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 <[email protected]> * * 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 <[email protected]>"); MODULE_DESCRIPTION("Key Wrapping (RFC3394 / NIST SP800-38F)"); MODULE_ALIAS_CRYPTO("kw"); Cheers, -- Email: Herbert Xu <[email protected]> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
