1 /* $OpenBSD: xform.c,v 1.16 2001/08/28 12:20:43 ben Exp $ */ 2 /*- 3 * The authors of this code are John Ioannidis (ji@tla.org), 4 * Angelos D. Keromytis (kermit@csd.uch.gr), 5 * Niels Provos (provos@physnet.uni-hamburg.de) and 6 * Damien Miller (djm@mindrot.org). 7 * 8 * This code was written by John Ioannidis for BSD/OS in Athens, Greece, 9 * in November 1995. 10 * 11 * Ported to OpenBSD and NetBSD, with additional transforms, in December 1996, 12 * by Angelos D. Keromytis. 13 * 14 * Additional transforms and features in 1997 and 1998 by Angelos D. Keromytis 15 * and Niels Provos. 16 * 17 * Additional features in 1999 by Angelos D. Keromytis. 18 * 19 * AES XTS implementation in 2008 by Damien Miller 20 * 21 * Copyright (C) 1995, 1996, 1997, 1998, 1999 by John Ioannidis, 22 * Angelos D. Keromytis and Niels Provos. 23 * 24 * Copyright (C) 2001, Angelos D. Keromytis. 25 * 26 * Copyright (C) 2008, Damien Miller 27 * Copyright (c) 2014 The FreeBSD Foundation 28 * All rights reserved. 29 * 30 * Portions of this software were developed by John-Mark Gurney 31 * under sponsorship of the FreeBSD Foundation and 32 * Rubicon Communications, LLC (Netgate). 33 * 34 * Permission to use, copy, and modify this software with or without fee 35 * is hereby granted, provided that this entire notice is included in 36 * all copies of any software which is or includes a copy or 37 * modification of this software. 38 * You may use this code under the GNU public license if you so wish. Please 39 * contribute changes back to the authors under this freer than GPL license 40 * so that we may further the use of strong encryption without limitations to 41 * all. 42 * 43 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR 44 * IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY 45 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE 46 * MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR 47 * PURPOSE. 48 */ 49 50 #include <sys/cdefs.h> 51 __FBSDID("$FreeBSD$"); 52 53 #include <opencrypto/xform_enc.h> 54 55 static int aes_xts_setkey(u_int8_t **, u_int8_t *, int); 56 static void aes_xts_encrypt(caddr_t, u_int8_t *); 57 static void aes_xts_decrypt(caddr_t, u_int8_t *); 58 static void aes_xts_zerokey(u_int8_t **); 59 static void aes_xts_reinit(caddr_t, u_int8_t *); 60 61 /* Encryption instances */ 62 struct enc_xform enc_xform_aes_xts = { 63 CRYPTO_AES_XTS, "AES-XTS", 64 AES_BLOCK_LEN, AES_XTS_IV_LEN, AES_XTS_MIN_KEY, AES_XTS_MAX_KEY, 65 aes_xts_encrypt, 66 aes_xts_decrypt, 67 aes_xts_setkey, 68 aes_xts_zerokey, 69 aes_xts_reinit 70 }; 71 72 /* 73 * Encryption wrapper routines. 74 */ 75 static void 76 aes_xts_reinit(caddr_t key, u_int8_t *iv) 77 { 78 struct aes_xts_ctx *ctx = (struct aes_xts_ctx *)key; 79 u_int64_t blocknum; 80 u_int i; 81 82 /* 83 * Prepare tweak as E_k2(IV). IV is specified as LE representation 84 * of a 64-bit block number which we allow to be passed in directly. 85 */ 86 bcopy(iv, &blocknum, AES_XTS_IVSIZE); 87 for (i = 0; i < AES_XTS_IVSIZE; i++) { 88 ctx->tweak[i] = blocknum & 0xff; 89 blocknum >>= 8; 90 } 91 /* Last 64 bits of IV are always zero */ 92 bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE); 93 94 rijndael_encrypt(&ctx->key2, ctx->tweak, ctx->tweak); 95 } 96 97 static void 98 aes_xts_crypt(struct aes_xts_ctx *ctx, u_int8_t *data, u_int do_encrypt) 99 { 100 u_int8_t block[AES_XTS_BLOCKSIZE]; 101 u_int i, carry_in, carry_out; 102 103 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) 104 block[i] = data[i] ^ ctx->tweak[i]; 105 106 if (do_encrypt) 107 rijndael_encrypt(&ctx->key1, block, data); 108 else 109 rijndael_decrypt(&ctx->key1, block, data); 110 111 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) 112 data[i] ^= ctx->tweak[i]; 113 114 /* Exponentiate tweak */ 115 carry_in = 0; 116 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) { 117 carry_out = ctx->tweak[i] & 0x80; 118 ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0); 119 carry_in = carry_out; 120 } 121 if (carry_in) 122 ctx->tweak[0] ^= AES_XTS_ALPHA; 123 bzero(block, sizeof(block)); 124 } 125 126 static void 127 aes_xts_encrypt(caddr_t key, u_int8_t *data) 128 { 129 aes_xts_crypt((struct aes_xts_ctx *)key, data, 1); 130 } 131 132 static void 133 aes_xts_decrypt(caddr_t key, u_int8_t *data) 134 { 135 aes_xts_crypt((struct aes_xts_ctx *)key, data, 0); 136 } 137 138 static int 139 aes_xts_setkey(u_int8_t **sched, u_int8_t *key, int len) 140 { 141 struct aes_xts_ctx *ctx; 142 143 if (len != 32 && len != 64) 144 return EINVAL; 145 146 *sched = KMALLOC(sizeof(struct aes_xts_ctx), M_CRYPTO_DATA, 147 M_NOWAIT | M_ZERO); 148 if (*sched == NULL) 149 return ENOMEM; 150 ctx = (struct aes_xts_ctx *)*sched; 151 152 rijndael_set_key(&ctx->key1, key, len * 4); 153 rijndael_set_key(&ctx->key2, key + (len / 2), len * 4); 154 155 return 0; 156 } 157 158 static void 159 aes_xts_zerokey(u_int8_t **sched) 160 { 161 bzero(*sched, sizeof(struct aes_xts_ctx)); 162 KFREE(*sched, M_CRYPTO_DATA); 163 *sched = NULL; 164 } 165