*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->NetBSD man pages -> SSL_CTX_set_options (3)              



NAME    [Toc]    [Back]

       SSL_CTX_set_options, SSL_set_options, SSL_CTX_get_options,
       SSL_get_options - manipulate SSL engine options

LIBRARY    [Toc]    [Back]

       libcrypto, -lcrypto

SYNOPSIS    [Toc]    [Back]

        #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    [Toc]    [Back]

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

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

       SSL_CTX_get_options() returns the options set for ctx.

       SSL_get_options() returns the options set for ssl.

NOTES    [Toc]    [Back]

       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.

       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.

       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
 , '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







           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.)

           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

           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:

           Always create a new key when using temporary/ephemeral
           DH parameters (see SSL_CTX_set_tmp_dh_callback(3)).
           This option must be used to prevent small subgroup
           attacks, when the DH parameters were not generated
           using "strong" primes (e.g. when using DSA-parameters,
           see openssl_dhparam(1)).  If "strong" primes were
           used, it is not strictly necessary to generate a new
           DH key during each handshake but it is also recommended.
  SSL_OP_SINGLE_DH_USE should therefore be
           enabled whenever temporary/ephemeral DH parameters are

           Always use ephemeral (temporary) RSA key when doing
           RSA operations (see SSL_CTX_set_tmp_rsa_callback(3)).
           According to the specifications this is only done,
           when a RSA key can only be used for signature operations
 (namely under export ciphers with restricted RSA
           keylength). By setting this option, ephemeral RSA keys
           are always used. This option breaks compatibility with
           the SSL/TLS specifications and may lead to interoperability
 problems with clients and should therefore
           never be used. Ciphers with EDH (ephemeral DiffieHellman)
 key exchange should be used instead.



           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


           Do not use the SSLv2 protocol.

           Do not use the SSLv3 protocol.

           Do not use the TLSv1 protocol.

RETURN VALUES    [Toc]    [Back]

       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    [Toc]    [Back]

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

HISTORY    [Toc]    [Back]

       SSL_OP_TLS_ROLLBACK_BUG has been added in OpenSSL 0.9.6.

       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).

2002-07-31                    0.9.6g       SSL_CTX_set_options(3)
[ Back ]
 Similar pages
Name OS Title
SSL_CTX_get_mode OpenBSD manipulate SSL engine mode
SSL_set_mode Tru64 Manipulate SSL engine mode
SSL_CTX_set_mode Tru64 Manipulate SSL engine mode
SSL_CTX_set_mode NetBSD manipulate SSL engine mode
SSL_get_mode OpenBSD manipulate SSL engine mode
SSL_CTX_set_mode OpenBSD manipulate SSL engine mode
SSL_set_mode OpenBSD manipulate SSL engine mode
SSL_get_mode Tru64 Manipulate SSL engine mode
SSL_CTX_get_mode Tru64 Manipulate SSL engine mode
DtMmdbQuit HP-UX shuts down the DtInfo database engine
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service