text: /*
   * chap-new.c - New CHAP implementation.
   *
   * Copyright (c) 2003 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. 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.
   *
   * 3. 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.
   */
  
  #include "netif/ppp/ppp_opts.h"
  #if PPP_SUPPORT &&                                                             \
      CHAP_SUPPORT /* don't build if not configured for use in lwipopts.h */
  
  #if 0 /* UNUSED */
  #include <stdlib.h>
  #include <string.h>
  #endif /* UNUSED */
  
  #include "netif/ppp/ppp_impl.h"
  
  #if 0 /* UNUSED */
  #include "session.h"
  #endif /* UNUSED */
  
  #include "netif/ppp/chap-md5.h"
  #include "netif/ppp/chap-new.h"
  #if MSCHAP_SUPPORT
  #include "netif/ppp/chap_ms.h"
  #endif
  #include "netif/ppp/magic.h"
  
  #if 0  /* UNUSED */
  /* Hook for a plugin to validate CHAP challenge */
  int (*chap_verify_hook)(const char *name, const char *ourname, int id,
  			const struct chap_digest_type *digest,
  			const unsigned char *challenge, const unsigned char *response,
  			char *message, int message_space) = NULL;
  #endif /* UNUSED */
  
  #if PPP_OPTIONS
  /*
   * Command-line options.
   */
  static option_t chap_option_list[] = {
      {"chap-restart", o_int, &chap_timeout_time, "Set timeout for CHAP",
       OPT_PRIO},
      {"chap-max-challenge", o_int, &pcb->settings.chap_max_transmits,
       "Set max #xmits for challenge", OPT_PRIO},
      {"chap-interval", o_int, &pcb->settings.chap_rechallenge_time,
       "Set interval for rechallenge", OPT_PRIO},
      {NULL}};
  #endif /* PPP_OPTIONS */
  
  /* Values for flags in chap_client_state and chap_server_state */
  #define LOWERUP 1
  #define AUTH_STARTED 2
  #define AUTH_DONE 4
  #define AUTH_FAILED 8
  #define TIMEOUT_PENDING 0x10
  #define CHALLENGE_VALID 0x20
  
  /*
   * Prototypes.
   */
  static void chap_init(ppp_pcb *pcb);
  static void chap_lowerup(ppp_pcb *pcb);
  static void chap_lowerdown(ppp_pcb *pcb);
  #if PPP_SERVER
  static void chap_timeout(void *arg);
  static void chap_generate_challenge(ppp_pcb *pcb);
  static void chap_handle_response(ppp_pcb *pcb, int code, unsigned char *pkt,
                                   int len);
  static int chap_verify_response(ppp_pcb *pcb, const char *name,
                                  const char *ourname, int id,
                                  const struct chap_digest_type *digest,
                                  const unsigned char *challenge,
                                  const unsigned char *response, char *message,
                                  int message_space);
  #endif /* PPP_SERVER */
  static void chap_respond(ppp_pcb *pcb, int id, unsigned char *pkt, int len);
  static void chap_handle_status(ppp_pcb *pcb, int code, int id,
                                 unsigned char *pkt, int len);
  static void chap_protrej(ppp_pcb *pcb);
  static void chap_input(ppp_pcb *pcb, unsigned char *pkt, int pktlen);
  #if PRINTPKT_SUPPORT
  static int chap_print_pkt(const unsigned char *p, int plen,
                            void (*printer)(void *, const char *, ...),
                            void *arg);
  #endif /* PRINTPKT_SUPPORT */
  
  /* List of digest types that we know about */
  static const struct chap_digest_type *const chap_digests[] = {&md5_digest,
  #if MSCHAP_SUPPORT
                                                                &chapms_digest,
                                                                &chapms2_digest,
  #endif /* MSCHAP_SUPPORT */
                                                                NULL};
  
  /*
   * chap_init - reset to initial state.
   */
  static void chap_init(ppp_pcb *pcb) {
    LWIP_UNUSED_ARG(pcb);
  
