Document problem with NULL SSL ciphers and man-in-the-middle attacks.

diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 356a1d295c82157c13334f952662d0fec57149ca..166d86a623cb6a971a5b3a4cab4b9ba250dc1267 100644 (file)
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -1,4 +1,4 @@
-
+
 
 
  Operating System Environment
@@ -1604,7 +1604,10 @@ $ kill -INT `head -1 /usr/local/pgsql/data/postmaster.pid`
    ciphers can be specified in the OpenSSL
    configuration file, you can specify ciphers specifically for use by
    the database server by modifying  in
-   postgresql.conf.
+   postgresql.conf.  It is possible to allow authentication
+   without the overhead of encryption by using NULL-SHA or
+   NULL-MD5 ciphers.  However, a man-in-the-middle could read
+   and pass communications between client and server.