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 #include <sys/types.h> 52 #include <sys/systm.h> 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_encrypt_multi(void *, const uint8_t *, uint8_t *, size_t); 59 static void aes_xts_decrypt_multi(void *, const uint8_t *, uint8_t *, size_t); 60 static void aes_xts_reinit(void *, const uint8_t *, size_t); 61 62 /* Encryption instances */ 63 const struct enc_xform enc_xform_aes_xts = { 64 .type = CRYPTO_AES_XTS, 65 .name = "AES-XTS", 66 .ctxsize = sizeof(struct aes_xts_ctx), 67 .blocksize = AES_BLOCK_LEN, 68 .ivsize = AES_XTS_IV_LEN, 69 .minkey = AES_XTS_MIN_KEY, 70 .maxkey = AES_XTS_MAX_KEY, 71 .setkey = aes_xts_setkey, 72 .reinit = aes_xts_reinit, 73 .encrypt = aes_xts_encrypt, 74 .decrypt = aes_xts_decrypt, 75 .encrypt_multi = aes_xts_encrypt_multi, 76 .decrypt_multi = aes_xts_decrypt_multi, 77 }; 78 79 /* 80 * Encryption wrapper routines. 81 */ 82 static void 83 aes_xts_reinit(void *key, const uint8_t *iv, size_t ivlen) 84 { 85 struct aes_xts_ctx *ctx = key; 86 uint64_t blocknum; 87 u_int i; 88 89 KASSERT(ivlen == sizeof(blocknum), 90 ("%s: invalid IV length", __func__)); 91 92 /* 93 * Prepare tweak as E_k2(IV). IV is specified as LE representation 94 * of a 64-bit block number which we allow to be passed in directly. 95 */ 96 bcopy(iv, &blocknum, AES_XTS_IVSIZE); 97 for (i = 0; i < AES_XTS_IVSIZE; i++) { 98 ctx->tweak[i] = blocknum & 0xff; 99 blocknum >>= 8; 100 } 101 /* Last 64 bits of IV are always zero */ 102 bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE); 103 104 rijndael_encrypt(&ctx->key2, ctx->tweak, ctx->tweak); 105 } 106 107 static void 108 aes_xts_crypt(struct aes_xts_ctx *ctx, const uint8_t *in, uint8_t *out, 109 size_t len, bool do_encrypt) 110 { 111 uint8_t block[AES_XTS_BLOCKSIZE]; 112 u_int i, carry_in, carry_out; 113 114 KASSERT(len % AES_XTS_BLOCKSIZE == 0, ("%s: invalid length", __func__)); 115 while (len > 0) { 116 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) 117 block[i] = in[i] ^ ctx->tweak[i]; 118 119 if (do_encrypt) 120 rijndael_encrypt(&ctx->key1, block, out); 121 else 122 rijndael_decrypt(&ctx->key1, block, out); 123 124 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) 125 out[i] ^= ctx->tweak[i]; 126 127 /* Exponentiate tweak */ 128 carry_in = 0; 129 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) { 130 carry_out = ctx->tweak[i] & 0x80; 131 ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0); 132 carry_in = carry_out; 133 } 134 if (carry_in) 135 ctx->tweak[0] ^= AES_XTS_ALPHA; 136 137 in += AES_XTS_BLOCKSIZE; 138 out += AES_XTS_BLOCKSIZE; 139 len -= AES_XTS_BLOCKSIZE; 140 } 141 explicit_bzero(block, sizeof(block)); 142 } 143 144 static void 145 aes_xts_encrypt(void *key, const uint8_t *in, uint8_t *out) 146 { 147 aes_xts_crypt(key, in, out, AES_XTS_BLOCKSIZE, true); 148 } 149 150 static void 151 aes_xts_decrypt(void *key, const uint8_t *in, uint8_t *out) 152 { 153 aes_xts_crypt(key, in, out, AES_XTS_BLOCKSIZE, false); 154 } 155 156 static void 157 aes_xts_encrypt_multi(void *vctx, const uint8_t *in, uint8_t *out, size_t len) 158 { 159 aes_xts_crypt(vctx, in, out, len, true); 160 } 161 162 static void 163 aes_xts_decrypt_multi(void *vctx, const uint8_t *in, uint8_t *out, size_t len) 164 { 165 aes_xts_crypt(vctx, in, out, len, false); 166 } 167 168 static int 169 aes_xts_setkey(void *sched, const uint8_t *key, int len) 170 { 171 struct aes_xts_ctx *ctx; 172 173 if (len != 32 && len != 64) 174 return (EINVAL); 175 176 ctx = sched; 177 178 rijndael_set_key(&ctx->key1, key, len * 4); 179 rijndael_set_key(&ctx->key2, key + (len / 2), len * 4); 180 181 return (0); 182 } 183