On Sun, Apr 26, 2015 at 12:08:20AM +0200, Stephan Mueller wrote:
> This patch implements the AES key wrapping as specified in
> NIST SP800-38F and RFC3394.
This is my attempt at turning kw into a givcipher. The encrypt
part is complete but untested as I gave up after finding the
reverse SG problem with your decrypt code.
/*
* Key Wrapping: RFC3394 / NIST SP800-38F
*
* Implemented modes as defined in NIST SP800-38F: Kw
*
* Copyright (C) 2015, Stephan Mueller <smueller@xxxxxxxxxx>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, and the entire permission notice in its entirety,
* including the disclaimer of warranties.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* ALTERNATIVELY, this product may be distributed under the terms of
* the GNU General Public License, in which case the provisions of the GPL2
* are required INSTEAD OF the above restrictions. (This clause is
* necessary due to a potential bad interaction between the GPL and
* the restrictions contained in a BSD-style copyright.)
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
* WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
* USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*/
/*
* Note for using key wrapping:
*
* * The result of the encryption operation is the ciphertext starting
* with the 2nd semiblock. The first semiblock is provided as the IV.
* The IV uses to start the encryption operation is the default IV.
*
* * The input for the decryption is the first semiblock handed in as an
* IV. The ciphertext is the data starting with the 2nd semiblock. The
* return code of the decryption operation will be EBADMSG in case an
* integrity error occurs.
*
* To obtain the full result of an encryption as expected by SP800-38F, the
* caller must allocate a buffer of plaintext + 8 bytes:
*
* unsigned int datalen = ptlen + crypto_ablkcipher_ivsize(tfm);
* u8 data[datalen];
* u8 *iv = data;
* u8 *pt = data + crypto_ablkcipher_ivsize(tfm);
* <ensure that pt contains the plaintext of size ptlen>
* sg_init_one(&sg, ptdata, ptlen);
* ablkcipher_request_set_crypt(req, &sg, &sg, ptlen, iv);
*
* ==> After encryption, data now contains full KW result as per SP800-38F.
*
* In case of decryption, ciphertext now already has the expected length
* and must be segmented appropriately:
*
* unsigned int datalen = CTLEN;
* u8 data[datalen];
* <ensure that data contains full ciphertext>
* u8 *iv = data;
* u8 *ct = data + crypto_ablkcipher_ivsize(tfm);
* unsigned int ctlen = datalen - crypto_ablkcipher_ivsize(tfm);
* sg_init_one(&sg, ctdata, ctlen);
* ablkcipher_request_set_crypt(req, &sg, &sg, ptlen, iv);
*
* ==> After decryption (which hopefully does not return EBADMSG), the ct
* pointer now points to the plaintext of size ctlen.
*/
#include <crypto/internal/skcipher.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
struct crypto_kw_ctx {
struct crypto_cipher *child;
};
struct crypto_rfc3394_ctx {
struct crypto_ablkcipher *child;
};
struct crypto_kw_block {
#define SEMIBSIZE sizeof(be64)
union {
struct {
be64 A;
be64 R;
};
u8 V[];
};
};
/* convert 64 bit integer into its string representation */
static inline void crypto_kw_cpu_to_be64(u64 val, u8 *buf)
{
struct s {
__be64 conv;
};
struct s *conversion = (struct s *) buf;
conversion->conv = cpu_to_be64(val);
}
static inline void crypto_kw_copy_scatterlist(struct scatterlist *src,
struct scatterlist *dst)
{
memcpy(dst, src, sizeof(struct scatterlist));
}
/* find the next memory block in scatter_walk of given size */
static inline bool crypto_kw_scatterwalk_find(struct scatter_walk *walk,
unsigned int size)
{
int n = scatterwalk_clamp(walk, size);
if (!n) {
scatterwalk_start(walk, sg_next(walk->sg));
n = scatterwalk_clamp(walk, size);
}
if (n != size)
return false;
return true;
}
/*
* Copy out the memory block from or to scatter_walk of requested size
* before the walk->offset pointer. The scatter_walk is processed in reverse.
*/
static bool crypto_kw_scatterwalk_memcpy_rev(struct scatter_walk *walk,
unsigned int *walklen,
u8 *buf, unsigned int bufsize,
bool out)
{
u8 *ptr = NULL;
walk->offset -= bufsize;
if (!crypto_kw_scatterwalk_find(walk, bufsize))
return false;
ptr = scatterwalk_map(walk);
if (out)
memcpy(ptr, buf, bufsize);
else
memcpy(buf, ptr, bufsize);
*walklen -= bufsize;
scatterwalk_unmap(ptr);
scatterwalk_done(walk, 0, *walklen);
return true;
}
/*
* Copy the memory block from or to scatter_walk of requested size
* at the walk->offset pointer. The scatter_walk is processed forward.