  #if 0 /* Not necessary, everything is cleared in ppp_new() */
  	memset(&pcb->chap_client, 0, sizeof(chap_client_state));
  #if PPP_SERVER
  	memset(&pcb->chap_server, 0, sizeof(chap_server_state));
  #endif /* PPP_SERVER */
  #endif /* 0 */
  }
  
  /*
   * chap_lowerup - we can start doing stuff now.
   */
  static void chap_lowerup(ppp_pcb *pcb) {
  
    pcb->chap_client.flags |= LOWERUP;
  #if PPP_SERVER
    pcb->chap_server.flags |= LOWERUP;
    if (pcb->chap_server.flags & AUTH_STARTED)
      chap_timeout(pcb);
  #endif /* PPP_SERVER */
  }
  
  static void chap_lowerdown(ppp_pcb *pcb) {
  
    pcb->chap_client.flags = 0;
  #if PPP_SERVER
    if (pcb->chap_server.flags & TIMEOUT_PENDING)
      UNTIMEOUT(chap_timeout, pcb);
    pcb->chap_server.flags = 0;
  #endif /* PPP_SERVER */
  }
  
  #if PPP_SERVER
  /*
   * chap_auth_peer - Start authenticating the peer.
   * If the lower layer is already up, we start sending challenges,
   * otherwise we wait for the lower layer to come up.
   */
  void chap_auth_peer(ppp_pcb *pcb, const char *our_name, int digest_code) {
    const struct chap_digest_type *dp;
    int i;
  
    if (pcb->chap_server.flags & AUTH_STARTED) {
      ppp_error("CHAP: peer authentication already started!");
      return;
    }
    for (i = 0; (dp = chap_digests[i]) != NULL; ++i)
      if (dp->code == digest_code)
        break;
    if (dp == NULL)
      ppp_fatal("CHAP digest 0x%x requested but not available", digest_code);
  
    pcb->chap_server.digest = dp;
    pcb->chap_server.name = our_name;
    /* Start with a random ID value */
    pcb->chap_server.id = magic();
    pcb->chap_server.flags |= AUTH_STARTED;
    if (pcb->chap_server.flags & LOWERUP)
      chap_timeout(pcb);
  }
  #endif /* PPP_SERVER */
  
  /*
   * chap_auth_with_peer - Prepare to authenticate ourselves to the peer.
   * There isn't much to do until we receive a challenge.
   */
  void chap_auth_with_peer(ppp_pcb *pcb, const char *our_name, int digest_code) {
    const struct chap_digest_type *dp;
    int i;
  
    if (NULL == our_name)
      return;
  
    if (pcb->chap_client.flags & AUTH_STARTED) {
      ppp_error("CHAP: authentication with peer already started!");
      return;
    }
    for (i = 0; (dp = chap_digests[i]) != NULL; ++i)
      if (dp->code == digest_code)
        break;
  
    if (dp == NULL)
      ppp_fatal("CHAP digest 0x%x requested but not available", digest_code);
  
    pcb->chap_client.digest = dp;
    pcb->chap_client.name = our_name;
    pcb->chap_client.flags |= AUTH_STARTED;
  }
  
  #if PPP_SERVER
  /*
   * chap_timeout - It's time to send another challenge to the peer.
   * This could be either a retransmission of a previous challenge,
   * or a new challenge to start re-authentication.
   */
  static void chap_timeout(void *arg) {
    ppp_pcb *pcb = (ppp_pcb *)arg;
    struct pbuf *p;
  
    pcb->chap_server.flags &= ~TIMEOUT_PENDING;
    if ((pcb->chap_server.flags & CHALLENGE_VALID) == 0) {
      pcb->chap_server.challenge_xmits = 0;
      chap_generate_challenge(pcb);
      pcb->chap_server.flags |= CHALLENGE_VALID;
    } else if (pcb->chap_server.challenge_xmits >=
               pcb->settings.chap_max_transmits) {
      pcb->chap_server.flags &= ~CHALLENGE_VALID;
      pcb->chap_server.flags |= AUTH_DONE | AUTH_FAILED;
      auth_peer_fail(pcb, PPP_CHAP);
      return;
    }
  
    p = pbuf_alloc(PBUF_RAW, (u16_t)(pcb->chap_server.challenge_pktlen),
                   PPP_CTRL_PBUF_TYPE);
    if (NULL == p)
      return;
    if (p->tot_len != p->len) {
      pbuf_free(p);
      return;
    }
    MEMCPY(p->payload, pcb->chap_server.challenge,
           pcb->chap_server.challenge_pktlen);
    ppp_write(pcb, p);
    ++pcb->chap_server.challenge_xmits;
    pcb->chap_server.flags |= TIMEOUT_PENDING;
    TIMEOUT(chap_timeout, arg, pcb->settings.chap_timeout_time);
  }
  
