linux/crypto/akcipher.c
Eric Biggers 29ce50e078 crypto: remove CONFIG_CRYPTO_STATS
Remove support for the "Crypto usage statistics" feature
(CONFIG_CRYPTO_STATS).  This feature does not appear to have ever been
used, and it is harmful because it significantly reduces performance and
is a large maintenance burden.

Covering each of these points in detail:

1. Feature is not being used

Since these generic crypto statistics are only readable using netlink,
it's fairly straightforward to look for programs that use them.  I'm
unable to find any evidence that any such programs exist.  For example,
Debian Code Search returns no hits except the kernel header and kernel
code itself and translations of the kernel header:
https://codesearch.debian.net/search?q=CRYPTOCFGA_STAT&literal=1&perpkg=1

The patch series that added this feature in 2018
(https://lore.kernel.org/linux-crypto/1537351855-16618-1-git-send-email-clabbe@baylibre.com/)
said "The goal is to have an ifconfig for crypto device."  This doesn't
appear to have happened.

It's not clear that there is real demand for crypto statistics.  Just
because the kernel provides other types of statistics such as I/O and
networking statistics and some people find those useful does not mean
that crypto statistics are useful too.

Further evidence that programs are not using CONFIG_CRYPTO_STATS is that
it was able to be disabled in RHEL and Fedora as a bug fix
(https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/2947).

Even further evidence comes from the fact that there are and have been
bugs in how the stats work, but they were never reported.  For example,
before Linux v6.7 hash stats were double-counted in most cases.

There has also never been any documentation for this feature, so it
might be hard to use even if someone wanted to.

2. CONFIG_CRYPTO_STATS significantly reduces performance

Enabling CONFIG_CRYPTO_STATS significantly reduces the performance of
the crypto API, even if no program ever retrieves the statistics.  This
primarily affects systems with a large number of CPUs.  For example,
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2039576 reported
that Lustre client encryption performance improved from 21.7GB/s to
48.2GB/s by disabling CONFIG_CRYPTO_STATS.

It can be argued that this means that CONFIG_CRYPTO_STATS should be
optimized with per-cpu counters similar to many of the networking
counters.  But no one has done this in 5+ years.  This is consistent
with the fact that the feature appears to be unused, so there seems to
be little interest in improving it as opposed to just disabling it.

It can be argued that because CONFIG_CRYPTO_STATS is off by default,
performance doesn't matter.  But Linux distros tend to error on the side
of enabling options.  The option is enabled in Ubuntu and Arch Linux,
and until recently was enabled in RHEL and Fedora (see above).  So, even
just having the option available is harmful to users.

3. CONFIG_CRYPTO_STATS is a large maintenance burden

There are over 1000 lines of code associated with CONFIG_CRYPTO_STATS,
spread among 32 files.  It significantly complicates much of the
implementation of the crypto API.  After the initial submission, many
fixes and refactorings have consumed effort of multiple people to keep
this feature "working".  We should be spending this effort elsewhere.

