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Clarify protocols supported.

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Update protocols supported and note that SSLv2 is effectively disabled
by default.

PR#3184
(cherry picked from commit 1b13a4f38dfc385d5e776f6b3e06c5795874cf9b)
This commit is contained in:
Dr. Stephen Henson 2014-06-28 21:54:13 +01:00
parent 377551b9c4
commit 6d02baf6ab
2 changed files with 28 additions and 10 deletions
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34
doc/ssl/SSL_CTX_new.pod
View file

@ -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

4
doc/ssl/SSL_CTX_set_cipher_list.pod
View file

@ -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