[PATCH v8 3/4] crypto: AF_ALG -- add asymmetric cipher

["Stephan Müller" <smueller@chronox.de>]

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

The akcipher interface implementation uses the common AF_ALG interface
code regarding TX and RX SGL handling.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
---
 crypto/algif_akcipher.c | 466 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/crypto/if_alg.h |   2 +
 2 files changed, 468 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 000000000000..1b36eb0b6e8f
--- /dev/null
+++ b/crypto/algif_akcipher.c
@@ -0,0 +1,466 @@
+/*
+ * algif_akcipher: User-space interface for asymmetric cipher algorithms
+ *
+ * Copyright (C) 2017, Stephan Mueller <smueller@chronox.de>
+ *
+ * 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.
+ *
+ * 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/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_tfm {
+	struct crypto_akcipher *akcipher;
+	bool has_key;
+};
+
+static int akcipher_sendmsg(struct socket *sock, struct msghdr *msg,
+			    size_t size)
+{
+	return af_alg_sendmsg(sock, msg, size, 0);
+}
+
+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 sock *psk = ask->parent;
+	struct alg_sock *pask = alg_sk(psk);
+	struct af_alg_ctx *ctx = ask->private;
+	struct akcipher_tfm *akc = pask->private;
+	struct crypto_akcipher *tfm = akc->akcipher;
+	struct af_alg_async_req *areq;
+	int err = 0;
+	int maxsize;
+	size_t len = 0;
+	size_t used = 0;
+
+	maxsize = crypto_akcipher_maxsize(tfm);
+	if (maxsize < 0)
+		return maxsize;
+
+	/* Allocate cipher request for current operation. */
+	areq = af_alg_alloc_areq(sk, sizeof(struct af_alg_async_req) +
+				     crypto_akcipher_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, maxsize, &len);
+	if (err)
+		goto free;
+
+	/* ensure output buffer is sufficiently large */
+	if (len < maxsize) {
+		err = -EMSGSIZE;
+		goto free;
+	}
+
+	/*
+	 * Create a per request TX SGL for this request which tracks the
+	 * SG entries from the global TX SGL.
+	 */
+	used = ctx->used;
+	areq->tsgl_entries = af_alg_count_tsgl(sk, used, 0);
+	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);
+	af_alg_pull_tsgl(sk, used, areq->tsgl, 0);
+
+	/* Initialize the crypto operation */
+	akcipher_request_set_tfm(&areq->cra_u.akcipher_req, tfm);
+	akcipher_request_set_crypt(&areq->cra_u.akcipher_req, areq->tsgl,
+				   areq->first_rsgl.sgl.sg, used, len);
+
+	if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) {
+		/* AIO operation */
+		areq->iocb = msg->msg_iocb;
+		akcipher_request_set_callback(&areq->cra_u.akcipher_req,
+					      CRYPTO_TFM_REQ_MAY_SLEEP,
+					      af_alg_async_cb, areq);
+	} else
+		/* Synchronous operation */
+		akcipher_request_set_callback(&areq->cra_u.akcipher_req,
+					      CRYPTO_TFM_REQ_MAY_SLEEP |
+					      CRYPTO_TFM_REQ_MAY_BACKLOG,
+					      af_alg_complete,
+					      &ctx->completion);
+
+	switch (ctx->op) {
+	case ALG_OP_ENCRYPT:
+		err = crypto_akcipher_encrypt(&areq->cra_u.akcipher_req);
+		break;
+	case ALG_OP_DECRYPT:
+		err = crypto_akcipher_decrypt(&areq->cra_u.akcipher_req);
+		break;
+	case ALG_OP_SIGN:
+		err = crypto_akcipher_sign(&areq->cra_u.akcipher_req);
