SSL_CTX_SET_CIPHER_LIST(3ossl)

okay bestie, welcome to the OpenSSL SSL_CTX_SET_CIPHER_LIST(3ossl) page — literally the manual for picking which ciphers get to come to the party 💅✨

✨ NAME ✨

SSL_CTX_set_cipher_list, SSL_set_cipher_list, SSL_CTX_set_ciphersuites, SSL_set_ciphersuites, OSSL_default_cipher_list, OSSL_default_ciphersuites — choose list of available SSL_CIPHERs

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🌸 SYNOPSIS 🌸

#include <openssl/ssl.h>

int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str);
int SSL_set_cipher_list(SSL *ssl, const char *str);

int SSL_CTX_set_ciphersuites(SSL_CTX *ctx, const char *str);
int SSL_set_ciphersuites(SSL *s, const char *str);

const char *OSSL_default_cipher_list(void);
const char *OSSL_default_ciphersuites(void);

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💖 DESCRIPTION 💖

Okay so let's break it down, bestie, because there's a lot going on here 🫶

SSL_CTX_set_cipher_list() sets the list of available ciphers (TLSv1.2 and below) for ctx using the control string str. The format of that string is described in openssl-ciphers(1). And here's the tea: the list of ciphers is inherited by all ssl objects created from ctx — so it's like, generational, passing down the cipher vibes to the whole family 🌈. This function does not impact TLSv1.3 ciphersuites, so if you wanna configure those, use SSL_CTX_set_ciphersuites() instead.

ctx MUST NOT be NULL. No cap. 💀

SSL_set_cipher_list() sets the list of ciphers (TLSv1.2 and below) only for ssl. So it's just for that one connection, not the whole squad.

SSL_CTX_set_ciphersuites() is used to configure the available TLSv1.3 ciphersuites for ctx. This is a simple colon (":") separated list of TLSv1.3 ciphersuite names in order of preference. The valid TLSv1.3 ciphersuite names are:

• TLS_AES_128_GCM_SHA256
• TLS_AES_256_GCM_SHA384
• TLS_CHACHA20_POLY1305_SHA256
• TLS_AES_128_CCM_SHA256
• TLS_AES_128_CCM_8_SHA256
• TLS_SHA384_SHA384 — integrity-only
• TLS_SHA256_SHA256 — integrity-only

An empty list is permissible. The default value for this setting is:

"TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256"

SSL_set_ciphersuites() is the same as SSL_CTX_set_ciphersuites() except it configures the ciphersuites for ssl.

OSSL_default_cipher_list() returns the default cipher string for TLSv1.2 (and earlier) ciphers. OSSL_default_ciphersuites() returns the default cipher string for TLSv1.3 ciphersuites. Defaults are cute, we love a good default 💖

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💅 NOTES 💅

The control string str for SSL_CTX_set_cipher_list(), SSL_set_cipher_list(), SSL_CTX_set_ciphersuites() and SSL_set_ciphersuites() should be universally usable and not depend on details of the library configuration (ciphers compiled in). So no syntax checking takes place — none, zero, zilch. Items that are not recognized, because the corresponding ciphers are not compiled in or because they are mistyped, are simply ignored. Failure is only flagged if no ciphers could be collected at all. So like, if you typo, it just gets silently vibed past and you won't even know 😭

It should be noted that inclusion of a cipher to be used into the list is a necessary condition. On the client side, the inclusion into the list is also sufficient unless the security level excludes it. On the server side, additional restrictions apply. All ciphers have additional requirements. ADH ciphers don't need a certificate, but DH-parameters must have been set. All other ciphers need a corresponding certificate and key.

An RSA cipher can only be chosen when an RSA certificate is available. RSA ciphers using DHE need a certificate and key and additional DH-parameters (see SSL_CTX_set_tmp_dh_callback(3)).

A DSA cipher can only be chosen when a DSA certificate is available. DSA ciphers always use DH key exchange and therefore need DH-parameters (see SSL_CTX_set_tmp_dh_callback(3)).

When these conditions are not met for any cipher in the list (e.g. a client only supports export RSA ciphers with an asymmetric key length of 512 bits and the server is not configured to use temporary RSA keys), the "no shared cipher" (SSL_R_NO_SHARED_CIPHER) error is generated and the handshake will fail. It's giving catastrophic communication breakdown 💀

OSSL_default_cipher_list() and OSSL_default_ciphersuites() replace SSL_DEFAULT_CIPHER_LIST and TLS_DEFAULT_CIPHERSUITES, respectively. The cipher list defines are deprecated as of 3.0. So RIP to those, they're old news now 🙈

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🫶 RETURN VALUES 🫶

• SSL_CTX_set_cipher_list() and SSL_set_cipher_list() return 1 if any cipher could be selected and 0 on complete failure.
• SSL_CTX_set_ciphersuites() and SSL_set_ciphersuites() return 1 if the requested ciphersuite list was configured, and 0 otherwise.

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🔥 SEE ALSO 🔥

ssl(7), SSL_get_ciphers(3), SSL_CTX_use_certificate(3), SSL_CTX_set_tmp_dh_callback(3), openssl-ciphers(1)

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⭐ HISTORY ⭐

OSSL_default_cipher_list() and OSSL_default_ciphersites() are new in 3.0.

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👑 COPYRIGHT 👑

Copyright 2000-2024 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 🫶 this was OpenSSL 3.5.9, dated 2026-09-29 — go forth and configure your ciphers, you absolute icon 👑✨💖