Remove SSL_OP_TLS_BLOCK_PADDING_BUG

[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 7ffe9481121c734b2c13cb0d8b8d12c30782eb0f..84dde2805ec2d3119ded9a0f1136b89d9ee5caa3 100644 (file)
--- a/doc/ssl/SSL_CTX_set_options.pod
+++ b/doc/ssl/SSL_CTX_set_options.pod
@@ -44,7 +44,7 @@ secure renegotiation.
 =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)
 operation (|).
 
 SSL_CTX_set_options() and SSL_set_options() affect the (external)


@@ -63,33 +63,15 @@ The following B<bug workaround> options are available:
 
 =item SSL_OP_MICROSOFT_SESS_ID_BUG
 
 
 =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.
+As of OpenSSL 1.0.0 this option has no effect.

 
 =item SSL_OP_NETSCAPE_CHALLENGE_BUG
 
 
 =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.
+As of OpenSSL 1.0.0 this option has no effect.

 
 =item SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
 
 
 =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.
+As of OpenSSL 0.9.8q and 1.0.0c, this option has no effect.

 
 =item SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
 
 
 =item SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
 


@@ -99,9 +81,10 @@ 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 +94,6 @@ 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 +101,12 @@ 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.


@@ -162,15 +147,7 @@ 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
 
 
 =item SSL_OP_CIPHER_SERVER_PREFERENCE
 


@@ -188,15 +165,7 @@ 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
 
 
 =item SSL_OP_NO_SSLv2
 


@@ -224,37 +193,49 @@ 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.
 
 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, SSL_OP_LEGACY_SERVER_CONNECT
+=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

 
 

-See the B<SECURE RENEGOTIATION> section for a discussion of the purpose of
-these options.
+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.

 
 =back
 
 =head1 SECURE RENEGOTIATION
 
 OpenSSL 0.9.8m and later always attempts to use secure renegotiation as
 
 =back
 
 =head1 SECURE RENEGOTIATION
 
 OpenSSL 0.9.8m and later always attempts to use secure renegotiation as

-described in draft-ietf-tls-renegotiation (FIXME: replace by RFC). This
-counters the prefix attack described in CVE-2009-3555 and elsewhere.
+described in RFC5746. This counters the prefix attack described in
+CVE-2009-3555 and elsewhere.
+
+The deprecated and highly broken SSLv2 protocol does not support
+renegotiation at all: its use is B<strongly> discouraged.

 
 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>.
 

+The following sections describe the operations permitted by OpenSSL's secure
+renegotiation implementation.
+

 =head2 Patched client and server
 
 =head2 Patched client and server
 

-Connections and renegotiation will always succeed.
+Connections and renegotiation are always permitted by OpenSSL implementations.

 
 

-=head2 Unpatched client and patched server
+=head2 Unpatched client and patched OpenSSL server

 
 

-The initial connection suceeds but client renegotiation is denied with a
-B<no_renegotiation> warning alert if TLS v1.0 is used or a fatal
+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.
 
 B<handshake_failure> alert in SSL v3.0.
 

-If the patched 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 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.
 
 If the option B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> is set then
 renegotiation B<always> succeeds.


@@ -263,32 +244,42 @@ B<NB:> a bug in OpenSSL clients earlier than 0.9.8m (all of which are
 unpatched) will result in the connection hanging if it receives a
 B<no_renegotiation> alert. OpenSSL versions 0.9.8m and later will regard
 a B<no_renegotiation> alert as fatal and respond with a fatal
 unpatched) will result in the connection hanging if it receives a
 B<no_renegotiation> alert. OpenSSL versions 0.9.8m and later will regard
 a B<no_renegotiation> alert as fatal and respond with a fatal

-B<handshake_failure> alert.
+B<handshake_failure> alert. This is because the OpenSSL API currently has
+no provision to indicate to an application that a renegotiation attempt
+was refused.
+
+=head2 Patched OpenSSL client and unpatched server.

 
 

-=head2 Patched 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.

 
 

-If the option B<SSL_OP_LEGACY_SERVER_CONNECT> is set then initial connections
-to unpatched servers succeed. This option is currently set by default even
+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
 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.
+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.
 
 
 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.
 

-Applications that want to ensure they can connect to unpatched servers should
-always B<set> B<SSL_OP_LEGACY_SERVER_CONNECT>
+OpenSSL client applications wishing to ensure they can connect to unpatched
+servers should always B<set> B<SSL_OP_LEGACY_SERVER_CONNECT>

 
 

-Applications that want to ensure they can B<not> connect to unpatched servers
-(and thus avoid any security issues) should always B<clear>
+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().
 
 B<SSL_OP_LEGACY_SERVER_CONNECT> using SSL_CTX_clear_options() or
 SSL_clear_options().
 

-The function SSL_get_secure_renegotiation_support() indicates whether the peer
-supports secure renegotiation. 
-
-The deprecated and highly broken SSLv2 protocol does not support secure
-renegotiation at all: its use is B<strongly> discouraged.
+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