Add some documentation for SSL_get_shared_ciphers()

=head1 NAME

SSL_get1_supported_ciphers, SSL_get_client_ciphers,

SSL_get_ciphers, SSL_CTX_get_ciphers, SSL_get_cipher_list

SSL_get1_supported_ciphers,

SSL_get_client_ciphers,

SSL_get_ciphers,

SSL_CTX_get_ciphers,

SSL_get_cipher_list,

SSL_get_shared_ciphers

- get list of available SSL_CIPHERs

=head1 SYNOPSIS

 STACK_OF(SSL_CIPHER) *SSL_get1_supported_ciphers(SSL *s);

 STACK_OF(SSL_CIPHER) *SSL_get_client_ciphers(const SSL *ssl);

 const char *SSL_get_cipher_list(const SSL *ssl, int priority);

 char *SSL_get_shared_ciphers(const SSL *s, char *buf, int size);

=head1 DESCRIPTION

SSL_CTX_get_ciphers() returns the stack of available SSL_CIPHERs for B<ctx>.

SSL_get1_supported_ciphers() returns the stack of enabled SSL_CIPHERs for

B<ssl>, sorted by preference.

B<ssl> as would be sent in a ClientHello (that is, sorted by preference).

The list depends on settings like the cipher list, the supported protocol

versions, the security level, and the enabled signature algorithms.

SRP and PSK ciphers are only enabled if the appropriate callbacks or settings

have been applied.

This is the list that will be sent by the client to the server.

The list supported by the server might include more ciphers in case there is a

hole in the list of supported protocols.

The server will also not use ciphers from this list depending on the

configured certificates and DH parameters.

The list of ciphers that would be sent in a ClientHello can differ from

the list of ciphers that would be acceptable when acting as a server.

For example, additional ciphers may be usable by a server if there is

a gap in the list of supported protocols, and some ciphers may not be

usable by a server if there is not a suitable certificate configured.

If B<ssl> is NULL or no ciphers are available, NULL is returned.

SSL_get_client_ciphers() returns the stack of available SSL_CIPHERs matching the

available, or there are less ciphers than B<priority> available, NULL

is returned.

SSL_get_shared_ciphers() creates a colon separated and NUL terminated list of

SSL_CIPHER names that are available in both the client and the server. B<buf> is

the buffer that should be populated with the list of names and B<size> is the

size of that buffer. A pointer to B<buf> is returned on success or NULL on

error. If the supplied buffer is not large enough to contain the complete list

of names then a truncated list of names will be returned. Note that just because

a ciphersuite is available (i.e. it is configured in the cipher list) and shared

by both the client and the server it does not mean that it is enabled (see the

description of SSL_get1_supported_ciphers() above). This function will return

available shared ciphersuites whether or not they are enabled. This is a server

side function only and must only be called after the completion of the initial

handshake.

=head1 NOTES

The details of the ciphers obtained by SSL_get_ciphers(), SSL_CTX_get_ciphers()

=item SSL_SESSION *B<SSL_get_session>(const SSL *ssl);

=item char *B<SSL_get_shared_ciphers>(const SSL *ssl, char *buf, int len);

=item char *B<SSL_get_shared_ciphers>(const SSL *ssl, char *buf, int size);

=item int B<SSL_get_shutdown>(const SSL *ssl);