Unix System III login.c

/*
 * login [ name ]
 */

#include <sys/types.h>
#include <sgtty.h>
#include <utmp.h>
#include <signal.h>
#include <pwd.h>
#include <stdio.h>
#include <sys/stat.h>
#define SCPYN(a, b)     strncpy(a, b, sizeof(a))

char    maildir[30] =   "/usr/spool/mail/";
struct  passwd nouser = {"", "nope"};
struct  sgttyb ttyb;
struct  utmp utmp;
char    minusnam[16] = "-";
char    homedir[64] = "HOME=";
char    *envinit[] = {homedir, "PATH=:/bin:/usr/bin", 0};
struct  passwd *pwd;

struct  passwd *getpwnam();
char    *strcat();
int     setpwent();
char    *ttyname();
char    *crypt();
char    *getpass();
char    *rindex(), *index();
extern  char **environ;

main(argc, argv)
char **argv;
{
        register char *namep;
        int t, f, c;
        char *ttyn;

        alarm(60);
        signal(SIGQUIT, SIG_IGN);
        signal(SIGINT, SIG_IGN);
        nice(-100);
        nice(20);
        nice(0);
        gtty(0, &ttyb);
        ttyb.sg_erase = '#';
        ttyb.sg_kill = '@';
        stty(0, &ttyb);
        for (t=3; t<20; t++)
                close(t);
        ttyn = ttyname(0);
        if (ttyn==0)
                ttyn = "/dev/tty??";

    loop:
        SCPYN(utmp.ut_name, "");
        if (argc>1) {
                SCPYN(utmp.ut_name, argv[1]);
                argc = 0;
        }
        while (utmp.ut_name[0] == '\0') {
                namep = utmp.ut_name;
                printf("login: ");
                while ((c = getchar()) != '\n') {
                        if(c == ' ')
                                c = '_';
                        if (c == EOF)
                                exit(0);
                        if (namep < utmp.ut_name+8)
                                *namep++ = c;
                }
        }
        setpwent();
        if ((pwd = getpwnam(utmp.ut_name)) == NULL)
                pwd = &nouser;
        endpwent();
        if (*pwd->pw_passwd != '\0') {
                namep = crypt(getpass("Password:"),pwd->pw_passwd);
                if (strcmp(namep, pwd->pw_passwd)) {
                        printf("Login incorrect\n");
                        goto loop;
                }
        }
        if(chdir(pwd->pw_dir) < 0) {
                printf("No directory\n");
                goto loop;
        }
        time(&utmp.ut_time);
        t = ttyslot();
        if (t>0 && (f = open("/etc/utmp", 1)) >= 0) {
                lseek(f, (long)(t*sizeof(utmp)), 0);
                SCPYN(utmp.ut_line, index(ttyn+1, '/')+1);
                write(f, (char *)&utmp, sizeof(utmp));
                close(f);
        }
        if (t>0 && (f = open("/usr/adm/wtmp", 1)) >= 0) {
                lseek(f, 0L, 2);
                write(f, (char *)&utmp, sizeof(utmp));
                close(f);
        }
        chown(ttyn, pwd->pw_uid, pwd->pw_gid);
        setgid(pwd->pw_gid);
        setuid(pwd->pw_uid);
        if (*pwd->pw_shell == '\0')
                pwd->pw_shell = "/bin/sh";
        environ = envinit;
        strncat(homedir, pwd->pw_dir, sizeof(homedir)-6);
        if ((namep = rindex(pwd->pw_shell, '/')) == NULL)
                namep = pwd->pw_shell;
        else
                namep++;
        strcat(minusnam, namep);
        alarm(0);
        umask(02);
        showmotd();
        strcat(maildir, pwd->pw_name);
        if(access(maildir,4)==0) {
                struct stat statb;
                stat(maildir, &statb);
                if (statb.st_size)
                        printf("You have mail.\n");
        }
        signal(SIGQUIT, SIG_DFL);
        signal(SIGINT, SIG_DFL);
        execlp(pwd->pw_shell, minusnam, 0);
        printf("No shell\n");
        exit(0);
}

int     stopmotd;
catch()
{
        signal(SIGINT, SIG_IGN);
        stopmotd++;
}

showmotd()
{
        FILE *mf;
        register c;

        signal(SIGINT, catch);
        if((mf = fopen("/etc/motd","r")) != NULL) {
                while((c = getc(mf)) != EOF && stopmotd == 0)
                        putchar(c);
                fclose(mf);
        }
        signal(SIGINT, SIG_IGN);
}