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    Command:

    SSL_CTX_set_options

    
           SSL_get_secure_renegotiation_support - manipulate SSL options
    
    
    

    SYNOPSIS

            #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

           Note: all these functions are implemented using macros.
    
           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.
    
    
    

    NOTES

           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
           logical 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() 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(), the
           current option setting is copied. Changes to ctx do not affect already
           created SSL objects. SSL_clear() does not affect the settings.
               mentioned above, this breaks this server so 16 bytes is the way to
               go.
    
           SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
               As of OpenSSL 0.9.8q and 1.0.0c, this option has no effect.
    
           SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
               ...
    
           SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
               ...
    
           SSL_OP_MSIE_SSLV2_RSA_PADDING
               As of OpenSSL 0.9.7h and 0.9.8a, this option has no effect.
    
           SSL_OP_SSLEAY_080_CLIENT_DH_BUG
               ...
    
           SSL_OP_TLS_D5_BUG
               ...
    
           SSL_OP_TLS_BLOCK_PADDING_BUG
               ...
    
           SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
               Disables a countermeasure against a SSL 3.0/TLS 1.0 protocol
               vulnerability affecting CBC ciphers, which cannot be handled by
               some broken SSL implementations.  This option has no effect for
               connections using other ciphers.
    
           SSL_OP_ALL
               All of the above bug workarounds.
    
           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_TLS_ROLLBACK_BUG
               Disable version rollback attack detection.
    
               During the client key exchange, the client must send the same
               information about acceptable SSL/TLS protocol levels as during the
               first hello. Some clients violate this rule by adapting to the
               server's answer. (Example: the client sends a SSLv2 hello and
               accepts up to SSLv3.1=TLSv1, the server only understands up to
               SSLv3. In this case the client must still use the same
               SSLv3.1=TLSv1 announcement. Some clients step down to SSLv3 with
               respect to the server's answer and violate the version rollback
               protection.)
    
           SSL_OP_CIPHER_SERVER_PREFERENCE
               When choosing a cipher, use the server's preferences instead of the
               client preferences. When not set, the SSL server will always follow
               the clients preferences. When set, the SSLv3/TLSv1 server will
               choose following its own preferences. Because of the different
               protocol, for SSLv2 the server will send its list of preferences to
               the client and the client chooses.
    
           SSL_OP_PKCS1_CHECK_1
               ...
    
           SSL_OP_PKCS1_CHECK_2
               ...
    
           SSL_OP_NETSCAPE_CA_DN_BUG
               If we accept a netscape connection, demand a client cert, have a
               non-self-signed CA which does not have its CA in netscape, and the
               browser has a cert, it will crash/hang.  Works for 3.x and 4.xbeta
    
           SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG
               ...
    
           SSL_OP_NO_SSLv2
               Do not use the SSLv2 protocol.
    
           SSL_OP_NO_SSLv3
               Do not use the SSLv3 protocol.
    
           SSL_OP_NO_TLSv1
               Do not use the TLSv1 protocol.
    
           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 will, where possible, transparently
               make use of RFC4507bis 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_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
               Allow legacy insecure renegotiation between OpenSSL and unpatched
               clients or servers. See the SECURE RENEGOTIATION section for more
               details.
    
           SSL_OP_LEGACY_SERVER_CONNECT
               Allow legacy insecure renegotiation between OpenSSL and unpatched
               servers only: this option is currently set by default. See the
               SECURE RENEGOTIATION section for more details.
    
           The following sections describe the operations permitted by OpenSSL's
           secure renegotiation implementation.
    
       Patched client and server
           Connections and renegotiation are always permitted by OpenSSL
           implementations.
    
       Unpatched client and patched OpenSSL server
           The initial connection suceeds but client renegotiation is denied by
           the server with a no_renegotiation warning alert if TLS v1.0 is used or
           a fatal handshake_failure alert in SSL v3.0.
    
           If the patched OpenSSL server attempts to renegotiate a fatal
           handshake_failure alert is sent. This is because the server code may be
           unaware of the unpatched nature of the client.
    
           If the option SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION is set then
           renegotiation always succeeds.
    
           NB: a bug in OpenSSL clients earlier than 0.9.8m (all of which are
           unpatched) will result in the connection hanging if it receives a
           no_renegotiation alert. OpenSSL versions 0.9.8m and later will regard a
           no_renegotiation alert as fatal and respond with a fatal
           handshake_failure alert. This is because the OpenSSL API currently has
           no provision to indicate to an application that a renegotiation attempt
           was refused.
    
       Patched OpenSSL client and unpatched server.
           If the option SSL_OP_LEGACY_SERVER_CONNECT or
           SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION is set then initial
           connections and renegotiation between patched OpenSSL clients and
           unpatched servers succeeds. If neither option is set then initial
           connections to unpatched servers will fail.
    
           The option SSL_OP_LEGACY_SERVER_CONNECT is currently set by default
           even though it has security implications: otherwise it would be
           impossible to connect to unpatched servers (i.e. all of them initially)
           and this is clearly not acceptable. Renegotiation is permitted because
           this does not add any additional security issues: during an attack
           clients do not see any renegotiations anyway.
    
           As more servers become patched the option SSL_OP_LEGACY_SERVER_CONNECT
           will not be set by default in a future version of OpenSSL.
    
           OpenSSL client applications wishing to ensure they can connect to
           unpatched servers should always set SSL_OP_LEGACY_SERVER_CONNECT
    
           OpenSSL client applications that want to ensure they can not connect to
           unpatched servers (and thus avoid any security issues) should always
           clear SSL_OP_LEGACY_SERVER_CONNECT using SSL_CTX_clear_options() or
           SSL_clear_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

           ssl(3), SSL_new(3), SSL_clear(3), SSL_CTX_set_tmp_dh_callback(3),
           SSL_CTX_set_tmp_rsa_callback(3), dhparam(1)
    
    
    

    HISTORY

           SSL_OP_CIPHER_SERVER_PREFERENCE and
           SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION have been added in
           OpenSSL 0.9.7.
    
           SSL_OP_TLS_ROLLBACK_BUG has been added in OpenSSL 0.9.6 and was
           automatically enabled with SSL_OP_ALL. As of 0.9.7, it is no longer
           included in SSL_OP_ALL and must be explicitly set.
    
           SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS has been added in OpenSSL 0.9.6e.
           Versions up to OpenSSL 0.9.6c do not include the countermeasure that
           can be disabled with this option (in OpenSSL 0.9.6d, it was always
           enabled).
    
           SSL_CTX_clear_options() and SSL_clear_options() were first added in
           OpenSSL 0.9.8m.
    
           SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION, SSL_OP_LEGACY_SERVER_CONNECT
           and the function SSL_get_secure_renegotiation_support() were first
           added in OpenSSL 0.9.8m.
    
    
    

    1.0.1e 2016-01-07 SSL_CTX_set_options(3)

    
    
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