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ASN1_TIME_SET(3) Library Functions Manual ASN1_TIME_SET(3)

ASN1_TIME_set, ASN1_UTCTIME_set, ASN1_GENERALIZEDTIME_set, ASN1_TIME_adj, ASN1_UTCTIME_adj, ASN1_GENERALIZEDTIME_adj, ASN1_TIME_set_string, ASN1_UTCTIME_set_string, ASN1_GENERALIZEDTIME_set_string, ASN1_TIME_check, ASN1_UTCTIME_check, ASN1_GENERALIZEDTIME_check, ASN1_TIME_print, ASN1_UTCTIME_print, ASN1_GENERALIZEDTIME_print, ASN1_TIME_diff, ASN1_UTCTIME_cmp_time_t, ASN1_TIME_to_generalizedtime — ASN.1 Time functions

#include <openssl/asn1.h>

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_UTCTIME_set_string(ASN1_UTCTIME *s, const char *str);

int
ASN1_GENERALIZEDTIME_set_string(ASN1_GENERALIZEDTIME *s, const char *str);

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_diff(int *pday, int *psec, const ASN1_TIME *from, const ASN1_TIME *to);

int
ASN1_UTCTIME_cmp_time_t(const ASN1_UTCTIME *s, time_t t);

ASN1_GENERALIZEDTIME *
ASN1_TIME_to_generalizedtime(const ASN1_TIME *t, ASN1_GENERALIZEDTIME **out);

The functions (), (), and () set the time structure s to the time represented by the time_t value t. If s is NULL, a new time structure is allocated and returned.

The functions (), (), and () set the 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 time structure is allocated and returned.

() may change the type from ASN1_GENERALIZEDTIME to ASN1_UTCTIME or vice versa depending on the resulting year. The functions () and () do not modify the type of the return structure.

The functions (), (), and () set the time structure s to the time represented by the string str, which must be in appropriate ASN.1 time format (for example YYMMDDHHMMSSZ or YYYYMMDDHHMMSSZ). The string str is copied into s. If s is NULL, these functions only perform a format check on str.

The functions (), (), and () check the syntax of the time structure s.

The functions (), (), and () print 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 an invalid format, it prints out "Bad time value" and returns an error. The output of ASN1_GENERALIZEDTIME_print() may include a fractional part following the second.

The function () 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 nonzero, 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.

The function () compares the two times represented by s and t.

The function () converts the ASN1_TIME t to an ASN1_GENERALIZEDTIME, regardless of year. If either out or *out is NULL, then a new object is allocated and must be freed after use.

The ASN1_TIME structure corresponds to the ASN.1 structure defined in RFC 5280 et al. The time setting functions obey the rules outlined in RFC 5280: if the date can be represented by UTCTime it is used, otherwise GeneralizedTime is used.

The ASN1_TIME, ASN1_UTCTIME, and ASN1_GENERALIZEDTIME structures are represented as ASN1_STRING structures internally and can be freed using ASN1_STRING_free(3).

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).

ASN1_UTCTIME is limited to a year range of 1950 through 2049.

It is recommended that ASN1_TIME functions be used instead of ASN1_UTCTIME or ASN1_GENERALIZEDTIME functions because the ASN1_UTCTIME and ASN1_GENERALIZEDTIME functions act only on that specific time format, while the ASN1_TIME functions operate on either format.

ASN1_TIME_set(), ASN1_UTCTIME_set(), ASN1_GENERALIZEDTIME_set(), ASN1_TIME_adj(), ASN1_UTCTIME_adj(), ASN1_GENERALIZEDTIME_adj(), and ASN1_TIME_to_generalizedtime() return a pointer to a time structure or NULL if an error occurred.

ASN1_TIME_set_string(), ASN1_UTCTIME_set_string(), and ASN1_GENERALIZEDTIME_set_string() return 1 if the time value is successfully set or 0 otherwise.

ASN1_TIME_check(), ASN1_UTCTIME_check(), and ASN1_GENERALIZEDTIME_check() return 1 if the time structure is syntactically correct or 0 otherwise.

ASN1_TIME_print(), ASN1_UTCTIME_print(), and ASN1_GENERALIZEDTIME_print() return 1 if the time is successfully printed or 0 if an error occurred (I/O error or invalid time format).

ASN1_TIME_diff() returns 1 for success or 0 for failure. It can for example fail if a time structure passed in has invalid syntax.

ASN1_UTCTIME_cmp_time_t() returns -1 if s is earlier than t, 0 if both are equal, 1 if s is later than t, or -2 on error.

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);

ASN1_TIME_new(3), ASN1_time_parse(3), X509_cmp_time(3)

ASN1_UTCTIME_check() and ASN1_UTCTIME_print() first appeared in SSLeay 0.5.1. ASN1_UTCTIME_set() first appeared in SSLeay 0.6.0. ASN1_UTCTIME_set_string() first appeared in SSLeay 0.9.0. All these functions have been available since OpenBSD 2.4.

ASN1_TIME_set(), ASN1_GENERALIZEDTIME_set(), ASN1_GENERALIZEDTIME_set_string(), ASN1_GENERALIZEDTIME_check(), ASN1_TIME_print(), and ASN1_GENERALIZEDTIME_print() first appeared in OpenSSL 0.9.2b and have been available since OpenBSD 2.6.

ASN1_UTCTIME_cmp_time_t() first appeared in OpenSSL 0.9.6 and has been available since OpenBSD 2.9.

ASN1_TIME_check() and ASN1_TIME_to_generalizedtime() first appeared in OpenSSL 0.9.7 and have been available since OpenBSD 3.2.

ASN1_TIME_adj(), ASN1_UTCTIME_adj(), ASN1_GENERALIZEDTIME_adj(), and ASN1_TIME_set_string() first appeared in OpenSSL 1.0.0 and have been available since OpenBSD 4.9.

ASN1_TIME_diff() first appeared in OpenSSL 1.0.2 and have been available since OpenBSD 7.1.

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.

ASN1_TIME_print(), ASN1_UTCTIME_print(), and ASN1_GENERALIZEDTIME_print() do not print the time zone: they either print "GMT" or nothing. But all certificates complying with RFC 5280 et al use GMT anyway.

March 31, 2022 OpenBSD-7.2