SSL_CTX_SET_KEYLOG_CALLBACK(3ossl)

💖 SSL_CTX_set_keylog_callback(3ossl) — like, the OpenSSL page about logging TLS key material 💖

okay so real talk, this is SSL_CTX_set_keylog_callback(3ossl) straight out of the OpenSSL docs, and it's genuinely the whole keylogging crew: SSL_CTX_set_keylog_callback, SSL_CTX_get_keylog_callback, and SSL_CTX_keylog_cb_func. bestie, they all live together, it's giving found family 🫶

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✨ NAME ✨

SSL_CTX_set_keylog_callback, SSL_CTX_get_keylog_callback, SSL_CTX_keylog_cb_func — logging TLS key material 🔑

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🌸 SYNOPSIS 🌸

like, copy-paste this exactly, no cap:

#include <openssl/ssl.h>

typedef void (*SSL_CTX_keylog_cb_func)(const SSL *ssl, const char *line);

void SSL_CTX_set_keylog_callback(SSL_CTX *ctx, SSL_CTX_keylog_cb_func cb);
SSL_CTX_keylog_cb_func SSL_CTX_get_keylog_callback(const SSL_CTX *ctx);

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🦋 DESCRIPTION 🦋

SSL_CTX_set_keylog_callback() sets the TLS key logging callback. she's the main character here 👑 this callback gets called whenever TLS key material is generated or received, and the whole point is so your app can store that keying material for debugging purposes. iykyk 💅

SSL_CTX_get_keylog_callback() retrieves the TLS key logging callback you set earlier. if literally no callback has been set, this returns NULL. and like — when there's no key logging callback at all, or if SSL_CTX_set_keylog_callback gets called with NULL as the value of cb, then no logging of key material will be done. periodt. 🚫

so the key logging callback is called with two items, and yes both matter:

• the ssl object associated with the connection 🫶
• line, a string containing the key material in the format used by NSS for its SSLKEYLOGFILE debugging output

and to recreate that file? the key logging callback should log line, followed by a newline. oh and line will always be a NUL-terminated string, so you're safe, bestie 🧚

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💜 RETURN VALUES 💜

SSL_CTX_get_keylog_callback() returns a pointer to SSL_CTX_keylog_cb_func, or NULL if the callback is not set. that's it, that's the whole vibe check ✅

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🌈 SEE ALSO 🌈

• ssl(7) — go read it, slay

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🎀 COPYRIGHT 🎀

Copyright 2016-2018 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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ngl this one's short and sweet, but the key material in here is literally the keys to the kingdom — keep that logging for debugging, not for the group chat 🙈

okay bye bestie, this was OpenSSL 3.5.0, dated 2026-09-25 — ate, no crumbs 💅✨🍓