diff options
Diffstat (limited to 'openssl/doc/ssl/SSL_CTX_new.pod')
| -rw-r--r-- | openssl/doc/ssl/SSL_CTX_new.pod | 34 |
1 files changed, 24 insertions, 10 deletions
diff --git a/openssl/doc/ssl/SSL_CTX_new.pod b/openssl/doc/ssl/SSL_CTX_new.pod index 73e8c47f9..491ac8c17 100644 --- a/openssl/doc/ssl/SSL_CTX_new.pod +++ b/openssl/doc/ssl/SSL_CTX_new.pod @@ -51,22 +51,36 @@ 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<not> 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<SSL_CTX_set_options()> or -B<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 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 |