asn1.cpp

/*_############################################################################
  _## 
  _##  asn1.cpp  
  _##
  _##  SNMP++ v3.3
  _##  -----------------------------------------------
  _##  Copyright (c) 2001-2013 Jochen Katz, Frank Fock
  _##
  _##  This software is based on SNMP++2.6 from Hewlett Packard:
  _##  
  _##    Copyright (c) 1996
  _##    Hewlett-Packard Company
  _##  
  _##  ATTENTION: USE OF THIS SOFTWARE IS SUBJECT TO THE FOLLOWING TERMS.
  _##  Permission to use, copy, modify, distribute and/or sell this software 
  _##  and/or its documentation is hereby granted without fee. User agrees 
  _##  to display the above copyright notice and this license notice in all 
  _##  copies of the software and any documentation of the software. User 
  _##  agrees to assume all liability for the use of the software; 
  _##  Hewlett-Packard and Jochen Katz make no representations about the 
  _##  suitability of this software for any purpose. It is provided 
  _##  "AS-IS" without warranty of any kind, either express or implied. User 
  _##  hereby grants a royalty-free license to any and all derivatives based
  _##  upon this software code base. 
  _##  
  _##########################################################################*/

/*===================================================================
  Copyright (c) 1999
  Hewlett-Packard Company

  ATTENTION: USE OF THIS SOFTWARE IS SUBJECT TO THE FOLLOWING TERMS.
  Permission to use, copy, modify, distribute and/or sell this software
  and/or its documentation is hereby granted without fee. User agrees
  to display the above copyright notice and this license notice in all
  copies of the software and any documentation of the software. User
  agrees to assume all liability for the use of the software; Hewlett-Packard
  makes no representations about the suitability of this software for any
  purpose. It is provided "AS-IS" without warranty of any kind,either express
  or implied. User hereby grants a royalty-free license to any and all
  derivatives based upon this software code base.

  A S N 1. C P P

  ASN encoder / decoder implementation

  DESIGN + AUTHOR:  Peter E. Mellquist
=====================================================================*/
char asn1_cpp_version[]="#(@) SNMP++ $Id$";

#include <libsnmp.h>

#include "snmp_pp/config_snmp_pp.h"
#include "snmp_pp/asn1.h"
#include "snmp_pp/v3.h"
#include "snmp_pp/snmperrs.h"
#include "snmp_pp/log.h"

namespace Snmp_pp {

static const char *loggerModuleName = "snmp++.asn1";

/*
 * asn_parse_int - pulls a long out of an ASN int type.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the end of this object.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_parse_int(unsigned char *data,
			     int *datalength,
			     unsigned char *type,
			     long *intp)
{
  /*
   * ASN.1 integer ::= 0x02 asnlength byte {byte}*
   *       timestamp   0x43 asnlength byte {byte}*
   */
  unsigned char *bufp = data;
  unsigned long	 asn_length;
  long value = 0;

  *type = *bufp++;
  if ((*type != 0x02) && (*type != 0x43) &&
      (*type != 0x41)) {
    ASNERROR("Wrong Type. Not an integer");
    return NULL;
  }
  bufp = asn_parse_length(bufp, &asn_length);
  if (bufp == NULL) {
    ASNERROR("bad length");
    return NULL;
  }
  if ((asn_length + (bufp - data)) > (unsigned long)(*datalength)) {
    ASNERROR("overflow of message (int)");
    return NULL;
  }
  if (asn_length > sizeof(*intp)) {
    ASNERROR("I don't support such large integers");
    return NULL;
  }
  *datalength -= (int)asn_length + SAFE_INT_CAST(bufp - data);
  if (*bufp & 0x80)
    value = -1; /* integer is negative */
  while(asn_length--)
    value = (value << 8) | *bufp++;
  *intp = value;
  return bufp;
}


/*
 * asn_parse_unsigned_int - pulls an unsigned long out of an ASN int type.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the end of this object.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_parse_unsigned_int(unsigned char *data,	
                                      int *datalength,
                                      unsigned char *type,
                                      unsigned long *intp)
{
  /*
   * ASN.1 integer ::= 0x02 asnlength byte {byte}*
   *                   0x43 asnlength byte {byte}*
   */
  unsigned char *bufp = data;
  unsigned long	asn_length;
  unsigned long value = 0;

  // get the type
  *type = *bufp++;
  if ((*type != 0x02) && (*type != 0x43) &&
      (*type != 0x41) && (*type != 0x42) &&
      (*type != 0x47)) {
    ASNERROR("Wrong Type. Not an unsigned integer");
    return NULL;
  }

  // pick up the len
  bufp = asn_parse_length(bufp, &asn_length);
  if (bufp == NULL) {
    ASNERROR("bad length");
    return NULL;
  }

  // check the len for message overflow
  if ((asn_length + (bufp - data)) > (unsigned long)(*datalength)) {
    ASNERROR("overflow of message (uint)");
    return NULL;
  }

  // check for legal uint size
  if ((asn_length > 5) || ((asn_length > 4) && (*bufp != 0x00))) {
    ASNERROR("I don't support such large integers");
    return NULL;
  }

  // check for leading  0 octet
  if (*bufp == 0x00) {
    bufp++;
    asn_length--;
  }

  // fix the returned data length value
  *datalength -= (int)asn_length + SAFE_INT_CAST(bufp - data);

  // calculate the value
  for (long i=0;i<(long)asn_length;i++)
    value = (value << 8) + (unsigned long) *bufp++;

  *intp = value;  // assign return value

  return bufp;   // return the bumped pointer
}


/*
 * asn_build_int - builds an ASN object containing an integer.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the end of this object.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_build_int(unsigned char *data, int *datalength,
                             const unsigned char type,
                             const long *intp)
{
  /*
   * ASN.1 integer ::= 0x02 asnlength byte {byte}*
   */
  long integer = *intp;
  unsigned long mask;
  int intsize = sizeof(long);

  /* Truncate "unnecessary" bytes off of the most significant end of this
   * 2's complement integer.  There should be no sequence of 9
   * consecutive 1's or 0's at the most significant end of the
   * integer.
   */
  mask = 0x1FFul << ((8 * (sizeof(long) - 1)) - 1);
  /* mask is 0xFF800000 on a big-endian machine */
  while((((integer & mask) == 0) || ((integer & mask) == mask))
	&& intsize > 1) {
    intsize--;
    integer <<= 8;
  }
  data = asn_build_header(data, datalength, type, intsize);
  if (data == NULL)          return NULL;
  if (*datalength < intsize) return NULL;
  *datalength -= intsize;
  mask = 0xFFul << (8 * (sizeof(long) - 1));
  /* mask is 0xFF000000 on a big-endian machine */
  while(intsize--) {
    *data++ = (unsigned char)((integer & mask) >> (8 * (sizeof(long) - 1)));
    integer <<= 8;
  }
  return data;
}


/*
 * asn_build_unsigned_int - builds an ASN object containing an integer.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the end of this object.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_build_unsigned_int(unsigned char *data, // modified data
                                      int *datalength,     // returned buffer length
                                      unsigned char type,  // SMI type
                                      unsigned long *intp) // Uint to encode
{
  /*
   * ASN.1 integer ::= 0x02 asnlength byte {byte}*
   */
  unsigned long u_integer = *intp;
  long u_integer_len;
  long x;

  // figure out the len
  if (((u_integer >> 24) & 0xFF) != 0)
    u_integer_len = 4;
  else if (((u_integer >> 16) & 0xFF) !=0)
    u_integer_len = 3;
  else if (((u_integer >> 8) & 0xFF) !=0)
    u_integer_len = 2;
  else
    u_integer_len = 1;

  // check for 5 byte len where first byte will be a null
  if (((u_integer >> (8 * (u_integer_len -1))) & 0x080) !=0)	{
    u_integer_len++;
  }

