From 5a6ae115f86024805a43193d7ab5756b9d74c58f Mon Sep 17 00:00:00 2001 From: "Dr. Stephen Henson" Date: Wed, 27 Jan 2010 18:53:49 +0000 Subject: reword RI description --- doc/ssl/SSL_CTX_set_options.pod | 51 +++++++++++++++++++++++------------------ 1 file changed, 29 insertions(+), 22 deletions(-) (limited to 'doc') diff --git a/doc/ssl/SSL_CTX_set_options.pod b/doc/ssl/SSL_CTX_set_options.pod index 7ffe948112..a878a6af6d 100644 --- a/doc/ssl/SSL_CTX_set_options.pod +++ b/doc/ssl/SSL_CTX_set_options.pod @@ -237,24 +237,30 @@ 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. +The deprecated and highly broken SSLv2 protocol does not support secure +renegotiation at all: its use is B 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. A server not supporting secure renegotiation is referred to as I. +The following sections describe the operations permitted by OpenSSL's secure +renegotiation implementation. + =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 warning alert if TLS v1.0 is used or a fatal +The initial connection suceeds but client renegotiation is denied by the +server with a B warning alert if TLS v1.0 is used or a fatal B alert in SSL v3.0. -If the patched server attempts to renegotiate a fatal B -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 alert is sent. This is because the server code may be +unaware of the unpatched nature of the client. If the option B is set then renegotiation B succeeds. @@ -263,32 +269,33 @@ B 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 alert. OpenSSL versions 0.9.8m and later will regard a B alert as fatal and respond with a fatal -B alert. +B alert. This is because the OpenSSL API currently has +no provision to indicate to an application that a renegotiation attempt +was refused. -=head2 Patched client and unpatched server. +=head2 Patched OpenSSL client and unpatched server. If the option B is set then initial connections -to unpatched servers succeed. This option 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. +between patched OpenSSL clients and unpatched servers succeed. This option +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. As more servers become patched the option B will B be set by default in a future version of OpenSSL. -Applications that want to ensure they can connect to unpatched servers should -always B B +OpenSSL client applications wishing to ensure they can connect to unpatched +servers should always B B -Applications that want to ensure they can B connect to unpatched servers -(and thus avoid any security issues) should always B +OpenSSL client applications that want to ensure they can B connect to +unpatched servers (and thus avoid any security issues) should always B B 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 discouraged. +Renegotiation between a patched OpenSSL client and unpatched server follows +the same scheme as between an unpatched client and a patched OpenSSL server: +i.e. it is not permitted unless the option +B is set. =head1 RETURN VALUES -- cgit v1.2.3