// SPDX-License-Identifier: GPL-2.0-or-later /* XTS: as defined in IEEE1619/D16 * http://grouper.ieee.org/groups/1619/email/pdf00086.pdf * * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org> * * Based on ecb.c * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au> */ #include <crypto/internal/skcipher.h> #include <crypto/scatterwalk.h> #include <linux/err.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/scatterlist.h> #include <linux/slab.h> #include <crypto/xts.h> #include <crypto/b128ops.h> #include <crypto/gf128mul.h> struct xts_tfm_ctx { struct crypto_skcipher *child; struct crypto_cipher *tweak; }; struct xts_instance_ctx { struct crypto_skcipher_spawn spawn; char name[CRYPTO_MAX_ALG_NAME]; }; struct xts_request_ctx { le128 t; struct scatterlist *tail; struct scatterlist sg[2]; struct skcipher_request subreq; }; static int xts_setkey(struct crypto_skcipher *parent, const u8 *key, unsigned int keylen) { struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(parent); struct crypto_skcipher *child; struct crypto_cipher *tweak; int err; err = xts_verify_key(parent, key, keylen); if (err) return err; keylen /= 2; /* we need two cipher instances: one to compute the initial 'tweak' * by encrypting the IV (usually the 'plain' iv) and the other * one to encrypt and decrypt the data */ /* tweak cipher, uses Key2 i.e. the second half of *key */ tweak = ctx->tweak; crypto_cipher_clear_flags(tweak, CRYPTO_TFM_REQ_MASK); crypto_cipher_set_flags(tweak, crypto_skcipher_get_flags(parent) & CRYPTO_TFM_REQ_MASK); err = crypto_cipher_setkey(tweak, key + keylen, keylen); if (err) return err; /* data cipher, uses Key1 i.e. the first half of *key */ child = ctx->child; crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK); crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) & CRYPTO_TFM_REQ_MASK); return crypto_skcipher_setkey(child, key, keylen); } /* * We compute the tweak masks twice (both before and after the ECB encryption or * decryption) to avoid having to allocate a temporary buffer and/or make * mutliple calls to the 'ecb(..)' instance, which usually would be slower than * just doing the gf128mul_x_ble() calls again. */ static int xts_xor_tweak(struct skcipher_request *req, bool second_pass, bool enc) { struct xts_request_ctx *rctx = skcipher_request_ctx(req); struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); const bool cts = (req->cryptlen % XTS_BLOCK_SIZE); const int bs = XTS_BLOCK_SIZE; struct skcipher_walk w; le128 t = rctx->t; int err; if (second_pass) { req = &rctx->subreq; /* set to our TFM to enforce correct alignment: */ skcipher_request_set_tfm(req, tfm); } err = skcipher_walk_virt(&w, req, false); while (w.nbytes) { unsigned int avail = w.nbytes; le128 *wsrc; le128 *wdst; wsrc = w.src.virt.addr; wdst = w.dst.virt.addr; do { if (unlikely(cts) && w.total - w.nbytes + avail < 2 * XTS_BLOCK_SIZE) { if (!enc) { if (second_pass) rctx->t = t; gf128mul_x_ble(&t, &t); } le128_xor(wdst, &t, wsrc); if (enc && second_pass) gf128mul_x_ble(&rctx->t, &t); skcipher_walk_done(&w, avail - bs); return 0; } le128_xor(wdst++, &t, wsrc++); gf128mul_x_ble(&t, &t); } while ((avail -= bs) >= bs); err = skcipher_walk_done(&w, avail); } return err; } static int xts_xor_tweak_pre(struct skcipher_request *req, bool enc) { return xts_xor_tweak(req, false, enc); } static int xts_xor_tweak_post(struct skcipher_request *req, bool enc) { return xts_xor_tweak(req, true, enc); } static void xts_cts_done(struct crypto_async_request *areq, int err) { struct skcipher_request *req = areq->data; le128 b; if (!err) { struct xts_request_ctx *rctx = skcipher_request_ctx(req); scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 0); le128_xor(&b, &rctx->t, &b); scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 