--- /dev/null
+/*
+ * Key Wrapping: RFC3394 / NIST SP800-38F
+ *
+ * Copyright (C) 2015, Stephan Mueller <smueller@chronox.de>
+ *
+ * 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 used 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_skcipher_ivsize(tfm);
+ * u8 data[datalen];
+ * u8 *iv = data;
+ * u8 *pt = data + crypto_skcipher_ivsize(tfm);
+ * <ensure that pt contains the plaintext of size ptlen>
+ * sg_init_one(&sg, ptdata, ptlen);
+ * skcipher_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_skcipher_ivsize(tfm);
+ * unsigned int ctlen = datalen - crypto_skcipher_ivsize(tfm);
+ * sg_init_one(&sg, ctdata, ctlen);
+ * skcipher_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.
+ *
+ * Note 2: KWP is not implemented as this would defy in-place operation.
+ * If somebody wants to wrap non-aligned data, he should simply pad
+ * the input with zeros to fill it up to the 8 byte boundary.
+ */
+
+#include <linux/module.h>
+#include <linux/crypto.h>
+#include <linux/scatterlist.h>
+#include <crypto/scatterwalk.h>
+#include <crypto/internal/skcipher.h>
+
+struct crypto_kw_ctx {
+ struct crypto_cipher *child;
+};
+
+struct crypto_kw_block {
+#define SEMIBSIZE 8
+ u8 A[SEMIBSIZE];
+ u8 R[SEMIBSIZE];
+};
+
+/* 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
+ * the walk variable
+ */
+static void crypto_kw_scatterlist_ff(struct scatter_walk *walk,
+ struct scatterlist *sg,
+ unsigned int end)
+{
+ unsigned int skip = 0;
+
+ /* The caller should only operate on full SEMIBLOCKs. */
+ BUG_ON(end < SEMIBSIZE);
+
+ skip = end - SEMIBSIZE;
+ while (sg) {
+ if (sg->length > skip) {
+ scatterwalk_start(walk, sg);
+ scatterwalk_advance(walk, skip);
+ break;
+ } else
+ skip -= sg->length;
+
+ sg = sg_next(sg);
+ }
+}
+
+static int crypto_kw_decrypt(struct blkcipher_desc *desc,
+ struct scatterlist *dst, struct scatterlist *src,
+ unsigned int nbytes)
+{
+ 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 scatterlist *lsrc, *ldst;
+ int ret = 0;
+
+ /*
+ * 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;
+
+ /* Place the IV into block A */
+ memcpy(block->A, desc->info, SEMIBSIZE);
+
+ /*
+ * src scatterlist is read-only. dst scatterlist is r/w. During the
+ * first loop, lsrc points to src and ldst to dst. For any
+ * subsequent round, the code operates on dst only.
+ */
+ lsrc = src;
+ 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;
+
+ 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,
+ 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);
+ t--;
+ /* perform KW operation: decrypt 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,
+ true);
+
+ tmp_nbytes -= SEMIBSIZE;
+ }
+
+ /* we now start to operate on the dst SGL only */
+ lsrc = dst;
+ ldst = dst;
+ }
+
+ /* Perform authentication check */
+ if (crypto_memneq("\xA6\xA6\xA6\xA6\xA6\xA6\xA6\xA6", block->A,
+ SEMIBSIZE))
+ ret = -EBADMSG;
+
+ memzero_explicit(&block, sizeof(struct crypto_kw_block));
+
+ return ret;
+}
+
+static int crypto_kw_encrypt(struct blkcipher_desc *desc,
+ struct scatterlist *dst, struct scatterlist *src,
+ unsigned int nbytes)
+{
+ 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 scatterlist *lsrc, *ldst;
+
+ /*
+ * 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;
+
+ /*
+ * 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);
+
+ /*
+ * src scatterlist is read-only. dst scatterlist is r/w. During the
+ * first loop, lsrc points to src and ldst to dst. For any
+ * subsequent round, the code operates on dst only.
+ */
+ lsrc = src;
+ 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;
+
+ scatterwalk_start(&src_walk, lsrc);
+ scatterwalk_start(&dst_walk, ldst);
+
+ while (tmp_nbytes) {
+ /* get the source block */
+ 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);
+ /* perform KW operation: modify IV with counter */
+ crypto_xor(block->A, tbe, SEMIBSIZE);
+ t++;
+
+ /* Copy block->R into place */
+ scatterwalk_copychunks(block->R, &dst_walk, SEMIBSIZE,
+ true);
+
+ tmp_nbytes -= SEMIBSIZE;
+ }
+
+ /* we now start to operate on the dst SGL only */
+ lsrc = dst;
+ ldst = dst;
+ }
+
+ /* establish the IV for the caller to pick up */
+ memcpy(desc->info, block->A, SEMIBSIZE);
+
+ memzero_explicit(&block, sizeof(struct crypto_kw_block));
+
+ return 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_BLKCIPHER);
+ 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 */
+ if (alg->cra_blocksize != sizeof(struct crypto_kw_block))
+ goto err;
+
+ inst = crypto_alloc_instance("kw", alg);
+ if (IS_ERR(inst))
+ goto err;
+
+ inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
+ inst->alg.cra_priority = alg->cra_priority;
+ inst->alg.cra_blocksize = SEMIBSIZE;
+ inst->alg.cra_alignmask = 0;
+ inst->alg.cra_type = &crypto_blkcipher_type;
+ inst->alg.cra_blkcipher.ivsize = SEMIBSIZE;
+ inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
+ inst->alg.cra_blkcipher.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_blkcipher.setkey = crypto_kw_setkey;
+ inst->alg.cra_blkcipher.encrypt = crypto_kw_encrypt;
+ inst->alg.cra_blkcipher.decrypt = crypto_kw_decrypt;
+
+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@chronox.de>");
+MODULE_DESCRIPTION("Key Wrapping (RFC3394 / NIST SP800-38F)");
+MODULE_ALIAS_CRYPTO("kw");
projects / users / hch / xfs.git / commitdiff