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crypto: salsa20-generic - cleanup and convert to skcipher API

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Convert salsa20-generic from the deprecated "blkcipher" API to the
"skcipher" API, in the process fixing it up to be thread-safe (as the
crypto API expects) by maintaining each request's state separately from
the transform context.

Also remove the unnecessary cra_alignmask and tighten validation of the
key size by accepting only 16 or 32 bytes, not anything in between.

These changes bring the code close to the way chacha20-generic does
things, so hopefully it will be easier to maintain in the future.

However, the way Salsa20 interprets the IV is still slightly different;
that was not changed.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric Biggers 2018-01-05 11:09:57 -08:00 committed by Herbert Xu
parent 148b974dee
commit b62b3db76f
1 changed files with 108 additions and 140 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

236
crypto/salsa20_generic.c
View file

@ -19,49 +19,27 @@
* *
*/ */
#include <linux/init.h> #include <asm/unaligned.h>
#include <crypto/internal/skcipher.h>
#include <linux/module.h> #include <linux/module.h>
#include <linux/errno.h>
#include <linux/crypto.h>
#include <linux/types.h>
#include <linux/bitops.h>
#include <crypto/algapi.h>
#include <asm/byteorder.h>
#define SALSA20_IV_SIZE 8U #define SALSA20_IV_SIZE 8
#define SALSA20_MIN_KEY_SIZE 16U #define SALSA20_MIN_KEY_SIZE 16
#define SALSA20_MAX_KEY_SIZE 32U #define SALSA20_MAX_KEY_SIZE 32
#define SALSA20_BLOCK_SIZE 64
/* struct salsa20_ctx {
* Start of code taken from D. J. Bernstein's reference implementation. u32 initial_state[16];
* With some modifications and optimizations made to suit our needs.
*/
/*
salsa20-ref.c version 20051118
D. J. Bernstein
Public domain.
*/
#define U32TO8_LITTLE(p, v) \
{ (p)[0] = (v >> 0) & 0xff; (p)[1] = (v >> 8) & 0xff; \
(p)[2] = (v >> 16) & 0xff; (p)[3] = (v >> 24) & 0xff; }
#define U8TO32_LITTLE(p) \
(((u32)((p)[0]) ) | ((u32)((p)[1]) << 8) | \
((u32)((p)[2]) << 16) | ((u32)((p)[3]) << 24) )
struct salsa20_ctx
{
u32 input[16];
}; };
static void salsa20_wordtobyte(u8 output[64], const u32 input[16]) static void salsa20_block(u32 *state, __le32 *stream)
{ {
u32 x[16]; u32 x[16];
int i; int i;
memcpy(x, input, sizeof(x)); memcpy(x, state, sizeof(x));
for (i = 20; i > 0; i -= 2) {
for (i = 0; i < 20; i += 2) {
x[ 4] ^= rol32((x[ 0] + x[12]), 7); x[ 4] ^= rol32((x[ 0] + x[12]), 7);
x[ 8] ^= rol32((x[ 4] + x[ 0]), 9); x[ 8] ^= rol32((x[ 4] + x[ 0]), 9);
x[12] ^= rol32((x[ 8] + x[ 4]), 13); x[12] ^= rol32((x[ 8] + x[ 4]), 13);
@ -95,145 +73,135 @@ static void salsa20_wordtobyte(u8 output[64], const u32 input[16])
x[14] ^= rol32((x[13] + x[12]), 13); x[14] ^= rol32((x[13] + x[12]), 13);
x[15] ^= rol32((x[14] + x[13]), 18); x[15] ^= rol32((x[14] + x[13]), 18);
} }
for (i = 0; i < 16; ++i)
x[i] += input[i]; for (i = 0; i < 16; i++)
for (i = 0; i < 16; ++i) stream[i] = cpu_to_le32(x[i] + state[i]);
U32TO8_LITTLE(output + 4 * i,x[i]);
if (++state[8] == 0)
state[9]++;
} }
