xref: /openssl/crypto/modes/xts128.c (revision e23d850f)
1 /*
2  * Copyright 2011-2020 The OpenSSL Project Authors. All Rights Reserved.
3  *
4  * Licensed under the Apache License 2.0 (the "License").  You may not use
5  * this file except in compliance with the License.  You can obtain a copy
6  * in the file LICENSE in the source distribution or at
7  * https://www.openssl.org/source/license.html
8  */
9 
10 #include <string.h>
11 #include <openssl/crypto.h>
12 #include "internal/endian.h"
13 #include "crypto/modes.h"
14 
15 #ifndef STRICT_ALIGNMENT
16 # ifdef __GNUC__
17 typedef u64 u64_a1 __attribute((__aligned__(1)));
18 # else
19 typedef u64 u64_a1;
20 # endif
21 #endif
22 
CRYPTO_xts128_encrypt(const XTS128_CONTEXT * ctx,const unsigned char iv[16],const unsigned char * inp,unsigned char * out,size_t len,int enc)23 int CRYPTO_xts128_encrypt(const XTS128_CONTEXT *ctx,
24                           const unsigned char iv[16],
25                           const unsigned char *inp, unsigned char *out,
26                           size_t len, int enc)
27 {
28     DECLARE_IS_ENDIAN;
29     union {
30         u64 u[2];
31         u32 d[4];
32         u8 c[16];
33     } tweak, scratch;
34     unsigned int i;
35 
36     if (len < 16)
37         return -1;
38 
39     memcpy(tweak.c, iv, 16);
40 
41     (*ctx->block2) (tweak.c, tweak.c, ctx->key2);
42 
43     if (!enc && (len % 16))
44         len -= 16;
45 
46     while (len >= 16) {
47 #if defined(STRICT_ALIGNMENT)
48         memcpy(scratch.c, inp, 16);
49         scratch.u[0] ^= tweak.u[0];
50         scratch.u[1] ^= tweak.u[1];
51 #else
52         scratch.u[0] = ((u64_a1 *)inp)[0] ^ tweak.u[0];
53         scratch.u[1] = ((u64_a1 *)inp)[1] ^ tweak.u[1];
54 #endif
55         (*ctx->block1) (scratch.c, scratch.c, ctx->key1);
56 #if defined(STRICT_ALIGNMENT)
57         scratch.u[0] ^= tweak.u[0];
58         scratch.u[1] ^= tweak.u[1];
59         memcpy(out, scratch.c, 16);
60 #else
61         ((u64_a1 *)out)[0] = scratch.u[0] ^= tweak.u[0];
62         ((u64_a1 *)out)[1] = scratch.u[1] ^= tweak.u[1];
63 #endif
64         inp += 16;
65         out += 16;
66         len -= 16;
67 
68         if (len == 0)
69             return 0;
70 
71         if (IS_LITTLE_ENDIAN) {
72             unsigned int carry, res;
73 
74             res = 0x87 & (((int)tweak.d[3]) >> 31);
75             carry = (unsigned int)(tweak.u[0] >> 63);
76             tweak.u[0] = (tweak.u[0] << 1) ^ res;
77             tweak.u[1] = (tweak.u[1] << 1) | carry;
78         } else {
79             size_t c;
80 
81             for (c = 0, i = 0; i < 16; ++i) {
82                 /*
83                  * + substitutes for |, because c is 1 bit
84                  */
85                 c += ((size_t)tweak.c[i]) << 1;
86                 tweak.c[i] = (u8)c;
87                 c = c >> 8;
88             }
89             tweak.c[0] ^= (u8)(0x87 & (0 - c));
90         }
91     }
92     if (enc) {
93         for (i = 0; i < len; ++i) {
94             u8 c = inp[i];
95             out[i] = scratch.c[i];
96             scratch.c[i] = c;
97         }
98         scratch.u[0] ^= tweak.u[0];
99         scratch.u[1] ^= tweak.u[1];
100         (*ctx->block1) (scratch.c, scratch.c, ctx->key1);
101         scratch.u[0] ^= tweak.u[0];
102         scratch.u[1] ^= tweak.u[1];
103         memcpy(out - 16, scratch.c, 16);
104     } else {
105         union {
106             u64 u[2];
107             u8 c[16];
108         } tweak1;
109 
110         if (IS_LITTLE_ENDIAN) {
111             unsigned int carry, res;
112 
113             res = 0x87 & (((int)tweak.d[3]) >> 31);
114             carry = (unsigned int)(tweak.u[0] >> 63);
115             tweak1.u[0] = (tweak.u[0] << 1) ^ res;
116             tweak1.u[1] = (tweak.u[1] << 1) | carry;
117         } else {
118             size_t c;
119 
120             for (c = 0, i = 0; i < 16; ++i) {
121                 /*
122                  * + substitutes for |, because c is 1 bit
123                  */
124                 c += ((size_t)tweak.c[i]) << 1;
125                 tweak1.c[i] = (u8)c;
126                 c = c >> 8;
127             }
128             tweak1.c[0] ^= (u8)(0x87 & (0 - c));
129         }
130 #if defined(STRICT_ALIGNMENT)
131         memcpy(scratch.c, inp, 16);
132         scratch.u[0] ^= tweak1.u[0];
133         scratch.u[1] ^= tweak1.u[1];
134 #else
135         scratch.u[0] = ((u64_a1 *)inp)[0] ^ tweak1.u[0];
136         scratch.u[1] = ((u64_a1 *)inp)[1] ^ tweak1.u[1];
137 #endif
138         (*ctx->block1) (scratch.c, scratch.c, ctx->key1);
139         scratch.u[0] ^= tweak1.u[0];
140         scratch.u[1] ^= tweak1.u[1];
141 
142         for (i = 0; i < len; ++i) {
143             u8 c = inp[16 + i];
144             out[16 + i] = scratch.c[i];
145             scratch.c[i] = c;
146         }
147         scratch.u[0] ^= tweak.u[0];
148         scratch.u[1] ^= tweak.u[1];
149         (*ctx->block1) (scratch.c, scratch.c, ctx->key1);
150 #if defined(STRICT_ALIGNMENT)
151         scratch.u[0] ^= tweak.u[0];
152         scratch.u[1] ^= tweak.u[1];
153         memcpy(out, scratch.c, 16);
154 #else
155         ((u64_a1 *)out)[0] = scratch.u[0] ^ tweak.u[0];
156         ((u64_a1 *)out)[1] = scratch.u[1] ^ tweak.u[1];
157 #endif
158     }
159 
160     return 0;
161 }
162