usr.bin/pppd/chap.c

/*
 * chap.c - Challenge Handshake Authentication Protocol.
 *
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 *
 * 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) 1991 Gregory M. Christy.
 * 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 Gregory M. Christy.  The name of the author 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.
 */

#define RCSID   "$Id: chap.c,v 1.24 1999/11/15 01:51:50 paulus Exp $"

/*
 * TODO:
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/time.h>

#include "pppd.h"
#include "chap.h"
#include "md5.h"
#if defined(CHAPMS) || defined(CHAPMSV2)
#include "chap_ms.h"
#endif

#if !defined(lint) && !defined(_lint)
static const char rcsid[] = RCSID;
#endif

/*
 * Command-line options.
 */
static option_t chap_option_list[] = {
    { "chap-restart", o_int, &chap[0].timeouttime,
      "Set CHAP Challenge retry interval" },
    { "chap-max-challenge", o_int, &chap[0].max_transmits,
      "Max number of Challenges sent without a valid response" },
    { "chap-interval", o_int, &chap[0].chal_interval,
      "Set interval for rechallenge" },
#if defined(CHAPMS) && defined(MSLANMAN)
    { "ms-lanman", o_bool, &ms_lanman,
      "Use obsolete LAN Manager password when using MS-CHAP", 1 },
#endif
    { NULL }
};

/*
 * Protocol entry points.
 */
static void ChapInit __P((int));
static void ChapLowerUp __P((int));
static void ChapLowerDown __P((int));
static void ChapInput __P((int, u_char *, int));
static void ChapProtocolReject __P((int));
static int  ChapPrintPkt __P((u_char *, int,
    void (*) __P((void *, const char *, ...)), void *));

struct protent chap_protent = {
    PPP_CHAP,           /* PPP protocol number */
    ChapInit,           /* Initialization procedure */
    ChapInput,          /* Process a received packet */
    ChapProtocolReject,     /* Process a received protocol-reject */
    ChapLowerUp,        /* Lower layer has come up */
    ChapLowerDown,      /* Lower layer has gone down */
    NULL,           /* Open the protocol */
    NULL,           /* Close the protocol */
    ChapPrintPkt,       /* Print a packet in readable form */
    NULL,           /* Process a received data packet */
    1,              /* 0 iff protocol is disabled */
    "CHAP",         /* Text name of protocol */
    NULL,           /* Text name of corresponding data protocol */
    chap_option_list,       /* List of command-line options */
    NULL,           /* Check requested options, assign defaults */
    NULL,           /* Configure interface for demand-dial */
    NULL            /* Say whether to bring up link for this pkt */
};

/* Not static'd for plug-ins */
chap_state chap[NUM_PPP];       /* CHAP state; one for each unit */

static void ChapChallengeTimeout __P((void *));
static void ChapResponseTimeout __P((void *));
static void ChapReceiveChallenge __P((chap_state *, u_char *, int, int));
static void ChapRechallenge __P((void *));
static void ChapReceiveResponse __P((chap_state *, u_char *, int, int));
static void ChapReceiveSuccess __P((chap_state *, u_char *, int, int));
static void ChapReceiveFailure __P((chap_state *, u_char *, int, int));
static void ChapSendStatus __P((chap_state *, int));
static void ChapSendChallenge __P((chap_state *));
static void ChapSendResponse __P((chap_state *));
static void ChapGenChallenge __P((chap_state *));

static const char *
chap_cstate(int clientstate)
{
    static const char *cstate[] = { CHAPCS__LIST };
    static char buf[32];

    if (clientstate < 0 || clientstate >= Dim(cstate)) {
    (void) slprintf(buf, sizeof(buf), "#%d", clientstate);
    return (buf);
    }
    return cstate[clientstate];
}

static const char *
chap_sstate(int serverstate)
{
    static const char *sstate[] = { CHAPSS__LIST };
    static char buf[32];

    if (serverstate < 0 || serverstate >= Dim(sstate)) {
    (void) slprintf(buf, sizeof(buf), "#%d", serverstate);
    return (buf);
    }
    return sstate[serverstate];
}

/*
 * ChapInit - Initialize a CHAP unit.
 */
static void
ChapInit(unit)
    int unit;
{
    chap_state *cstate = &chap[unit];

