Fix grammar error in SSL_CTX_set_min_proto_version

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

diff --git a/doc/ssl/SSL_CTX_set_options.pod b/doc/ssl/SSL_CTX_set_options.pod
index e5837819dcab7f1ab0b929fd4294313dacacdc1d..63609f3a3192b71ee89ba6bd546a602bbcda3fa2 100644 (file)
--- a/doc/ssl/SSL_CTX_set_options.pod
+++ b/doc/ssl/SSL_CTX_set_options.pod
@@ -2,7 +2,9 @@
 
 =head1 NAME
 
 
 =head1 NAME
 

-SSL_CTX_set_options, SSL_set_options, SSL_CTX_get_options, SSL_get_options - manipulate SSL options
+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
 
 
 =head1 SYNOPSIS
 


@@ -21,8 +23,6 @@ SSL_CTX_set_options, SSL_set_options, SSL_CTX_get_options, SSL_get_options - man
 
 =head1 DESCRIPTION
 
 
 =head1 DESCRIPTION
 

-Note: all these functions are implemented using macros.
-

 SSL_CTX_set_options() adds the options set via bitmask in B<options> to B<ctx>.
 Options already set before are not cleared!
 
 SSL_CTX_set_options() adds the options set via bitmask in B<options> to B<ctx>.
 Options already set before are not cleared!
 


@@ -40,17 +40,18 @@ SSL_get_options() returns the options set for B<ssl>.
 
 SSL_get_secure_renegotiation_support() indicates whether the peer supports
 secure renegotiation.
 
 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.
 
 =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 logical B<or>
+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
 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)|SSL_CTX_set_mode(3)> and SSL_set_mode() functions.
+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
 
 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


@@ -61,36 +62,6 @@ The following B<bug workaround> options are available:
 
 =over 4
 
 
 =over 4
 

-=item SSL_OP_MICROSOFT_SESS_ID_BUG
-
-www.microsoft.com - when talking SSLv2, if session-id reuse is
-performed, the session-id passed back in the server-finished message
-is different from the one decided upon.
-
-=item SSL_OP_NETSCAPE_CHALLENGE_BUG
-
-Netscape-Commerce/1.12, when talking SSLv2, accepts a 32 byte
-challenge but then appears to only use 16 bytes when generating the
-encryption keys.  Using 16 bytes is ok but it should be ok to use 32.
-According to the SSLv3 spec, one should use 32 bytes for the challenge
-when operating in SSLv2/v3 compatibility mode, but as mentioned above,
-this breaks this server so 16 bytes is the way to go.
-
-=item SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
-
-ssl3.netscape.com:443, first a connection is established with RC4-MD5.
-If it is then resumed, we end up using DES-CBC3-SHA.  It should be
-RC4-MD5 according to 7.6.1.3, 'cipher_suite'.
-
-Netscape-Enterprise/2.01 (https://merchant.netscape.com) has this bug.
-It only really shows up when connecting via SSLv2/v3 then reconnecting
-via SSLv3. The cipher list changes....
-
-NEW INFORMATION.  Try connecting with a cipher list of just
-DES-CBC-SHA:RC4-MD5.  For some weird reason, each new connection uses
-RC4-MD5, but a re-connect tries to use DES-CBC-SHA.  So netscape, when
-doing a re-connect, always takes the first cipher in the cipher list.
-

 =item SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
 
 ...
 =item SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
 
 ...


@@ -99,9 +70,10 @@ doing a re-connect, always takes the first cipher in the cipher list.
 
 ...
 
 
 ...
 

-=item SSL_OP_MSIE_SSLV2_RSA_PADDING
+=item SSL_OP_SAFARI_ECDHE_ECDSA_BUG

 
 

-As of OpenSSL 0.9.7h and 0.9.8a, this option has no effect.
+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_SSLEAY_080_CLIENT_DH_BUG
 


@@ -111,10 +83,6 @@ As of OpenSSL 0.9.7h and 0.9.8a, this option has no effect.
 
 ...
 
 
 ...
 

-=item SSL_OP_TLS_BLOCK_PADDING_BUG
-
-...
-

 =item SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
 
 Disables a countermeasure against a SSL 3.0/TLS 1.0 protocol
 =item SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
 
 Disables a countermeasure against a SSL 3.0/TLS 1.0 protocol


@@ -122,6 +90,12 @@ vulnerability affecting CBC ciphers, which cannot be handled by some
 broken SSL implementations.  This option has no effect for connections
 using other ciphers.
 
 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.
 =item SSL_OP_ALL
 
 All of the above bug workarounds.


@@ -151,10 +125,10 @@ 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
 =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)|SSL_CTX_set_tmp_dh_callback(3)>).
+(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
 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)|dhparam(1)>).
+(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
 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


@@ -162,23 +136,14 @@ temporary/ephemeral DH parameters are used.
 
