* can be fully instantiated with IMPLEMENT_DYNAMIC_CHECK_FN(). */
typedef unsigned long (*dynamic_v_check_fn)(unsigned long ossl_version);
#define IMPLEMENT_DYNAMIC_CHECK_FN() \
+ OPENSSL_EXPORT unsigned long v_check(unsigned long v); \
OPENSSL_EXPORT unsigned long v_check(unsigned long v) { \
if(v >= OSSL_DYNAMIC_OLDEST) return OSSL_DYNAMIC_VERSION; \
return 0; }
typedef int (*dynamic_bind_engine)(ENGINE *e, const char *id,
const dynamic_fns *fns);
#define IMPLEMENT_DYNAMIC_BIND_FN(fn) \
+ OPENSSL_EXPORT \
+ int bind_engine(ENGINE *e, const char *id, const dynamic_fns *fns);
OPENSSL_EXPORT \
int bind_engine(ENGINE *e, const char *id, const dynamic_fns *fns) { \
if(ENGINE_get_static_state() == fns->static_state) goto skip_cbs; \
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<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>.
+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<no_renegotiation> 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<no_renegotiation> warning alert if TLS v1.0 is used or a fatal
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.
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 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
-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<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().
-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.
+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<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> is set.
=head1 RETURN VALUES