    BZERO(cstate, sizeof(*cstate));
    cstate->unit = unit;
    cstate->clientstate = CHAPCS_INITIAL;
    cstate->serverstate = CHAPSS_INITIAL;
    cstate->timeouttime = CHAP_DEFTIMEOUT;
    cstate->max_transmits = CHAP_DEFTRANSMITS;

    /* XXX save get_first_hwaddr() here. */
    /* random number generator is initialized in magic_init */
}


/*
 * ChapAuthWithPeer - Authenticate us with our peer (start client).
 *
 */
void
ChapAuthWithPeer(unit, our_name, digest)
    int unit;
    char *our_name;
    int digest;
{
    chap_state *cstate = &chap[unit];

    cstate->resp_name = our_name;
    cstate->resp_type = digest;

    if (cstate->clientstate == CHAPCS_INITIAL ||
    cstate->clientstate == CHAPCS_PENDING) {
    /* lower layer isn't up - wait until later */
    cstate->clientstate = CHAPCS_PENDING;
    return;
    }

    /*
     * We get here as a result of LCP coming up.
     * So even if CHAP was open before, we will
     * have to re-authenticate ourselves.
     */
    cstate->clientstate = CHAPCS_LISTEN;
}


/*
 * ChapAuthPeer - Authenticate our peer (start server).
 */
void
ChapAuthPeer(unit, our_name, digest)
    int unit;
    char *our_name;
    int digest;
{
    chap_state *cstate = &chap[unit];

    cstate->chal_name = our_name;
    cstate->chal_type = digest;

    if (cstate->serverstate == CHAPSS_INITIAL ||
    cstate->serverstate == CHAPSS_PENDING) {
    /* lower layer isn't up - wait until later */
    cstate->serverstate = CHAPSS_PENDING;
    return;
    }

    ChapGenChallenge(cstate);
    ChapSendChallenge(cstate);      /* crank it up dude! */
    cstate->serverstate = CHAPSS_INITIAL_CHAL;
}


/*
 * ChapChallengeTimeout - Timeout expired on sending challenge.
 */
static void
ChapChallengeTimeout(arg)
    void *arg;
{
    chap_state *cstate = (chap_state *) arg;

    /* if we aren't sending challenges, don't worry.  then again we */
    /* probably shouldn't be here either */
    if (cstate->serverstate != CHAPSS_INITIAL_CHAL &&
    cstate->serverstate != CHAPSS_RECHALLENGE)
    return;

    if (cstate->chal_transmits >= cstate->max_transmits) {
    /* give up on peer */
    error("Peer failed to respond to CHAP challenge");
    cstate->serverstate = CHAPSS_BADAUTH;
    auth_peer_fail(cstate->unit, PPP_CHAP);
    return;
    }

    ChapSendChallenge(cstate);      /* Re-send challenge */
}


/*
 * ChapResponseTimeout - Timeout expired on sending response.
 */
static void
ChapResponseTimeout(arg)
    void *arg;
{
    chap_state *cstate = (chap_state *) arg;

    /* if we aren't sending a response, don't worry. */
    if (cstate->clientstate != CHAPCS_RESPONSE)
    return;

    ChapSendResponse(cstate);       /* re-send response */
}


/*
 * ChapRechallenge - Time to challenge the peer again.
 */
static void
ChapRechallenge(arg)
    void *arg;
{
    chap_state *cstate = (chap_state *) arg;

    /* if we aren't sending a response, don't worry. */
    if (cstate->serverstate != CHAPSS_OPEN)
    return;

    ChapGenChallenge(cstate);
    ChapSendChallenge(cstate);
    cstate->serverstate = CHAPSS_RECHALLENGE;
}


/*
 * ChapLowerUp - The lower layer is up.
 *
 * Start up if we have pending requests.
 */
static void
ChapLowerUp(unit)
    int unit;
{
    chap_state *cstate = &chap[unit];

    if (cstate->clientstate == CHAPCS_INITIAL)
    cstate->clientstate = CHAPCS_CLOSED;
    else if (cstate->clientstate == CHAPCS_PENDING)
    cstate->clientstate = CHAPCS_LISTEN;

    if (cstate->serverstate == CHAPSS_INITIAL)
    cstate->serverstate = CHAPSS_CLOSED;
    else if (cstate->serverstate == CHAPSS_PENDING) {
    ChapGenChallenge(cstate);
    ChapSendChallenge(cstate);
    cstate->serverstate = CHAPSS_INITIAL_CHAL;
    }
}


