1 files changed, 419 insertions, 0 deletions

diff --git a/crypto/keywrap.c b/crypto/keywrap.c
new file mode 100644
index 000000000000..b1d106ce55f3
--- /dev/null
+++ b/crypto/keywrap.c
@@ -0,0 +1,419 @@
+/*
+ * 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");