SSL_SESSION_FREE(3ossl)

💖 SSL_SESSION_FREE(3ossl) — bestie edition, from the ossl manual 💖

okay so welcome to SSL_SESSION_FREE(3ossl), the ossl manual page that’s literally all about creating, freeing, and managing SSL_SESSION structures. No cap, it’s short but every line matters. Grab a strawberry 🍓 and let’s go.

✨ NAME ✨

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

🌸 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);

🦋 DESCRIPTION 🦋

• SSL_SESSION_new() — creates a brand-new SSL_SESSION structure and returns a pointer to it. New session, who dis? ✨
• SSL_SESSION_dup() — creates a new SSL_SESSION structure that is a copy of src. Cute detail: the copy is not owned by any cache that src may have been in. 🎀
• SSL_SESSION_up_ref() — increments the reference count on the given SSL_SESSION structure. It’s giving “keep the vibes alive.” 💅
• 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, if the reference count has reached 0. If session is NULL, nothing is done. No drama, just nothing is done. 🫶

🔥 NOTES 🔥

okay this is the important part, bestie — do not skip the notes. SSL_SESSION objects are 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.

SSL objects may be using the SSL_SESSION object; and the way that a session may be reused means several SSL objects may be using one SSL_SESSION object at the same time. So it is therefore crucial to keep the reference count (usage information) correct and not delete an SSL_SESSION object that is still used, as this may lead to program failures due to dangling pointers. 😭

These failures may also appear delayed, e.g. when an SSL_SESSION object was completely freed as the reference count incorrectly became 0, but it is still referenced in the internal session cache and the cache list is processed during a SSL_CTX_flush_sessions(3) operation. Delayed chaos is still chaos. 💀

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, as this would cause incorrect reference counts and therefore program failures. Periodt. 👑

🎀 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.

💅 SEE ALSO 💅

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

🌈 HISTORY 🌈

The SSL_SESSION_dup() function was added in OpenSSL 1.1.1. Slay, vintage-ish. 🦋

👑 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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That’s the whole page, bestie — from the ossl manual, OpenSSL 3.5.6, dated 2026-04-07 💖✨🫶