SSL_SESSION_FREE(3ossl)

💖 SSL_SESSION_FREE — the OpenSSL manual, bestie edition 💖

okay so this is the SSL_SESSION_FREE(3ossl) page from the OpenSSL manual, and it's literally all about creating, freeing and babysitting SSL_SESSION structures. it's giving ✨reference counting✨, and honestly? it's the kind of page that saves your whole program from a tragic little crash era. let's get into it 🫶

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🌸 NAME 🌸

SSL_SESSION_new, SSL_SESSION_dup, SSL_SESSION_up_ref, SSL_SESSION_free — create, free and manage SSL_SESSION structures

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✨ SYNOPSIS ✨

#include <openssl/ssl.h>

SSL_SESSION *SSL_SESSION_new(void);
SSL_SESSION *SSL_SESSION_dup(const SSL_SESSION *src);
int SSL_SESSION_up_ref(SSL_SESSION *ses);
void SSL_SESSION_free(SSL_SESSION *session);

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🦋 DESCRIPTION 🦋

okay so four little functions, four little jobs, and they're all about keeping your sessions alive and well 💅

• SSL_SESSION_new() — makes a brand new SSL_SESSION structure and hands you back a pointer to it. fresh out the box, no cap ✨
• SSL_SESSION_dup() — makes a new SSL_SESSION structure that's a copy of src. and here's the tea: the copy is not owned by any cache that src may have been in. so like, it's a fresh independent babe, no cache drama attached 🎀
• SSL_SESSION_up_ref() — bumps the reference count up on the given SSL_SESSION structure. one more friend holding hands with it 🫶
• SSL_SESSION_free() — decrements the reference count of session, and removes the SSL_SESSION structure pointed to by session and frees up the allocated memory — but only if the reference count has reached 0. and if session is NULL? nothing happens. literally nothing. it's fine. it's chill 💜

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💀 NOTES 💀

okay bestie, this is the part where you pay attention, because this is the part that decides whether your program slays or absolutely falls apart 😭

SSL_SESSION objects get allocated when a TLS/SSL handshake operation is successfully completed. depending on the settings — see SSL_CTX_set_session_cache_mode(3) — the SSL_SESSION objects are internally referenced by the SSL_CTX and linked into its session cache.

and SSL objects may be using the SSL_SESSION object. because a session may be reused, several SSL objects may be using one SSL_SESSION object at the same time. so it is crucial to keep the reference count (that's the usage info, iykyk) correct, and to not delete an SSL_SESSION object that's still in use — because that may lead to program failures due to dangling pointers 💀

and here's the sneaky part: these failures may also appear delayed. like, e.g. when an SSL_SESSION object was completely freed because the reference count incorrectly became 0, but it's still referenced in the internal session cache and the cache list is processed during an SSL_CTX_flush_sessions(3) operation. so it's not even a "you'll know right away" situation, it's a "your bug is lurking in the group chat ready to expose you later" situation 🙈

⚠️ SSL_SESSION_free() must only be called for SSL_SESSION objects for which the reference count was explicitly incremented (e.g. by calling SSL_get1_session(), see SSL_get_session(3)), or when the SSL_SESSION object was generated outside a TLS handshake operation, e.g. by using d2i_SSL_SESSION(3). it must not be called on other SSL_SESSION objects, because that would cause incorrect reference counts and therefore program failures. so like... don't do that. periodt.

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⭐ RETURN VALUES ⭐

• SSL_SESSION_new returns a pointer to the newly allocated SSL_SESSION structure, or NULL on error 😭
• SSL_SESSION_dup returns a pointer to the new copy, or NULL on error 😭
• SSL_SESSION_up_ref returns 1 on success, or 0 on error 👑

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🌈 SEE ALSO 🌈

ssl(7), SSL_get_session(3), SSL_CTX_set_session_cache_mode(3), SSL_CTX_flush_sessions(3), d2i_SSL_SESSION(3)

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🎀 HISTORY 🎀

the SSL_SESSION_dup() function was added in OpenSSL 1.1.1. a little icon was born ✨

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👑 COPYRIGHT 👑

Copyright 2000-2023 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>.

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and that's the whole page bestie, no crumbs left 🍓 this was OpenSSL version 3.5.9, dated 2026-09-29, and it ate fr fr. now go fix your reference counts 💅💖