diff options
Diffstat (limited to 'crypto')
| -rw-r--r-- | crypto/keywrap.c | 419 |
1 files changed, 419 insertions, 0 deletions
diff --git a/crypto/keywrap.c b/crypto/keywrap.c new file mode 100644 index 0000000..b1d106c --- /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"); |
