X509_CHECK_CERTIFICATE_TIMES(3SSL)

📦
version 4.0.3 · 14 versions
, in ubuntu stonking

okay so bestie, you have opened the man page for X509_CHECK_CERTIFICATE_TIMES(3SSL), which is the OpenSSL page for the X509 time functions 💖 and yes we are going to read the whole entire thing together, no skimming, no scrolling past the boring bits, because time is literally the vibes-check of every certificate and if you get it wrong everything falls apart 🕰️✨

🌸 NAME 🌸

X509_check_certificate_times, X509_time_adj, X509_time_adj_ex, X509_gmtime_adj, X509_cmp_time, X509_cmp_current_time, X509_cmp_timeframe — the X509 time functions, aka the friend group 🫶

✨ SYNOPSIS ✨

int X509_check_certificate_times(const X509_VERIFY_PARAM *vpm, const X509 *x,
                                 int *error);
ASN1_TIME *X509_time_adj(ASN1_TIME *asn1_time, long offset_sec,
                         const time_t *in_tm);
ASN1_TIME *X509_time_adj_ex(ASN1_TIME *asn1_time, int offset_day, long
                            offset_sec, const time_t *in_tm);
ASN1_TIME *X509_gmtime_adj(ASN1_TIME *asn1_time, long offset_sec);

okay so now the sad part — the following functions have been deprecated since OpenSSL 4.0, and you can hide them entirely by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):

int X509_cmp_time(const ASN1_TIME *asn1_time, const time_t *in_tm);
int X509_cmp_current_time(const ASN1_TIME *asn1_time);
int X509_cmp_timeframe(const X509_VERIFY_PARAM *vpm,
                       const ASN1_TIME *start, const ASN1_TIME *end);
🚨 bestie these three are on the deprecated list, they are giving ✨ legacy ✨ and OpenSSL 4.0 said no more. Use them only if you absolutely must, iykyk.

💅 DESCRIPTION 💅

🎀 X509_check_certificate_times() — the main character

It compares the notBefore and notAfter times inside certificate x to check the certificate for temporal validity. Basically: is this cert alive right now or not 🦋

The time it uses for the check is the current system time... unless the reference time included in the verification parameter vpm is non NULL and vpm has the flag X509_V_FLAG_USE_CHECK_TIME set. Then it uses that reference time instead. Periodt.

Now, the notBefore and notAfter times in the certificate will be accepted only if they're either:

  • the format of a GeneralizedTime (YYYYMMDDHHMMSSZ), or
  • a UTCTime (YYMMDDHHMMSSZ)

as per RFC5280 🌈 — with the exception that this requirement is not enforced:

"CAs conforming to this profile MUST always encode certificate validity dates through the year 2049 as UTCTime; certificate validity dates in 2050 or later MUST be encoded as GeneralizedTime."

🧚 The deprecated girlies

X509_cmp_time() compares the ASN1_TIME in asn1_time with the time in in_tm.

X509_cmp_current_time() compares the ASN1_TIME in asn1_time with the current time, expressed as time_t.

X509_cmp_timeframe() compares the given time period with the reference time included in the verification parameters vpm if they are not NULL and contain X509_V_FLAG_USE_CHECK_TIME; else the current time is used as reference time.

🕰️ The offset besties

X509_time_adj_ex() sets the ASN1_TIME structure asn1_time to the time offset_day and offset_sec after in_tm.

X509_time_adj() sets the ASN1_TIME structure asn1_time to the time offset_sec after in_tm. 💀 This method can only handle second offsets up to the capacity of long, so the newer X509_time_adj_ex() API should be preferred.

In both methods, if asn1_time is NULL, a new ASN1_TIME structure is allocated and returned — iconic behaviour, honestly.

