MirOS Manual: SSL_CTX_get_options(3), SSL_CTX_set_options(3), SSL_get_options(3), SSL_set_options(3)


SSL_CTX_SET_OPTIONS(3)       OpenSSL       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.

     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:

     SSL_OP_MICROSOFT_SESS_ID_BUG
         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.

     SSL_OP_NETSCAPE_CHALLENGE_BUG
         Netscape-Commerce/1.12, when talking SSLv2, accepts a 32
         byte challenge but then appears to only use 16 bytes

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SSL_CTX_SET_OPTIONS(3)       OpenSSL       SSL_CTX_SET_OPTIONS(3)

         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 men-
         tioned above, this breaks this server so 16 bytes is the
         way to go.

     SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
         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.

     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 pro-
         tocol 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.

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SSL_CTX_SET_OPTIONS(3)       OpenSSL       SSL_CTX_SET_OPTIONS(3)

     It is usually safe to use SSL_OP_ALL to enable the bug wor-
     karound options if compatibility with somewhat broken imple-
     mentations 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 lev-
         els 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_SINGLE_DH_USE
         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 dhparam(1)).
         If "strong" primes were used, it is not strictly neces-
         sary 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 used.

         This is set by default in OpenSSL 0.9.7 on MirBSD.

     SSL_OP_EPHEMERAL_RSA
         This option is no longer implemented and is treated as
         no op.

     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
         ...

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SSL_CTX_SET_OPTIONS(3)       OpenSSL       SSL_CTX_SET_OPTIONS(3)

     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.

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),
     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).

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