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crypto: chacha20 - Fix chacha20_block() keystream alignment (again) 

In commit 9f480faec5 ("crypto: chacha20 - Fix keystream alignment for
chacha20_block()"), I had missed that chacha20_block() can be called
directly on the buffer passed to get_random_bytes(), which can have any
alignment.  So, while my commit didn't break anything, it didn't fully
solve the alignment problems.

Revert my solution and just update chacha20_block() to use
put_unaligned_le32(), so the output buffer need not be aligned.
This is simpler, and on many CPUs it's the same speed.

But, I kept the 'tmp' buffers in extract_crng_user() and
_get_random_bytes() 4-byte aligned, since that alignment is actually
needed for _crng_backtrack_protect() too.

Reported-by: Stephan Müller <smueller@chronox.de>
Cc: Theodore Ts'o <tytso@mit.edu>
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 2018-09-11 20:05:10 -07:00 committed by Herbert Xu
parent 78105c7e76
commit a5e9f55709
4 changed files with 20 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
crypto/chacha20_generic.c
View File

@ -18,20 +18,21 @@
static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
unsigned int bytes)
{
u32 stream[CHACHA20_BLOCK_WORDS];
/* aligned to potentially speed up crypto_xor() */
u8 stream[CHACHA20_BLOCK_SIZE] __aligned(sizeof(long));
if (dst != src)
memcpy(dst, src, bytes);
while (bytes >= CHACHA20_BLOCK_SIZE) {
chacha20_block(state, stream);
crypto_xor(dst, (const u8 *)stream, CHACHA20_BLOCK_SIZE);
crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE);
bytes -= CHACHA20_BLOCK_SIZE;
dst += CHACHA20_BLOCK_SIZE;
}
if (bytes) {
chacha20_block(state, stream);
crypto_xor(dst, (const u8 *)stream, bytes);
crypto_xor(dst, stream, bytes);
}
}

24
drivers/char/random.c
View File

@ -433,9 +433,9 @@ static int crng_init_cnt = 0;
static unsigned long crng_global_init_time = 0;
#define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE)
static void _extract_crng(struct crng_state *crng,
__u32 out[CHACHA20_BLOCK_WORDS]);
__u8 out[CHACHA20_BLOCK_SIZE]);
static void _crng_backtrack_protect(struct crng_state *crng,
__u32 tmp[CHACHA20_BLOCK_WORDS], int used);
__u8 tmp[CHACHA20_BLOCK_SIZE], int used);
static void process_random_ready_list(void);
static void _get_random_bytes(void *buf, int nbytes);
@ -921,7 +921,7 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
unsigned long flags;
int i, num;
union {
__u32 block[CHACHA20_BLOCK_WORDS];
__u8 block[CHACHA20_BLOCK_SIZE];
__u32 key[8];
} buf;
@ -968,7 +968,7 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
}
static void _extract_crng(struct crng_state *crng,
__u32 out[CHACHA20_BLOCK_WORDS])
__u8 out[CHACHA20_BLOCK_SIZE])
{
unsigned long v, flags;
@ -985,7 +985,7 @@ static void _extract_crng(struct crng_state *crng,
spin_unlock_irqrestore(&crng->lock, flags);
}
static void extract_crng(__u32 out[CHACHA20_BLOCK_WORDS])
static void extract_crng(__u8 out[CHACHA20_BLOCK_SIZE])
{
struct crng_state *crng = NULL;
@ -1003,7 +1003,7 @@ static void extract_crng(__u32 out[CHACHA20_BLOCK_WORDS])
* enough) to mutate the CRNG key to provide backtracking protection.
*/
static void _crng_backtrack_protect(struct crng_state *crng,
__u32 tmp[CHACHA20_BLOCK_WORDS], int used)
__u8 tmp[CHACHA20_BLOCK_SIZE], int used)
{
unsigned long flags;
__u32 *s, *d;
@ -1015,14 +1015,14 @@ static void _crng_backtrack_protect(struct crng_state *crng,
used = 0;
}
spin_lock_irqsave(&crng->lock, flags);
s = &tmp[used / sizeof(__u32)];
s = (__u32 *) &tmp[used];
d = &crng->state[4];
for (i=0; i < 8; i++)
*d++ ^= *s++;
spin_unlock_irqrestore(&crng->lock, flags);
}
static void crng_backtrack_protect(__u32 tmp[CHACHA20_BLOCK_WORDS], int used)
static void crng_backtrack_protect(__u8 tmp[CHACHA20_BLOCK_SIZE], int used)
{
struct crng_state *crng = NULL;
@ -1038,7 +1038,7 @@ static void crng_backtrack_protect(__u32 tmp[CHACHA20_BLOCK_WORDS], int used)
static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
{
ssize_t ret = 0, i = CHACHA20_BLOCK_SIZE;
__u32 tmp[CHACHA20_BLOCK_WORDS];
__u8 tmp[CHACHA20_BLOCK_SIZE] __aligned(4);
int large_request = (nbytes > 256);
while (nbytes) {
@ -1617,7 +1617,7 @@ static void _warn_unseeded_randomness(const char *func_name, void *caller,
*/
static void _get_random_bytes(void *buf, int nbytes)
{
__u32 tmp[CHACHA20_BLOCK_WORDS];
__u8 tmp[CHACHA20_BLOCK_SIZE] __aligned(4);
trace_get_random_bytes(nbytes, _RET_IP_);
@ -2243,7 +2243,7 @@ u64 get_random_u64(void)
if (use_lock)
read_lock_irqsave(&batched_entropy_reset_lock, flags);
if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
extract_crng((__u32 *)batch->entropy_u64);
extract_crng((u8 *)batch->entropy_u64);
batch->position = 0;
}
ret = batch->entropy_u64[batch->position++];
@ -2273,7 +2273,7 @@ u32 get_random_u32(void)
if (use_lock)
read_lock_irqsave(&batched_entropy_reset_lock, flags);
if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
extract_crng(batch->entropy_u32);
extract_crng((u8 *)batch->entropy_u32);
batch->position = 0;
}
ret = batch->entropy_u32[batch->position++];

3
include/crypto/chacha20.h
View File

@ -13,13 +13,12 @@
#define CHACHA20_IV_SIZE 16
#define CHACHA20_KEY_SIZE 32
#define CHACHA20_BLOCK_SIZE 64
#define CHACHA20_BLOCK_WORDS (CHACHA20_BLOCK_SIZE / sizeof(u32))
struct chacha20_ctx {
u32 key[8];
};
void chacha20_block(u32 *state, u32 *stream);
void chacha20_block(u32 *state, u8 *stream);
void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv);
int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
unsigned int keysize);

6
lib/chacha20.c
View File

@ -16,9 +16,9 @@
#include <asm/unaligned.h>
#include <crypto/chacha20.h>
void chacha20_block(u32 *state, u32 *stream)
void chacha20_block(u32 *state, u8 *stream)
{
u32 x[16], *out = stream;
u32 x[16];
int i;
for (i = 0; i < ARRAY_SIZE(x); i++)
@ -67,7 +67,7 @@ void chacha20_block(u32 *state, u32 *stream)
}
for (i = 0; i < ARRAY_SIZE(x); i++)
out[i] = cpu_to_le32(x[i] + state[i]);
put_unaligned_le32(x[i] + state[i], &stream[i * sizeof(u32)]);
state[12]++;
}