login.c

Util-linux 软件包包含许多工具。其中比较重要的是加载、卸载、格式化、分区和管理硬盘驱动器

	    int wtmp;

	    if((wtmp = open(_PATH_WTMP, O_APPEND|O_WRONLY)) >= 0) {
		write(wtmp, (char *)&ut, sizeof(ut));
		close(wtmp);
	    }
	}
#else
	/* Probably all this locking below is just nonsense,
	   and the short version is OK as well. */
	{ 
	    int lf, wtmp;
	    if ((lf = open(_PATH_WTMPLOCK, O_CREAT|O_WRONLY, 0660)) >= 0) {
		flock(lf, LOCK_EX);
		if ((wtmp = open(_PATH_WTMP, O_APPEND|O_WRONLY)) >= 0) {
		    write(wtmp, (char *)&ut, sizeof(ut));
		    close(wtmp);
		}
		flock(lf, LOCK_UN);
		close(lf);
	    }
	}
#endif
#endif
    }
    
    dolastlog(quietlog);
    
    chown(ttyn, pwd->pw_uid,
	  (gr = getgrnam(TTYGRPNAME)) ? gr->gr_gid : pwd->pw_gid);
    chmod(ttyn, TTY_MODE);

#ifdef CHOWNVCS
    /* if tty is one of the VC's then change owner and mode of the 
       special /dev/vcs devices as well */
    if (consoletty(0)) {
	chown(vcsn, pwd->pw_uid, (gr ? gr->gr_gid : pwd->pw_gid));
	chown(vcsan, pwd->pw_uid, (gr ? gr->gr_gid : pwd->pw_gid));
	chmod(vcsn, TTY_MODE);
	chmod(vcsan, TTY_MODE);
    }
#endif

    setgid(pwd->pw_gid);
    
#ifdef HAVE_QUOTA
    quota(Q_DOWARN, pwd->pw_uid, (dev_t)-1, 0);
#endif
    
    if (*pwd->pw_shell == '\0')
      pwd->pw_shell = _PATH_BSHELL;
    
    /* preserve TERM even without -p flag */
    {
	char *ep;
	
	if(!((ep = getenv("TERM")) && (termenv = strdup(ep))))
	  termenv = "dumb";
    }
    
    /* destroy environment unless user has requested preservation */
    if (!pflag)
      {
          environ = (char**)malloc(sizeof(char*));
	  memset(environ, 0, sizeof(char*));
      }
    
    setenv("HOME", pwd->pw_dir, 0);      /* legal to override */
    if(pwd->pw_uid)
      setenv("PATH", _PATH_DEFPATH, 1);
    else
      setenv("PATH", _PATH_DEFPATH_ROOT, 1);
    
    setenv("SHELL", pwd->pw_shell, 1);
    setenv("TERM", termenv, 1);
    
    /* mailx will give a funny error msg if you forget this one */
    {
      char tmp[MAXPATHLEN];
      /* avoid snprintf */
      if (sizeof(_PATH_MAILDIR) + strlen(pwd->pw_name) + 1 < MAXPATHLEN) {
	      sprintf(tmp, "%s/%s", _PATH_MAILDIR, pwd->pw_name);
	      setenv("MAIL",tmp,0);
      }
    }
    
    /* LOGNAME is not documented in login(1) but
       HP-UX 6.5 does it. We'll not allow modifying it.
       */
    setenv("LOGNAME", pwd->pw_name, 1);

#ifdef USE_PAM
    {
	int i;
	char ** env = pam_getenvlist(pamh);

	if (env != NULL) {
	    for (i=0; env[i]; i++) {
		putenv(env[i]);
		/* D(("env[%d] = %s", i,env[i])); */
	    }
	}
    }
#endif

#ifdef DO_PS_FIDDLING
    setproctitle("login", username);
#endif
    
    if (!strncmp(tty_name, "ttyS", 4))
      syslog(LOG_INFO, _("DIALUP AT %s BY %s"), tty_name, pwd->pw_name);
    
    /* allow tracking of good logins.
       -steve philp ([e-mail]) */
    
    if (pwd->pw_uid == 0) {
	if (hostname)
	  syslog(LOG_NOTICE, _("ROOT LOGIN ON %s FROM %s"),
		 tty_name, hostname);
	else
	  syslog(LOG_NOTICE, _("ROOT LOGIN ON %s"), tty_name);
    } else {
	if (hostname) 
	  syslog(LOG_INFO, _("LOGIN ON %s BY %s FROM %s"), tty_name, 
		 pwd->pw_name, hostname);
	else 
	  syslog(LOG_INFO, _("LOGIN ON %s BY %s"), tty_name, 
		 pwd->pw_name);
    }
    
    if (!quietlog) {
	motd();

