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1 | /* -*-c-*- |
2 | * | |
3 | * Key size management | |
4 | * | |
5 | * (c) 2007 Straylight/Edgeware | |
6 | */ | |
7 | ||
8 | /*----- Licensing notice --------------------------------------------------* | |
9 | * | |
10 | * This file is part of Catacomb. | |
11 | * | |
12 | * Catacomb is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU Library General Public License as | |
14 | * published by the Free Software Foundation; either version 2 of the | |
15 | * License, or (at your option) any later version. | |
16 | * | |
17 | * Catacomb is distributed in the hope that it will be useful, | |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | * GNU Library General Public License for more details. | |
21 | * | |
22 | * You should have received a copy of the GNU Library General Public | |
23 | * License along with Catacomb; if not, write to the Free | |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
25 | * MA 02111-1307, USA. | |
26 | */ | |
27 | ||
28 | #ifndef CATACOMB_KEYSZ_H | |
29 | #define CATACOMB_KEYSZ_H | |
30 | ||
31 | #ifdef __cplusplus | |
32 | extern "C" { | |
33 | #endif | |
34 | ||
35 | /*----- Header files ------------------------------------------------------*/ | |
36 | ||
37 | #include <stddef.h> | |
38 | ||
39 | #include <mLib/bits.h> | |
40 | ||
41 | /*----- Data structures ---------------------------------------------------*/ | |
42 | ||
43 | /* --- Key size type constants --- * | |
44 | * | |
45 | * A key size limitation is an array of bytes. The first byte describes the | |
46 | * kind of limitation on the key size %$k$%; the rest are argument bytes | |
47 | * %$a_i$%, for %$i \ge 0$%. In all cases, %$a_0$% is the `recommended' key | |
48 | * size. | |
49 | * | |
50 | * * @KSZ_ANY@ means there is no restriction. | |
51 | * | |
52 | * * @KSZ_RANGE@ requires that %$k \ge a_1$%, %$k \equiv 0 \pmod{a_3}$%, | |
53 | * and, if %$a_2 \ne 0$%, %$k \le a_2$%. | |
54 | * | |
55 | * * @KSZ_SET@ requires that %$k \in {\,a_i\,}$%. | |
56 | */ | |
57 | ||
58 | enum { | |
59 | KSZ_ANY, /* Allows any key at all */ | |
60 | KSZ_RANGE, /* Allows keys within a range */ | |
61 | KSZ_SET /* Allows specific sizes of keys */ | |
62 | }; | |
63 | ||
64 | /*----- Key sizes for symmetric algorithms --------------------------------*/ | |
65 | ||
66 | /* --- @keysz@ --- * | |
67 | * | |
68 | * Arguments: @size_t sz@ = a proposed key size, or zero | |
69 | * @const octet *ksz@ = pointer to key size table | |
70 | * | |
71 | * Returns: See below. | |
72 | * | |
73 | * Use: Returns a sensible key size. If @sz@ is nonzero, it is | |
74 | * interpreted as an amount (in bytes) of key material which the | |
75 | * caller has available, and the return value is either the | |
76 | * largest allowable key size less than or equal to the caller's | |
77 | * size, or zero if there is no valid key length small enough. | |
78 | * If @sz@ is zero, the function returns a `recommended' key | |
79 | * size. | |
80 | */ | |
81 | ||
82 | extern size_t keysz(size_t /*sz*/, const octet */*ksz*/); | |
83 | ||
84 | #define KSZ_CHECK(pre, sz) (keysz((sz), pre##_keysz) == (sz)) | |
85 | #define KSZ_ASSERT(pre, sz) \ | |
86 | assert(((void)"Bad key size for " #pre, KSZ_CHECK(pre, sz))) | |
87 | ||
88 | /*----- That's all, folks -------------------------------------------------*/ | |
89 | ||
90 | #ifdef __cplusplus | |
91 | } | |
92 | #endif | |
93 | ||
94 | #endif |