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authorSimon Josefsson <simon@josefsson.org>2010-05-28 09:21:12 +0200
committerSimon Josefsson <simon@josefsson.org>2010-05-28 09:21:12 +0200
commit1d088b700f21f8804d921ae1336f0166cfd628d2 (patch)
treeb1a9c3dd21384f9d9aa2db2e9bd45292409c8aed
parent58604f748d324cce14c58148a6174a88be7e60b4 (diff)
downloadgnutls-1d088b700f21f8804d921ae1336f0166cfd628d2.tar.gz
Update.
-rw-r--r--doc/gnutls.texi50
1 files changed, 28 insertions, 22 deletions
diff --git a/doc/gnutls.texi b/doc/gnutls.texi
index 3dc3b1f177..312bc23a59 100644
--- a/doc/gnutls.texi
+++ b/doc/gnutls.texi
@@ -1262,32 +1262,38 @@ initial negotiation. When the extension is used, the attack is
detected and the session can be terminated. The extension is
specified in @xcite{RFC5746}.
-GnuTLS supports the safe renegotiation extension. By default, GnuTLS
-clients will attempt to negotiate the safe renegotiation extension
-when talking to servers. Also by default, GnuTLS servers will accept
-the extension when presented by clients. However, by default GnuTLS
-client and servers will not refuse renegotiation attempts when the
-extension has not been negotiated, as this would break backwards
-compatibility and cause too much operational problems. We will likely
-reconsider these defaults in the future.
-
-To modify the default behaviour, we have introduced four new priority
+GnuTLS supports the safe renegotiation extension. The default
+behavior is as follows. Clients will attempt to negotiate the safe
+renegotiation extension when talking to servers. Servers will accept
+the extension when presented by clients. Clients and servers will
+permit an initial handshake to complete even when the other side does
+not support the safe renegotiation extension. Clients and servers
+will refuse renegotiation attempts when the extension has not been
+negotiated.
+
+Note that permitting clients to connect to servers even when the safe
+renegotiation extension is not negotiated open up for some attacks.
+Changing this default behaviour would prevent interoperability against
+the majority of deployed servers out there. We will reconsider this
+default behaviour in the future when more servers have been upgraded.
+Note that it is easy to configure clients to always require the safe
+renegotiation extension from servers (see below on the
+%SAFE_RENEGOTIATION priority string).
+
+To modify the default behaviour, we have introduced some new priority
strings. The priority strings can be used by applications
(@pxref{gnutls_priority_set}) and end users (e.g., @code{--priority}
parameter to @code{gnutls-cli} and @code{gnutls-serv}).
-The @code{%UNSAFE_RENEGOTIATION} priority string requests what is
-today the default behaviour, i.e., that handshakes without the safe
-renegotiation extension is permitted. To make more use of the
-extension, you may provide the @code{%SAFE_RENEGOTIATION} priority
-string. In this mode, clients will require that the server supports
-the extension for the initial handshake, and servers will require that
-the client supports the extension for renegotiated handshakes. If you
-want to make a server refuse even initial handshakes without the safe
-renegotiation extension, use the @code{%INITIAL_SAFE_RENEGOTIATION}
-priority string. It is possible to disable use of the extension
-completely by using the @code{%DISABLE_SAFE_RENEGOTIATION} priority
-string however this is recommended against except for debugging.
+The @code{%UNSAFE_RENEGOTIATION} priority string permits
+(re-)handshakes even when the safe renegotiation extension was not
+negotiated. The @code{%SAFE_RENEGOTIATION} priority string makes
+client and servers require the extension for every handshake.
+
+It is possible to disable use of the extension completely, in both
+clients and servers, by using the @code{%DISABLE_SAFE_RENEGOTIATION}
+priority string however we strongly recommend you to only do this for
+debugging and test purposes.
For applications we have introduced a new API related to safe
renegotiation. The @ref{gnutls_safe_renegotiation_status} function is