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SSL_CTX_SET_OPTIONS(3) Library Functions Manual SSL_CTX_SET_OPTIONS(3)

SSL_CTX_set_options, SSL_set_options, SSL_CTX_clear_options, SSL_clear_options, SSL_CTX_get_options, SSL_get_options, SSL_get_secure_renegotiation_support — manipulate SSL options

/* -lssl -lcrypto */
#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);

() adds the options set via bitmask in options to ctx. Options already set before are not cleared!

() adds the options set via bitmask in options to ssl. Options already set before are not cleared!

() clears the options set via bitmask in options to ctx.

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

() returns the options set for ctx.

() returns the options set for ssl.

() indicates whether the peer supports secure renegotiation.

All these functions are implemented using macros.

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 (|).

() 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.

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. () does not affect the settings.

The following options are available:

This currently does nothing.

It is usually safe to use SSL_OP_ALL to enable the bug workaround options if compatibility with somewhat broken implementations is desired.

The following options are available:

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.
Turn on Cookie Exchange as described in RFC 4347 Section 4.2.1. Only affects DTLS connections.
Allow connections to legacy servers that do not support secure renegotiation. This option is not set by default.
Do not use the DTLSv1 protocol. Deprecated; use SSL_CTX_set_min_proto_version(3) instead.
Do not use the DTLSv1.2 protocol. Deprecated; use SSL_CTX_set_min_proto_version(3) instead.
Do not query the MTU. Only affects DTLS connections.
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.
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.

Do not use the TLSv1.0 protocol. Deprecated; use SSL_CTX_set_min_proto_version(3) instead.
Do not use the TLSv1.1 protocol. Deprecated; use SSL_CTX_set_min_proto_version(3) instead.
Do not use the TLSv1.2 protocol. Deprecated; use SSL_CTX_set_max_proto_version(3) instead.

The following options used to be supported at some point in the past and no longer have any effect: 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.

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.

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

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.

OpenBSD-current July 17, 2026 SSL_CTX_SET_OPTIONS(3)