NAME¶
ASN1_TIME_set, ASN1_TIME_adj, ASN1_TIME_check, ASN1_TIME_set_string,
ASN1_TIME_print, ASN1_TIME_diff - ASN.1 Time functions.
SYNOPSIS¶
ASN1_TIME *ASN1_TIME_set(ASN1_TIME *s, time_t t);
ASN1_TIME *ASN1_TIME_adj(ASN1_TIME *s, time_t t,
int offset_day, long offset_sec);
int ASN1_TIME_set_string(ASN1_TIME *s, const char *str);
int ASN1_TIME_check(const ASN1_TIME *t);
int ASN1_TIME_print(BIO *b, const ASN1_TIME *s);
int ASN1_TIME_diff(int *pday, int *psec,
const ASN1_TIME *from, const ASN1_TIME *to);
DESCRIPTION¶
The function
ASN1_TIME_set() sets the ASN1_TIME structure
s to the
time represented by the time_t value
t. If
s is NULL a new
ASN1_TIME structure is allocated and returned.
ASN1_TIME_adj() sets the ASN1_TIME structure
s to the time
represented by the time
offset_day and
offset_sec after the
time_t value
t. The values of
offset_day or
offset_sec
can be negative to set a time before
t. The
offset_sec value can
also exceed the number of seconds in a day. If
s is NULL a new
ASN1_TIME structure is allocated and returned.
ASN1_TIME_set_string() sets ASN1_TIME structure
s to the time
represented by string
str which must be in appropriate ASN.1 time
format (for example YYMMDDHHMMSSZ or YYYYMMDDHHMMSSZ).
ASN1_TIME_check() checks the syntax of ASN1_TIME structure
s.
ASN1_TIME_print() prints out the time
s to BIO
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 structure has invalid format it prints out "Bad time value"
and returns an error.
ASN1_TIME_diff() sets
*pday and
*psec to the time
difference between
from and
to. If
to represents a time
later than
from then one or both (depending on the time difference) of
*pday and
*psec will be positive. If
to represents a time
earlier than
from then one or both of
*pday and
*psec
will be negative. If
to and
from represent the same time then
*pday and
*psec will both be zero. If both
*pday and
*psec are non-zero they will always have the same sign. The value of
*psec will always be less than the number of seconds in a day. If
from or
to is NULL the current time is used.
NOTES¶
The ASN1_TIME structure corresponds to the ASN.1 structure
Time defined
in RFC5280 et al. The time setting functions obey the rules outlined in
RFC5280: if the date can be represented by UTCTime it is used, else
GeneralizedTime is used.
The ASN1_TIME structure is represented as an ASN1_STRING internally and can be
freed up using
ASN1_STRING_free().
The ASN1_TIME 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).
Some applications add offset times directly to a time_t value and pass the
results to
ASN1_TIME_set() (or equivalent). This can cause problems as
the time_t value can overflow on some systems resulting in unexpected results.
New applications should use
ASN1_TIME_adj() instead and pass the offset
value in the
offset_sec and
offset_day parameters instead of
directly manipulating a time_t value.
BUGS¶
ASN1_TIME_print() currently does not print out the time zone: it either
prints out "GMT" or nothing. But all certificates complying with
RFC5280 et al use GMT anyway.
EXAMPLES¶
Set a time structure to one hour after the current time and print it out:
#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);
Determine if one time is later or sooner than the current time:
int day, sec;
if (!ASN1_TIME_diff(&day, &sec, NULL, to))
/* Invalid time format */
if (day > 0 || sec > 0)
printf("Later\n");
else if (day < 0 || sec < 0)
printf("Sooner\n");
else
printf("Same\n");
RETURN VALUES¶
ASN1_TIME_set() and
ASN1_TIME_adj() return a pointer to an
ASN1_TIME structure or NULL if an error occurred.
ASN1_TIME_set_string() returns 1 if the time value is successfully set
and 0 otherwise.
ASN1_TIME_check() returns 1 if the structure is syntactically correct and
0 otherwise.
ASN1_TIME_print() returns 1 if the time is successfully printed out and 0
if an error occurred (I/O error or invalid time format).
ASN1_TIME_diff() returns 1 for sucess and 0 for failure. It can fail if
the pass ASN1_TIME structure has invalid syntax for example.