  // build up the header
  data = asn_build_header(data, datalength, type, u_integer_len);
  if (data == NULL)                return NULL;
  if (*datalength < u_integer_len) return NULL;

  // special case, add a null byte for len of 5
  if (u_integer_len == 5) {
    *data++ = 0;
    for (x=1;x<u_integer_len;x++)
      *data++= (unsigned char) (u_integer >> (8 * ((u_integer_len-1)-x)& 0xFF));
  }
  else
  {
    for (x=0;x<u_integer_len;x++)
      *data++= (unsigned char) (u_integer >> (8 * ((u_integer_len-1)-x)& 0xFF));
  }
  *datalength -= u_integer_len;
  return data;
}


/*
 * asn_parse_string - pulls an octet string out of an ASN octet string type.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the beginning of the next object.
 *
 *  "string" is filled with the octet string.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_parse_string(unsigned char	*data,
                                int *datalength,
                                unsigned char *type,
                                unsigned char *str,
                                int *strlength)
{
  /*
   * ASN.1 octet string ::= primstring | cmpdstring
   * primstring ::= 0x04 asnlength byte {byte}*
   * cmpdstring ::= 0x24 asnlength string {string}*
   * ipaddress  ::= 0x40 4 byte byte byte byte
   */
  unsigned char *bufp = data;
  unsigned long	 asn_length;

  *type = *bufp++;
  if ((*type != 0x04) && (*type != 0x24) &&
      (*type != 0x40) && (*type != 0x44) &&
      (*type != 0x45)) {
    ASNERROR("asn parse string: Wrong Type. Not a string");
    return NULL;
  }
  bufp = asn_parse_length(bufp, &asn_length);
  if (bufp == NULL)
    return NULL;
  if ((asn_length + (bufp - data)) > (unsigned long)(*datalength)) {
    ASNERROR("asn parse string: overflow of message");
    return NULL;
  }
  if ((int)asn_length > *strlength) {
    ASNERROR("asn parse string: String to parse is longer than buffer, aborting parsing.");
    return NULL;
  }

  memcpy(str, bufp, asn_length);
  *strlength = (int)asn_length;
  *datalength -= (int)asn_length + SAFE_INT_CAST(bufp - data);
  return bufp + asn_length;
}


/*
 * asn_build_string - Builds an ASN octet string object containing the input string.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the beginning of the next object.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_build_string(unsigned char *data,
                                int *datalength,
                                const unsigned char type,
                                const unsigned char *string,
                                const int strlength)
{
  /*
   * ASN.1 octet string ::= primstring | cmpdstring
   * primstring ::= 0x04 asnlength byte {byte}*
   * cmpdstring ::= 0x24 asnlength string {string}*
   * This code will never send a compound string.
   */
  data = asn_build_header(data, datalength, type, strlength);
  if (data == NULL)            return NULL;
  if (*datalength < strlength) return NULL;

  memcpy(data, string, strlength);
  *datalength -= strlength;
  return data + strlength;
}


/*
 * asn_parse_header - interprets the ID and length of the current object.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   in this object following the id and length.
 *
 *  Returns a pointer to the first byte of the contents of this object.
 *  Returns NULL on any error.
 */
unsigned char *asn_parse_header(unsigned char *data,
				int *datalength,
                                unsigned char *type)
{
  unsigned char *bufp = data;
  unsigned long asn_length;

  /* this only works on data types < 30, i.e. no extension octets */
  if (IS_EXTENSION_ID(*bufp)) {
    ASNERROR("can't process ID >= 30");
    return NULL;
  }
  *type = *bufp;
  bufp = asn_parse_length(bufp + 1, &asn_length);
  if (bufp == NULL)
    return NULL;
  int header_len = SAFE_INT_CAST(bufp - data);
  if ((unsigned long)(header_len + asn_length) > (unsigned long)*datalength) {
    ASNERROR("asn length too long");
    return NULL;
  }
  *datalength = (int)asn_length;
  return bufp;
}

/*
 * asn_build_header - builds an ASN header for an object with the ID and
 * length specified.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   in this object following the id and length.
 *
 *  This only works on data types < 30, i.e. no extension octets.
 *  The maximum length is 0xFFFF;
 *
 *  Returns a pointer to the first byte of the contents of this object.
 *  Returns NULL on any error.
 */
unsigned char *asn_build_header(unsigned char *data,
                                int *datalength,
                                unsigned char type,
                                int length)
{
  if (*datalength < 1)
    return NULL;
  *data++ = type;
  (*datalength)--;
  return asn_build_length(data, datalength, length);
}

/*
 * asn_build_sequence - builds an ASN header for a sequence with the ID and
 * length specified.
 *
 *  This only works on data types < 30, i.e. no extension octets.
 *
 *  Returns a pointer to the first byte of the contents of this object.
 *  Returns NULL on any error.
 */
unsigned char *asn_build_sequence(unsigned char *data,
                                  int *datalength,
                                  unsigned char type,
                                  int length)
{
  if (*datalength < 2) /* need at least two octets for a sequence */
  {
    ASNERROR("build_sequence");
    return NULL;
  }
  *data++ = type;
  (*datalength)--;

  unsigned char *data_with_length = asn_build_length(data, datalength, length);
  if (data_with_length == NULL)
  {
    (*datalength)++; /* correct datalength to emulate old behavior of build_sequence */
    return NULL;
  }
     
  return data_with_length;
}

/*
 * asn_parse_length - interprets the length of the current object.
 *  On exit, length contains the value of this length field.
 *
 *  Returns a pointer to the first byte after this length
 *  field (aka: the start of the data field).
 *  Returns NULL on any error.
 */
unsigned char * asn_parse_length(unsigned char *data,
                                 unsigned long *length)
{
  unsigned char lengthbyte = *data;
  *length = 0;
  if (lengthbyte & ASN_LONG_LEN) {
    lengthbyte &= ~ASN_LONG_LEN;	/* turn MSb off */
    if (lengthbyte == 0) {
      ASNERROR("We don't support indefinite lengths");
      return NULL;
    }
    if (lengthbyte > sizeof(int)) {
      ASNERROR("we can't support data lengths that long");
      return NULL;
    }
    for (int i=0 ; i < lengthbyte ; i++)
    {
      *length = (*length << 8) + *(data + 1 + i);
    }
    // check for length greater than 2^31
    if (*length > 0x80000000ul) {
      ASNERROR("SNMP does not support data lengths > 2^31");
      return NULL;
    }
    return data + lengthbyte + 1;
  } else { /* short asnlength */
    *length = (long)lengthbyte;
    return data + 1;
  }
}

unsigned char *asn_build_length(unsigned char *data,
                                int *datalength,
                                int length)
{
  unsigned char *start_data = data;

  /* no indefinite lengths sent */
  if (length < 0x80) {
    if (*datalength < 1) {
      ASNERROR("build_length");
      return NULL;
    }	
    *data++ = (unsigned char)length;
  }
  else if (length <= 0xFF) {
    if (*datalength < 2) {
      ASNERROR("build_length");
      return NULL;
    }	
    *data++ = (unsigned char)(0x01 | ASN_LONG_LEN);
    *data++ = (unsigned char)length;
  }
  else if (length <= 0xFFFF) { /* 0xFF < length <= 0xFFFF */
    if (*datalength < 3) {
      ASNERROR("build_length");
      return NULL;
    }	
    *data++ = (unsigned char)(0x02 | ASN_LONG_LEN);
    *data++ = (unsigned char)((length >> 8) & 0xFF);
    *data++ = (unsigned char)(length & 0xFF);
  }
  else if (length <= 0xFFFFFF) { /* 0xFF < length <= 0xFFFF */
    if (*datalength < 4) {
      ASNERROR("build_length");
      return NULL;
    }	
    *data++ = (unsigned char)(0x03 | ASN_LONG_LEN);
    *data++ = (unsigned char)((length >> 16) & 0xFF);
    *data++ = (unsigned char)((length >> 8) & 0xFF);
    *data++ = (unsigned char)(length & 0xFF);
  }
  else {
    if (*datalength < 5) {
      ASNERROR("build_length");
      return NULL;
    }	
    *data++ = (unsigned char)(0x04 | ASN_LONG_LEN);
    *data++ = (unsigned char)((length >> 24) & 0xFF);
    *data++ = (unsigned char)((length >> 16) & 0xFF);
    *data++ = (unsigned char)((length >> 8) & 0xFF);
    *data++ = (unsigned char)(length & 0xFF);
  }
  *datalength -= SAFE_INT_CAST(data - start_data);
  return data;
}