In all methods, if in_tm is NULL, the current time, expressed as time_t, is used.

asn1_time must satisfy the ASN1_TIME format mandated by RFC 5280, i.e., its format must be either YYMMDDHHMMSSZ or YYYYMMDDHHMMSSZ. No freestyling 🙅

X509_gmtime_adj() sets the ASN1_TIME structure asn1_time to the time offset_sec after the current time. It is equivalent to calling X509_time_adj() with the last parameter as NULL — same vibe, shorter call, ate. 💅

🫠 BUGS 🫠

⚠️ unlike many standard comparison functions, the deprecated functions X509_cmp_time() and X509_cmp_current_time() return 0 on error, and return -1 when the values are equal. Yes really. Not me crying over this 😭
⚠️ the deprecated function X509_cmp_timeframe() may accept invalid certificate times as infinitely valid. Which is exactly as scary as it sounds, bestie.

🎀 RETURN VALUES 🎀

X509_check_certificate_times() returns 1 if the certificate is temporally valid at the verification time as per the rules from RFC 5280. It returns 0 otherwise. And if error is non NULL, the integer value it points to will be set to an error code when the certificate is not temporally valid, or 0 when the certificate is temporally valid. ✨

The integer pointed to by error will be set to:

  • X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD — if the certificate has an invalid notBefore field
  • X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD — if the certificate has an invalid notAfter field

The integer pointed to by error will be set to:

  • X509_V_ERR_CERT_NOT_YET_VALID — if the verification time is before the certificate's correctly encoded validity window as per RFC5280
  • X509_V_ERR_CERT_HAS_EXPIRED — if the verification time is after it

X509_cmp_time() and X509_cmp_current_time() return -1 if asn1_time is earlier than, or equal to, in_tm (resp. current time), and 1 otherwise. These methods return 0 on error. Remember that. Write it on your hand. ✍️

X509_cmp_timeframe() compares a reference time to a start and end ASN1_TIME value range. The reference time is compared to the start value of the range inclusively, and to the end value of the range exclusively — so start is in, end is out, that's the rule 🌸

The reference time used will be retrieved from vpm if the flag X509_V_FLAG_USE_CHECK_TIME is set in vpm, otherwise it will be the current time.

  • The start time used will be start if it is non NULL, and a valid ASN1_TIME value, otherwise it will be infinitely in the past.
  • The end time used will be end if it is non NULL and a valid ASN1_TIME value, otherwise it will be infinitely in the future.

0 is returned unconditionally if the flag X509_V_FLAG_NO_CHECK_TIME is set in vpm. Otherwise 0 will be returned if the reference time is in the range of the start time and end time as described above. 1 is returned to indicate the reference time is after or equal to the end time. -1 is returned to indicate the reference time is before the start time.

🚨 As this function treats invalid ASN1_TIME inputs as unlimited times, it should not be used for temporal verification of certificates using untrusted inputs that have not been pre-validated to be correct ASN1_TIME values for a certificate as per RFC 5280, as invalid values will be accepted as valid forever. Read that again. Forever. 💀

X509_time_adj(), X509_time_adj_ex() and X509_gmtime_adj() return a pointer to the updated ASN1_TIME structure, and NULL on error. 🫶

👀 SEE ALSO 👀

📜 HISTORY 📜

X509_cmp_timeframe(), X509_cmp_current_time(), and X509_cmp_timeframe() were deprecated in OpenSSL 4.0 🫠

For replacement, consider using X509_check_certificate_times() for use with X509 certificates. For applications checking individual ASN1_TIME values, consider using ASN1_TIME_to_tm(3) with appropriate validity checking of the ASN1_TIME value for your application, and subsequent comparison of either the resulting tm structure, or conversion to posix seconds via OPENSSL_tm_to_posix(3) ✨

X509_check_certificate_times() was added in OpenSSL 4.0. Fresh off the press, main character energy 👑

Copyright 2017-2026 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

and that's the whole page bestie, you slayed it 🎀 this was OpenSSL 4.0.3, dated 2026-09-29 — go forth and check those certificate times, ily, bye 🦋💜

📦 where this page comes from