SSL_CTX_SET_MAX_CERT_LIST(3SSL)

💖 SSL_CTX_SET_MAX_CERT_LIST 💖

okay bestie, this is the OpenSSL page for SSL_CTX_set_max_cert_list, SSL_CTX_get_max_cert_list, SSL_set_max_cert_list, and SSL_get_max_cert_list — aka the ✨manipulate allowed size for the peer's certificate chain✨ squad. yes it's three-SSL-manual-page energy, we love her, she's giving TLS gatekeeper. 🎀

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🌸 NAME 🌸

SSL_CTX_set_max_cert_list, SSL_CTX_get_max_cert_list, SSL_set_max_cert_list, SSL_get_max_cert_list — manipulate allowed size for the peer's certificate chain 💅

✨ SYNOPSIS ✨

#include <openssl/ssl.h>

long SSL_CTX_set_max_cert_list(SSL_CTX *ctx, long size);
long SSL_CTX_get_max_cert_list(SSL_CTX *ctx);

long SSL_set_max_cert_list(SSL *ssl, long size);
long SSL_get_max_cert_list(SSL *ctx);

not me typing out all four signatures fr fr 😭 copy them exactly bestie, they are NOT to be edited, periodt.

🦋 DESCRIPTION 🦋

• SSL_CTX_set_max_cert_list() — sets the max size allowed for the peer's certificate chain, for all the SSL objects created from ctx, to be size bytes. and the way that those SSL objects inherit the setting? they inherit whatever was valid for ctx at the time SSL_new(3) got called. iconic behavior tbh. 👑
• SSL_CTX_get_max_cert_list() — returns the currently set max size for ctx. lowkey just reading the vibes back to you. 🌈
• SSL_set_max_cert_list() — sets the max size allowed for the peer's certificate chain for ssl to be size bytes. this setting stays valid until a new value is set, she's loyal like that. 💖
• SSL_get_max_cert_list() — returns the currently set max size for ssl. simple, clean, slay. ✨

💜 NOTES 💜

so during the handshake process, the peer may send a certificate chain. and the TLS/SSL standard? bestie, it does not give any maximum size of the certificate chain. nope. nothing. 💀

the OpenSSL library handles incoming data by a dynamically allocated buffer. and in order to prevent this buffer from growing without bounds due to data received from a faulty or malicious peer, a maximum size for the certificate chain is set. it's giving security guard at the club. 🫶

the default value for the maximum certificate chain size is 100kB (30kB on the 16-bit DOS platform — yes, that's real, that's a thing). this should be sufficient for usual certificate chains (OpenSSL's default maximum chain length is 10, see SSL_CTX_set_verify(3), and certificates without special extensions have a typical size of 1-2kB). math checks out, we ate. 🔥

for special applications it can be necessary to extend the maximum certificate chain size allowed to be sent by the peer, see e.g. the work on "Internet X.509 Public Key Infrastructure Proxy Certificate Profile" and "TLS Delegation Protocol" at http://www.ietf.org/ and http://www.globus.org/ . extra reading bestie, go off. 📚

under normal conditions it should never be necessary to set a value smaller than the default, as the buffer is handled dynamically and only uses the memory actually required by the data sent by the peer. so like... don't? 🙈

⚠️ if the maximum certificate chain size allowed is exceeded, the handshake will fail with an SSL_R_EXCESSIVE_MESSAGE_SIZE error. not cute, not the vibe, avoid. 😭

⭐ RETURN VALUES ⭐

• SSL_CTX_set_max_cert_list() and SSL_set_max_cert_list() return the previously set value (yes, the old one, the throwback 👑).
• SSL_CTX_get_max_cert_list() and SSL_get_max_cert_list() return the currently set value.

🌺 SEE ALSO 🌺

• ssl(7)
• SSL_new(3)
• SSL_CTX_set_verify(3)

🎀 COPYRIGHT 🎀

Copyright 2001-2020 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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and that's the whole page bestie, no cap, every flag and fact accounted for 🫶

version 4.0.3 · dated 2026-09-29 · SSL_CTX_SET_MAX_CERT_LIST(3SSL) — mwah, take care of your cert chain lengths, ily, bye 💅✨