derparse.c

代理服务器 squid-2.6.STABLE16

// Copyright (C) 2002 Microsoft Corporation
// All rights reserved.
//
// THIS CODE AND INFORMATION IS PROVIDED "AS IS"
// WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
// OR IMPLIED, INCLUDING BUT NOT LIMITED
// TO THE IMPLIED WARRANTIES OF MERCHANTIBILITY
// AND/OR FITNESS FOR A PARTICULAR PURPOSE.
//
// Date    - 10/08/2002
// Author  - Sanj Surati


/////////////////////////////////////////////////////////////
//
// DERPARSE.C
//
// SPNEGO Token Handler Source File
//
// Contains implementation of ASN.1 DER read/write functions
// as defined in DERPARSE.H.
//
/////////////////////////////////////////////////////////////

#include <stdlib.h>
#include <stdio.h>
#include <memory.h>
#include "spnego.h"
#include "derparse.h"

//
// The GSS Mechanism OID enumeration values (SPNEGO_MECH_OID) control which offset in
// the array below, that a mechanism can be found.
//
MECH_OID g_stcMechOIDList [] =
{
   { (unsigned char*) "\x06\x09\x2a\x86\x48\x82\xf7\x12\x01\x02\x02",  11, 9, spnego_mech_oid_Kerberos_V5_Legacy  },  //  1.2.840.48018.1.2.2 
   { (unsigned char*) "\x06\x09\x2a\x86\x48\x86\xf7\x12\x01\x02\x02",  11, 9, spnego_mech_oid_Kerberos_V5         },  //  1.2.840.113554.1.2.2
   { (unsigned char*) "\x06\x06\x2b\x06\x01\x05\x05\x02",               8, 6, spnego_mech_oid_Spnego              },  //  1.3.6.1.1.5.5.2
   { (unsigned char*) "",												0, 0, spnego_mech_oid_NotUsed             }   //  Placeholder
};

/////////////////////////////////////////////////////////////////////////////
//
// Function:
//    ASNDerGetLength
//
// Parameters:
//    [in]  pbLengthData      -  DER Length Data
//    [in]  nBoundaryLength   -  Length that value must not exceed.
//    [out] pnLength          -  Filled out with length value
//    [out] pnNumLengthBytes  -  Filled out with number of bytes
//                               consumed by DER length.
//
// Returns:
//    int   Success - SPNEGO_E_SUCCESS
//          Failure - SPNEGO API Error code
//
// Comments :
//    Interprets the data at pbLengthData as a DER length.  The length must
//    fit within the bounds of nBoundary length.  We do not currently
//    process lengths that take more than 4 bytes.
//
////////////////////////////////////////////////////////////////////////////

int ASNDerGetLength( unsigned char* pbLengthData, long nBoundaryLength, long* pnLength,
                     long* pnNumLengthBytes )
{
   int   nReturn = SPNEGO_E_INVALID_LENGTH;
   int   nNumLengthBytes = 0;

   // First check if the extended length bit is set

   if ( *pbLengthData & LEN_XTND )
   {
      // Lower 7 bits contain the number of trailing bytes that describe the length
      nNumLengthBytes = *pbLengthData & LEN_MASK;

      // Check that the number of bytes we are about to read is within our boundary
      // constraints

      if ( nNumLengthBytes <= nBoundaryLength - 1 )
      {

         // For now, our handler won't deal with lengths greater than 4 bytes
         if ( nNumLengthBytes >= 1 && nNumLengthBytes <= 4 )
         {
            // 0 out the initial length
            *pnLength = 0L;

            // Bump by 1 byte
            pbLengthData++;