#ifdef DO_STAT_MAIL
	/*
	 * This turns out to be a bad idea: when the mail spool
	 * is NFS mounted, and the NFS connection hangs, the
	 * login hangs, even root cannot login.
	 * Checking for mail should be done from the shell.
	 */
	{
	    struct stat st;
	    char *mail;
	
	    mail = getenv("MAIL");
	    if (mail && stat(mail, &st) == 0 && st.st_size != 0) {
		if (st.st_mtime > st.st_atime)
			printf(_("You have new mail.\n"));
		else
			printf(_("You have mail.\n"));
	    }
	}
#endif
    }
    
    signal(SIGALRM, SIG_DFL);
    signal(SIGQUIT, SIG_DFL);
    signal(SIGTSTP, SIG_IGN);

#ifdef USE_PAM
    /*
     * We must fork before setuid() because we need to call
     * pam_close_session() as root.
     */
    
    childPid = fork();
    if (childPid < 0) {
       int errsv = errno;
       /* error in fork() */
       fprintf(stderr, _("login: failure forking: %s"), strerror(errsv));
       PAM_END;
       exit(0);
    }

    if (childPid) {
       /* parent - wait for child to finish, then cleanup session */
       signal(SIGHUP, SIG_IGN);
       signal(SIGINT, SIG_IGN);
       signal(SIGQUIT, SIG_IGN);
       signal(SIGTSTP, SIG_IGN);
       signal(SIGTTIN, SIG_IGN);
       signal(SIGTTOU, SIG_IGN);

       wait(NULL);
       PAM_END;
       exit(0);
    }

    /* child */
    /*
     * Problem: if the user's shell is a shell like ash that doesnt do
     * setsid() or setpgrp(), then a ctrl-\, sending SIGQUIT to every
     * process in the pgrp, will kill us.
     */

    /* start new session */
    setsid();

    /* make sure we have a controlling tty */
    opentty(ttyn);
    openlog("login", LOG_ODELAY, LOG_AUTHPRIV);	/* reopen */

    /*
     * TIOCSCTTY: steal tty from other process group.
     */
    if (ioctl(0, TIOCSCTTY, 1))
	    syslog(LOG_ERR, _("TIOCSCTTY failed: %m"));
#endif
    signal(SIGINT, SIG_DFL);
    
    /* discard permissions last so can't get killed and drop core */
    if(setuid(pwd->pw_uid) < 0 && pwd->pw_uid) {
	syslog(LOG_ALERT, _("setuid() failed"));
	exit(1);
    }
    
    /* wait until here to change directory! */
    if (chdir(pwd->pw_dir) < 0) {
	printf(_("No directory %s!\n"), pwd->pw_dir);
	if (chdir("/"))
	  exit(0);
	pwd->pw_dir = "/";
	printf(_("Logging in with home = \"/\".\n"));
    }
    
    /* if the shell field has a space: treat it like a shell script */
    if (strchr(pwd->pw_shell, ' ')) {
	buff = malloc(strlen(pwd->pw_shell) + 6);

	if (!buff) {
	    fprintf(stderr, _("login: no memory for shell script.\n"));
	    exit(0);
	}

	strcpy(buff, "exec ");
	strcat(buff, pwd->pw_shell);
	childArgv[childArgc++] = "/bin/sh";
	childArgv[childArgc++] = "-sh";
	childArgv[childArgc++] = "-c";
	childArgv[childArgc++] = buff;
    } else {
	tbuf[0] = '-';
	xstrncpy(tbuf + 1, ((p = rindex(pwd->pw_shell, '/')) ?
			   p + 1 : pwd->pw_shell),
		sizeof(tbuf)-1);
	
	childArgv[childArgc++] = pwd->pw_shell;
	childArgv[childArgc++] = tbuf;
    }

    childArgv[childArgc++] = NULL;

    execvp(childArgv[0], childArgv + 1);

    errsv = errno;

    if (!strcmp(childArgv[0], "/bin/sh"))
	fprintf(stderr, _("login: couldn't exec shell script: %s.\n"),
		strerror(errsv));
    else
	fprintf(stderr, _("login: no shell: %s.\n"), strerror(errsv));

    exit(0);
}

#ifndef USE_PAM
static void
getloginname(void) {
    int ch, cnt, cnt2;
    char *p;
    static char nbuf[UT_NAMESIZE + 1];
    
    cnt2 = 0;
    for (;;) {
	cnt = 0;
	printf(_("\n%s login: "), thishost); fflush(stdout);
	for (p = nbuf; (ch = getchar()) != '\n'; ) {
	    if (ch == EOF) {
		badlogin("EOF");
		exit(0);
	    }
	    if (p < nbuf + UT_NAMESIZE)
	      *p++ = ch;
	    
	    cnt++;
	    if (cnt > UT_NAMESIZE + 20) {
		fprintf(stderr, _("login name much too long.\n"));
		badlogin(_("NAME too long"));
		exit(0);
	    }
	}
	if (p > nbuf) {
	  if (nbuf[0] == '-')
	    fprintf(stderr,
		    _("login names may not start with '-'.\n"));
	  else {
	      *p = '\0';
	      username = nbuf;
	      break;
	  }
	}
	
	cnt2++;
	if (cnt2 > 50) {
	    fprintf(stderr, _("too many bare linefeeds.\n"));
	    badlogin(_("EXCESSIVE linefeeds"));
	    exit(0);
	}
    }
}
#endif