/*
 * asn_parse_objid - pulls an object indentifier out of an ASN object identifier type.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the beginning of the next object.
 *
 *  "objid" is filled with the object identifier.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_parse_objid(unsigned char *data,
                               int *datalength,
                               unsigned char *type,
                               oid *objid,
                               int *objidlength)
{
  /*
   * ASN.1 objid ::= 0x06 asnlength subidentifier {subidentifier}*
   * subidentifier ::= {leadingbyte}* lastbyte
   * leadingbyte ::= 1 7bitvalue
   * lastbyte ::= 0 7bitvalue
   */
  unsigned char *bufp = data;
  oid *oidp = objid + 1;
  unsigned long subidentifier;
  long length;
  unsigned long asn_length;

  *type = *bufp++;
  if (*type != 0x06) {
    ASNERROR("Wrong Type. Not an oid");
    return NULL;
  }
  bufp = asn_parse_length(bufp, &asn_length);
  if (bufp == NULL)
    return NULL;
  if ((asn_length + (bufp - data)) > (unsigned long)(*datalength)) {
    ASNERROR("overflow of message (objid)");
    return NULL;
  }
  *datalength -= (int)asn_length + SAFE_INT_CAST(bufp - data);

  /* Handle invalid object identifier encodings of the form 06 00 robustly */
  if (asn_length == 0)
    objid[0] = objid[1] = 0;

  length = asn_length;
  (*objidlength)--;	/* account for expansion of first byte */
  while (length > 0 && (*objidlength)-- > 0) {
    subidentifier = 0;
    do {	/* shift and add in low order 7 bits */
      subidentifier = (subidentifier << 7) + (*(unsigned char *)bufp & ~ASN_BIT8);
      length--;
    } while (*(unsigned char *)bufp++ & ASN_BIT8); /* last byte has high bit clear */
    if (subidentifier > (unsigned long)MAX_SUBID) {
      ASNERROR("subidentifier too long");
      return NULL;
    }
    *oidp++ = (oid)subidentifier;
  }

  /*
   * The first two subidentifiers are encoded into the first component
   * with the value (X * 40) + Y, where:
   * X is the value of the first subidentifier.
   * Y is the value of the second subidentifier.
   */
  subidentifier = (unsigned long)objid[1];
  if (subidentifier == 0x2B) {
    objid[0] = 1;
    objid[1] = 3;
  } else if (subidentifier < 40) {
      objid[0] = 0;
      objid[1] = (oid)subidentifier;
  } else if (subidentifier < 80) {
      objid[0] = 1;
      objid[1] = (oid)(subidentifier - 40);
  }
  else {
    objid[0] = 2;
    objid[1] = (oid)(subidentifier - 80);
  }
  *objidlength = (int)(oidp - objid);
  return bufp;
}

/*
 * asn_build_objid - Builds an ASN object identifier object containing the
 * input string.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the beginning of the next object.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_build_objid(unsigned char *data,
                                int *datalength,
                                unsigned char type,
                                oid *objid,
                                int objidlength)
{
  /*
   * ASN.1 objid ::= 0x06 asnlength subidentifier {subidentifier}*
   * subidentifier ::= {leadingbyte}* lastbyte
   * leadingbyte ::= 1 7bitvalue
   * lastbyte ::= 0 7bitvalue
   */
  // F.Fock correct buffer size must be 5*8bit*MAX_OID_LEN
  unsigned char buf[MAX_OID_LEN*5];
  unsigned char *bp = buf;
  oid *op = objid;
  int    asnlength;

  if (objidlength > MAX_OID_LEN) {
      ASNERROR("Too many sub-identifiers.");
      objidlength = MAX_OID_LEN;
  }
  if (objidlength < 2) {
    *bp++ = 0;
    objidlength = 0;
  } else {
    asn_build_subid(op[1] + (op[0] * 40), bp);
    objidlength -= 2;
    op += 2;
  }

  while(objidlength-- > 0) {
    asn_build_subid(*op++, bp);
  }
  asnlength = SAFE_INT_CAST(bp - buf);
  data = asn_build_header(data, datalength, type, asnlength);
  if (data == NULL)            return NULL;
  if (*datalength < asnlength) return NULL;

  memcpy((char *)data, (char *)buf,  asnlength);
  *datalength -= asnlength;
  return data + asnlength;
}

/**
 * Add the given sub-identifier to the OID byte buffer and forward its pointer
 * accordingly for appending the next one.
 * @param subid
 *    the sub-identifier (32-bit unsigned) to add.
 * @param bp
 *    the buffer pointer. On return, the pointer will be increased at least
 *    by one (character) and at most by five.
 */
void asn_build_subid(unsigned long subid, unsigned char*& bp) {
  unsigned long mask, testmask;
  int bits, testbits;
  if (subid < 127) { /* off by one? */
      *bp++ = (unsigned char)subid;
  } else {
      mask = 0x7F; /* handle subid == 0 case */
      bits = 0;
      /* testmask *MUST* !!!! be of an unsigned type */
      for(testmask = 0x7F, testbits = 0; testmask != 0;
	  testmask <<= 7, testbits += 7) {
	if (subid & testmask) {	/* if any bits set */
	  mask = testmask;
	  bits = testbits;
	}
      }
      /* mask can't be zero here */
      for(;mask != 0x7F; mask >>= 7, bits -= 7) {
	/* fix a mask that got truncated above */
	if (mask == 0x1E00000)
	  mask = 0xFE00000;
	*bp++ = (unsigned char)(((subid & mask) >> bits) | ASN_BIT8);
      }
      *bp++ = (unsigned char)(subid & mask);
  }    
}

/*
 * asn_parse_null - Interprets an ASN null type.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the beginning of the next object.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_parse_null(unsigned char	*data,
                              int *datalength,
                              unsigned char *type)
{
  /*
   * ASN.1 null ::= 0x05 0x00
   */
  unsigned char   *bufp = data;
  unsigned long	    asn_length;

  *type = *bufp++;
  if (*type != 0x05) {
    ASNERROR("Wrong Type. Not a null");
    return NULL;
  }
  bufp = asn_parse_length(bufp, &asn_length);
  if (bufp == NULL)
    return NULL;
  if (asn_length != 0) {
    ASNERROR("Malformed NULL");
    return NULL;
  }
  *datalength -= SAFE_INT_CAST(bufp - data);
  return bufp + asn_length;
}


/*
 * asn_build_null - Builds an ASN null object.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the beginning of the next object.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_build_null(unsigned char *data,
                               int *datalength,
                               unsigned char type)
{
  /*
   * ASN.1 null ::= 0x05 0x00
   */
  return asn_build_header(data, datalength, type, 0);
}

/*
 * asn_parse_bitstring - pulls a bitstring out of an ASN bitstring type.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the beginning of the next object.
 *
 *  "string" is filled with the bit string.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_parse_bitstring(unsigned char *data,
                                    int *datalength,
                                    unsigned char *type,
                                    unsigned char *string,
                                    int *strlength)
{
  /*
   * bitstring ::= 0x03 asnlength unused {byte}*
   */
  unsigned char *bufp = data;
  unsigned long	    asn_length;

