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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: keysz.c,v 1.2 2004/04/08 01:36:15 mdw Exp $ |
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4 | * |
5 | * General block cipher utilities |
6 | * |
7 | * (c) 2000 Straylight/Edgeware |
8 | */ |
9 | |
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10 | /*----- Licensing notice --------------------------------------------------* |
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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. |
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18 | * |
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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. |
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23 | * |
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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 | |
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30 | /*----- Header files ------------------------------------------------------*/ |
31 | |
32 | #include <assert.h> |
33 | |
34 | #include "gcipher.h" |
35 | |
36 | /*----- Main code ---------------------------------------------------------*/ |
37 | |
38 | /* --- @keysz@ --- * |
39 | * |
40 | * Arguments: @size_t sz@ = a proposed key size, or zero |
41 | * @const octet *ksz@ = pointer to key size table |
42 | * |
43 | * Returns: See below. |
44 | * |
45 | * Use: Returns a sensible key size. If @sz@ is nonzero, it is |
46 | * interpreted as an amount (in bytes) of key material which the |
47 | * caller has available, and the return value is either the |
48 | * largest allowable key size less than or equal to the caller's |
49 | * size, or zero if there is no valid key length small enough. |
50 | * If @sz@ is zero, the function returns a `recommended' key |
51 | * size. |
52 | */ |
53 | |
54 | size_t keysz(size_t sz, const octet *ksz) |
55 | { |
56 | if (sz == 0) |
57 | return (ksz[1]); |
58 | else switch (ksz[0]) { |
59 | case KSZ_ANY: |
60 | return (sz); |
61 | case KSZ_RANGE: |
62 | if (ksz[4]) |
63 | sz -= sz % ksz[4]; |
64 | if (sz < ksz[2]) |
65 | return (0); |
66 | if (ksz[3] && sz > ksz[3]) |
67 | return (ksz[3]); |
68 | return (sz); |
69 | case KSZ_SET: { |
70 | unsigned q = 0; |
71 | for (ksz++; *ksz; ksz++) { |
72 | if (sz >= *ksz && q < *ksz) |
73 | q = *ksz; |
74 | } |
75 | return (q); |
76 | } |
77 | } |
78 | |
79 | assert(((void)"bad key size table", 0)); |
80 | return (0); |
81 | } |
82 | |
83 | /*----- That's all, folks -------------------------------------------------*/ |