Provide a function to test whether we have unread records pending

Also updates SSL_has_pending() to use it. This actually fixes a bug in
SSL_has_pending() which is supposed to return 1 if we have any processed
or unprocessed data sitting in OpenSSL buffers. However it failed to return
1 if we had processed non-application data pending.
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2875)

ssl/record/rec_layer_s3.c

@@ -77,11 +77,24 @@ void RECORD_LAYER_release(RECORD_LAYER *rl)
     SSL3_RECORD_release(rl->rrec, SSL_MAX_PIPELINES);
 }
 
+/* Checks if we have unprocessed read ahead data pending */
 int RECORD_LAYER_read_pending(const RECORD_LAYER *rl)
 {
     return SSL3_BUFFER_get_left(&rl->rbuf) != 0;
 }
 
+/* Checks if we have decrypted unread record data pending */
+int RECORD_LAYER_processed_read_pending(const RECORD_LAYER *rl)
+{
+    size_t curr_rec = 0, num_recs = RECORD_LAYER_get_numrpipes(rl);
+    const SSL3_RECORD *rr = rl->rrec;
+
+    while (curr_rec < num_recs && SSL3_RECORD_is_read(&rr[curr_rec]))
+        curr_rec++;
+
+    return curr_rec < num_recs;
+}
+
 int RECORD_LAYER_write_pending(const RECORD_LAYER *rl)
 {
     return (rl->numwpipes > 0)

ssl/record/record.h

@@ -207,6 +207,7 @@ void RECORD_LAYER_init(RECORD_LAYER *rl, SSL *s);
 void RECORD_LAYER_clear(RECORD_LAYER *rl);
 void RECORD_LAYER_release(RECORD_LAYER *rl);
 int RECORD_LAYER_read_pending(const RECORD_LAYER *rl);
+int RECORD_LAYER_processed_read_pending(const RECORD_LAYER *rl);
 int RECORD_LAYER_write_pending(const RECORD_LAYER *rl);
 void RECORD_LAYER_reset_read_sequence(RECORD_LAYER *rl);
 void RECORD_LAYER_reset_write_sequence(RECORD_LAYER *rl);

ssl/ssl_lib.c

@@ -1323,7 +1323,7 @@ int SSL_has_pending(const SSL *s)
      * data. That data may not result in any application data, or we may fail
      * to parse the records for some reason.
      */
-    if (SSL_pending(s))
+    if (RECORD_LAYER_processed_read_pending(&s->rlayer))
         return 1;
 
     return RECORD_LAYER_read_pending(&s->rlayer);