SSL_CTX_CTRL(3)

💅 SSL_CTX_CTRL — ok so this is the internal one, bestie

Hi hi! So this is from the Library Functions Manual, and the page is called SSL_CTX_CTRL(3). It's giving "backstage pass you're not really supposed to use" energy, and honestly? Iconic of you to look it up anyway. 🎀

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🌸 NAME

SSL_CTX_ctrl, SSL_CTX_callback_ctrl, SSL_ctrl, SSL_callback_ctrl — the internal handling functions for SSL_CTX and SSL objects 🧚

Like, these are the little gears turning inside the machine. You don't touch the gears. But it's cute that you asked.

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✨ SYNOPSIS

It's from the library “libssl” libcrypto, and you pull it in with:

#include <openssl/ssl.h>

Then the four besties show up like this:

long
SSL_CTX_ctrl(SSL_CTX *ctx, int cmd, long larg, void *parg);

long
SSL_CTX_callback_ctrl(SSL_CTX *, int cmd, void (*fp)());

long
SSL_ctrl(SSL *ssl, int cmd, long larg, void *parg);

long
SSL_callback_ctrl(SSL *, int cmd, void (*fp)());

Look at them. Four little functions. All returning long. All taking a cmd, and then depending on that cmd they also evaluate larg, parg, or fp. Main character energy fr fr. 👑

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🦋 DESCRIPTION

Okay so the SSL_*_ctrl() family of functions is used to manipulate settings of the SSL_CTX and SSL objects. Depending on the command cmd, the arguments larg, parg, or fp are evaluated — so the argument situation changes based on what you asked for. Very "the vibes decide the rules" of them.

⚠️ BIG ONE, bestie: these functions should never be called directly. Not a little. Not once. Not "just to see what happens." 🙈

All the functionalities you actually need are made available via other functions or macros. So the whole point is: go use those, and let these stay behind the curtain, lowkey doing their thing. 💜

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💀 RETURN VALUES

The return values of the SSL*_ctrl() functions depend on the command supplied via the cmd() parameter.

That's it. That's the whole answer. Each cmd has its own deal, so the return value is whatever that command says it is. No blanket promise, no guarantees, no notes. 😭 It's giving "I'll text you back" and then not specifying when.

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🌈 SEE ALSO

The whole extended friend group — go say hi to:

• ssl(3)
• SSL_CTX_add_extra_chain_cert(3)
• SSL_CTX_sess_number(3)
• SSL_CTX_sess_set_cache_size(3)
• SSL_CTX_set_max_cert_list(3)
• SSL_CTX_set_mode(3)
• SSL_CTX_set_options(3)
• SSL_CTX_set_session_cache_mode(3)
• SSL_CTX_set_tlsext_servername_callback(3)
• SSL_CTX_set_tlsext_status_cb(3)
• SSL_CTX_set_tlsext_ticket_key_cb(3)
• SSL_get_server_tmp_key(3)
• SSL_num_renegotiations(3)
• SSL_session_reused(3)
• SSL_set_max_send_fragment(3)

Look at that list. It's long. It's slaying. Every single one of them counts, periodt. 🫶

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⭐ HISTORY

Storytime, gather round:

• SSL_CTX_ctrl() and SSL_ctrl() first appeared in SSLeay 0.8.0 and have been available since OpenBSD 2.4. Ancient. Vintage. OG. 🕰️
• SSL_CTX_callback_ctrl() and SSL_callback_ctrl() first appeared in OpenSSL 0.9.5 and have been available since OpenBSD 2.7. The younger siblings fr fr. 🌱

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🎀 aaaand that's the whole page, bestie! This one came from Debian, dated June 8, 2025, and it's the SSL_CTX_CTRL(3) manual page — so now you know the lore. Don't call these directly, mwah 💅

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