  	sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
  	rcu_read_unlock();
  }
  
  static int aead_wait_for_data(struct sock *sk, unsigned flags)
  {
  	struct alg_sock *ask = alg_sk(sk);
  	struct aead_ctx *ctx = ask->private;
  	long timeout;
  	DEFINE_WAIT(wait);
  	int err = -ERESTARTSYS;
  
  	if (flags & MSG_DONTWAIT)
  		return -EAGAIN;
  
  	set_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
  
  	for (;;) {
  		if (signal_pending(current))
  			break;
  		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
  		timeout = MAX_SCHEDULE_TIMEOUT;
  		if (sk_wait_event(sk, &timeout, !ctx->more)) {
  			err = 0;
  			break;
  		}
  	}
  	finish_wait(sk_sleep(sk), &wait);
  
  	clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
  
  	return err;
  }
  
  static void aead_data_wakeup(struct sock *sk)
  {
  	struct alg_sock *ask = alg_sk(sk);
  	struct aead_ctx *ctx = ask->private;
  	struct socket_wq *wq;
  
  	if (ctx->more)
  		return;
  	if (!ctx->used)
  		return;
  
  	rcu_read_lock();
  	wq = rcu_dereference(sk->sk_wq);
  	if (wq_has_sleeper(wq))
  		wake_up_interruptible_sync_poll(&wq->wait, POLLOUT |
  							   POLLRDNORM |
  							   POLLRDBAND);
  	sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
  	rcu_read_unlock();
  }

  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 aead_ctx *ctx = ask->private;
  	unsigned ivsize =
  		crypto_aead_ivsize(crypto_aead_reqtfm(&ctx->aead_req));
  	struct aead_sg_list *sgl = &ctx->tsgl;
  	struct af_alg_control con = {};
  	long copied = 0;
  	bool enc = 0;
  	bool init = 0;
  	int err = -EINVAL;
  
  	if (msg->msg_controllen) {
  		err = af_alg_cmsg_send(msg, &con);
  		if (err)
  			return err;
  
  		init = 1;
  		switch (con.op) {
  		case ALG_OP_ENCRYPT:
  			enc = 1;
  			break;
  		case ALG_OP_DECRYPT:
  			enc = 0;
  			break;
  		default:
  			return -EINVAL;
  		}
  
  		if (con.iv && con.iv->ivlen != ivsize)
  			return -EINVAL;
  	}
  
  	lock_sock(sk);
  	if (!ctx->more && ctx->used)
  		goto unlock;
  
  	if (init) {
  		ctx->enc = enc;
  		if (con.iv)
  			memcpy(ctx->iv, con.iv->iv, ivsize);
  
  		ctx->aead_assoclen = con.aead_assoclen;
  	}
  
  	while (size) {
  		unsigned long len = size;
  		struct scatterlist *sg = NULL;
  
  		/* use the existing memory in an allocated page */
  		if (ctx->merge) {
  			sg = sgl->sg + sgl->cur - 1;
  			len = min_t(unsigned long, len,
  				    PAGE_SIZE - sg->offset - sg->length);
  			err = memcpy_from_msg(page_address(sg_page(sg)) +
  					      sg->offset + sg->length,
  					      msg, len);
  			if (err)
  				goto unlock;
  
  			sg->length += len;
  			ctx->merge = (sg->offset + sg->length) &
  				     (PAGE_SIZE - 1);
  
  			ctx->used += len;
  			copied += len;
  			size -= len;
  			continue;
  		}
  
  		if (!aead_writable(sk)) {
  			/* user space sent too much data */
  			aead_put_sgl(sk);
  			err = -EMSGSIZE;
  			goto unlock;
  		}
  