/*
 * ChapLowerDown - The lower layer is down.
 *
 * Cancel all timeouts.
 */
static void
ChapLowerDown(unit)
    int unit;
{
    chap_state *cstate = &chap[unit];

    /* Timeout(s) pending?  Cancel if so. */
    if (cstate->serverstate == CHAPSS_INITIAL_CHAL ||
    cstate->serverstate == CHAPSS_RECHALLENGE)
    UNTIMEOUT(ChapChallengeTimeout, cstate);
    else if (cstate->serverstate == CHAPSS_OPEN
         && cstate->chal_interval != 0)
    UNTIMEOUT(ChapRechallenge, cstate);
    if (cstate->clientstate == CHAPCS_RESPONSE)
    UNTIMEOUT(ChapResponseTimeout, cstate);

    cstate->clientstate = CHAPCS_INITIAL;
    cstate->serverstate = CHAPSS_INITIAL;
}


/*
 * ChapProtocolReject - Peer doesn't grok CHAP.
 */
static void
ChapProtocolReject(unit)
    int unit;
{
    chap_state *cstate = &chap[unit];

    if (cstate->serverstate != CHAPSS_INITIAL &&
    cstate->serverstate != CHAPSS_CLOSED)
    auth_peer_fail(unit, PPP_CHAP);
    if (cstate->clientstate != CHAPCS_INITIAL &&
    cstate->clientstate != CHAPCS_CLOSED)
    auth_withpeer_fail(unit, PPP_CHAP);
    ChapLowerDown(unit);        /* shutdown chap */
}


/*
 * ChapInput - Input CHAP packet.
 */
static void
ChapInput(unit, inpacket, packet_len)
    int unit;
    u_char *inpacket;
    int packet_len;
{
    chap_state *cstate = &chap[unit];
    u_char *inp;
    u_char code, id;
    int len;

    /*
     * Parse header (code, id and length).
     * If packet too short, drop it.
     */
    inp = inpacket;
    if (packet_len < CHAP_HEADERLEN) {
    error("CHAP: packet is too small (%d < %d)", packet_len,
        CHAP_HEADERLEN);
    return;
    }
    GETCHAR(code, inp);
    GETCHAR(id, inp);
    GETSHORT(len, inp);
    if (len < CHAP_HEADERLEN || len > packet_len) {
    error("CHAP: packet has illegal length %d (%d..%d)",
        len, CHAP_HEADERLEN, packet_len);
    return;
    }
    len -= CHAP_HEADERLEN;

    /*
     * Action depends on code (as in fact it usually does :-).
     */
    switch (code) {
    case CHAP_CHALLENGE:
    ChapReceiveChallenge(cstate, inp, id, len);
    break;

    case CHAP_RESPONSE:
    ChapReceiveResponse(cstate, inp, id, len);
    break;

    case CHAP_FAILURE:
    ChapReceiveFailure(cstate, inp, id, len);
    break;

    case CHAP_SUCCESS:
    ChapReceiveSuccess(cstate, inp, id, len);
    break;

    default:
    /* CHAP does not define a code reject. */
    warn("Unknown CHAP code (%d) received.", code);
    break;
    }
}


/*
 * ChapReceiveChallenge - Receive Challenge and send Response.
 */
static void
ChapReceiveChallenge(cstate, inp, id, len)
    chap_state *cstate;
    u_char *inp;
    int id;
    int len;
{
    int rchallenge_len;
    u_char *rchallenge;
    int secret_len;
    char rhostname[MAXNAMELEN];
    char secret[MAXSECRETLEN];
    MD5_CTX mdContext;
    u_char hash[MD5_SIGNATURE_SIZE];
    int fake_response = 0;

    if (cstate->clientstate == CHAPCS_CLOSED ||
    cstate->clientstate == CHAPCS_PENDING) {
    if (debug)
        dbglog("CHAP Challenge unexpectedly received in state %s",
        chap_cstate(cstate->clientstate));
    return;
    }

    if (len < 2) {
    error("CHAP: Challenge message length %d", len);
    return;
    }

