// SPDX-License-Identifier: GPL-2.0-or-later
/*
* algif_aead: User-space interface for AEAD algorithms
*
* Copyright (C) 2014, Stephan Mueller <[email protected]>
*
* 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 (maybe with
* MSG_SPLICE_PAGES). 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 <crypto/skcipher.h>
#include <crypto/null.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_tfm {
struct crypto_aead *aead;
struct crypto_sync_skcipher *null_tfm;
};
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 aead_tfm *aeadc = pask->private;
struct crypto_aead *tfm = aeadc->aead;
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 aead_tfm *aeadc = pask->private;
struct crypto_aead *tfm = aeadc->aead;
unsigned int ivsize = crypto_aead_ivsize(tfm);
return af_alg_sendmsg(sock, msg, size, ivsize);
}
static int crypto_aead_copy_sgl(struct crypto_sync_skcipher *null_tfm,
struct scatterlist *src,
struct scatterlist *dst, unsigned int len)
{
SYNC_SKCIPHER_REQUEST_ON_STACK(skreq, null_tfm);
skcipher_request_set_sync_tfm(skreq, null_tfm);
skcipher_request_set_callback(skreq, CRYPTO_TFM_REQ_MAY_SLEEP,
NULL, NULL);
skcipher_request_set_crypt(skreq, src, dst, len, NULL);
return crypto_skcipher_encrypt(skreq);
}
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 aead_tfm *aeadc = pask->private;
struct crypto_aead *tfm = aeadc->aead;
struct crypto_sync_skcipher *null_tfm = aeadc->null_tfm;
unsigned int i, as = crypto_aead_authsize(tfm);
struct af_alg_async_req *areq;
struct af_alg_tsgl *tsgl, *tmp;
struct scatterlist *rsgl_src, *tsgl_src = NULL;
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));
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, 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) {
err = -EINVAL;
goto free;
}
used -= less;
outlen -= less;
}
processed = used + ctx->aead_assoclen;
list_for_each_entry_safe(tsgl, tmp, &ctx->tsgl_list, list) {
for (i = 0; i < tsgl->cur; i++) {
struct scatterlist *process_sg = tsgl->sg + i;
if (!(process_sg->length) || !sg_page(process_sg))
continue;
tsgl_src = process_sg;
break;
}
if (tsgl_src)
break;
}
if (processed && !tsgl_src) {
err = -EFAULT;
goto free;
}
/*
* 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.
*
* To ensure efficiency, the following implementation ensure that the
* ciphers are invoked to perform a crypto operation in-place. This
* is achieved by memory management specified as follows.
*/
/* Use the RX SGL as source (and destination) for crypto op. */
rsgl_src = areq->first_rsgl.sgl.sgt.sgl;
if (ctx->enc) {
/*
* Encryption operation - The in-place cipher operation is
* achieved by the following operation:
*
* TX SGL: AAD || PT
* | |
* | copy |
* v v
* RX SGL: AAD || PT || Tag
*/
err = crypto_aead_copy_sgl(null_tfm, tsgl_src,
areq->first_rsgl.sgl.sgt.sgl,
processed);
if (err)
goto free;
af_alg_pull_tsgl(sk, processed, NULL, 0);
} else {
/*
* Decryption operation - To achieve an in-place cipher
* operation, the following SGL structure is used:
*
* TX SGL: AAD || CT || Tag
* | | ^
* | copy | | Create SGL link.
* v v |
* RX SGL: AAD || CT ----+
*/
/* Copy AAD || CT to RX SGL buffer for in-place operation. */
err = crypto_aead_copy_sgl(null_tfm, tsgl_src,
areq->first_rsgl.sgl.sgt.sgl,
outlen);
if (err)
goto free;
/* Create TX SGL for tag and chain it to RX SGL. */
areq->tsgl_entries = af_alg_count_tsgl(sk, processed,
processed - as);
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);
/* Release TX SGL, except for tag data and reassign tag data. */
af_alg_pull_tsgl(sk, processed, areq->tsgl, processed - as);
/* chain the areq TX SGL holding the tag with RX SGL */
if (usedpages) {
/* RX SGL present */
struct af_alg_sgl *sgl_prev = &areq->last_rsgl->sgl;
struct scatterlist *sg = sgl_prev->sgt.sgl;
sg_unmark_end(sg + sgl_prev->sgt.nents - 1);
sg_chain(sg, sgl_prev->sgt.nents + 1, areq->tsgl);
} else
/* no RX SGL present (e.g. authentication only) */
rsgl_src = areq->tsgl;
}
/* Initialize the crypto operation */
aead_request_set_crypt(&areq->cra_u.aead_req, rsgl_src,
areq->first_rsgl.sgl.sgt.sgl, used, ctx->iv);
aead_request_set_ad(&areq->cra_u.aead_req, ctx->aead_assoclen);
aead_request_set_tfm(&areq->cra_u.aead_req, tfm);
if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) {
/* AIO operation */
sock_hold(sk);
areq->iocb = msg->msg_iocb;
/* Remember output size that will be generated. */
areq->outlen = outlen;
aead_request_set_callback(&areq->cra_u.aead_req,
CRYPTO_TFM_REQ_MAY_SLEEP,
af_alg_async_cb, areq);
err = ctx->enc ? crypto_aead_encrypt(&areq->cra_u.aead_req) :
crypto_aead_decrypt(&areq->cra_u.aead_req);
/* AIO operation in progress */
if (err == -EINPROGRESS)
return -EIOCBQUEUED;
sock_put(sk);
} else {
/* Synchronous operation */
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 aead_tfm *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->aead) & 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, u32 type, u32 mask)
{
struct aead_tfm *tfm;
struct crypto_aead *aead;
struct crypto_sync_skcipher *null_tfm;
tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
if (!tfm)
return ERR_PTR(-ENOMEM);
aead = crypto_alloc_aead(name, type, mask);
if (IS_ERR(aead)) {
kfree(tfm);
return ERR_CAST(aead);
}
null_tfm = crypto_get_default_null_skcipher();
if (IS_ERR(null_tfm)) {
crypto_free_aead(aead);
kfree(tfm);
return ERR_CAST(null_tfm);
}
tfm->aead = aead;
tfm->null_tfm = null_tfm;
return tfm;
}
static void aead_release(void *private)
{
struct aead_tfm *tfm = private;
crypto_free_aead(tfm->aead);
crypto_put_default_null_skcipher();
kfree(tfm);
}
static int aead_setauthsize(void *private, unsigned int authsize)
{
struct aead_tfm *tfm = private;
return crypto_aead_setauthsize(tfm->aead, authsize);
}
static int aead_setkey(void *private, const u8 *key, unsigned int keylen)
{
struct aead_tfm *tfm = private;
return crypto_aead_setkey(tfm->aead, 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 aead_tfm *aeadc = pask->private;
struct crypto_aead *tfm = aeadc->aead;
unsigned int ivlen = crypto_aead_ivsize(tfm);
af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
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 aead_tfm *tfm = private;
struct crypto_aead *aead = tfm->aead;
unsigned int len = sizeof(*ctx);
unsigned int ivlen = crypto_aead_ivsize(aead);
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 aead_tfm *tfm = private;
if (crypto_aead_get_flags(tfm->aead) & 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 <[email protected]>");
MODULE_DESCRIPTION("AEAD kernel crypto API user space interface");
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