  		/* allocate a new page */
  		len = min_t(unsigned long, size, aead_sndbuf(sk));
  		while (len) {
  			int plen = 0;
  
  			if (sgl->cur >= ALG_MAX_PAGES) {
  				aead_put_sgl(sk);
  				err = -E2BIG;
  				goto unlock;
  			}
  
  			sg = sgl->sg + sgl->cur;
  			plen = min_t(int, len, PAGE_SIZE);
  
  			sg_assign_page(sg, alloc_page(GFP_KERNEL));
  			err = -ENOMEM;
  			if (!sg_page(sg))
  				goto unlock;
  
  			err = memcpy_from_msg(page_address(sg_page(sg)),
  					      msg, plen);
  			if (err) {
  				__free_page(sg_page(sg));
  				sg_assign_page(sg, NULL);
  				goto unlock;
  			}
  
  			sg->offset = 0;
  			sg->length = plen;
  			len -= plen;
  			ctx->used += plen;
  			copied += plen;
  			sgl->cur++;
  			size -= plen;
  			ctx->merge = plen & (PAGE_SIZE - 1);
  		}
  	}
  
  	err = 0;
  
  	ctx->more = msg->msg_flags & MSG_MORE;
  	if (!ctx->more && !aead_sufficient_data(ctx)) {
  		aead_put_sgl(sk);
  		err = -EMSGSIZE;
  	}
  
  unlock:
  	aead_data_wakeup(sk);
  	release_sock(sk);
  
  	return err ?: copied;
  }
  
  static ssize_t aead_sendpage(struct socket *sock, struct page *page,
  			     int offset, size_t size, int flags)
  {
  	struct sock *sk = sock->sk;
  	struct alg_sock *ask = alg_sk(sk);
  	struct aead_ctx *ctx = ask->private;
  	struct aead_sg_list *sgl = &ctx->tsgl;
  	int err = -EINVAL;
  
  	if (flags & MSG_SENDPAGE_NOTLAST)
  		flags |= MSG_MORE;
  
  	if (sgl->cur >= ALG_MAX_PAGES)
  		return -E2BIG;
  
  	lock_sock(sk);
  	if (!ctx->more && ctx->used)
  		goto unlock;
  
  	if (!size)
  		goto done;
  
  	if (!aead_writable(sk)) {
  		/* user space sent too much data */
  		aead_put_sgl(sk);
  		err = -EMSGSIZE;
  		goto unlock;
  	}
  
  	ctx->merge = 0;
  
  	get_page(page);
  	sg_set_page(sgl->sg + sgl->cur, page, size, offset);
  	sgl->cur++;
  	ctx->used += size;
  
  	err = 0;
  
  done:
  	ctx->more = flags & MSG_MORE;
  	if (!ctx->more && !aead_sufficient_data(ctx)) {
  		aead_put_sgl(sk);
  		err = -EMSGSIZE;
  	}
  
  unlock:
  	aead_data_wakeup(sk);
  	release_sock(sk);
  
  	return err ?: size;
  }

  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 aead_ctx *ctx = ask->private;
  	unsigned bs = crypto_aead_blocksize(crypto_aead_reqtfm(&ctx->aead_req));
  	unsigned as = crypto_aead_authsize(crypto_aead_reqtfm(&ctx->aead_req));
  	struct aead_sg_list *sgl = &ctx->tsgl;
  	struct scatterlist *sg = NULL;
  	struct scatterlist assoc[ALG_MAX_PAGES];
  	size_t assoclen = 0;
  	unsigned int i = 0;
  	int err = -EINVAL;
  	unsigned long used = 0;
  	size_t outlen = 0;
  	size_t usedpages = 0;
  	unsigned int cnt = 0;
  
  	/* Limit number of IOV blocks to be accessed below */
  	if (msg->msg_iter.nr_segs > RSGL_MAX_ENTRIES)
  		return -ENOMSG;
  
  	lock_sock(sk);
  
