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linux/arch/arm64/crypto/sm4-ce-ccm-glue.c
Tianjia Zhang 3b9d902153 crypto: arm64/sm4-ccm - Rewrite skcipher walker loop 
The fact that an error in the skcipher walker API are indicated
not only by a non-zero return value, but also by the fact that
walk->nbytes is zero, causes the layout of the skcipher walker
loop to be sufficiently different from the usual layout, which
is not a problem in itself, but it is likely to cause reading
confusion and difficulty in code maintenance.

This patch rewrites skcipher walker loop, and separates the
last chunk cryption from the loop to avoid wrong calls to the
skcipher walker API. In addition to following the usual convention
of checking walk->nbytes, it also makes the loop execute logic
clearer and easier to understand.

Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-02-10 17:20:19 +08:00

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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* SM4-CCM AEAD Algorithm using ARMv8 Crypto Extensions
* as specified in rfc8998
* https://datatracker.ietf.org/doc/html/rfc8998
*
* Copyright (C) 2022 Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
*/
#include <linux/module.h>
#include <linux/crypto.h>
#include <linux/kernel.h>
#include <linux/cpufeature.h>
#include <asm/neon.h>
#include <crypto/scatterwalk.h>
#include <crypto/internal/aead.h>
#include <crypto/internal/skcipher.h>
#include <crypto/sm4.h>
#include "sm4-ce.h"
asmlinkage void sm4_ce_cbcmac_update(const u32 *rkey_enc, u8 *mac,
const u8 *src, unsigned int nblocks);
asmlinkage void sm4_ce_ccm_enc(const u32 *rkey_enc, u8 *dst, const u8 *src,
u8 *iv, unsigned int nbytes, u8 *mac);
asmlinkage void sm4_ce_ccm_dec(const u32 *rkey_enc, u8 *dst, const u8 *src,
u8 *iv, unsigned int nbytes, u8 *mac);
asmlinkage void sm4_ce_ccm_final(const u32 *rkey_enc, u8 *iv, u8 *mac);
static int ccm_setkey(struct crypto_aead *tfm, const u8 *key,
unsigned int key_len)
{
struct sm4_ctx *ctx = crypto_aead_ctx(tfm);
if (key_len != SM4_KEY_SIZE)
return -EINVAL;
kernel_neon_begin();
sm4_ce_expand_key(key, ctx->rkey_enc, ctx->rkey_dec,
crypto_sm4_fk, crypto_sm4_ck);
kernel_neon_end();
return 0;
}
static int ccm_setauthsize(struct crypto_aead *tfm, unsigned int authsize)
{
if ((authsize & 1) || authsize < 4)
return -EINVAL;
return 0;
}
static int ccm_format_input(u8 info[], struct aead_request *req,
unsigned int msglen)
{
struct crypto_aead *aead = crypto_aead_reqtfm(req);
unsigned int l = req->iv[0] + 1;
unsigned int m;
__be32 len;
/* verify that CCM dimension 'L': 2 <= L <= 8 */
if (l < 2 || l > 8)
return -EINVAL;
if (l < 4 && msglen >> (8 * l))
return -EOVERFLOW;
memset(&req->iv[SM4_BLOCK_SIZE - l], 0, l);
memcpy(info, req->iv, SM4_BLOCK_SIZE);
m = crypto_aead_authsize(aead);
/* format flags field per RFC 3610/NIST 800-38C */
*info |= ((m - 2) / 2) << 3;
if (req->assoclen)
*info |= (1 << 6);
/*
* format message length field,
* Linux uses a u32 type to represent msglen
*/
if (l >= 4)
l = 4;
len = cpu_to_be32(msglen);
memcpy(&info[SM4_BLOCK_SIZE - l], (u8 *)&len + 4 - l, l);
return 0;
}
static void ccm_calculate_auth_mac(struct aead_request *req, u8 mac[])
{
struct crypto_aead *aead = crypto_aead_reqtfm(req);
struct sm4_ctx *ctx = crypto_aead_ctx(aead);
struct __packed { __be16 l; __be32 h; } aadlen;
u32 assoclen = req->assoclen;
struct scatter_walk walk;
unsigned int len;
if (assoclen < 0xff00) {
aadlen.l = cpu_to_be16(assoclen);
len = 2;
} else {
aadlen.l = cpu_to_be16(0xfffe);
put_unaligned_be32(assoclen, &aadlen.h);
len = 6;
}
sm4_ce_crypt_block(ctx->rkey_enc, mac, mac);
crypto_xor(mac, (const u8 *)&aadlen, len);
scatterwalk_start(&walk, req->src);
do {
u32 n = scatterwalk_clamp(&walk, assoclen);
u8 *p, *ptr;
if (!n) {
scatterwalk_start(&walk, sg_next(walk.sg));
n = scatterwalk_clamp(&walk, assoclen);
}
p = ptr = scatterwalk_map(&walk);
