linux/crypto/ctr.c

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/*
* CTR: Counter mode
*
* (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
*/
#include <crypto/algapi.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>
struct ctr_instance_ctx {
struct crypto_spawn alg;
unsigned int noncesize;
unsigned int ivsize;
unsigned int countersize;
};
struct crypto_ctr_ctx {
struct crypto_cipher *child;
u8 *nonce;
};
static inline void __ctr_inc_byte(u8 *a, unsigned int size)
{
u8 *b = (a + size);
u8 c;
for (; size; size--) {
c = *--b + 1;
*b = c;
if (c)
break;
}
}
static void ctr_inc_quad(u8 *a, unsigned int size)
{
__be32 *b = (__be32 *)(a + size);
u32 c;
for (; size >= 4; size -=4) {
c = be32_to_cpu(*--b) + 1;
*b = cpu_to_be32(c);
if (c)
return;
}
__ctr_inc_byte(a, size);
}
static void xor_byte(u8 *a, const u8 *b, unsigned int bs)
{
for (; bs; bs--)
*a++ ^= *b++;
}
static void xor_quad(u8 *dst, const u8 *src, unsigned int bs)
{
u32 *a = (u32 *)dst;
u32 *b = (u32 *)src;
for (; bs >= 4; bs -= 4)
*a++ ^= *b++;
xor_byte((u8 *)a, (u8 *)b, bs);
}
static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key,
unsigned int keylen)
{
struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(parent);
struct crypto_cipher *child = ctx->child;
struct ctr_instance_ctx *ictx =
crypto_instance_ctx(crypto_tfm_alg_instance(parent));
unsigned int noncelen = ictx->noncesize;
int err = 0;
/* the nonce is stored in bytes at end of key */
if (keylen < noncelen)
return -EINVAL;
memcpy(ctx->nonce, key + (keylen - noncelen), noncelen);
keylen -= noncelen;
crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
CRYPTO_TFM_REQ_MASK);
err = crypto_cipher_setkey(child, key, keylen);
crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
CRYPTO_TFM_RES_MASK);
return err;
}
static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk,
struct crypto_cipher *tfm, u8 *ctrblk,
unsigned int countersize)
{
void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
crypto_cipher_alg(tfm)->cia_encrypt;
unsigned int bsize = crypto_cipher_blocksize(tfm);
unsigned long alignmask = crypto_cipher_alignmask(tfm);
u8 ks[bsize + alignmask];
u8 *keystream = (u8 *)ALIGN((unsigned long)ks, alignmask + 1);
u8 *src = walk->src.virt.addr;
u8 *dst = walk->dst.virt.addr;
unsigned int nbytes = walk->nbytes;
do {
/* create keystream */
fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
xor_quad(keystream, src, min(nbytes, bsize));
/* copy result into dst */
memcpy(dst, keystream, min(nbytes, bsize));
/* increment counter in counterblock */
ctr_inc_quad(ctrblk + (bsize - countersize), countersize);
if (nbytes < bsize)
break;
src += bsize;
dst += bsize;
nbytes -= bsize;
} while (nbytes);
return 0;
}
static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
struct crypto_cipher *tfm, u8 *ctrblk,
unsigned int countersize)
{
void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
crypto_cipher_alg(tfm)->cia_encrypt;
unsigned int bsize = crypto_cipher_blocksize(tfm);
unsigned long alignmask = crypto_cipher_alignmask(tfm);
unsigned int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr;
u8 ks[bsize + alignmask];
u8 *keystream = (u8 *)ALIGN((unsigned long)ks, alignmask + 1);
do {
/* create keystream */
fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
xor_quad(src, keystream, min(nbytes, bsize));
/* increment counter in counterblock */
ctr_inc_quad(ctrblk + (bsize - countersize), countersize);
if (nbytes < bsize)
break;
src += bsize;
nbytes -= bsize;
} while (nbytes);
return 0;
}
static int crypto_ctr_crypt(struct blkcipher_desc *desc,
struct scatterlist *dst, struct scatterlist *src,
unsigned int nbytes)
{
struct blkcipher_walk walk;
struct crypto_blkcipher *tfm = desc->tfm;
struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm);
struct crypto_cipher *child = ctx->child;
unsigned int bsize = crypto_cipher_blocksize(child);
struct ctr_instance_ctx *ictx =
crypto_instance_ctx(crypto_tfm_alg_instance(&tfm->base));
unsigned long alignmask = crypto_cipher_alignmask(child);
u8 cblk[bsize + alignmask];
u8 *counterblk = (u8 *)ALIGN((unsigned long)cblk, alignmask + 1);
int err;
blkcipher_walk_init(&walk, dst, src, nbytes);
err = blkcipher_walk_virt_block(desc, &walk, bsize);
