derparse.c

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// Function:
//    ASNDerCalcTokenLength
//
// Parameters:
//    [in]  nLength           -  Length to calculate length bytes for.
//    [in]  nDataLength       -  Actual Data length value.
//
// Returns:
//    long  Number of bytes necessary to represent a token, length and data
//
// Comments :
//    Helper function to calculate a token and value size, based on a
//    supplied length value, and any binary data that will need to be
//    written out.
//
////////////////////////////////////////////////////////////////////////////

long ASNDerCalcTokenLength( long nLength, long nDataLength )
{
   // Add a byte to the length size to account for a single byte to
   // hold the token type.
   long  nTotalLength = ASNDerCalcNumLengthBytes( nLength ) + 1;

   return nTotalLength + nDataLength;
}


/////////////////////////////////////////////////////////////////////////////
//
// Function:
//    ASNDerCalcElementLength
//
// Parameters:
//    [in]  nDataLength       -  Length of data.
//    [out] pnInternalLength  -  Filled out with length of element
//                               without sequence info.
//
// Returns:
//    long  Number of bytes necessary to represent an element
//
// Comments :
//    Helper function to calculate an element length.  An element consists
//    of a sequence token, a type token and then the data.
//
////////////////////////////////////////////////////////////////////////////

long ASNDerCalcElementLength( long nDataLength, long* pnInternalLength )
{
   // First the type token and the actual data
   long  nTotalLength = ASNDerCalcTokenLength( nDataLength, nDataLength );

   // Internal length is the length without the element sequence token
   if ( NULL != pnInternalLength )
   {
      *pnInternalLength = nTotalLength;
   }

   // Next add in the element's sequence token (remember that its
   // length is the total length of the type token and data)
   nTotalLength += ASNDerCalcTokenLength( nTotalLength, 0L );

   return nTotalLength;
}

/////////////////////////////////////////////////////////////////////////////
//
// Function:
//    ASNDerCalcMechListLength
//
// Parameters:
//    [in]  mechoid           -  Mech OID to put in list.
//    [out] pnInternalLength  -  Filled out with length of element
//                               without the primary sequence token.
//
// Returns:
//    long  Number of bytes necessary to represent a mechList
//
// Comments :
//    Helper function to calculate a MechList length.  A mechlist consists
//    of a NegTokenInit sequence token, a sequence token for the MechList
//    and finally a list of OIDs.  In our case, we only really have one
//    OID.
//
////////////////////////////////////////////////////////////////////////////

long ASNDerCalcMechListLength( SPNEGO_MECH_OID mechoid, long* pnInternalLength )
{
   // First the OID
   long  nTotalLength = g_stcMechOIDList[mechoid].iLen;

   // Next add in a sequence token
   nTotalLength += ASNDerCalcTokenLength( nTotalLength, 0L );

   // Internal length is the length without the element sequence token
   if ( NULL != pnInternalLength )
   {
      *pnInternalLength = nTotalLength;
   }

   // Finally add in the element's sequence token
   nTotalLength += ASNDerCalcTokenLength( nTotalLength, 0L );

   return nTotalLength;
}


/////////////////////////////////////////////////////////////////////////////
//
// Function:
//    ASNDerWriteLength
//
// Parameters:
//    [out] pbData            -  Buffer to write into.
//    [in]  nLength           -  Length to write out.
//
// Returns:
//    int   Number of bytes written out
//
// Comments :
//    Helper function to write out a length value following DER rules .
//
////////////////////////////////////////////////////////////////////////////

int ASNDerWriteLength( unsigned char* pbData, long nLength )
{
   int   nNumBytesRequired = ASNDerCalcNumLengthBytes( nLength );
   int   nNumLengthBytes = nNumBytesRequired - 1;


   if ( nNumBytesRequired > 1 )
   {

      // Write out the number of bytes following which will be used
      *pbData = (unsigned char ) ( LEN_XTND | nNumLengthBytes );

      // Point to where we'll actually write the length
      pbData++;

#ifdef __LITTLE_ENDIAN__

      // There may be a cleaner way to do this, but for now, this seems to be
      // an easy way to do the transformation
      switch ( nNumLengthBytes )
      {
         case 1:
         {
            // Cast the length to a single byte, since we know that it
            // is 0x7F or less (or we wouldn't only need a single byte).
      
            *pbData = (unsigned char) nLength;
            break;
         }

         case 2:
         {
            *pbData = *( ( (unsigned char*) &nLength ) + 1 );
            *( pbData + 1) = *( ( (unsigned char*) &nLength ) );
            break;
         }

         case 3:
         {
            *pbData = *( ( (unsigned char*) &nLength ) + 3 );
            *( pbData + 1) = *( ( (unsigned char*) &nLength ) + 2 );
            *( pbData + 2) = *( ( (unsigned char*) &nLength ) );
            break;
         }

         case 4:
         {
            *pbData = *( ( (unsigned char*) &nLength ) + 3 );
            *( pbData + 1) = *( ( (unsigned char*) &nLength ) + 2 );
            *( pbData + 2) = *( ( (unsigned char*) &nLength ) + 1 );
            *( pbData + 3) = *( ( (unsigned char*) &nLength ) );
            break;
         }

      }  // SWITCH ( nNumLengthBytes )

#else
      // We are Big-Endian, so the length can be copied in from the source
      // as is.  Ensure that we adjust for the number of bytes we actually
      // copy.

      memcpy( pbData,
               ( (unsigned char *) &nLength ) + ( 4 - nNumLengthBytes ), nNumLengthBytes );
#endif

   }  // IF > 1 byte for length
   else
   {
      // Cast the length to a single byte, since we know that it
      // is 0x7F or less (or we wouldn't only need a single byte).
      
