Merge origin/maint-0.2.2 for 6007_strict

This code shouldn't have any effect in 0.2.3, since we already accept
(and handle) data received while we are expecting a renegotiation.
(That's because the 0.2.3.x handshake _does_ have data there instead of
the renegotiation.)

I'm leaving it in anyway, since if it breaks anything, we'll want it
broken in master too so we can find out about it.  I added an XXX023
comment so that we can come back later and fix that.

changes/bug6007

@@ -0,0 +1,5 @@
+  o Major bugfixes (security):
+    - When waiting for a client to renegotiate, don't allow it to add
+      any bytes to the input buffer. This fixes a DoS issue. Fix for
+      bugs 6007 and 5934; bugfix on 0.2.0.20-rc.
+

src/or/connection_or.c

@@ -358,7 +358,12 @@ connection_or_reached_eof(or_connection_t *conn)
 int
 connection_or_process_inbuf(or_connection_t *conn)
 {
-  int ret;
+  /** Don't let the inbuf of a nonopen OR connection grow beyond this many
+   * bytes: it's either a broken client, a non-Tor client, or a DOS
+   * attempt. */
+#define MAX_OR_INBUF_WHEN_NONOPEN 0
+
+  int ret = 0;
   tor_assert(conn);
 
   switch (conn->_base.state) {
@@ -389,8 +394,27 @@ connection_or_process_inbuf(or_connection_t *conn)
     case OR_CONN_STATE_OR_HANDSHAKING_V3:
       return connection_or_process_cells_from_inbuf(conn);
     default:
-      return 0; /* don't do anything */
+      break; /* don't do anything */
+  }
+
+  /* This check was necessary with 0.2.2, when the TLS_SERVER_RENEGOTIATING
+   * check would otherwise just let data accumulate.  It serves no purpose
+   * in 0.2.3.
+   *
+   * XXX023 Remove this check once we verify that the above paragraph is
+   * 100% true. */
+  if (buf_datalen(conn->_base.inbuf) > MAX_OR_INBUF_WHEN_NONOPEN) {
+    log_fn(LOG_PROTOCOL_WARN, LD_NET, "Accumulated too much data (%d bytes) "
+	   "on nonopen OR connection %s %s:%u in state %s; closing.",
+	   (int)buf_datalen(conn->_base.inbuf),
+	   connection_or_nonopen_was_started_here(conn) ? "to" : "from",
+	   conn->_base.address, conn->_base.port,
+	   conn_state_to_string(conn->_base.type, conn->_base.state));
+    connection_mark_for_close(TO_CONN(conn));
+    ret = -1;
   }
+
+  return ret;
 }
 
 /** When adding cells to an OR connection's outbuf, keep adding until the