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_decode_utctime.c
15  ASN.1 DER, decode a  UTCTIME, Tom St Denis
16*/
17
18#ifdef LTC_DER
19
20static int char_to_int(unsigned char x)
21{
22   switch (x)  {
23      case '0': return 0;
24      case '1': return 1;
25      case '2': return 2;
26      case '3': return 3;
27      case '4': return 4;
28      case '5': return 5;
29      case '6': return 6;
30      case '7': return 7;
31      case '8': return 8;
32      case '9': return 9;
33   }
34   return 100;
35}
36
37#define DECODE_V(y, max) \
38   y  = char_to_int(buf[x])*10 + char_to_int(buf[x+1]); \
39   if (y >= max) return CRYPT_INVALID_PACKET;           \
40   x += 2;
41
42/**
43  Decodes a UTC time structure in DER format (reads all 6 valid encoding formats)
44  @param in     Input buffer
45  @param inlen  Length of input buffer in octets
46  @param out    [out] Destination of UTC time structure
47  @return CRYPT_OK   if successful
48*/
49int der_decode_utctime(const unsigned char *in, unsigned long *inlen,
50                             ltc_utctime   *out)
51{
52   unsigned char buf[32];
53   unsigned long x;
54   int           y;
55
56   LTC_ARGCHK(in    != NULL);
57   LTC_ARGCHK(inlen != NULL);
58   LTC_ARGCHK(out   != NULL);
59
60   /* check header */
61   if (*inlen < 2UL || (in[1] >= sizeof(buf)) || ((in[1] + 2UL) > *inlen)) {
62      return CRYPT_INVALID_PACKET;
63   }
64
65   /* decode the string */
66   for (x = 0; x < in[1]; x++) {
67       y = der_ia5_value_decode(in[x+2]);
68       if (y == -1) {
69          return CRYPT_INVALID_PACKET;
70       }
71       buf[x] = y;
72   }
73   *inlen = 2 + x;
74
75
76   /* possible encodings are
77YYMMDDhhmmZ
78YYMMDDhhmm+hh'mm'
79YYMMDDhhmm-hh'mm'
80YYMMDDhhmmssZ
81YYMMDDhhmmss+hh'mm'
82YYMMDDhhmmss-hh'mm'
83
84    So let's do a trivial decode upto [including] mm
85   */
86
87    x = 0;
88    DECODE_V(out->YY, 100);
89    DECODE_V(out->MM, 13);
90    DECODE_V(out->DD, 32);
91    DECODE_V(out->hh, 24);
92    DECODE_V(out->mm, 60);
93
94    /* clear timezone and seconds info */
95    out->off_dir = out->off_hh = out->off_mm = out->ss = 0;
96
97    /* now is it Z, +, - or 0-9 */
98    if (buf[x] == 'Z') {
99       return CRYPT_OK;
100    } else 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    } else if (buf[x] == '+' || buf[x] == '-') {
114       out->off_dir = (buf[x++] == '+') ? 0 : 1;
115       DECODE_V(out->off_hh, 24);
116       DECODE_V(out->off_mm, 60);
117       return CRYPT_OK;
118    } else {
119       return CRYPT_INVALID_PACKET;
120    }
121}
122
123#endif
124
125/* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/utctime/der_decode_utctime.c,v $ */
126/* $Revision: 1.8 $ */
127/* $Date: 2006/03/31 14:15:35 $ */
128