Don't send an alert if we've just received one

If the record received is for a version that we don't support, previously we
were sending an alert back. However if the incoming record already looks
like an alert then probably we shouldn't do that. So suppress an outgoing
alert if it looks like we've got one incoming.

Reviewed-by: Kurt Roeckx <kurt@openssl.org>

1 files changed, 12 insertions, 1 deletions

diff --git a/ssl/record/ssl3_record.c b/ssl/record/ssl3_record.c
index 5070bc3..bae9490 100644
--- a/ssl/record/ssl3_record.c
+++ b/ssl/record/ssl3_record.c
@@ -268,11 +268,22 @@ int ssl3_get_record(SSL *s)
             if (!s->first_packet && version != s->version) {
                 SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_WRONG_VERSION_NUMBER);
                 if ((s->version & 0xFF00) == (version & 0xFF00)
-                    && !s->enc_write_ctx && !s->write_hash)
+                    && !s->enc_write_ctx && !s->write_hash) {
+                    if (rr->type == SSL3_RT_ALERT) {
+                        /*
+                         * The record is using an incorrect version number, but
+                         * what we've got appears to be an alert. We haven't
+                         * read the body yet to check whether its a fatal or
+                         * not - but chances are it is. We probably shouldn't
+                         * send a fatal alert back. We'll just end.
+                         */
+                         goto err;
+                    }
                     /*
                      * Send back error using their minor version number :-)
                      */
                     s->version = (unsigned short)version;
+                }
                 al = SSL_AD_PROTOCOL_VERSION;
                 goto f_err;
             }