提交 c2c49969 编写于 作者: D Dr. Stephen Henson

Allow renegotiation if SSL_OP_LEGACY_SERVER_CONNECT is set as well as

initial connection to unpatched servers. There are no additional security
concerns in doing this as clients don't see renegotiation during an
attack anyway.
上级 47e0a1c3
...@@ -926,7 +926,7 @@ ...@@ -926,7 +926,7 @@
[Steve Henson] [Steve Henson]
*) Add option SSL_OP_LEGACY_SERVER_CONNECT which will allow clients to *) Add option SSL_OP_LEGACY_SERVER_CONNECT which will allow clients to
connect (but not renegotiate) with servers which do not support RI. connect and renegotiate with servers which do not support RI.
Until RI is more widely deployed this option is enabled by default. Until RI is more widely deployed this option is enabled by default.
[Steve Henson] [Steve Henson]
......
...@@ -237,7 +237,7 @@ OpenSSL 0.9.8m and later always attempts to use secure renegotiation as ...@@ -237,7 +237,7 @@ OpenSSL 0.9.8m and later always attempts to use secure renegotiation as
described in RFC5746. This counters the prefix attack described in described in RFC5746. This counters the prefix attack described in
CVE-2009-3555 and elsewhere. CVE-2009-3555 and elsewhere.
The deprecated and highly broken SSLv2 protocol does not support secure The deprecated and highly broken SSLv2 protocol does not support
renegotiation at all: its use is B<strongly> discouraged. renegotiation at all: its use is B<strongly> discouraged.
This attack has far reaching consequences which application writers should be This attack has far reaching consequences which application writers should be
...@@ -276,10 +276,14 @@ was refused. ...@@ -276,10 +276,14 @@ was refused.
=head2 Patched OpenSSL client and unpatched server. =head2 Patched OpenSSL client and unpatched server.
If the option B<SSL_OP_LEGACY_SERVER_CONNECT> is set then initial connections If the option B<SSL_OP_LEGACY_SERVER_CONNECT> is set then initial connections
between patched OpenSSL clients and unpatched servers succeed. This option and renegotiation between patched OpenSSL clients and unpatched servers
is currently set by default even though it has security implications: otherwise succeeds.
it would be impossible to connect to unpatched servers (i.e. all of them
initially) and this is clearly not acceptable. 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. 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 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. B<not> be set by default in a future version of OpenSSL.
...@@ -292,10 +296,9 @@ unpatched servers (and thus avoid any security issues) should always B<clear> ...@@ -292,10 +296,9 @@ unpatched servers (and thus avoid any security issues) should always B<clear>
B<SSL_OP_LEGACY_SERVER_CONNECT> using SSL_CTX_clear_options() or B<SSL_OP_LEGACY_SERVER_CONNECT> using SSL_CTX_clear_options() or
SSL_clear_options(). SSL_clear_options().
Renegotiation between a patched OpenSSL client and unpatched server follows As in the previous case if the option
the same scheme as between an unpatched client and a patched OpenSSL server: B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> is set then renegotiation
i.e. it is not permitted unless the option B<always> succeeds.
B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> is set.
=head1 RETURN VALUES =head1 RETURN VALUES
......
...@@ -1157,8 +1157,8 @@ int ssl_parse_serverhello_tlsext(SSL *s, unsigned char **p, unsigned char *d, in ...@@ -1157,8 +1157,8 @@ int ssl_parse_serverhello_tlsext(SSL *s, unsigned char **p, unsigned char *d, in
* which doesn't support RI so for the immediate future tolerate RI * which doesn't support RI so for the immediate future tolerate RI
* absence on initial connect only. * absence on initial connect only.
*/ */
if (!renegotiate_seen && if (!renegotiate_seen
(s->new_session || !(s->options & SSL_OP_LEGACY_SERVER_CONNECT)) && !(s->options & SSL_OP_LEGACY_SERVER_CONNECT)
&& !(s->options & SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION)) && !(s->options & SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION))
{ {
*al = SSL_AD_HANDSHAKE_FAILURE; *al = SSL_AD_HANDSHAKE_FAILURE;
......
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