*/
static bool crypto_kw_scatterwalk_memcpy(struct scatter_walk *walk,
unsigned int *walklen,
u8 *buf, unsigned int bufsize,
bool out)
{
u8 *ptr = NULL;
if (!crypto_kw_scatterwalk_find(walk, bufsize))
return false;
ptr = scatterwalk_map(walk);
if (out)
memcpy(ptr, buf, bufsize);
else
memcpy(buf, ptr, bufsize);
*walklen -= bufsize;
scatterwalk_unmap(ptr);
scatterwalk_advance(walk, bufsize);
scatterwalk_done(walk, 0, *walklen);
return true;
}
static int crypto_kw_decrypt(struct ablkcipher_request *req)
{
struct scatterlist *src = req->src;
struct scatterlist *dst = req->dst;
unsigned int nbytes = req->nbytes;
struct crypto_ablkcipher *tfm = crypto_ablkcipher_tfm(req);
struct crypto_kw_ctx *ctx = crypto_ablkcipher_ctx(tfm);
struct crypto_cipher *child = ctx->child;
unsigned long alignmask = crypto_cipher_alignmask(child) | 7;
unsigned int i;
struct blkcipher_walk walk;
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);
int ret;
/*
* Require at least 2 semiblocks (note, the 3rd semiblock that is
* required by SP800-38F is the IV.
*/
if (nbytes < (2 * SEMIBSIZE) || nbytes % SEMIBSIZE)
return -EINVAL;
/*
* src scatterlist is read only. dst scatterlist is r/w. During the
* first loop, src points to req->src and dst to req->dst. For any
* subsequent round, the code operates on req->dst only.
*/
for (i = 0; i < 6; i++) {
be64 tbe;
blkcipher_walk_init(&walk, dst, src, nbytes);
ret = blkcipher_walk_virt_ablkcipher(req, &walk);
if (ret)
goto out;
/*
* Point to the end of the scatterlists to walk them backwards.
*/
src_walk.offset += src_nbytes;
dst_walk.offset += dst_nbytes;
while (src_nbytes) {
if (!crypto_kw_scatterwalk_memcpy_rev(&src_walk,
&src_nbytes, block->R, SEMIBSIZE, false))
goto out;
crypto_kw_cpu_to_be64(t, tbe);
crypto_xor(block->A, tbe, SEMIBSIZE);
t--;
crypto_cipher_decrypt_one(child, (u8*)block,
(u8*)block);
if (!first_loop) {
/*
* Copy block->R from last round into
* place.
*/
if (!crypto_kw_scatterwalk_memcpy_rev(&dst_walk,
&dst_nbytes, tmpblock, SEMIBSIZE, true))
goto out;
} else {
first_loop = false;
}
/*
* Store current block->R in temp buffer to
* copy it in place in the next round.
*/
memcpy(&tmpblock, block->R, SEMIBSIZE);
}
/* process the final block->R */
if (!crypto_kw_scatterwalk_memcpy_rev(&dst_walk, &dst_nbytes,
tmpblock, SEMIBSIZE, true))
goto out;
/* we now start to operate on the dst buffers only */
crypto_kw_copy_scatterlist(dst, &lsrc);
crypto_kw_copy_scatterlist(dst, &ldst);
}
if (crypto_memneq("\xA6\xA6\xA6\xA6\xA6\xA6\xA6\xA6", block->A,
SEMIBSIZE))
ret = -EBADMSG;
out:
memzero_explicit(&block, sizeof(struct crypto_kw_block));
memzero_explicit(tmpblock, sizeof(tmpblock));
return ret;
}
static int crypto_kw_encrypt(struct ablkcipher_request *req)
{
struct scatterlist *src = req->src;
struct scatterlist *dst = req->dst;
unsigned int nbytes = req->nbytes;
struct crypto_ablkcipher *tfm = crypto_ablkcipher_tfm(req);
struct crypto_kw_ctx *ctx = crypto_ablkcipher_ctx(tfm);
struct crypto_cipher *child = ctx->child;
unsigned long alignmask = crypto_cipher_alignmask(child) | 7;
unsigned int i;
struct blkcipher_walk walk;
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;
int ret;
/*
* Require at least 2 semiblocks (note, the 3rd semiblock that is
* required by SP800-38F is the IV that occupies the first semiblock.
* This means that the dst memory must be one semiblock larger than src.
* Also ensure that the given data is aligned to semiblock.
*/
if (nbytes < (2 * SEMIBSIZE) || nbytes % SEMIBSIZE)
return -EINVAL;
/*
* src scatterlist is read only. dst scatterlist is r/w. During the
* first loop, src points to req->src and dst to req->dst. For any
* subsequent round, the code operates on req->dst only.
