SSL_GET_SESSION(3)

💅 NAME 💅

SSL_get_session, SSL_get0_session, SSL_get1_session — bestie, these are the three lil functions that grab you the TLS/SSL session data, and honestly? they're giving "keys to the castle" 🔑

So this page is from the Library Functions Manual (libssl girlies, we love you), and it's all about pulling the SSL_SESSION out of a connection. Let's get into it ✨

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🌸 SYNOPSIS 🌸

library “libssl” libcrypto

#include <openssl/ssl.h>

SSL_SESSION *
SSL_get_session(const SSL *ssl);

SSL_SESSION *
SSL_get0_session(const SSL *ssl);

SSL_SESSION *
SSL_get1_session(SSL *ssl);

Three functions, one header, no cap 💖

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🦋 DESCRIPTION 🦋

✨ the basics, bestie ✨

• SSL_get_session() — hands you a pointer to the SSL_SESSION that's actually used in ssl. But heads up: the reference count of that SSL_SESSION is not incremented, so like… that pointer can literally become invalid because of other operations. It's giving "borrowed, not yours" 🙈
• SSL_get0_session() — same as SSL_get_session(). Literally twins. Same energy 👯
• SSL_get1_session() — also same as SSL_get_session(), except the reference count of the SSL_SESSION is incremented by one. Now it's actually yours to keep 🔥

And what even is this ssl session, you ask? It contains all the information required to re-establish the connection without a new handshake. That's the whole vibe: no renegotiation, just reconnection. Iconic 🎀

🧚 the pointer lore (read this part fr) 🧚

SSL_get0_session() returns a pointer to the actual session. Since the reference counter is not incremented, that pointer is only valid while the connection is in use. That's the fine print, and I need you to respect it.

So if SSL_clear(3) or SSL_free(3) gets called, the session may be removed completely (if it's considered bad), and the pointer you got will become invalid. Poof. Gone. 💀

And even if the session is valid, it can be removed at any time due to a timeout during SSL_CTX_flush_sessions(3). Like, the session doesn't even have to do anything wrong. Rude, but that's the rules 😭

👑 keeping your data 👑

If the data is to be kept, SSL_get1_session() will increment the reference count, so the session will not be implicitly removed by other operations — it just stays in memory, chilling. 🫶

But then to actually remove it, SSL_SESSION_free(3) must be explicitly called once, to decrement the reference count again. Ball's in your court, bestie. You gotta clean up after yourself 💅

🚨 the one-SSL_CTX rule (this is important) 🚨

SSL_SESSION objects keep internal link information about the session cache list when being inserted into one SSL_CTX object's session cache.

Which means, and I'm saying this super clearly because it matters:

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).

One session = one context. No sharing. Don't be messy with it 🙅‍♀️

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🌈 RETURN VALUES 🌈

The following return values can occur:

• NULL — There is no session available in ssl. It's giving nothing, because there is nothing 😭
• Pointer to an SSL_SESSION — The return value points to the data of an SSL session. Slay, you got one 💖

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🍓 SEE ALSO 🍓

ssl(3), SSL_clear(3), SSL_free(3), SSL_SESSION_free(3), SSL_SESSION_get0_peer(3), SSL_SESSION_get_compress_id(3), SSL_SESSION_get_id(3), SSL_SESSION_get_protocol_version(3), SSL_SESSION_get_time(3), SSL_SESSION_new(3), SSL_SESSION_print(3), SSL_set_session(3)

That's the whole squad, go read them too ✨

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⭐ HISTORY ⭐

• SSL_get_session() first appeared in SSLeay 0.5.2 and has been available since OpenBSD 2.4. Elder icon behavior 👑
• SSL_get0_session() and SSL_get1_session() first appeared in OpenSSL 0.9.5 and have been available since OpenBSD 2.7. The younger siblings finally arrived 🦋

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okay that's the whole page, bestie!! 💜 This was the Debian build, dated June 8, 2025 — so like, fresh off the press, and yes it says Library Functions Manual up top which is why we're here gossiping about it 🎀 Now go get your session and hold onto that refcount like it's your last iced coffee 🧊💅