  *type = *bufp++;
  if (*type != 0x03) {
    ASNERROR("Wrong Type. Not a bitstring");
    return NULL;
  }
  bufp = asn_parse_length(bufp, &asn_length);
  if (bufp == NULL)
    return NULL;
  if ((asn_length + (bufp - data)) > (unsigned long)(*datalength)) {
    ASNERROR("overflow of message (bitstring)");
    return NULL;
  }
  if ((int) asn_length > *strlength) {
    ASNERROR("I don't support such long bitstrings");
    return NULL;
  }
  if (asn_length < 1) {
    ASNERROR("Invalid bitstring");
    return NULL;
  }
  if (*bufp > 7) {
    ASNERROR("Invalid bitstring");
    return NULL;
  }

  memcpy((char *)string,(char *)bufp,  (int)asn_length);
  *strlength = (int)asn_length;
  *datalength -= (int)asn_length + SAFE_INT_CAST(bufp - data);
  return bufp + asn_length;
}


/*
 * asn_build_bitstring - Builds an ASN bit string object containing the
 * input string.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the beginning of the next object.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_build_bitstring(unsigned char *data,
                                    int *datalength,
                                    unsigned char type,	
                                    unsigned char *string,
                                    int strlength)
{
  /*
   * ASN.1 bit string ::= 0x03 asnlength unused {byte}*
   */
  if (strlength < 1 || *string > 7) {
    ASNERROR("Building invalid bitstring");
    return NULL;
  }
  data = asn_build_header(data, datalength, type, strlength);
  if (data == NULL)            return NULL;
  if (*datalength < strlength) return NULL;

  memcpy((char *)data,(char *)string, strlength);
  *datalength -= strlength;
  return data + strlength;
}


/*
 * asn_parse_unsigned_int64 - pulls a 64 bit unsigned long out of an ASN int
 * type.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the end of this object.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_parse_unsigned_int64(unsigned char *data,
                                        int *datalength,
                                        unsigned char *type,
                                        struct counter64 *cp)
{
  /*
   * ASN.1 integer ::= 0x02 asnlength byte {byte}*
   */
  unsigned char *bufp = data;
  unsigned long	    asn_length;
  unsigned long low = 0, high = 0;

  *type = *bufp++;
  if ((*type != 0x02) && (*type != 0x46)) {
    ASNERROR("Wrong Type. Not an integer 64");
    return NULL;
  }
  bufp = asn_parse_length(bufp, &asn_length);
  if (bufp == NULL) {
    ASNERROR("bad length");
    return NULL;
  }
  if ((asn_length + (bufp - data)) > (unsigned long)(*datalength)) {
    ASNERROR("overflow of message (uint64)");
    return NULL;
  }
  if (((int)asn_length > 9) ||
      (((int)asn_length == 9) && *bufp != 0x00)) {
    ASNERROR("I don't support such large integers");
    return NULL;
  }
  *datalength -= (int)asn_length + SAFE_INT_CAST(bufp - data);
  if (*bufp & 0x80) {
    low = (unsigned long) -1; // integer is negative
    high = (unsigned long) -1;
  }
  while(asn_length--) {
    high = (high << 8) | ((low & 0xFF000000) >> 24);
    low = ((low << 8) | *bufp++) & 0xFFFFFFFF;
  }
  cp->low = low;
  cp->high = high;

  return bufp;
}


/*
 * asn_build_unsigned_int64 - builds an ASN object containing a 64 bit integer.
 *  On entry, datalength is input as the number of valid bytes following
 *   "data".  On exit, it is returned as the number of valid bytes
 *   following the end of this object.
 *
 *  Returns a pointer to the first byte past the end
 *   of this object (i.e. the start of the next object).
 *  Returns NULL on any error.
 */
unsigned char *asn_build_unsigned_int64(unsigned char *data,
                                        int *datalength,
                                        unsigned char type,
                                        struct counter64 *cp)
{
  /*
   * ASN.1 integer ::= 0x02 asnlength byte {byte}*
   */
  unsigned long low = cp->low;
  unsigned long high = cp->high;
  unsigned long mask = 0xFF000000ul;
  int add_null_byte = 0;
  int intsize = 8;

  if (((high & mask) >> 24) & 0x80) {
    /* if MSB is set */
    add_null_byte = 1;
    intsize++;
  }
  else {
    /*
     * Truncate "unnecessary" bytes off of the most significant end of this 2's
     * complement integer.
     * There should be no sequence of 9 consecutive 1's or 0's at the most
     * significant end of the integer.
     */
    unsigned long mask2 = 0xFF800000ul;
    while ((((high & mask2) == 0) || ((high & mask2) == mask2)) &&
	   (intsize > 1)) {
      intsize--;
      high = (high << 8) | ((low & mask) >> 24);
      low <<= 8;
    }
  }
  data = asn_build_header(data, datalength, type, intsize);
  if (data == NULL)          return NULL;
  if (*datalength < intsize) return NULL;
  *datalength -= intsize;
  if (add_null_byte == 1) {
    *data++ = 0;
    intsize--;
  }
  while(intsize--) {
    *data++ = (unsigned char)((high & mask) >> 24);
    high = (high << 8) | ((low & mask) >> 24);
    low <<= 8;
  }
  return data;
}


// create a pdu
struct snmp_pdu *snmp_pdu_create(int command)
{
  struct snmp_pdu *pdu;

  pdu = (struct snmp_pdu *)malloc(sizeof(struct snmp_pdu));
  if (!pdu) return pdu;
  memset((char *)pdu, 0,sizeof(struct snmp_pdu));
  pdu->command = command;
  pdu->msgid = 0;
  pdu->errstat = 0;
  pdu->errindex = 0;
  pdu->enterprise = NULL;
  pdu->enterprise_length = 0;
  pdu->variables = NULL;
  return pdu;
}

// free content and clear pointers
void clear_pdu(struct snmp_pdu *pdu, bool clear_all)
{
  struct variable_list *vp, *ovp;

  vp = pdu->variables;
  while (vp)
  {
    if (vp->name) free((char *)vp->name);  // free the oid part
    if (vp->val.string) free((char *)vp->val.string);  // free deep data
    ovp = vp;
    vp = vp->next_variable;     // go to the next one
    free((char *)ovp);     // free up vb itself
  }
  pdu->variables = NULL;

  // if enterprise free it up
  if (pdu->enterprise)
    free((char *)pdu->enterprise);
  pdu->enterprise = NULL;

  if (!clear_all) return;

  pdu->command = 0;
  pdu->reqid   = 0;
  pdu->msgid   = 0;
  pdu->maxsize_scopedpdu = 0;
  pdu->errstat = 0;
  pdu->errindex = 0;

  pdu->enterprise_length = 0;
  pdu->trap_type = 0;
  pdu->specific_type = 0;
  pdu->time = 0;
}

// free a pdu
void snmp_free_pdu(struct snmp_pdu *pdu)
{
  clear_pdu(pdu); // clear and free content
  free(pdu);   // free up pdu itself
}


// add a null var to a pdu
void snmp_add_var(struct snmp_pdu *pdu,
		  oid *name,
		  int name_length,
		  SmiVALUE *smival)
{
  struct variable_list *vars;

  // if we don't have a vb list ,create one
  if (pdu->variables == NULL)
    pdu->variables = vars = (struct variable_list *)malloc(sizeof(struct variable_list));
  else
  {
    // we have one, find the end
    vars = pdu->variables;
    while (vars->next_variable) vars = vars->next_variable;

    // create a new one
    vars->next_variable = (struct variable_list *)malloc(sizeof(struct variable_list));
    // bump ptr
    vars = vars->next_variable;
  }

  // add the oid with no data
  vars->next_variable = NULL;

  // hook in the Oid portion
  vars->name = (oid *)malloc(name_length * sizeof(oid));

  memcpy((char *)vars->name,(char *)name, name_length * sizeof(oid));
  vars->name_length = name_length;

