SSL_CTX_SET_OPTIONS(3)

💅 SSL_CTX_SET_OPTIONS — manipulate SSL options 🎀

okay bestie so this is a page from the libssl library manual (the SSL_CTX_SET_OPTIONS(3) one, yes that mouthful 💀) and it's genuinely the glow-up guide for telling the SSL library how to behave. let's get into it ✨

🌸 SYNOPSIS

library “libssl” libcrypto #include <openssl/ssl.h>

long
SSL_CTX_set_options(SSL_CTX *ctx, long options);

long
SSL_set_options(SSL *ssl, long options);

long
SSL_CTX_clear_options(SSL_CTX *ctx, long options);

long
SSL_clear_options(SSL *ssl, long options);

long
SSL_CTX_get_options(SSL_CTX *ctx);

long
SSL_get_options(SSL *ssl);

long
SSL_get_secure_renegotiation_support(SSL *ssl);

like, seven whole functions, all iconic in their own way 👑

🦋 DESCRIPTION

SSL_CTX_set_options() adds the options set via bitmask in options to ctx. and like, note the dramatics: options already set before are not cleared! not me stressing that at you 🙈

SSL_set_options() adds the options set via bitmask in options to ssl. same deal — options already set before are not cleared!

SSL_CTX_clear_options() clears the options set via bitmask in options to ctx. bye felicia 👋

SSL_clear_options() clears the options set via bitmask in options to ssl.

SSL_CTX_get_options() returns the options set for ctx.

SSL_get_options() returns the options set for ssl.

SSL_get_secure_renegotiation_support() indicates whether the peer supports secure renegotiation. a little vibe check on the other end of the connection 🔍

All these functions are implemented using macros. no cap.

The behaviour of the SSL library can be changed by setting several options. The options are coded as bitmasks and can be combined by a bitwise OR operation (|). yes bestie, | is your bestie here 🫶

SSL_CTX_set_options() and SSL_set_options() affect the (external) protocol behaviour of the SSL library. The (internal) behaviour of the API can be changed by using the similar SSL_CTX_set_mode(3) and SSL_set_mode(3) functions. two different departments, ok 💅

During a handshake, the option settings of the SSL object are used. When a new SSL object is created from a context using SSL_new(3), the current option setting is copied. Changes to ctx do not affect already created SSL objects. SSL_clear() does not affect the settings. like, the copy is independent, periodt.

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🎀 the bug workaround options (yes this is a whole category)

• SSL_OP_ALL — This currently does nothing. literally nothing, it's just vibing 💀

It is usually safe to use SSL_OP_ALL to enable the bug workaround options if compatibility with somewhat broken implementations is desired. (broken implementations, not you bestie, never you 💖)

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🔥 the modifying options (the main characters)

• SSL_OP_CIPHER_SERVER_PREFERENCE — When choosing a cipher, use the server's preferences instead of the client preferences. When not set, the server will always follow the client's preferences. When set, the server will choose following its own preferences. server said "i'm the main character here" 👑
• SSL_OP_COOKIE_EXCHANGE — Turn on Cookie Exchange as described in RFC 4347 Section 4.2.1. Only affects DTLS connections.
• SSL_OP_LEGACY_SERVER_CONNECT — Allow connections to legacy servers that do not support secure renegotiation. This option is not set by default.
• SSL_OP_NO_DTLSv1 — Do not use the DTLSv1 protocol. Deprecated; use SSL_CTX_set_min_proto_version(3) instead.
• SSL_OP_NO_DTLSv1_2 — Do not use the DTLSv1.2 protocol. Deprecated; use SSL_CTX_set_min_proto_version(3) instead.
• SSL_OP_NO_QUERY_MTU — Do not query the MTU. Only affects DTLS connections.
• SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION — When performing renegotiation as a server, always start a new session (i.e., session resumption requests are only accepted in the initial handshake). This option is not needed for clients.
• SSL_OP_NO_TICKET — Normally clients and servers using TLSv1.2 and earlier will, where possible, transparently make use of RFC 5077 tickets for stateless session resumption. If this option is set, this functionality is disabled and tickets will not be used by clients or servers. tickets? cancelled. 🎟️🚫
• SSL_OP_NO_TLSv1 — Do not use the TLSv1.0 protocol. Deprecated; use SSL_CTX_set_min_proto_version(3) instead.
• SSL_OP_NO_TLSv1_1 — Do not use the TLSv1.1 protocol. Deprecated; use SSL_CTX_set_min_proto_version(3) instead.
• SSL_OP_NO_TLSv1_2 — Do not use the TLSv1.2 protocol. Deprecated; use SSL_CTX_set_max_proto_version(3) instead. (note: this one's max, not min — careful bestie 👀)

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💀 the "used to be somebody" list

The following options used to be supported at some point in the past and no longer have any effect — they're retired, they're living their best life off the grid, they do nothing:

SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION, SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, SSL_OP_EPHEMERAL_RSA, SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER, SSL_OP_MICROSOFT_SESS_ID_BUG, SSL_OP_NETSCAPE_CA_DN_BUG, SSL_OP_NETSCAPE_CHALLENGE_BUG, SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG, SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG, SSL_OP_NO_COMPRESSION, SSL_OP_NO_SSLv2, SSL_OP_NO_SSLv3, SSL_OP_PKCS1_CHECK_1, SSL_OP_PKCS1_CHECK_2, SSL_OP_SAFARI_ECDHE_ECDSA_BUG, SSL_OP_SINGLE_DH_USE, SSL_OP_SINGLE_ECDH_USE, SSL_OP_SSLEAY_080_CLIENT_DH_BUG, SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG, SSL_OP_TLS_BLOCK_PADDING_BUG, SSL_OP_TLS_D5_BUG, SSL_OP_TLS_ROLLBACK_BUG, SSL_OP_TLSEXT_PADDING.

twenty-three icons, all honorary. 🕯️

⭐ RETURN VALUES

• SSL_CTX_set_options() and SSL_set_options() return the new options bitmask after adding options.
• SSL_CTX_clear_options() and SSL_clear_options() return the new options bitmask after clearing options.
• SSL_CTX_get_options() and SSL_get_options() return the current bitmask.
• SSL_get_secure_renegotiation_support() returns 1 is the peer supports secure renegotiation and 0 if it does not. (yes, "is", that's the original wording, we're keeping it, character for character fr fr 😭)

🌈 SEE ALSO

openssl(1), ssl(3), SSL_clear(3), SSL_CTX_ctrl(3), SSL_CTX_set_min_proto_version(3), SSL_new(3)

like, the whole friend group 💜

👑 HISTORY

SSL_CTX_set_options() and SSL_set_options() first appeared in SSLeay 0.9.0 and have been available since OpenBSD 2.4.

SSL_CTX_get_options() and SSL_get_options() first appeared in OpenSSL 0.9.2b and have been available since OpenBSD 2.6.

SSL_CTX_clear_options(), SSL_clear_options(), and SSL_get_secure_renegotiation_support() first appeared in OpenSSL 0.9.8m and have been available since OpenBSD 4.9.

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okay and that's the page girlypop ✨ this one shipped with the Debian version of the manual, dated July 17, 2026, filed under SSL_CTX_SET_OPTIONS(3). go forth and set your options, bestie — slay responsibly 💅🫶