Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!ll-xn!mit-eddie!oberon.lcs.mit.edu!billw
From: billw@oberon.lcs.mit.edu (Bill Wisner)
Newsgroups: comp.sources.bugs
Subject: Problem in Dan Heller's "dots" game
Message-ID: <7765@eddie.MIT.EDU>
Date: 30 Dec 87 04:49:17 GMT
Sender: uucp@eddie.MIT.EDU
Reply-To: billw@oberon.lcs.mit.edu (Bill Wisner)
Organization: MIT Laboratory for Computer Science
Lines: 63

Due to a problem with the format of /etc/utmp, dots can't handle 2-player
games against someone with an eight-letter username. The following replacement
for findem.c alleviates the problem.
-- (cut here)
/* findem.c   find the login of the person we wanna play */

#include "dots.h"
#include <sys/stat.h>
#include <sgtty.h>
#include <utmp.h>

#define UTMP  		"/etc/utmp"

struct utmp utmp_buf;
struct stat stat_buf;
struct sgttyb sgtty_buf;

int fd;

findem(argc, argv)
char **argv;
{
    char *ttyname(), to_tty[13], *tmp_name;
    register char *login = argv[2], *where = "", *ourtty = ttyname(0) + 5;
    register FILE *recipient;

    if (argc > 3)
	where = argv[3];
    if (!strcmp(where, ourtty)) {
	fprintf(stderr, "You can't play yourself.\n");
	return 0;
    }
    if ((fd = open(UTMP, 0)) == -1) {
	perror(UTMP);
	return 0;
    }

    while (read(fd, (char *) &utmp_buf, sizeof(utmp_buf)))
	if (!strncmp(utmp_buf.ut_name, login, 8) &&
	   (*where && !strcmp(utmp_buf.ut_line, where) ||
	   (!*where && strcmp(where, ourtty))))
		break;

    (void) close(fd);
    if (strncmp(login, utmp_buf.ut_name, 8)) {
	fprintf(stderr, "%s is not logged in.", login);
	return 0;
    }
    if (*where && strcmp(where, utmp_buf.ut_line)) {
	fprintf(stderr, "%s is not logged in on %s.\n", login, where);
	return 0;
    }

    (void) sprintf(to_tty, "/dev/%s", utmp_buf.ut_line);
    if (!(recipient = fopen(to_tty, "w"))) {
	perror(to_tty);
	fprintf(stderr, "%s: Can't ask %s to play.\n", argv[0], argv[2]);
	return 0;
    }
    setuid(getuid());	/* turns off set-uid attribute once tty is opened */
    setgid(getgid());	/* probably isn't necessary most of the time */

    return invite(recipient);
}