  // hook in the SMI value
  switch(smival->syntax)
    {
      // null , do nothing
    case sNMP_SYNTAX_NULL:
    case sNMP_SYNTAX_NOSUCHOBJECT:
    case sNMP_SYNTAX_NOSUCHINSTANCE:
    case sNMP_SYNTAX_ENDOFMIBVIEW:
      {
	vars->type = (unsigned char) smival->syntax;
	vars->val.string = NULL;
	vars->val_len = 0;
      }
      break;

      // octects
    case sNMP_SYNTAX_OCTETS:
    case sNMP_SYNTAX_OPAQUE:
    case sNMP_SYNTAX_IPADDR:
      {
	vars->type = (unsigned char) smival->syntax;
	vars->val.string = (unsigned char *)malloc((unsigned)smival->value.string.len);
	vars->val_len = (int) smival->value.string.len;
	memcpy((unsigned char *) vars->val.string,
		(unsigned char *) smival->value.string.ptr,
		(unsigned) smival->value.string.len);
      }
      break;

      // oid
    case sNMP_SYNTAX_OID:
      {
	vars->type = (unsigned char) smival->syntax;
        vars->val_len = (int) smival->value.oid.len * sizeof(oid);
	vars->val.objid = (oid *)malloc((unsigned)vars->val_len);
	memcpy((unsigned long *)vars->val.objid,
	       (unsigned long *)smival->value.oid.ptr,
	       (unsigned) vars->val_len);
      }
      break;


	
    case sNMP_SYNTAX_TIMETICKS:
    case sNMP_SYNTAX_CNTR32:
    case sNMP_SYNTAX_GAUGE32:
      //    case sNMP_SYNTAX_UINT32:
      {
	long templong;
	vars->type = (unsigned char) smival->syntax;
	vars->val.integer = (long *)malloc(sizeof(long));
	vars->val_len = sizeof(long);
	templong = (long) smival->value.uNumber;
	memcpy((long*) vars->val.integer,
		(long*) &templong,
		sizeof(long));
      }
      break;

    case sNMP_SYNTAX_INT32:
      {
	long templong;
	vars->type = (unsigned char) smival->syntax;
	vars->val.integer = (long *)malloc(sizeof(long));
	vars->val_len = sizeof(long);
	templong = (long) smival->value.sNumber;
	memcpy((long*) vars->val.integer,
		(long*) &templong,
		sizeof(long));
      }
      break;

      // 64 bit counter
    case sNMP_SYNTAX_CNTR64:
      {
	vars->type = (unsigned char) smival->syntax;
	vars->val.counter64 = (struct counter64 *)malloc(sizeof(struct counter64));
	vars->val_len = sizeof(struct counter64);
	memcpy((struct counter64*) vars->val.counter64,
		(SmiLPCNTR64) &(smival->value.hNumber),
		sizeof(SmiCNTR64));
      }
      break;

    } // end switch

}

// build the authentication, works for v1 or v2c
static unsigned char *snmp_auth_build(unsigned char *data,
				      int *length,
				      const long int version,
				      const unsigned char *community,
				      const int community_len,
				      const int messagelen)
{
  // 5 is 3 octets for version and 2 for community header + len
  // This assumes that community will not be longer than 0x7f chars.
  data = asn_build_sequence(data, length, ASN_SEQ_CON,
			    messagelen + community_len + 5);
  if (data == NULL) { 
    ASNERROR("buildheader");
    return NULL;
  }
  data = asn_build_int(data, length, ASN_UNI_PRIM | ASN_INTEGER, &version);
  if (data == NULL) {
    ASNERROR("buildint");
    return NULL;
  }

  data = asn_build_string(data, length, ASN_UNI_PRIM | ASN_OCTET_STR,
			  community, community_len);
  if (data == NULL) {
    ASNERROR("buildstring");
    return NULL;
  }

  return data;
}


// build a variable binding
unsigned char * snmp_build_var_op(unsigned char *data,
				  oid * var_name,
				  int *var_name_len,
				  unsigned char var_val_type,
				  int var_val_len,
				  unsigned char *var_val,
				  int *listlength)
{
  int valueLen;
  Buffer<unsigned char> buffer(MAX_SNMP_PACKET);
  unsigned char *buffer_pos = buffer.get_ptr();
  int bufferLen = MAX_SNMP_PACKET;

  buffer_pos = asn_build_objid(buffer_pos, &bufferLen,
			       ASN_UNI_PRIM | ASN_OBJECT_ID,
			       var_name, *var_name_len);
  if (buffer_pos == NULL) {
    ASNERROR("build_var_op: build_objid failed");
    return NULL;
  }

  // based on the type...
  switch(var_val_type) {
  case ASN_INTEGER:
    if (var_val_len != sizeof(long))
    {
      ASNERROR("build_var_op: Illegal size of integer");
      return NULL;
    }
    buffer_pos = asn_build_int(buffer_pos, &bufferLen,
                               var_val_type, (long *)var_val);
    break;

  case SMI_GAUGE:
  case SMI_COUNTER:
  case SMI_TIMETICKS:
  case SMI_UINTEGER:
    if (var_val_len != sizeof(unsigned long))
    {
      ASNERROR("build_var_op: Illegal size of unsigned integer");
      return NULL;
    }
    buffer_pos = asn_build_unsigned_int(buffer_pos, &bufferLen,
                                        var_val_type, (unsigned long *)var_val);
    break;

  case SMI_COUNTER64:
    if (var_val_len != sizeof(counter64))
    {
      ASNERROR("build_var_op: Illegal size of counter64");
      return NULL;
    }
    buffer_pos = asn_build_unsigned_int64(buffer_pos, &bufferLen,
                                          var_val_type,
                                          (struct counter64 *)var_val);
    break;

  case ASN_OCTET_STR:
  case SMI_IPADDRESS:
  case SMI_OPAQUE:
  case SMI_NSAP:
    buffer_pos = asn_build_string(buffer_pos, &bufferLen, var_val_type,
                                  var_val, var_val_len);
    break;

  case ASN_OBJECT_ID:
    buffer_pos = asn_build_objid(buffer_pos, &bufferLen, var_val_type,
                                 (oid *)var_val, var_val_len / sizeof(oid));
    break;

  case ASN_NULL:
    buffer_pos = asn_build_null(buffer_pos, &bufferLen, var_val_type);
    break;

  case ASN_BIT_STR:
    buffer_pos = asn_build_bitstring(buffer_pos, &bufferLen, var_val_type,
                                     var_val, var_val_len);
    break;

  case SNMP_NOSUCHOBJECT:
  case SNMP_NOSUCHINSTANCE:
  case SNMP_ENDOFMIBVIEW:
    buffer_pos = asn_build_null(buffer_pos, &bufferLen, var_val_type);
    break;

  default:
    ASNERROR("build_var_op: wrong type");
    return NULL;
  }
  if (buffer_pos == NULL) {
    ASNERROR("build_var_op: value build failed");
    return NULL;
  }

  valueLen = SAFE_INT_CAST(buffer_pos - buffer.get_ptr());

  data = asn_build_sequence(data, listlength, ASN_SEQ_CON, valueLen);

  if(data == NULL || *listlength < valueLen)
  {
    ASNERROR("build_var_op");
    data = NULL;
  }
  else
  {
    memcpy(data, buffer.get_ptr(), valueLen);
    data += valueLen;
    (*listlength)-=valueLen;
  }
  return data;
}


unsigned char *build_vb(struct snmp_pdu *pdu,
			unsigned char *buf, int *buf_len)
{
  Buffer<unsigned char> tmp_buf(MAX_SNMP_PACKET);
  unsigned char *cp = tmp_buf.get_ptr();
  struct   variable_list *vp;
  int vb_length;
  int length = MAX_SNMP_PACKET;

