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/* 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://libtom.org
*/
#include "tomcrypt.h"
/**
@file der_decode_utctime.c
ASN.1 DER, decode a UTCTIME, Tom St Denis
*/
#ifdef LTC_DER
static int char_to_int(unsigned char x)
{
switch (x) {
case '0': return 0;
case '1': return 1;
case '2': return 2;
case '3': return 3;
case '4': return 4;
case '5': return 5;
case '6': return 6;
case '7': return 7;
case '8': return 8;
case '9': return 9;
}
return 100;
}
#define DECODE_V(y, max) \
y = char_to_int(buf[x])*10 + char_to_int(buf[x+1]); \
if (y >= max) return CRYPT_INVALID_PACKET; \
x += 2;
/**
Decodes a UTC time structure in DER format (reads all 6 valid encoding formats)
@param in Input buffer
@param inlen Length of input buffer in octets
@param out [out] Destination of UTC time structure
@return CRYPT_OK if successful
*/
int der_decode_utctime(const unsigned char *in, unsigned long *inlen,
ltc_utctime *out)
{
unsigned char buf[32];
unsigned long x;
int y;
LTC_ARGCHK(in != NULL);
LTC_ARGCHK(inlen != NULL);
LTC_ARGCHK(out != NULL);
/* check header */
if (*inlen < 2UL || (in[1] >= sizeof(buf)) || ((in[1] + 2UL) > *inlen)) {
return CRYPT_INVALID_PACKET;
}
/* decode the string */
for (x = 0; x < in[1]; x++) {
y = der_ia5_value_decode(in[x+2]);
if (y == -1) {
return CRYPT_INVALID_PACKET;
}
buf[x] = y;
}
*inlen = 2 + x;
/* possible encodings are
YYMMDDhhmmZ
YYMMDDhhmm+hh'mm'
YYMMDDhhmm-hh'mm'
YYMMDDhhmmssZ
YYMMDDhhmmss+hh'mm'
YYMMDDhhmmss-hh'mm'
So let's do a trivial decode upto [including] mm
*/
x = 0;
DECODE_V(out->YY, 100);
DECODE_V(out->MM, 13);
DECODE_V(out->DD, 32);
DECODE_V(out->hh, 24);
DECODE_V(out->mm, 60);
/* clear timezone and seconds info */
out->off_dir = out->off_hh = out->off_mm = out->ss = 0;
/* now is it Z, +, - or 0-9 */
if (buf[x] == 'Z') {
return CRYPT_OK;
} else if (buf[x] == '+' || buf[x] == '-') {
out->off_dir = (buf[x++] == '+') ? 0 : 1;
DECODE_V(out->off_hh, 24);
DECODE_V(out->off_mm, 60);
return CRYPT_OK;
}
/* decode seconds */
DECODE_V(out->ss, 60);
/* now is it Z, +, - */
if (buf[x] == 'Z') {
return CRYPT_OK;
} else if (buf[x] == '+' || buf[x] == '-') {
out->off_dir = (buf[x++] == '+') ? 0 : 1;
DECODE_V(out->off_hh, 24);
DECODE_V(out->off_mm, 60);
return CRYPT_OK;
} else {
return CRYPT_INVALID_PACKET;
}
}
#endif
/* $Source$ */
/* $Revision$ */
/* $Date$ */
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