cli: ignore PAGER when escalating privileges

nmcli typically doesn't run setuid, nor uses file capabilities or is labelled
for a SELinux domain trainsition upon execution.

But in case anyone has any reason to do that, we should follow good
security practices and not exec whatever is set in the environment.

clients/cli/utils.c

@@ -29,6 +29,7 @@
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
+#include <sys/auxv.h>
 #include <sys/prctl.h>
 
 #include "nm-client-utils.h"
@@ -1489,7 +1490,8 @@ nmc_terminal_spawn_pager (const NmcConfig *nmc_config)
 	    || nm_cli.pager_pid > 0
 	    || nmc_config->print_output == NMC_PRINT_TERSE
 	    || !use_colors (nmc_config->use_colors)
-	    || g_strcmp0 (pager, "") == 0)
+	    || g_strcmp0 (pager, "") == 0
+	    || getauxval (AT_SECURE))
 		return;
 
 	if (pipe (fd) == -1) {