SSL_CTX_NEW(3ossl)

✨ SSL_CTX_NEW ✨

okay bestie, this is the OpenSSL manual page for SSL_CTX_NEW(3ossl) and it's literally the origin story of every TLS connection you've ever made 💖. Buckle up, we're making an SSL_CTX.

🎀 NAME 🎀

So there's a whole girl squad of functions in here, and they all do the "make me a new SSL_CTX object as framework for TLS/SSL or DTLS enabled functions" thing:

• TLSv1_2_method, TLSv1_2_server_method, TLSv1_2_client_method
• SSL_CTX_new, SSL_CTX_new_ex, SSL_CTX_up_ref
• SSLv3_method, SSLv3_server_method, SSLv3_client_method
• TLSv1_method, TLSv1_server_method, TLSv1_client_method
• TLSv1_1_method, TLSv1_1_server_method, TLSv1_1_client_method
• TLS_method, TLS_server_method, TLS_client_method
• SSLv23_method, SSLv23_server_method, SSLv23_client_method
• DTLS_method, DTLS_server_method, DTLS_client_method
• DTLSv1_method, DTLSv1_server_method, DTLSv1_client_method
• DTLSv1_2_method, DTLSv1_2_server_method, DTLSv1_2_client_method

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🌸 SYNOPSIS 🌸

#include <openssl/ssl.h>

SSL_CTX *SSL_CTX_new_ex(OSSL_LIB_CTX *libctx, const char *propq,
                        const SSL_METHOD *method);
SSL_CTX *SSL_CTX_new(const SSL_METHOD *method);
int SSL_CTX_up_ref(SSL_CTX *ctx);

const SSL_METHOD *TLS_method(void);
const SSL_METHOD *TLS_server_method(void);
const SSL_METHOD *TLS_client_method(void);

const SSL_METHOD *SSLv23_method(void);
const SSL_METHOD *SSLv23_server_method(void);
const SSL_METHOD *SSLv23_client_method(void);

#ifndef OPENSSL_NO_SSL3_METHOD
const SSL_METHOD *SSLv3_method(void);
const SSL_METHOD *SSLv3_server_method(void);
const SSL_METHOD *SSLv3_client_method(void);
#endif

#ifndef OPENSSL_NO_TLS1_METHOD
const SSL_METHOD *TLSv1_method(void);
const SSL_METHOD *TLSv1_server_method(void);
const SSL_METHOD *TLSv1_client_method(void);
#endif

#ifndef OPENSSL_NO_TLS1_1_METHOD
const SSL_METHOD *TLSv1_1_method(void);
const SSL_METHOD *TLSv1_1_server_method(void);
const SSL_METHOD *TLSv1_1_client_method(void);
#endif

#ifndef OPENSSL_NO_TLS1_2_METHOD
const SSL_METHOD *TLSv1_2_method(void);
const SSL_METHOD *TLSv1_2_server_method(void);
const SSL_METHOD *TLSv1_2_client_method(void);
#endif

const SSL_METHOD *DTLS_method(void);
const SSL_METHOD *DTLS_server_method(void);
const SSL_METHOD *DTLS_client_method(void);

#ifndef OPENSSL_NO_DTLS1_METHOD
const SSL_METHOD *DTLSv1_method(void);
const SSL_METHOD *DTLSv1_server_method(void);
const SSL_METHOD *DTLSv1_client_method(void);
#endif

#ifndef OPENSSL_NO_DTLS1_2_METHOD
const SSL_METHOD *DTLSv1_2_method(void);
const SSL_METHOD *DTLSv1_2_server_method(void);
const SSL_METHOD *DTLSv1_2_client_method(void);
#endif

---

🦋 DESCRIPTION 🦋

SSL_CTX_new_ex() creates a new SSL_CTX object, and this lil guy holds various configuration and data relevant to SSL/TLS or DTLS session establishment. All of that gets inherited later by the SSL object that represents an actual active session. The method parameter is the vibe-setter: it says whether this context is for the client side, the server side, or both — deets in "NOTES" below, bestie 👇.

The library context libctx (peep OSSL_LIB_CTX(3)) is what provides the cryptographic algorithms needed for the session. Any cryptographic algorithms used by any SSL objects created from this SSL_CTX get fetched from libctx using the property query string propq (see "ALGORITHM FETCHING" in crypto(7)). Either or both of libctx or propq may be NULL, no stress.

SSL_CTX_new() does the exact same thing as SSL_CTX_new_ex(), except it uses the default library context and specifies no property query string. That's it, that's the diff 💅.

An SSL_CTX object is reference counted. Creating one for the first time increments the reference count. Freeing the SSL_CTX (using SSL_CTX_free) decrements it. When the reference count drops to zero, any memory or resources allocated to the SSL_CTX object get freed. And SSL_CTX_up_ref() increments the reference count for an existing SSL_CTX structure. Slay.

⚠️ An SSL_CTX object should not be changed after it is used to create any SSL objects, or from multiple threads concurrently, since the implementation does not provide serialization of access for these cases. Do not do it. I'm watching 👀.

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💜 NOTES 💜

On session establishment, by default, no peer credentials verification is done. You have to explicitly ask for it, typically using SSL_CTX_set_verify(3). And for verifying peer certificates there are a ton of options you can set with various functions like SSL_CTX_load_verify_locations(3) and SSL_CTX_set1_param(3).

The SSL/(D)TLS implementation uses the X509_STORE_CTX_set_default(3) function to prepare checks for X509_PURPOSE_SSL_SERVER on the client side and X509_PURPOSE_SSL_CLIENT on the server side. The X509_VERIFY_PARAM_set_purpose(3) function can be used — also in conjunction with SSL_CTX_get0_param(3) — to override the default purpose of the session.