  // build varbinds into packet buffer
  for(vp = pdu->variables; vp; vp = vp->next_variable)
  {
    cp = snmp_build_var_op(cp, vp->name, &vp->name_length,
			    vp->type, vp->val_len,
			    (unsigned char *)vp->val.string,
			    &length);
    if (cp == NULL) return 0;
  }
  vb_length = SAFE_INT_CAST(cp - tmp_buf.get_ptr());
  *buf_len -= vb_length;
  if (*buf_len <= 0) return 0;

  // encode the length of encoded varbinds into buf
  cp = asn_build_header(buf, buf_len, ASN_SEQ_CON, vb_length);
  if (cp == NULL) return 0;

  // copy varbinds from packet behind header in buf
  memcpy(cp, tmp_buf.get_ptr(), vb_length);

  return (cp + vb_length);
}

unsigned char *build_data_pdu(struct snmp_pdu *pdu,
			      unsigned char *buf, int *buf_len,
			      unsigned char *vb_buf, int vb_buf_len)
{
  Buffer<unsigned char> tmp_buf(MAX_SNMP_PACKET);
  unsigned char *cp = tmp_buf.get_ptr();
  int totallength;
  int length = MAX_SNMP_PACKET;

  // build data of pdu into tmp_buf
  if (pdu->command != TRP_REQ_MSG)
  {
    // request id
    cp = asn_build_int(cp, &length, ASN_UNI_PRIM | ASN_INTEGER, &pdu->reqid);
    if (cp == NULL) return 0;

    // error status
    cp = asn_build_int(cp, &length, ASN_UNI_PRIM | ASN_INTEGER, &pdu->errstat);
    if (cp == NULL) return 0;

    // error index
    cp = asn_build_int(cp, &length, ASN_UNI_PRIM | ASN_INTEGER, &pdu->errindex);
    if (cp == NULL) return 0;
  }
  else
  { // this is a trap message
    // enterprise
    cp = asn_build_objid(cp, &length, ASN_UNI_PRIM | ASN_OBJECT_ID,
			  (oid *)pdu->enterprise, pdu->enterprise_length);
    if (cp == NULL) return 0;

    // agent-addr ; must be IPADDRESS changed by Frank Fock
    cp = asn_build_string(cp, &length, SMI_IPADDRESS,
			  (unsigned char *)&pdu->agent_addr.sin_addr.s_addr,
			  sizeof(pdu->agent_addr.sin_addr.s_addr));
    if (cp == NULL) return 0;

    long dummy = pdu->trap_type;
    // generic trap
    cp = asn_build_int(cp, &length, ASN_UNI_PRIM | ASN_INTEGER, &dummy);
    if (cp == NULL) return 0;

    dummy = pdu->specific_type;
    // specific trap
    cp = asn_build_int(cp, &length, ASN_UNI_PRIM | ASN_INTEGER, &dummy);
    if (cp == NULL) return 0;

    // timestamp
    cp = asn_build_unsigned_int(cp, &length, SMI_TIMETICKS, &pdu->time);
    if (cp == NULL) return 0;
  }

  if (length < vb_buf_len) return 0;

  // save relative position of varbinds
  int vb_rel_pos = SAFE_INT_CAST(cp - tmp_buf.get_ptr());
  totallength = SAFE_INT_CAST(cp - tmp_buf.get_ptr()) + vb_buf_len;

  // build header for datapdu into buf
  cp = asn_build_header(buf, buf_len,
			(unsigned char)pdu->command, totallength);
  if (cp == NULL) return 0;
  if (*buf_len < totallength) return 0;

  // copy data behind header
  memcpy(cp, tmp_buf.get_ptr(), totallength - vb_buf_len);
  memcpy((char *)cp + vb_rel_pos, (char *)vb_buf, vb_buf_len);
  *buf_len -= totallength;
  return (cp + totallength);
}

// serialize the pdu
int snmp_build(struct snmp_pdu	*pdu,
               unsigned char *packet,          int *out_length,
               const long version,
               const unsigned char* community, const int community_len)
{
  Buffer<unsigned char> buf(MAX_SNMP_PACKET);
  unsigned char  *cp;
  int	     length;
  int	 totallength;

  // encode vbs with header into packet
  length = *out_length;
  cp = build_vb(pdu, packet, &length);
  if (cp == 0) return -1;
  totallength = SAFE_INT_CAST(cp - packet);
  if (totallength >= *out_length) return -1;

  // encode datadpu into buf
  length = MAX_SNMP_PACKET;
  cp = build_data_pdu(pdu, buf.get_ptr(), &length,
		      packet, totallength);
  if (cp == 0) return -1;
  totallength = SAFE_INT_CAST(cp - buf.get_ptr());
  if (totallength >= *out_length) return -1;

  // build SNMP header
  length = *out_length;
  cp = snmp_auth_build(packet, &length, version,
			community, community_len, totallength);
  if (cp == NULL) return -1;
  if ((*out_length - (cp - packet)) < totallength) return -1;

  // copy data
  memcpy(cp, buf.get_ptr(), totallength);
  totallength += SAFE_INT_CAST(cp - packet);
  *out_length = totallength;

  return 0;
}

// parse the authentication header
static unsigned char *snmp_auth_parse(unsigned char *data,
				      int *length,
				      unsigned char *community,
				      int *community_len,
				      long	*version)
{
  unsigned char type;

  // get the type
  data = asn_parse_header(data, length, &type);
  if (data == NULL) {
    ASNERROR("bad header");
    return NULL;
  }

  if (type != ASN_SEQ_CON) {
    ASNERROR("wrong auth header type");
    return NULL;
  }

  // get the version
  data = asn_parse_int(data, length, &type, version);
  if (data == NULL) {
    ASNERROR("bad parse of version");
    return NULL;
  }

  // get the community name
  data = asn_parse_string(data, length, &type, community, community_len);
  if (data == NULL) {
    ASNERROR("bad parse of community");
    return NULL;
  }

  return (unsigned char *)data;
}

unsigned char *
snmp_parse_var_op(unsigned char *data,  // IN - pointer to the start of object
		   oid	    *var_name,	         // OUT - object id of variable
		   int	    *var_name_len,       // IN/OUT - length of variable name
		   unsigned char  *var_val_type, // OUT - type of variable (int or octet string) (one byte)
		   int	    *var_val_len,        // OUT - length of variable
		   unsigned char  **var_val,	 // OUT - pointer to ASN1 encoded value of variable
		   int	    *listlength)         // IN/OUT - number of valid bytes left in var_op_list
{
  unsigned char var_op_type;
  int	var_op_len = *listlength;
  unsigned char *var_op_start = data;

  data = asn_parse_header(data, &var_op_len, &var_op_type);
  if (data == NULL) {
    ASNERROR("Error snmp_parse_var_op: 1");
    return NULL;
  }
  if (var_op_type != ASN_SEQ_CON)
    return NULL;
  data = asn_parse_objid(data, &var_op_len, &var_op_type, var_name, var_name_len);
  if (data == NULL) {
    ASNERROR("Error snmp_parse_var_op: 2");
    return NULL;
  }
  if (var_op_type != (ASN_UNI_PRIM | ASN_OBJECT_ID))
    return NULL;
  *var_val = data;	/* save pointer to this object */
  /* find out what type of object this is */
  data = asn_parse_header(data, &var_op_len, var_val_type);
  if (data == NULL) {
    ASNERROR("Error snmp_parse_var_op: 3");
    return NULL;
  }
  if (((unsigned long)var_op_len + (data - var_op_start)) > (unsigned long)(*listlength)) {
    ASNERROR("Error snmp_parse_var_op: 4");
    return NULL;
  }
  *var_val_len = (int)var_op_len;
  data += var_op_len;
  *listlength -= (int)(data - var_op_start);
  return data;
}


int snmp_parse_vb(struct snmp_pdu *pdu, unsigned char *&data, int &data_len)
{
  unsigned char  *var_val;
  int len;
  struct variable_list *vp = 0;
  oid	    objid[ASN_MAX_NAME_LEN], *op;
  unsigned char type;