/*
 * Robert Ambrose writes:
 * A couple of my users have a problem with login processes hanging around
 * soaking up pts's.  What they seem to hung up on is trying to write out the
 * message 'Login timed out after %d seconds' when the connection has already
 * been dropped.
 * What I did was add a second timeout while trying to write the message so
 * the process just exits if the second timeout expires.
 */

static void
timedout2(int sig) {
	struct termio ti;
    
	/* reset echo */
	ioctl(0, TCGETA, &ti);
	ti.c_lflag |= ECHO;
	ioctl(0, TCSETA, &ti);
	exit(0);			/* %% */
}

static void
timedout(int sig) {
	signal(SIGALRM, timedout2);
	alarm(10);
	fprintf(stderr, _("Login timed out after %d seconds\n"), timeout);
	signal(SIGALRM, SIG_IGN);
	alarm(0);
	timedout2(0);
}

#ifndef USE_PAM
int
rootterm(char * ttyn)
{ 
    int fd;
    char buf[100],*p;
    int cnt, more = 0;
    
    fd = open(SECURETTY, O_RDONLY);
    if(fd < 0) return 1;
    
    /* read each line in /etc/securetty, if a line matches our ttyline
       then root is allowed to login on this tty, and we should return
       true. */
    for(;;) {
	p = buf; cnt = 100;
	while(--cnt >= 0 && (more = read(fd, p, 1)) == 1 && *p != '\n') p++;
	if(more && *p == '\n') {
	    *p = '\0';
	    if(!strcmp(buf, ttyn)) {
		close(fd);
		return 1;
	    } else
	      continue;
  	} else {
	    close(fd);
	    return 0;
  	}
    }
}
#endif /* !USE_PAM */

jmp_buf motdinterrupt;

void
motd(void) {
    int fd, nchars;
    void (*oldint)(int);
    char tbuf[8192];
    
    if ((fd = open(_PATH_MOTDFILE, O_RDONLY, 0)) < 0)
      return;
    oldint = signal(SIGINT, sigint);
    if (setjmp(motdinterrupt) == 0)
      while ((nchars = read(fd, tbuf, sizeof(tbuf))) > 0)
	write(fileno(stdout), tbuf, nchars);
    signal(SIGINT, oldint);
    close(fd);
}

void
sigint(int sig) {
    longjmp(motdinterrupt, 1);
}

#ifndef USE_PAM				/* PAM takes care of this */
void
checknologin(void) {
    int fd, nchars;
    char tbuf[8192];
    
    if ((fd = open(_PATH_NOLOGIN, O_RDONLY, 0)) >= 0) {
	while ((nchars = read(fd, tbuf, sizeof(tbuf))) > 0)
	  write(fileno(stdout), tbuf, nchars);
	close(fd);
	sleepexit(0);
    }
}
#endif

void
dolastlog(int quiet) {
    struct lastlog ll;
    int fd;
    
    if ((fd = open(_PATH_LASTLOG, O_RDWR, 0)) >= 0) {
	lseek(fd, (off_t)pwd->pw_uid * sizeof(ll), SEEK_SET);
	if (!quiet) {
	    if (read(fd, (char *)&ll, sizeof(ll)) == sizeof(ll) &&
		ll.ll_time != 0) {
		    time_t ll_time = (time_t) ll.ll_time;

		    printf(_("Last login: %.*s "),
			   24-5, ctime(&ll_time));
		
		    if (*ll.ll_host != '\0')
			    printf(_("from %.*s\n"),
				   (int)sizeof(ll.ll_host), ll.ll_host);
		    else
			    printf(_("on %.*s\n"),
				   (int)sizeof(ll.ll_line), ll.ll_line);
	    }
	    lseek(fd, (off_t)pwd->pw_uid * sizeof(ll), SEEK_SET);
	}
	memset((char *)&ll, 0, sizeof(ll));
	time(&ll.ll_time);
	xstrncpy(ll.ll_line, tty_name, sizeof(ll.ll_line));
	if (hostname)
	    xstrncpy(ll.ll_host, hostname, sizeof(ll.ll_host));

	write(fd, (char *)&ll, sizeof(ll));
	close(fd);
    }
}

void
badlogin(const char *name) {
    if (failures == 1) {
	if (hostname)
	  syslog(LOG_NOTICE, _("LOGIN FAILURE FROM %s, %s"),
		 hostname, name);
	else
	  syslog(LOG_NOTICE, _("LOGIN FAILURE ON %s, %s"),
		 tty_name, name);
    } else {
	if (hostname)
	  syslog(LOG_NOTICE, _("%d LOGIN FAILURES FROM %s, %s"),
		 failures, hostname, name);
	else
	  syslog(LOG_NOTICE, _("%d LOGIN FAILURES ON %s, %s"),
		 failures, tty_name, name);
    }
}

/* Should not be called from PAM code... */
void
sleepexit(int eval) {
    sleep(SLEEP_EXIT_TIMEOUT);
    exit(eval);
}