ASN1_TIME_set.3

.\" $OpenBSD: ASN1_TIME_set.3,v 1.23 2024/03/05 18:30:40 tb Exp $
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.Dd $Mdocdate: March 5 2024 $
.Dt ASN1_TIME_SET 3
.Os
.Sh NAME
.Nm ASN1_TIME_set ,
.Nm ASN1_UTCTIME_set ,
.Nm ASN1_GENERALIZEDTIME_set ,
.Nm ASN1_TIME_adj ,
.Nm ASN1_UTCTIME_adj ,
.Nm ASN1_GENERALIZEDTIME_adj ,
.Nm ASN1_TIME_set_string ,
.Nm ASN1_TIME_set_string_X509 ,
.Nm ASN1_UTCTIME_set_string ,
.Nm ASN1_GENERALIZEDTIME_set_string ,
.Nm ASN1_TIME_normalize ,
.Nm ASN1_TIME_check ,
.Nm ASN1_UTCTIME_check ,
.Nm ASN1_GENERALIZEDTIME_check ,
.Nm ASN1_TIME_print ,
.Nm ASN1_UTCTIME_print ,
.Nm ASN1_GENERALIZEDTIME_print ,
.Nm ASN1_TIME_to_tm ,
.Nm ASN1_TIME_diff ,
.Nm ASN1_TIME_cmp_time_t ,
.Nm ASN1_UTCTIME_cmp_time_t ,
.Nm ASN1_TIME_compare ,
.Nm ASN1_TIME_to_generalizedtime ,
.Nm OPENSSL_gmtime ,
.Nm OPENSSL_timegm ,
.Nm OPENSSL_posix_to_tm ,
.Nm OPENSSL_tm_to_posix
.Nd ASN.1 Time functions
.Sh SYNOPSIS
.In openssl/asn1.h
.Ft ASN1_TIME *
.Fo ASN1_TIME_set
.Fa "ASN1_TIME *s"
.Fa "time_t t"
.Fc
.Ft ASN1_UTCTIME *
.Fo ASN1_UTCTIME_set
.Fa "ASN1_UTCTIME *s"
.Fa "time_t t"
.Fc
.Ft ASN1_GENERALIZEDTIME *
.Fo ASN1_GENERALIZEDTIME_set
.Fa "ASN1_GENERALIZEDTIME *s"
.Fa "time_t t"
.Fc
.Ft ASN1_TIME *
.Fo ASN1_TIME_adj
.Fa "ASN1_TIME *s"
.Fa "time_t t"
.Fa "int offset_day"
.Fa "long offset_sec"
.Fc
.Ft ASN1_UTCTIME *
.Fo ASN1_UTCTIME_adj
.Fa "ASN1_UTCTIME *s"
.Fa "time_t t"
.Fa "int offset_day"
.Fa "long offset_sec"
.Fc
.Ft ASN1_GENERALIZEDTIME *
.Fo ASN1_GENERALIZEDTIME_adj
.Fa "ASN1_GENERALIZEDTIME *s"
.Fa "time_t t"
.Fa "int offset_day"
.Fa "long offset_sec"
.Fc
.Ft int
.Fo ASN1_TIME_set_string
.Fa "ASN1_TIME *s"
.Fa "const char *str"
.Fc
.Ft int
.Fo ASN1_TIME_set_string_X509
.Fa "ASN1_TIME *s"
.Fa "const char *str"
.Fc
.Ft int
.Fo ASN1_UTCTIME_set_string
.Fa "ASN1_UTCTIME *s"
.Fa "const char *str"
.Fc
.Ft int
.Fo ASN1_GENERALIZEDTIME_set_string
.Fa "ASN1_GENERALIZEDTIME *s"
.Fa "const char *str"
.Fc
.Ft int
.Fo ASN1_TIME_normalize
.Fa "ASN1_TIME *s"
.Fc
.Ft int
.Fo ASN1_TIME_check
.Fa "const ASN1_TIME *t"
.Fc
.Ft int
.Fo ASN1_UTCTIME_check
.Fa "const ASN1_UTCTIME *t"
.Fc
.Ft int
.Fo ASN1_GENERALIZEDTIME_check
.Fa "const ASN1_GENERALIZEDTIME *t"
.Fc
.Ft int
.Fo ASN1_TIME_print
.Fa "BIO *b"
.Fa "const ASN1_TIME *s"
.Fc
.Ft int
.Fo ASN1_UTCTIME_print
.Fa "BIO *b"
.Fa "const ASN1_UTCTIME *s"
.Fc
.Ft int
.Fo ASN1_GENERALIZEDTIME_print
