chap.c

lwip-1.4.0

    len = sizeof(rhostname) - 1;
  }
  BCOPY(inp, rhostname, len);
  rhostname[len] = '\000';

  CHAPDEBUG(LOG_INFO, ("ChapReceiveChallenge: received name field '%s'\n",
             rhostname));

  /* Microsoft doesn't send their name back in the PPP packet */
  if (ppp_settings.remote_name[0] != 0 && (ppp_settings.explicit_remote || rhostname[0] == 0)) {
    strncpy(rhostname, ppp_settings.remote_name, sizeof(rhostname));
    rhostname[sizeof(rhostname) - 1] = 0;
    CHAPDEBUG(LOG_INFO, ("ChapReceiveChallenge: using '%s' as remote name\n",
               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 */
    CHAPDEBUG(LOG_WARNING, ("No CHAP secret found for authenticating us to %s\n",
               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, secret_len);
    MD5Update(&mdContext, rchallenge, rchallenge_len);
    MD5Final(hash, &mdContext);
    BCOPY(hash, cstate->response, MD5_SIGNATURE_SIZE);
    cstate->resp_length = MD5_SIGNATURE_SIZE;
    break;
  
#if MSCHAP_SUPPORT
  case CHAP_MICROSOFT:
    ChapMS(cstate, rchallenge, rchallenge_len, secret, secret_len);
    break;
#endif

  default:
    CHAPDEBUG(LOG_INFO, ("unknown digest type %d\n", cstate->resp_type));
    return;
  }

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


/*
 * ChapReceiveResponse - Receive and process response.
 */
static void
ChapReceiveResponse(chap_state *cstate, u_char *inp, int id, int len)
{
  u_char *remmd, remmd_len;
  int secret_len, old_state;
  int code;
  char rhostname[256];
  MD5_CTX mdContext;
  char secret[MAXSECRETLEN];
  u_char hash[MD5_SIGNATURE_SIZE];

  CHAPDEBUG(LOG_INFO, ("ChapReceiveResponse: Rcvd id %d.\n", id));
  
  if (cstate->serverstate == CHAPSS_CLOSED ||
      cstate->serverstate == CHAPSS_PENDING) {
    CHAPDEBUG(LOG_INFO, ("ChapReceiveResponse: in state %d\n",
    cstate->serverstate));
    return;
  }

  if (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) {
    ChapSendStatus(cstate, CHAP_SUCCESS);
    return;
  }
  if (cstate->serverstate == CHAPSS_BADAUTH) {
    ChapSendStatus(cstate, CHAP_FAILURE);
    return;
  }
  
  if (len < 2) {
    CHAPDEBUG(LOG_INFO, ("ChapReceiveResponse: rcvd short packet.\n"));
    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) {
    CHAPDEBUG(LOG_INFO, ("ChapReceiveResponse: rcvd short packet.\n"));
    return;
  }

  UNTIMEOUT(ChapChallengeTimeout, cstate);
  
  if (len >= (int)sizeof(rhostname)) {
    len = sizeof(rhostname) - 1;
  }
  BCOPY(inp, rhostname, len);
  rhostname[len] = '\000';

  CHAPDEBUG(LOG_INFO, ("ChapReceiveResponse: received name field: %s\n",
             rhostname));

  /*
  * Get secret for authenticating them with us,
  * do the hash ourselves, and compare the result.
  */
  code = CHAP_FAILURE;
  if (!get_secret(cstate->unit, rhostname, cstate->chal_name,
                  secret, &secret_len, 1)) {
    CHAPDEBUG(LOG_WARNING, ("No CHAP secret found for authenticating %s\n",
               rhostname));
  } 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;
      
      default:
        CHAPDEBUG(LOG_INFO, ("unknown digest type %d\n", 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);
    }
  } else {
    CHAPDEBUG(LOG_ERR, ("CHAP peer authentication failed\n"));
    cstate->serverstate = CHAPSS_BADAUTH;
    auth_peer_fail(cstate->unit, PPP_CHAP);
  }
}

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

  CHAPDEBUG(LOG_INFO, ("ChapReceiveSuccess: Rcvd id %d.\n", id));

  if (cstate->clientstate == CHAPCS_OPEN) {
    /* presumably an answer to a duplicate response */
    return;
  }

  if (cstate->clientstate != CHAPCS_RESPONSE) {
    /* don't know what this is */
    CHAPDEBUG(LOG_INFO, ("ChapReceiveSuccess: in state %d\n",
               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.
 */
static void
ChapReceiveFailure(chap_state *cstate, u_char *inp, u_char id, int len)
{
  LWIP_UNUSED_ARG(id);
  LWIP_UNUSED_ARG(inp);

