/*      $OpenBSD: auth.c,v 1.43 2024/08/21 14:57:05 florian Exp $       */

/*
 * auth.c - PPP authentication and phase control.
 *
 * Copyright (c) 1989-2002 Paul Mackerras. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name(s) of the authors of this software must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission.
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Paul Mackerras
 *     <paulus@samba.org>".
 *
 * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
 * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Copyright (c) 1984-2000 Carnegie Mellon University. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any legal
 *    details, please contact
 *      Office of Technology Transfer
 *      Carnegie Mellon University
 *      5000 Forbes Avenue
 *      Pittsburgh, PA  15213-3890
 *      (412) 268-4387, fax: (412) 268-7395
 *      tech-transfer@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <limits.h>
#include <syslog.h>
#include <pwd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <utmp.h>
#include <fcntl.h>
#if defined(_PATH_LASTLOG) && defined(_linux_)
#include <lastlog.h>
#endif

#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>



#include "pppd.h"
#include "fsm.h"
#include "lcp.h"
#include "ipcp.h"
#include "upap.h"
#include "chap.h"
#ifdef CBCP_SUPPORT
#include "cbcp.h"
#endif
#include "pathnames.h"

/* Used for storing a sequence of words.  Usually malloced. */
struct wordlist {
    struct wordlist     *next;
    char                word[1];
};

/* Bits in scan_authfile return value */
#define NONWILD_SERVER  1
#define NONWILD_CLIENT  2

#define ISWILD(word)    (word[0] == '*' && word[1] == 0)

#define FALSE   0
#define TRUE    1

/* The name by which the peer authenticated itself to us. */
char peer_authname[MAXNAMELEN];

/* Records which authentication operations haven't completed yet. */
static int auth_pending[NUM_PPP];

/* Set if we have successfully called plogin() */
static int logged_in;

/* Set if we have run the /etc/ppp/auth-up script. */
static int did_authup;

/* List of addresses which the peer may use. */
static struct wordlist *addresses[NUM_PPP];

/* Number of network protocols which we have opened. */
static int num_np_open;

/* Number of network protocols which have come up. */
static int num_np_up;

/* Set if we got the contents of passwd[] from the pap-secrets file. */
static int passwd_from_file;

/* Bits in auth_pending[] */
#define PAP_WITHPEER    1
#define PAP_PEER        2
#define CHAP_WITHPEER   4
#define CHAP_PEER       8

extern char *crypt(const char *, const char *);

/* Prototypes for procedures local to this file. */

static void network_phase(int);
static void check_idle(void *);
static void connect_time_expired(void *);
static int  plogin(char *, char *, char **, int *);
static void plogout(void);
static int  null_login(int);
static int  get_pap_passwd(char *);
static int  have_pap_secret(void);
static int  have_chap_secret(char *, char *, u_int32_t);
static int  ip_addr_check(u_int32_t, struct wordlist *);
static int  scan_authfile(FILE *, char *, char *, u_int32_t, char *,
                struct wordlist **, char *);
static void free_wordlist(struct wordlist *);
static void auth_script(char *);
static void set_allowed_addrs(int, struct wordlist *);

/*
 * An Open on LCP has requested a change from Dead to Establish phase.
 * Do what's necessary to bring the physical layer up.
 */
void
link_required(int unit)
{
}

/*
 * LCP has terminated the link; go to the Dead phase and take the
 * physical layer down.
 */
void
link_terminated(int unit)
{
    if (phase == PHASE_DEAD)
        return;
    if (logged_in)
        plogout();
    phase = PHASE_DEAD;
    syslog(LOG_NOTICE, "Connection terminated.");
}

/*
 * LCP has gone down; it will either die or try to re-establish.
 */
void
link_down(int unit)
{
    int i;
    struct protent *protp;

    if (did_authup) {
        auth_script(_PATH_AUTHDOWN);
        did_authup = 0;
    }
    for (i = 0; (protp = protocols[i]) != NULL; ++i) {
        if (!protp->enabled_flag)
            continue;
        if (protp->protocol != PPP_LCP && protp->lowerdown != NULL)
            (*protp->lowerdown)(unit);
        if (protp->protocol < 0xC000 && protp->close != NULL)
            (*protp->close)(unit, "LCP down");
    }
    num_np_open = 0;
    num_np_up = 0;
    if (phase != PHASE_DEAD)
        phase = PHASE_TERMINATE;
}