.Fa "BIO *b"
.Fa "const ASN1_GENERALIZEDTIME *s"
.Fc
.Ft int
.Fo ASN1_TIME_to_tm
.Fa "const ASN1_TIME *s"
.Fa "struct tm *tm"
.Fc
.Ft int
.Fo ASN1_TIME_diff
.Fa "int *pday"
.Fa "int *psec"
.Fa "const ASN1_TIME *from"
.Fa "const ASN1_TIME *to"
.Fc
.Ft int
.Fo ASN1_TIME_cmp_time_t
.Fa "const ASN1_TIME *s"
.Fa "time_t t"
.Fc
.Ft int
.Fo ASN1_UTCTIME_cmp_time_t
.Fa "const ASN1_UTCTIME *s"
.Fa "time_t t"
.Fc
.Ft int
.Fo ASN1_TIME_compare
.Fa "const ASN1_TIME *s"
.Fa "const ASN1_TIME *t"
.Fc
.Ft ASN1_GENERALIZEDTIME *
.Fo ASN1_TIME_to_generalizedtime
.Fa "const ASN1_TIME *t"
.Fa "ASN1_GENERALIZEDTIME **out"
.Fc
.In openssl/crypto.h
.Ft struct tm *
.Fo OPENSSL_gmtime
.Fa "const time_t *time"
.Fa "struct tm *out_tm"
.Fc
.In openssl/posix_time.h
.Ft int
.Fo OPENSSL_timegm
.Fa "const struct tm *tm"
.Fa "time_t *out_time"
.Fc
.Ft int
.Fo OPENSSL_posix_to_tm
.Fa "int64_t time"
.Fa "struct tm *out_tm"
.Fc
.Ft int
.Fo OPENSSL_tm_to_posix
.Fa "struct tm *t_tm"
.Fa "int64_t *out"
.Fc
.Sh DESCRIPTION
An
.Vt ASN1_TIME
object is a shallow wrapper around a string containing an ASN.1
.Vt Time
value in the restricted format valid in X.509 certificates.
An
.Vt ASN1_TIME
object is either an
.Vt ASN1_UTCTIME
object containing a string of the format
.Ar YYMMDDHHMMSS Ns Cm Z
which is valid for the years 1950 to 2049, or an
.Vt ASN1_GENERALIZEDTIME
object containing a string of the format
.Ar YYYYMMDDHHMMSS Ns Cm Z
which is valid for the years 0000 to 1949 and 2050 to 9999.
In both cases, the mandatory suffix
.Sq Cm Z
represents the GMT time zone.
LibreSSL by design does not support the full syntax of ASN.1 times.
In particular, it neither supports fractional seconds
nor any other time zone.
.Pp
The functions
.Fn ASN1_TIME_set ,
.Fn ASN1_UTCTIME_set ,
and
.Fn ASN1_GENERALIZEDTIME_set
set the time object
.Fa s
to the time represented by the
.Vt time_t
value
.Fa t .
If
.Fa s
is
.Dv NULL ,
a new time object is allocated and returned.
.Pp
The functions
.Fn ASN1_TIME_adj ,
.Fn ASN1_UTCTIME_adj ,
and
.Fn ASN1_GENERALIZEDTIME_adj
set the time object
.Fa s
to the time represented by the time
.Fa offset_day
and
.Fa offset_sec
after the
.Vt time_t
value
.Fa t .
The values of
.Fa offset_day
or
.Fa offset_sec
can be negative to set a time before
.Fa t .
The
.Fa offset_sec
value can also exceed the number of seconds in a day.
If
.Fa s
is
.Dv NULL ,
a new time object is allocated and returned.