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2024-04-02 10:49:38 +08:00

282 lines
6.9 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Public Key Encryption
*
* Copyright (c) 2015, Intel Corporation
* Authors: Tadeusz Struk <tadeusz.struk@intel.com>
*/
#include <crypto/internal/akcipher.h>
#include <linux/cryptouser.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <net/netlink.h>
#include "internal.h"
#define CRYPTO_ALG_TYPE_AHASH_MASK 0x0000000e
static int __maybe_unused crypto_akcipher_report(
struct sk_buff *skb, struct crypto_alg *alg)
{
struct crypto_report_akcipher rakcipher;
memset(&rakcipher, 0, sizeof(rakcipher));
strscpy(rakcipher.type, "akcipher", sizeof(rakcipher.type));
return nla_put(skb, CRYPTOCFGA_REPORT_AKCIPHER,
sizeof(rakcipher), &rakcipher);
}
static void crypto_akcipher_show(struct seq_file *m, struct crypto_alg *alg)
__maybe_unused;
static void crypto_akcipher_show(struct seq_file *m, struct crypto_alg *alg)
{
seq_puts(m, "type : akcipher\n");
}
static void crypto_akcipher_exit_tfm(struct crypto_tfm *tfm)
{
struct crypto_akcipher *akcipher = __crypto_akcipher_tfm(tfm);
struct akcipher_alg *alg = crypto_akcipher_alg(akcipher);
alg->exit(akcipher);
}
static int crypto_akcipher_init_tfm(struct crypto_tfm *tfm)
{
struct crypto_akcipher *akcipher = __crypto_akcipher_tfm(tfm);
struct akcipher_alg *alg = crypto_akcipher_alg(akcipher);
if (alg->exit)
akcipher->base.exit = crypto_akcipher_exit_tfm;
if (alg->init)
return alg->init(akcipher);
return 0;
}
static void crypto_akcipher_free_instance(struct crypto_instance *inst)
{
struct akcipher_instance *akcipher = akcipher_instance(inst);
akcipher->free(akcipher);
}
static const struct crypto_type crypto_akcipher_type = {
.extsize = crypto_alg_extsize,
.init_tfm = crypto_akcipher_init_tfm,
.free = crypto_akcipher_free_instance,
#ifdef CONFIG_PROC_FS
.show = crypto_akcipher_show,
#endif
#if IS_ENABLED(CONFIG_CRYPTO_USER)
.report = crypto_akcipher_report,
#endif
.maskclear = ~CRYPTO_ALG_TYPE_MASK,
.maskset = CRYPTO_ALG_TYPE_AHASH_MASK,
.type = CRYPTO_ALG_TYPE_AKCIPHER,
.tfmsize = offsetof(struct crypto_akcipher, base),
};
int crypto_grab_akcipher(struct crypto_akcipher_spawn *spawn,
struct crypto_instance *inst,
const char *name, u32 type, u32 mask)
{
spawn->base.frontend = &crypto_akcipher_type;
return crypto_grab_spawn(&spawn->base, inst, name, type, mask);
}
EXPORT_SYMBOL_GPL(crypto_grab_akcipher);
struct crypto_akcipher *crypto_alloc_akcipher(const char *alg_name, u32 type,
u32 mask)
{
return crypto_alloc_tfm(alg_name, &crypto_akcipher_type, type, mask);
}
EXPORT_SYMBOL_GPL(crypto_alloc_akcipher);
static void akcipher_prepare_alg(struct akcipher_alg *alg)
{
struct crypto_alg *base = &alg->base;
base->cra_type = &crypto_akcipher_type;
base->cra_flags &= ~CRYPTO_ALG_TYPE_MASK;
base->cra_flags |= CRYPTO_ALG_TYPE_AKCIPHER;
}
static int akcipher_default_op(struct akcipher_request *req)
{
return -ENOSYS;
}
static int akcipher_default_set_key(struct crypto_akcipher *tfm,
const void *key, unsigned int keylen)
{
return -ENOSYS;
}
int crypto_register_akcipher(struct akcipher_alg *alg)
{
struct crypto_alg *base = &alg->base;
if (!alg->sign)
alg->sign = akcipher_default_op;
if (!alg->verify)
alg->verify = akcipher_default_op;
if (!alg->encrypt)
alg->encrypt = akcipher_default_op;
if (!alg->decrypt)
alg->decrypt = akcipher_default_op;
