xref: /freebsd/crypto/openssl/doc/man3/ASN1_TIME_set.pod (revision 8ddb146abcdf061be9f2c0db7e391697dafad85c) 
1=pod
2
3=head1 NAME
4
5ASN1_TIME_set, ASN1_UTCTIME_set, ASN1_GENERALIZEDTIME_set,
6ASN1_TIME_adj, ASN1_UTCTIME_adj, ASN1_GENERALIZEDTIME_adj,
7ASN1_TIME_check, ASN1_UTCTIME_check, ASN1_GENERALIZEDTIME_check,
8ASN1_TIME_set_string, ASN1_UTCTIME_set_string, ASN1_GENERALIZEDTIME_set_string,
9ASN1_TIME_set_string_X509,
10ASN1_TIME_normalize,
11ASN1_TIME_to_tm,
12ASN1_TIME_print, ASN1_UTCTIME_print, ASN1_GENERALIZEDTIME_print,
13ASN1_TIME_diff,
14ASN1_TIME_cmp_time_t, ASN1_UTCTIME_cmp_time_t,
15ASN1_TIME_compare,
16ASN1_TIME_to_generalizedtime - ASN.1 Time functions
17
18=head1 SYNOPSIS
19
20 ASN1_TIME *ASN1_TIME_set(ASN1_TIME *s, time_t t);
21 ASN1_UTCTIME *ASN1_UTCTIME_set(ASN1_UTCTIME *s, time_t t);
22 ASN1_GENERALIZEDTIME *ASN1_GENERALIZEDTIME_set(ASN1_GENERALIZEDTIME *s,
23                                                time_t t);
24
25 ASN1_TIME *ASN1_TIME_adj(ASN1_TIME *s, time_t t, int offset_day,
26                          long offset_sec);
27 ASN1_UTCTIME *ASN1_UTCTIME_adj(ASN1_UTCTIME *s, time_t t,
28                                int offset_day, long offset_sec);
29 ASN1_GENERALIZEDTIME *ASN1_GENERALIZEDTIME_adj(ASN1_GENERALIZEDTIME *s,
30                                                time_t t, int offset_day,
31                                                long offset_sec);
32
33 int ASN1_TIME_set_string(ASN1_TIME *s, const char *str);
34 int ASN1_TIME_set_string_X509(ASN1_TIME *s, const char *str);
35 int ASN1_UTCTIME_set_string(ASN1_UTCTIME *s, const char *str);
36 int ASN1_GENERALIZEDTIME_set_string(ASN1_GENERALIZEDTIME *s,
37                                     const char *str);
38
39 int ASN1_TIME_normalize(ASN1_TIME *s);
40
41 int ASN1_TIME_check(const ASN1_TIME *t);
42 int ASN1_UTCTIME_check(const ASN1_UTCTIME *t);
43 int ASN1_GENERALIZEDTIME_check(const ASN1_GENERALIZEDTIME *t);
44
45 int ASN1_TIME_print(BIO *b, const ASN1_TIME *s);
46 int ASN1_UTCTIME_print(BIO *b, const ASN1_UTCTIME *s);
47 int ASN1_GENERALIZEDTIME_print(BIO *b, const ASN1_GENERALIZEDTIME *s);
48
49 int ASN1_TIME_to_tm(const ASN1_TIME *s, struct tm *tm);
50 int ASN1_TIME_diff(int *pday, int *psec, const ASN1_TIME *from,
51                    const ASN1_TIME *to);
52
53 int ASN1_TIME_cmp_time_t(const ASN1_TIME *s, time_t t);
54 int ASN1_UTCTIME_cmp_time_t(const ASN1_UTCTIME *s, time_t t);
55
56 int ASN1_TIME_compare(const ASN1_TIME *a, const ASN1_TIME *b);
57
58 ASN1_GENERALIZEDTIME *ASN1_TIME_to_generalizedtime(ASN1_TIME *t,
59                                                    ASN1_GENERALIZEDTIME **out);
60
61=head1 DESCRIPTION
62
63The ASN1_TIME_set(), ASN1_UTCTIME_set() and ASN1_GENERALIZEDTIME_set()
64functions set the structure B<s> to the time represented by the time_t
65value B<t>. If B<s> is NULL a new time structure is allocated and returned.
66
67The ASN1_TIME_adj(), ASN1_UTCTIME_adj() and ASN1_GENERALIZEDTIME_adj()
68functions set the time structure B<s> to the time represented
69by the time B<offset_day> and B<offset_sec> after the time_t value B<t>.
70The values of B<offset_day> or B<offset_sec> can be negative to set a
71time before B<t>. The B<offset_sec> value can also exceed the number of
72seconds in a day. If B<s> is NULL a new structure is allocated
73and returned.
74
75The ASN1_TIME_set_string(), ASN1_UTCTIME_set_string() and
76ASN1_GENERALIZEDTIME_set_string() functions set the time structure B<s>
77to the time represented by string B<str> which must be in appropriate ASN.1
78time format (for example YYMMDDHHMMSSZ or YYYYMMDDHHMMSSZ). If B<s> is NULL
79this function performs a format check on B<str> only. The string B<str>
80is copied into B<s>.
81
82ASN1_TIME_set_string_X509() sets ASN1_TIME structure B<s> to the time
83represented by string B<str> which must be in appropriate time format
84that RFC 5280 requires, which means it only allows YYMMDDHHMMSSZ and
85YYYYMMDDHHMMSSZ (leap second is rejected), all other ASN.1 time format
86are not allowed. If B<s> is NULL this function performs a format check
87on B<str> only.
88
89The ASN1_TIME_normalize() function converts an ASN1_GENERALIZEDTIME or
90ASN1_UTCTIME into a time value that can be used in a certificate. It
91should be used after the ASN1_TIME_set_string() functions and before
92ASN1_TIME_print() functions to get consistent (i.e. GMT) results.
93
94The ASN1_TIME_check(), ASN1_UTCTIME_check() and ASN1_GENERALIZEDTIME_check()
95functions check the syntax of the time structure B<s>.
96
97The ASN1_TIME_print(), ASN1_UTCTIME_print() and ASN1_GENERALIZEDTIME_print()
98functions print the time structure B<s> to BIO B<b> in human readable
99format. It will be of the format MMM DD HH:MM:SS YYYY [GMT], for example
100"Feb  3 00:55:52 2015 GMT" it does not include a newline. If the time
101structure has invalid format it prints out "Bad time value" and returns
102an error. The output for generalized time may include a fractional part
103following the second.
104
105ASN1_TIME_to_tm() converts the time B<s> to the standard B<tm> structure.
106If B<s> is NULL, then the current time is converted. The output time is GMT.
107The B<tm_sec>, B<tm_min>, B<tm_hour>, B<tm_mday>, B<tm_wday>, B<tm_yday>,
108B<tm_mon> and B<tm_year> fields of B<tm> structure are set to proper values,
109whereas all other fields are set to 0. If B<tm> is NULL this function performs
110a format check on B<s> only. If B<s> is in Generalized format with fractional
111seconds, e.g. YYYYMMDDHHMMSS.SSSZ, the fractional seconds will be lost while
112converting B<s> to B<tm> structure.
113
114ASN1_TIME_diff() sets B<*pday> and B<*psec> to the time difference between
115B<from> and B<to>. If B<to> represents a time later than B<from> then
116one or both (depending on the time difference) of B<*pday> and B<*psec>
117will be positive. If B<to> represents a time earlier than B<from> then
118one or both of B<*pday> and B<*psec> will be negative. If B<to> and B<from>
119represent the same time then B<*pday> and B<*psec> will both be zero.
120If both B<*pday> and B<*psec> are nonzero they will always have the same
121sign. The value of B<*psec> will always be less than the number of seconds
122in a day. If B<from> or B<to> is NULL the current time is used.
123
124The ASN1_TIME_cmp_time_t() and ASN1_UTCTIME_cmp_time_t() functions compare
125the two times represented by the time structure B<s> and the time_t B<t>.
126
127The ASN1_TIME_compare() function compares the two times represented by the
128time structures B<a> and B<b>.
129
130The ASN1_TIME_to_generalizedtime() function converts an ASN1_TIME to an
131ASN1_GENERALIZEDTIME, regardless of year. If either B<out> or
132B<*out> are NULL, then a new object is allocated and must be freed after use.
133
134=head1 NOTES
135
136The ASN1_TIME structure corresponds to the ASN.1 structure B<Time>
137defined in RFC5280 et al. The time setting functions obey the rules outlined
138in RFC5280: if the date can be represented by UTCTime it is used, else
139GeneralizedTime is used.
140
141The ASN1_TIME, ASN1_UTCTIME and ASN1_GENERALIZEDTIME structures are represented
142as an ASN1_STRING internally and can be freed up using ASN1_STRING_free().
143
144The ASN1_TIME structure can represent years from 0000 to 9999 but no attempt
145is made to correct ancient calendar changes (for example from Julian to
146Gregorian calendars).
147
148ASN1_UTCTIME is limited to a year range of 1950 through 2049.
149
150Some applications add offset times directly to a time_t value and pass the
151results to ASN1_TIME_set() (or equivalent). This can cause problems as the
152time_t value can overflow on some systems resulting in unexpected results.
153New applications should use ASN1_TIME_adj() instead and pass the offset value
154in the B<offset_sec> and B<offset_day> parameters instead of directly
155manipulating a time_t value.
