+++ /dev/null
-=pod
-
-=head1 NAME
-
-SSL_CTX_set_options, SSL_set_options, SSL_CTX_clear_options,
-SSL_clear_options, SSL_CTX_get_options, SSL_get_options,
-SSL_get_secure_renegotiation_support - manipulate SSL options
-
-=head1 SYNOPSIS
-
- #include <openssl/ssl.h>
-
- long SSL_CTX_set_options(SSL_CTX *ctx, long options);
- long SSL_set_options(SSL *ssl, long options);
-
- long SSL_CTX_clear_options(SSL_CTX *ctx, long options);
- long SSL_clear_options(SSL *ssl, long options);
-
- long SSL_CTX_get_options(SSL_CTX *ctx);
- long SSL_get_options(SSL *ssl);
-
- long SSL_get_secure_renegotiation_support(SSL *ssl);
-
-=head1 DESCRIPTION
-
-SSL_CTX_set_options() adds the options set via bitmask in B<options> to B<ctx>.
-Options already set before are not cleared!
-
-SSL_set_options() adds the options set via bitmask in B<options> to B<ssl>.
-Options already set before are not cleared!
-
-SSL_CTX_clear_options() clears the options set via bitmask in B<options>
-to B<ctx>.
-
-SSL_clear_options() clears the options set via bitmask in B<options> to B<ssl>.
-
-SSL_CTX_get_options() returns the options set for B<ctx>.
-
-SSL_get_options() returns the options set for B<ssl>.
-
-SSL_get_secure_renegotiation_support() indicates whether the peer supports
-secure renegotiation.
-Note, this is implemented via a macro.
-
-=head1 NOTES
-
-The behaviour of the SSL library can be changed by setting several options.
-The options are coded as bitmasks and can be combined by a bitwise B<or>
-operation (|).
-
-SSL_CTX_set_options() and SSL_set_options() affect the (external)
-protocol behaviour of the SSL library. The (internal) behaviour of
-the API can be changed by using the similar
-L<SSL_CTX_set_mode(3)> and SSL_set_mode() functions.
-
-During a handshake, the option settings of the SSL object are used. When
-a new SSL object is created from a context using SSL_new(), the current
-option setting is copied. Changes to B<ctx> do not affect already created
-SSL objects. SSL_clear() does not affect the settings.
-
-The following B<bug workaround> options are available:
-
-=over 4
-
-=item SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
-
-...
-
-=item SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
-
-...
-
-=item SSL_OP_SAFARI_ECDHE_ECDSA_BUG
-
-Don't prefer ECDHE-ECDSA ciphers when the client appears to be Safari on OS X.
-OS X 10.8..10.8.3 has broken support for ECDHE-ECDSA ciphers.
-
-=item SSL_OP_SSLEAY_080_CLIENT_DH_BUG
-
-...
-
-=item SSL_OP_TLS_D5_BUG
-
-...
-
-=item SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
-
-Disables a countermeasure against a SSL 3.0/TLS 1.0 protocol
-vulnerability affecting CBC ciphers, which cannot be handled by some
-broken SSL implementations. This option has no effect for connections
-using other ciphers.
-
-=item SSL_OP_TLSEXT_PADDING
-
-Adds a padding extension to ensure the ClientHello size is never between
-256 and 511 bytes in length. This is needed as a workaround for some
-implementations.
-
-=item SSL_OP_ALL
-
-All of the above bug workarounds.
-
-=back
-
-It is usually safe to use B<SSL_OP_ALL> to enable the bug workaround
-options if compatibility with somewhat broken implementations is
-desired.
-
-The following B<modifying> options are available:
-
-=over 4
-
-=item SSL_OP_TLS_ROLLBACK_BUG
-
-Disable version rollback attack detection.
-
-During the client key exchange, the client must send the same information
-about acceptable SSL/TLS protocol levels as during the first hello. Some
-clients violate this rule by adapting to the server's answer. (Example:
-the client sends a SSLv2 hello and accepts up to SSLv3.1=TLSv1, the server
-only understands up to SSLv3. In this case the client must still use the
-same SSLv3.1=TLSv1 announcement. Some clients step down to SSLv3 with respect
-to the server's answer and violate the version rollback protection.)
-
-=item SSL_OP_SINGLE_DH_USE
-
-Always create a new key when using temporary/ephemeral DH parameters
-(see L<SSL_CTX_set_tmp_dh_callback(3)>).
-This option must be used to prevent small subgroup attacks, when
-the DH parameters were not generated using "strong" primes
-(e.g. when using DSA-parameters, see L<dhparam(1)>).
-If "strong" primes were used, it is not strictly necessary to generate
-a new DH key during each handshake but it is also recommended.
-B<SSL_OP_SINGLE_DH_USE> should therefore be enabled whenever
-temporary/ephemeral DH parameters are used.
-
-=item SSL_OP_EPHEMERAL_RSA
-
-This option is no longer implemented and is treated as no op.
-
-=item SSL_OP_CIPHER_SERVER_PREFERENCE
-
-When choosing a cipher, use the server's preferences instead of the client
-preferences. When not set, the SSL server will always follow the clients
-preferences. When set, the SSL/TLS server will choose following its
-own preferences.
-
-=item SSL_OP_PKCS1_CHECK_1
-
-...
-
-=item SSL_OP_PKCS1_CHECK_2
-
-...
-
-
-=item SSL_OP_NO_SSLv3, SSL_OP_NO_TLSv1, SSL_OP_NO_TLSv1_1,
-SSL_OP_NO_TLSv1_2, SSL_OP_NO_DTLSv1, SSL_OP_NO_DTLSv1_2
-
-These options turn off the SSLv3, TLSv1, TLSv1.1 or TLSv1.2 protocol
-versions with TLS or the DTLSv1, DTLSv1.2 versions with DTLS,
-respectively.
