nss: Remove cryptographic key support from nss_files, nss_nis, nss_ni…

…splus

The interface has hard-coded buffer sizes and is therefore tied to
DES.  It also does not match current practice where different
services on the same host use different key material.

This change simplifies removal of the sunrpc code.

NEWS

@@ -104,6 +104,12 @@ Deprecated and removed features, and other changes affecting compatibility:
   or contents might be overwritten on subsequent calls in the same thread or
   if the thread is terminated.  It makes strerror MT-safe.
 
+* The "files", "nis" and "nisplus" NSS modules no longer supports the
+  "key" database (used for secure RPC).  The contents of the
+  /etc/publickey file will be ignored, regardless of the settings in
+  /etc/nsswitch.conf.  (This method of storing RPC keys only supported
+  the obsolete and insecure AUTH_DES flavor of secure RPC.)
+
 Changes to build and runtime requirements:
 
 * powerpc64le requires GCC 7.4 or newer.  This is required for supporting

nis/Makefile

@@ -36,7 +36,7 @@ headers			:= $(wildcard rpcsvc/*.[hx])
 # These are the databases available for the nis (and perhaps later nisplus)
 # service.  This must be a superset of the services in nss.
 databases		= proto service hosts network grp pwd rpc ethers \
-			  spwd netgrp alias publickey
+			  spwd netgrp alias
 
 # Specify rules for the nss_* modules.
 services		:= nis nisplus