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/types.h> 51 #include <sys/systm.h> 52 #include <opencrypto/xform_enc.h> 53 54 static int aes_xts_setkey(void *, const uint8_t *, int); 55 static void aes_xts_encrypt(void *, const uint8_t *, uint8_t *); 56 static void aes_xts_decrypt(void *, const uint8_t *, uint8_t *); 57 static void aes_xts_encrypt_multi(void *, const uint8_t *, uint8_t *, size_t); 58 static void aes_xts_decrypt_multi(void *, const uint8_t *, uint8_t *, size_t); 59 static void aes_xts_reinit(void *, const uint8_t *, size_t); 60 61 /* Encryption instances */ 62 const 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 .setkey = aes_xts_setkey, 71 .reinit = aes_xts_reinit, 72 .encrypt = aes_xts_encrypt, 73 .decrypt = aes_xts_decrypt, 74 .encrypt_multi = aes_xts_encrypt_multi, 75 .decrypt_multi = aes_xts_decrypt_multi, 76 }; 77 78 /* 79 * Encryption wrapper routines. 80 */ 81 static void 82 aes_xts_reinit(void *key, const uint8_t *iv, size_t ivlen) 83 { 84 struct aes_xts_ctx *ctx = key; 85 uint64_t blocknum; 86 u_int i; 87 88 KASSERT(ivlen == sizeof(blocknum), 89 ("%s: invalid IV length", __func__)); 90 91 /* 92 * Prepare tweak as E_k2(IV). IV is specified as LE representation 93 * of a 64-bit block number which we allow to be passed in directly. 94 */ 95 bcopy(iv, &blocknum, AES_XTS_IVSIZE); 96 for (i = 0; i < AES_XTS_IVSIZE; i++) { 97 ctx->tweak[i] = blocknum & 0xff; 98 blocknum >>= 8; 99 } 100 /* Last 64 bits of IV are always zero */ 101 bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE); 102 103 rijndael_encrypt(&ctx->key2, ctx->tweak, ctx->tweak); 104 } 105 106 static void 107 aes_xts_crypt(struct aes_xts_ctx *ctx, const uint8_t *in, uint8_t *out, 108 size_t len, bool do_encrypt) 109 { 110 uint8_t block[AES_XTS_BLOCKSIZE]; 111 u_int i, carry_in, carry_out; 112 113 KASSERT(len % AES_XTS_BLOCKSIZE == 0, ("%s: invalid length", __func__)); 114 while (len > 0) { 115 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) 116 block[i] = in[i] ^ ctx->tweak[i]; 117 118 if (do_encrypt) 119 rijndael_encrypt(&ctx->key1, block, out); 120 else 121 rijndael_decrypt(&ctx->key1, block, out); 122 123 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) 124 out[i] ^= ctx->tweak[i]; 125 126 /* Exponentiate tweak */ 127 carry_in = 0; 128 for (i = 0; i < AES_XTS_BLOCKSIZE; i++) { 129 carry_out = ctx->tweak[i] & 0x80; 130 ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0); 131 carry_in = carry_out; 132 } 133 if (carry_in) 134 ctx->tweak[0] ^= AES_XTS_ALPHA; 135 136 in += AES_XTS_BLOCKSIZE; 137 out += AES_XTS_BLOCKSIZE; 138 len -= AES_XTS_BLOCKSIZE; 139 } 140 explicit_bzero(block, sizeof(block)); 141 } 142 143 static void 144 aes_xts_encrypt(void *key, const uint8_t *in, uint8_t *out) 145 { 146 aes_xts_crypt(key, in, out, AES_XTS_BLOCKSIZE, true); 147 } 148 149 static void 150 aes_xts_decrypt(void *key, const uint8_t *in, uint8_t *out) 151 { 152 aes_xts_crypt(key, in, out, AES_XTS_BLOCKSIZE, false); 153 } 154 155 static void 156 aes_xts_encrypt_multi(void *vctx, const uint8_t *in, uint8_t *out, size_t len) 157 { 158 aes_xts_crypt(vctx, in, out, len, true); 159 } 160 161 static void 162 aes_xts_decrypt_multi(void *vctx, const uint8_t *in, uint8_t *out, size_t len) 163 { 164 aes_xts_crypt(vctx, in, out, len, false); 165 } 166 167 static int 168 aes_xts_setkey(void *sched, const uint8_t *key, int len) 169 { 170 struct aes_xts_ctx *ctx; 171 172 if (len != 32 && len != 64) 173 return (EINVAL); 174 175 ctx = sched; 176 177 rijndael_set_key(&ctx->key1, key, len * 4); 178 rijndael_set_key(&ctx->key2, key + (len / 2), len * 4); 179 180 return (0); 181 } 182