  CHAPDEBUG(LOG_INFO, ("ChapReceiveFailure: Rcvd id %d.\n", id));

  if (cstate->clientstate != CHAPCS_RESPONSE) {
    /* don't know what this is */
    CHAPDEBUG(LOG_INFO, ("ChapReceiveFailure: in state %d\n",
               cstate->clientstate));
    return;
  }

  UNTIMEOUT(ChapResponseTimeout, cstate);

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

  CHAPDEBUG(LOG_ERR, ("CHAP authentication failed\n"));
  auth_withpeer_fail(cstate->unit, PPP_CHAP); /* lwip: just sets the PPP error code on this unit to PPPERR_AUTHFAIL */
}


/*
 * ChapSendChallenge - Send an Authenticate challenge.
 */
static void
ChapSendChallenge(chap_state *cstate)
{
  u_char *outp;
  int chal_len, name_len;
  int outlen;
  
  chal_len = cstate->chal_len;
  name_len = (int)strlen(cstate->chal_name);
  outlen = CHAP_HEADERLEN + sizeof (u_char) + chal_len + name_len;
  outp = outpacket_buf[cstate->unit];

  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 */
  
  pppWrite(cstate->unit, outpacket_buf[cstate->unit], outlen + PPP_HDRLEN);

  CHAPDEBUG(LOG_INFO, ("ChapSendChallenge: Sent id %d.\n", cstate->chal_id));
  
  TIMEOUT(ChapChallengeTimeout, cstate, cstate->timeouttime);
  ++cstate->chal_transmits;
}


/*
 * ChapSendStatus - Send a status response (ack or nak).
 */
static void
ChapSendStatus(chap_state *cstate, int code)
{
  u_char *outp;
  int outlen, msglen;
  char msg[256]; /* @todo: this can be a char*, no strcpy needed */

  if (code == CHAP_SUCCESS) {
    strcpy(msg, "Welcome!");
  } else {
    strcpy(msg, "I don't like you.  Go 'way.");
  }
  msglen = (int)strlen(msg);

  outlen = CHAP_HEADERLEN + msglen;
  outp = outpacket_buf[cstate->unit];

  MAKEHEADER(outp, PPP_CHAP);    /* paste in a header */
  
  PUTCHAR(code, outp);
  PUTCHAR(cstate->chal_id, outp);
  PUTSHORT(outlen, outp);
  BCOPY(msg, outp, msglen);
  pppWrite(cstate->unit, outpacket_buf[cstate->unit], outlen + PPP_HDRLEN);

  CHAPDEBUG(LOG_INFO, ("ChapSendStatus: Sent code %d, id %d.\n", code,
             cstate->chal_id));
}

/*
 * 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(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)
        ((((magic() >> 16) *
              (MAX_CHALLENGE_LENGTH - MIN_CHALLENGE_LENGTH)) >> 16)
           + MIN_CHALLENGE_LENGTH);
  LWIP_ASSERT("chal_len <= 0xff", chal_len <= 0xffff);
  cstate->chal_len = (u_char)chal_len;
  cstate->chal_id = ++cstate->id;
  cstate->chal_transmits = 0;

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

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

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

  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 */
  pppWrite(cstate->unit, outpacket_buf[cstate->unit], outlen + PPP_HDRLEN);

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

#if PPP_ADDITIONAL_CALLBACKS
static char *ChapCodenames[] = {
  "Challenge", "Response", "Success", "Failure"
};
/*
 * ChapPrintPkt - print the contents of a CHAP packet.
 */
static int
ChapPrintPkt( u_char *p, int plen, void (*printer) (void *, 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 = %.*Z", nlen, p);
      break;
    case CHAP_FAILURE:
    case CHAP_SUCCESS:
      printer(arg, " %.*Z", len, p);
      break;
    default:
      for (clen = len; clen > 0; --clen) {
        GETCHAR(x, p);
        printer(arg, " %.2x", x);
      }
  }

  return len + CHAP_HEADERLEN;
}
#endif /* PPP_ADDITIONAL_CALLBACKS */

#endif /* CHAP_SUPPORT */

#endif /* PPP_SUPPORT */