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
|
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
*
* LibTomCrypt is a library that provides various cryptographic
* algorithms in a highly modular and flexible manner.
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
*/
#include "tomcrypt.h"
/**
@file der_length_object_identifier.c
ASN.1 DER, get length of Object Identifier, Tom St Denis
*/
#ifdef LTC_DER
unsigned long der_object_identifier_bits(unsigned long x)
{
unsigned long c;
x &= 0xFFFFFFFF;
c = 0;
while (x) {
++c;
x >>= 1;
}
return c;
}
/**
Gets length of DER encoding of Object Identifier
@param nwords The number of OID words
@param words The actual OID words to get the size of
@param outlen [out] The length of the DER encoding for the given string
@return CRYPT_OK if successful
*/
int der_length_object_identifier(unsigned long *words, unsigned long nwords, unsigned long *outlen)
{
unsigned long y, z, t, wordbuf;
LTC_ARGCHK(words != NULL);
LTC_ARGCHK(outlen != NULL);
/* must be >= 2 words */
if (nwords < 2) {
return CRYPT_INVALID_ARG;
}
/* word1 = 0,1,2,3 and word2 0..39 */
if (words[0] > 3 || (words[0] < 2 && words[1] > 39)) {
return CRYPT_INVALID_ARG;
}
/* leading word is the first two */
z = 0;
wordbuf = words[0] * 40 + words[1];
for (y = 1; y < nwords; y++) {
t = der_object_identifier_bits(wordbuf);
z += t/7 + ((t%7) ? 1 : 0) + (wordbuf == 0 ? 1 : 0);
if (y < nwords - 1) {
/* grab next word */
wordbuf = words[y+1];
}
}
/* now depending on the length our length encoding changes */
if (z < 128) {
z += 2;
} else if (z < 256) {
z += 3;
} else if (z < 65536UL) {
z += 4;
} else {
return CRYPT_INVALID_ARG;
}
*outlen = z;
return CRYPT_OK;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/object_identifier/der_length_object_identifier.c,v $ */
/* $Revision: 1.4 $ */
/* $Date: 2006/04/16 20:17:42 $ */
|
