/* * passprompt.c - pppd plugin to invoke an external PAP password prompter * * Copyright 1999 Paul Mackerras, Alan Curry. * *  This program is free software; you can redistribute it and/or *  modify it under the terms of the GNU General Public License *  as published by the Free Software Foundation; either version *  2 of the License, or (at your option) any later version. */#include <errno.h>#include <unistd.h>#include <sys/wait.h>#include <syslog.h>#include "pppd.h"static char promptprog[PATH_MAX+1];static option_t options[] = {    { "promptprog", o_string, promptprog,      "External PAP password prompting program",      OPT_STATIC, NULL, PATH_MAX },    { NULL }};static int promptpass(char *user, char *passwd){    int p[2];    pid_t kid;    int readgood, wstat;    size_t red;    if (promptprog[0] == 0 || access(promptprog, X_OK) < 0)	return -1;	/* sorry, can't help */    if (!passwd)	return 1;    if (pipe(p)) {	warn("Can't make a pipe for %s", promptprog);	return 0;    }    if ((kid = fork()) == (pid_t) -1) {	warn("Can't fork to run %s", promptprog);	close(p[0]);	close(p[1]);	return 0;    }    if (!kid) {	/* we are the child, exec the program */	char *argv[4], fdstr[32];	sys_close();	closelog();	close(p[0]);	seteuid(getuid());	setegid(getgid());	argv[0] = promptprog;	argv[1] = user;	argv[2] = remote_name;	sprintf(fdstr, "%d", p[1]);	argv[3] = fdstr;	argv[4] = 0;	execv(*argv, argv);	_exit(127);    }    /* we are the parent, read the password from the pipe */    close(p[1]);    readgood = 0;    do {	red = read(p[0], passwd + readgood, MAXSECRETLEN-1 - readgood);	if (red == 0)	    break;	if (red < 0) {	    error("Can't read secret from %s: %m", promptprog);	    readgood = -1;	    break;	}	readgood += red;    } while (readgood < MAXSECRETLEN - 1);    passwd[readgood] = 0;    close(p[0]);    /* now wait for child to exit */    while (waitpid(kid, &wstat, 0) < 0) {	if (errno != EINTR) {	    warn("error waiting for %s: %m", promptprog);	    break;	}    }    if (readgood < 0)	return 0;    if (!WIFEXITED(wstat))	warn("%s terminated abnormally", promptprog);    if (WEXITSTATUS(wstat))	warn("%s exited with code %d", promptprog, WEXITSTATUS(status));    return 1;}void plugin_init(void){    add_options(options);    pap_passwd_hook = promptpass;}