  	/*
  	 * AEAD memory structure: For encryption, the tag is appended to the
  	 * ciphertext which implies that the memory allocated for the ciphertext
  	 * must be increased by the tag length. For decryption, the tag
  	 * is expected to be concatenated to the ciphertext. The plaintext
  	 * therefore has a memory size of the ciphertext minus the tag length.
  	 *
  	 * The memory structure for cipher operation has the following
  	 * structure:
  	 *	AEAD encryption input:  assoc data || plaintext
  	 *	AEAD encryption output: cipherntext || auth tag
  	 *	AEAD decryption input:  assoc data || ciphertext || auth tag
  	 *	AEAD decryption output: plaintext
  	 */
  
  	if (ctx->more) {
  		err = aead_wait_for_data(sk, flags);
  		if (err)
  			goto unlock;
  	}
  
  	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(ctx))
  		goto unlock;
  
  	/*
  	 * The cipher operation input data is reduced by the associated data
  	 * length as this data is processed separately later on.
  	 */
  	used -= ctx->aead_assoclen;
  
  	if (ctx->enc) {
  		/* round up output buffer to multiple of block size */
  		outlen = ((used + bs - 1) / bs * bs);
  		/* add the size needed for the auth tag to be created */
  		outlen += as;
  	} else {
  		/* output data size is input without the authentication tag */
  		outlen = used - as;
  		/* round up output buffer to multiple of block size */
  		outlen = ((outlen + bs - 1) / bs * bs);
  	}
  
  	/* convert iovecs of output buffers into scatterlists */
  	while (iov_iter_count(&msg->msg_iter)) {
  		size_t seglen = min_t(size_t, iov_iter_count(&msg->msg_iter),
  				      (outlen - usedpages));
  
  		/* make one iovec available as scatterlist */
  		err = af_alg_make_sg(&ctx->rsgl[cnt], &msg->msg_iter,
  				     seglen);
  		if (err < 0)
  			goto unlock;
  		usedpages += err;

  		/* chain the new scatterlist with previous one */

  		if (cnt)

  			af_alg_link_sg(&ctx->rsgl[cnt-1], &ctx->rsgl[cnt]);

  		/* we do not need more iovecs as we have sufficient memory */
  		if (outlen <= usedpages)
  			break;
  		iov_iter_advance(&msg->msg_iter, err);
  		cnt++;
  	}
  
  	err = -EINVAL;
  	/* ensure output buffer is sufficiently large */
  	if (usedpages < outlen)
  		goto unlock;
  
  	sg_init_table(assoc, ALG_MAX_PAGES);
  	assoclen = ctx->aead_assoclen;
  	/*
  	 * Split scatterlist into two: first part becomes AD, second part
  	 * is plaintext / ciphertext. The first part is assigned to assoc
  	 * scatterlist. When this loop finishes, sg points to the start of the
  	 * plaintext / ciphertext.
  	 */
  	for (i = 0; i < ctx->tsgl.cur; i++) {
  		sg = sgl->sg + i;
  		if (sg->length <= assoclen) {
  			/* AD is larger than one page */
  			sg_set_page(assoc + i, sg_page(sg),
  				    sg->length, sg->offset);
  			assoclen -= sg->length;
  			if (i >= ctx->tsgl.cur)
  				goto unlock;
  		} else if (!assoclen) {
  			/* current page is to start of plaintext / ciphertext */
  			if (i)
  				/* AD terminates at page boundary */
  				sg_mark_end(assoc + i - 1);
  			else
  				/* AD size is zero */
  				sg_mark_end(assoc);
  			break;
  		} else {
  			/* AD does not terminate at page boundary */
  			sg_set_page(assoc + i, sg_page(sg),
  				    assoclen, sg->offset);
  			sg_mark_end(assoc + i);
  			/* plaintext / ciphertext starts after AD */
  			sg->length -= assoclen;
  			sg->offset += assoclen;
  			break;
  		}
  	}
  
