Option to set current cert to server certificate.

(cherry picked from commit daddd9a950)

doc/ssl/SSL_CTX_add1_chain_cert.pod

@@ -77,6 +77,14 @@ the first valid certificate or B<SSL_CERT_SET_NEXT> to set the next valid
 certificate after the current certificate. These two operations can be
 used to iterate over all certificates in an B<SSL_CTX> structure.
 
+SSL_set_current_cert() also supports the option B<SSL_CERT_SET_SERVER>.
+If B<ssl> is a server and has sent a certificate to a connected client
+this option sets that certificate to the current certificate and returns 1.
+If the negotiated ciphersuite is anonymous (and thus no certificate will
+be sent) 2 is returned and the current certificate is unchanged. If B<ssl>
+is not a server or a certificate has not been sent 0 is returned and
+the current certificate is unchanged.
+
 All these functions are implemented as macros. Those containing a B<1>
 increment the reference count of the supplied certificate or chain so it must
 be freed at some point after the operation. Those containing a B<0> do

ssl/s3_lib.c

@@ -3432,6 +3432,24 @@ long ssl3_ctrl(SSL *s, int cmd, long larg, void *parg)
 		return ssl_cert_select_current(s->cert, (X509 *)parg);
 
 	case SSL_CTRL_SET_CURRENT_CERT:
+		if (larg == SSL_CERT_SET_SERVER)
+			{
+			CERT_PKEY *cpk;
+			const SSL_CIPHER *cipher;
+			if (!s->server)
+				return 0;
+			cipher = s->s3->tmp.new_cipher;
+			if (!cipher)
+				return 0;
+			/* No certificate for unauthenticated ciphersuites */
+			if (cipher->algorithm_auth & SSL_aNULL)
+				return 2;
+			cpk = ssl_get_server_send_pkey(s);
+			if (!cpk)
+				return 0;
+			s->cert->key = cpk;
+			return 1;
+			}
 		return ssl_cert_set_current(s->cert, larg);
 
 #ifndef OPENSSL_NO_EC

ssl/ssl.h

@@ -1942,6 +1942,7 @@ DECLARE_PEM_rw(SSL_SESSION, SSL_SESSION)
 
 #define SSL_CERT_SET_FIRST			1
 #define SSL_CERT_SET_NEXT			2
+#define SSL_CERT_SET_SERVER			3
 
 #define DTLSv1_get_timeout(ssl, arg) \
 	SSL_ctrl(ssl,DTLS_CTRL_GET_TIMEOUT,0, (void *)arg)

ssl/ssl_lib.c

@@ -2672,6 +2672,8 @@ CERT_PKEY *ssl_get_server_send_pkey(const SSL *s)
 	int i;
 
 	c = s->cert;
+	if (!s->s3 || !s->s3->tmp.new_cipher)
+		return NULL;
 	ssl_set_cert_masks(c, s->s3->tmp.new_cipher);
 
 #ifdef OPENSSL_SSL_DEBUG_BROKEN_PROTOCOL