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✏️ Editing: ASN1_TIME_diff.3

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.\" ========================================================================
.\"
.IX Title "ASN1_TIME_SET 3"
.TH ASN1_TIME_SET 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
ASN1_TIME_set, ASN1_UTCTIME_set, ASN1_GENERALIZEDTIME_set, ASN1_TIME_adj, ASN1_UTCTIME_adj, ASN1_GENERALIZEDTIME_adj, ASN1_TIME_check, ASN1_UTCTIME_check, ASN1_GENERALIZEDTIME_check, ASN1_TIME_set_string, ASN1_UTCTIME_set_string, ASN1_GENERALIZEDTIME_set_string, ASN1_TIME_set_string_X509, ASN1_TIME_normalize, ASN1_TIME_to_tm, ASN1_TIME_print, ASN1_UTCTIME_print, ASN1_GENERALIZEDTIME_print, ASN1_TIME_diff, ASN1_TIME_cmp_time_t, ASN1_UTCTIME_cmp_time_t, ASN1_TIME_compare, ASN1_TIME_to_generalizedtime \- ASN.1 Time functions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 4
\& ASN1_TIME *ASN1_TIME_set(ASN1_TIME *s, time_t t);
\& ASN1_UTCTIME *ASN1_UTCTIME_set(ASN1_UTCTIME *s, time_t t);
\& ASN1_GENERALIZEDTIME *ASN1_GENERALIZEDTIME_set(ASN1_GENERALIZEDTIME *s,
\&                                                time_t t);
\&
\& ASN1_TIME *ASN1_TIME_adj(ASN1_TIME *s, time_t t, int offset_day,
\&                          long offset_sec);
\& ASN1_UTCTIME *ASN1_UTCTIME_adj(ASN1_UTCTIME *s, time_t t,
\&                                int offset_day, long offset_sec);
\& ASN1_GENERALIZEDTIME *ASN1_GENERALIZEDTIME_adj(ASN1_GENERALIZEDTIME *s,
\&                                                time_t t, int offset_day,
\&                                                long offset_sec);
\&
\& int ASN1_TIME_set_string(ASN1_TIME *s, const char *str);
\& int ASN1_TIME_set_string_X509(ASN1_TIME *s, const char *str);
\& int ASN1_UTCTIME_set_string(ASN1_UTCTIME *s, const char *str);
\& int ASN1_GENERALIZEDTIME_set_string(ASN1_GENERALIZEDTIME *s,
\&                                     const char *str);
\&
\& int ASN1_TIME_normalize(ASN1_TIME *s);
\&
\& int ASN1_TIME_check(const ASN1_TIME *t);
\& int ASN1_UTCTIME_check(const ASN1_UTCTIME *t);
\& int ASN1_GENERALIZEDTIME_check(const ASN1_GENERALIZEDTIME *t);
\&
\& int ASN1_TIME_print(BIO *b, const ASN1_TIME *s);
\& int ASN1_UTCTIME_print(BIO *b, const ASN1_UTCTIME *s);
\& int ASN1_GENERALIZEDTIME_print(BIO *b, const ASN1_GENERALIZEDTIME *s);
\&
\& int ASN1_TIME_to_tm(const ASN1_TIME *s, struct tm *tm);
\& int ASN1_TIME_diff(int *pday, int *psec, const ASN1_TIME *from,
\&                    const ASN1_TIME *to);
\&
\& int ASN1_TIME_cmp_time_t(const ASN1_TIME *s, time_t t);
\& int ASN1_UTCTIME_cmp_time_t(const ASN1_UTCTIME *s, time_t t);
\&
\& int ASN1_TIME_compare(const ASN1_TIME *a, const ASN1_TIME *b);
\&
\& ASN1_GENERALIZEDTIME *ASN1_TIME_to_generalizedtime(ASN1_TIME *t,
\&                                                    ASN1_GENERALIZEDTIME **out);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \fBASN1_TIME_set()\fR, \fBASN1_UTCTIME_set()\fR and \fBASN1_GENERALIZEDTIME_set()\fR
functions set the structure \fBs\fR to the time represented by the time_t
value \fBt\fR. If \fBs\fR is \s-1NULL\s0 a new time structure is allocated and returned.
