Never expose ssl->bbio in the public API.

This is adapted from BoringSSL commit 2f87112b963.

This fixes a number of bugs where the existence of bbio was leaked in the
public API and broke things.

- SSL_get_wbio returned the bbio during the handshake. It must always return
  the BIO the consumer configured. In doing so, some internal accesses of
  SSL_get_wbio should be switched to ssl->wbio since those want to see bbio.

- The logic in SSL_set_rfd, etc. (which I doubt is quite right since
  SSL_set_bio's lifetime is unclear) would get confused once wbio got
  wrapped. Those want to compare to SSL_get_wbio.

- If SSL_set_bio was called mid-handshake, bbio would get disconnected and
  lose state. It forgets to reattach the bbio afterwards. Unfortunately,
  Conscrypt does this a lot. It just never ended up calling it at a point
  where the bbio would cause problems.

- Make more explicit the invariant that any bbio's which exist are always
  attached. Simplify a few things as part of that.

RT#4572

Reviewed-by: Richard Levitte <levitte@openssl.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/ssl/statem/statem_dtls.c b/ssl/statem/statem_dtls.c
index 5929113..31ae1cb 100644
--- a/ssl/statem/statem_dtls.c
+++ b/ssl/statem/statem_dtls.c
@@ -182,7 +182,7 @@ int dtls1_do_write(SSL *s, int type)
             }
         }
 
-        used_len = BIO_wpending(SSL_get_wbio(s)) + DTLS1_RT_HEADER_LENGTH
+        used_len = BIO_wpending(s->wbio) + DTLS1_RT_HEADER_LENGTH
             + mac_size + blocksize;
         if (s->d1->mtu > used_len)
             curr_mtu = s->d1->mtu - used_len;
@@ -193,7 +193,7 @@ int dtls1_do_write(SSL *s, int type)
             /*
              * grr.. we could get an error if MTU picked was wrong
              */
-            ret = BIO_flush(SSL_get_wbio(s));
+            ret = BIO_flush(s->wbio);
             if (ret <= 0) {
                 s->rwstate = SSL_WRITING;
                 return ret;
@@ -1120,7 +1120,7 @@ dtls1_retransmit_message(SSL *s, unsigned short seq, int *found)
 
     s->d1->retransmitting = 0;
 
-    (void)BIO_flush(SSL_get_wbio(s));
+    (void)BIO_flush(s->wbio);
     return ret;
 }