The SSL_CTX object uses method as the connection method. Three method variants are available, and they're giving:

• a generic method (for either client or server use)
• a server-only method
• a client-only method

The method parameter of SSL_CTX_new_ex() and SSL_CTX_new() can be one of the following:

• TLS_method(), TLS_server_method(), TLS_client_method() — These are the general-purpose, version-flexible SSL/TLS methods ✨. The actual protocol version used will be negotiated to the highest version mutually supported by the client and the server. The supported protocols are SSLv3, TLSv1, TLSv1.1, TLSv1.2 and TLSv1.3. Applications should use these methods, and avoid the version-specific methods described below, which are deprecated. Periodt.
• SSLv23_method(), SSLv23_server_method(), SSLv23_client_method() — These functions do not exist anymore, they have been renamed to TLS_method(), TLS_server_method() and TLS_client_method() respectively. Currently the old function calls are renamed to the corresponding new ones by preprocessor macros, to ensure that existing code which uses the old function names still compiles. However, using the old function names is deprecated and new code should call the new functions instead.
• TLSv1_2_method(), TLSv1_2_server_method(), TLSv1_2_client_method() — A TLS/SSL connection established with these methods will only understand the TLSv1.2 protocol. These methods are deprecated.
• TLSv1_1_method(), TLSv1_1_server_method(), TLSv1_1_client_method() — A TLS/SSL connection established with these methods will only understand the TLSv1.1 protocol. These methods are deprecated.
• TLSv1_method(), TLSv1_server_method(), TLSv1_client_method() — A TLS/SSL connection established with these methods will only understand the TLSv1 protocol. These methods are deprecated.
• SSLv3_method(), SSLv3_server_method(), SSLv3_client_method() — A TLS/SSL connection established with these methods will only understand the SSLv3 protocol. The SSLv3 protocol is deprecated and should not be used.
• DTLS_method(), DTLS_server_method(), DTLS_client_method() — These are the version-flexible DTLS methods 🌈. Currently supported protocols are DTLS 1.0 and DTLS 1.2.
• DTLSv1_2_method(), DTLSv1_2_server_method(), DTLSv1_2_client_method() — These are the version-specific methods for DTLSv1.2. These methods are deprecated.
• DTLSv1_method(), DTLSv1_server_method(), DTLSv1_client_method() — These are the version-specific methods for DTLSv1. These methods are deprecated.

SSL_CTX_new() initializes the list of ciphers, the session cache setting, the callbacks, the keys and certificates and the options to their default values. Fresh start, clean slate, main character energy 👑

TLS_method(), TLS_server_method(), TLS_client_method(), DTLS_method(), DTLS_server_method() and DTLS_client_method() are the version-flexible methods. All other methods only support one specific protocol version. Use the version-flexible methods instead of the version specific methods, bestie, I'm begging 🥺.

If you want to limit the supported protocols for the version flexible methods you can use the SSL_CTX_set_min_proto_version(3), SSL_set_min_proto_version(3), SSL_CTX_set_max_proto_version(3) and SSL_set_max_proto_version(3) functions. Using these functions it's possible to choose e.g. TLS_server_method() and be able to negotiate with all possible clients, but to only allow newer protocols like TLS 1.0, TLS 1.1, TLS 1.2 or TLS 1.3. Iconic behaviour, honestly.

The list of protocols available can also be limited using the SSL_OP_NO_SSLv3, SSL_OP_NO_TLSv1, SSL_OP_NO_TLSv1_1, SSL_OP_NO_TLSv1_3, SSL_OP_NO_TLSv1_2 and SSL_OP_NO_TLSv1_3 options of the SSL_CTX_set_options(3) or SSL_set_options(3) functions, but this approach is not recommended. Clients should avoid creating "holes" in the set of protocols they support. When disabling a protocol, make sure that you also disable either all previous or all subsequent protocol versions. In clients, when a protocol version is disabled without disabling all previous protocol versions, the effect is to also disable all subsequent protocol versions. It's giving domino effect 💀.

🚨 The SSLv3 protocol is deprecated and should generally not be used. Applications should typically use SSL_CTX_set_min_proto_version(3) to set the minimum protocol to at least TLS1_VERSION.

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🌟 RETURN VALUES 🌟

Here's the vibe check on what you might get back:

• NULL — The creation of a new SSL_CTX object failed 😭. Check the error stack to find out the reason.
• Pointer to an SSL_CTX object — The return value points to an allocated SSL_CTX object 🎉.
  • SSL_CTX_up_ref() returns 1 for success and 0 for failure.

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🫶 SEE ALSO 🫶

SSL_CTX_set_options(3), SSL_CTX_free(3), X509_STORE_CTX_set_default(3), SSL_CTX_set_verify(3), SSL_CTX_set1_param(3), SSL_CTX_get0_param(3), SSL_connect(3), SSL_accept(3), SSL_CTX_set_min_proto_version(3), ssl(7), SSL_set_connect_state(3)

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🕰️ HISTORY 🕰️

Let's take a lil walk down memory lane, bestie:

• Support for SSLv2 and the corresponding SSLv2_method(), SSLv2_server_method() and SSLv2_client_method() functions where removed in OpenSSL 1.1.0.
• SSLv23_method(), SSLv23_server_method() and SSLv23_client_method() were deprecated and the preferred TLS_method(), TLS_server_method() and TLS_client_method() functions were added in OpenSSL 1.1.0.
• All version-specific methods were deprecated in OpenSSL 1.1.0.
• SSL_CTX_new_ex() was added in OpenSSL 3.0.

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👑 COPYRIGHT 👑

Copyright 2000-2023 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 version 3.5.9, dated 2026-09-29, brought to you by SSL_CTX_NEW(3ossl) — now go make a context and slay ✨🦋