.PP
The \fBASN1_TIME_adj()\fR, \fBASN1_UTCTIME_adj()\fR and \fBASN1_GENERALIZEDTIME_adj()\fR
functions set the time structure \fBs\fR to the time represented
by the time \fBoffset_day\fR and \fBoffset_sec\fR after the time_t value \fBt\fR.
The values of \fBoffset_day\fR or \fBoffset_sec\fR can be negative to set a
time before \fBt\fR. The \fBoffset_sec\fR value can also exceed the number of
seconds in a day. If \fBs\fR is \s-1NULL\s0 a new structure is allocated
and returned.
.PP
The \fBASN1_TIME_set_string()\fR, \fBASN1_UTCTIME_set_string()\fR and
\&\fBASN1_GENERALIZEDTIME_set_string()\fR functions set the time structure \fBs\fR
to the time represented by string \fBstr\fR which must be in appropriate \s-1ASN.1\s0
time format (for example \s-1YYMMDDHHMMSSZ\s0 or \s-1YYYYMMDDHHMMSSZ\s0). If \fBs\fR is \s-1NULL\s0
this function performs a format check on \fBstr\fR only. The string \fBstr\fR
is copied into \fBs\fR.
.PP
\&\fBASN1_TIME_set_string_X509()\fR sets \s-1ASN1_TIME\s0 structure \fBs\fR to the time
represented by string \fBstr\fR which must be in appropriate time format
that \s-1RFC 5280\s0 requires, which means it only allows \s-1YYMMDDHHMMSSZ\s0 and
\&\s-1YYYYMMDDHHMMSSZ\s0 (leap second is rejected), all other \s-1ASN.1\s0 time format
are not allowed. If \fBs\fR is \s-1NULL\s0 this function performs a format check
on \fBstr\fR only.
.PP
The \fBASN1_TIME_normalize()\fR function converts an \s-1ASN1_GENERALIZEDTIME\s0 or
\&\s-1ASN1_UTCTIME\s0 into a time value that can be used in a certificate. It
should be used after the \fBASN1_TIME_set_string()\fR functions and before
\&\fBASN1_TIME_print()\fR functions to get consistent (i.e. \s-1GMT\s0) results.
.PP
The \fBASN1_TIME_check()\fR, \fBASN1_UTCTIME_check()\fR and \fBASN1_GENERALIZEDTIME_check()\fR
functions check the syntax of the time structure \fBs\fR.
.PP
The \fBASN1_TIME_print()\fR, \fBASN1_UTCTIME_print()\fR and \fBASN1_GENERALIZEDTIME_print()\fR
functions print the time structure \fBs\fR to \s-1BIO\s0 \fBb\fR in human readable
format. It will be of the format \s-1MMM DD HH:MM:SS YYYY\s0 [\s-1GMT\s0], for example
\&\*(L"Feb  3 00:55:52 2015 \s-1GMT\*(R"\s0 it does not include a newline. If the time
structure has invalid format it prints out \*(L"Bad time value\*(R" and returns
an error. The output for generalized time may include a fractional part
following the second.
.PP
\&\fBASN1_TIME_to_tm()\fR converts the time \fBs\fR to the standard \fBtm\fR structure.
If \fBs\fR is \s-1NULL,\s0 then the current time is converted. The output time is \s-1GMT.\s0
The \fBtm_sec\fR, \fBtm_min\fR, \fBtm_hour\fR, \fBtm_mday\fR, \fBtm_wday\fR, \fBtm_yday\fR,
\&\fBtm_mon\fR and \fBtm_year\fR fields of \fBtm\fR structure are set to proper values,
whereas all other fields are set to 0. If \fBtm\fR is \s-1NULL\s0 this function performs
a format check on \fBs\fR only. If \fBs\fR is in Generalized format with fractional
seconds, e.g. \s-1YYYYMMDDHHMMSS.SSSZ,\s0 the fractional seconds will be lost while
converting \fBs\fR to \fBtm\fR structure.