  	aead_request_set_assoc(&ctx->aead_req, assoc, ctx->aead_assoclen);
  	aead_request_set_crypt(&ctx->aead_req, sg, ctx->rsgl[0].sg, used,
  			       ctx->iv);
  
  	err = af_alg_wait_for_completion(ctx->enc ?
  					 crypto_aead_encrypt(&ctx->aead_req) :
  					 crypto_aead_decrypt(&ctx->aead_req),
  					 &ctx->completion);
  
  	if (err) {
  		/* EBADMSG implies a valid cipher operation took place */
  		if (err == -EBADMSG)
  			aead_put_sgl(sk);
  		goto unlock;
  	}
  
  	aead_put_sgl(sk);
  
  	err = 0;
  
  unlock:
  	for (i = 0; i < cnt; i++)
  		af_alg_free_sg(&ctx->rsgl[i]);
  
  	aead_wmem_wakeup(sk);
  	release_sock(sk);
  
  	return err ? err : outlen;
  }
  
  static unsigned int aead_poll(struct file *file, struct socket *sock,
  			      poll_table *wait)
  {
  	struct sock *sk = sock->sk;
  	struct alg_sock *ask = alg_sk(sk);
  	struct aead_ctx *ctx = ask->private;
  	unsigned int mask;
  
  	sock_poll_wait(file, sk_sleep(sk), wait);
  	mask = 0;
  
  	if (!ctx->more)
  		mask |= POLLIN | POLLRDNORM;
  
  	if (aead_writable(sk))
  		mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
  
  	return mask;
  }
  
  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	=	aead_sendpage,
  	.recvmsg	=	aead_recvmsg,
  	.poll		=	aead_poll,
  };
  
  static void *aead_bind(const char *name, u32 type, u32 mask)
  {
  	return crypto_alloc_aead(name, type, mask);
  }
  
  static void aead_release(void *private)
  {
  	crypto_free_aead(private);
  }
  
  static int aead_setauthsize(void *private, unsigned int authsize)
  {
  	return crypto_aead_setauthsize(private, authsize);
  }
  
  static int aead_setkey(void *private, const u8 *key, unsigned int keylen)
  {
  	return crypto_aead_setkey(private, key, keylen);
  }
  
  static void aead_sock_destruct(struct sock *sk)
  {
  	struct alg_sock *ask = alg_sk(sk);
  	struct aead_ctx *ctx = ask->private;
  	unsigned int ivlen = crypto_aead_ivsize(
  				crypto_aead_reqtfm(&ctx->aead_req));
  
  	aead_put_sgl(sk);
  	sock_kzfree_s(sk, ctx->iv, ivlen);
  	sock_kfree_s(sk, ctx, ctx->len);
  	af_alg_release_parent(sk);
  }
  
  static int aead_accept_parent(void *private, struct sock *sk)
  {
  	struct aead_ctx *ctx;
  	struct alg_sock *ask = alg_sk(sk);
  	unsigned int len = sizeof(*ctx) + crypto_aead_reqsize(private);
  	unsigned int ivlen = crypto_aead_ivsize(private);
  
  	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);
  
  	ctx->len = len;
  	ctx->used = 0;
  	ctx->more = 0;
  	ctx->merge = 0;
  	ctx->enc = 0;
  	ctx->tsgl.cur = 0;
  	ctx->aead_assoclen = 0;
  	af_alg_init_completion(&ctx->completion);
  	sg_init_table(ctx->tsgl.sg, ALG_MAX_PAGES);
  
  	ask->private = ctx;
  
  	aead_request_set_tfm(&ctx->aead_req, private);
  	aead_request_set_callback(&ctx->aead_req, CRYPTO_TFM_REQ_MAY_BACKLOG,
  				  af_alg_complete, &ctx->completion);
  
  	sk->sk_destruct = aead_sock_destruct;
  
  	return 0;
  }
  
  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,
  	.ops		=	&algif_aead_ops,
  	.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");