Correct example.

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

diff --git a/doc/ssl/SSL_CTX_set_cipher_list.pod b/doc/ssl/SSL_CTX_set_cipher_list.pod
index 9a29eeeb9558deaf08f89af9a0d3d367f4222c36..c2c349f65e7b6c2fea47715f8f8bad111858d31c 100644 (file)
--- a/doc/ssl/SSL_CTX_set_cipher_list.pod
+++ b/doc/ssl/SSL_CTX_set_cipher_list.pod
@@ -31,12 +31,28 @@ 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. 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, the respective is valid for DSA ciphers. Ciphers using EDH need
-a certificate and key and DH-parameters.
+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)|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)|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)|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
 
@@ -47,6 +63,8 @@ could be selected and 0 on complete failure.
 
 L<ssl(3)|ssl(3)>, L<SSL_get_ciphers(3)|SSL_get_ciphers(3)>,
 L<SSL_CTX_use_certificate(3)|SSL_CTX_use_certificate(3)>,
+L<SSL_CTX_set_tmp_rsa_callback(3)|SSL_CTX_set_tmp_rsa_callback(3)>,
+L<SSL_CTX_set_tmp_dh_callback(3)|SSL_CTX_set_tmp_dh_callback(3)>,
 L<ciphers(1)|ciphers(1)>
 
 =cut