crypto: algif - add AEAD support

/*

 * 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

	 * bytes

	 */

#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 kiocb *unused, 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 kiocb *unused, 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 initial list */

		if (cnt)

			scatterwalk_crypto_chain(ctx->rsgl[0].sg,

					ctx->rsgl[cnt].sg, 1,

					sg_nents(ctx->rsgl[cnt-1].sg));

		/* 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");