1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
|
/* crypto/constant_time_locl.h */
/*-
* Utilities for constant-time cryptography.
*
* Author: Emilia Kasper (emilia@openssl.org)
* Based on previous work by Bodo Moeller, Emilia Kasper, Adam Langley
* (Google).
* ====================================================================
* Copyright (c) 2014 The OpenSSL Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* "This product includes cryptographic software written by
* Eric Young (eay@cryptsoft.com)"
* The word 'cryptographic' can be left out if the rouines from the library
* being used are not cryptographic related :-).
* 4. If you include any Windows specific code (or a derivative thereof) from
* the apps directory (application code) you must include an acknowledgement:
* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
*
* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* The licence and distribution terms for any publically available version or
* derivative of this code cannot be changed. i.e. this code cannot simply be
* copied and put under another distribution licence
* [including the GNU Public Licence.]
*/
#ifndef HEADER_CONSTANT_TIME_LOCL_H
# define HEADER_CONSTANT_TIME_LOCL_H
# include "e_os.h" /* For 'inline' */
#ifdef __cplusplus
extern "C" {
#endif
/*-
* The boolean methods return a bitmask of all ones (0xff...f) for true
* and 0 for false. This is useful for choosing a value based on the result
* of a conditional in constant time. For example,
*
* if (a < b) {
* c = a;
* } else {
* c = b;
* }
*
* can be written as
*
* unsigned int lt = constant_time_lt(a, b);
* c = constant_time_select(lt, a, b);
*/
/*
* Returns the given value with the MSB copied to all the other
* bits. Uses the fact that arithmetic shift shifts-in the sign bit.
* However, this is not ensured by the C standard so you may need to
* replace this with something else on odd CPUs.
*/
static inline unsigned int constant_time_msb(unsigned int a);
/*
* Returns 0xff..f if a < b and 0 otherwise.
*/
static inline unsigned int constant_time_lt(unsigned int a, unsigned int b);
/* Convenience method for getting an 8-bit mask. */
static inline unsigned char constant_time_lt_8(unsigned int a,
unsigned int b);
/*
* Returns 0xff..f if a >= b and 0 otherwise.
*/
static inline unsigned int constant_time_ge(unsigned int a, unsigned int b);
/* Convenience method for getting an 8-bit mask. */
static inline unsigned char constant_time_ge_8(unsigned int a,
unsigned int b);
/*
* Returns 0xff..f if a == 0 and 0 otherwise.
*/
static inline unsigned int constant_time_is_zero(unsigned int a);
/* Convenience method for getting an 8-bit mask. */
static inline unsigned char constant_time_is_zero_8(unsigned int a);
/*
* Returns 0xff..f if a == b and 0 otherwise.
*/
static inline unsigned int constant_time_eq(unsigned int a, unsigned int b);
/* Convenience method for getting an 8-bit mask. */
static inline unsigned char constant_time_eq_8(unsigned int a,
unsigned int b);
/* Signed integers. */
static inline unsigned int constant_time_eq_int(int a, int b);
/* Convenience method for getting an 8-bit mask. */
static inline unsigned char constant_time_eq_int_8(int a, int b);
/*-
* Returns (mask & a) | (~mask & b).
*
* When |mask| is all 1s or all 0s (as returned by the methods above),
* the select methods return either |a| (if |mask| is nonzero) or |b|
* (if |mask| is zero).
*/
static inline unsigned int constant_time_select(unsigned int mask,
unsigned int a,
unsigned int b);
/* Convenience method for unsigned chars. */
static inline unsigned char constant_time_select_8(unsigned char mask,
unsigned char a,
unsigned char b);
/* Convenience method for signed integers. */
static inline int constant_time_select_int(unsigned int mask, int a, int b);
static inline unsigned int constant_time_msb(unsigned int a)
{
return 0 - (a >> (sizeof(a) * 8 - 1));
}
static inline unsigned int constant_time_lt(unsigned int a, unsigned int b)
{
return constant_time_msb(a ^ ((a ^ b) | ((a - b) ^ b)));
}
static inline unsigned char constant_time_lt_8(unsigned int a, unsigned int b)
{
return (unsigned char)(constant_time_lt(a, b));
}
static inline unsigned int constant_time_ge(unsigned int a, unsigned int b)
{
return ~constant_time_lt(a, b);
}
static inline unsigned char constant_time_ge_8(unsigned int a, unsigned int b)
{
return (unsigned char)(constant_time_ge(a, b));
}
static inline unsigned int constant_time_is_zero(unsigned int a)
{
return constant_time_msb(~a & (a - 1));
}
static inline unsigned char constant_time_is_zero_8(unsigned int a)
{
return (unsigned char)(constant_time_is_zero(a));
}
static inline unsigned int constant_time_eq(unsigned int a, unsigned int b)
{
return constant_time_is_zero(a ^ b);
}
static inline unsigned char constant_time_eq_8(unsigned int a, unsigned int b)
{
return (unsigned char)(constant_time_eq(a, b));
}
static inline unsigned int constant_time_eq_int(int a, int b)
{
return constant_time_eq((unsigned)(a), (unsigned)(b));
}
static inline unsigned char constant_time_eq_int_8(int a, int b)
{
return constant_time_eq_8((unsigned)(a), (unsigned)(b));
}
static inline unsigned int constant_time_select(unsigned int mask,
unsigned int a,
unsigned int b)
{
return (mask & a) | (~mask & b);
}
static inline unsigned char constant_time_select_8(unsigned char mask,
unsigned char a,
unsigned char b)
{
return (unsigned char)(constant_time_select(mask, a, b));
}
static inline int constant_time_select_int(unsigned int mask, int a, int b)
{
return (int)(constant_time_select(mask, (unsigned)(a), (unsigned)(b)));
}
#ifdef __cplusplus
}
#endif
#endif /* HEADER_CONSTANT_TIME_LOCL_H */
|
