SSL_CTX_set_options(3)

NAME
SSL_CTX_set_options, SSL_set_options, SSL_CTX_get_options, SSL_get_options - manipulate SSL engine 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_get_options(SSL_CTX *ctx);
 long SSL_get_options(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_get_options() returns the options set for ctx.

SSL_get_options() returns the options set for ssl.

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 (|). Options can only be added but can never be reset.

During a handshake, the option settings of the SSL object 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.

The following bug workaround options are available: www.microsoft.com - when talking SSLv2, if session-id reuse is performed, the session-id passed back in the server-finished message is different from the one decided upon. Netscape-Commerce/1.12, when talking SSLv2, accepts a 32 byte challenge but then appears to only use 16 bytes when generating the encryption keys. Using 16 bytes is ok but it should be ok to use 32. According to the SSLv3 spec, one should use 32 bytes for the challenge when operating in SSLv2/v3 compatibility mode, but as mentioned above, this breaks this server so 16 bytes is the way to go. ssl3.netscape.com:443, first a connection is established with RC4-MD5. If it is then resumed, we end up using DES-CBC3-SHA. It should be RC4-MD5 according to 7.6.1.3, 'cipher_suite'.

Netscape-Enterprise/2.01 (https://merchant.netscape.com) has this bug. It only really shows up when connecting via SSLv2/v3 then reconnecting via SSLv3. The cipher list changes....

NEW INFORMATION. Try connecting with a cipher list of just DES-CBC-SHA:RC4-MD5. For some weird reason, each new connection uses RC4-MD5, but a re-connect tries to use DES-CBC-SHA. So netscape, when doing a re-connect, always takes the first cipher in the cipher list. ... ... ... ... ... ... 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.) All of the above bug workarounds.

It is save and recommended to use SSL_OP_ALL to enable the bug workaround options.

The following modifying options are available: Always create a new key when using temporary DH parameters. Also use the temporary RSA key when doing RSA operations. ... ... If we accept a netscape connection, demand a client cert, have a non-self-sighed CA which does not have it's CA in netscape, and the browser has a cert, it will crash/hang. Works for 3.x and 4.xbeta On servers try to use non-export (stronger) ciphers first. This option does not work under all circumstances (in the code it is declared "broken"). ... Do not use the SSLv2 protocol. Do not use the SSLv3 protocol. Do not use the TLSv1 protocol.

RETURN VALUES
SSL_CTX_set_options() and SSL_set_options() return the new options bitmask after adding options.

SSL_CTX_get_options() and SSL_get_options() return the current bitmask.

SEE ALSO
ssl(3), SSL_new(3), SSL_clear(3)

HISTORY
SSL_OP_TLS_ROLLBACK_BUG has been added in OpenSSL 0.9.6.