   #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:
               {
                  *( ( (unsigned char*) pnLength ) ) = *pbLengthData;
                  break;
               }

               case 2:
               {
                  *( ( (unsigned char*) pnLength ) ) = *(pbLengthData + 1);
                  *( ( (unsigned char*) pnLength ) + 1 ) = *(pbLengthData);

                  break;
               }

               case 3:
               {
                  *( ( (unsigned char*) pnLength ) ) = *(pbLengthData + 2);
                  *( ( (unsigned char*) pnLength ) + 2 ) = *(pbLengthData + 1);
                  *( ( (unsigned char*) pnLength ) + 3 ) = *(pbLengthData);
                  break;
               }

               case 4:
               {
                  *( ( (unsigned char*) pnLength ) ) = *(pbLengthData + 3);
                  *( ( (unsigned char*) pnLength ) + 1 ) = *(pbLengthData + 2);
                  *( ( (unsigned char*) pnLength ) + 2 ) = *(pbLengthData + 1);
                  *( ( (unsigned char*) pnLength ) + 3 ) = *(pbLengthData);
                  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( ( (unsigned char *) pnLength ) + ( 4 - nNumLengthBytes ),
                     pbLengthData, nNumLengthBytes );
   #endif

            // Account for the initial length byte
            *pnNumLengthBytes = nNumLengthBytes + 1;
            nReturn = SPNEGO_E_SUCCESS;

         }  // IF Valid Length

      }  // IF num bytes to read is within the boundary length

   }  // IF xtended length
   else
   {

      // Extended bit is not set, so the length is in the value and the one
      // byte describes the length
      *pnLength = *pbLengthData & LEN_MASK;
      *pnNumLengthBytes = 1;
      nReturn = SPNEGO_E_SUCCESS;

   }
   LOG(("ASNDerGetLength returned %d\n",nReturn));
   return nReturn;
}


/////////////////////////////////////////////////////////////////////////////
//
// Function:
//    ASNDerCheckToken
//
// Parameters:
//    [in]  pbTokenData       -  Token Data
//    [in]  nToken            -  Token identifier to check for
//    [in]  nLengthWithToken  -  Expected token length (with data)
//    [in]  nBoundaryLength   -  Length that value must not exceed.
//    [out] pnLength          -  Filled out with data length
//    [out] pnTokenLength     -  Filled out with number of bytes 
//                               consumed by token identifier and length.
//
// Returns:
//    int   Success - SPNEGO_E_SUCCESS
//          Failure - SPNEGO API Error code
//
// Comments :
//    Checks the data pointed to by pbTokenData for the specified token
//    identifier and the length that immediately follows.  If
//    nLengthWithToken is > 0, the calculated length must match.  The
//    length must also not exceed the specified boundary length .
//
////////////////////////////////////////////////////////////////////////////

int ASNDerCheckToken( unsigned char* pbTokenData, unsigned char nToken,
                        long nLengthWithToken, long nBoundaryLength,
                        long* pnLength, long* pnTokenLength )
{

   int   nReturn = SPNEGO_E_INVALID_LENGTH;
   long  nNumLengthBytes = 0L;

   // Make sure that we've at least got 2 bytes of room to work with

   if ( nBoundaryLength >= 2 )
   {
      // The first byte of the token data MUST match the specified token
      if ( *pbTokenData == nToken )
      {
         // Next byte indicates the length
         pbTokenData++;

         // Get the length described by the token
         if ( ( nReturn = ASNDerGetLength( pbTokenData, nBoundaryLength, pnLength,
                                             &nNumLengthBytes )  ) == SPNEGO_E_SUCCESS )
         {
            // Verify that the length is LESS THAN the boundary length
            // (this should prevent us walking out of our buffer)
            if ( ( nBoundaryLength - ( nNumLengthBytes + 1 ) < *pnLength ) )
            {

               nReturn = SPNEGO_E_INVALID_LENGTH;

            }

            // If we were passed a length to check, do so now
            if ( nLengthWithToken > 0L )
            {

               // Check that the expected length matches
               if ( ( nLengthWithToken - ( nNumLengthBytes + 1 ) ) != *pnLength )
               {

                  nReturn = SPNEGO_E_INVALID_LENGTH;

