SSL_SET_SESSION(3)

📦 version 4.4.0, in alpine 3.24, arch rolling

💖 SSL_SET_SESSION(3) 💖

okay bestie, so this one lives in the Library Functions Manual and it's part of the libssl / libcrypto fam — yes, the crypto girlies. Let's get into it ✨

🌸 SYNOPSIS 🌸

library “libssl” libcrypto #include <openssl/ssl.h>

int
SSL_set_session(SSL *ssl, SSL_SESSION *session);

🎀 DESCRIPTION 🎀

So SSL_set_session() sets session to be used when the TLS/SSL connection is about to be established. That's it, that's the vibe. 🫶

Heads up though: SSL_set_session() is only useful for TLS/SSL clients. Server girlies, this one's not for you 💅

When the session is set, the reference count of session gets incremented by 1. Iconic. But if the session is not reused, that reference count gets decremented again during SSL_connect(). And if you're sitting there like "wait, was it even reused??" — you can query that with the SSL_session_reused(3) call. iykyk 😌

Now, if there's already a session set inside ssl — like, because it was set with SSL_set_session() before, or because the same ssl was already used for a connection — then SSL_SESSION_free(3) will be called for that session. Old session, your time is up 🫡

⚠️ BIG important warning, fr fr: SSL_SESSION objects keep internal link information about the session cache list when they get inserted into one SSL_CTX object's session cache. So one SSL_SESSION object — regardless of its reference count — must therefore only be used with one SSL_CTX object (and the SSL objects created from this SSL_CTX object). No sharing, no passing it around like a friendship bracelet. It's giving exclusive relationship 🔥

✨ RETURN VALUES ✨

These are the return values that can occur, bestie:

  • 0 — the operation failed 😭 check the error stack to find out the reason.
  • 1 — the operation succeeded 👑 slay.

🦋 SEE ALSO 🦋

go read those, they're literally the supporting cast 💜

🌈 HISTORY 🌈

SSL_set_session() first appeared in SSLeay 0.5.2 and has been available since OpenBSD 2.4. a true elder, we stan an OG 🧚

aaaand that's the whole page! this lil gem came from the Debian edition, dated June 8, 2025 — mwah, bye bestie 💅🎀

📦 where this page comes from