[PATCH v4 3/7] crypto: AF_ALG -- add asymmetric cipher interface

[Tadeusz Struk]

From: Stephan Mueller <smueller@xxxxxxxxxx>

This patch adds the user space interface for asymmetric ciphers. The
interface allows the use of sendmsg as well as vmsplice to provide data.

This version has been rebased on top of 4.6 and a few chackpatch issues
have been fixed.

Signed-off-by: Stephan Mueller <smueller@xxxxxxxxxx>
Signed-off-by: Tadeusz Struk <tadeusz.struk@xxxxxxxxx>
---
 crypto/algif_akcipher.c |  542 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 542 insertions(+)
 create mode 100644 crypto/algif_akcipher.c

diff --git a/crypto/algif_akcipher.c b/crypto/algif_akcipher.c
new file mode 100644
index 0000000..6342b6e
--- /dev/null
+++ b/crypto/algif_akcipher.c
@@ -0,0 +1,542 @@
+/*
+ * algif_akcipher: User-space interface for asymmetric cipher algorithms
+ *
+ * Copyright (C) 2015, Stephan Mueller <smueller@xxxxxxxxxx>
+ *
+ * This file provides the user-space API for asymmetric 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.
+ */
+
+#include <crypto/akcipher.h>
+#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 akcipher_sg_list {
+	unsigned int cur;
+	struct scatterlist sg[ALG_MAX_PAGES];
+};
+
+struct akcipher_ctx {
+	struct akcipher_sg_list tsgl;
+	struct af_alg_sgl rsgl[ALG_MAX_PAGES];
+
+	struct af_alg_completion completion;
+
+	unsigned long used;
+
+	unsigned int len;
+	bool more;
+	bool merge;
+	int op;
+
+	struct akcipher_request req;
+};
+
+static inline int akcipher_sndbuf(struct sock *sk)
+{
+	struct alg_sock *ask = alg_sk(sk);
+	struct akcipher_ctx *ctx = ask->private;
+
+	return max_t(int, max_t(int, sk->sk_sndbuf & PAGE_MASK, PAGE_SIZE) -
+			  ctx->used, 0);
+}
+
+static inline bool akcipher_writable(struct sock *sk)
+{
+	return akcipher_sndbuf(sk) >= PAGE_SIZE;
+}
+
+static inline int akcipher_calcsize(struct akcipher_ctx *ctx)
+{
+	return crypto_akcipher_maxsize(crypto_akcipher_reqtfm(&ctx->req));
+}
+
+static void akcipher_put_sgl(struct sock *sk)
+{
+	struct alg_sock *ask = alg_sk(sk);
+	struct akcipher_ctx *ctx = ask->private;
+	struct akcipher_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);
+	}
+	sg_init_table(sg, ALG_MAX_PAGES);
+	sgl->cur = 0;
+	ctx->used = 0;
+	ctx->more = 0;
+	ctx->merge = 0;
+}
+
+static void akcipher_wmem_wakeup(struct sock *sk)
+{
+	struct socket_wq *wq;
+
+	if (!akcipher_writable(sk))
+		return;
+
+	rcu_read_lock();
+	wq = rcu_dereference(sk->sk_wq);
+	if (wq_has_sleeper(&wq->wait))
+		wake_up_interruptible_sync_poll(&wq->wait, POLLIN |
+							   POLLRDNORM |
+							   POLLRDBAND);
+	sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
+	rcu_read_unlock();
+}
+
+static int akcipher_wait_for_data(struct sock *sk, unsigned int flags)
+{
+	struct alg_sock *ask = alg_sk(sk);
+	struct akcipher_ctx *ctx = ask->private;
+	long timeout;
+	DEFINE_WAIT(wait);
+	int err = -ERESTARTSYS;
+
+	if (flags & MSG_DONTWAIT)
+		return -EAGAIN;
+
+	set_bit(SOCKWQ_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(SOCKWQ_ASYNC_WAITDATA, &sk->sk_socket->flags);
+
+	return err;
+}
+
+static void akcipher_data_wakeup(struct sock *sk)
+{
+	struct alg_sock *ask = alg_sk(sk);
+	struct akcipher_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->wait))
+		wake_up_interruptible_sync_poll(&wq->wait, POLLOUT |
+							   POLLRDNORM |
+							   POLLRDBAND);
+	sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