static const char sigma[16] = "expand 32-byte k"; static void salsa20_docrypt(u32 *state, u8 *dst, const u8 *src,
static const char tau[16] = "expand 16-byte k"; unsigned int bytes)
static void salsa20_keysetup(struct salsa20_ctx *ctx, const u8 *k, u32 kbytes)
{ {
const char *constants; __le32 stream[SALSA20_BLOCK_SIZE / sizeof(__le32)];
ctx->input[1] = U8TO32_LITTLE(k + 0);
ctx->input[2] = U8TO32_LITTLE(k + 4);
ctx->input[3] = U8TO32_LITTLE(k + 8);
ctx->input[4] = U8TO32_LITTLE(k + 12);
if (kbytes == 32) { /* recommended */
k += 16;
constants = sigma;
} else { /* kbytes == 16 */
constants = tau;
}
ctx->input[11] = U8TO32_LITTLE(k + 0);
ctx->input[12] = U8TO32_LITTLE(k + 4);
ctx->input[13] = U8TO32_LITTLE(k + 8);
ctx->input[14] = U8TO32_LITTLE(k + 12);
ctx->input[0] = U8TO32_LITTLE(constants + 0);
ctx->input[5] = U8TO32_LITTLE(constants + 4);
ctx->input[10] = U8TO32_LITTLE(constants + 8);
ctx->input[15] = U8TO32_LITTLE(constants + 12);
}
static void salsa20_ivsetup(struct salsa20_ctx *ctx, const u8 *iv)
{
ctx->input[6] = U8TO32_LITTLE(iv + 0);
ctx->input[7] = U8TO32_LITTLE(iv + 4);
ctx->input[8] = 0;
ctx->input[9] = 0;
}
static void salsa20_encrypt_bytes(struct salsa20_ctx *ctx, u8 *dst,
const u8 *src, unsigned int bytes)
{
u8 buf[64];
if (dst != src) if (dst != src)
memcpy(dst, src, bytes); memcpy(dst, src, bytes);
while (bytes) { while (bytes >= SALSA20_BLOCK_SIZE) {
salsa20_wordtobyte(buf, ctx->input); salsa20_block(state, stream);
crypto_xor(dst, (const u8 *)stream, SALSA20_BLOCK_SIZE);
ctx->input[8]++; bytes -= SALSA20_BLOCK_SIZE;
if (!ctx->input[8]) dst += SALSA20_BLOCK_SIZE;
ctx->input[9]++;
if (bytes <= 64) {
crypto_xor(dst, buf, bytes);
return;
} }
if (bytes) {
crypto_xor(dst, buf, 64); salsa20_block(state, stream);
bytes -= 64; crypto_xor(dst, (const u8 *)stream, bytes);
dst += 64;
} }
} }
/* static void salsa20_init(u32 *state, const struct salsa20_ctx *ctx,
* End of code taken from D. J. Bernstein's reference implementation. const u8 *iv)
*/ {
memcpy(state, ctx->initial_state, sizeof(ctx->initial_state));
state[6] = get_unaligned_le32(iv + 0);
state[7] = get_unaligned_le32(iv + 4);
}
static int setkey(struct crypto_tfm *tfm, const u8 *key, static int salsa20_setkey(struct crypto_skcipher *tfm, const u8 *key,
unsigned int keysize) unsigned int keysize)
{ {
struct salsa20_ctx *ctx = crypto_tfm_ctx(tfm); static const char sigma[16] = "expand 32-byte k";
salsa20_keysetup(ctx, key, keysize); static const char tau[16] = "expand 16-byte k";
struct salsa20_ctx *ctx = crypto_skcipher_ctx(tfm);
const char *constants;
if (keysize != SALSA20_MIN_KEY_SIZE &&
keysize != SALSA20_MAX_KEY_SIZE)
return -EINVAL;
ctx->initial_state[1] = get_unaligned_le32(key + 0);
ctx->initial_state[2] = get_unaligned_le32(key + 4);
ctx->initial_state[3] = get_unaligned_le32(key + 8);
ctx->initial_state[4] = get_unaligned_le32(key + 12);
if (keysize == 32) { /* recommended */
key += 16;
constants = sigma;
} else { /* keysize == 16 */
constants = tau;
}
ctx->initial_state[11] = get_unaligned_le32(key + 0);
ctx->initial_state[12] = get_unaligned_le32(key + 4);
ctx->initial_state[13] = get_unaligned_le32(key + 8);
ctx->initial_state[14] = get_unaligned_le32(key + 12);
