dowjones@imp.com (Joachim Astel) (04/29/91)
This is a workaround for the SCO UNIX SysV R3.2 ct-bug. The following program
"callback" takes a phone number as an argument and calls back the specified
number at a fixed speed. Note my WARNING in callback.c, which reads that EVERY
person on the system can do a callback (because the system runs setuid root).
It uses /etc/init which can handle the correct permissions and so on.
You may feel free to modify the sources, but don't blame me with them. :-)
The program was a quick one, so I do not make gurantees for anything.
To make it run, you must do the following:
1. Unshar the following shar-archive
2. edit the Makefile to your personal needs
3. read the comments at the beginning of callback.c, and modify the "#defines"
to your personal needs (baudrate in CT_CMDSTRING, etc.)
4. type ("make" and) "make install" at your shell-prompt
5. edit the /etc/inittab file and add an entry for /usr/bin/callout (this
is mentioned in 'detail' at the beginning of callback.c)
Here we go...
--------------------------------- cut here ------------------------------------
:
# This is a shell archive, meaning:
# 1. Remove everything above the : line.
# 2. Save the resulting text in a file.
# 3. Execute the file with /bin/sh (not csh) to create:
# callback.c
# Makefile
# This archive created: Mon Apr 29 02:12:26 1991 by dowjones@impch.imp.com
export PATH; PATH=/bin:/usr/bin:$PATH
if test -f 'callback.c'
then
echo shar: "will not over-write existing file 'callback.c'"
else
sed 's/^X//' << \SHAR_EOF > 'callback.c'
X/*
X * callback.c - Copyright (C) 1991 by Joachim Astel (dowjones@jattmp.imp.com)
X *
X * WARNING: the program runs as -rws--x--x root (suid-bit set for root),
X * so EVERY person on the system can make the unix system to call
X * him/her back. USE IT ON YOUR OWN RISK.
X *
X * This program fetches superuser-permissions and creates a temporary
X * shell-script "CALL_FILE" with a "sleep 10" and "ct" command in it.
X * Afterwards, an "init"-command is executed, and the shell script is
X * activated from init as far as there is an appropriate line entry in
X * /etc/inittab, like the following:
X *
X * "cbc:c:once:/usr/bin/callout" (without quotation marks, of course)
X * ^ ^^^^^^^^^^^^^^^^ Must be the same as in #define CALL_FILE
X * ^
X * if you have already an entry "c" in use, change the defined
X * INITTAB_ID (see below) to "a" or "b"
X *
X * It works under SCO UNIX SysV R3.2, which has problems with its C2-system
X * if you try to execute "ct" directly.
X *
X * BUGS: the error handling could be better. All in all, the program was a
X * a quick hack. I got reports from some users that this programm did
X * not call back at some time. But that effect was non-reproduceable.
X */
X
X#include <stdio.h>
X#include <signal.h>
X#include <time.h>
X#include <pwd.h>
X
X/* You may feel free to change the following defines */
X
X#define LOG_FILE "/usr/adm/callback"
X#define CT_CMDSTRING "ct -s 2400 %s\n" /* (%s: phone-number.) */
X#define CALL_FILE "/usr/bin/callout" /* must be mentioned in /etc/inittab */
X#define INITTAB_ID "c" /* "slot" in /etc/inittab */
X#define NOTE \
X "Please hang up now and reconfigure your modem to auto-answer mode."
X
X#ifndef GETLUID
X#define getluid getuid
X#endif
X
Xchar *Prgrm;
X
X#define SAME 0 /* for strcmp */
X
X/* return username of specific id */
Xchar *username(id)
X int id;
X{
X struct passwd *pwd;
X
X setpwent(); /* rewind passwd file */
X if ((pwd = getpwuid(id)) == NULL) {
X fprintf(stderr, "%s: Unknown user-id: %d\n", Prgrm, id);
X exit(1);
X }
X endpwent(); /* close passwd file */
X return pwd->pw_name;
X}
X
Xmain(argc, argv)
X int argc;
X char **argv;
X{
X FILE *call_file, *log_file;
X char *phone_number;
X int pid;
X
X Prgrm = *argv;
X
X if (argc != 2) {
X fprintf(stderr, "Usage: %s phone-number\n", Prgrm);
X exit(0);
X }
X phone_number = argv[1];
X
X if (!(pid = fork())) { /* Child-process */
X setgid(0); setuid(0); /* get root permissions */
X
X if ((call_file = fopen(CALL_FILE, "w")) == NULL) {
X fprintf(stderr, "Error: Cannot open %s\n", CALL_FILE);
X kill(pid, 9); /* don't let parent process hangup */
X exit(1); /* abort program */
X }
X fprintf(call_file, "sleep 10\n");
X fprintf(call_file, CT_CMDSTRING, phone_number);
X fclose(call_file);
X chmod(CALL_FILE, 0755);
X
X close(0); close(1); close(2); /* ignore signals etc. */
X signal(SIGHUP, SIG_IGN);
X
X if ((log_file = fopen(LOG_FILE, "w+")) != NULL) {
X time_t t;
X time(&t);
X fprintf(log_file, "%s: %s %s\n", username(getluid()),
X phone_number, ctime(&t));
X fclose(log_file);
X }
X execl("/etc/init", "call-back", INITTAB_ID, NULL);
X /* on error... */
X fprintf(stderr, "Error: Cannot execute init\n");
X kill(pid, 9); /* don't let parent-process hangup the line */
X exit(1); /* abort program */
X }
X}
SHAR_EOF
fi
if test -f 'Makefile'
then
echo shar: "will not over-write existing file 'Makefile'"
else
sed 's/^X//' << \SHAR_EOF > 'Makefile'
X# Makefile for "callback.c"
X
XCC = cc
XBINFILE = callback
XINSTALLPATH = /usr/bin
X
XOBJECTS = callback.o
X
Xall: $(BINFILE)
X @echo "Now start \"make install\""
X
X$(BINFILE): $(OBJECTS)
X $(CC) $(CFLAGS) -o $(@) $(OBJECTS)
X
Xinstall: $(BINFILE)
X cp $(BINFILE) $(INSTALLPATH)
X strip $(INSTALLPATH)/$(BINFILE)
X chmod 4111 $(INSTALLPATH)/$(BINFILE)
X chgrp bin $(INSTALLPATH)/$(BINFILE)
X chown root $(INSTALLPATH)/$(BINFILE)
X
Xclean:
X -rm -f *.o core
X
Xclobber:
X -rm -f *.o core $(BINFILE)
SHAR_EOF
fi
exit 0
# End of shell archive
--
Joachim Astel, E-MAIL: dowjones@jattmp.imp.com, dowjones@jattmp.nbg.sub.org