/*
 * The link is established.
 * Proceed to the Dead, Authenticate or Network phase as appropriate.
 */
void
link_established(int unit)
{
    int auth;
    lcp_options *wo = &lcp_wantoptions[unit];
    lcp_options *go = &lcp_gotoptions[unit];
    lcp_options *ho = &lcp_hisoptions[unit];
    int i;
    struct protent *protp;

    /*
     * Tell higher-level protocols that LCP is up.
     */
    for (i = 0; (protp = protocols[i]) != NULL; ++i)
        if (protp->protocol != PPP_LCP && protp->enabled_flag
            && protp->lowerup != NULL)
            (*protp->lowerup)(unit);

    if (auth_required && !(go->neg_chap || go->neg_upap)) {
        /*
         * We wanted the peer to authenticate itself, and it refused:
         * treat it as though it authenticated with PAP using a username
         * of "" and a password of "".  If that's not OK, boot it out.
         */
        if (!wo->neg_upap || !null_login(unit)) {
            syslog(LOG_WARNING, "peer refused to authenticate");
            lcp_close(unit, "peer refused to authenticate");
            return;
        }
    }

    phase = PHASE_AUTHENTICATE;
    auth = 0;
    if (go->neg_chap) {
        ChapAuthPeer(unit, our_name, go->chap_mdtype);
        auth |= CHAP_PEER;
    } else if (go->neg_upap) {
        upap_authpeer(unit);
        auth |= PAP_PEER;
    }
    if (ho->neg_chap) {
        ChapAuthWithPeer(unit, user, ho->chap_mdtype);
        auth |= CHAP_WITHPEER;
    } else if (ho->neg_upap) {
        if (passwd[0] == 0) {
            passwd_from_file = 1;
            if (!get_pap_passwd(passwd))
                syslog(LOG_ERR, "No secret found for PAP login");
        }
        upap_authwithpeer(unit, user, passwd);
        auth |= PAP_WITHPEER;
    }
    auth_pending[unit] = auth;

    if (!auth)
        network_phase(unit);
}

/*
 * Proceed to the network phase.
 */
static void
network_phase(int unit)
{
    int i;
    struct protent *protp;
    lcp_options *go = &lcp_gotoptions[unit];

    /*
     * If the peer had to authenticate, run the auth-up script now.
     */
    if ((go->neg_chap || go->neg_upap) && !did_authup) {
        auth_script(_PATH_AUTHUP);
        did_authup = 1;
    }

#ifdef CBCP_SUPPORT
    /*
     * If we negotiated callback, do it now.
     */
    if (go->neg_cbcp) {
        phase = PHASE_CALLBACK;
        (*cbcp_protent.open)(unit);
        return;
    }
#endif

    phase = PHASE_NETWORK;
#if 0
    if (!demand)
        set_filters(&pass_filter, &active_filter);
#endif
    for (i = 0; (protp = protocols[i]) != NULL; ++i)
        if (protp->protocol < 0xC000 && protp->enabled_flag
            && protp->open != NULL) {
            (*protp->open)(unit);
            if (protp->protocol != PPP_CCP)
                ++num_np_open;
        }

    if (num_np_open == 0)
        /* nothing to do */
        lcp_close(0, "No network protocols running");
}

/*
 * The peer has failed to authenticate himself using `protocol'.
 */
void
auth_peer_fail(int unit, int protocol)
{
    /*
     * Authentication failure: take the link down
     */
    lcp_close(unit, "Authentication failed");
}

/*
 * The peer has been successfully authenticated using `protocol'.
 */
void
auth_peer_success(int unit, int protocol, char *name, int namelen)
{
    int bit;

    switch (protocol) {
    case PPP_CHAP:
        bit = CHAP_PEER;
        break;
    case PPP_PAP:
        bit = PAP_PEER;
        break;
    default:
        syslog(LOG_WARNING, "auth_peer_success: unknown protocol %x",
               protocol);
        return;
    }

    /*
     * Save the authenticated name of the peer for later.
     */
    if (namelen > sizeof(peer_authname) - 1)
        namelen = sizeof(peer_authname) - 1;
    BCOPY(name, peer_authname, namelen);
    peer_authname[namelen] = 0;
    script_setenv("PEERNAME", peer_authname);

    /*
     * If there is no more authentication still to be done,
     * proceed to the network (or callback) phase.
     */
    if ((auth_pending[unit] &= ~bit) == 0)
        network_phase(unit);
}

/*
 * We have failed to authenticate ourselves to the peer using `protocol'.
 */
void
auth_withpeer_fail(int unit, int protocol)
{
    if (passwd_from_file)
        EXPLICIT_BZERO(passwd, MAXSECRETLEN);
    /*
     * We've failed to authenticate ourselves to our peer.
     * He'll probably take the link down, and there's not much
     * we can do except wait for that.
     */
}

/*
 * We have successfully authenticated ourselves with the peer using `protocol'.
 */
void
auth_withpeer_success(int unit, int protocol)
{
    int bit;

    switch (protocol) {
    case PPP_CHAP:
        bit = CHAP_WITHPEER;
        break;
    case PPP_PAP:
        if (passwd_from_file)
            EXPLICIT_BZERO(passwd, MAXSECRETLEN);
        bit = PAP_WITHPEER;
        break;
    default:
        syslog(LOG_WARNING, "auth_peer_success: unknown protocol %x",
               protocol);
        bit = 0;
    }

    /*
     * If there is no more authentication still being done,
     * proceed to the network (or callback) phase.
     */
    if ((auth_pending[unit] &= ~bit) == 0)
        network_phase(unit);
}


/*
 * np_up - a network protocol has come up.
 */
void
np_up(int unit, int proto)
{
    if (num_np_up == 0) {
        /*
         * At this point we consider that the link has come up successfully.
         */
        need_holdoff = 0;

        if (idle_time_limit > 0)
            TIMEOUT(check_idle, NULL, idle_time_limit);

        /*
         * Set a timeout to close the connection once the maximum
         * connect time has expired.
         */
        if (maxconnect > 0)
            TIMEOUT(connect_time_expired, 0, maxconnect);

        /*
         * Detach now, if the updetach option was given.
         */
        if (nodetach == -1)
            detach();
    }
    ++num_np_up;
}

/*
 * np_down - a network protocol has gone down.
 */
void
np_down(int unit, int proto)
{
    if (--num_np_up == 0 && idle_time_limit > 0) {
        UNTIMEOUT(check_idle, NULL);
    }
}

/*
 * np_finished - a network protocol has finished using the link.
 */
void
np_finished(int unit, int roto)
{
    if (--num_np_open <= 0) {
        /* no further use for the link: shut up shop. */
        lcp_close(0, "No network protocols running");
    }
}

/*
 * check_idle - check whether the link has been idle for long
 * enough that we can shut it down.
 */
static void
check_idle(void *arg)
{
    struct ppp_idle idle;
    time_t itime;

    if (!get_idle_time(0, &idle))
        return;
    itime = MIN(idle.xmit_idle, idle.recv_idle);
    if (itime >= idle_time_limit) {
        /* link is idle: shut it down. */
        syslog(LOG_INFO, "Terminating connection due to lack of activity.");
        lcp_close(0, "Link inactive");
    } else {
        TIMEOUT(check_idle, NULL, idle_time_limit - itime);
    }
}

/*
 * connect_time_expired - log a message and close the connection.
 */
static void
connect_time_expired(void *arg)
{
    syslog(LOG_INFO, "Connect time expired");
    lcp_close(0, "Connect time expired");       /* Close connection */
}

/*
 * auth_check_options - called to check authentication options.
 */
void
auth_check_options(void)
{
    lcp_options *wo = &lcp_wantoptions[0];
    int can_auth;
    ipcp_options *ipwo = &ipcp_wantoptions[0];
    u_int32_t remote;

    /* Default our_name to hostname, and user to our_name */
    if (our_name[0] == 0 || usehostname)
        strlcpy(our_name, hostname, HOST_NAME_MAX+1);
    if (user[0] == 0)
        strlcpy(user, our_name, MAXNAMELEN);

    /* If authentication is required, ask peer for CHAP or PAP. */
    if (auth_required && !wo->neg_chap && !wo->neg_upap) {
        wo->neg_chap = 1;
        wo->neg_upap = 1;
    }

    /*
     * Check whether we have appropriate secrets to use
     * to authenticate the peer.
     */
    can_auth = wo->neg_upap && (uselogin || have_pap_secret());
    if (!can_auth && wo->neg_chap) {
        remote = ipwo->accept_remote? 0: ipwo->hisaddr;
        can_auth = have_chap_secret(remote_name, our_name, remote);
    }

    if (auth_required && !can_auth) {
        option_error("peer authentication required but no suitable secret(s) found\n");
        if (remote_name[0] == 0)
            option_error("for authenticating any peer to us (%s)\n", our_name);
        else
            option_error("for authenticating peer %s to us (%s)\n",
                         remote_name, our_name);
        exit(1);
    }

    /*
     * Check whether the user tried to override certain values
     * set by root.
     */
    if (!auth_required && auth_req_info.priv > 0) {
        if (!default_device && devnam_info.priv == 0) {
            option_error("can't override device name when noauth option used");
            exit(1);
        }
        if ((connector != NULL && connector_info.priv == 0)
            || (disconnector != NULL && disconnector_info.priv == 0)
            || (welcomer != NULL && welcomer_info.priv == 0)) {
            option_error("can't override connect, disconnect or welcome");
            option_error("option values when noauth option used");
            exit(1);
        }
    }
}

/*
 * auth_reset - called when LCP is starting negotiations to recheck
 * authentication options, i.e. whether we have appropriate secrets
 * to use for authenticating ourselves and/or the peer.
 */
void
auth_reset(int unit)

{
    lcp_options *go = &lcp_gotoptions[unit];
    lcp_options *ao = &lcp_allowoptions[0];
    ipcp_options *ipwo = &ipcp_wantoptions[0];
    u_int32_t remote;

    ao->neg_upap = !refuse_pap && (passwd[0] != 0 || get_pap_passwd(NULL));
    ao->neg_chap = !refuse_chap
        && have_chap_secret(user, remote_name, (u_int32_t)0);

    if (go->neg_upap && !uselogin && !have_pap_secret())
        go->neg_upap = 0;
    if (go->neg_chap) {
        remote = ipwo->accept_remote? 0: ipwo->hisaddr;
        if (!have_chap_secret(remote_name, our_name, remote))
            go->neg_chap = 0;
    }
}


/*
 * check_passwd - Check the user name and passwd against the PAP secrets
 * file.  If requested, also check against the system password database,
 * and login the user if OK.
 *
 * returns:
 *      UPAP_AUTHNAK: Authentication failed.
 *      UPAP_AUTHACK: Authentication succeeded.
 * In either case, msg points to an appropriate message.
 */
int
check_passwd(int unit, char *auser, int userlen,
    char *apasswd, int passwdlen, char **msg, int *msglen)
{
    int ret;
    char *filename;
    FILE *f;
    struct wordlist *addrs;
    u_int32_t remote;
    ipcp_options *ipwo = &ipcp_wantoptions[unit];
    char passwd[256], user[256];
    char secret[MAXWORDLEN];
    static int attempts = 0;

    /*
     * Make copies of apasswd and auser, then null-terminate them.
     */
    BCOPY(apasswd, passwd, passwdlen);
    passwd[passwdlen] = '\0';
    BCOPY(auser, user, userlen);
    user[userlen] = '\0';
    *msg = (char *) 0;

    /*
     * Open the file of pap secrets and scan for a suitable secret
     * for authenticating this user.
     */
    filename = _PATH_UPAPFILE;
    addrs = NULL;
    ret = UPAP_AUTHACK;
    f = fopen(filename, "r");
    if (f == NULL) {
        syslog(LOG_ERR, "Can't open PAP password file %s: %m", filename);
        ret = UPAP_AUTHNAK;
    } else {
        check_access(f, filename);
        remote = ipwo->accept_remote? 0: ipwo->hisaddr;
        if (scan_authfile(f, user, our_name, remote,
                          secret, &addrs, filename) < 0
            || (secret[0] != 0 && (cryptpap || strcmp(passwd, secret) != 0)
                && strcmp(crypt(passwd, secret), secret) != 0)) {
            syslog(LOG_WARNING, "PAP authentication failure for %s", user);
            ret = UPAP_AUTHNAK;
        }
        fclose(f);
    }

    if (uselogin && ret == UPAP_AUTHACK) {
        ret = plogin(user, passwd, msg, msglen);
        if (ret == UPAP_AUTHNAK) {
            syslog(LOG_WARNING, "PAP login failure for %s", user);
        }
    }

    if (ret == UPAP_AUTHNAK) {
        if (*msg == (char *) 0)
            *msg = "Login incorrect";
        *msglen = strlen(*msg);
        /*
         * Frustrate passwd stealer programs.
         * Allow 10 tries, but start backing off after 3 (stolen from login).
         * On 10'th, drop the connection.
         */
        if (attempts++ >= 10) {
            syslog(LOG_WARNING, "%d LOGIN FAILURES ON %s, %s",
                   attempts, devnam, user);
            quit();
        }
        if (attempts > 3)
            sleep((u_int) (attempts - 3) * 5);
        if (addrs != NULL)
            free_wordlist(addrs);

    } else {
        attempts = 0;                   /* Reset count */
        if (*msg == (char *) 0)
            *msg = "Login ok";
        *msglen = strlen(*msg);
        set_allowed_addrs(unit, addrs);
    }

    EXPLICIT_BZERO(passwd, sizeof(passwd));
    EXPLICIT_BZERO(secret, sizeof(secret));

    return ret;
}

/*
 * plogin - Check the user name and password against the system
 * password database, and login the user if OK.
 *
 * returns:
 *      UPAP_AUTHNAK: Login failed.
 *      UPAP_AUTHACK: Login succeeded.
 * In either case, msg points to an appropriate message.
 */

static int
plogin(char *user, char *passwd, char **msg, int *msglen)
{
    struct passwd *pw;
    char *tty;

    pw = getpwnam_shadow(user);
    if (crypt_checkpass(passwd, pw ? pw->pw_passwd : NULL))
            return UPAP_AUTHNAK;

    /*
     * Write a wtmp entry for this user.
     */

    tty = devnam;
    if (strncmp(tty, "/dev/", 5) == 0)
        tty += 5;
    logwtmp(tty, user, remote_name);            /* Add wtmp login entry */

#if defined(_PATH_LASTLOG)
    {
            struct lastlog ll;
            int fd;

            if ((fd = open(_PATH_LASTLOG, O_RDWR)) >= 0) {
                memset(&ll, 0, sizeof(ll));
                (void)time(&ll.ll_time);
                (void)strncpy(ll.ll_line, tty, sizeof(ll.ll_line));
                (void)pwrite(fd, &ll, sizeof(ll), (off_t)pw->pw_uid *
                    sizeof(ll));
                (void)close(fd);
            }
    }
#endif


    syslog(LOG_INFO, "user %s logged in", user);
    logged_in = TRUE;

    return (UPAP_AUTHACK);
}

/*
 * plogout - Logout the user.
 */
static void
plogout(void)
{
    char *tty;

    tty = devnam;
    if (strncmp(tty, "/dev/", 5) == 0)
        tty += 5;
    logwtmp(tty, "", "");               /* Wipe out utmp logout entry */

    logged_in = FALSE;
}


/*
 * null_login - Check if a username of "" and a password of "" are
 * acceptable, and iff so, set the list of acceptable IP addresses
 * and return 1.
 */
static int
null_login(int unit)
{
    char *filename;
    FILE *f;
    int i, ret;
    struct wordlist *addrs;
    char secret[MAXWORDLEN];

    /*
     * Open the file of pap secrets and scan for a suitable secret.
     * We don't accept a wildcard client.
     */
    filename = _PATH_UPAPFILE;
    addrs = NULL;
    f = fopen(filename, "r");
    if (f == NULL)
        return 0;
    check_access(f, filename);

    i = scan_authfile(f, "", our_name, (u_int32_t)0, secret, &addrs, filename);
    ret = i >= 0 && (i & NONWILD_CLIENT) != 0 && secret[0] == 0;
    EXPLICIT_BZERO(secret, sizeof(secret));

    if (ret)
        set_allowed_addrs(unit, addrs);
    else
        free_wordlist(addrs);

    fclose(f);
    return ret;
}


/*
 * get_pap_passwd - get a password for authenticating ourselves with
 * our peer using PAP.  Returns 1 on success, 0 if no suitable password
 * could be found.
 */
static int
get_pap_passwd(char *passwd)
{
    char *filename;
    FILE *f;
    int ret;
    char secret[MAXWORDLEN];

    filename = _PATH_UPAPFILE;
    f = fopen(filename, "r");
    if (f == NULL)
        return 0;
    check_access(f, filename);
    ret = scan_authfile(f, user,
                        remote_name[0]? remote_name: NULL,
                        (u_int32_t)0, secret, NULL, filename);
    fclose(f);
    if (ret < 0)
        return 0;
    if (passwd != NULL)
        strlcpy(passwd, secret, MAXSECRETLEN);
    EXPLICIT_BZERO(secret, sizeof(secret));
    return 1;
}


/*
 * have_pap_secret - check whether we have a PAP file with any
 * secrets that we could possibly use for authenticating the peer.
 */
static int
have_pap_secret(void)
{
    FILE *f;
    int ret;
    char *filename;
    ipcp_options *ipwo = &ipcp_wantoptions[0];
    u_int32_t remote;

    filename = _PATH_UPAPFILE;
    f = fopen(filename, "r");
    if (f == NULL)
        return 0;

    remote = ipwo->accept_remote? 0: ipwo->hisaddr;
    ret = scan_authfile(f, NULL, our_name, remote, NULL, NULL, filename);
    fclose(f);
    if (ret < 0)
        return 0;

    return 1;
}


/*
 * have_chap_secret - check whether we have a CHAP file with a
 * secret that we could possibly use for authenticating `client'
 * on `server'.  Either can be the null string, meaning we don't
 * know the identity yet.
 */
static int
have_chap_secret(char *client, char *server, u_int32_t remote)
{
    FILE *f;
    int ret;
    char *filename;

    filename = _PATH_CHAPFILE;
    f = fopen(filename, "r");
    if (f == NULL)
        return 0;

    if (client[0] == 0)
        client = NULL;
    else if (server[0] == 0)
        server = NULL;

    ret = scan_authfile(f, client, server, remote, NULL, NULL, filename);
    fclose(f);
    if (ret < 0)
        return 0;

    return 1;
}


/*
 * get_secret - open the CHAP secret file and return the secret
 * for authenticating the given client on the given server.
 * (We could be either client or server).
 */
int
get_secret(int unit, char *client, char *server,
    char *secret, int *secret_len, int save_addrs)
{
    FILE *f;
    int ret, len;
    char *filename;
    struct wordlist *addrs;
    char secbuf[MAXWORDLEN];

    filename = _PATH_CHAPFILE;
    addrs = NULL;
    secbuf[0] = 0;

    f = fopen(filename, "r");
    if (f == NULL) {
        syslog(LOG_ERR, "Can't open chap secret file %s: %m", filename);
        return 0;
    }
    check_access(f, filename);

    ret = scan_authfile(f, client, server, (u_int32_t)0,
                        secbuf, &addrs, filename);
    fclose(f);
    if (ret < 0)
        return 0;

    if (save_addrs)
        set_allowed_addrs(unit, addrs);

    len = strlen(secbuf);
    if (len > MAXSECRETLEN) {
        syslog(LOG_ERR, "Secret for %s on %s is too long", client, server);
        len = MAXSECRETLEN;
    }
    BCOPY(secbuf, secret, len);
    EXPLICIT_BZERO(secbuf, sizeof(secbuf));
    *secret_len = len;

    return 1;
}

/*
 * set_allowed_addrs() - set the list of allowed addresses.
 */
static void
set_allowed_addrs(int unit, struct wordlist *addrs)
{
    if (addresses[unit] != NULL)
        free_wordlist(addresses[unit]);
    addresses[unit] = addrs;

    /*
     * If there's only one authorized address we might as well
     * ask our peer for that one right away
     */
    if (addrs != NULL && addrs->next == NULL) {
        char *p = addrs->word;
        struct ipcp_options *wo = &ipcp_wantoptions[unit];
        struct in_addr ina;
        struct hostent *hp;

        if (*p != '!' && *p != '-' && !ISWILD(p) && strchr(p, '/') == NULL) {
            hp = gethostbyname(p);
            if (hp != NULL && hp->h_addrtype == AF_INET)
                wo->hisaddr = *(u_int32_t *)hp->h_addr;
            else if (inet_pton(AF_INET, p, &ina) == 1)
                wo->hisaddr = ina.s_addr;
        }
    }
}

/*
 * auth_ip_addr - check whether the peer is authorized to use
 * a given IP address.  Returns 1 if authorized, 0 otherwise.
 */
int
auth_ip_addr(int unit, u_int32_t addr)
{
    return ip_addr_check(addr, addresses[unit]);
}

static int
ip_addr_check(u_int32_t addr, struct wordlist *addrs)
{
    u_int32_t mask, ah;
    struct in_addr ina;
    int accept, r = 1;
    char *ptr_word, *ptr_mask;
    struct hostent *hp;

    /* don't allow loopback or multicast address */
    if (bad_ip_adrs(addr))
        return 0;

    if (addrs == NULL)
        return !auth_required;          /* no addresses authorized */

    for (; addrs != NULL; addrs = addrs->next) {
        /* "-" means no addresses authorized, "*" means any address allowed */
        ptr_word = addrs->word;
        if (strcmp(ptr_word, "-") == 0)
            break;
        if (strcmp(ptr_word, "*") == 0)
            return 1;

        accept = 1;
        if (*ptr_word == '!') {
            accept = 0;
            ++ptr_word;
        }

        mask = ~ (u_int32_t) 0;
        ptr_mask = strchr (ptr_word, '/');
        if (ptr_mask != NULL) {
            int bit_count;

            bit_count = (int) strtol (ptr_mask+1, (char **) 0, 10);
            if (bit_count <= 0 || bit_count > 32) {
                syslog (LOG_WARNING,
                        "invalid address length %s in auth. address list",
                        ptr_mask);
                continue;
            }
            *ptr_mask = '\0';
            mask <<= 32 - bit_count;
        }

        hp = gethostbyname(ptr_word);
        if (hp != NULL && hp->h_addrtype == AF_INET) {
            ina.s_addr = *(u_int32_t *)hp->h_addr;
        } else {
            r = inet_pton(AF_INET, ptr_word, &ina);
            if (ptr_mask == NULL) {
                /* calculate appropriate mask for net */
                ah = ntohl(ina.s_addr);
                if (IN_CLASSA(ah))
                    mask = IN_CLASSA_NET;
                else if (IN_CLASSB(ah))
                    mask = IN_CLASSB_NET;
                else if (IN_CLASSC(ah))
                    mask = IN_CLASSC_NET;
            }
        }

        if (ptr_mask != NULL)
            *ptr_mask = '/';

        if (r != 1)
            syslog (LOG_WARNING,
                    "unknown host %s in auth. address list",
                    addrs->word);
        else
            /* Here ina.s_addr and addr are in network byte order,
               and mask is in host order. */
            if (((addr ^ ina.s_addr) & htonl(mask)) == 0)
                return accept;
    }
    return 0;                   /* not in list => can't have it */
}

/*
 * bad_ip_adrs - return 1 if the IP address is one we don't want
 * to use, such as an address in the loopback net or a multicast address.
 * addr is in network byte order.
 */
int
bad_ip_adrs(u_int32_t addr)
{
    addr = ntohl(addr);
    return (addr >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET
        || IN_MULTICAST(addr);
}

/*
 * check_access - complain if a secret file has too-liberal permissions.
 */
void
check_access(FILE *f, char *filename)
{
    struct stat sbuf;

    if (fstat(fileno(f), &sbuf) < 0) {
        syslog(LOG_WARNING, "cannot stat secret file %s: %m", filename);
    } else if ((sbuf.st_mode & (S_IRWXG | S_IRWXO)) != 0) {
        syslog(LOG_WARNING, "Warning - secret file %s has world and/or group access", filename);
    }
}


/*
 * scan_authfile - Scan an authorization file for a secret suitable
 * for authenticating `client' on `server'.  The return value is -1
 * if no secret is found, otherwise >= 0.  The return value has
 * NONWILD_CLIENT set if the secret didn't have "*" for the client, and
 * NONWILD_SERVER set if the secret didn't have "*" for the server.
 * Any following words on the line (i.e. address authorization
 * info) are placed in a wordlist and returned in *addrs.
 */
static int
scan_authfile(FILE *f, char *client, char *server, u_int32_t ipaddr,
    char *secret, struct wordlist **addrs, char *filename)
{
    int newline, xxx;
    int got_flag, best_flag;
    FILE *sf;
    struct wordlist *ap, *addr_list, *alist, *alast;
    char word[MAXWORDLEN];
    char atfile[MAXWORDLEN];
    char lsecret[MAXWORDLEN];

    if (addrs != NULL)
        *addrs = NULL;
    addr_list = NULL;
    if (!getword(f, word, &newline, filename))
        return -1;              /* file is empty??? */
    newline = 1;
    best_flag = -1;
    for (;;) {
        /*
         * Skip until we find a word at the start of a line.
         */
        while (!newline && getword(f, word, &newline, filename))
            ;
        if (!newline)
            break;              /* got to end of file */

        /*
         * Got a client - check if it's a match or a wildcard.
         */
        got_flag = 0;
        if (client != NULL && strcmp(word, client) != 0 && !ISWILD(word)) {
            newline = 0;
            continue;
        }
        if (!ISWILD(word))
            got_flag = NONWILD_CLIENT;

        /*
         * Now get a server and check if it matches.
         */
        if (!getword(f, word, &newline, filename))
            break;
        if (newline)
            continue;
        if (server != NULL && strcmp(word, server) != 0 && !ISWILD(word))
            continue;
        if (!ISWILD(word))
            got_flag |= NONWILD_SERVER;

        /*
         * Got some sort of a match - see if it's better than what
         * we have already.
         */
        if (got_flag <= best_flag)
            continue;

        /*
         * Get the secret.
         */
        if (!getword(f, word, &newline, filename))
            break;
        if (newline)
            continue;

        /*
         * Special syntax: @filename means read secret from file.
         */
        if (word[0] == '@') {
            strlcpy(atfile, word+1, sizeof atfile);
            if ((sf = fopen(atfile, "r")) == NULL) {
                syslog(LOG_WARNING, "can't open indirect secret file %s",
                       atfile);
                continue;
            }
            check_access(sf, atfile);
            if (!getword(sf, word, &xxx, atfile)) {
                syslog(LOG_WARNING, "no secret in indirect secret file %s",
                       atfile);
                fclose(sf);
                continue;
            }
            fclose(sf);
        }
        if (secret != NULL)
            strlcpy(lsecret, word, sizeof lsecret);

        /*
         * Now read address authorization info and make a wordlist.
         */
        alist = alast = NULL;
        for (;;) {
            size_t wordlen;

            if (!getword(f, word, &newline, filename) || newline)
                break;
            wordlen = strlen(word);     /* NUL in struct wordlist */
            ap = (struct wordlist *) malloc(sizeof(struct wordlist) +
                wordlen);

            if (ap == NULL)
                novm("authorized addresses");
            ap->next = NULL;
            strlcpy(ap->word, word, wordlen + 1);
            if (alist == NULL)
                alist = ap;
            else
                alast->next = ap;
            alast = ap;
        }

        /*
         * Check if the given IP address is allowed by the wordlist.
         */
        if (ipaddr != 0 && !ip_addr_check(ipaddr, alist)) {
            free_wordlist(alist);
            continue;
        }

        /*
         * This is the best so far; remember it.
         */
        best_flag = got_flag;
        if (addr_list)
            free_wordlist(addr_list);
        addr_list = alist;
        if (secret != NULL)
            strlcpy(secret, lsecret, MAXWORDLEN);

        if (!newline)
            break;
    }

    if (addrs != NULL)
        *addrs = addr_list;
    else if (addr_list != NULL)
        free_wordlist(addr_list);

    return best_flag;
}

/*
 * free_wordlist - release memory allocated for a wordlist.
 */
static void
free_wordlist(struct wordlist *wp)
{
    struct wordlist *next;

    while (wp != NULL) {
        next = wp->next;
        free(wp);
        wp = next;
    }
}

/*
 * auth_script - execute a script with arguments
 * interface-name peer-name real-user tty speed
 */
static void
auth_script(char *script)
{
    char strspeed[32];
    struct passwd *pw;
    char struid[32];
    char *user_name;
    char *argv[8];

    if ((pw = getpwuid(getuid())) != NULL && pw->pw_name != NULL)
        user_name = pw->pw_name;
    else {
        snprintf(struid, sizeof struid, "%u", getuid());
        user_name = struid;
    }
    snprintf(strspeed, sizeof strspeed, "%d", baud_rate);

    argv[0] = script;
    argv[1] = ifname;
    argv[2] = peer_authname;
    argv[3] = user_name;
    argv[4] = devnam;
    argv[5] = strspeed;
    argv[6] = NULL;

    run_program(script, argv, 0);
}