.PP
\&\fBASN1_TIME_diff()\fR sets \fB*pday\fR and \fB*psec\fR to the time difference between
\&\fBfrom\fR and \fBto\fR. If \fBto\fR represents a time later than \fBfrom\fR then
one or both (depending on the time difference) of \fB*pday\fR and \fB*psec\fR
will be positive. If \fBto\fR represents a time earlier than \fBfrom\fR then
one or both of \fB*pday\fR and \fB*psec\fR will be negative. If \fBto\fR and \fBfrom\fR
represent the same time then \fB*pday\fR and \fB*psec\fR will both be zero.
If both \fB*pday\fR and \fB*psec\fR are nonzero they will always have the same
sign. The value of \fB*psec\fR will always be less than the number of seconds
in a day. If \fBfrom\fR or \fBto\fR is \s-1NULL\s0 the current time is used.
.PP
The \fBASN1_TIME_cmp_time_t()\fR and \fBASN1_UTCTIME_cmp_time_t()\fR functions compare
the two times represented by the time structure \fBs\fR and the time_t \fBt\fR.
.PP
The \fBASN1_TIME_compare()\fR function compares the two times represented by the
time structures \fBa\fR and \fBb\fR.
.PP
The \fBASN1_TIME_to_generalizedtime()\fR function converts an \s-1ASN1_TIME\s0 to an
\&\s-1ASN1_GENERALIZEDTIME,\s0 regardless of year. If either \fBout\fR or
\&\fB*out\fR are \s-1NULL,\s0 then a new object is allocated and must be freed after use.
.SH "NOTES"
.IX Header "NOTES"
The \s-1ASN1_TIME\s0 structure corresponds to the \s-1ASN.1\s0 structure \fBTime\fR
defined in \s-1RFC5280\s0 et al. The time setting functions obey the rules outlined
in \s-1RFC5280:\s0 if the date can be represented by UTCTime it is used, else
GeneralizedTime is used.
.PP
The \s-1ASN1_TIME, ASN1_UTCTIME\s0 and \s-1ASN1_GENERALIZEDTIME\s0 structures are represented
as an \s-1ASN1_STRING\s0 internally and can be freed up using \fBASN1_STRING_free()\fR.
.PP
The \s-1ASN1_TIME\s0 structure can represent years from 0000 to 9999 but no attempt
is made to correct ancient calendar changes (for example from Julian to
Gregorian calendars).
.PP
\&\s-1ASN1_UTCTIME\s0 is limited to a year range of 1950 through 2049.
.PP
Some applications add offset times directly to a time_t value and pass the
results to \fBASN1_TIME_set()\fR (or equivalent). This can cause problems as the
time_t value can overflow on some systems resulting in unexpected results.
New applications should use \fBASN1_TIME_adj()\fR instead and pass the offset value
in the \fBoffset_sec\fR and \fBoffset_day\fR parameters instead of directly
manipulating a time_t value.
.PP
\&\fBASN1_TIME_adj()\fR may change the type from \s-1ASN1_GENERALIZEDTIME\s0 to \s-1ASN1_UTCTIME,\s0
or vice versa, based on the resulting year. The \fBASN1_GENERALIZEDTIME_adj()\fR and
\&\fBASN1_UTCTIME_adj()\fR functions will not modify the type of the return structure.
.PP
It is recommended that functions starting with \s-1ASN1_TIME\s0 be used instead of
those starting with \s-1ASN1_UTCTIME\s0 or \s-1ASN1_GENERALIZEDTIME.\s0 The functions
starting with \s-1ASN1_UTCTIME\s0 and \s-1ASN1_GENERALIZEDTIME\s0 act only on that specific
time format. The functions starting with \s-1ASN1_TIME\s0 will operate on either
format.
.SH "BUGS"
.IX Header "BUGS"
\&\fBASN1_TIME_print()\fR, \fBASN1_UTCTIME_print()\fR and \fBASN1_GENERALIZEDTIME_print()\fR
do not print out the timezone: it either prints out \*(L"\s-1GMT\*(R"\s0 or nothing. But all
certificates complying with \s-1RFC5280\s0 et al use \s-1GMT\s0 anyway.