+		break;
+	case ALG_OP_VERIFY:
+		err = crypto_akcipher_verify(&areq->cra_u.akcipher_req);
+		break;
+	default:
+		err = -EOPNOTSUPP;
+		goto free;
+	}
+
+	/* Wait for synchronous operation completion */
+	if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb))
+		err = af_alg_wait_for_completion(err, &ctx->completion);
+
+	/* AIO operation in progress */
+	if (err == -EINPROGRESS) {
+		sock_hold(sk);
+
+		/* Remember output size that will be generated. */
+		areq->outlen = areq->cra_u.akcipher_req.dst_len;
+
+		return -EIOCBQUEUED;
+	}
+
+free:
+	af_alg_free_areq_sgls(areq);
+	sock_kfree_s(sk, areq, areq->areqlen);
+
+	return err ? err : areq->cra_u.akcipher_req.dst_len;
+}
+
+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 sock *psk = ask->parent;
+	struct alg_sock *pask = alg_sk(psk);
+	struct akcipher_tfm *akc = pask->private;
+	struct crypto_akcipher *tfm = akc->akcipher;
+
+	int ret = 0;
+
+	lock_sock(sk);
+
+	while (msg_data_left(msg)) {
+		int err = _akcipher_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.
+		 */
+		if (err <= 0) {
+			if (err == -EIOCBQUEUED || err == -EBADMSG || !ret)
+				ret = err;
+			goto out;
+		}
+
+		ret += err;
+
+		/*
+		 * The caller must provide crypto_akcipher_maxsize per request.
+		 * If he provides more, we conclude that multiple akcipher
+		 * operations are requested.
+		 */
+		iov_iter_advance(&msg->msg_iter,
+				 crypto_akcipher_maxsize(tfm) - err);
+	}
+
+out:
+	af_alg_wmem_wakeup(sk);
+	release_sock(sk);
+	return ret;
+}
+
+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	=	af_alg_sendpage,
+	.recvmsg	=	akcipher_recvmsg,
+	.poll		=	af_alg_poll,
+};
+
+static int akcipher_check_key(struct socket *sock)
+{
+	int err = 0;
+	struct sock *psk;
+	struct alg_sock *pask;
+	struct akcipher_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 akcipher_sendmsg_nokey(struct socket *sock, struct msghdr *msg,
+				  size_t size)
+{
+	int err;
+
+	err = akcipher_check_key(sock);
+	if (err)
+		return err;
+
+	return akcipher_sendmsg(sock, msg, size);
+}
+
+static ssize_t akcipher_sendpage_nokey(struct socket *sock, struct page *page,
+				       int offset, size_t size, int flags)
+{
+	int err;
+
+	err = akcipher_check_key(sock);
+	if (err)
+		return err;
+
+	return af_alg_sendpage(sock, page, offset, size, flags);
+}
+
+static int akcipher_recvmsg_nokey(struct socket *sock, struct msghdr *msg,
+				  size_t ignored, int flags)
+{
+	int err;
+
+	err = akcipher_check_key(sock);
+	if (err)
+		return err;
+
+	return akcipher_recvmsg(sock, msg, ignored, flags);
+}
+
+static struct proto_ops algif_akcipher_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	=	akcipher_sendmsg_nokey,
+	.sendpage	=	akcipher_sendpage_nokey,
+	.recvmsg	=	akcipher_recvmsg_nokey,
+	.poll		=	af_alg_poll,
+};
+
+static void *akcipher_bind(const char *name, u32 type, u32 mask)
+{
+	struct akcipher_tfm *tfm;
+	struct crypto_akcipher *akcipher;
+
+	tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
+	if (!tfm)
+		return ERR_PTR(-ENOMEM);
+
+	akcipher = crypto_alloc_akcipher(name, type, mask);
+	if (IS_ERR(akcipher)) {
+		kfree(tfm);
+		return ERR_CAST(akcipher);
+	}
+
+	tfm->akcipher = akcipher;
+
+	return tfm;
+}
+