.Pp
.Fn ASN1_TIME_adj
may change the type from
.Vt ASN1_GENERALIZEDTIME
to
.Vt ASN1_UTCTIME
or vice versa depending on the resulting year.
The functions
.Fn ASN1_UTCTIME_adj
and
.Fn ASN1_GENERALIZEDTIME_adj
do not modify the type of the return object.
.Pp
The functions
.Fn ASN1_TIME_set_string ,
.Fn ASN1_TIME_set_string_X509 ,
.Fn ASN1_UTCTIME_set_string ,
and
.Fn ASN1_GENERALIZEDTIME_set_string
set the time object
.Fa s
to the time string
.Fa str ,
which must be in appropriate ASN.1 time format:
YYMMDDHHMMSSZ for
.Vt ASN1_UTCTIME ,
YYYYMMDDHHMMSSZ for
.Vt ASN1_GENERALIZEDTIME ,
or either of the two for
.Vt ASN1_TIME .
The string
.Fa str
is copied into
.Fa s .
If
.Fa s
is
.Dv NULL ,
these functions only perform a format check on
.Fa str .
.Pp
In LibreSSL,
.Fn ASN1_TIME_set_string
and
.Fn ASN1_TIME_set_string_X509
behave identically and always set the time object
to a valid value to use in an X.509 certificate.
.Fn ASN1_GENERALIZEDTIME_set_string
may encode a time string that is not valid in an X.509 certificate.
.Pp
The function
.Fn ASN1_TIME_normalize
converts an
.Vt ASN1_GENERALIZEDTIME
into a time value that can be used in a certificate
by changing it to an
.Vt ASN1_UTCTIME
if possible.
It has no effect on an
.Vt ASN1_UTCTIME .
.Pp
The functions
.Fn ASN1_TIME_check ,
.Fn ASN1_UTCTIME_check ,
and
.Fn ASN1_GENERALIZEDTIME_check
check the syntax of the time string contained in the object
.Fa s .
.Pp
The functions
.Fn ASN1_TIME_print ,
.Fn ASN1_UTCTIME_print ,
and
.Fn ASN1_GENERALIZEDTIME_print
print out the time
.Fa s
to
.Vt BIO
.Fa b
in human readable format.
It will be of the format MMM DD HH:MM:SS YYYY [GMT], for example "Feb 3
00:55:52 2015 GMT".
It does not include a newline.
If the time string has an invalid format,
it prints out "Bad time value" and returns an error.
.Pp
The function
.Fn ASN1_TIME_to_tm
converts the time
.Fa s
to the standard
.Vt tm
structure.
If
.Fa s
is
.Dv NULL ,
then the current time is converted.
The output time is always in the GMT time zone.
The
.Fa tm_sec , tm_min , tm_hour , tm_mday , tm_mon ,
and
.Fa tm_year
fields of the
.Vt tm
structure are set to the proper values,
whereas all other fields are set to 0.
If
.Fa tm
is
.Dv NULL ,
this function performs a format check on
.Fa s
only.
.Pp
The function
.Fn ASN1_TIME_diff
sets
.Pf * Fa pday
and
.Pf * Fa psec
to the time difference between
.Fa from
and
.Fa to .
If
.Fa to
represents a time later than
.Fa from ,
then one or both (depending on the time difference) of
.Pf * Fa pday
and
.Pf * Fa psec
will be positive.
If
.Fa to
represents a time earlier than
.Fa from ,
then one or both of
.Pf * Fa pday
and
.Pf * Fa psec
will be negative.
If
.Fa to
and
.Fa from
represent the same time, then
.Pf * Fa pday
and
.Pf * Fa psec
will both be zero.
If both
.Pf * Fa pday
and
.Pf * Fa psec
are nonzero, they will always have the same sign.
The value of
.Pf * Fa psec
will always be less than the number of seconds in a day.
If
.Fa from
or
.Fa to
is
.Dv NULL ,
the current time is used.
.Pp
The functions
.Fn ASN1_TIME_cmp_time_t ,
.Fn ASN1_UTCTIME_cmp_time_t ,
and
.Fn ASN1_TIME_compare
compare the two times represented by
.Fa s
and
.Fa t .
