Skip to content

Commit

Permalink
crypto: keywrap - simplify code
Browse files Browse the repository at this point in the history 
The code is simplified by using two __be64 values for the operation
instead of using two arrays of u8. This allows to get rid of the memory
alignment code. In addition, the crypto_xor can be replaced with a
native XOR operation. Finally, the definition of the variables is
re-arranged such that the data structures come before simple variables
to potentially reduce memory space.

Signed-off-by: Stephan Mueller <[email protected]>
Signed-off-by: Herbert Xu <[email protected]>
  • Loading branch information
@smuellerDD @herbertx
smuellerDD authored and herbertx committed Oct 12, 2017
1 parent 5b3f3a8 commit 9e49451
Showing 1 changed file with 26 additions and 58 deletions.
84 changes: 26 additions & 58 deletions crypto/keywrap.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -93,18 +93,10 @@ struct crypto_kw_ctx {

struct crypto_kw_block {
#define SEMIBSIZE 8
u8 A[SEMIBSIZE];
u8 R[SEMIBSIZE];
__be64 A;
__be64 R;
};

/* convert 64 bit integer into its string representation */
static inline void crypto_kw_cpu_to_be64(u64 val, u8 *buf)
{
__be64 *a = (__be64 *)buf;

*a = cpu_to_be64(val);
}

/*
* Fast forward the SGL to the "end" length minus SEMIBSIZE.
* The start in the SGL defined by the fast-forward is returned with
Expand Down Expand Up @@ -139,17 +131,10 @@ static int crypto_kw_decrypt(struct blkcipher_desc *desc,
struct crypto_blkcipher *tfm = desc->tfm;
struct crypto_kw_ctx *ctx = crypto_blkcipher_ctx(tfm);
struct crypto_cipher *child = ctx->child;

unsigned long alignmask = max_t(unsigned long, SEMIBSIZE,
crypto_cipher_alignmask(child));
unsigned int i;

u8 blockbuf[sizeof(struct crypto_kw_block) + alignmask];
struct crypto_kw_block *block = (struct crypto_kw_block *)
PTR_ALIGN(blockbuf + 0, alignmask + 1);

u64 t = 6 * ((nbytes) >> 3);
struct crypto_kw_block block;
struct scatterlist *lsrc, *ldst;
u64 t = 6 * ((nbytes) >> 3);
unsigned int i;
int ret = 0;

/*
Expand All @@ -160,7 +145,7 @@ static int crypto_kw_decrypt(struct blkcipher_desc *desc,
return -EINVAL;

/* Place the IV into block A */
memcpy(block->A, desc->info, SEMIBSIZE);
memcpy(&block.A, desc->info, SEMIBSIZE);

/*
* src scatterlist is read-only. dst scatterlist is r/w. During the
Expand All @@ -171,32 +156,27 @@ static int crypto_kw_decrypt(struct blkcipher_desc *desc,
ldst = dst;

for (i = 0; i < 6; i++) {
u8 tbe_buffer[SEMIBSIZE + alignmask];
/* alignment for the crypto_xor and the _to_be64 operation */
u8 *tbe = PTR_ALIGN(tbe_buffer + 0, alignmask + 1);
unsigned int tmp_nbytes = nbytes;
struct scatter_walk src_walk, dst_walk;
unsigned int tmp_nbytes = nbytes;

while (tmp_nbytes) {
/* move pointer by tmp_nbytes in the SGL */
crypto_kw_scatterlist_ff(&src_walk, lsrc, tmp_nbytes);
/* get the source block */
scatterwalk_copychunks(block->R, &src_walk, SEMIBSIZE,
scatterwalk_copychunks(&block.R, &src_walk, SEMIBSIZE,
false);

/* perform KW operation: get counter as byte string */
crypto_kw_cpu_to_be64(t, tbe);
/* perform KW operation: modify IV with counter */
crypto_xor(block->A, tbe, SEMIBSIZE);
block.A ^= cpu_to_be64(t);
t--;
/* perform KW operation: decrypt block */
crypto_cipher_decrypt_one(child, (u8*)block,
(u8*)block);
crypto_cipher_decrypt_one(child, (u8*)&block,
(u8*)&block);

