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      1 /*	$NetBSD: timegm.c,v 1.2 2017/01/28 21:31:45 christos Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1997 Kungliga Tekniska Hgskolan
      5  * (Royal Institute of Technology, Stockholm, Sweden).
      6  * All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  *
     12  * 1. Redistributions of source code must retain the above copyright
     13  *    notice, this list of conditions and the following disclaimer.
     14  *
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * 3. Neither the name of the Institute nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #include "der_locl.h"
     37 
     38 #define ASN1_MAX_YEAR	2000
     39 
     40 static int
     41 is_leap(unsigned y)
     42 {
     43     y += 1900;
     44     return (y % 4) == 0 && ((y % 100) != 0 || (y % 400) == 0);
     45 }
     46 
     47 static const unsigned ndays[2][12] ={
     48     {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
     49     {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}};
     50 
     51 /*
     52  * This is a simplifed version of timegm(3) that doesn't accept out of
     53  * bound values that timegm(3) normally accepts but those are not
     54  * valid in asn1 encodings.
     55  */
     56 
     57 time_t
     58 _der_timegm (struct tm *tm)
     59 {
     60   time_t res = 0;
     61   int i;
     62 
     63   /*
     64    * See comment in _der_gmtime
     65    */
     66   if (tm->tm_year > ASN1_MAX_YEAR)
     67       return 0;
     68 
     69   if (tm->tm_year < 0)
     70       return -1;
     71   if (tm->tm_mon < 0 || tm->tm_mon > 11)
     72       return -1;
     73   if (tm->tm_mday < 1 || tm->tm_mday > (int)ndays[is_leap(tm->tm_year)][tm->tm_mon])
     74       return -1;
     75   if (tm->tm_hour < 0 || tm->tm_hour > 23)
     76       return -1;
     77   if (tm->tm_min < 0 || tm->tm_min > 59)
     78       return -1;
     79   if (tm->tm_sec < 0 || tm->tm_sec > 59)
     80       return -1;
     81 
     82   for (i = 70; i < tm->tm_year; ++i)
     83     res += is_leap(i) ? 366 : 365;
     84 
     85   for (i = 0; i < tm->tm_mon; ++i)
     86     res += ndays[is_leap(tm->tm_year)][i];
     87   res += tm->tm_mday - 1;
     88   res *= 24;
     89   res += tm->tm_hour;
     90   res *= 60;
     91   res += tm->tm_min;
     92   res *= 60;
     93   res += tm->tm_sec;
     94   return res;
     95 }
     96 
     97 struct tm *
     98 _der_gmtime(time_t t, struct tm *tm)
     99 {
    100     time_t secday = t % (3600 * 24);
    101     time_t days = t / (3600 * 24);
    102 
    103     memset(tm, 0, sizeof(*tm));
    104 
    105     tm->tm_sec = secday % 60;
    106     tm->tm_min = (secday % 3600) / 60;
    107     tm->tm_hour = (int)(secday / 3600);
    108 
    109     /*
    110      * Refuse to calculate time ~ 2000 years into the future, this is
    111      * not possible for systems where time_t is a int32_t, however,
    112      * when time_t is a int64_t, that can happen, and this becomes a
    113      * denial of sevice.
    114      */
    115     if (days > (ASN1_MAX_YEAR * 365))
    116 	return NULL;
    117 
    118     tm->tm_year = 70;
    119     while(1) {
    120 	unsigned dayinyear = (is_leap(tm->tm_year) ? 366 : 365);
    121 	if (days < dayinyear)
    122 	    break;
    123 	tm->tm_year += 1;
    124 	days -= dayinyear;
    125     }
    126     tm->tm_mon = 0;
    127 
    128     while (1) {
    129 	unsigned daysinmonth = ndays[is_leap(tm->tm_year)][tm->tm_mon];
    130 	if (days < daysinmonth)
    131 	    break;
    132 	days -= daysinmonth;
    133 	tm->tm_mon++;
    134     }
    135     tm->tm_mday = (int)(days + 1);
    136 
    137     return tm;
    138 }
    139