Remove support for rlogind in login(1), that is, remove the '-r' flag

The "quick hack" finally disappeared.  Probably nobody noticed.  ;)
(See the changes in <configure.ac> for the context of this pun.)

Probably everybody uses SSH these days for remote login.  Let's remove
this insecure method.

Closes: <https://github.com/shadow-maint/shadow/issues/992>
Reviewed-by: dkwo <nicolopiazzalunga@gmail.com>
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Michael Vetter <jubalh@iodoru.org>
Cc: Sam James <sam@gentoo.org>
Cc: Benedikt Brinkmann <datacobra@thinkbot.de>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

lib/Makefile.am

@@ -119,7 +119,6 @@ libshadow_la_SOURCES = \
 	pwdcheck.c \
 	pwmem.c \
 	remove_tree.c \
-	rlogin.c \
 	root_flag.c \
 	run_part.h \
 	run_part.c \

lib/prototypes.h

@@ -369,10 +369,6 @@ unsigned long csrand_interval (unsigned long min, unsigned long max);
 /* remove_tree.c */
 extern int remove_tree (const char *root, bool remove_root);
 
-/* rlogin.c */
-extern int do_rlogin(const char *remote_host, char *name, size_t namesize,
-                     char *term, size_t termsize);
-
 /* root_flag.c */
 extern void process_root_flag (const char* short_opt, int argc, char **argv);
 

lib/rlogin.c

@@ -1,135 +0,0 @@
-/*
- * SPDX-FileCopyrightText: 1989 - 1994, Julianne Frances Haugh
- * SPDX-FileCopyrightText: 1996 - 1999, Marek Michałkiewicz
- * SPDX-FileCopyrightText: 2003 - 2005, Tomasz Kłoczko
- * SPDX-FileCopyrightText: 2007 - 2008, Nicolas François
- *
- * SPDX-License-Identifier: BSD-3-Clause
- */
-
-#include <config.h>
-
-#ifdef RLOGIN
-
-#ident "$Id$"
-
-#include "prototypes.h"
-#include "defines.h"
-#include <stdio.h>
-#include <pwd.h>
-#include <netdb.h>
-
-#include "atoi/str2i.h"
-
-
-static struct {
-	int spd_name;
-	int spd_baud;
-} speed_table[] =
-{
-	{ B50, 50},
-	{ B75, 75},
-	{ B110, 110},
-	{ B134, 134},
-	{ B150, 150},
-	{ B200, 200},
-	{ B300, 300},
-	{ B600, 600},
-	{ B1200, 1200},
-	{ B1800, 1800},
-	{ B2400, 2400},
-	{ B4800, 4800},
-	{ B9600, 9600},
-	{ B19200, 19200},
-	{ B38400, 38400},
-	{ -1, -1}
-};
-
-
-static void
-get_remote_string(char *buf, size_t size)
-{
-	for (;;) {
-		if (read (0, buf, 1) != 1) {
-			exit (EXIT_FAILURE);
-		}
-		if ('\0' == *buf) {
-			return;
-		}
-		--size;
-		if (size > 0) {
-			++buf;
-		}
-	}
-	/*NOTREACHED*/
-}
-
-
-int
-do_rlogin(const char *remote_host, char *name, size_t namesize, char *term,
-          size_t termsize)
-{
-	struct passwd *pwd;
-	char remote_name[32];
-	char *cp;
-	unsigned long remote_speed = 9600;
-	int speed_name = B9600;
-	int i;
-	TERMIO termio;
-
-	get_remote_string(remote_name, sizeof(remote_name));
-	get_remote_string(name, namesize);
-	get_remote_string(term, termsize);
-
-	cp = strchr (term, '/');
-	if (NULL != cp) {
-		*cp = '\0';
-		cp++;
-
-		if (str2ul(&remote_speed, cp) == -1)
-			remote_speed = 9600;
-	}
-	for (i = 0;
-	     (   (speed_table[i].spd_baud != remote_speed)
-	      && (speed_table[i].spd_name != -1));
-	     i++);
-
-	if (-1 != speed_table[i].spd_name) {
-		speed_name = speed_table[i].spd_name;
-	}
-
-	/*
-	 * Put the terminal in cooked mode with echo turned on.
-	 */
-
-	GTTY (0, &termio);
-	termio.c_iflag |= ICRNL | IXON;
-	termio.c_oflag |= OPOST | ONLCR;
-	termio.c_lflag |= ICANON | ECHO | ECHOE;
-#ifdef CBAUD
-	termio.c_cflag = (termio.c_cflag & ~CBAUD) | speed_name;
-#else
-	termio.c_cflag = (termio.c_cflag) | speed_name;
-#endif
-	STTY (0, &termio);
-
-	pwd = getpwnam (name); /* local, no need for xgetpwnam */
-	if (NULL == pwd) {
-		return 0;
-	}
-
-	/*
-	 * ruserok() returns 0 for success on modern systems, and 1 on
-	 * older ones.  If you are having trouble with people logging
-	 * in without giving a required password, THIS is the culprit -
-	 * go fix the #define in config.h.
-	 */
-
-#ifndef	RUSEROK
-	return 0;
-#else
-	return ruserok (remote_host, pwd->pw_uid == 0,
-			remote_name, name) == RUSEROK;
-#endif
-}
-#endif				/* RLOGIN */