[thirdparty/openssl.git] / doc / ssl / SSL_CTX_set_cipher_list.pod

=pod

=head1 NAME

SSL_CTX_set_cipher_list, SSL_set_cipher_list - choose list of available SSL_CIPHERs

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str);
 int SSL_set_cipher_list(SSL *ssl, const char *str);

=head1 DESCRIPTION

SSL_CTX_set_cipher_list() sets the list of available ciphers for B<ctx>
using the control string B<str>. The format of the string is described
in L<ciphers(1)>. The list of ciphers is inherited by all
B<ssl> objects created from B<ctx>.

SSL_set_cipher_list() sets the list of ciphers only for B<ssl>.

=head1 NOTES

The control string B<str> should be universally usable and not depend
on details of the library configuration (ciphers compiled in). Thus no
syntax checking takes place. Items that are not recognized, because the
corresponding ciphers are not compiled in or because they are mistyped,
are simply ignored. Failure is only flagged if no ciphers could be collected
at all.

It should be noted, that inclusion of a cipher to be used into the list is
a necessary condition. On the client side, the inclusion into the list is
also sufficient unless the security level excludes it. On the server side,
additional restrictions apply. All ciphers have additional requirements.
ADH ciphers don't need a certificate, but DH-parameters must have been set.
All other ciphers need a corresponding certificate and key.

A RSA cipher can only be chosen, when a RSA certificate is available.
RSA export ciphers with a keylength of 512 bits for the RSA key require
a temporary 512 bit RSA key, as typically the supplied key has a length
of 1024 bit (see
L<SSL_CTX_set_tmp_rsa_callback(3)>).
RSA ciphers using DHE need a certificate and key and additional DH-parameters
(see L<SSL_CTX_set_tmp_dh_callback(3)>).

A DSA cipher can only be chosen, when a DSA certificate is available.
DSA ciphers always use DH key exchange and therefore need DH-parameters
(see L<SSL_CTX_set_tmp_dh_callback(3)>).

When these conditions are not met for any cipher in the list (e.g. a
client only supports export RSA ciphers with a asymmetric key length
of 512 bits and the server is not configured to use temporary RSA
keys), the "no shared cipher" (SSL_R_NO_SHARED_CIPHER) error is generated
and the handshake will fail.

=head1 RETURN VALUES

SSL_CTX_set_cipher_list() and SSL_set_cipher_list() return 1 if any cipher
could be selected and 0 on complete failure.

=head1 SEE ALSO

L<ssl(3)>, L<SSL_get_ciphers(3)>,
L<SSL_CTX_use_certificate(3)>,
L<SSL_CTX_set_tmp_rsa_callback(3)>,
L<SSL_CTX_set_tmp_dh_callback(3)>,
L<ciphers(1)>

=cut
Commit	Line	Data
615513ba RL	1	=pod
	2
	3	=head1 NAME
	4
66ebbb6a	5	SSL_CTX_set_cipher_list, SSL_set_cipher_list - choose list of available SSL_CIPHERs
615513ba RL	6
	7	=head1 SYNOPSIS
	8
	9	#include <openssl/ssl.h>
	10
	11	int SSL_CTX_set_cipher_list(SSL_CTX ctx, const char str);
	12	int SSL_set_cipher_list(SSL ssl, const char str);
	13
	14	=head1 DESCRIPTION
	15
	16	SSL_CTX_set_cipher_list() sets the list of available ciphers for B<ctx>
	17	using the control string B<str>. The format of the string is described
9b86974e	18	in L<ciphers(1)>. The list of ciphers is inherited by all
615513ba RL	19	B<ssl> objects created from B<ctx>.
	20
	21	SSL_set_cipher_list() sets the list of ciphers only for B<ssl>.
	22
	23	=head1 NOTES
	24
c69c47b9	25	The control string B<str> should be universally usable and not depend
615513ba RL	26	on details of the library configuration (ciphers compiled in). Thus no
615513ba RL	27	syntax checking takes place. Items that are not recognized, because the
c69c47b9	28	corresponding ciphers are not compiled in or because they are mistyped,
615513ba RL	29	are simply ignored. Failure is only flagged if no ciphers could be collected
	30	at all.
	31
dd3430a6 RL	32	It should be noted, that inclusion of a cipher to be used into the list is
dd3430a6 RL	33	a necessary condition. On the client side, the inclusion into the list is
0f817d3b DSH	34	also sufficient unless the security level excludes it. On the server side,
	35	additional restrictions apply. All ciphers have additional requirements.
	36	ADH ciphers don't need a certificate, but DH-parameters must have been set.
	37	All other ciphers need a corresponding certificate and key.
6d3dec92 LJ	38
	39	A RSA cipher can only be chosen, when a RSA certificate is available.
	40	RSA export ciphers with a keylength of 512 bits for the RSA key require
	41	a temporary 512 bit RSA key, as typically the supplied key has a length
4db48ec0	42	of 1024 bit (see
9b86974e	43	L<SSL_CTX_set_tmp_rsa_callback(3)>).
0b30fc90	44	RSA ciphers using DHE need a certificate and key and additional DH-parameters
9b86974e	45	(see L<SSL_CTX_set_tmp_dh_callback(3)>).
6d3dec92 LJ	46
6d3dec92 LJ	47	A DSA cipher can only be chosen, when a DSA certificate is available.
3e3dac9f	48	DSA ciphers always use DH key exchange and therefore need DH-parameters
9b86974e	49	(see L<SSL_CTX_set_tmp_dh_callback(3)>).
6d3dec92 LJ	50
	51	When these conditions are not met for any cipher in the list (e.g. a
	52	client only supports export RSA ciphers with a asymmetric key length
	53	of 512 bits and the server is not configured to use temporary RSA
	54	keys), the "no shared cipher" (SSL_R_NO_SHARED_CIPHER) error is generated
	55	and the handshake will fail.
dd3430a6	56
615513ba RL	57	=head1 RETURN VALUES
	58
	59	SSL_CTX_set_cipher_list() and SSL_set_cipher_list() return 1 if any cipher
	60	could be selected and 0 on complete failure.
	61
	62	=head1 SEE ALSO
	63
9b86974e RS	64	L<ssl(3)>, L<SSL_get_ciphers(3)>,
	65	L<SSL_CTX_use_certificate(3)>,
	66	L<SSL_CTX_set_tmp_rsa_callback(3)>,
	67	L<SSL_CTX_set_tmp_dh_callback(3)>,
	68	L<ciphers(1)>
615513ba RL	69
615513ba RL	70	=cut