    GETCHAR(rchallenge_len, inp);
    len -= sizeof (u_char) + rchallenge_len;    /* now name field length */
    if (len < 0) {
    error("CHAP: Challenge truncated");
    return;
    }
    rchallenge = inp;
    INCPTR(rchallenge_len, inp);

    if (len >= sizeof(rhostname))
    len = sizeof(rhostname) - 1;
    if (len > 0) {
    BCOPY(inp, rhostname, len);
    }
    rhostname[len] = '\0';

#ifdef CHECK_CHALLENGE_LENGTH
    if (rchallenge_len < CHECK_CHALLENGE_LENGTH) {
    warn("CHAP: Challenge from %s unreasonably short (%d octets)",
        rhostname, rchallenge_len);
    fake_response = 1;
    }
#endif

    /* XXX compare against saved get_first_hwaddr() here. */

    /* Microsoft NT doesn't send a name in the CHAP Challenge message */
    if (explicit_remote ||
    (remote_name[0] != '\0' && rhostname[0] == '\0')) {
    (void) strlcpy(rhostname, remote_name, sizeof(rhostname));
    if (debug)
        dbglog("CHAP:  Peer gave no name; using '%q' as remote name",
        rhostname);
    }

    if (cstate->peercname[0] == '\0') {
    (void) strlcpy(cstate->peercname, rhostname,
        sizeof (cstate->peercname));
    } else if (strcmp(rhostname, cstate->peercname) != 0) {
    if (++cstate->rename_count == 1) {
        info("CHAP: peer challenge name changed from '%q' to '%q'",
        cstate->peercname, rhostname);
        (void) strlcpy(cstate->peercname, rhostname,
        sizeof (cstate->peercname));
    } else {
        fake_response = 1;
        if (cstate->rename_count == 2)
        warn("CHAP: peer challenge name changed again to '%q'",
            rhostname);
    }
    }

    /* get secret for authenticating ourselves with the specified host */
    if (!get_secret(cstate->unit, cstate->resp_name, rhostname,
            secret, &secret_len, 0)) {
    secret_len = 0;     /* assume null secret if can't find one */
    warn("No CHAP secret found for authenticating us (%q) to %q",
        cstate->resp_name, rhostname);
    }

    /* cancel response send timeout if necessary */
    if (cstate->clientstate == CHAPCS_RESPONSE)
    UNTIMEOUT(ChapResponseTimeout, cstate);

    cstate->resp_id = id;
    cstate->resp_transmits = 0;

    /*  generate MD based on negotiated type */
    switch (cstate->resp_type) {

    case CHAP_DIGEST_MD5:
    MD5Init(&mdContext);
    MD5Update(&mdContext, &cstate->resp_id, 1);
    MD5Update(&mdContext, (u_char *)secret, (unsigned)secret_len);
    MD5Update(&mdContext, rchallenge, rchallenge_len);
    MD5Final(hash, &mdContext);
    if (fake_response) {
        for (len = 0; len < MD5_SIGNATURE_SIZE; len++)
        cstate->response[len] = (char) (drand48() * 0xff);
    } else {
        BCOPY(hash, cstate->response, MD5_SIGNATURE_SIZE);
    }
    cstate->resp_length = MD5_SIGNATURE_SIZE;
    break;

#ifdef CHAPMS
    case CHAP_MICROSOFT:
    ChapMS(cstate, rchallenge, rchallenge_len, secret, secret_len);
    break;
#endif

#ifdef CHAPMSV2
    case CHAP_MICROSOFT_V2:
    ChapMSv2(cstate, rchallenge, rchallenge_len, secret, secret_len);
    break;
#endif

    default:
    error("CHAP: unknown digest type %d", cstate->resp_type);
    return;
    }

    BZERO(secret, sizeof(secret));
    ChapSendResponse(cstate);
}


/*
 * ChapReceiveResponse - Receive and process response.
 */
static void
ChapReceiveResponse(cstate, inp, id, len)
    chap_state *cstate;
    u_char *inp;
    int id;
    int len;
{
    u_char *remmd, remmd_len;
    int secret_len, old_state;
    int code;
    char rhostname[MAXNAMELEN], *rhn;
    MD5_CTX mdContext;
    char secret[MAXSECRETLEN];
    u_char hash[MD5_SIGNATURE_SIZE];

    if (cstate->serverstate == CHAPSS_CLOSED ||
    cstate->serverstate == CHAPSS_PENDING) {
    if (debug)
        dbglog("CHAP Response unexpectedly received in state %s",
        chap_sstate(cstate->serverstate));
    return;
    }

    if (id != cstate->chal_id) {
    if (debug)
        dbglog("CHAP: discard response %d; expecting %d", id,
        cstate->chal_id);
    return;         /* doesn't match ID of last challenge */
    }