*/
for (i = 0; i < 6; i++) {
be64 tbe;
blkcipher_walk_init(&walk, dst, src, nbytes);
ret = blkcipher_walk_virt_ablkcipher(req, &walk);
if (ret)
goto out;
while (walk.nbytes) {
unsigned int leftover = walk.nbytes;
be64 *vsrc = (be64 *)walk->src.virt.addr;
block->A = *(be64 *)walk->iv;
do {
block->R = *vsrc++;
crypto_cipher_encrypt_one(child, block->V,
block->V);
*vdst++ = block->R;
tbe = cpu_to_be64(t++);
crypto_xor(block->A, tbe, SEMIBSIZE);
} while ((leftover -= SEMIBSIZE) >= bsize);
*(be64 *)walk->iv = block->A;
ret = blkcipher_walk_done(desc, &walk, nbytes);
if (ret)
goto out;
}
/* we now start to operate on the dst buffers only */
dst = src;
}
ret = 0;
out:
memzero_explicit(&block, sizeof(struct crypto_kw_block));
return ret;
}
static int crypto_kw_givencrypt(struct skcipher_givcrypt_request *req)
{
memcpy(req->giv, "\xA6\xA6\xA6\xA6\xA6\xA6\xA6\xA6", SEMIBSIZE);
memcpy(req->creq.info, req->giv, SEMIBSIZE);
return crypto_kw_encrypt(&req->creq);
}
static int crypto_kw_givdecrypt(struct skcipher_givcrypt_request *req)
{
int err = crypto_kw_decrypt(&req->creq);
if (err)
return err;
return memcmp(req->creq.info, "\xA6\xA6\xA6\xA6\xA6\xA6\xA6\xA6",
SEMIBSIZE) ? -EBADMSG : 0;
}
static int crypto_kw_setkey(struct crypto_tfm *parent, const u8 *key,
unsigned int keylen)
{
struct crypto_kw_ctx *ctx = crypto_tfm_ctx(parent);
struct crypto_cipher *child = ctx->child;
int err;
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_kw_init_tfm(struct crypto_tfm *tfm)
{
struct crypto_instance *inst = crypto_tfm_alg_instance(tfm);
struct crypto_spawn *spawn = crypto_instance_ctx(inst);
struct crypto_kw_ctx *ctx = crypto_tfm_ctx(tfm);
struct crypto_cipher *cipher;
cipher = crypto_spawn_cipher(spawn);
if (IS_ERR(cipher))
return PTR_ERR(cipher);
ctx->child = cipher;
return 0;
}
static void crypto_kw_exit_tfm(struct crypto_tfm *tfm)
{
struct crypto_kw_ctx *ctx = crypto_tfm_ctx(tfm);
crypto_free_cipher(ctx->child);
}
static struct crypto_instance *crypto_kw_alloc(struct rtattr **tb)
{
struct crypto_instance *inst = NULL;
struct crypto_alg *alg = NULL;
int err;
err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_GIVCIPHER |
CRYPTO_ALG_GENIV);
if (err)
return ERR_PTR(err);
alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
CRYPTO_ALG_TYPE_MASK);
if (IS_ERR(alg))
return ERR_CAST(alg);
inst = ERR_PTR(-EINVAL);
/* Section 5.1 requirement for KW and KWP */
if (alg->cra_blocksize != 2 * SEMIBSIZE)
goto err;
inst = crypto_alloc_instance("kw", alg);
if (IS_ERR(inst))
goto err;
inst->alg.cra_flags = CRYPTO_ALG_TYPE_GIVCIPHER | CRYPTO_ALG_GENIV;
inst->alg.cra_priority = alg->cra_priority;
inst->alg.cra_blocksize = SEMIBSIZE;
inst->alg.cra_alignmask = 7;
inst->alg.cra_type = &crypto_givcipher_type;
inst->alg.cra_ablkcipher.ivsize = SEMIBSIZE;
inst->alg.cra_ablkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
inst->alg.cra_ablkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
inst->alg.cra_ctxsize = sizeof(struct crypto_kw_ctx);
inst->alg.cra_init = crypto_kw_init_tfm;
inst->alg.cra_exit = crypto_kw_exit_tfm;
inst->alg.cra_ablkcipher.setkey = crypto_kw_setkey;
inst->alg.cra_ablkcipher.encrypt = crypto_kw_encrypt;
inst->alg.cra_ablkcipher.decrypt = crypto_kw_decrypt;
inst->alg.cra_ablkcipher.givencrypt = crypto_kw_givencrypt;
inst->alg.cra_ablkcipher.givdecrypt = crypto_kw_givdecrypt;
err:
crypto_mod_put(alg);
return inst;
}
static void crypto_kw_free(struct crypto_instance *inst)
{
crypto_drop_spawn(crypto_instance_ctx(inst));
kfree(inst);
}
static struct crypto_template crypto_kw_tmpl = {
.name = "kw",
.alloc = crypto_kw_alloc,
.free = crypto_kw_free,
.module = THIS_MODULE,
};
static int __init crypto_kw_init(void)
{
return crypto_register_template(&crypto_kw_tmpl);
}
static void __exit crypto_kw_exit(void)
{
crypto_unregister_template(&crypto_kw_tmpl);
}
module_init(crypto_kw_init);
module_exit(crypto_kw_exit);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Stephan Mueller <smueller@xxxxxxxxxx>");
MODULE_DESCRIPTION("Key Wrapping (RFC3394 / NIST SP800-38F)");
MODULE_ALIAS_CRYPTO("kw");
Cheers,
--
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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