+static void akcipher_release(void *private)
+{
+	struct akcipher_tfm *tfm = private;
+	struct crypto_akcipher *akcipher = tfm->akcipher;
+
+	crypto_free_akcipher(akcipher);
+	kfree(tfm);
+}
+
+static int akcipher_setprivkey(void *private, const u8 *key,
+			       unsigned int keylen)
+{
+	struct akcipher_tfm *tfm = private;
+	struct crypto_akcipher *akcipher = tfm->akcipher;
+	int err;
+
+	err = crypto_akcipher_set_priv_key(akcipher, key, keylen);
+	tfm->has_key = !err;
+
+	/* Return the maximum size of the akcipher operation. */
+	if (!err)
+		err = crypto_akcipher_maxsize(akcipher);
+
+	return err;
+}
+
+static int akcipher_setpubkey(void *private, const u8 *key, unsigned int keylen)
+{
+	struct akcipher_tfm *tfm = private;
+	struct crypto_akcipher *akcipher = tfm->akcipher;
+	int err;
+
+	err = crypto_akcipher_set_pub_key(akcipher, key, keylen);
+	tfm->has_key = !err;
+
+	/* Return the maximum size of the akcipher operation. */
+	if (!err)
+		err = crypto_akcipher_maxsize(akcipher);
+
+	return err;
+}
+
+static void akcipher_sock_destruct(struct sock *sk)
+{
+	struct alg_sock *ask = alg_sk(sk);
+	struct af_alg_ctx *ctx = ask->private;
+
+	af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
+	sock_kfree_s(sk, ctx, ctx->len);
+	af_alg_release_parent(sk);
+}
+
+static int akcipher_accept_parent_nokey(void *private, struct sock *sk)
+{
+	struct af_alg_ctx *ctx;
+	struct alg_sock *ask = alg_sk(sk);
+	unsigned int len = sizeof(*ctx);
+
+	ctx = sock_kmalloc(sk, len, GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+	memset(ctx, 0, len);
+
+	INIT_LIST_HEAD(&ctx->tsgl_list);
+	ctx->len = len;
+	ctx->used = 0;
+	ctx->rcvused = 0;
+	ctx->more = 0;
+	ctx->merge = 0;
+	ctx->op = 0;
+	af_alg_init_completion(&ctx->completion);
+
+	ask->private = ctx;
+
+	sk->sk_destruct = akcipher_sock_destruct;
+
+	return 0;
+}
+
+static int akcipher_accept_parent(void *private, struct sock *sk)
+{
+	struct akcipher_tfm *tfm = private;
+
+	if (!tfm->has_key)
+		return -ENOKEY;
+
+	return akcipher_accept_parent_nokey(private, sk);
+}
+
+static const struct af_alg_type algif_type_akcipher = {
+	.bind		=	akcipher_bind,
+	.release	=	akcipher_release,
+	.setkey		=	akcipher_setprivkey,
+	.setpubkey	=	akcipher_setpubkey,
+	.setauthsize	=	NULL,
+	.accept		=	akcipher_accept_parent,
+	.accept_nokey	=	akcipher_accept_parent_nokey,
+	.ops		=	&algif_akcipher_ops,
+	.ops_nokey	=	&algif_akcipher_ops_nokey,
+	.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);
+	BUG_ON(err);
+}
+
+module_init(algif_akcipher_init);
+module_exit(algif_akcipher_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
+MODULE_DESCRIPTION("Asymmetric kernel crypto API user space interface");
diff --git a/include/crypto/if_alg.h b/include/crypto/if_alg.h
index d1de8ed3e77b..a2b396756e24 100644
--- a/include/crypto/if_alg.h
+++ b/include/crypto/if_alg.h
@@ -22,6 +22,7 @@
 
 #include <crypto/aead.h>
 #include <crypto/skcipher.h>
+#include <crypto/akcipher.h>
 
 #define ALG_MAX_PAGES			16
 
@@ -119,6 +120,7 @@ struct af_alg_async_req {
 	union {
 		struct aead_request aead_req;
 		struct skcipher_request skcipher_req;
+		struct akcipher_request akcipher_req;
 	} cra_u;
 
 	/* req ctx trails this struct */
-- 
2.13.4