  /*
   * chap_generate_challenge - generate a challenge string and format
   * the challenge packet in pcb->chap_server.challenge_pkt.
   */
  static void chap_generate_challenge(ppp_pcb *pcb) {
    int clen = 1, nlen, len;
    unsigned char *p;
  
    p = pcb->chap_server.challenge;
    MAKEHEADER(p, PPP_CHAP);
    p += CHAP_HDRLEN;
    pcb->chap_server.digest->generate_challenge(pcb, p);
    clen = *p;
    nlen = strlen(pcb->chap_server.name);
    memcpy(p + 1 + clen, pcb->chap_server.name, nlen);
  
    len = CHAP_HDRLEN + 1 + clen + nlen;
    pcb->chap_server.challenge_pktlen = PPP_HDRLEN + len;
  
    p = pcb->chap_server.challenge + PPP_HDRLEN;
    p[0] = CHAP_CHALLENGE;
    p[1] = ++pcb->chap_server.id;
    p[2] = len >> 8;
    p[3] = len;
  }
  
  /*
   * chap_handle_response - check the response to our challenge.
   */
  static void chap_handle_response(ppp_pcb *pcb, int id, unsigned char *pkt,
                                   int len) {
    int response_len, ok, mlen;
    const unsigned char *response;
    unsigned char *outp;
    struct pbuf *p;
    const char *name = NULL; /* initialized to shut gcc up */
  #if 0                      /* UNUSED */
  	int (*verifier)(const char *, const char *, int, const struct chap_digest_type *,
  		const unsigned char *, const unsigned char *, char *, int);
  #endif                     /* UNUSED */
    char rname[MAXNAMELEN + 1];
    char message[256];
  
    if ((pcb->chap_server.flags & LOWERUP) == 0)
      return;
    if (id != pcb->chap_server.challenge[PPP_HDRLEN + 1] || len < 2)
      return;
    if (pcb->chap_server.flags & CHALLENGE_VALID) {
      response = pkt;
      GETCHAR(response_len, pkt);
      len -= response_len + 1; /* length of name */
      name = (char *)pkt + response_len;
      if (len < 0)
        return;
  
      if (pcb->chap_server.flags & TIMEOUT_PENDING) {
        pcb->chap_server.flags &= ~TIMEOUT_PENDING;
        UNTIMEOUT(chap_timeout, pcb);
      }
  #if PPP_REMOTENAME
      if (pcb->settings.explicit_remote) {
        name = pcb->remote_name;
      } else
  #endif /* PPP_REMOTENAME */
      {
        /* Null terminate and clean remote name. */
        ppp_slprintf(rname, sizeof(rname), "%.*v", len, name);
        name = rname;
      }
  
  #if 0  /* UNUSED */
  		if (chap_verify_hook)
  			verifier = chap_verify_hook;
  		else
  			verifier = chap_verify_response;
  		ok = (*verifier)(name, pcb->chap_server.name, id, pcb->chap_server.digest,
  				 pcb->chap_server.challenge + PPP_HDRLEN + CHAP_HDRLEN,
  				 response, pcb->chap_server.message, sizeof(pcb->chap_server.message));
  #endif /* UNUSED */
      ok = chap_verify_response(
          pcb, name, pcb->chap_server.name, id, pcb->chap_server.digest,
          pcb->chap_server.challenge + PPP_HDRLEN + CHAP_HDRLEN, response,
          message, sizeof(message));
  #if 0  /* UNUSED */
  		if (!ok || !auth_number()) {
  #endif /* UNUSED */
      if (!ok) {
        pcb->chap_server.flags |= AUTH_FAILED;
        ppp_warn("Peer %q failed CHAP authentication", name);
      }
    } else if ((pcb->chap_server.flags & AUTH_DONE) == 0)
      return;
  