/* move pointer by tmp_nbytes in the SGL */
crypto_kw_scatterlist_ff(&dst_walk, ldst, tmp_nbytes);
/* Copy block->R into place */
scatterwalk_copychunks(block->R, &dst_walk, SEMIBSIZE,
scatterwalk_copychunks(&block.R, &dst_walk, SEMIBSIZE,
true);

tmp_nbytes -= SEMIBSIZE;
Expand All @@ -208,11 +188,10 @@ static int crypto_kw_decrypt(struct blkcipher_desc *desc,
}

/* Perform authentication check */
if (crypto_memneq("\xA6\xA6\xA6\xA6\xA6\xA6\xA6\xA6", block->A,
SEMIBSIZE))
if (block.A != cpu_to_be64(0xa6a6a6a6a6a6a6a6))
ret = -EBADMSG;

memzero_explicit(block, sizeof(struct crypto_kw_block));
memzero_explicit(&block, sizeof(struct crypto_kw_block));

return ret;
}
Expand All @@ -224,17 +203,10 @@ static int crypto_kw_encrypt(struct blkcipher_desc *desc,
struct crypto_blkcipher *tfm = desc->tfm;
struct crypto_kw_ctx *ctx = crypto_blkcipher_ctx(tfm);
struct crypto_cipher *child = ctx->child;

unsigned long alignmask = max_t(unsigned long, SEMIBSIZE,
crypto_cipher_alignmask(child));
unsigned int i;

u8 blockbuf[sizeof(struct crypto_kw_block) + alignmask];
struct crypto_kw_block *block = (struct crypto_kw_block *)
PTR_ALIGN(blockbuf + 0, alignmask + 1);

u64 t = 1;
struct crypto_kw_block block;
struct scatterlist *lsrc, *ldst;
u64 t = 1;
unsigned int i;

/*
* Require at least 2 semiblocks (note, the 3rd semiblock that is
Expand All @@ -249,7 +221,7 @@ static int crypto_kw_encrypt(struct blkcipher_desc *desc,
* Place the predefined IV into block A -- for encrypt, the caller
* does not need to provide an IV, but he needs to fetch the final IV.
*/
memcpy(block->A, "\xA6\xA6\xA6\xA6\xA6\xA6\xA6\xA6", SEMIBSIZE);
block.A = cpu_to_be64(0xa6a6a6a6a6a6a6a6);

/*
* src scatterlist is read-only. dst scatterlist is r/w. During the
Expand All @@ -260,30 +232,26 @@ static int crypto_kw_encrypt(struct blkcipher_desc *desc,
ldst = dst;

for (i = 0; i < 6; i++) {
u8 tbe_buffer[SEMIBSIZE + alignmask];
u8 *tbe = PTR_ALIGN(tbe_buffer + 0, alignmask + 1);
unsigned int tmp_nbytes = nbytes;
struct scatter_walk src_walk, dst_walk;
unsigned int tmp_nbytes = nbytes;

scatterwalk_start(&src_walk, lsrc);
scatterwalk_start(&dst_walk, ldst);

while (tmp_nbytes) {
/* get the source block */
scatterwalk_copychunks(block->R, &src_walk, SEMIBSIZE,
scatterwalk_copychunks(&block.R, &src_walk, SEMIBSIZE,
false);

/* perform KW operation: encrypt block */
crypto_cipher_encrypt_one(child, (u8 *)block,
(u8 *)block);
/* perform KW operation: get counter as byte string */
crypto_kw_cpu_to_be64(t, tbe);
crypto_cipher_encrypt_one(child, (u8 *)&block,
(u8 *)&block);
/* perform KW operation: modify IV with counter */
crypto_xor(block->A, tbe, SEMIBSIZE);
block.A ^= cpu_to_be64(t);
t++;

/* Copy block->R into place */
scatterwalk_copychunks(block->R, &dst_walk, SEMIBSIZE,
scatterwalk_copychunks(&block.R, &dst_walk, SEMIBSIZE,
true);

tmp_nbytes -= SEMIBSIZE;
Expand All @@ -295,9 +263,9 @@ static int crypto_kw_encrypt(struct blkcipher_desc *desc,
}

/* establish the IV for the caller to pick up */
memcpy(desc->info, block->A, SEMIBSIZE);
memcpy(desc->info, &block.A, SEMIBSIZE);

memzero_explicit(block, sizeof(struct crypto_kw_block));
memzero_explicit(&block, sizeof(struct crypto_kw_block));

return 0;
}
Expand Down

0 comments on commit 9e49451

Please sign in to comment.