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(void *, const uint8_t *, int); 56 static void aes_xts_encrypt(void *, const uint8_t *, uint8_t *); 57 static void aes_xts_decrypt(void *, const uint8_t *, uint8_t *); 58 static void aes_xts_reinit(void *, const uint8_t *); 59 60 /* Encryption instances */ 61 struct enc_xform enc_xform_aes_xts = { 62 .type = CRYPTO_AES_XTS, 63 .name = "AES-XTS", 64 .ctxsize = sizeof(struct aes_xts_ctx), 65 .blocksize = AES_BLOCK_LEN, 66 .ivsize = AES_XTS_IV_LEN, 67 .minkey = AES_XTS_MIN_KEY, 68 .maxkey = AES_XTS_MAX_KEY, 69 .encrypt = aes_xts_encrypt, 70 .decrypt = aes_xts_decrypt, 71 .setkey = aes_xts_setkey, 72 .reinit = aes_xts_reinit 73 }; 74 75 /* 76 * Encryption wrapper routines. 77 */ 78 static void 79 aes_xts_reinit(void *key, const uint8_t *iv) 80 { 81 struct aes_xts_ctx *ctx = key; 82 uint64_t blocknum; 83 u_int i; 84 85 /* 86 * Prepare tweak as E_k2(IV). IV is specified as LE representation 87 * of a 64-bit block number which we allow to be passed in directly. 88 */ 89 bcopy(iv, &blocknum, AES_XTS_IVSIZE); 90 for (i = 0; i < AES_XTS_IVSIZE; i++) { 91 ctx->tweak[i] = blocknum & 0xff; 92 blocknum >>= 8; 93 } 94 /* Last 64 bits of IV are always zero */ 95 bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE); 96 97 rijndael_encrypt(&ctx->key2, ctx->tweak, ctx->tweak); 98 } 99 100 static void 101 aes_xts_crypt(struct aes_xts_ctx *ctx, const uint8_t *in, uint8_t *out, 102 u_int do_encrypt) 103 { 104 uint8_t block[AES_XTS_BLOCKSIZE]; 105 u_int i, carry_in, carry_out; 106 107 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) 108 block[i] = in[i] ^ ctx->tweak[i]; 109 110 if (do_encrypt) 111 rijndael_encrypt(&ctx->key1, block, out); 112 else 113 rijndael_decrypt(&ctx->key1, block, out); 114 115 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) 116 out[i] ^= ctx->tweak[i]; 117 118 /* Exponentiate tweak */ 119 carry_in = 0; 120 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) { 121 carry_out = ctx->tweak[i] & 0x80; 122 ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0); 123 carry_in = carry_out; 124 } 125 if (carry_in) 126 ctx->tweak[0] ^= AES_XTS_ALPHA; 127 explicit_bzero(block, sizeof(block)); 128 } 129 130 static void 131 aes_xts_encrypt(void *key, const uint8_t *in, uint8_t *out) 132 { 133 aes_xts_crypt(key, in, out, 1); 134 } 135 136 static void 137 aes_xts_decrypt(void *key, const uint8_t *in, uint8_t *out) 138 { 139 aes_xts_crypt(key, in, out, 0); 140 } 141 142 static int 143 aes_xts_setkey(void *sched, const uint8_t *key, int len) 144 { 145 struct aes_xts_ctx *ctx; 146 147 if (len != 32 && len != 64) 148 return (EINVAL); 149 150 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