  // get the vb list from received data
  data = asn_parse_header(data, &data_len, &type);
  if (data == NULL)
    return SNMP_CLASS_ASN1ERROR;
  if (type != ASN_SEQ_CON)
    return SNMP_CLASS_ASN1ERROR;
  pdu->variables = NULL;
  while(data_len > 0) {
    if (pdu->variables == NULL) {
      pdu->variables = vp = (struct variable_list *)malloc(sizeof(struct variable_list));
    } else {
      vp->next_variable = (struct variable_list *)malloc(sizeof(struct variable_list));
      vp = vp->next_variable;
    }
    vp->next_variable = NULL;
    vp->val.string = NULL;
    vp->name = NULL;
    vp->name_length = ASN_MAX_NAME_LEN;
    data = snmp_parse_var_op(data, objid, &vp->name_length, &vp->type,
			      &vp->val_len, &var_val, &data_len);
    if (data == NULL)
      return SNMP_CLASS_ASN1ERROR;
    op = (oid *)malloc((unsigned)vp->name_length * sizeof(oid));

    memcpy((char *)op, (char *)objid, vp->name_length * sizeof(oid));
    vp->name = op;

    len = MAX_SNMP_PACKET;
    switch((short)vp->type) {
    case ASN_INTEGER:
      vp->val.integer = (long *)malloc(sizeof(long));
      vp->val_len = sizeof(long);
      asn_parse_int(var_val, &len, &vp->type, vp->val.integer);
      break;

    case SMI_COUNTER:
    case SMI_GAUGE:
    case SMI_TIMETICKS:
    case SMI_UINTEGER:
      vp->val.integer = (long *)malloc(sizeof(long));
      vp->val_len = sizeof(long);
      asn_parse_unsigned_int(var_val, &len, &vp->type, vp->val.integer);
      break;

    case SMI_COUNTER64:
      vp->val.counter64 = (struct counter64 *)malloc(sizeof(struct counter64));
      vp->val_len = sizeof(struct counter64);
      asn_parse_unsigned_int64(var_val, &len, &vp->type,
			       vp->val.counter64);
      break;
	
    case ASN_OCTET_STR:
    case SMI_IPADDRESS:
    case SMI_OPAQUE:
    case SMI_NSAP:
      vp->val.string = (unsigned char *)malloc((unsigned)vp->val_len);
      asn_parse_string(var_val, &len, &vp->type, vp->val.string, &vp->val_len);
      break;

    case ASN_OBJECT_ID:
      vp->val_len = ASN_MAX_NAME_LEN;
      asn_parse_objid(var_val, &len, &vp->type, objid, &vp->val_len);
      //vp->val_len *= sizeof(oid);
      vp->val.objid = (oid *)malloc((unsigned)vp->val_len * sizeof(oid));

      memcpy((char *)vp->val.objid,
	     (char *)objid,
	     vp->val_len * sizeof(oid));
      break;

    case SNMP_NOSUCHOBJECT:
    case SNMP_NOSUCHINSTANCE:
    case SNMP_ENDOFMIBVIEW:
    case ASN_NULL:
      break;

    default:
      ASNERROR("bad type returned ");
      return SNMP_CLASS_ASN1ERROR;
    }
  }
  return SNMP_CLASS_SUCCESS;
}


int snmp_parse_data_pdu(snmp_pdu *pdu, unsigned char *&data, int &length)
{
  oid	    objid[ASN_MAX_NAME_LEN];
  int	    four = 4;
  unsigned char  type;

  data = asn_parse_header(data, &length, &type);
  if (data == NULL) return SNMP_CLASS_ASN1ERROR;

  pdu->command = type;

  if (pdu->command != TRP_REQ_MSG)
  {
    // get the rid error status and error index
    data = asn_parse_int(data, &length, &type, &pdu->reqid);
    if (data == NULL) return SNMP_CLASS_ASN1ERROR;

    data = asn_parse_int(data, &length, &type, &pdu->errstat);
    if (data == NULL) return SNMP_CLASS_ASN1ERROR;

    data = asn_parse_int(data, &length, &type, &pdu->errindex);
    if (data == NULL) return SNMP_CLASS_ASN1ERROR;
  }
  else
  {  // is a trap

    // get the enterprise
    pdu->enterprise_length = ASN_MAX_NAME_LEN;
    data = asn_parse_objid(data, &length, &type,
			   objid, &pdu->enterprise_length);
    if (data == NULL) return SNMP_CLASS_ASN1ERROR;

    pdu->enterprise = (oid *)malloc(pdu->enterprise_length * sizeof(oid));

    memcpy((char *)pdu->enterprise,(char *)objid,
	   pdu->enterprise_length * sizeof(oid));

    // get source address
    data = asn_parse_string(data, &length, &type,
			    (unsigned char *)&pdu->agent_addr.sin_addr.s_addr,
			    &four);
    if (data == NULL) return SNMP_CLASS_ASN1ERROR;

    // get trap type
    long dummy = 0;
    data = asn_parse_int(data, &length, &type, &dummy);
    pdu->trap_type = dummy;

    if (data == NULL) return SNMP_CLASS_ASN1ERROR;

    // trap specific type
    dummy = 0;
    data = asn_parse_int(data, &length, &type, &dummy);
    pdu->specific_type = dummy;
    if (data == NULL) return SNMP_CLASS_ASN1ERROR;

    // timestamp
    data = asn_parse_unsigned_int(data, &length, &type, &pdu->time);
    if (data == NULL) return SNMP_CLASS_ASN1ERROR;
  }
  return SNMP_CLASS_SUCCESS;
}


// parse a pdu
int snmp_parse(struct snmp_pdu *pdu,
                unsigned char *data, int data_length,
		unsigned char *community_name,
		int &community_len,
		snmp_version &spp_version)
{
  long    version = -1;

  // authenticates message and returns length if valid
  data = snmp_auth_parse(data, &data_length,
			 community_name, &community_len,
			 &version);
  if (data == NULL)
    return SNMP_CLASS_ASN1ERROR;

  if(version != SNMP_VERSION_1 && version != SNMP_VERSION_2C) {
    ASNERROR("Wrong version");
    return SNMP_CLASS_BADVERSION;
  }

  spp_version = (snmp_version) version;

  int res = snmp_parse_data_pdu(pdu, data, data_length);
  if (res != SNMP_CLASS_SUCCESS)
    return res;

  return snmp_parse_vb(pdu, data, data_length);
}


// Parse the field HeaderData of a SNMPv3 message and return the values.
unsigned char *asn1_parse_header_data(unsigned char *buf, int *buf_len,
				      long *msg_id, long *msg_max_size,
				      unsigned char *msg_flags,
				      long *msg_security_model)
{
  unsigned char *buf_ptr = buf;
  int length = *buf_len;
  unsigned char type;

  buf = asn_parse_header(buf, &length, &type);
  if (!buf)
  {
    debugprintf(0, "Parse error in header HeaderData");
    return 0;
  }

  if (type != ASN_SEQ_CON) {
    debugprintf(0, "wrong type in header of msgHeaderData");
    return 0;
  }

  buf = asn_parse_int(buf, &length, &type, msg_id);
  if (!buf) {
    debugprintf(0, "Parse error: msg_id");
    return 0;
  }

  buf = asn_parse_int(buf, &length, &type, msg_max_size);
  if (!buf) {
    debugprintf(0, "Parse error: msg_max_size");
    return 0;
  }

  int dummy = 1;
  buf = asn_parse_string(buf, &length, &type, msg_flags, &dummy);

  if ((dummy !=1) || (!buf)) {
    debugprintf(0, "Parse error: msg_flags");
    return 0;
  }

  buf = asn_parse_int(buf, &length, &type, msg_security_model);
  if (!buf) {
    debugprintf(0, "Parse error: msg_security_model");
    return 0;
  }

  if (length) {
    debugprintf(0, "Parse error: wrong length in header of HeaderData");
    return 0;
  }

  debugprintf(3, "Parsed HeaderData: globalDataLength(0x%x), msg_id(%ld), "
	     "msg_max_size(0x%lx), msg_flags(0x%x), msg_security_model(0x%lx)",
	      length, *msg_id, *msg_max_size, *msg_flags, *msg_security_model);