      *pbData = (unsigned char) nLength;
   }

   return nNumBytesRequired;
}

/////////////////////////////////////////////////////////////////////////////
//
// Function:
//    ASNDerWriteToken
//
// Parameters:
//    [out] pbData            -  Buffer to write into.
//    [in]  ucType            -  Token Type
//    [in]  pbTokenValue      -  Actual Value
//    [in]  nLength           -  Length of Data.
//
// Returns:
//    int   Number of bytes written out
//
// Comments :
//    Helper function to write out a token and any associated data.  If
//    pbTokenValue is non-NULL, then it is written out in addition to the
//    token identifier and the length bytes.
//
////////////////////////////////////////////////////////////////////////////

int ASNDerWriteToken( unsigned char* pbData, unsigned char ucType,
                     unsigned char* pbTokenValue, long nLength )
{
   int   nTotalBytesWrittenOut = 0L;
   int   nNumLengthBytesWritten = 0L;

   // Write out the type
   *pbData = ucType;

   // Wrote 1 byte, and move data pointer
   nTotalBytesWrittenOut++;
   pbData++;

   // Now write out the length and adjust the number of bytes written out
   nNumLengthBytesWritten = ASNDerWriteLength( pbData, nLength );

   nTotalBytesWrittenOut += nNumLengthBytesWritten;
   pbData += nNumLengthBytesWritten;

   // Write out the token value if we got one.  The assumption is that the
   // nLength value indicates how many bytes are in pbTokenValue.

   if ( NULL != pbTokenValue )
   {
      memcpy( pbData, pbTokenValue, nLength );
      nTotalBytesWrittenOut += nLength;
   }

   return nTotalBytesWrittenOut;
}


/////////////////////////////////////////////////////////////////////////////
//
// Function:
//    ASNDerWriteOID
//
// Parameters:
//    [out] pbData            -  Buffer to write into.
//    [in]  eMechOID          -  OID to write out.
//
// Returns:
//    int   Number of bytes written out
//
// Comments :
//    Helper function to write out an OID.  For these we have the raw bytes
//    listed in a global structure.  The caller simply indicates which OID
//    should be written and we will splat out the data.
//
////////////////////////////////////////////////////////////////////////////

int ASNDerWriteOID( unsigned char* pbData, SPNEGO_MECH_OID eMechOID )
{

   memcpy( pbData, g_stcMechOIDList[eMechOID].ucOid, g_stcMechOIDList[eMechOID].iLen );

   return g_stcMechOIDList[eMechOID].iLen;
}


/////////////////////////////////////////////////////////////////////////////
//
// Function:
//    ASNDerWriteMechList
//
// Parameters:
//    [out] pbData            -  Buffer to write into.
//    [in]  eMechOID          -  OID to put in MechList.
//
// Returns:
//    int   Number of bytes written out
//
// Comments :
//    Helper function to write out a MechList.  A MechList consists of the
//    Init Token Sequence, a sequence token and then the list of OIDs.  In
//    our case the OID is from a global array of known OIDs.
//
////////////////////////////////////////////////////////////////////////////

long ASNDerWriteMechList( unsigned char* pbData, SPNEGO_MECH_OID mechoid )
{
   // First get the length
   long  nInternalLength = 0L;
   long  nMechListLength = ASNDerCalcMechListLength( mechoid, &nInternalLength );
   long  nTempLength = 0L;

   nTempLength = ASNDerWriteToken( pbData, SPNEGO_NEGINIT_ELEMENT_MECHTYPES,
                                    NULL, nInternalLength );

   // Adjust the data pointer
   pbData += nTempLength;

   // Now write the Sequence token and the OID (the OID is a BLOB in the global
   // structure.

   nTempLength = ASNDerWriteToken( pbData, SPNEGO_CONSTRUCTED_SEQUENCE,
                                    g_stcMechOIDList[mechoid].ucOid,
                                    g_stcMechOIDList[mechoid].iLen );

   return nMechListLength;
}


/////////////////////////////////////////////////////////////////////////////
//
// Function:
//    ASNDerWriteElement
//
// Parameters:
//    [out] pbData            -  Buffer to write into.
//    [in]  ucElementSequence -  Sequence Token
//    [in]  ucType            -  Token Type
//    [in]  pbTokenValue      -  Actual Value
//    [in]  nLength           -  Length of Data.
//
// Returns:
//    int   Number of bytes written out
//
// Comments :
//    Helper function to write out a SPNEGO Token element.  An element
//    consists of a sequence token, a type token and the associated data.
//
////////////////////////////////////////////////////////////////////////////

int ASNDerWriteElement( unsigned char* pbData, unsigned char ucElementSequence,
                        unsigned char ucType, unsigned char* pbTokenValue, long nLength )
{
   // First get the length
   long  nInternalLength = 0L;
   long  nElementLength = ASNDerCalcElementLength( nLength, &nInternalLength );
   long  nTempLength = 0L;

   // Write out the sequence byte and the length of the type and data
   nTempLength = ASNDerWriteToken( pbData, ucElementSequence, NULL, nInternalLength );

   // Adjust the data pointer
   pbData += nTempLength;

   // Now write the type and the data.
   nTempLength = ASNDerWriteToken( pbData, ucType, pbTokenValue, nLength );

   return nElementLength;
}