    /* send the response */
    mlen = strlen(message);
    len = CHAP_HDRLEN + mlen;
    p = pbuf_alloc(PBUF_RAW, (u16_t)(PPP_HDRLEN + len), PPP_CTRL_PBUF_TYPE);
    if (NULL == p)
      return;
    if (p->tot_len != p->len) {
      pbuf_free(p);
      return;
    }
  
    outp = (unsigned char *)p->payload;
    MAKEHEADER(outp, PPP_CHAP);
  
    outp[0] =
        (pcb->chap_server.flags & AUTH_FAILED) ? CHAP_FAILURE : CHAP_SUCCESS;
    outp[1] = id;
    outp[2] = len >> 8;
    outp[3] = len;
    if (mlen > 0)
      memcpy(outp + CHAP_HDRLEN, message, mlen);
    ppp_write(pcb, p);
  
    if (pcb->chap_server.flags & CHALLENGE_VALID) {
      pcb->chap_server.flags &= ~CHALLENGE_VALID;
      if (!(pcb->chap_server.flags & AUTH_DONE) &&
          !(pcb->chap_server.flags & AUTH_FAILED)) {
  
  #if 0  /* UNUSED */
  		    /*
  		     * Auth is OK, so now we need to check session restrictions
  		     * to ensure everything is OK, but only if we used a
  		     * plugin, and only if we're configured to check.  This
  		     * allows us to do PAM checks on PPP servers that
  		     * authenticate against ActiveDirectory, and use AD for
  		     * account info (like when using Winbind integrated with
  		     * PAM).
  		     */
  		    if (session_mgmt &&
  			session_check(name, NULL, devnam, NULL) == 0) {
  			pcb->chap_server.flags |= AUTH_FAILED;
  			ppp_warn("Peer %q failed CHAP Session verification", name);
  		    }
  #endif /* UNUSED */
      }
      if (pcb->chap_server.flags & AUTH_FAILED) {
        auth_peer_fail(pcb, PPP_CHAP);
      } else {
        if ((pcb->chap_server.flags & AUTH_DONE) == 0)
          auth_peer_success(pcb, PPP_CHAP, pcb->chap_server.digest->code, name,
                            strlen(name));
        if (pcb->settings.chap_rechallenge_time) {
          pcb->chap_server.flags |= TIMEOUT_PENDING;
          TIMEOUT(chap_timeout, pcb, pcb->settings.chap_rechallenge_time);
        }
      }
      pcb->chap_server.flags |= AUTH_DONE;
    }
  }
  
  /*
   * chap_verify_response - check whether the peer's response matches
   * what we think it should be.  Returns 1 if it does (authentication
   * succeeded), or 0 if it doesn't.
   */
  static int chap_verify_response(ppp_pcb *pcb, const char *name,
                                  const char *ourname, int id,
                                  const struct chap_digest_type *digest,
                                  const unsigned char *challenge,
                                  const unsigned char *response, char *message,
                                  int message_space) {
    int ok;
    unsigned char secret[MAXSECRETLEN];
    int secret_len;
  
    /* Get the secret that the peer is supposed to know */
    if (!get_secret(pcb, name, ourname, (char *)secret, &secret_len, 1)) {
      ppp_error("No CHAP secret found for authenticating %q", name);
      return 0;
    }
    ok = digest->verify_response(pcb, id, name, secret, secret_len, challenge,
                                 response, message, message_space);
    memset(secret, 0, sizeof(secret));
  
    return ok;
  }
  #endif /* PPP_SERVER */
  
  /*
   * chap_respond - Generate and send a response to a challenge.
   */
  static void chap_respond(ppp_pcb *pcb, int id, unsigned char *pkt, int len) {
    int clen, nlen;
    int secret_len;
    struct pbuf *p;
    u_char *outp;
    char rname[MAXNAMELEN + 1];
    char secret[MAXSECRETLEN + 1];
  
