1 // SPDX-License-Identifier: BSD-2-Clause
2 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
3 *
4 * LibTomCrypt is a library that provides various cryptographic
5 * algorithms in a highly modular and flexible manner.
6 *
7 * The library is free for all purposes without any express
8 * guarantee it works.
9 */
10 #include "tomcrypt_private.h"
11
12 /**
13 @file der_decode_utctime.c
14 ASN.1 DER, decode a UTCTIME, Tom St Denis
15 */
16
17 #ifdef LTC_DER
18
_char_to_int(unsigned char x)19 static int _char_to_int(unsigned char x)
20 {
21 switch (x) {
22 case '0': return 0;
23 case '1': return 1;
24 case '2': return 2;
25 case '3': return 3;
26 case '4': return 4;
27 case '5': return 5;
28 case '6': return 6;
29 case '7': return 7;
30 case '8': return 8;
31 case '9': return 9;
32 default: return 100;
33 }
34 }
35
36 #define DECODE_V(y, max) \
37 y = _char_to_int(buf[x])*10 + _char_to_int(buf[x+1]); \
38 if (y >= max) return CRYPT_INVALID_PACKET; \
39 x += 2;
40
41 /**
42 Decodes a UTC time structure in DER format (reads all 6 valid encoding formats)
43 @param in Input buffer
44 @param inlen Length of input buffer in octets
45 @param out [out] Destination of UTC time structure
46 @return CRYPT_OK if successful
47 */
der_decode_utctime(const unsigned char * in,unsigned long * inlen,ltc_utctime * out)48 int der_decode_utctime(const unsigned char *in, unsigned long *inlen,
49 ltc_utctime *out)
50 {
51 unsigned char buf[32] = { 0 }; /* initialize as all zeroes */
52 unsigned long x;
53 int y;
54
55 LTC_ARGCHK(in != NULL);
56 LTC_ARGCHK(inlen != NULL);
57 LTC_ARGCHK(out != NULL);
58
59 /* check header */
60 if (*inlen < 2UL || (in[1] >= sizeof(buf)) || ((in[1] + 2UL) > *inlen)) {
61 return CRYPT_INVALID_PACKET;
62 }
63
64 /* decode the string */
65 for (x = 0; x < in[1]; x++) {
66 y = der_ia5_value_decode(in[x+2]);
67 if (y == -1) {
68 return CRYPT_INVALID_PACKET;
69 }
70 buf[x] = y;
71 }
72 *inlen = 2 + x;
73
74
75 /* possible encodings are
76 YYMMDDhhmmZ
77 YYMMDDhhmm+hh'mm'
78 YYMMDDhhmm-hh'mm'
79 YYMMDDhhmmssZ
80 YYMMDDhhmmss+hh'mm'
81 YYMMDDhhmmss-hh'mm'
82
83 So let's do a trivial decode upto [including] mm
84 */
85
86 x = 0;
87 DECODE_V(out->YY, 100);
88 DECODE_V(out->MM, 13);
89 DECODE_V(out->DD, 32);
90 DECODE_V(out->hh, 24);
91 DECODE_V(out->mm, 60);
92
93 /* clear timezone and seconds info */
94 out->off_dir = out->off_hh = out->off_mm = out->ss = 0;
95
96 /* now is it Z, +, - or 0-9 */
97 if (buf[x] == 'Z') {
98 return CRYPT_OK;
99 }
100 if (buf[x] == '+' || buf[x] == '-') {
101 out->off_dir = (buf[x++] == '+') ? 0 : 1;
102 DECODE_V(out->off_hh, 24);
103 DECODE_V(out->off_mm, 60);
104 return CRYPT_OK;
105 }
106
107 /* decode seconds */
108 DECODE_V(out->ss, 60);
109
110 /* now is it Z, +, - */
111 if (buf[x] == 'Z') {
112 return CRYPT_OK;
113 }
114 if (buf[x] == '+' || buf[x] == '-') {
115 out->off_dir = (buf[x++] == '+') ? 0 : 1;
116 DECODE_V(out->off_hh, 24);
117 DECODE_V(out->off_mm, 60);
118 return CRYPT_OK;
119 }
120 return CRYPT_INVALID_PACKET;
121 }
122
123 #endif
124
125 /* ref: $Format:%D$ */
126 /* git commit: $Format:%H$ */
127 /* commit time: $Format:%ai$ */
128