    /*
     * If we have received a duplicate or bogus Response,
     * we have to send the same answer (Success/Failure)
     * as we did for the first Response we saw.
     */
    if (cstate->serverstate == CHAPSS_OPEN) {
    if (debug)
        dbglog("CHAP ignoring response and resending success message");
    ChapSendStatus(cstate, CHAP_SUCCESS);
    return;
    }
    if (cstate->serverstate == CHAPSS_BADAUTH) {
    if (debug)
        dbglog("CHAP ignoring response and resending failure message");
    ChapSendStatus(cstate, CHAP_FAILURE);
    return;
    }

    if (len < 2) {
    error("CHAP: Response message length %d", len);
    return;
    }
    GETCHAR(remmd_len, inp);        /* get length of MD */
    remmd = inp;            /* get pointer to MD */
    INCPTR(remmd_len, inp);

    len -= sizeof (u_char) + remmd_len;
    if (len < 0) {
    error("CHAP: Response truncated");
    return;
    }

    UNTIMEOUT(ChapChallengeTimeout, cstate);

    if (len >= sizeof(rhostname))
    len = sizeof(rhostname) - 1;
    BCOPY(inp, rhostname, len);
    rhostname[len] = '\0';

    /*
     * Get secret for authenticating them with us,
     * do the hash ourselves, and compare the result.
     */
    code = CHAP_FAILURE;
    rhn = (explicit_remote? remote_name: rhostname);
    if (cstate->serverstate == CHAPSS_RECHALLENGE &&
    strcmp(rhostname, peer_authname) != 0) {
    warn("Peer changed his name from '%q' to '%q' on rechallenge",
        peer_authname, rhostname);
    } else if (!get_secret(cstate->unit, rhn, cstate->chal_name, secret,
    &secret_len, 1)) {
    warn("No CHAP secret found for authenticating %q to us (%q)",
        rhn, cstate->chal_name);
    } else {

    /*  generate MD based on negotiated type */
    switch (cstate->chal_type) {

    case CHAP_DIGEST_MD5:       /* only MD5 is defined for now */
        if (remmd_len != MD5_SIGNATURE_SIZE)
        break;          /* it's not even the right length */
        MD5Init(&mdContext);
        MD5Update(&mdContext, &cstate->chal_id, 1);
        MD5Update(&mdContext, (u_char *)secret, secret_len);
        MD5Update(&mdContext, cstate->challenge, cstate->chal_len);
        MD5Final(hash, &mdContext);

        /* compare local and remote MDs and send the appropriate status */
        if (memcmp (hash, remmd, MD5_SIGNATURE_SIZE) == 0)
        code = CHAP_SUCCESS;    /* they are the same! */
        break;

#ifdef CHAPMS
    case CHAP_MICROSOFT:
        if (ChapMSValidate(cstate, remmd, remmd_len, secret,
            secret_len))
            code = CHAP_SUCCESS;
        break;
#endif

#ifdef CHAPMSV2
    case CHAP_MICROSOFT_V2:
        if (ChapMSv2Validate(cstate, rhostname, remmd, remmd_len,
            secret, secret_len))
            code = CHAP_SUCCESS;
        break;
#endif

    default:
        error("CHAP: unknown digest type %d", cstate->chal_type);
    }
    }

    BZERO(secret, sizeof(secret));
    ChapSendStatus(cstate, code);

    if (code == CHAP_SUCCESS) {
    old_state = cstate->serverstate;
    cstate->serverstate = CHAPSS_OPEN;
    if (old_state == CHAPSS_INITIAL_CHAL) {
        auth_peer_success(cstate->unit, PPP_CHAP, rhostname, len);
    }
    if (cstate->chal_interval != 0)
        TIMEOUT(ChapRechallenge, cstate, cstate->chal_interval);
    if (old_state == CHAPSS_INITIAL_CHAL)
        notice("CHAP peer authentication succeeded for %q", rhostname);
    else if (debug)
        dbglog("CHAP peer reauthentication succeeded for %q", rhostname);
    } else {
    error("CHAP peer %sauthentication failed for remote host %q",
        (cstate->serverstate == CHAPSS_INITIAL_CHAL ? "" : "re"),
        rhostname);
    cstate->serverstate = CHAPSS_BADAUTH;
    auth_peer_fail(cstate->unit, PPP_CHAP);
    }
}

