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 <sys/types.h> 54 #include <opencrypto/xform_enc.h> 55 56 static int aes_xts_setkey(void *, const uint8_t *, int); 57 static void aes_xts_encrypt(void *, const uint8_t *, uint8_t *); 58 static void aes_xts_decrypt(void *, const uint8_t *, uint8_t *); 59 static void aes_xts_reinit(void *, const uint8_t *); 60 61 /* Encryption instances */ 62 struct enc_xform enc_xform_aes_xts = { 63 .type = CRYPTO_AES_XTS, 64 .name = "AES-XTS", 65 .ctxsize = sizeof(struct aes_xts_ctx), 66 .blocksize = AES_BLOCK_LEN, 67 .ivsize = AES_XTS_IV_LEN, 68 .minkey = AES_XTS_MIN_KEY, 69 .maxkey = AES_XTS_MAX_KEY, 70 .encrypt = aes_xts_encrypt, 71 .decrypt = aes_xts_decrypt, 72 .setkey = aes_xts_setkey, 73 .reinit = aes_xts_reinit 74 }; 75 76 /* 77 * Encryption wrapper routines. 78 */ 79 static void 80 aes_xts_reinit(void *key, const uint8_t *iv) 81 { 82 struct aes_xts_ctx *ctx = key; 83 uint64_t blocknum; 84 u_int i; 85 86 /* 87 * Prepare tweak as E_k2(IV). IV is specified as LE representation 88 * of a 64-bit block number which we allow to be passed in directly. 89 */ 90 bcopy(iv, &blocknum, AES_XTS_IVSIZE); 91 for (i = 0; i < AES_XTS_IVSIZE; i++) { 92 ctx->tweak[i] = blocknum & 0xff; 93 blocknum >>= 8; 94 } 95 /* Last 64 bits of IV are always zero */ 96 bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE); 97 98 rijndael_encrypt(&ctx->key2, ctx->tweak, ctx->tweak); 99 } 100 101 static void 102 aes_xts_crypt(struct aes_xts_ctx *ctx, const uint8_t *in, uint8_t *out, 103 u_int do_encrypt) 104 { 105 uint8_t block[AES_XTS_BLOCKSIZE]; 106 u_int i, carry_in, carry_out; 107 108 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) 109 block[i] = in[i] ^ ctx->tweak[i]; 110 111 if (do_encrypt) 112 rijndael_encrypt(&ctx->key1, block, out); 113 else 114 rijndael_decrypt(&ctx->key1, block, out); 115 116 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) 117 out[i] ^= ctx->tweak[i]; 118 119 /* Exponentiate tweak */ 120 carry_in = 0; 121 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) { 122 carry_out = ctx->tweak[i] & 0x80; 123 ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0); 124 carry_in = carry_out; 125 } 126 if (carry_in) 127 ctx->tweak[0] ^= AES_XTS_ALPHA; 128 explicit_bzero(block, sizeof(block)); 129 } 130 131 static void 132 aes_xts_encrypt(void *key, const uint8_t *in, uint8_t *out) 133 { 134 aes_xts_crypt(key, in, out, 1); 135 } 136 137 static void 138 aes_xts_decrypt(void *key, const uint8_t *in, uint8_t *out) 139 { 140 aes_xts_crypt(key, in, out, 0); 141 } 142 143 static int 144 aes_xts_setkey(void *sched, const uint8_t *key, int len) 145 { 146 struct aes_xts_ctx *ctx; 147 148 if (len != 32 && len != 64) 149 return (EINVAL); 150 151 ctx = sched; 152 153 rijndael_set_key(&ctx->key1, key, len * 4); 154 rijndael_set_key(&ctx->key2, key + (len / 2), len * 4); 155 156 return (0); 157 } 158