From: Dr. Stephen Henson Date: Sat, 28 Jun 2014 20:54:13 +0000 (+0100) Subject: Clarify protocols supported. X-Git-Tag: master-post-reformat~653^2~4 X-Git-Url: https://git.openssl.org/?p=openssl.git;a=commitdiff_plain;h=528b1f9a9f9831f8440e23be70e0139ba7c0bd98 Clarify protocols supported. Update protocols supported and note that SSLv2 is effectively disabled by default. PR#3184 --- diff --git a/doc/ssl/SSL_CTX_new.pod b/doc/ssl/SSL_CTX_new.pod index 23e13e134e..89249df32a 100644 --- a/doc/ssl/SSL_CTX_new.pod +++ b/doc/ssl/SSL_CTX_new.pod @@ -62,22 +62,36 @@ SSLv3 client hello messages. =item SSLv23_method(void), SSLv23_server_method(void), SSLv23_client_method(void) -A TLS/SSL connection established with these methods will understand the SSLv2, -SSLv3, and TLSv1 protocol. A client will send out SSLv2 client hello messages -and will indicate that it also understands SSLv3 and TLSv1. A server will -understand SSLv2, SSLv3, and TLSv1 client hello messages. This is the best -choice when compatibility is a concern. +A TLS/SSL connection established with these methods may understand the SSLv2, +SSLv3, TLSv1, TLSv1.1 and TLSv1.2 protocols. + +If the cipher list does not contain any SSLv2 ciphersuites (the default +cipher list does not) or extensions are required (for example server name) +a client will send out TLSv1 client hello messages including extensions and +will indicate that it also understands TLSv1.1, TLSv1.2 and permits a +fallback to SSLv3. A server will support SSLv3, TLSv1, TLSv1.1 and TLSv1.2 +protocols. This is the best choice when compatibility is a concern. + +If any SSLv2 ciphersuites are included in the cipher list and no extensions +are required then SSLv2 compatible client hellos will be used by clients and +SSLv2 will be accepted by servers. This is B recommended due to the +insecurity of SSLv2 and the limited nature of the SSLv2 client hello +prohibiting the use of extensions. =back The list of protocols available can later be limited using the SSL_OP_NO_SSLv2, -SSL_OP_NO_SSLv3, SSL_OP_NO_TLSv1 options of the B or -B functions. Using these options it is possible to choose -e.g. SSLv23_server_method() and be able to negotiate with all possible -clients, but to only allow newer protocols like SSLv3 or TLSv1. +SSL_OP_NO_SSLv3, SSL_OP_NO_TLSv1, SSL_OP_NO_TLSv1_1 and SSL_OP_NO_TLSv1_2 +options of the SSL_CTX_set_options() or SSL_set_options() functions. +Using these options it is possible to choose e.g. SSLv23_server_method() and +be able to negotiate with all possible clients, but to only allow newer +protocols like TLSv1, TLSv1.1 or TLS v1.2. + +Applications which never want to support SSLv2 (even is the cipher string +is configured to use SSLv2 ciphersuites) can set SSL_OP_NO_SSLv2. SSL_CTX_new() initializes the list of ciphers, the session cache setting, -the callbacks, the keys and certificates, and the options to its default +the callbacks, the keys and certificates and the options to its default values. =head1 RETURN VALUES diff --git a/doc/ssl/SSL_CTX_set_cipher_list.pod b/doc/ssl/SSL_CTX_set_cipher_list.pod index c2c349f65e..8b41917334 100644 --- a/doc/ssl/SSL_CTX_set_cipher_list.pod +++ b/doc/ssl/SSL_CTX_set_cipher_list.pod @@ -54,6 +54,10 @@ 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. +If the cipher list does not contain any SSLv2 cipher suites (this is the +default) then SSLv2 is effectively disabled and neither clients nor servers +will attempt to use SSLv2. + =head1 RETURN VALUES SSL_CTX_set_cipher_list() and SSL_set_cipher_list() return 1 if any cipher