Don't change version number if session established

When sending an invalid version number alert don't change the
version number to the client version if a session is already
established.

Thanks to Marek Majkowski for additional analysis of this issue.

PR#3191

ssl/s3_pkt.c

diff --git a/ssl/s3_pkt.c b/ssl/s3_pkt.c
index a6fd3bf..c3a061d 100644
--- a/ssl/s3_pkt.c
+++ b/ssl/s3_pkt.c
@@ -348,7 +348,7 @@
 			if (version != s->version)
 				{
 				SSLerr(SSL_F_SSL3_GET_RECORD,SSL_R_WRONG_VERSION_NUMBER);
-                                if ((s->version & 0xFF00) == (version & 0xFF00))
+                                if ((s->version & 0xFF00) == (version & 0xFF00) && !s->enc_write_ctx && !s->write_hash)
                                 	/* Send back error using their minor version number :-) */
 					s->version = (unsigned short)version;
 				al=SSL_AD_PROTOCOL_VERSION;

ssl/s3_srvr.c

diff --git a/ssl/s3_srvr.c b/ssl/s3_srvr.c
index 5d0432f..41a5ba5 100644
--- a/ssl/s3_srvr.c
+++ b/ssl/s3_srvr.c
@@ -978,12 +978,13 @@
 	s->client_version=(((int)p[0])<<8)|(int)p[1];
 	p+=2;
 
-	if ((SSL_IS_DTLS(s) && s->client_version > s->version
-			&& s->method->version != DTLS_ANY_VERSION) ||
-	    (!SSL_IS_DTLS(s) && s->client_version < s->version))
+	if (SSL_IS_DTLS(s)  ?	(s->client_version > s->version &&
+				 s->method->version != DTLS_ANY_VERSION)
+			    :	(s->client_version < s->version))
 		{
 		SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_WRONG_VERSION_NUMBER);
-		if ((s->client_version>>8) == SSL3_VERSION_MAJOR)
+		if ((s->client_version>>8) == SSL3_VERSION_MAJOR &&
+			!s->enc_write_ctx && !s->write_hash)
 			{
 			/* similar to ssl3_get_record, send alert using remote version number */
 			s->version = s->client_version;