+	rcu_read_unlock();
+}
+
+static int akcipher_sendmsg(struct socket *sock, struct msghdr *msg,
+			    size_t size)
+{
+	struct sock *sk = sock->sk;
+	struct alg_sock *ask = alg_sk(sk);
+	struct akcipher_ctx *ctx = ask->private;
+	struct akcipher_sg_list *sgl = &ctx->tsgl;
+	struct af_alg_control con = {};
+	long copied = 0;
+	int op = 0;
+	bool init = 0;
+	int err;
+
+	if (msg->msg_controllen) {
+		err = af_alg_cmsg_send(msg, &con);
+		if (err)
+			return err;
+
+		init = 1;
+		switch (con.op) {
+		case ALG_OP_VERIFY:
+		case ALG_OP_SIGN:
+		case ALG_OP_ENCRYPT:
+		case ALG_OP_DECRYPT:
+			op = con.op;
+			break;
+		default:
+			return -EINVAL;
+		}
+	}
+
+	lock_sock(sk);
+	if (!ctx->more && ctx->used)
+		goto unlock;
+
+	if (init)
+		ctx->op = op;
+
+	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 (!akcipher_writable(sk)) {
+			/* user space sent too much data */
+			akcipher_put_sgl(sk);
+			err = -EMSGSIZE;
+			goto unlock;
+		}
+
+		/* allocate a new page */
+		len = min_t(unsigned long, size, akcipher_sndbuf(sk));
+		while (len) {
+			int plen = 0;
+
+			if (sgl->cur >= ALG_MAX_PAGES) {
+				akcipher_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));
+			if (!sg_page(sg)) {
+				err = -ENOMEM;
+				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;
+
+unlock:
+	akcipher_data_wakeup(sk);
+	release_sock(sk);
+
+	return err ?: copied;
+}
+
+static ssize_t akcipher_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 akcipher_ctx *ctx = ask->private;
+	struct akcipher_sg_list *sgl = &ctx->tsgl;
+	int err = 0;
+
+	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 (!akcipher_writable(sk)) {
+		/* user space sent too much data */
+		akcipher_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;
+
+done:
+	ctx->more = flags & MSG_MORE;
+unlock:
+	akcipher_data_wakeup(sk);
+	release_sock(sk);
+
+	return err ? err : size;
+}
+
+static int akcipher_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 akcipher_ctx *ctx = ask->private;
+	struct akcipher_sg_list *sgl = &ctx->tsgl;
+	unsigned int i = 0;
+	int err;
+	unsigned long used = 0;
+	size_t usedpages = 0;
+	unsigned int cnt = 0;
+
+	/* Limit number of IOV blocks to be accessed below */
+	if (msg->msg_iter.nr_segs > ALG_MAX_PAGES)
+		return -ENOMSG;
+
+	lock_sock(sk);
+
+	if (ctx->more) {
+		err = akcipher_wait_for_data(sk, flags);
+		if (err)
+			goto unlock;
+	}
+
+	used = ctx->used;
+
+	/* convert iovecs of output buffers into scatterlists */
+	while (iov_iter_count(&msg->msg_iter)) {
+		/* make one iovec available as scatterlist */
+		err = af_alg_make_sg(&ctx->rsgl[cnt], &msg->msg_iter,
+				     iov_iter_count(&msg->msg_iter));
+		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]);
+
+		iov_iter_advance(&msg->msg_iter, err);
+		cnt++;
+	}
+
+	/* ensure output buffer is sufficiently large */
+	if (usedpages < akcipher_calcsize(ctx)) {
+		err = -EMSGSIZE;
+		goto unlock;
+	}
+
+	sg_mark_end(sgl->sg + sgl->cur - 1);
+
+	akcipher_request_set_crypt(&ctx->req, sgl->sg, ctx->rsgl[0].sg, used,
+				   usedpages);
+	switch (ctx->op) {
+	case ALG_OP_VERIFY:
+		err = crypto_akcipher_verify(&ctx->req);
+		break;
+	case ALG_OP_SIGN:
+		err = crypto_akcipher_sign(&ctx->req);
+		break;
+	case ALG_OP_ENCRYPT:
+		err = crypto_akcipher_encrypt(&ctx->req);
+		break;
+	case ALG_OP_DECRYPT:
+		err = crypto_akcipher_decrypt(&ctx->req);
+		break;
+	default:
+		err = -EFAULT;
+		goto unlock;
+	}
+
+	err = af_alg_wait_for_completion(err, &ctx->completion);
+
+	if (err) {
+		/* EBADMSG implies a valid cipher operation took place */
+		if (err == -EBADMSG)
+			akcipher_put_sgl(sk);
+		goto unlock;
+	}
+
+	akcipher_put_sgl(sk);
+
+unlock:
+	for (i = 0; i < cnt; i++)
+		af_alg_free_sg(&ctx->rsgl[i]);
+
+	akcipher_wmem_wakeup(sk);
+	release_sock(sk);
+
+	return err ? err : ctx->req.dst_len;
+}
+
+static unsigned int akcipher_poll(struct file *file, struct socket *sock,
+				  poll_table *wait)
+{
+	struct sock *sk = sock->sk;
+	struct alg_sock *ask = alg_sk(sk);
+	struct akcipher_ctx *ctx = ask->private;
+	unsigned int mask = 0;
+
+	sock_poll_wait(file, sk_sleep(sk), wait);
+
+	if (!ctx->more)
+		mask |= POLLIN | POLLRDNORM;
+
+	if (akcipher_writable(sk))
+		mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
+
+	return mask;
+}
+
+static struct proto_ops algif_akcipher_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	=	akcipher_sendmsg,
+	.sendpage	=	akcipher_sendpage,
+	.recvmsg	=	akcipher_recvmsg,
+	.poll		=	akcipher_poll,
+};
+
+static void *akcipher_bind(const char *name, u32 type, u32 mask)
+{
+	return crypto_alloc_akcipher(name, type, mask);
+}
+
+static void akcipher_release(void *private)
+{
+	crypto_free_akcipher(private);
+}
+
+static int akcipher_setprivkey(void *private, const u8 *key,
+			       unsigned int keylen)
+{
+	return crypto_akcipher_set_priv_key(private, key, keylen);
+}
+
+static int akcipher_setpubkey(void *private, const u8 *key, unsigned int keylen)
+{
+	return crypto_akcipher_set_pub_key(private, key, keylen);
+}
+
+static void akcipher_sock_destruct(struct sock *sk)
+{
+	struct alg_sock *ask = alg_sk(sk);
+	struct akcipher_ctx *ctx = ask->private;
+
+	akcipher_put_sgl(sk);
+	sock_kfree_s(sk, ctx, ctx->len);
+	af_alg_release_parent(sk);
+}
+
+static int akcipher_accept_parent(void *private, struct sock *sk)
+{
+	struct akcipher_ctx *ctx;
+	struct alg_sock *ask = alg_sk(sk);
+	unsigned int len = sizeof(*ctx) + crypto_akcipher_reqsize(private);
+
+	ctx = sock_kmalloc(sk, len, GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+	memset(ctx, 0, len);
+
+	ctx->len = len;
+	ctx->used = 0;
+	ctx->more = 0;
+	ctx->merge = 0;
+	ctx->op = 0;
+	ctx->tsgl.cur = 0;
+	af_alg_init_completion(&ctx->completion);
+	sg_init_table(ctx->tsgl.sg, ALG_MAX_PAGES);
+
+	ask->private = ctx;
+
+	akcipher_request_set_tfm(&ctx->req, private);
+	akcipher_request_set_callback(&ctx->req, CRYPTO_TFM_REQ_MAY_BACKLOG,
+				      af_alg_complete, &ctx->completion);
+
+	sk->sk_destruct = akcipher_sock_destruct;
+
+	return 0;
+}
+
+static const struct af_alg_type algif_type_akcipher = {
+	.bind		=	akcipher_bind,
+	.release	=	akcipher_release,
+	.setkey		=	akcipher_setprivkey,
+	.setpubkey	=	akcipher_setpubkey,
+	.accept		=	akcipher_accept_parent,
+	.ops		=	&algif_akcipher_ops,
+	.name		=	"akcipher",
+	.owner		=	THIS_MODULE
+};
+
+static int __init algif_akcipher_init(void)
+{
+	return af_alg_register_type(&algif_type_akcipher);
+}
+
+static void __exit algif_akcipher_exit(void)
+{
+	int err = af_alg_unregister_type(&algif_type_akcipher);
+
+	WARN_ON(err);
+}
+
+module_init(algif_akcipher_init);
+module_exit(algif_akcipher_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Stephan Mueller <smueller@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Asymmetric kernel crypto API user space interface");