/*
 * ChapReceiveSuccess - Receive Success
 */
/*ARGSUSED*/
static void
ChapReceiveSuccess(cstate, inp, id, len)
    chap_state *cstate;
    u_char *inp;
    u_char id;
    int len;
{

    if (cstate->clientstate == CHAPCS_OPEN) {
    /* presumably an answer to a duplicate response */
    if (debug)
        dbglog("CHAP duplicate Success message ignored");
    return;
    }

    if (cstate->clientstate != CHAPCS_RESPONSE) {
    /* don't know what this is */
    if (debug)
        dbglog("CHAP Success unexpectedly received in state %s",
        chap_cstate(cstate->clientstate));
    return;
    }

    UNTIMEOUT(ChapResponseTimeout, cstate);

    /*
     * Print message.
     */
    if (len > 0)
    PRINTMSG(inp, len);

    cstate->clientstate = CHAPCS_OPEN;

    auth_withpeer_success(cstate->unit, PPP_CHAP);
}


/*
 * ChapReceiveFailure - Receive failure.
 */
/*ARGSUSED*/
static void
ChapReceiveFailure(cstate, inp, id, len)
    chap_state *cstate;
    u_char *inp;
    u_char id;
    int len;
{
    if (cstate->clientstate != CHAPCS_RESPONSE) {
    /* don't know what this is */
    if (debug)
        dbglog("CHAP Failure unexpectedly received in state %s",
        chap_cstate(cstate->clientstate));
    return;
    }

    UNTIMEOUT(ChapResponseTimeout, cstate);

    /*
     * Print message.
     */
    if (len > 0)
    PRINTMSG(inp, len);

    error("CHAP authentication failed");
    auth_withpeer_fail(cstate->unit, PPP_CHAP);
}


/*
 * ChapSendChallenge - Send an Authenticate challenge.
 */
static void
ChapSendChallenge(cstate)
    chap_state *cstate;
{
    u_char *outp;
    int chal_len, name_len;
    int outlen;

    chal_len = cstate->chal_len;
    name_len = strlen(cstate->chal_name);
    outlen = CHAP_HEADERLEN + sizeof (u_char) + chal_len + name_len;
    outp = outpacket_buf;

    MAKEHEADER(outp, PPP_CHAP);     /* paste in a CHAP header */

    PUTCHAR(CHAP_CHALLENGE, outp);
    PUTCHAR(cstate->chal_id, outp);
    PUTSHORT(outlen, outp);

    PUTCHAR(chal_len, outp);        /* put length of challenge */
    BCOPY(cstate->challenge, outp, chal_len);
    INCPTR(chal_len, outp);

    BCOPY(cstate->chal_name, outp, name_len);   /* append hostname */

    output(cstate->unit, outpacket_buf, outlen + PPP_HDRLEN);

    TIMEOUT(ChapChallengeTimeout, cstate, cstate->timeouttime);
    ++cstate->chal_transmits;
}


/*
 * ChapSendStatus - Send a status response (ack or nak).
 */
static void
ChapSendStatus(cstate, code)
    chap_state *cstate;
    int code;
{
    u_char *outp;
    int outlen, msglen;
    char msg[256], *msgp;

    if ((msgp = cstate->stat_message) != NULL) {
    msglen = cstate->stat_length;
    } else {
    if (code == CHAP_SUCCESS)
        (void) slprintf(msg, sizeof(msg), "Welcome to %s.", hostname);
    else
        (void) slprintf(msg, sizeof(msg), "I don't like you.  Go 'way.");
    msglen = strlen(msg);
    msgp = msg;
    }

    outlen = CHAP_HEADERLEN + msglen;
    outp = outpacket_buf;

    MAKEHEADER(outp, PPP_CHAP); /* paste in a header */

    PUTCHAR(code, outp);
    PUTCHAR(cstate->chal_id, outp);
    PUTSHORT(outlen, outp);
    BCOPY(msgp, outp, msglen);
    output(cstate->unit, outpacket_buf, outlen + PPP_HDRLEN);
}