/* set up counter block */
memset(counterblk, 0 , bsize);
memcpy(counterblk, ctx->nonce, ictx->noncesize);
memcpy(counterblk + ictx->noncesize, walk.iv, ictx->ivsize);
/* initialize counter portion of counter block */
ctr_inc_quad(counterblk + (bsize - ictx->countersize),
ictx->countersize);
while (walk.nbytes) {
if (walk.src.virt.addr == walk.dst.virt.addr)
nbytes = crypto_ctr_crypt_inplace(&walk, child,
counterblk,
ictx->countersize);
else
nbytes = crypto_ctr_crypt_segment(&walk, child,
counterblk,
ictx->countersize);
err = blkcipher_walk_done(desc, &walk, nbytes);
}
return err;
}
static int crypto_ctr_init_tfm(struct crypto_tfm *tfm)
{
struct crypto_instance *inst = (void *)tfm->__crt_alg;
struct ctr_instance_ctx *ictx = crypto_instance_ctx(inst);
struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
struct crypto_cipher *cipher;
ctx->nonce = kzalloc(ictx->noncesize, GFP_KERNEL);
if (!ctx->nonce)
return -ENOMEM;
cipher = crypto_spawn_cipher(&ictx->alg);
if (IS_ERR(cipher))
return PTR_ERR(cipher);
ctx->child = cipher;
return 0;
}
static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
{
struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
kfree(ctx->nonce);
crypto_free_cipher(ctx->child);
}
static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
{
struct crypto_instance *inst;
struct crypto_alg *alg;
struct ctr_instance_ctx *ictx;
unsigned int noncesize;
unsigned int ivsize;
unsigned int countersize;
int err;
err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
if (err)
return ERR_PTR(err);
alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
CRYPTO_ALG_TYPE_MASK);
if (IS_ERR(alg))
return ERR_PTR(PTR_ERR(alg));
err = crypto_attr_u32(tb[2], &noncesize);
if (err)
goto out_put_alg;
err = crypto_attr_u32(tb[3], &ivsize);
if (err)
goto out_put_alg;
err = crypto_attr_u32(tb[4], &countersize);
if (err)
goto out_put_alg;
/* verify size of nonce + iv + counter
* counter must be >= 4 bytes.
*/
err = -EINVAL;
if (((noncesize + ivsize + countersize) < alg->cra_blocksize) ||
((noncesize + ivsize) > alg->cra_blocksize) ||
(countersize > alg->cra_blocksize) || (countersize < 4))
goto out_put_alg;
inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
err = -ENOMEM;
if (!inst)
goto out_put_alg;
err = -ENAMETOOLONG;
if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
"ctr(%s,%u,%u,%u)", alg->cra_name, noncesize,
ivsize, countersize) >= CRYPTO_MAX_ALG_NAME) {
goto err_free_inst;
}
if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
"ctr(%s,%u,%u,%u)", alg->cra_driver_name, noncesize,
ivsize, countersize) >= CRYPTO_MAX_ALG_NAME) {
goto err_free_inst;
}
ictx = crypto_instance_ctx(inst);
ictx->noncesize = noncesize;
ictx->ivsize = ivsize;
ictx->countersize = countersize;
err = crypto_init_spawn(&ictx->alg, alg, inst,
CRYPTO_ALG_TYPE_MASK | CRYPTO_ALG_ASYNC);
if (err)
goto err_free_inst;
err = 0;
inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
inst->alg.cra_priority = alg->cra_priority;
inst->alg.cra_blocksize = 1;
inst->alg.cra_alignmask = 3;
inst->alg.cra_type = &crypto_blkcipher_type;
inst->alg.cra_blkcipher.ivsize = ivsize;
inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize
+ noncesize;
inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize
+ noncesize;
inst->alg.cra_ctxsize = sizeof(struct crypto_ctr_ctx);
inst->alg.cra_init = crypto_ctr_init_tfm;
inst->alg.cra_exit = crypto_ctr_exit_tfm;
inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;
err_free_inst:
if (err)
kfree(inst);
out_put_alg:
crypto_mod_put(alg);
if (err)
inst = ERR_PTR(err);
return inst;
}
static void crypto_ctr_free(struct crypto_instance *inst)
{
struct ctr_instance_ctx *ictx = crypto_instance_ctx(inst);
crypto_drop_spawn(&ictx->alg);
kfree(inst);
}
static struct crypto_template crypto_ctr_tmpl = {
.name = "ctr",
.alloc = crypto_ctr_alloc,
.free = crypto_ctr_free,
.module = THIS_MODULE,
};
static int __init crypto_ctr_module_init(void)
{
return crypto_register_template(&crypto_ctr_tmpl);
}
static void __exit crypto_ctr_module_exit(void)
{
crypto_unregister_template(&crypto_ctr_tmpl);
}
module_init(crypto_ctr_module_init);
module_exit(crypto_ctr_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("CTR Counter block mode");