if (!alg->set_priv_key)
alg->set_priv_key = akcipher_default_set_key;
akcipher_prepare_alg(alg);
return crypto_register_alg(base);
}
EXPORT_SYMBOL_GPL(crypto_register_akcipher);
void crypto_unregister_akcipher(struct akcipher_alg *alg)
{
crypto_unregister_alg(&alg->base);
}
EXPORT_SYMBOL_GPL(crypto_unregister_akcipher);
int akcipher_register_instance(struct crypto_template *tmpl,
struct akcipher_instance *inst)
{
if (WARN_ON(!inst->free))
return -EINVAL;
akcipher_prepare_alg(&inst->alg);
return crypto_register_instance(tmpl, akcipher_crypto_instance(inst));
}
EXPORT_SYMBOL_GPL(akcipher_register_instance);
int crypto_akcipher_sync_prep(struct crypto_akcipher_sync_data *data)
{
unsigned int reqsize = crypto_akcipher_reqsize(data->tfm);
struct akcipher_request *req;
struct scatterlist *sg;
unsigned int mlen;
unsigned int len;
u8 *buf;
if (data->dst)
mlen = max(data->slen, data->dlen);
else
mlen = data->slen + data->dlen;
len = sizeof(*req) + reqsize + mlen;
if (len < mlen)
return -EOVERFLOW;
req = kzalloc(len, GFP_KERNEL);
if (!req)
return -ENOMEM;
data->req = req;
akcipher_request_set_tfm(req, data->tfm);
buf = (u8 *)(req + 1) + reqsize;
data->buf = buf;
memcpy(buf, data->src, data->slen);
sg = &data->sg;
sg_init_one(sg, buf, mlen);
akcipher_request_set_crypt(req, sg, data->dst ? sg : NULL,
data->slen, data->dlen);
crypto_init_wait(&data->cwait);
akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP,
crypto_req_done, &data->cwait);
return 0;
}
EXPORT_SYMBOL_GPL(crypto_akcipher_sync_prep);
int crypto_akcipher_sync_post(struct crypto_akcipher_sync_data *data, int err)
{
err = crypto_wait_req(err, &data->cwait);
if (data->dst)
memcpy(data->dst, data->buf, data->dlen);
data->dlen = data->req->dst_len;
kfree_sensitive(data->req);
return err;
}
EXPORT_SYMBOL_GPL(crypto_akcipher_sync_post);
int crypto_akcipher_sync_encrypt(struct crypto_akcipher *tfm,
const void *src, unsigned int slen,
void *dst, unsigned int dlen)
{
struct crypto_akcipher_sync_data data = {
.tfm = tfm,
.src = src,
.dst = dst,
.slen = slen,
.dlen = dlen,
};
return crypto_akcipher_sync_prep(&data) ?:
crypto_akcipher_sync_post(&data,
crypto_akcipher_encrypt(data.req));
}
EXPORT_SYMBOL_GPL(crypto_akcipher_sync_encrypt);
int crypto_akcipher_sync_decrypt(struct crypto_akcipher *tfm,
const void *src, unsigned int slen,
void *dst, unsigned int dlen)
{
struct crypto_akcipher_sync_data data = {
.tfm = tfm,
.src = src,
.dst = dst,
.slen = slen,
.dlen = dlen,
};
return crypto_akcipher_sync_prep(&data) ?:
crypto_akcipher_sync_post(&data,
crypto_akcipher_decrypt(data.req)) ?:
data.dlen;
}
EXPORT_SYMBOL_GPL(crypto_akcipher_sync_decrypt);
static void crypto_exit_akcipher_ops_sig(struct crypto_tfm *tfm)
{
struct crypto_akcipher **ctx = crypto_tfm_ctx(tfm);
crypto_free_akcipher(*ctx);
}
int crypto_init_akcipher_ops_sig(struct crypto_tfm *tfm)
{
struct crypto_akcipher **ctx = crypto_tfm_ctx(tfm);
struct crypto_alg *calg = tfm->__crt_alg;
struct crypto_akcipher *akcipher;
if (!crypto_mod_get(calg))
return -EAGAIN;
akcipher = crypto_create_tfm(calg, &crypto_akcipher_type);
if (IS_ERR(akcipher)) {
crypto_mod_put(calg);
return PTR_ERR(akcipher);
}
*ctx = akcipher;
tfm->exit = crypto_exit_akcipher_ops_sig;
return 0;
}
EXPORT_SYMBOL_GPL(crypto_init_akcipher_ops_sig);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Generic public key cipher type");