/*
 * ChapGenChallenge is used to generate a pseudo-random challenge string of
 * a pseudo-random length between min_len and max_len.  The challenge
 * string and its length are stored in *cstate, and various other fields of
 * *cstate are initialized.
 */

static void
ChapGenChallenge(cstate)
    chap_state *cstate;
{
    int chal_len;
    u_char *ptr = cstate->challenge;
    int i;

    /* pick a random challenge length between MIN_CHALLENGE_LENGTH and
       MAX_CHALLENGE_LENGTH */
    chal_len =  (unsigned) ((drand48() *
                 (MAX_CHALLENGE_LENGTH - MIN_CHALLENGE_LENGTH)) +
                MIN_CHALLENGE_LENGTH);
    cstate->chal_len = chal_len;
    cstate->chal_id = ++cstate->id;
    cstate->chal_transmits = 0;

    /* XXX tack on saved get_first_hwaddr() here. */

    /* generate a random string */
    for (i = 0; i < chal_len; i++)
    *ptr++ = (char) (drand48() * 0xff);
}

/*
 * ChapSendResponse - send a response packet with values as specified
 * in *cstate.
 */
/* ARGSUSED */
static void
ChapSendResponse(cstate)
    chap_state *cstate;
{
    u_char *outp;
    int outlen, md_len, name_len;

    md_len = cstate->resp_length;
    name_len = strlen(cstate->resp_name);
    outlen = CHAP_HEADERLEN + sizeof (u_char) + md_len + name_len;
    outp = outpacket_buf;

    MAKEHEADER(outp, PPP_CHAP);

    PUTCHAR(CHAP_RESPONSE, outp);   /* we are a response */
    PUTCHAR(cstate->resp_id, outp); /* copy id from challenge packet */
    PUTSHORT(outlen, outp);     /* packet length */

    PUTCHAR(md_len, outp);      /* length of MD */
    BCOPY(cstate->response, outp, md_len);  /* copy MD to buffer */
    INCPTR(md_len, outp);

    BCOPY(cstate->resp_name, outp, name_len); /* append our name */

    /* send the packet */
    output(cstate->unit, outpacket_buf, outlen + PPP_HDRLEN);

    cstate->clientstate = CHAPCS_RESPONSE;
    TIMEOUT(ChapResponseTimeout, cstate, cstate->timeouttime);
    ++cstate->resp_transmits;
}

/*
 * ChapPrintPkt - print the contents of a CHAP packet.
 */
static char *ChapCodenames[] = {
    "Challenge", "Response", "Success", "Failure"
};

static int
ChapPrintPkt(p, plen, printer, arg)
    u_char *p;
    int plen;
    void (*printer) __P((void *, const char *, ...));
    void *arg;
{
    int code, id, len;
    int clen, nlen;
    u_char x;

    if (plen < CHAP_HEADERLEN)
    return 0;
    GETCHAR(code, p);
    GETCHAR(id, p);
    GETSHORT(len, p);
    if (len < CHAP_HEADERLEN || len > plen)
    return 0;

    if (code >= 1 && code <= sizeof(ChapCodenames) / sizeof(char *))
    printer(arg, " %s", ChapCodenames[code-1]);
    else
    printer(arg, " code=0x%x", code);
    printer(arg, " id=0x%x", id);
    len -= CHAP_HEADERLEN;
    switch (code) {
    case CHAP_CHALLENGE:
    case CHAP_RESPONSE:
    if (len < 1)
        break;
    clen = p[0];
    if (len < clen + 1)
        break;
    ++p;
    nlen = len - clen - 1;
    printer(arg, " <");
    for (; clen > 0; --clen) {
        GETCHAR(x, p);
        printer(arg, "%.2x", x);
    }
    printer(arg, ">, name = ");
    print_string((char *)p, nlen, printer, arg);
    break;
    case CHAP_FAILURE:
    case CHAP_SUCCESS:
    printer(arg, " ");
    print_string((char *)p, len, printer, arg);
    break;
    default:
    for (clen = len; clen > 0; --clen) {
        GETCHAR(x, p);
        printer(arg, " %.2x", x);
    }
    }

    return len + CHAP_HEADERLEN;
}