ctx->initial_state[0] = get_unaligned_le32(constants + 0);
ctx->initial_state[5] = get_unaligned_le32(constants + 4);
ctx->initial_state[10] = get_unaligned_le32(constants + 8);
ctx->initial_state[15] = get_unaligned_le32(constants + 12);
/* space for the nonce; it will be overridden for each request */
ctx->initial_state[6] = 0;
ctx->initial_state[7] = 0;
/* initial block number */
ctx->initial_state[8] = 0;
ctx->initial_state[9] = 0;
return 0; return 0;
} }
static int encrypt(struct blkcipher_desc *desc, static int salsa20_crypt(struct skcipher_request *req)
struct scatterlist *dst, struct scatterlist *src,
unsigned int nbytes)
{ {
struct blkcipher_walk walk; struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
struct crypto_blkcipher *tfm = desc->tfm; const struct salsa20_ctx *ctx = crypto_skcipher_ctx(tfm);
struct salsa20_ctx *ctx = crypto_blkcipher_ctx(tfm); struct skcipher_walk walk;
u32 state[16];
int err; int err;
blkcipher_walk_init(&walk, dst, src, nbytes); err = skcipher_walk_virt(&walk, req, true);
err = blkcipher_walk_virt_block(desc, &walk, 64);
salsa20_ivsetup(ctx, walk.iv); salsa20_init(state, ctx, walk.iv);
while (walk.nbytes >= 64) { while (walk.nbytes > 0) {
salsa20_encrypt_bytes(ctx, walk.dst.virt.addr, unsigned int nbytes = walk.nbytes;
walk.src.virt.addr,
walk.nbytes - (walk.nbytes % 64));
err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64);
}
if (walk.nbytes) { if (nbytes < walk.total)
salsa20_encrypt_bytes(ctx, walk.dst.virt.addr, nbytes = round_down(nbytes, walk.stride);
walk.src.virt.addr, walk.nbytes);
err = blkcipher_walk_done(desc, &walk, 0); salsa20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
nbytes);
err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
} }
return err; return err;
} }
static struct crypto_alg alg = { static struct skcipher_alg alg = {
.cra_name = "salsa20", .base.cra_name = "salsa20",
.cra_driver_name = "salsa20-generic", .base.cra_driver_name = "salsa20-generic",
.cra_priority = 100, .base.cra_priority = 100,
.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER, .base.cra_blocksize = 1,
.cra_type = &crypto_blkcipher_type, .base.cra_ctxsize = sizeof(struct salsa20_ctx),
.cra_blocksize = 1, .base.cra_module = THIS_MODULE,
.cra_ctxsize = sizeof(struct salsa20_ctx),
.cra_alignmask = 3,
.cra_module = THIS_MODULE,
.cra_u = {
.blkcipher = {
.setkey = setkey,
.encrypt = encrypt,
.decrypt = encrypt,
.min_keysize = SALSA20_MIN_KEY_SIZE, .min_keysize = SALSA20_MIN_KEY_SIZE,
.max_keysize = SALSA20_MAX_KEY_SIZE, .max_keysize = SALSA20_MAX_KEY_SIZE,
.ivsize = SALSA20_IV_SIZE, .ivsize = SALSA20_IV_SIZE,
} .chunksize = SALSA20_BLOCK_SIZE,
} .setkey = salsa20_setkey,
.encrypt = salsa20_crypt,
.decrypt = salsa20_crypt,
}; };
static int __init salsa20_generic_mod_init(void) static int __init salsa20_generic_mod_init(void)
{ {
return crypto_register_alg(&alg); return crypto_register_skcipher(&alg);
} }
static void __exit salsa20_generic_mod_fini(void) static void __exit salsa20_generic_mod_fini(void)
{ {
crypto_unregister_alg(&alg); crypto_unregister_skcipher(&alg);
} }
module_init(salsa20_generic_mod_init); module_init(salsa20_generic_mod_init);