1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
2 *
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
5 *
6 * The library is free for all purposes without any express
7 * guarantee it works.
8 *
9 * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
10 */
11 #include "tomcrypt.h"
12
13 /**
14 @file der_length_object_identifier.c
15 ASN.1 DER, get length of Object Identifier, Tom St Denis
16 */
17
18 #ifdef LTC_DER
19
der_object_identifier_bits(unsigned long x)20 unsigned long der_object_identifier_bits(unsigned long x)
21 {
22 unsigned long c;
23 x &= 0xFFFFFFFF;
24 c = 0;
25 while (x) {
26 ++c;
27 x >>= 1;
28 }
29 return c;
30 }
31
32
33 /**
34 Gets length of DER encoding of Object Identifier
35 @param nwords The number of OID words
36 @param words The actual OID words to get the size of
37 @param outlen [out] The length of the DER encoding for the given string
38 @return CRYPT_OK if successful
39 */
der_length_object_identifier(unsigned long * words,unsigned long nwords,unsigned long * outlen)40 int der_length_object_identifier(unsigned long *words, unsigned long nwords, unsigned long *outlen)
41 {
42 unsigned long y, z, t, wordbuf;
43
44 LTC_ARGCHK(words != NULL);
45 LTC_ARGCHK(outlen != NULL);
46
47
48 /* must be >= 2 words */
49 if (nwords < 2) {
50 return CRYPT_INVALID_ARG;
51 }
52
53 /* word1 = 0,1,2,3 and word2 0..39 */
54 if (words[0] > 3 || (words[0] < 2 && words[1] > 39)) {
55 return CRYPT_INVALID_ARG;
56 }
57
58 /* leading word is the first two */
59 z = 0;
60 wordbuf = words[0] * 40 + words[1];
61 for (y = 1; y < nwords; y++) {
62 t = der_object_identifier_bits(wordbuf);
63 z += t/7 + ((t%7) ? 1 : 0) + (wordbuf == 0 ? 1 : 0);
64 if (y < nwords - 1) {
65 /* grab next word */
66 wordbuf = words[y+1];
67 }
68 }
69
70 /* now depending on the length our length encoding changes */
71 if (z < 128) {
72 z += 2;
73 } else if (z < 256) {
74 z += 3;
75 } else if (z < 65536UL) {
76 z += 4;
77 } else {
78 return CRYPT_INVALID_ARG;
79 }
80
81 *outlen = z;
82 return CRYPT_OK;
83 }
84
85 #endif
86
87 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/object_identifier/der_length_object_identifier.c,v $ */
88 /* $Revision: 1.4 $ */
89 /* $Date: 2006/04/16 20:17:42 $ */
90