SSL_CTX_SET_SECURITY_LEVEL(3ossl)

📦

version 15.1 · 3 versions

15.1 · freebsd 15.1 (latest)
14.5 · freebsd 14.5
nixpkgs unstable

💅 SSL_CTX_SET_SECURITY_LEVEL 💅

okay so this is the OpenSSL manual page for the SSL/TLS security framework — yes, the whole vibe-check system for how much crypto paranoia you're running with. Bestie, it's a lot of getters and setters, but it's genuinely iconic once you get it. iykyk 🎀

✨ NAME ✨

SSL_CTX_set_security_level, SSL_set_security_level, SSL_CTX_get_security_level, SSL_get_security_level, SSL_CTX_set_security_callback, SSL_set_security_callback, SSL_CTX_get_security_callback, SSL_get_security_callback, SSL_CTX_set0_security_ex_data, SSL_set0_security_ex_data, SSL_CTX_get0_security_ex_data, SSL_get0_security_ex_data — literally the SSL/TLS security framework, the whole squad 🫶

🌸 SYNOPSIS 🌸

#include <openssl/ssl.h>

void SSL_CTX_set_security_level(SSL_CTX *ctx, int level);
void SSL_set_security_level(SSL *s, int level);

int SSL_CTX_get_security_level(const SSL_CTX *ctx);
int SSL_get_security_level(const SSL *s);

void SSL_CTX_set_security_callback(SSL_CTX *ctx,
                                   int (*cb)(SSL *s, SSL_CTX *ctx, int op,
                                             int bits, int nid,
                                             void *other, void *ex));

void SSL_set_security_callback(SSL *s, int (*cb)(SSL *s, SSL_CTX *ctx, int op,
                                                 int bits, int nid,
                                                 void *other, void *ex));

int (*SSL_CTX_get_security_callback(const SSL_CTX *ctx))(SSL *s, SSL_CTX *ctx, int op,
                                                         int bits, int nid, void *other,
                                                         void *ex);
int (*SSL_get_security_callback(const SSL *s))(SSL *s, SSL_CTX *ctx, int op,
                                               int bits, int nid, void *other,
                                               void *ex);

void SSL_CTX_set0_security_ex_data(SSL_CTX *ctx, void *ex);
void SSL_set0_security_ex_data(SSL *s, void *ex);

void *SSL_CTX_get0_security_ex_data(const SSL_CTX *ctx);
void *SSL_get0_security_ex_data(const SSL *s);

like, yes, those return types on the get_security_callback girlies are unhinged to look at. she's giving "function returning a function pointer" main character energy 😭 but it's exactly what it looks like, no cap.

🦋 DESCRIPTION 🦋

SSL_CTX_set_security_level() and SSL_set_security_level() set the security level to level. if you never set one, the library's default security level is what you get — no notes, that's just how she rolls ✨

SSL_CTX_get_security_level() and SSL_get_security_level() retrieve the current security level. casual little peek, love that for you 💅

SSL_CTX_set_security_callback(), SSL_set_security_callback(), SSL_CTX_get_security_callback() and SSL_get_security_callback() get or set the security callback associated with ctx or s. if you don't set one, a default security callback is used. what the parameters mean and what the default callbacks do is described below, so keep reading bestie 👑

SSL_CTX_set0_security_ex_data(), SSL_set0_security_ex_data(), SSL_CTX_get0_security_ex_data() and SSL_get0_security_ex_data() set the extra data pointer passed to the ex parameter of the callback. this value is passed to the callback verbatim and can be set to any convenient application specific value — literally whatever your app finds cute 🍓

🌈 DEFAULT CALLBACK BEHAVIOUR 🌈

if an application doesn't set its own security callback, the default callback is used. it's intended to provide sane defaults. the meaning of each level is described below — and omg there are six of them, buckle up 🧚

⭐ Level 0

everything is permitted. this retains compatibility with previous versions of OpenSSL. it's the "no thoughts, head empty" setting 💀

⭐ Level 1

the security level corresponds to a minimum of 80 bits of security. any parameters offering below 80 bits of security are excluded. as a result RSA, DSA and DH keys shorter than 1024 bits and ECC keys shorter than 160 bits are prohibited. any cipher suite using MD5 for the MAC is also prohibited. any cipher suites using CCM with a 64 bit authentication tag are prohibited. note that signatures using SHA1 and MD5 are also forbidden at this level as they have less than 80 security bits. additionally, SSLv3, TLS 1.0, TLS 1.1 and DTLS 1.0 are all disabled at this level. she said no to the old protocols 🚫

