/* XTS: as defined in IEEE1619/D16 * http://grouper.ieee.org/groups/1619/email/pdf00086.pdf * (sector sizes which are not a multiple of 16 bytes are, * however currently unsupported) * * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org> * * Based om ecb.c * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au> * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by the Free * Software Foundation; either version 2 of the License, or (at your option) * any later version. */ #include <crypto/algapi.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/b128ops.h> #include <crypto/gf128mul.h> struct priv { struct crypto_cipher *child; struct crypto_cipher *tweak; }; static int setkey(struct crypto_tfm *parent, const u8 *key, unsigned int keylen) { struct priv *ctx = crypto_tfm_ctx(parent); struct crypto_cipher *child = ctx->tweak; u32 *flags = &parent->crt_flags; int err; /* key consists of keys of equal size concatenated, therefore * the length must be even */ if (keylen % 2) { /* tell the user why there was an error */ *flags |= CRYPTO_TFM_RES_BAD_KEY_LEN; return -EINVAL; } /* we need two cipher instances: one to compute the inital '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 */ 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/2, keylen/2); if (err) return err; crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) & CRYPTO_TFM_RES_MASK); child = ctx->child; /* data cipher, uses Key1 i.e. the first half of *key */ 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/2); if (err) return err; crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) & CRYPTO_TFM_RES_MASK); return 0; } struct sinfo { be128 *t; struct crypto_tfm *tfm; void (*fn)(struct crypto_tfm *, u8 *, const u8 *); }; static inline void xts_round(struct sinfo *s, void *dst, const void *src) { be128_xor(dst, s->t, src); /* PP <- T xor P */ s->fn(s->tfm, dst, dst); /* CC <- E(Key1,PP) */ be128_xor(dst, dst, s->t); /* C <- T xor CC */ } static int crypt(struct blkcipher_desc *d, struct blkcipher_walk *w, struct priv *ctx, void (*tw)(struct crypto_tfm *, u8 *, const u8 *), void (*fn)(struct crypto_tfm *, u8 *, const u8 *)) { int err; unsigned int avail; const int bs = crypto_cipher_blocksize(ctx->child); struct sinfo s = { .tfm = crypto_cipher_tfm(ctx->child), .fn = fn }; u8 *wsrc; u8 *wdst; err = blkcipher_walk_virt(d, w); if (!w->nbytes) return err; s.t = (be128 *)w->iv; avail = w->nbytes; wsrc = w->src.virt.addr; wdst = w->dst.virt.addr; /* calculate first value of T */ tw(crypto_cipher_tfm(ctx->tweak), w->iv, w->iv); goto first; for (;;) { do { gf128mul_x_ble(s.t, s.t); first: xts_round(&s, wdst, wsrc); wsrc += bs; wdst += bs; } while ((avail -= bs) >= bs); err = blkcipher_walk_done(d, w, avail); if (!w->nbytes) break; avail = w->nbytes; wsrc = w->src.virt.addr; wdst = w->dst.virt.addr; } return err; } static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst, struct scatterlist *src, unsigned int nbytes) { struct priv *ctx = crypto_blkcipher_ctx(desc->tfm); struct blkcipher_walk w; blkcipher_walk_init(&w, dst, src, nbytes); return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt, crypto_cipher_alg(ctx->child)->cia_encrypt); } static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst, struct scatterlist *src, unsigned int nbytes) { struct priv *ctx = crypto_blkcipher_ctx(desc->tfm); struct blkcipher_walk w; blkcipher_walk_init(&w, dst, src, nbytes); return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt, crypto_cipher_alg(ctx->child)->cia_decrypt); } static int init_tfm(struct crypto_tfm *tfm) { struct crypto_cipher *cipher; struct crypto_instance *inst = (void *)tfm->__crt_alg; struct crypto_spawn *spawn = crypto_instance_ctx(inst); struct priv *ctx = crypto_tfm_ctx(tfm); u32 *flags = &tfm->crt_flags; cipher = crypto_spawn_cipher(spawn); if (IS_ERR(cipher)) return PTR_ERR(cipher); if (crypto_cipher_blocksize(cipher) != 16) { *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN; crypto_free_cipher(cipher); return -EINVAL; } ctx->child = cipher; cipher = crypto_spawn_cipher(spawn); if (IS_ERR(cipher)) { crypto_free_cipher(ctx->child); return PTR_ERR(cipher); } /* this check isn't really needed, leave it here just in case */ if (crypto_cipher_blocksize(cipher) != 16) { crypto_free_cipher(cipher); crypto_free_cipher(ctx->child); *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN; return -EINVAL; } ctx->tweak = cipher; return 0; } static void exit_tfm(struct crypto_tfm *tfm) { struct priv *ctx = crypto_tfm_ctx(tfm); crypto_free_cipher(ctx->child); crypto_free_cipher(ctx->tweak); } static struct crypto_instance *alloc(struct rtattr **tb) { struct crypto_instance *inst; struct crypto_alg *alg; 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_PTR(PTR_ERR(alg)); inst = crypto_alloc_instance("xts", alg); if (IS_ERR(inst)) goto out_put_alg; inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER; inst->alg.cra_priority = alg->cra_priority; inst->alg.cra_blocksize = alg->cra_blocksize; if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7; else inst->alg.cra_alignmask = alg->cra_alignmask; inst->alg.cra_type = &crypto_blkcipher_type; inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize; inst->alg.cra_blkcipher.min_keysize = 2 * alg->cra_cipher.cia_min_keysize; inst->alg.cra_blkcipher.max_keysize = 2 * alg->cra_cipher.cia_max_keysize; inst->alg.cra_ctxsize = sizeof(struct priv); inst->alg.cra_init = init_tfm; inst->alg.cra_exit = exit_tfm; inst->alg.cra_blkcipher.setkey = setkey; inst->alg.cra_blkcipher.encrypt = encrypt; inst->alg.cra_blkcipher.decrypt = decrypt; out_put_alg: crypto_mod_put(alg); return inst; } static void free(struct crypto_instance *inst) { crypto_drop_spawn(crypto_instance_ctx(inst)); kfree(inst); } static struct crypto_template crypto_tmpl = { .name = "xts", .alloc = alloc, .free = free, .module = THIS_MODULE, }; static int __init crypto_module_init(void) { return crypto_register_template(&crypto_tmpl); } static void __exit crypto_module_exit(void) { crypto_unregister_template(&crypto_tmpl); } module_init(crypto_module_init); module_exit(crypto_module_exit); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("XTS block cipher mode");