-As of OpenSSL 1.1.0, these options are deprecated, use
-L<SSL_CTX_set_min_proto_version(3)> and
-L<SSL_CTX_set_max_proto_version(3)> instead.
-
-=item SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
-
-When performing renegotiation as a server, always start a new session
-(i.e., session resumption requests are only accepted in the initial
-handshake). This option is not needed for clients.
-
-=item SSL_OP_NO_TICKET
-
-Normally clients and servers will, where possible, transparently make use
-of RFC4507bis tickets for stateless session resumption.
-
-If this option is set this functionality is disabled and tickets will
-not be used by clients or servers.
-
-=item SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
-
-Allow legacy insecure renegotiation between OpenSSL and unpatched clients or
-servers. See the B<SECURE RENEGOTIATION> section for more details.
-
-=item SSL_OP_LEGACY_SERVER_CONNECT
-
-Allow legacy insecure renegotiation between OpenSSL and unpatched servers
-B<only>: this option is currently set by default. See the
-B<SECURE RENEGOTIATION> section for more details.
-
-=item SSL_OP_NO_ENCRYPT_THEN_MAC
-
-Normally clients and servers will transparently attempt to negotiate the
-RFC7366 Encrypt-then-MAC option on TLS and DTLS connection.
-
-If this option is set, Encrypt-then-MAC is disabled. Clients will not
-propose, and servers will not accept the extension.
-
-=back
-
-=head1 SECURE RENEGOTIATION
-
-OpenSSL always attempts to use secure renegotiation as
-described in RFC5746. This counters the prefix attack described in
-CVE-2009-3555 and elsewhere.
-
-This attack has far reaching consequences which application writers should be
-aware of. In the description below an implementation supporting secure
-renegotiation is referred to as I<patched>. A server not supporting secure
-renegotiation is referred to as I<unpatched>.
-
-The following sections describe the operations permitted by OpenSSL's secure
-renegotiation implementation.
-
-=head2 Patched client and server
-
-Connections and renegotiation are always permitted by OpenSSL implementations.
-
-=head2 Unpatched client and patched OpenSSL server
-
-The initial connection succeeds but client renegotiation is denied by the
-server with a B<no_renegotiation> warning alert if TLS v1.0 is used or a fatal
-B<handshake_failure> alert in SSL v3.0.
-
-If the patched OpenSSL server attempts to renegotiate a fatal
-B<handshake_failure> alert is sent. This is because the server code may be
-unaware of the unpatched nature of the client.
-
-If the option B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> is set then
-renegotiation B<always> succeeds.
-
-=head2 Patched OpenSSL client and unpatched server.
-
-If the option B<SSL_OP_LEGACY_SERVER_CONNECT> or
-B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> is set then initial connections
-and renegotiation between patched OpenSSL clients and unpatched servers
-succeeds. If neither option is set then initial connections to unpatched
-servers will fail.
-
-The option B<SSL_OP_LEGACY_SERVER_CONNECT> is currently set by default even
-though it has security implications: otherwise it would be impossible to
-connect to unpatched servers (i.e. all of them initially) and this is clearly
-not acceptable. Renegotiation is permitted because this does not add any
-additional security issues: during an attack clients do not see any
-renegotiations anyway.
-
-As more servers become patched the option B<SSL_OP_LEGACY_SERVER_CONNECT> will
-B<not> be set by default in a future version of OpenSSL.
-
-OpenSSL client applications wishing to ensure they can connect to unpatched
-servers should always B<set> B<SSL_OP_LEGACY_SERVER_CONNECT>
-
-OpenSSL client applications that want to ensure they can B<not> connect to
-unpatched servers (and thus avoid any security issues) should always B<clear>
-B<SSL_OP_LEGACY_SERVER_CONNECT> using SSL_CTX_clear_options() or
-SSL_clear_options().
-
-The difference between the B<SSL_OP_LEGACY_SERVER_CONNECT> and
-B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> options is that
-B<SSL_OP_LEGACY_SERVER_CONNECT> enables initial connections and secure
-renegotiation between OpenSSL clients and unpatched servers B<only>, while
-B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> allows initial connections
-and renegotiation between OpenSSL and unpatched clients or servers.
-
-=head1 RETURN VALUES
-
-SSL_CTX_set_options() and SSL_set_options() return the new options bitmask
-after adding B<options>.
-
-SSL_CTX_clear_options() and SSL_clear_options() return the new options bitmask
-after clearing B<options>.
-
-SSL_CTX_get_options() and SSL_get_options() return the current bitmask.
-
-SSL_get_secure_renegotiation_support() returns 1 is the peer supports
-secure renegotiation and 0 if it does not.
-
-=head1 SEE ALSO
-
-L<ssl(3)>, L<SSL_new(3)>, L<SSL_clear(3)>,
-L<SSL_CTX_set_tmp_dh_callback(3)>,
-L<SSL_CTX_set_min_proto_version(3)>,
-L<dhparam(1)>
-
-=head1 HISTORY
-
-The attempt to always try to use secure renegotiation was added in
-Openssl 0.9.8m.
-
-=head1 COPYRIGHT
-
-Copyright 2001-2016 The OpenSSL Project Authors. All Rights Reserved.
-
-Licensed under the OpenSSL license (the "License"). You may not use
-this file except in compliance with the License. You can obtain a copy
-in the file LICENSE in the source distribution or at
-L<https://www.openssl.org/source/license.html>.
-
-=cut
projects / openssl.git / blobdiff