  *buf_len -= SAFE_INT_CAST(buf - buf_ptr);
  return buf;
}

// Encode the given values for the HeaderData into the buffer.
unsigned char *asn1_build_header_data(unsigned char *outBuf, int *maxLength,
				       long msgID,
				       long maxMessageSize,
				       unsigned char msgFlags,
				       long securityModel)

{
  unsigned char buf[MAXLENGTH_GLOBALDATA];
  unsigned char *bufPtr = (unsigned char*)&buf;
  unsigned char *outBufPtr = outBuf;
  int length = *maxLength;
  int totalLength;

#ifdef INVALID_MAXMSGSIZE
  debugprintf(-10, "\nWARNING: Using constant MaxMessageSize!\n");
  maxMessageSize = 65535;
#endif

  debugprintf(3, "Coding msgID(%ld), maxMessageSize(0x%lx), "
	      "msgFlags(0x%x), securityModel(0x%lx)",
              msgID, maxMessageSize, msgFlags, securityModel);

  bufPtr = asn_build_int(bufPtr, &length, ASN_UNI_PRIM | ASN_INTEGER, &msgID);
  if (bufPtr == NULL) {
    debugprintf(0, "asn_build_header_data: Error coding msgID");
    return NULL;
  }
  bufPtr = asn_build_int(bufPtr, &length, ASN_UNI_PRIM | ASN_INTEGER,
                         &maxMessageSize);
  if (bufPtr == NULL) {
    debugprintf(0, "asn_build_header_data: Error coding maxMessageSize");
    return NULL;
  }

  bufPtr = asn_build_string(bufPtr, &length, ASN_UNI_PRIM | ASN_OCTET_STR,
                            &msgFlags, 1);
  if (bufPtr == NULL) {
    debugprintf(0, "asn_build_header_data: Error coding msgFlags");
    return NULL;
  }

  bufPtr = asn_build_int(bufPtr, &length, ASN_UNI_PRIM | ASN_INTEGER,
                         &securityModel);
  if (bufPtr == NULL) {
    debugprintf(0, "asn_build_header_data: Error coding securityModel");
    return NULL;
  }

  totalLength = SAFE_INT_CAST(bufPtr - (unsigned char*)&buf);

  debugprintf(3, "Coding sequence (headerdata), length = 0x%x", totalLength);
  outBufPtr = asn_build_sequence(outBufPtr, maxLength, ASN_SEQ_CON,
                                 totalLength);

  if (outBufPtr == NULL) {
    debugprintf(0, "asn_build_header_data: Error coding seq headerdata");
    return NULL;
  }

  if (*maxLength < totalLength) {
    debugprintf(0, "asn_build_header_data: Length error");
    return NULL;
  }

  memcpy(outBufPtr, (unsigned char*)&buf, totalLength);
  outBufPtr += totalLength;
  *maxLength -= totalLength;

  debugprintf(21, "bufHeaderData:");
  debughexprintf(21, outBuf, SAFE_INT_CAST(outBufPtr - outBuf));

  return outBufPtr;
}

// Parse the ScopedPDU and return the encoded values.
unsigned char *asn1_parse_scoped_pdu(
         unsigned char *scoped_pdu, int *scoped_pdu_len,
         unsigned char *context_engine_id, int *context_engine_id_len,
         unsigned char *context_name, int *context_name_len)
{
  unsigned char type;

  scoped_pdu = asn_parse_header(scoped_pdu, scoped_pdu_len, &type);
  if (!scoped_pdu) {
    debugprintf(0, "Parse error: Wrong header in scoped_pdu.");
    return 0;
  }

  if (type != ASN_SEQ_CON) {
    debugprintf(0, "Parse error: Wrong header type in scoped_pdu.");
    return 0;
  }

  scoped_pdu = asn_parse_string(scoped_pdu, scoped_pdu_len, &type,
                                context_engine_id, context_engine_id_len);
  if (!scoped_pdu) {
    debugprintf(0, "Parse error: context_engine_id");
    return 0;
  }

  scoped_pdu = asn_parse_string(scoped_pdu, scoped_pdu_len, &type,
                                context_name, context_name_len);
  if (!scoped_pdu) {
    debugprintf(0, "mpParseScopedPDU: bad parse of context_name");
    return 0;
  }

  debugprintf(3, "Parsed scoped_pdu: context_engine_id length(0x%x), "
	      "context_name length(0x%x)",
	      *context_engine_id_len, *context_name_len);

  return scoped_pdu;
}

// Encode the given values for the scopedPDU into the buffer.
unsigned char *asn1_build_scoped_pdu(
                   unsigned char *outBuf, int *max_len,
                   unsigned char *contextEngineID, long contextEngineIDLength,
                   unsigned char *contextName, long contextNameLength,
                   unsigned char *data, long dataLength)
{
  Buffer<unsigned char> buffer(MAX_SNMP_PACKET);
  unsigned char *bufPtr = buffer.get_ptr();
  unsigned char *outBufPtr = outBuf;

  LOG_BEGIN(loggerModuleName, DEBUG_LOG | 10);
  LOG("ASN1: coding (context engine id) (context name)");
  LOG(OctetStr(contextEngineID, contextEngineIDLength).get_printable());
  LOG(OctetStr(contextName, contextNameLength).get_printable());
  LOG_END;

  bufPtr = asn_build_string(bufPtr, max_len, ASN_UNI_PRIM | ASN_OCTET_STR,
                            contextEngineID, contextEngineIDLength);
  if (!bufPtr)
  {
    LOG_BEGIN(loggerModuleName, ERROR_LOG | 1);
    LOG("ASN1: Error encoding contextEngineID");
    LOG_END;

    return 0;
  }

  bufPtr = asn_build_string(bufPtr, max_len, ASN_UNI_PRIM | ASN_OCTET_STR,
                            contextName, contextNameLength);
  if (!bufPtr)
  {
    LOG_BEGIN(loggerModuleName, ERROR_LOG | 1);
    LOG("ASN1: Error encoding contextName");
    LOG_END;

    return 0;
  }

  long bufLength = SAFE_INT_CAST(bufPtr - buffer.get_ptr());

  memcpy((char *)bufPtr, (char *)data, dataLength);
  bufLength += dataLength;

  LOG_BEGIN(loggerModuleName, DEBUG_LOG | 10);
  LOG("ASN1: Encoding scoped PDU sequence (len)");
  LOG(bufLength);
  LOG_END;

  outBufPtr = asn_build_sequence(outBufPtr, max_len, ASN_SEQ_CON, bufLength);
  if (!outBufPtr)
  {
    LOG_BEGIN(loggerModuleName, ERROR_LOG | 1);
    LOG("ASN1: Error encoding scopedPDU sequence");
    LOG_END;

    return 0;
  }

  memcpy(outBufPtr, buffer.get_ptr(), bufLength);
  outBufPtr += bufLength;

#ifdef __DEBUG
  LOG_BEGIN(loggerModuleName, DEBUG_LOG | 15);
  LOG("ASN1: Result of build_scoped_pdu (len) (data)");
  LOG(outBufPtr - outBuf);
  LOG(OctetStr(outBuf, outBufPtr - outBuf).get_printable_hex());
  LOG_END;
#endif

  return outBufPtr;
}

} // end of namespace Snmp_pp