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=pod

=head1 NAME

SSL_CTX_sessions - access internal session cache

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 struct lhash_st *SSL_CTX_sessions(SSL_CTX *ctx);

=head1 DESCRIPTION

SSL_CTX_sessions() returns a pointer to the lhash databases containing the

internal session cache for B<ctx>.

=head1 NOTES

The sessions in the internal session cache are kept in an

L<lhash(3)|lhash(3)> type database. It is possible to directly

access this database e.g. for searching. In parallel, the sessions

form a linked list which is maintained seperatly from the

L<lhash(3)|lhash(3)> operations, so that the database must not be

modified directly but by using the

L<SSL_CTX_add_session(3)|SSL_CTX_add_session(3)> family of functions.

=head1 SEE ALSO

L<ssl(3)|ssl(3)>, L<lhash(3)|lhash(3)>,

L<SSL_CTX_add_session(3)|SSL_CTX_add_session(3)>,

L<SSL_CTX_set_session_cache_mode(3)|SSL_CTX_set_session_cache_mode(3)>

=cut

=pod

=head1 NAME

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

=head1 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);

=head1 DESCRIPTION

SSL_CTX_set_options() adds the options set via bitmask in B<options> to B<ctx>.

Options already set before are not cleared.

SSL_set_options() adds the options set via bitmask in B<options> to B<ssl>.

Options already set before are not cleared.

SSL_CTX_get_options() returns the options set for B<ctx>.

SSL_get_options() returns the options set for B<ssl>.

=head1 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 B<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 B<ctx> do not affect already created

SSL objects. SSL_clear() does not affect the settings.

The following B<bug workaround> options are available:

=over 4

=item 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.

=item 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 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 opperating in SSLv2/v3 compatablity mode, but as mentioned above,

this breaks this server so 16 bytes is the way to go.

=item 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.

=item SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG

...

=item SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER

...

=item SSL_OP_MSIE_SSLV2_RSA_PADDING

...

=item SSL_OP_SSLEAY_080_CLIENT_DH_BUG

...

=item SSL_OP_TLS_D5_BUG

...

=item SSL_OP_TLS_BLOCK_PADDING_BUG

...

=item 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.)

=item SSL_OP_ALL

All of the above bug workarounds.

=back

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

options.

The following B<modifying> options are available:

=over 4

=item SSL_OP_SINGLE_DH_USE

Always create a new key when using temporary DH parameters.

=item SSL_OP_EPHEMERAL_RSA

Also use the temporary RSA key when doing RSA operations.

=item SSL_OP_PKCS1_CHECK_1

...

=item SSL_OP_PKCS1_CHECK_2

...

=item SSL_OP_NETSCAPE_CA_DN_BUG

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 

=item SSL_OP_NON_EXPORT_FIRST

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").

=item SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG

...

=item SSL_OP_NO_SSLv2

Do not use the SSLv2 protocol.

=item SSL_OP_NO_SSLv3

Do not use the SSLv3 protocol.

=item SSL_OP_NO_TLSv1

Do not use the TLSv1 protocol.

=back

=head1 RETURN VALUES

SSL_CTX_set_options() and SSL_set_options() return the new options bitmask

after adding B<options>.

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

=head1 SEE ALSO

L<ssl(3)|ssl(3)>, L<SSL_new(3)|SSL_new(3)>, L<SSL_clear(3)|SSL_clear(3)>

=head1 HISTORY

SSL_OP_TLS_ROLLBACK_BUG has been added in OpenSSL 0.9.6.

=cut