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 <sys/systm.h> 55 #include <opencrypto/xform_enc.h> 56 57 static int aes_xts_setkey(void *, const uint8_t *, int); 58 static void aes_xts_encrypt(void *, const uint8_t *, uint8_t *); 59 static void aes_xts_decrypt(void *, const uint8_t *, uint8_t *); 60 static void aes_xts_encrypt_multi(void *, const uint8_t *, uint8_t *, size_t); 61 static void aes_xts_decrypt_multi(void *, const uint8_t *, uint8_t *, size_t); 62 static void aes_xts_reinit(void *, const uint8_t *, size_t); 63 64 /* Encryption instances */ 65 const struct enc_xform enc_xform_aes_xts = { 66 .type = CRYPTO_AES_XTS, 67 .name = "AES-XTS", 68 .ctxsize = sizeof(struct aes_xts_ctx), 69 .blocksize = AES_BLOCK_LEN, 70 .ivsize = AES_XTS_IV_LEN, 71 .minkey = AES_XTS_MIN_KEY, 72 .maxkey = AES_XTS_MAX_KEY, 73 .setkey = aes_xts_setkey, 74 .reinit = aes_xts_reinit, 75 .encrypt = aes_xts_encrypt, 76 .decrypt = aes_xts_decrypt, 77 .encrypt_multi = aes_xts_encrypt_multi, 78 .decrypt_multi = aes_xts_decrypt_multi, 79 }; 80 81 /* 82 * Encryption wrapper routines. 83 */ 84 static void 85 aes_xts_reinit(void *key, const uint8_t *iv, size_t ivlen) 86 { 87 struct aes_xts_ctx *ctx = key; 88 uint64_t blocknum; 89 u_int i; 90 91 KASSERT(ivlen == sizeof(blocknum), 92 ("%s: invalid IV length", __func__)); 93 94 /* 95 * Prepare tweak as E_k2(IV). IV is specified as LE representation 96 * of a 64-bit block number which we allow to be passed in directly. 97 */ 98 bcopy(iv, &blocknum, AES_XTS_IVSIZE); 99 for (i = 0; i < AES_XTS_IVSIZE; i++) { 100 ctx->tweak[i] = blocknum & 0xff; 101 blocknum >>= 8; 102 } 103 /* Last 64 bits of IV are always zero */ 104 bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE); 105 106 rijndael_encrypt(&ctx->key2, ctx->tweak, ctx->tweak); 107 } 108 109 static void 110 aes_xts_crypt(struct aes_xts_ctx *ctx, const uint8_t *in, uint8_t *out, 111 size_t len, bool do_encrypt) 112 { 113 uint8_t block[AES_XTS_BLOCKSIZE]; 114 u_int i, carry_in, carry_out; 115 116 KASSERT(len % AES_XTS_BLOCKSIZE == 0, ("%s: invalid length", __func__)); 117 while (len > 0) { 118 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) 119 block[i] = in[i] ^ ctx->tweak[i]; 120 121 if (do_encrypt) 122 rijndael_encrypt(&ctx->key1, block, out); 123 else 124 rijndael_decrypt(&ctx->key1, block, out); 125 126 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) 127 out[i] ^= ctx->tweak[i]; 128 129 /* Exponentiate tweak */ 130 carry_in = 0; 131 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) { 132 carry_out = ctx->tweak[i] & 0x80; 133 ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0); 134 carry_in = carry_out; 135 } 136 if (carry_in) 137 ctx->tweak[0] ^= AES_XTS_ALPHA; 138 139 in += AES_XTS_BLOCKSIZE; 140 out += AES_XTS_BLOCKSIZE; 141 len -= AES_XTS_BLOCKSIZE; 142 } 143 explicit_bzero(block, sizeof(block)); 144 } 145 146 static void 147 aes_xts_encrypt(void *key, const uint8_t *in, uint8_t *out) 148 { 149 aes_xts_crypt(key, in, out, AES_XTS_BLOCKSIZE, true); 150 } 151 152 static void 153 aes_xts_decrypt(void *key, const uint8_t *in, uint8_t *out) 154 { 155 aes_xts_crypt(key, in, out, AES_XTS_BLOCKSIZE, false); 156 } 157 158 static void 159 aes_xts_encrypt_multi(void *vctx, const uint8_t *in, uint8_t *out, size_t len) 160 { 161 aes_xts_crypt(vctx, in, out, len, true); 162 } 163 164 static void 165 aes_xts_decrypt_multi(void *vctx, const uint8_t *in, uint8_t *out, size_t len) 166 { 167 aes_xts_crypt(vctx, in, out, len, false); 168 } 169 170 static int 171 aes_xts_setkey(void *sched, const uint8_t *key, int len) 172 { 173 struct aes_xts_ctx *ctx; 174 175 if (len != 32 && len != 64) 176 return (EINVAL); 177 178 ctx = sched; 179 180 rijndael_set_key(&ctx->key1, key, len * 4); 181 rijndael_set_key(&ctx->key2, key + (len / 2), len * 4); 182 183 return (0); 184 } 185