1); } skcipher_request_complete(req, err); } static int xts_cts_final(struct skcipher_request *req, int (*crypt)(struct skcipher_request *req)) { const struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req)); int offset = req->cryptlen & ~(XTS_BLOCK_SIZE - 1); struct xts_request_ctx *rctx = skcipher_request_ctx(req); struct skcipher_request *subreq = &rctx->subreq; int tail = req->cryptlen % XTS_BLOCK_SIZE; le128 b[2]; int err; rctx->tail = scatterwalk_ffwd(rctx->sg, req->dst, offset - XTS_BLOCK_SIZE); scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0); b[1] = b[0]; scatterwalk_map_and_copy(b, req->src, offset, tail, 0); le128_xor(b, &rctx->t, b); scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE + tail, 1); skcipher_request_set_tfm(subreq, ctx->child); skcipher_request_set_callback(subreq, req->base.flags, xts_cts_done, req); skcipher_request_set_crypt(subreq, rctx->tail, rctx->tail, XTS_BLOCK_SIZE, NULL); err = crypt(subreq); if (err) return err; scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0); le128_xor(b, &rctx->t, b); scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 1); return 0; } static void xts_encrypt_done(struct crypto_async_request *areq, int err) { struct skcipher_request *req = areq->data; if (!err) { struct xts_request_ctx *rctx = skcipher_request_ctx(req); rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP; err = xts_xor_tweak_post(req, true); if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) { err = xts_cts_final(req, crypto_skcipher_encrypt); if (err == -EINPROGRESS) return; } } skcipher_request_complete(req, err); } static void xts_decrypt_done(struct crypto_async_request *areq, int err) { struct skcipher_request *req = areq->data; if (!err) { struct xts_request_ctx *rctx = skcipher_request_ctx(req); rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP; err = xts_xor_tweak_post(req, false); if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) { err = xts_cts_final(req, crypto_skcipher_decrypt); if (err == -EINPROGRESS) return; } } skcipher_request_complete(req, err); } static int xts_init_crypt(struct skcipher_request *req, crypto_completion_t compl) { const struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req)); struct xts_request_ctx *rctx = skcipher_request_ctx(req); struct skcipher_request *subreq = &rctx->subreq; if (req->cryptlen < XTS_BLOCK_SIZE) return -EINVAL; skcipher_request_set_tfm(subreq, ctx->child); skcipher_request_set_callback(subreq, req->base.flags, compl, req); skcipher_request_set_crypt(subreq, req->dst, req->dst, req->cryptlen & ~(XTS_BLOCK_SIZE - 1), NULL); /* calculate first value of T */ crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv); return 0; } static int xts_encrypt(struct skcipher_request *req) { struct xts_request_ctx *rctx = skcipher_request_ctx(req); struct skcipher_request *subreq = &rctx->subreq; int err; err = xts_init_crypt(req, xts_encrypt_done) ?: xts_xor_tweak_pre(req, true) ?: crypto_skcipher_encrypt(subreq) ?: xts_xor_tweak_post(req, true); if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0)) return err; return xts_cts_final(req, crypto_skcipher_encrypt); } static int xts_decrypt(struct skcipher_request *req) { struct xts_request_ctx *rctx = skcipher_request_ctx(req); struct skcipher_request *subreq = &rctx->subreq; int err; err = xts_init_crypt(req, xts_decrypt_done) ?: xts_xor_tweak_pre(req, false) ?: crypto_skcipher_decrypt(subreq) ?: xts_xor_tweak_post(req, false); if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0)) return err; return xts_cts_final(req, crypto_skcipher_decrypt); } static int xts_init_tfm(struct crypto_skcipher *tfm) { struct skcipher_instance *inst = skcipher_alg_instance(tfm); struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst); struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm); struct crypto_skcipher *child; struct crypto_cipher *tweak; child = crypto_spawn_skcipher(&ictx->spawn); if (IS_ERR(child)) return PTR_ERR(child); ctx->child = child; tweak = crypto_alloc_cipher(ictx->name, 0, 0); if (IS_ERR(tweak)) { crypto_free_skcipher(ctx->child); return PTR_ERR(tweak); } ctx->tweak = tweak; crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) + sizeof(struct xts_request_ctx)); return 0; } static void xts_exit_tfm(struct crypto_skcipher *tfm) { struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm); crypto_free_skcipher(ctx->child); crypto_free_cipher(ctx->tweak); } static void xts_free_instance(struct skcipher_instance *inst) { struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst); crypto_drop_skcipher(&ictx->spawn); kfree(inst); } static int xts_create(struct crypto_template *tmpl, struct rtattr **tb) { struct skcipher_instance *inst; struct xts_instance_ctx *ctx; struct skcipher_alg *alg; const char *cipher_name; u32 mask; int err; err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask); if (err) return err; cipher_name = crypto_attr_alg_name(tb[1]); if (IS_ERR(cipher_name)) return PTR_ERR(cipher_name); inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL); if (!inst) return -ENOMEM; ctx = skcipher_instance_ctx(inst); err = crypto_grab_skcipher(&ctx->spawn, skcipher_crypto_instance(inst), cipher_name, 0, mask); if (err == -ENOENT) { err = -ENAMETOOLONG; if (snprintf(ctx->name, CRYPTO_MAX_ALG_NAME, "ecb(%s)", cipher_name) >= CRYPTO_MAX_ALG_NAME) goto err_free_inst; err = crypto_grab_skcipher(&ctx->spawn, skcipher_crypto_instance(inst), ctx->name, 0, mask); } if (err) goto err_free_inst; alg = crypto_skcipher_spawn_alg(&ctx->spawn); err = -EINVAL; if (alg->base.cra_blocksize != XTS_BLOCK_SIZE) goto err_free_inst; if (crypto_skcipher_alg_ivsize(alg)) goto err_free_inst; err = crypto_inst_setname(skcipher_crypto_instance(inst), "xts", &alg->base); if (err) goto err_free_inst; err = -EINVAL; cipher_name = alg->base.cra_name; /* Alas we screwed up the naming so we have to mangle the * cipher name. */ if (!strncmp(cipher_name, "ecb(", 4)) { unsigned len; len = strlcpy(ctx->name, cipher_name + 4, sizeof(ctx->name)); if (len < 2 || len >= sizeof(ctx->name)) goto err_free_inst; if (ctx->name[len - 1] != ')') goto err_free_inst; ctx->name[len - 1] = 0; if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME, "xts(%s)", ctx->name) >= CRYPTO_MAX_ALG_NAME) { err = -ENAMETOOLONG; goto err_free_inst; } } else goto err_free_inst; inst->alg.base.cra_priority = alg->base.cra_priority; inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE; inst->alg.base.cra_alignmask = alg->base.cra_alignmask | (__alignof__(u64) - 1); inst->alg.ivsize = XTS_BLOCK_SIZE; inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) * 2; inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2; inst->alg.base.cra_ctxsize = sizeof(struct xts_tfm_ctx); inst->alg.init = xts_init_tfm; inst->alg.exit = xts_exit_tfm; inst->alg.setkey = xts_setkey; inst->alg.encrypt = xts_encrypt; inst->alg.decrypt = xts_decrypt; inst->free = xts_free_instance; err = skcipher_register_instance(tmpl, inst); if (err) { err_free_inst: xts_free_instance(inst); } return err; } static struct crypto_template xts_tmpl = { .name = "xts", .create = xts_create, .module = THIS_MODULE, }; static int __init xts_module_init(void) { return crypto_register_template(&xts_tmpl); } static void __exit xts_module_exit(void) { crypto_unregister_template(&xts_tmpl); } subsys_initcall(xts_module_init); module_exit(xts_module_exit); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("XTS block cipher mode"); MODULE_ALIAS_CRYPTO("xts");