7809fc3d |
1 | /* -*-c-*- |
2 | * |
3 | * $Id: keysz.c,v 1.1 2000/06/17 11:27:52 mdw Exp $ |
4 | * |
5 | * General block cipher utilities |
6 | * |
7 | * (c) 2000 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
14 | * Catacomb is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: keysz.c,v $ |
33 | * Revision 1.1 2000/06/17 11:27:52 mdw |
34 | * Key size table interpretation. |
35 | * |
36 | */ |
37 | |
38 | /*----- Header files ------------------------------------------------------*/ |
39 | |
40 | #include <assert.h> |
41 | |
42 | #include "gcipher.h" |
43 | |
44 | /*----- Main code ---------------------------------------------------------*/ |
45 | |
46 | /* --- @keysz@ --- * |
47 | * |
48 | * Arguments: @size_t sz@ = a proposed key size, or zero |
49 | * @const octet *ksz@ = pointer to key size table |
50 | * |
51 | * Returns: See below. |
52 | * |
53 | * Use: Returns a sensible key size. If @sz@ is nonzero, it is |
54 | * interpreted as an amount (in bytes) of key material which the |
55 | * caller has available, and the return value is either the |
56 | * largest allowable key size less than or equal to the caller's |
57 | * size, or zero if there is no valid key length small enough. |
58 | * If @sz@ is zero, the function returns a `recommended' key |
59 | * size. |
60 | */ |
61 | |
62 | size_t keysz(size_t sz, const octet *ksz) |
63 | { |
64 | if (sz == 0) |
65 | return (ksz[1]); |
66 | else switch (ksz[0]) { |
67 | case KSZ_ANY: |
68 | return (sz); |
69 | case KSZ_RANGE: |
70 | if (ksz[4]) |
71 | sz -= sz % ksz[4]; |
72 | if (sz < ksz[2]) |
73 | return (0); |
74 | if (ksz[3] && sz > ksz[3]) |
75 | return (ksz[3]); |
76 | return (sz); |
77 | case KSZ_SET: { |
78 | unsigned q = 0; |
79 | for (ksz++; *ksz; ksz++) { |
80 | if (sz >= *ksz && q < *ksz) |
81 | q = *ksz; |
82 | } |
83 | return (q); |
84 | } |
85 | } |
86 | |
87 | assert(((void)"bad key size table", 0)); |
88 | return (0); |
89 | } |
90 | |
91 | /*----- That's all, folks -------------------------------------------------*/ |