.Pp
The function
.Fn ASN1_TIME_to_generalizedtime
converts the
.Vt ASN1_TIME
.Fa t
to an
.Vt ASN1_GENERALIZEDTIME ,
regardless of year.
If either
.Fa out
or
.Pf * Fa out
is
.Dv NULL ,
then a new object is allocated and must be freed after use.
.Pp
The
.Vt ASN1_TIME ,
.Vt ASN1_UTCTIME ,
and
.Vt ASN1_GENERALIZEDTIME
objects are represented as
.Vt ASN1_STRING
objects internally and can be freed using
.Xr ASN1_STRING_free 3 .
.Pp
It is recommended that
.Vt ASN1_TIME
functions be used instead of
.Vt ASN1_UTCTIME
or
.Vt ASN1_GENERALIZEDTIME
functions because the
.Vt ASN1_UTCTIME
and
.Vt ASN1_GENERALIZEDTIME
functions act only on that specific time format, while the
.Vt ASN1_TIME
functions operate on either format.
.Pp
.Fn OPENSSL_gmtime
converts a time_t value in
.Fa time
to a struct tm in
.Fa out_tm
and also returns the struct passed in on success.
.Pp
.Fn OPENSSL_timegm
converts a time structure in UTC time in
.Fa tm
to a time_t value in
.Fa out_time .
.Pp
.Fn OPENSSL_posix_to_tm
converts an
.Vt int64_t
POSIX time value in
.Fa time ,
which must be in the range of year 0 to 9999,
to a broken out time value in
.Fa tm .
.Pp
.Fn OPENSSL_tm_to_posix
converts a time value between the years 0 and 9999 in
.Fa tm
to a POSIX time value in
.Fa out .
.Sh RETURN VALUES
.Fn ASN1_TIME_set ,
.Fn ASN1_UTCTIME_set ,
.Fn ASN1_GENERALIZEDTIME_set ,
.Fn ASN1_TIME_adj ,
.Fn ASN1_UTCTIME_adj ,
.Fn ASN1_GENERALIZEDTIME_adj ,
and
.Fn ASN1_TIME_to_generalizedtime
return a pointer to a time object or
.Dv NULL
if an error occurred.
.Pp
.Fn ASN1_TIME_set_string ,
.Fn ASN1_TIME_set_string_X509 ,
.Fn ASN1_UTCTIME_set_string ,
and
.Fn ASN1_GENERALIZEDTIME_set_string
return 1 if the time value is successfully set or 0 otherwise.
.Pp
.Fn ASN1_TIME_normalize
returns 1 on success or 0 on error.
.Pp
.Fn ASN1_TIME_check ,
.Fn ASN1_UTCTIME_check ,
and
.Fn ASN1_GENERALIZEDTIME_check
return 1 if the time string contained in the object is syntactically
correct or 0 otherwise.
.Pp
.Fn ASN1_TIME_print ,
.Fn ASN1_UTCTIME_print ,
and
.Fn ASN1_GENERALIZEDTIME_print
return 1 if the time is successfully printed or 0 if an error
occurred (I/O error or invalid time format).
.Pp
.Fn ASN1_TIME_to_tm
returns 1 if the time is successfully parsed
or 0 if an error occurred, usually due to an invalid time format.
.Pp
.Fn ASN1_TIME_diff
returns 1 for success or 0 for failure.
It can for example fail if a time string passed in has invalid syntax.
.Pp
.Fn ASN1_TIME_cmp_time_t ,
.Fn ASN1_UTCTIME_cmp_time_t ,
and
.Fn ASN1_TIME_compare
return \-1 if
.Fa s
is earlier than
.Fa t ,
0 if both are equal, 1 if
.Fa s
is later than
.Fa t ,
or \-2 on error.
.Pp
.Fn OPENSSL_timegm
returns 1 for success or 0 for failure.
It can fail if the time is not representable in a time_t,
or falls outside the range allowed in RFC 5280 times.
.Pp
.Fn OPENSSL_gmtime
returns
.Fa out_tm
on success or NULL for failure.
It can fail if the time is not representable in a struct tm,
or falls outside the range allowed in RFC 5280 times.
