SSL_CTX_SET_OPTIONS(3)

NAME
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

SYNOPSIS
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);

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

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

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

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.

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 (|).

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.

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.

The following bug workaround options are available:

SSL_OP_ALL
    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 modifying options are available:

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.

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. See the SECURE RENEGOTIATION section for more details.

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.

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.

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.

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.

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

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.