linux/crypto/algif_aead.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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.
 *
 * 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 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 <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>

static const struct af_alg_allowlist_entry aead_allowlist[] = {
	{ "ccm(aes)", true }, /* bluez */
	{},
};

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 crypto_aead *tfm = pask->private;
	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 crypto_aead *tfm = pask->private;
	unsigned int ivsize = crypto_aead_ivsize(tfm);

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

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 crypto_aead *tfm = pask->private;
	unsigned int as = crypto_aead_authsize(tfm);
	unsigned int ivsize = crypto_aead_ivsize(tfm);
	struct af_alg_async_req *areq;
	struct scatterlist *rsgl_src, *tsgl_src = NULL;
	void *iv;
	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->init || ctx->more) {
		err = af_alg_wait_for_data(sk, flags, 0);
		if (err)
			return err;
	}

	/*
	 * Data length provided by caller via sendmsg that has not yet been
	 * processed.
	 */
	used = ctx->used;

	/*
	 * Make sure sufficient data is present -- note, the same check is also
	 * present in sendmsg. The checks in 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 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) + ivsize);
	if (IS_ERR(areq))
		return PTR_ERR(areq);

	iv = (u8 *)aead_request_ctx(&areq->cra_u.aead_req) +
	     crypto_aead_reqsize(tfm);
	memcpy(iv, ctx->iv, ivsize);

	/* 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 + (ctx->enc ? 0 : as)) {
			err = -EINVAL;
			goto free;
		}
		used -= less;
		outlen -= less;
	}

	/*
	 * Create a per request TX SGL for this request which tracks the
	 * SG entries from the global TX SGL.
	 */
	processed = used + ctx->aead_assoclen;
	areq->tsgl_entries = af_alg_count_tsgl(sk, processed);
	if (!areq->tsgl_entries)
		areq->tsgl_entries = 1;
	areq->tsgl = sock_kmalloc(sk, array_size(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, processed, areq->tsgl);
	tsgl_src = areq->tsgl;

	/*
	 * 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.
	 */

	/* Use the RX SGL as source (and destination) for crypto op. */
	rsgl_src = areq->first_rsgl.sgl.sgt.sgl;

	memcpy_sglist(rsgl_src, tsgl_src, ctx->aead_assoclen);

	/* Initialize the crypto operation */
	aead_request_set_crypt(&areq->cra_u.aead_req, tsgl_src,
			       areq->first_rsgl.sgl.sgt.sgl, used, iv);
	aead_request_set_ad(&areq->cra_u.aead_req, ctx->aead_assoclen);
	aead_request_set_tfm(&areq->cra_u.aead_req, tfm);

	aead_request_set_callback(&areq->cra_u.aead_req,
				  CRYPTO_TFM_REQ_MAY_SLEEP |
				  CRYPTO_TFM_REQ_MAY_BACKLOG,
				  crypto_req_done, &ctx->wait);
	err = crypto_wait_req(ctx->enc ?
			crypto_aead_encrypt(&areq->cra_u.aead_req) :
			crypto_aead_decrypt(&areq->cra_u.aead_req),
			&ctx->wait);

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,
	.mmap		=	sock_no_mmap,
	.bind		=	sock_no_bind,
	.accept		=	sock_no_accept,

	.release	=	af_alg_release,
	.sendmsg	=	aead_sendmsg,
	.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 crypto_aead *tfm;
	struct sock *sk = sock->sk;
	struct alg_sock *ask = alg_sk(sk);

	lock_sock(sk);
	if (!atomic_read(&ask->nokey_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 (crypto_aead_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
		goto unlock;

	atomic_dec(&pask->nokey_refcnt);
	atomic_set(&ask->nokey_refcnt, 0);

	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 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,
	.mmap		=	sock_no_mmap,
	.bind		=	sock_no_bind,
	.accept		=	sock_no_accept,

	.release	=	af_alg_release,
	.sendmsg	=	aead_sendmsg_nokey,
	.recvmsg	=	aead_recvmsg_nokey,
	.poll		=	af_alg_poll,
};

static void *aead_bind(const char *name)
{
	int err;

	err = af_alg_check_restriction(name, aead_allowlist);
	if (err)
		return ERR_PTR(err);

	return crypto_alloc_aead(name, 0, AF_ALG_CRYPTOAPI_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 af_alg_ctx *ctx = ask->private;
	struct sock *psk = ask->parent;
	struct alg_sock *pask = alg_sk(psk);
	struct crypto_aead *tfm = pask->private;
	unsigned int ivlen = crypto_aead_ivsize(tfm);

	af_alg_pull_tsgl(sk, ctx->used, NULL);
	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 crypto_aead *tfm = private;
	unsigned int len = sizeof(*ctx);
	unsigned int ivlen = crypto_aead_ivsize(tfm);

	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;
	crypto_init_wait(&ctx->wait);

	ask->private = ctx;

	sk->sk_destruct = aead_sock_destruct;

	return 0;
}

static int aead_accept_parent(void *private, struct sock *sk)
{
	struct crypto_aead *tfm = private;

	if (crypto_aead_get_flags(tfm) & CRYPTO_TFM_NEED_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");