/*
 * 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.
 */

/*
 * Copyright (c) 2018, Joyent, Inc.
 */

#include <errno.h>
#include <unistd.h>
#include <fcntl.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;
    int red;

    if (promptprog[0] == 0 || access(promptprog, X_OK) < 0)
        return -1;      /* sorry, can't help */

    /* This occurs when we're probed for the ability to supply a password */
    if (user != NULL && passwd == NULL)
        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);
        (void) close(p[0]);
        (void) close(p[1]);
        return 0;
    }
    if (kid == (pid_t)0) {
        /* we are the child, exec the program */
        char *argv[5], fdstr[32];

        sys_close();
        closelog();
        if (detached && p[1] <= 2) {
            (void) dup2(p[1], 3);
            p[1] = 3;
        }
        (void) close(p[0]);
        if (detached) {
            red = open("/etc/ppp/prompt-errors", O_WRONLY | O_APPEND | O_CREAT,
                0600);
            (void) dup2(red, 1);
            (void) dup2(red, 2);
        }
        (void) seteuid(getuid());
        (void) setegid(getgid());
        argv[0] = promptprog;
        argv[1] = user == NULL ? "" : user;
        argv[2] = remote_name;
        (void) slprintf(fdstr, sizeof (fdstr), "%d", p[1]);
        argv[3] = fdstr;
        argv[4] = NULL;
        (void) execv(*argv, argv);
        _exit(127);
    }

    /* we are the parent, read the password from the pipe */
    (void) close(p[1]);
    readgood = 0;
    do {
        red = read(p[0], passwd + readgood, MAXSECRETLEN-1 - readgood);
        if (red == 0)
            break;
        if (red < 0) {
            if (errno == EINTR)
                continue;
            error("Can't read secret from %s: %m", promptprog);
            readgood = -1;
            break;
        }
        readgood += red;
    } while (readgood < MAXSECRETLEN - 1);
    passwd[readgood] = 0;
    (void) 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 (readgood > 0 && passwd[--readgood] == '\n')
        passwd[readgood] = '\0';
    if (!WIFEXITED(wstat))
        warn("%s terminated abnormally", promptprog);
    if (WEXITSTATUS(wstat) != 0)
        warn("%s exited with code %d", promptprog, WEXITSTATUS(wstat));

    return 1;
}

void plugin_init(void)
{
    add_options(options);
    pap_passwd_hook = promptpass;
}