1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis */
2 /* SPDX-License-Identifier: Unlicense */
3 #include "tomcrypt_private.h"
4
5 /**
6 @file der_encode_object_identifier.c
7 ASN.1 DER, Encode Object Identifier, Tom St Denis
8 */
9
10 #ifdef LTC_DER
11 /**
12 Encode an OID
13 @param words The words to encode (upto 32-bits each)
14 @param nwords The number of words in the OID
15 @param out [out] Destination of OID data
16 @param outlen [in/out] The max and resulting size of the OID
17 @return CRYPT_OK if successful
18 */
der_encode_object_identifier(const unsigned long * words,unsigned long nwords,unsigned char * out,unsigned long * outlen)19 int der_encode_object_identifier(const unsigned long *words, unsigned long nwords,
20 unsigned char *out, unsigned long *outlen)
21 {
22 unsigned long i, x, y, z, t, mask, wordbuf;
23 int err;
24
25 LTC_ARGCHK(words != NULL);
26 LTC_ARGCHK(out != NULL);
27 LTC_ARGCHK(outlen != NULL);
28
29 /* check length */
30 if ((err = der_length_object_identifier(words, nwords, &x)) != CRYPT_OK) {
31 return err;
32 }
33 if (x > *outlen) {
34 *outlen = x;
35 return CRYPT_BUFFER_OVERFLOW;
36 }
37
38 /* compute length to store OID data */
39 z = 0;
40 wordbuf = words[0] * 40 + words[1];
41 for (y = 1; y < nwords; y++) {
42 t = der_object_identifier_bits(wordbuf);
43 z += t/7 + ((t%7) ? 1 : 0) + (wordbuf == 0 ? 1 : 0);
44 if (y < nwords - 1) {
45 wordbuf = words[y + 1];
46 }
47 }
48
49 /* store header + length */
50 x = 0;
51 out[x++] = 0x06;
52 y = *outlen - x;
53 if ((err = der_encode_asn1_length(z, out + x, &y)) != CRYPT_OK) {
54 return err;
55 }
56 x += y;
57
58 /* store first byte */
59 wordbuf = words[0] * 40 + words[1];
60 for (i = 1; i < nwords; i++) {
61 /* store 7 bit words in little endian */
62 t = wordbuf & 0xFFFFFFFF;
63 if (t) {
64 y = x;
65 mask = 0;
66 while (t) {
67 out[x++] = (unsigned char)((t & 0x7F) | mask);
68 t >>= 7;
69 mask |= 0x80; /* upper bit is set on all but the last byte */
70 }
71 /* now swap bytes y...x-1 */
72 z = x - 1;
73 while (y < z) {
74 t = out[y]; out[y] = out[z]; out[z] = (unsigned char)t;
75 ++y;
76 --z;
77 }
78 } else {
79 /* zero word */
80 out[x++] = 0x00;
81 }
82
83 if (i < nwords - 1) {
84 wordbuf = words[i + 1];
85 }
86 }
87
88 *outlen = x;
89 return CRYPT_OK;
90 }
91
92 #endif
93