               }

            }  // IF need to validate length

            if ( SPNEGO_E_SUCCESS == nReturn )
            {
               *pnTokenLength = nNumLengthBytes + 1;
            }

         }  // IF ASNDerGetLength

      }  // IF token matches
      else
      {
         nReturn = SPNEGO_E_TOKEN_NOT_FOUND;
      }

   }  // IF Boundary Length is at least 2 bytes 

   LOG(("ASNDerCheckToken returned %d\n",nReturn));
   return nReturn;
}

/////////////////////////////////////////////////////////////////////////////
//
// Function:
//    ASNDerCheckOID
//
// Parameters:
//    [in]  pbTokenData       -  Token Data
//    [in]  nMechOID          -  OID we are looking for
//    [in]  nBoundaryLength   -  Length that value must not exceed.
//    [out] pnTokenLength     -  Filled out with number of bytes
//                               consumed by token and data.
//
// Returns:
//    int   Success - SPNEGO_E_SUCCESS
//          Failure - SPNEGO API Error code
//
// Comments :
//    Checks the data pointed to by pbTokenData for the specified OID.
//
////////////////////////////////////////////////////////////////////////////

int ASNDerCheckOID( unsigned char* pbTokenData, SPNEGO_MECH_OID nMechOID, long nBoundaryLength,
                     long* pnTokenLength )
{
   int   nReturn = 0L;
   long  nLength = 0L;

   // Verify that we have an OID token
   if ( ( nReturn = ASNDerCheckToken( pbTokenData, OID, 0L, nBoundaryLength, 
                                       &nLength, pnTokenLength ) ) == SPNEGO_E_SUCCESS )
   {
      // Add the data length to the Token Length
      *pnTokenLength += nLength;

      // Token Lengths plus the actual length must match the length in our OID list element.
      // If it doesn't, we're done
      if ( *pnTokenLength == g_stcMechOIDList[nMechOID].iLen )
      {
         // Memcompare the token and the expected field
         if ( memcmp( pbTokenData, g_stcMechOIDList[nMechOID].ucOid, *pnTokenLength ) != 0 )
         {
   	    LOG(("ASNDerCheckOID memcmp failed\n"));
            nReturn = SPNEGO_E_UNEXPECTED_OID;
         }
      }
      else
      {
         LOG(("ASNDerCheckOID token length failed\n"));
         nReturn = SPNEGO_E_UNEXPECTED_OID;
      }

   }  // IF OID Token CHecks

   LOG(("ASNDerCheckOID returned %d\n",nReturn));
   return nReturn;
}

/////////////////////////////////////////////////////////////////////////////
//
// Function:
//    ASNDerCalcNumLengthBytes
//
// Parameters:
//    [in]  nLength           -  Length to calculate length bytes for.
//
// Returns:
//    int   Number of bytes necessary to represent length
//
// Comments :
//    Helper function to calculate the number of length bytes necessary to
//    represent a length value.  For our purposes, a 32-bit value should be
//    enough to describea length.
//
////////////////////////////////////////////////////////////////////////////

int ASNDerCalcNumLengthBytes( long nLength )
{
      if ( nLength <= 0x7F )
      {
         // A single byte will be sufficient for describing this length.
         // The byte will simply contain the length
         return 1;
      }
      else if ( nLength <= 0xFF )
      {
         // Two bytes are necessary, one to say how many following bytes
         // describe the length, and one to give the length
         return 2;
      }
      else if ( nLength <= 0xFFFF )
      {
         // Three bytes are necessary, one to say how many following bytes
         // describe the length, and two to give the length
         return 3;
      }
      else if ( nLength <= 0xFFFFFF )
      {
         // Four bytes are necessary, one to say how many following bytes
         // describe the length, and three to give the length
         return 4;
      }
      else
      {
         // Five bytes are necessary, one to say how many following bytes
         // describe the length, and four to give the length
         return 5;
      }
}


/////////////////////////////////////////////////////////////////////////////
//