assoclen -= n;
scatterwalk_advance(&walk, n);
while (n > 0) {
unsigned int l, nblocks;
if (len == SM4_BLOCK_SIZE) {
if (n < SM4_BLOCK_SIZE) {
sm4_ce_crypt_block(ctx->rkey_enc,
mac, mac);
len = 0;
} else {
nblocks = n / SM4_BLOCK_SIZE;
sm4_ce_cbcmac_update(ctx->rkey_enc,
mac, ptr, nblocks);
ptr += nblocks * SM4_BLOCK_SIZE;
n %= SM4_BLOCK_SIZE;
continue;
}
}
l = min(n, SM4_BLOCK_SIZE - len);
if (l) {
crypto_xor(mac + len, ptr, l);
len += l;
ptr += l;
n -= l;
}
}
scatterwalk_unmap(p);
scatterwalk_done(&walk, 0, assoclen);
} while (assoclen);
}
static int ccm_crypt(struct aead_request *req, struct skcipher_walk *walk,
u32 *rkey_enc, u8 mac[],
void (*sm4_ce_ccm_crypt)(const u32 *rkey_enc, u8 *dst,
const u8 *src, u8 *iv,
unsigned int nbytes, u8 *mac))
{
u8 __aligned(8) ctr0[SM4_BLOCK_SIZE];
int err = 0;
/* preserve the initial ctr0 for the TAG */
memcpy(ctr0, walk->iv, SM4_BLOCK_SIZE);
crypto_inc(walk->iv, SM4_BLOCK_SIZE);
kernel_neon_begin();
if (req->assoclen)
ccm_calculate_auth_mac(req, mac);
while (walk->nbytes && walk->nbytes != walk->total) {
unsigned int tail = walk->nbytes % SM4_BLOCK_SIZE;
sm4_ce_ccm_crypt(rkey_enc, walk->dst.virt.addr,
walk->src.virt.addr, walk->iv,
walk->nbytes - tail, mac);
kernel_neon_end();
err = skcipher_walk_done(walk, tail);
kernel_neon_begin();
}
if (walk->nbytes) {
sm4_ce_ccm_crypt(rkey_enc, walk->dst.virt.addr,
walk->src.virt.addr, walk->iv,
walk->nbytes, mac);
sm4_ce_ccm_final(rkey_enc, ctr0, mac);
kernel_neon_end();
err = skcipher_walk_done(walk, 0);
} else {
sm4_ce_ccm_final(rkey_enc, ctr0, mac);
kernel_neon_end();
}
return err;
}
static int ccm_encrypt(struct aead_request *req)
{
struct crypto_aead *aead = crypto_aead_reqtfm(req);
struct sm4_ctx *ctx = crypto_aead_ctx(aead);
u8 __aligned(8) mac[SM4_BLOCK_SIZE];
struct skcipher_walk walk;
int err;
err = ccm_format_input(mac, req, req->cryptlen);
if (err)
return err;
err = skcipher_walk_aead_encrypt(&walk, req, false);
if (err)
return err;
err = ccm_crypt(req, &walk, ctx->rkey_enc, mac, sm4_ce_ccm_enc);
if (err)
return err;
/* copy authtag to end of dst */
scatterwalk_map_and_copy(mac, req->dst, req->assoclen + req->cryptlen,
crypto_aead_authsize(aead), 1);
return 0;
}
static int ccm_decrypt(struct aead_request *req)
{
struct crypto_aead *aead = crypto_aead_reqtfm(req);
unsigned int authsize = crypto_aead_authsize(aead);
struct sm4_ctx *ctx = crypto_aead_ctx(aead);
u8 __aligned(8) mac[SM4_BLOCK_SIZE];
u8 authtag[SM4_BLOCK_SIZE];
struct skcipher_walk walk;
int err;
err = ccm_format_input(mac, req, req->cryptlen - authsize);
if (err)
return err;
err = skcipher_walk_aead_decrypt(&walk, req, false);
if (err)
return err;
err = ccm_crypt(req, &walk, ctx->rkey_enc, mac, sm4_ce_ccm_dec);
if (err)
return err;
/* compare calculated auth tag with the stored one */
scatterwalk_map_and_copy(authtag, req->src,
req->assoclen + req->cryptlen - authsize,
authsize, 0);
if (crypto_memneq(authtag, mac, authsize))
return -EBADMSG;
return 0;
}
static struct aead_alg sm4_ccm_alg = {
.base = {
.cra_name = "ccm(sm4)",
.cra_driver_name = "ccm-sm4-ce",
.cra_priority = 400,
.cra_blocksize = 1,
.cra_ctxsize = sizeof(struct sm4_ctx),
.cra_module = THIS_MODULE,
},
.ivsize = SM4_BLOCK_SIZE,
.chunksize = SM4_BLOCK_SIZE,
.maxauthsize = SM4_BLOCK_SIZE,
.setkey = ccm_setkey,
.setauthsize = ccm_setauthsize,
.encrypt = ccm_encrypt,
.decrypt = ccm_decrypt,
};
static int __init sm4_ce_ccm_init(void)
{
return crypto_register_aead(&sm4_ccm_alg);
}
static void __exit sm4_ce_ccm_exit(void)
{
crypto_unregister_aead(&sm4_ccm_alg);
}
module_cpu_feature_match(SM4, sm4_ce_ccm_init);
module_exit(sm4_ce_ccm_exit);
MODULE_DESCRIPTION("Synchronous SM4 in CCM mode using ARMv8 Crypto Extensions");
MODULE_ALIAS_CRYPTO("ccm(sm4)");
MODULE_AUTHOR("Tianjia Zhang <tianjia.zhang@linux.alibaba.com>");
MODULE_LICENSE("GPL v2");
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