1 /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
2 /* This code placed in the public domain by Mark W. Eichin */
3
4 #include "autoconf.h"
5 #include <stdio.h>
6
7 #ifdef HAVE_SYS_TYPES_H
8 #include <sys/types.h>
9 #endif
10 #ifdef HAVE_SYS_TIME_H
11 #include <sys/time.h>
12 #endif
13 #include <time.h>
14
15 #include "k5-gmt_mktime.h"
16
17 #if !HAVE_TIMEGM || TEST_LEAP
18 static time_t gmt_mktime(struct tm *t);
19 #endif
20
21 /*
22 * Use the nonstandard timegm() (if available) to convert broken-down
23 * UTC times into time_t values. Use our custom gmt_mktime() if
24 * timegm() is not available.
25 *
26 * We use gmtime() (or gmtime_r()) when encoding ASN.1 GeneralizedTime
27 * values. On systems where a "right" (leap-second-aware) time zone
28 * is configured, gmtime() adjusts for the presence of accumulated
29 * leap seconds in the input time_t value. POSIX requires that time_t
30 * values omit leap seconds; systems configured to include leap
31 * seconds in their time_t values are non-conforming and will have
32 * difficulties exchanging timestamp information with other systems.
33 *
34 * We use krb5int_gmt_mktime() for decoding ASN.1 GeneralizedTime
35 * values. If timegm() is not available, krb5int_gmt_mktime() won't
36 * be the inverse of gmtime() on a system that counts leap seconds. A
37 * system configured with a "right" time zone probably has timegm()
38 * available; without it, an application would have no reliable way of
39 * converting broken-down UTC times into time_t values.
40 */
41 time_t
krb5int_gmt_mktime(struct tm * t)42 krb5int_gmt_mktime(struct tm *t)
43 {
44 #if HAVE_TIMEGM
45 return timegm(t);
46 #else
47 return gmt_mktime(t);
48 #endif
49 }
50
51 #if !HAVE_TIMEGM || TEST_LEAP
52
53 /* take a struct tm, return seconds from GMT epoch */
54 /* like mktime, this ignores tm_wday and tm_yday. */
55 /* unlike mktime, this does not set them... it only passes a return value. */
56
57 static const int days_in_month[12] = {
58 0, /* jan 31 */
59 31, /* feb 28 */
60 59, /* mar 31 */
61 90, /* apr 30 */
62 120, /* may 31 */
63 151, /* jun 30 */
64 181, /* jul 31 */
65 212, /* aug 31 */
66 243, /* sep 30 */
67 273, /* oct 31 */
68 304, /* nov 30 */
69 334 /* dec 31 */
70 };
71
72 #define hasleapday(year) (year%400?(year%100?(year%4?0:1):0):1)
73
74 static time_t
gmt_mktime(struct tm * t)75 gmt_mktime(struct tm *t)
76 {
77 uint32_t accum;
78
79 #define assert_time(cnd) if(!(cnd)) return (time_t) -1
80
81 /*
82 * For 32-bit unsigned time values starting on 1/1/1970, the range is:
83 * time 0x00000000 -> Thu Jan 1 00:00:00 1970
84 * time 0xffffffff -> Sun Feb 7 06:28:15 2106
85 *
86 * We can't encode all dates in 2106, and we're not doing overflow checking
87 * for such cases.
88 */
89 assert_time(t->tm_year>=70);
90 assert_time(t->tm_year<=206);
91
92 assert_time(t->tm_mon>=0);
93 assert_time(t->tm_mon<=11);
94 assert_time(t->tm_mday>=1);
95 assert_time(t->tm_mday<=31);
96 assert_time(t->tm_hour>=0);
97 assert_time(t->tm_hour<=23);
98 assert_time(t->tm_min>=0);
99 assert_time(t->tm_min<=59);
100 assert_time(t->tm_sec>=0);
101 assert_time(t->tm_sec<=62);
102
103 #undef assert_time
104
105
106 accum = t->tm_year - 70;
107 accum *= 365; /* 365 days/normal year */
108
109 /* add in leap day for all previous years */
110 if (t->tm_year >= 70)
111 accum += (t->tm_year - 69) / 4;
112 else
113 accum -= (72 - t->tm_year) / 4;
114 /* add in leap day for this year */
115 if(t->tm_mon >= 2) /* march or later */
116 if(hasleapday((t->tm_year + 1900))) accum += 1;
117
118 accum += days_in_month[t->tm_mon];
119 accum += t->tm_mday-1; /* days of month are the only 1-based field */
120 accum *= 24; /* 24 hour/day */
121 accum += t->tm_hour;
122 accum *= 60; /* 60 minute/hour */
123 accum += t->tm_min;
124 accum *= 60; /* 60 seconds/minute */
125 accum += t->tm_sec;
126
127 return accum;
128 }
129 #endif /* !HAVE_TIMEGM || TEST_LEAP */
130
131 #ifdef TEST_LEAP
132 int
main(int argc,char * argv[])133 main (int argc, char *argv[])
134 {
135 int yr;
136 time_t t;
137 struct tm tm = {
138 .tm_mon = 0, .tm_mday = 1,
139 .tm_hour = 0, .tm_min = 0, .tm_sec = 0,
140 };
141 for (yr = 60; yr <= 104; yr++)
142 {
143 printf ("1/1/%d%c -> ", 1900 + yr, hasleapday((1900+yr)) ? '*' : ' ');
144 tm.tm_year = yr;
145 t = gmt_mktime (&tm);
146 if (t == (time_t) -1)
147 printf ("-1\n");
148 else
149 {
150 long u;
151 if (t % (24 * 60 * 60))
152 printf ("(not integral multiple of days) ");
153 u = t / (24 * 60 * 60);
154 printf ("%3ld*365%+ld\t0x%08lx\n",
155 (long) (u / 365), (long) (u % 365),
156 (long) t);
157 }
158 }
159 t = 0x80000000, printf ("time 0x%lx -> %s", t, ctime (&t));
160 t = 0x7fffffff, printf ("time 0x%lx -> %s", t, ctime (&t));
161 return 0;
162 }
163 #endif
164