156
157ASN1_TIME_adj() may change the type from ASN1_GENERALIZEDTIME to ASN1_UTCTIME,
158or vice versa, based on the resulting year. The ASN1_GENERALIZEDTIME_adj() and
159ASN1_UTCTIME_adj() functions will not modify the type of the return structure.
160
161It is recommended that functions starting with ASN1_TIME be used instead of
162those starting with ASN1_UTCTIME or ASN1_GENERALIZEDTIME. The functions
163starting with ASN1_UTCTIME and ASN1_GENERALIZEDTIME act only on that specific
164time format. The functions starting with ASN1_TIME will operate on either
165format.
166
167=head1 BUGS
168
169ASN1_TIME_print(), ASN1_UTCTIME_print() and ASN1_GENERALIZEDTIME_print()
170do not print out the timezone: it either prints out "GMT" or nothing. But all
171certificates complying with RFC5280 et al use GMT anyway.
172
173Use the ASN1_TIME_normalize() function to normalize the time value before
174printing to get GMT results.
175
176=head1 RETURN VALUES
177
178ASN1_TIME_set(), ASN1_UTCTIME_set(), ASN1_GENERALIZEDTIME_set(), ASN1_TIME_adj(),
179ASN1_UTCTIME_adj and ASN1_GENERALIZEDTIME_set return a pointer to a time structure
180or NULL if an error occurred.
181
182ASN1_TIME_set_string(), ASN1_UTCTIME_set_string(), ASN1_GENERALIZEDTIME_set_string()
183ASN1_TIME_set_string_X509() return 1 if the time value is successfully set and 0 otherwise.
184
185ASN1_TIME_normalize() returns 1 on success, and 0 on error.
186
187ASN1_TIME_check(), ASN1_UTCTIME_check and ASN1_GENERALIZEDTIME_check() return 1
188if the structure is syntactically correct and 0 otherwise.
189
190ASN1_TIME_print(), ASN1_UTCTIME_print() and ASN1_GENERALIZEDTIME_print() return 1
191if the time is successfully printed out and 0 if an error occurred (I/O error or
192invalid time format).
193
194ASN1_TIME_to_tm() returns 1 if the time is successfully parsed and 0 if an
195error occurred (invalid time format).
196
197ASN1_TIME_diff() returns 1 for success and 0 for failure. It can fail if the
198passed-in time structure has invalid syntax, for example.
199
200ASN1_TIME_cmp_time_t() and ASN1_UTCTIME_cmp_time_t() return -1 if B<s> is
201before B<t>, 0 if B<s> equals B<t>, or 1 if B<s> is after B<t>. -2 is returned
202on error.
203
204ASN1_TIME_compare() returns -1 if B<a> is before B<b>, 0 if B<a> equals B<b>, or 1 if B<a> is after B<b>. -2 is returned on error.
205
206ASN1_TIME_to_generalizedtime() returns a pointer to
207the appropriate time structure on success or NULL if an error occurred.
208
209=head1 EXAMPLES
210
211Set a time structure to one hour after the current time and print it out:
212
213 #include <time.h>
214 #include <openssl/asn1.h>
215
216 ASN1_TIME *tm;
217 time_t t;
218 BIO *b;
219
220 t = time(NULL);
221 tm = ASN1_TIME_adj(NULL, t, 0, 60 * 60);
222 b = BIO_new_fp(stdout, BIO_NOCLOSE);
223 ASN1_TIME_print(b, tm);
224 ASN1_STRING_free(tm);
225 BIO_free(b);
226
227Determine if one time is later or sooner than the current time:
228
229 int day, sec;
230
231 if (!ASN1_TIME_diff(&day, &sec, NULL, to))
232     /* Invalid time format */
233
234 if (day > 0 || sec > 0)
235     printf("Later\n");
236 else if (day < 0 || sec < 0)
237     printf("Sooner\n");
238 else
239     printf("Same\n");
240
241=head1 HISTORY
242
243The ASN1_TIME_to_tm() function was added in OpenSSL 1.1.1.
244The ASN1_TIME_set_string_X509() function was added in OpenSSL 1.1.1.
245The ASN1_TIME_normalize() function was added in OpenSSL 1.1.1.
246The ASN1_TIME_cmp_time_t() function was added in OpenSSL 1.1.1.
247The ASN1_TIME_compare() function was added in OpenSSL 1.1.1.
248
249=head1 COPYRIGHT
250
251Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.
252
253Licensed under the OpenSSL license (the "License").  You may not use
254this file except in compliance with the License.  You can obtain a copy
255in the file LICENSE in the source distribution or at
256L<https://www.openssl.org/source/license.html>.
257
258=cut
259