diff options
Diffstat (limited to 'crypto/xts.c')
| -rw-r--r-- | crypto/xts.c | 476 |
1 files changed, 476 insertions, 0 deletions
diff --git a/crypto/xts.c b/crypto/xts.c new file mode 100644 index 000000000..038f60dd5 --- /dev/null +++ b/crypto/xts.c @@ -0,0 +1,476 @@ +// 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/cipher.h> +#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; + struct crypto_cipher_spawn tweak_spawn; +}; + +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(void *data, int err) +{ + struct skcipher_request *req = 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(void *data, int err) +{ + struct skcipher_request *req = data; + + if (!err) { + struct xts_request_ctx *rctx = skcipher_request_ctx(req); + + rctx->subreq.base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG; + 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 || err == -EBUSY) + return; + } + } + + skcipher_request_complete(req, err); +} + +static void xts_decrypt_done(void *data, int err) +{ + struct skcipher_request *req = data; + + if (!err) { + struct xts_request_ctx *rctx = skcipher_request_ctx(req); + + rctx->subreq.base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG; + 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 || err == -EBUSY) + 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_spawn_cipher(&ictx->tweak_spawn); + 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); + crypto_drop_cipher(&ictx->tweak_spawn); + kfree(inst); +} + +static int xts_create(struct crypto_template *tmpl, struct rtattr **tb) +{ + char name[CRYPTO_MAX_ALG_NAME]; + 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(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), + 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)) { + int len; + + len = strscpy(name, cipher_name + 4, sizeof(name)); + if (len < 2) + goto err_free_inst; + + if (name[len - 1] != ')') + goto err_free_inst; + + name[len - 1] = 0; + + if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME, + "xts(%s)", name) >= CRYPTO_MAX_ALG_NAME) { + err = -ENAMETOOLONG; + goto err_free_inst; + } + } else + goto err_free_inst; + + err = crypto_grab_cipher(&ctx->tweak_spawn, + skcipher_crypto_instance(inst), name, 0, mask); + if (err) + 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"); +MODULE_IMPORT_NS(CRYPTO_INTERNAL); +MODULE_SOFTDEP("pre: ecb"); |