    p = pbuf_alloc(PBUF_RAW, (u16_t)(RESP_MAX_PKTLEN), PPP_CTRL_PBUF_TYPE);
    if (NULL == p)
      return;
    if (p->tot_len != p->len) {
      pbuf_free(p);
      return;
    }
  
    if ((pcb->chap_client.flags & (LOWERUP | AUTH_STARTED)) !=
        (LOWERUP | AUTH_STARTED))
      return; /* not ready */
    if (len < 2 || len < pkt[0] + 1)
      return; /* too short */
    clen = pkt[0];
    nlen = len - (clen + 1);
  
    /* Null terminate and clean remote name. */
    ppp_slprintf(rname, sizeof(rname), "%.*v", nlen, pkt + clen + 1);
  
  #if PPP_REMOTENAME
    /* Microsoft doesn't send their name back in the PPP packet */
    if (pcb->settings.explicit_remote ||
        (pcb->settings.remote_name[0] != 0 && rname[0] == 0))
      strlcpy(rname, pcb->settings.remote_name, sizeof(rname));
  #endif /* PPP_REMOTENAME */
  
    /* get secret for authenticating ourselves with the specified host */
    if (!get_secret(pcb, pcb->chap_client.name, rname, secret, &secret_len, 0)) {
      secret_len = 0; /* assume null secret if can't find one */
      ppp_warn("No CHAP secret found for authenticating us to %q", rname);
    }
  
    outp = (u_char *)p->payload;
    MAKEHEADER(outp, PPP_CHAP);
    outp += CHAP_HDRLEN;
  
    pcb->chap_client.digest->make_response(pcb, outp, id, pcb->chap_client.name,
                                           pkt, secret, secret_len,
                                           pcb->chap_client.priv);
    memset(secret, 0, secret_len);
  
    clen = *outp;
    nlen = strlen(pcb->chap_client.name);
    memcpy(outp + clen + 1, pcb->chap_client.name, nlen);
  
    outp = (u_char *)p->payload + PPP_HDRLEN;
    len = CHAP_HDRLEN + clen + 1 + nlen;
    outp[0] = CHAP_RESPONSE;
    outp[1] = id;
    outp[2] = len >> 8;
    outp[3] = len;
  
    pbuf_realloc(p, PPP_HDRLEN + len);
    ppp_write(pcb, p);
  }
  
  static void chap_handle_status(ppp_pcb *pcb, int code, int id,
                                 unsigned char *pkt, int len) {
    const char *msg = NULL;
    LWIP_UNUSED_ARG(id);
  
    if ((pcb->chap_client.flags & (AUTH_DONE | AUTH_STARTED | LOWERUP)) !=
        (AUTH_STARTED | LOWERUP))
      return;
    pcb->chap_client.flags |= AUTH_DONE;
  
    if (code == CHAP_SUCCESS) {
      /* used for MS-CHAP v2 mutual auth, yuck */
      if (pcb->chap_client.digest->check_success != NULL) {
        if (!(*pcb->chap_client.digest->check_success)(pcb, pkt, len,
                                                       pcb->chap_client.priv))
          code = CHAP_FAILURE;
      } else
        msg = "CHAP authentication succeeded";
    } else {
      if (pcb->chap_client.digest->handle_failure != NULL)
        (*pcb->chap_client.digest->handle_failure)(pcb, pkt, len);
      else
        msg = "CHAP authentication failed";
    }
    if (msg) {
      if (len > 0)
        ppp_info("%s: %.*v", msg, len, pkt);
      else
        ppp_info("%s", msg);
    }
    if (code == CHAP_SUCCESS)
      auth_withpeer_success(pcb, PPP_CHAP, pcb->chap_client.digest->code);
    else {
      pcb->chap_client.flags |= AUTH_FAILED;
      ppp_error("CHAP authentication failed");
      auth_withpeer_fail(pcb, PPP_CHAP);
    }
  }
  
  static void chap_input(ppp_pcb *pcb, unsigned char *pkt, int pktlen) {
    unsigned char code, id;
    int len;
  