.Pp
.Fn OPENSSL_posix_to_tm
and
.Fn OPENSSL_tm_to_posix
return 1 for success or 0 on failure.
It is a failure if the year is less than 0 or more than 9999.
.Sh EXAMPLES
Set a time object to one hour after the current time and print it
out:
.Bd -literal -offset indent
#include <time.h>
#include <openssl/asn1.h>

ASN1_TIME *asn1_time;
time_t t;
BIO *b;

t = time(NULL);
asn1_time = ASN1_TIME_adj(NULL, t, 0, 60 * 60);
b = BIO_new_fp(stdout, BIO_NOCLOSE);
if (asn1_time != NULL) {
	ASN1_TIME_print(b, asn1_time);
	BIO_printf(b, "\en");
} else {
	BIO_printf(b, "Time out of range or un-representable\en");
}
ASN1_STRING_free(asn1_time);
BIO_free(b);
.Ed
.Sh SEE ALSO
.Xr ASN1_TIME_new 3 ,
.Xr X509_cmp_time 3
.Sh STANDARDS
The usage of the ASN.1
.Vt Time ,
.Vt UTCTime ,
and
.Vt GeneralizedTime
data types in X.509 certificates is specified in
RFC 5280, Internet X.509 Public Key Infrastructure Certificate and
Certificate Revocation List (CRL) Profile,
section 4.1.2.5 (TBS Certificate Validity).
.Sh HISTORY
.Fn ASN1_UTCTIME_check
and
.Fn ASN1_UTCTIME_print
first appeared in SSLeay 0.5.1.
.Fn ASN1_UTCTIME_set
first appeared in SSLeay 0.6.0.
.Fn ASN1_UTCTIME_set_string
first appeared in SSLeay 0.9.0.
All these functions have been available since
.Ox 2.4 .
.Pp
.Fn ASN1_TIME_set ,
.Fn ASN1_GENERALIZEDTIME_set ,
.Fn ASN1_GENERALIZEDTIME_set_string ,
.Fn ASN1_GENERALIZEDTIME_check ,
.Fn ASN1_TIME_print ,
and
.Fn ASN1_GENERALIZEDTIME_print
first appeared in OpenSSL 0.9.2b and have been available since
.Ox 2.6 .
.Pp
.Fn ASN1_UTCTIME_cmp_time_t
first appeared in OpenSSL 0.9.6 and has been available since
.Ox 2.9 .
.Pp
.Fn ASN1_TIME_check
and
.Fn ASN1_TIME_to_generalizedtime
first appeared in OpenSSL 0.9.7 and have been available since
.Ox 3.2 .
.Pp
.Fn ASN1_TIME_adj ,
.Fn ASN1_UTCTIME_adj ,
.Fn ASN1_GENERALIZEDTIME_adj ,
and
.Fn ASN1_TIME_set_string
first appeared in OpenSSL 1.0.0 and have been available since
.Ox 4.9 .
.Pp
.Fn ASN1_TIME_diff
first appeared in OpenSSL 1.0.2 and have been available since
.Ox 7.1 .
.Pp
.Fn ASN1_TIME_set_string_X509 ,
.Fn ASN1_TIME_normalize ,
.Fn ASN1_TIME_to_tm ,
.Fn ASN1_TIME_cmp_time_t ,
and
.Fn ASN1_TIME_compare
first appeared in OpenSSL 1.1.1 and have been available since
.Ox 7.2 .
.Pp
.Fn OPENSSL_gmtime
first appeared in OpenSSL 0.9.7.
.Fn OPENSSL_timegm ,
.Fn OPENSSL_posix_to_tm ,
and
.Fn OPENSSL_tm_to_posix
first appeared in BoringSSL;
all these functions have been available since
.Ox 7.5 .
.Sh CAVEATS
Some applications add offset times directly to a
.Vt time_t
value and pass the results to
.Fn ASN1_TIME_set
(or equivalent).
This can cause problems as the
.Vt time_t
value can overflow on some systems resulting in unexpected results.
New applications should use
.Fn ASN1_TIME_adj
instead and pass the offset value in the
.Fa offset_sec
and
.Fa offset_day
parameters instead of directly manipulating a
.Vt time_t
value.