.PP
Use the \fBASN1_TIME_normalize()\fR function to normalize the time value before
printing to get \s-1GMT\s0 results.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBASN1_TIME_set()\fR, \fBASN1_UTCTIME_set()\fR, \fBASN1_GENERALIZEDTIME_set()\fR, \fBASN1_TIME_adj()\fR,
ASN1_UTCTIME_adj and ASN1_GENERALIZEDTIME_set return a pointer to a time structure
or \s-1NULL\s0 if an error occurred.
.PP
\&\fBASN1_TIME_set_string()\fR, \fBASN1_UTCTIME_set_string()\fR, \fBASN1_GENERALIZEDTIME_set_string()\fR
\&\fBASN1_TIME_set_string_X509()\fR return 1 if the time value is successfully set and 0 otherwise.
.PP
\&\fBASN1_TIME_normalize()\fR returns 1 on success, and 0 on error.
.PP
\&\fBASN1_TIME_check()\fR, ASN1_UTCTIME_check and \fBASN1_GENERALIZEDTIME_check()\fR return 1
if the structure is syntactically correct and 0 otherwise.
.PP
\&\fBASN1_TIME_print()\fR, \fBASN1_UTCTIME_print()\fR and \fBASN1_GENERALIZEDTIME_print()\fR return 1
if the time is successfully printed out and 0 if an error occurred (I/O error or
invalid time format).
.PP
\&\fBASN1_TIME_to_tm()\fR returns 1 if the time is successfully parsed and 0 if an
error occurred (invalid time format).
.PP
\&\fBASN1_TIME_diff()\fR returns 1 for success and 0 for failure. It can fail if the
passed-in time structure has invalid syntax, for example.
.PP
\&\fBASN1_TIME_cmp_time_t()\fR and \fBASN1_UTCTIME_cmp_time_t()\fR return \-1 if \fBs\fR is
before \fBt\fR, 0 if \fBs\fR equals \fBt\fR, or 1 if \fBs\fR is after \fBt\fR. \-2 is returned
on error.
.PP
\&\fBASN1_TIME_compare()\fR returns \-1 if \fBa\fR is before \fBb\fR, 0 if \fBa\fR equals \fBb\fR, or 1 if \fBa\fR is after \fBb\fR. \-2 is returned on error.
.PP
\&\fBASN1_TIME_to_generalizedtime()\fR returns a pointer to
the appropriate time structure on success or \s-1NULL\s0 if an error occurred.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Set a time structure to one hour after the current time and print it out:
.PP
.Vb 2
\& #include <time.h>
\& #include <openssl/asn1.h>
\&
\& ASN1_TIME *tm;
\& time_t t;
\& BIO *b;
\&
\& t = time(NULL);
\& tm = ASN1_TIME_adj(NULL, t, 0, 60 * 60);
\& b = BIO_new_fp(stdout, BIO_NOCLOSE);
\& ASN1_TIME_print(b, tm);
\& ASN1_STRING_free(tm);
\& BIO_free(b);
.Ve
.PP
Determine if one time is later or sooner than the current time:
.PP
.Vb 1
\& int day, sec;
\&
\& if (!ASN1_TIME_diff(&day, &sec, NULL, to))
\&     /* Invalid time format */
\&
\& if (day > 0 || sec > 0)
\&     printf("Later\en");
\& else if (day < 0 || sec < 0)
\&     printf("Sooner\en");
\& else
\&     printf("Same\en");
.Ve
.SH "HISTORY"
.IX Header "HISTORY"
The \fBASN1_TIME_to_tm()\fR function was added in OpenSSL 1.1.1.
The \fBASN1_TIME_set_string_X509()\fR function was added in OpenSSL 1.1.1.
The \fBASN1_TIME_normalize()\fR function was added in OpenSSL 1.1.1.
The \fBASN1_TIME_cmp_time_t()\fR function was added in OpenSSL 1.1.1.
The \fBASN1_TIME_compare()\fR function was added in OpenSSL 1.1.1.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2015\-2020 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.

MR SKB