 =item SSL_OP_EPHEMERAL_RSA
 
 
 =item SSL_OP_EPHEMERAL_RSA
 

-Always use ephemeral (temporary) RSA key when doing RSA operations
-(see L<SSL_CTX_set_tmp_rsa_callback(3)|SSL_CTX_set_tmp_rsa_callback(3)>).
-According to the specifications this is only done, when a RSA key
-can only be used for signature operations (namely under export ciphers
-with restricted RSA keylength). By setting this option, ephemeral
-RSA keys are always used. This option breaks compatibility with the
-SSL/TLS specifications and may lead to interoperability problems with
-clients and should therefore never be used. Ciphers with EDH (ephemeral
-Diffie-Hellman) key exchange should be used instead.
+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
 
 =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 SSLv3/TLSv1 server will choose following its
-own preferences. Because of the different protocol, for SSLv2 the server
-will send its list of preferences to the client and the client chooses.
+preferences. When set, the SSL/TLS server will choose following its
+own preferences.

 
 =item SSL_OP_PKCS1_CHECK_1
 
 
 =item SSL_OP_PKCS1_CHECK_1
 


@@ -188,27 +153,16 @@ will send its list of preferences to the client and the client chooses.
 
 ...
 
 
 ...
 

-=item SSL_OP_NETSCAPE_CA_DN_BUG
-
-If we accept a netscape connection, demand a client cert, have a
-non-self-signed CA which does not have its CA in netscape, and the
-browser has a cert, it will crash/hang.  Works for 3.x and 4.xbeta 
-
-=item SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG
-
-...
-
-=item SSL_OP_NO_SSLv2

 
 

-Do not use the SSLv2 protocol.
+=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

 
 

-=item SSL_OP_NO_SSLv3
-
-Do not use the SSLv3 protocol.
-
-=item SSL_OP_NO_TLSv1
-
-Do not use the TLSv1 protocol.
+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
 
 
 =item SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
 


@@ -226,46 +180,88 @@ not be used by clients or servers.
 
 =item SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
 
 
 =item SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
 

-See the B<SECURE RENEGOTIATION> section for a discussion of the purpose of
-this option
+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
 
 
 =back
 
 =head1 SECURE RENEGOTIATION
 

-OpenSSL by 0.9.8m and later always attempts to use secure renegotiation as
-described in draft-ietf-tls-renegotiation (FIXME: replace by RFC). This
-counters a prefix attack described in the draft and elsewhere (FIXME: need full
-reference).
+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>.
 
 
 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>.
 

-If an unpatched client attempts to connect to a patched OpenSSL server then
-the attempt will succeed but renegotiation is not permitted. As required
-by the standard a B<no_renegotiation> alert is sent back to the client if
-the TLS v1.0 protocol is used. If SSLv3.0 is used then renegotiation results
-in a fatal B<handshake_failed> alert.
+The following sections describe the operations permitted by OpenSSL's secure
+renegotiation implementation.
+
+=head2 Patched client and server

 
 

-If a patched OpenSSL client attempts to connect to an unpatched server
-then the connection will fail because it is not possible to determine
-whether an attack is taking place.
+Connections and renegotiation are always permitted by OpenSSL implementations.

 
 

-If the option B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> is set then the
-renegotiation between unpatched clients and patched servers is permitted as
-well as initial connections and renegotiation between patched clients and
-unpatched servers. This option should be used with caution because it leaves
-both clients and servers vulnerable. However unpatched servers and clients are
-likely to be around for some time and simply refusing to connect to unpatched
-servers may well be considered unacceptable. So applications may be forced to
-use this option for the immediate future.
+=head2 Unpatched client and patched OpenSSL server

 
 

-The function SSL_get_secure_renegotiation_support() indicates whether the peer
-supports secure renegotiation. 
+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.

 
 

-The deprecated SSLv2 protocol does not support secure renegotiation at all.
+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
 
 
 =head1 RETURN VALUES
 


@@ -282,30 +278,23 @@ secure renegotiation and 0 if it does not.
 
 =head1 SEE ALSO
 
 
 =head1 SEE ALSO
 

-L<ssl(3)|ssl(3)>, L<SSL_new(3)|SSL_new(3)>, L<SSL_clear(3)|SSL_clear(3)>,
-L<SSL_CTX_set_tmp_dh_callback(3)|SSL_CTX_set_tmp_dh_callback(3)>,
-L<SSL_CTX_set_tmp_rsa_callback(3)|SSL_CTX_set_tmp_rsa_callback(3)>,
-L<dhparam(1)|dhparam(1)>
+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
 
 
 =head1 HISTORY
 

-B<SSL_OP_CIPHER_SERVER_PREFERENCE> and
-B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> have been added in
-OpenSSL 0.9.7.
-
-B<SSL_OP_TLS_ROLLBACK_BUG> has been added in OpenSSL 0.9.6 and was automatically
-enabled with B<SSL_OP_ALL>. As of 0.9.7, it is no longer included in B<SSL_OP_ALL>
-and must be explicitly set.
+The attempt to always try to use secure renegotiation was added in
+Openssl 0.9.8m.

 
 

-B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS> has been added in OpenSSL 0.9.6e.
-Versions up to OpenSSL 0.9.6c do not include the countermeasure that
-can be disabled with this option (in OpenSSL 0.9.6d, it was always
-enabled).
+=head1 COPYRIGHT

 
 

-SSL_CTX_clear_options() and SSL_clear_options() were first added in OpenSSL
-0.9.8m.
+Copyright 2001-2016 The OpenSSL Project Authors. All Rights Reserved.

 
 

-B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> was first added in OpenSSL
-0.9.8m.
+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
 
 =cut