    if (pktlen < CHAP_HDRLEN)
      return;
    GETCHAR(code, pkt);
    GETCHAR(id, pkt);
    GETSHORT(len, pkt);
    if (len < CHAP_HDRLEN || len > pktlen)
      return;
    len -= CHAP_HDRLEN;
  
    switch (code) {
    case CHAP_CHALLENGE:
      chap_respond(pcb, id, pkt, len);
      break;
  #if PPP_SERVER
    case CHAP_RESPONSE:
      chap_handle_response(pcb, id, pkt, len);
      break;
  #endif /* PPP_SERVER */
    case CHAP_FAILURE:
    case CHAP_SUCCESS:
      chap_handle_status(pcb, code, id, pkt, len);
      break;
    default:
      break;
    }
  }
  
  static void chap_protrej(ppp_pcb *pcb) {
  
  #if PPP_SERVER
    if (pcb->chap_server.flags & TIMEOUT_PENDING) {
      pcb->chap_server.flags &= ~TIMEOUT_PENDING;
      UNTIMEOUT(chap_timeout, pcb);
    }
    if (pcb->chap_server.flags & AUTH_STARTED) {
      pcb->chap_server.flags = 0;
      auth_peer_fail(pcb, PPP_CHAP);
    }
  #endif /* PPP_SERVER */
    if ((pcb->chap_client.flags & (AUTH_STARTED | AUTH_DONE)) == AUTH_STARTED) {
      pcb->chap_client.flags &= ~AUTH_STARTED;
      ppp_error("CHAP authentication failed due to protocol-reject");
      auth_withpeer_fail(pcb, PPP_CHAP);
    }
  }
  
  #if PRINTPKT_SUPPORT
  /*
   * chap_print_pkt - print the contents of a CHAP packet.
   */
  static const char *const chap_code_names[] = {"Challenge", "Response",
                                                "Success", "Failure"};
  
  static int chap_print_pkt(const unsigned char *p, int plen,
                            void (*printer)(void *, const char *, ...),
                            void *arg) {
    int code, id, len;
    int clen, nlen;
    unsigned char x;
  
    if (plen < CHAP_HDRLEN)
      return 0;
    GETCHAR(code, p);
    GETCHAR(id, p);
    GETSHORT(len, p);
    if (len < CHAP_HDRLEN || len > plen)
      return 0;
  
    if (code >= 1 && code <= (int)LWIP_ARRAYSIZE(chap_code_names))
      printer(arg, " %s", chap_code_names[code - 1]);
    else
      printer(arg, " code=0x%x", code);
    printer(arg, " id=0x%x", id);
    len -= CHAP_HDRLEN;
    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 = ");
      ppp_print_string(p, nlen, printer, arg);
      break;
    case CHAP_FAILURE:
    case CHAP_SUCCESS:
      printer(arg, " ");
      ppp_print_string(p, len, printer, arg);
      break;
    default:
      for (clen = len; clen > 0; --clen) {
        GETCHAR(x, p);
        printer(arg, " %.2x", x);
      }
      /* no break */
    }
  
    return len + CHAP_HDRLEN;
  }
  #endif /* PRINTPKT_SUPPORT */
  
  const struct protent chap_protent = {
    PPP_CHAP,
    chap_init,
    chap_input,
    chap_protrej,
    chap_lowerup,
    chap_lowerdown,
    NULL, /* open */
    NULL, /* close */
  #if PRINTPKT_SUPPORT
    chap_print_pkt,
  #endif /* PRINTPKT_SUPPORT */
  #if PPP_DATAINPUT
    NULL, /* datainput */
  #endif  /* PPP_DATAINPUT */
  #if PRINTPKT_SUPPORT
    "CHAP", /* name */
    NULL,   /* data_name */
  #endif    /* PRINTPKT_SUPPORT */
  #if PPP_OPTIONS
    chap_option_list,
    NULL, /* check_options */
  #endif  /* PPP_OPTIONS */
  #if DEMAND_SUPPORT
    NULL,
    NULL
  #endif /* DEMAND_SUPPORT */
  };
  
  #endif /* PPP_SUPPORT && CHAP_SUPPORT */
  