⭐ Level 2

security level set to 112 bits of security. as a result RSA, DSA and DH keys shorter than 2048 bits and ECC keys shorter than 224 bits are prohibited. in addition to the level 1 exclusions any cipher suite using RC4 is also prohibited. compression is disabled. rip compression, you had a good run 🙈

⭐ Level 3

security level set to 128 bits of security. as a result RSA, DSA and DH keys shorter than 3072 bits and ECC keys shorter than 256 bits are prohibited. in addition to the level 2 exclusions cipher suites not offering forward secrecy are prohibited. session tickets are disabled. forward secrecy or nothing 🔥

⭐ Level 4

security level set to 192 bits of security. as a result RSA, DSA and DH keys shorter than 7680 bits and ECC keys shorter than 384 bits are prohibited. cipher suites using SHA1 for the MAC are prohibited. SHA1 girlies, your era is over 💅

⭐ Level 5

security level set to 256 bits of security. as a result RSA, DSA and DH keys shorter than 15360 bits and ECC keys shorter than 512 bits are prohibited. level 5 is highkey the final boss 👑

🎀 APPLICATION DEFINED SECURITY CALLBACKS 🎀

Documentation to be provided.

(not me telling you the manpage literally says that 😭 that's the whole section, verbatim, she's a mystery, an enigma, a placeholder.)

👑 NOTES 👑

the default security level can be configured when OpenSSL is compiled by setting -DOPENSSL_TLS_SECURITY_LEVEL=level. if not set then 2 is used. remember that number, it's your factory setting 🫶

the security framework disables or reject parameters inconsistent with the set security level. in the past this was difficult as applications had to set a number of distinct parameters (supported ciphers, supported curves supported signature algorithms) to achieve this end and some cases (DH parameter size for example) could not be checked at all. honestly, the struggle was real 😭

by setting an appropriate security level much of this complexity can be avoided. slay, less work for you ✨

the bits of security limits affect all relevant parameters including cipher suite encryption algorithms, supported ECC curves, supported signature algorithms, DH parameter sizes, certificate key sizes and signature algorithms. this limit applies no matter what other custom settings an application has set: so if the cipher suite is set to ALL then only cipher suites consistent with the security level are permissible. like, ALL does not mean all, bestie, it means "all the ones that pass the vibe check" 💀

see SP800-57 for how the security limits are related to individual algorithms.

some security levels require large key sizes for non-ECC public key algorithms which can severely degrade performance. for example 256 bits of security requires the use of RSA keys of at least 15360 bits in size. your CPU will simply pass away 🫠

some restrictions can be gracefully handled: for example cipher suites offering insufficient security are not sent by the client and will not be selected by the server. other restrictions such as the peer certificate key size or the DH parameter size will abort the handshake with a fatal alert. yeah, that one's a full on crash-out 💀

attempts to set certificates or parameters with insufficient security are also blocked. for example trying to set a certificate using a 512 bit RSA key or a certificate with a signature with SHA1 digest at level 1 using SSL_CTX_use_certificate(). applications which do not check the return values for errors will misbehave: for example it might appear that a certificate is not set at all because it had been rejected.

⚠️ ok this is the important one: check your return values, fr fr. if you ignore them your app will ghost you and act like the cert was never set, and you'll be debugging for hours like ??? 🙈

💖 RETURN VALUES 💖

SSL_CTX_set_security_level() and SSL_set_security_level() do not return values. they simply are.
SSL_CTX_get_security_level() and SSL_get_security_level() return a integer that represents the security level with SSL_CTX or SSL, respectively.
SSL_CTX_set_security_callback() and SSL_set_security_callback() do not return values.
SSL_CTX_get_security_callback() and SSL_get_security_callback() return the pointer to the security callback or NULL if the callback is not set.
SSL_CTX_get0_security_ex_data() and SSL_get0_security_ex_data() return the extra data pointer or NULL if the ex data is not set.

🌸 SEE ALSO 🌸

ssl(7) — go read it, bestie, it's the lore 🦋

⭐ HISTORY ⭐

these functions were added in OpenSSL 1.1.0. vintage 💅

🍓 COPYRIGHT 🍓

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>.

and that's the whole page, bestie 🧚✨ this was OpenSSL 3.5.6, dated 2026-04-07, page SSL_CTX_SET_SECURITY_LEVEL(3ossl) — go forth and set your security levels responsibly, mwah 💜

📦 where this page comes from

freebsd 15.1: base 15.1
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms