[ppp.git] / pppd / auth.c

/*
 * auth.c - PPP authentication and phase control.
 *
 * Copyright (c) 1993 The Australian National University.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the Australian National University.  The name of the University
 * may not be used to endorse or promote products derived from this
 * software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Copyright (c) 1989 Carnegie Mellon University.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by Carnegie Mellon University.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifndef lint
static char rcsid[] = "$Id: auth.c,v 1.52 1999/05/12 06:19:46 paulus Exp $";
#endif

#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <pwd.h>
#include <grp.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>

#ifdef USE_PAM
#include <security/pam_appl.h>
#endif

#ifdef HAS_SHADOW
#include <shadow.h>
#ifndef PW_PPP
#define PW_PPP PW_LOGIN
#endif
#endif

#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;
};

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

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

/* 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;

/* List of addresses which the peer may use. */
static struct permitted_ip *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;

/*
 * This is used to ensure that we don't start an auth-up/down
 * script while one is already running.
 */
enum script_state {
    s_down,
    s_up
};

static enum script_state auth_state = s_down;
static enum script_state auth_script_state = s_down;
static pid_t auth_script_pid = 0;

/*
 * Option variables.
 */
bool uselogin = 0;              /* Use /etc/passwd for checking PAP */
bool cryptpap = 0;              /* Passwords in pap-secrets are encrypted */
bool refuse_pap = 0;            /* Don't wanna auth. ourselves with PAP */
bool refuse_chap = 0;           /* Don't wanna auth. ourselves with CHAP */
bool usehostname = 0;           /* Use hostname for our_name */
bool auth_required = 0;         /* Always require authentication from peer */
bool allow_any_ip = 0;          /* Allow peer to use any IP address */
bool explicit_remote = 0;       /* User specified explicit remote name */
char remote_name[MAXNAMELEN];   /* Peer's name for authentication */

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

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

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

static void network_phase __P((int));
static void check_idle __P((void *));
static void connect_time_expired __P((void *));
static int  plogin __P((char *, char *, char **, int *));
static void plogout __P((void));
static int  null_login __P((int));
static int  get_pap_passwd __P((char *));
static int  have_pap_secret __P((int *));
static int  have_chap_secret __P((char *, char *, int, int *));
static int  ip_addr_check __P((u_int32_t, struct permitted_ip *));
static int  scan_authfile __P((FILE *, char *, char *, char *,
                               struct wordlist **, char *));
static void free_wordlist __P((struct wordlist *));
static void auth_script __P((char *));
static void auth_script_done __P((void *));
static void set_allowed_addrs __P((int, struct wordlist *));
static int  some_ip_ok __P((struct wordlist *));
static int  setupapfile __P((char **));
static int  privgroup __P((char **));
static void check_access __P((FILE *, char *));

/*
 * Authentication-related options.
 */
option_t auth_options[] = {
    { "require-pap", o_bool, &lcp_wantoptions[0].neg_upap,
      "Require PAP authentication from peer", 1, &auth_required },
    { "+pap", o_bool, &lcp_wantoptions[0].neg_upap,
      "Require PAP authentication from peer", 1, &auth_required },
    { "refuse-pap", o_bool, &refuse_pap,
      "Don't agree to auth to peer with PAP", 1 },
    { "-pap", o_bool, &refuse_pap,
      "Don't allow PAP authentication with peer", 1 },
    { "require-chap", o_bool, &lcp_wantoptions[0].neg_chap,
      "Require CHAP authentication from peer", 1, &auth_required },
    { "+chap", o_bool, &lcp_wantoptions[0].neg_chap,
      "Require CHAP authentication from peer", 1, &auth_required },
    { "refuse-chap", o_bool, &refuse_chap,
      "Don't agree to auth to peer with CHAP", 1 },
    { "-chap", o_bool, &refuse_chap,
      "Don't allow CHAP authentication with peer", 1 },
    { "name", o_string, our_name,
      "Set local name for authentication",
      OPT_PRIV|OPT_STATIC, NULL, MAXNAMELEN },
    { "user", o_string, user,
      "Set name for auth with peer", OPT_STATIC, NULL, MAXNAMELEN },
    { "usehostname", o_bool, &usehostname,
      "Must use hostname for authentication", 1 },
    { "remotename", o_string, remote_name,
      "Set remote name for authentication", OPT_STATIC,
      &explicit_remote, MAXNAMELEN },
    { "auth", o_bool, &auth_required,
      "Require authentication from peer", 1 },
    { "noauth", o_bool, &auth_required,
      "Don't require peer to authenticate", OPT_PRIV, &allow_any_ip },
    {  "login", o_bool, &uselogin,
      "Use system password database for PAP", 1 },
    { "papcrypt", o_bool, &cryptpap,
      "PAP passwords are encrypted", 1 },
    { "+ua", o_special, setupapfile,
      "Get PAP user and password from file" },
    { "privgroup", o_special, privgroup,
      "Allow group members to use privileged options", OPT_PRIV },
    { NULL }
};

/*
 * setupapfile - specifies UPAP info for authenticating with peer.
 */
static int
setupapfile(argv)
    char **argv;
{
    FILE * ufile;
    int l;

    lcp_allowoptions[0].neg_upap = 1;

    /* open user info file */
    seteuid(getuid());
    ufile = fopen(*argv, "r");
    seteuid(0);
    if (ufile == NULL) {
        option_error("unable to open user login data file %s", *argv);
        return 0;
    }
    check_access(ufile, *argv);

    /* get username */
    if (fgets(user, MAXNAMELEN - 1, ufile) == NULL
        || fgets(passwd, MAXSECRETLEN - 1, ufile) == NULL){
        option_error("unable to read user login data file %s", *argv);
        return 0;
    }
    fclose(ufile);

    /* get rid of newlines */
    l = strlen(user);
    if (l > 0 && user[l-1] == '\n')
        user[l-1] = 0;
    l = strlen(passwd);
    if (l > 0 && passwd[l-1] == '\n')
        passwd[l-1] = 0;

    return (1);
}


/*
 * privgroup - allow members of the group to have privileged access.
 */
static int
privgroup(argv)
    char **argv;
{
    struct group *g;
    int i;

    g = getgrnam(*argv);
    if (g == 0) {
        option_error("group %s is unknown", *argv);
        return 0;
    }
    for (i = 0; i < ngroups; ++i) {
        if (groups[i] == g->gr_gid) {
            privileged = 1;
            break;
        }
    }
    return 1;
}


/*
 * 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(unit)
    int unit;
{
}

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

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

    auth_state = s_down;
    if (auth_script_state == s_up && auth_script_pid == 0) {
        auth_script_state = s_down;
        auth_script(_PATH_AUTHDOWN);
    }
    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(unit)
    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)) {
            warn("peer refused to authenticate: terminating link");
            lcp_close(unit, "peer refused to authenticate");
            status = EXIT_PEER_AUTH_FAILED;
            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))
                error("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(unit)
    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) {
        auth_state = s_up;
        if (auth_script_state == s_down && auth_script_pid == 0) {
            auth_script_state = s_up;
            auth_script(_PATH_AUTHUP);
        }
    }

#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(unit, protocol)
    int unit, protocol;
{
    /*
     * Authentication failure: take the link down
     */
    lcp_close(unit, "Authentication failed");
    status = EXIT_PEER_AUTH_FAILED;
}

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

    switch (protocol) {
    case PPP_CHAP:
        bit = CHAP_PEER;
        break;
    case PPP_PAP:
        bit = PAP_PEER;
        break;
    default:
        warn("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(unit, protocol)
    int unit, protocol;
{
    if (passwd_from_file)
        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(unit, protocol)
    int unit, protocol;
{
    int bit;

    switch (protocol) {
    case PPP_CHAP:
        bit = CHAP_WITHPEER;
        break;
    case PPP_PAP:
        if (passwd_from_file)
            BZERO(passwd, MAXSECRETLEN);
        bit = PAP_WITHPEER;
        break;
    default:
        warn("auth_withpeer_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(unit, proto)
    int unit, proto;
{
    if (num_np_up == 0) {
        /*
         * At this point we consider that the link has come up successfully.
         */
        need_holdoff = 0;
        status = EXIT_OK;

        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 (updetach && !nodetach)
            detach();
    }
    ++num_np_up;
}

/*
 * np_down - a network protocol has gone down.
 */
void
np_down(unit, proto)
    int unit, 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(unit, proto)
    int unit, proto;
{
    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(arg)
     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. */
        notice("Terminating connection due to lack of activity.");
        lcp_close(0, "Link inactive");
        status = EXIT_IDLE_TIMEOUT;
    } else {
        TIMEOUT(check_idle, NULL, idle_time_limit - itime);
    }
}

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

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

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

    /*
     * If we have a default route, require the peer to authenticate
     * unless the noauth option was given.
     */
    if (!auth_required && !allow_any_ip && have_route_to(0))
        auth_required = 1;

    /* If authentication is required, ask peer for CHAP or PAP. */
    if (auth_required) {
        if (!wo->neg_chap && !wo->neg_upap) {
            wo->neg_chap = 1;
            wo->neg_upap = 1;
        }
    } else {
        wo->neg_chap = 0;
        wo->neg_upap = 0;
    }

    /*
     * Check whether we have appropriate secrets to use
     * to authenticate the peer.
     */
    lacks_ip = 0;
    can_auth = wo->neg_upap && (uselogin || have_pap_secret(&lacks_ip));
    if (!can_auth && wo->neg_chap) {
        can_auth = have_chap_secret((explicit_remote? remote_name: NULL),
                                    our_name, 1, &lacks_ip);
    }

    if (auth_required && !can_auth) {
        if (explicit_remote)
            option_error(
"The remote system (%s) is required to authenticate itself but I",
                         remote_name);
        else
            option_error(
"The remote system is required to authenticate itself but I");

        if (!lacks_ip)
            option_error(
"couldn't find any suitable secret (password) for it to use to do so.");
        else
            option_error(
"couldn't find any secret (password) which would let it use an IP address.");

        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(unit)
    int unit;
{
    lcp_options *go = &lcp_gotoptions[unit];
    lcp_options *ao = &lcp_allowoptions[0];

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

    if (go->neg_upap && !uselogin && !have_pap_secret(NULL))
        go->neg_upap = 0;
    if (go->neg_chap) {
        if (!have_chap_secret((explicit_remote? remote_name: NULL),
                              our_name, 1, NULL))
            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(unit, auser, userlen, apasswd, passwdlen, msg, msglen)
    int unit;
    char *auser;
    int userlen;
    char *apasswd;
    int passwdlen;
    char **msg;
    int *msglen;
{
    int ret;
    char *filename;
    FILE *f;
    struct wordlist *addrs;
    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) {
        error("Can't open PAP password file %s: %m", filename);
        ret = UPAP_AUTHNAK;

    } else {
        check_access(f, filename);
        if (scan_authfile(f, user, our_name, secret, &addrs, filename) < 0
            || (secret[0] != 0 && (cryptpap || strcmp(passwd, secret) != 0)
                && strcmp(crypt(passwd, secret), secret) != 0)) {
            warn("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) {
            warn("PAP login failure for %s", user);
        }
    }

    if (ret == UPAP_AUTHNAK) {
        if (*msg == (char *) 0)
            *msg = "Login incorrect";
        *msglen = strlen(*msg);
        /*
         * XXX can we ever get here more than once??
         * 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) {
            warn("%d LOGIN FAILURES ON %s, %s", attempts, devnam, user);
            lcp_close(unit, "login failed");
        }
        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);
    }

    BZERO(passwd, sizeof(passwd));
    BZERO(secret, sizeof(secret));

    return ret;
}

/*
 * This function is needed for PAM.
 */

#ifdef USE_PAM
/* Static variables used to communicate between the conversation function
 * and the server_login function 
 */
static char *PAM_username;
static char *PAM_password;
static int PAM_error = 0;
static pam_handle_t *pamh = NULL;

/* PAM conversation function
 * Here we assume (for now, at least) that echo on means login name, and
 * echo off means password.
 */

static int PAM_conv (int num_msg, const struct pam_message **msg,
                    struct pam_response **resp, void *appdata_ptr)
{
    int replies = 0;
    struct pam_response *reply = NULL;

#define COPY_STRING(s) (s) ? strdup(s) : NULL

    reply = malloc(sizeof(struct pam_response) * num_msg);
    if (!reply) return PAM_CONV_ERR;

    for (replies = 0; replies < num_msg; replies++) {
        switch (msg[replies]->msg_style) {
            case PAM_PROMPT_ECHO_ON:
                reply[replies].resp_retcode = PAM_SUCCESS;
                reply[replies].resp = COPY_STRING(PAM_username);
                /* PAM frees resp */
                break;
            case PAM_PROMPT_ECHO_OFF:
                reply[replies].resp_retcode = PAM_SUCCESS;
                reply[replies].resp = COPY_STRING(PAM_password);
                /* PAM frees resp */
                break;
            case PAM_TEXT_INFO:
                /* fall through */
            case PAM_ERROR_MSG:
                /* ignore it, but pam still wants a NULL response... */
                reply[replies].resp_retcode = PAM_SUCCESS;
                reply[replies].resp = NULL;
                break;
            default:       
                /* Must be an error of some sort... */
                free (reply);
                PAM_error = 1;
                return PAM_CONV_ERR;
        }
    }
    *resp = reply;     
    return PAM_SUCCESS;
}

static struct pam_conv PAM_conversation = {
    &PAM_conv,
    NULL
};
#endif  /* USE_PAM */

/*
 * 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(user, passwd, msg, msglen)
    char *user;
    char *passwd;
    char **msg;
    int *msglen;
{
    char *tty;

#ifdef USE_PAM
    int pam_error;

    pam_error = pam_start ("ppp", user, &PAM_conversation, &pamh);
    if (pam_error != PAM_SUCCESS) {
        *msg = (char *) pam_strerror (pamh, pam_error);
        reopen_log();
        return UPAP_AUTHNAK;
    }
    /*
     * Define the fields for the credential validation
     */
     
    PAM_username = user;
    PAM_password = passwd;
    PAM_error = 0;
    pam_set_item (pamh, PAM_TTY, devnam); /* this might be useful to some modules */

    /*
     * Validate the user
     */
    pam_error = pam_authenticate (pamh, PAM_SILENT);
    if (pam_error == PAM_SUCCESS && !PAM_error) {    
        pam_error = pam_acct_mgmt (pamh, PAM_SILENT);
        if (pam_error == PAM_SUCCESS)
            pam_open_session (pamh, PAM_SILENT);
    }

    *msg = (char *) pam_strerror (pamh, pam_error);

    /*
     * Clean up the mess
     */
    reopen_log();       /* apparently the PAM stuff does closelog() */
    PAM_username = NULL;
    PAM_password = NULL;
    if (pam_error != PAM_SUCCESS)
        return UPAP_AUTHNAK;
#else /* #ifdef USE_PAM */

/*
 * Use the non-PAM methods directly
 */

#ifdef HAS_SHADOW
    struct spwd *spwd;
    struct spwd *getspnam();
#endif
    struct passwd *pw = getpwnam(user);

    endpwent();
    if (pw == NULL)
        return (UPAP_AUTHNAK);

#ifdef HAS_SHADOW
    spwd = getspnam(user);
    endspent();
    if (spwd) {
        /* check the age of the password entry */
        long now = time(NULL) / 86400L;

        if ((spwd->sp_expire > 0 && now >= spwd->sp_expire)
            || ((spwd->sp_max >= 0 && spwd->sp_max < 10000)
                && spwd->sp_lstchg >= 0
                && now >= spwd->sp_lstchg + spwd->sp_max)) {
            warn("Password for %s has expired", user);
            return (UPAP_AUTHNAK);
        }
        pw->pw_passwd = spwd->sp_pwdp;
    }
#endif

    /*
     * If no passwd, don't let them login.
     */
    if (pw->pw_passwd == NULL || strlen(pw->pw_passwd) < 2
        || strcmp(crypt(passwd, pw->pw_passwd), pw->pw_passwd) != 0)
        return (UPAP_AUTHNAK);

#endif /* #ifdef USE_PAM */

    /*
     * 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) && !defined(USE_PAM)
    if (pw != (struct passwd *)NULL) {
            struct lastlog ll;
            int fd;

            if ((fd = open(_PATH_LASTLOG, O_RDWR, 0)) >= 0) {
                (void)lseek(fd, (off_t)(pw->pw_uid * sizeof(ll)), SEEK_SET);
                memset((void *)&ll, 0, sizeof(ll));
                (void)time(&ll.ll_time);
                (void)strncpy(ll.ll_line, tty, sizeof(ll.ll_line));
                (void)write(fd, (char *)&ll, sizeof(ll));
                (void)close(fd);
            }
    }
#endif /* _PATH_LASTLOG and not USE_PAM */

    info("user %s logged in", user);
    logged_in = 1;

    return (UPAP_AUTHACK);
}

/*
 * plogout - Logout the user.
 */
static void
plogout()
{
#ifdef USE_PAM
    int pam_error;

    if (pamh != NULL) {
        pam_error = pam_close_session (pamh, PAM_SILENT);
        pam_end (pamh, pam_error);
        pamh = NULL;
    }
    /* Apparently the pam stuff does closelog(). */
    reopen_log();
#else /* ! USE_PAM */   
    char *tty;

    tty = devnam;
    if (strncmp(tty, "/dev/", 5) == 0)
        tty += 5;
    logwtmp(tty, "", "");               /* Wipe out utmp logout entry */
#endif /* ! USE_PAM */
    logged_in = 0;
}


/*
 * 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(unit)
    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, secret, &addrs, filename);
    ret = i >= 0 && (i & NONWILD_CLIENT) != 0 && secret[0] == 0;
    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.
 * Assumes passwd points to MAXSECRETLEN bytes of space (if non-null).
 */
static int
get_pap_passwd(passwd)
    char *passwd;
{
    char *filename;
    FILE *f;
    int ret;
    struct wordlist *addrs;
    char secret[MAXWORDLEN];

    filename = _PATH_UPAPFILE;
    addrs = NULL;
    f = fopen(filename, "r");
    if (f == NULL)
        return 0;
    check_access(f, filename);
    ret = scan_authfile(f, user,
                        (remote_name[0]? remote_name: NULL),
                        secret, NULL, filename);
    fclose(f);
    if (ret < 0)
        return 0;
    if (passwd != NULL)
        strlcpy(passwd, secret, MAXSECRETLEN);
    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(lacks_ipp)
    int *lacks_ipp;
{
    FILE *f;
    int ret;
    char *filename;
    struct wordlist *addrs;

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

    ret = scan_authfile(f, (explicit_remote? remote_name: NULL), our_name,
                        NULL, &addrs, filename);
    fclose(f);
    if (ret >= 0 && !some_ip_ok(addrs)) {
        if (lacks_ipp != 0)
            *lacks_ipp = 1;
        ret = -1;
    }
    if (addrs != 0)
        free_wordlist(addrs);

    return ret >= 0;
}


/*
 * 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(client, server, need_ip, lacks_ipp)
    char *client;
    char *server;
    int need_ip;
    int *lacks_ipp;
{
    FILE *f;
    int ret;
    char *filename;
    struct wordlist *addrs;

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

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

    ret = scan_authfile(f, client, server, NULL, &addrs, filename);
    fclose(f);
    if (ret >= 0 && need_ip && !some_ip_ok(addrs)) {
        if (lacks_ipp != 0)
            *lacks_ipp = 1;
        ret = -1;
    }
    if (addrs != 0)
        free_wordlist(addrs);

    return ret >= 0;
}


/*
 * 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(unit, client, server, secret, secret_len, save_addrs)
    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) {
        error("Can't open chap secret file %s: %m", filename);
        return 0;
    }
    check_access(f, filename);

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

    if (save_addrs)
        set_allowed_addrs(unit, addrs);

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

    return 1;
}

/*
 * set_allowed_addrs() - set the list of allowed addresses.
 */
static void
set_allowed_addrs(unit, addrs)
    int unit;
    struct wordlist *addrs;
{
    int n = 0;
    struct wordlist *ap;
    struct permitted_ip *ip;
    char *ptr_word, *ptr_mask;
    struct hostent *hp;
    struct netent *np;
    u_int32_t a, mask, ah;
    struct ipcp_options *wo = &ipcp_wantoptions[unit];
    u_int32_t suggested_ip = 0;

    if (addresses[unit] != NULL)
        free(addresses[unit]);
    addresses[unit] = NULL;

    for (ap = addrs; ap != NULL; ap = ap->next)
        ++n;
    if (n == 0)
        return;
    ip = (struct permitted_ip *) malloc((n + 1) * sizeof(struct permitted_ip));
    if (ip == 0)
        return;

    n = 0;
    for (ap = addrs; ap != NULL; ap = ap->next) {
        /* "-" means no addresses authorized, "*" means any address allowed */
        ptr_word = ap->word;
        if (strcmp(ptr_word, "-") == 0)
            break;
        if (strcmp(ptr_word, "*") == 0) {
            ip[n].permit = 1;
            ip[n].base = ip[n].mask = 0;
            ++n;
            break;
        }

        ip[n].permit = 1;
        if (*ptr_word == '!') {
            ip[n].permit = 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) {
                warn("invalid address length %v 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) {
            a = *(u_int32_t *)hp->h_addr;
        } else {
            np = getnetbyname (ptr_word);
            if (np != NULL && np->n_addrtype == AF_INET) {
                a = htonl (*(u_int32_t *)np->n_net);
                if (ptr_mask == NULL) {
                    /* calculate appropriate mask for net */
                    ah = ntohl(a);
                    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;
                }
            } else {
                a = inet_addr (ptr_word);
            }
        }

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

        if (a == (u_int32_t)-1L)
            warn("unknown host %s in auth. address list", ap->word);
        else {
            ip[n].mask = htonl(mask);
            ip[n].base = a & ip[n].mask;
            ++n;
            if (~mask == 0 && suggested_ip == 0)
                suggested_ip = a;
        }
    }

    ip[n].permit = 0;           /* make the last entry forbid all addresses */
    ip[n].base = 0;             /* to terminate the list */
    ip[n].mask = 0;

    addresses[unit] = ip;

    /*
     * If the address given for the peer isn't authorized, or if
     * the user hasn't given one, AND there is an authorized address
     * which is a single host, then use that if we find one.
     */
    if (suggested_ip != 0
        && (wo->hisaddr == 0 || !auth_ip_addr(unit, wo->hisaddr)))
        wo->hisaddr = suggested_ip;
}

/*
 * 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(unit, addr)
    int unit;
    u_int32_t addr;
{
    if (addresses[unit] == NULL) {
        if (auth_required)
            return 0;           /* no addresses authorized */
        return allow_any_ip || !have_route_to(addr);
    }
    return ip_addr_check(addr, addresses[unit]);
}

static int
ip_addr_check(addr, addrs)
    u_int32_t addr;
    struct permitted_ip *addrs;
{
    /* don't allow loopback or multicast address */
    if (bad_ip_adrs(addr))
        return 0;

    for (; ; ++addrs)
        if ((addr & addrs->mask) == addrs->base)
            return addrs->permit;
}

/*
 * 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(addr)
    u_int32_t addr;
{
    addr = ntohl(addr);
    return (addr >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET
        || IN_MULTICAST(addr) || IN_BADCLASS(addr);
}

/*
 * some_ip_ok - check a wordlist to see if it authorizes any
 * IP address(es).
 */
static int
some_ip_ok(addrs)
    struct wordlist *addrs;
{
    for (; addrs != 0; addrs = addrs->next) {
        if (strcmp(addrs->word, "-") == 0)
            break;
        if (addrs->word[0] != '!')
            return 1;           /* some IP address is allowed */
    }
    return 0;
}

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

    if (fstat(fileno(f), &sbuf) < 0) {
        warn("cannot stat secret file %s: %m", filename);
    } else if ((sbuf.st_mode & (S_IRWXG | S_IRWXO)) != 0) {
        warn("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.
 * We assume secret is NULL or points to MAXWORDLEN bytes of space.
 */
static int
scan_authfile(f, client, server, secret, addrs, filename)
    FILE *f;
    char *client;
    char *server;
    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 (!ISWILD(word)) {
            if (server != NULL && strcmp(word, server) != 0)
                continue;
            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) {
                warn("can't open indirect secret file %s", atfile);
                continue;
            }
            check_access(sf, atfile);
            if (!getword(sf, word, &xxx, atfile)) {
                warn("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 (;;) {
            if (!getword(f, word, &newline, filename) || newline)
                break;
            ap = (struct wordlist *) malloc(sizeof(struct wordlist));
            if (ap == NULL)
                novm("authorized addresses");
            ap->next = NULL;
            ap->word = strdup(word);
            if (ap->word == NULL)
                novm("authorized address");
            if (alist == NULL)
                alist = ap;
            else
                alast->next = ap;
            alast = ap;
        }

        /*
         * 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(wp)
    struct wordlist *wp;
{
    struct wordlist *next;

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

/*
 * auth_script_done - called when the auth-up or auth-down script
 * has finished.
 */
static void
auth_script_done(arg)
    void *arg;
{
    auth_script_pid = 0;
    switch (auth_script_state) {
    case s_up:
        if (auth_state == s_down) {
            auth_script_state = s_down;
            auth_script(_PATH_AUTHDOWN);
        }
        break;
    case s_down:
        if (auth_state == s_up) {
            auth_script_state = s_up;
            auth_script(_PATH_AUTHUP);
        }
        break;
    }
}

/*
 * auth_script - execute a script with arguments
 * interface-name peer-name real-user tty speed
 */
static void
auth_script(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 {
        slprintf(struid, sizeof(struid), "%d", getuid());
        user_name = struid;
    }
    slprintf(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;

    auth_script_pid = run_program(script, argv, 0, auth_script_done, NULL);
}