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|
// 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 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/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_BACKLOG,
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->used) {
err = af_alg_wait_for_data(sk, flags);
if (err)
return err;
}
/*
* Data length provided by caller via sendmsg/sendpage that has not
* yet been processed.
*/
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(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.sg;
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.sg, processed);
if (err)
goto free;
af_alg_pull_tsgl(sk, processed, NULL, 0);
} else {
/*
* Decryption operation - To achieve an in-place cipher
* operation, t
|