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|
/*
* This filter is a flavor of the filter IIS uses for compression.
* (Original filter written by David Treadwell on July 1997.)
*
* ISA and IIS let you accumulate Requests chunks into a complete
* Request.
* The following filter is an example to a filter that collects the
* response chunks and then allows you to change them depending on the
* complete response.
* This filter works with 2 notifications.
* In Send Raw Data it collects the response's chunks, sends 0 bytes
* instead of them (i.e. sends nothing).
* Then, when all the chunks of this response passed Send Raw Data
* notification, ISA thinks the complete response was sent. So
* it calls End Of Request Notification. End Of Request Notification
* will be the place where we will send the complete response.
*
* Note. Since the filter allocates memory for accumulating a response from a
* Web server, it is vulnerable to a DoS attack. In this sample we show how
* to handle that issue using a threshold. When the memory needed for the
* response exceeds that threshold, the filter will behave as if it received
* an end-of-request notification and will call OnEndOfRequest. The
* OnEndOfRequest function will try do to change the response based on the
* partial data accumulated. After doing this, the filter will notify the
* ISA Server Web proxy to stop sending notifications regarding the current
* request. After this, the filter will transparent and pass the response
* without altering it.
*/
#include <windows.h>
#include <httpfilt.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h>
#include <assert.h>
#include <time.h>
/*************** Declaration ***************/
const char *fileName = "C:\\LogWRM.txt"; // i made the C drive accessible to network service so this work fine
FILE *p = NULL;
const char LINE_TO_INSERT[] = "<h3>Brought to you by an ISA Web Filter</h3>\r\n";
const char CONTENT_LENGTH[] = "Content-Length:";
const int ACCUMULATION_SIZE_LIMIT = 10000;
/*************** Prototype ***************/
void logLn(char buffer[] ); // to log into a file to see the trace of the filter
static DWORD OnSendRawData(PHTTP_FILTER_CONTEXT pfc, PHTTP_FILTER_RAW_DATA pRawData);
static DWORD OnEndOfRequest(PHTTP_FILTER_CONTEXT pfc);
static void DisableNotifications(PHTTP_FILTER_CONTEXT pfc, DWORD flags);
static int strnstr(const char *string, const char *strCharSet , int n);
void OutputDebugStringF (const char* pchFormat, ...);
static bool InsertOurHTMLHeader(PHTTP_FILTER_CONTEXT pfc,LPBYTE *ppBuffer,LPDWORD lpdwLen);
static DWORD dwfnContentLen(LPSTR ContentLenLine,int iLineLen);
static DWORD IsFirstInCARP(PHTTP_FILTER_CONTEXT pfc, BOOL *IsFirst);
/*************** Implementation ***************/
void logLn(char buffer[] ){
time_t t;
time(&t);
if (p != NULL)
fprintf(p,"%s\t\t%s\n", ctime(&t), buffer);
};
BOOL WINAPI TerminateFilter ( DWORD dwFlags )
{
//logLn("" );
logLn("TerminateFilter" );
if (p != NULL)
fclose(p);
UNREFERENCED_PARAMETER(dwFlags);
return TRUE;
}
BOOL WINAPI GetFilterVersion ( PHTTP_FILTER_VERSION pVer )
{
p = fopen(fileName, "a+" );
logLn("GetFilterVersion" );
if (pVer == NULL)
{
SetLastError( ERROR_INVALID_PARAMETER);
return FALSE;
}
pVer->dwFilterVersion = HTTP_FILTER_REVISION;
pVer->dwFlags = SF_NOTIFY_END_OF_REQUEST | SF_NOTIFY_SECURE_PORT | SF_NOTIFY_NONSECURE_PORT | SF_NOTIFY_SEND_RAW_DATA //| SF_NOTIFY_ORDER_HIGH
;
return TRUE;
}
DWORD WINAPI HttpFilterProc (
PHTTP_FILTER_CONTEXT pfc,
DWORD NotificationType,
LPVOID pvNotification
)
{
logLn("HttpFilterProc: begin" );
OutputDebugStringA("WEBRESPONSEMODIFIER: entring HttpFilterProc.\n" );
DWORD dwRet = SF_STATUS_REQ_NEXT_NOTIFICATION;
switch (NotificationType)
{
case SF_NOTIFY_SEND_RAW_DATA:
dwRet = OnSendRawData(pfc, (PHTTP_FILTER_RAW_DATA)pvNotification);
break;
case SF_NOTIFY_END_OF_REQUEST:
dwRet = OnEndOfRequest(pfc);
break;
default:
// We cannot reach here, unless Web Filter support has a BAD ERROR.
SetLastError( ERROR_INVALID_PARAMETER);
dwRet = SF_STATUS_REQ_ERROR;
break;
}
logLn("HttpFilterProc: end" );
return dwRet;
}
/*
* OnSendRawData():
* During Send Raw Data Notification we do the following:
* 1) Append each chunk to an accumulation buffer (pRawData->cvInData).
* 2) Resize the Current chunk to 0 (don't send anything.)
*/
static DWORD OnSendRawData ( PHTTP_FILTER_CONTEXT pfc, PHTTP_FILTER_RAW_DATA pInRawData )
{
logLn("OnSendRawData" );
if ( NULL == pfc || NULL == pInRawData)
{
SetLastError( ERROR_INVALID_PARAMETER);
return SF_STATUS_REQ_ERROR;
}
/*
* Making the filter CARP-aware.
* The filter is active only if we are in the last array server.
*/
BOOL IsFirst;
DWORD dwErrorCode = IsFirstInCARP(pfc,&IsFirst) ;
if (dwErrorCode != ERROR_SUCCESS)
{
SetLastError(dwErrorCode);
return SF_STATUS_REQ_ERROR;
}
if (!IsFirst)
{
OutputDebugStringA("WEBRESPONSEMODIFIER: OnSendRawData, intra array server, do nothing.\n" );
DisableNotifications(pfc, SF_NOTIFY_SEND_RAW_DATA);
return SF_STATUS_REQ_NEXT_NOTIFICATION;
}
OutputDebugStringA("WEBRESPONSEMODIFIER: First array server, accumulate data.\n" );
/*
* Called first time for this request - then allocate pRawData.
*/
DWORD dwReserved = 0;
if ( NULL == pfc->pFilterContext )
{
pfc->pFilterContext = (LPVOID)pfc->AllocMem( pfc, sizeof(HTTP_FILTER_RAW_DATA), dwReserved);
if ( NULL == pfc->pFilterContext )
{
DisableNotifications( pfc, SF_NOTIFY_END_OF_REQUEST | SF_NOTIFY_SEND_RAW_DATA);
SetLastError( ERROR_NOT_ENOUGH_MEMORY );
return SF_STATUS_REQ_ERROR;
}
PHTTP_FILTER_RAW_DATA pRawData = (PHTTP_FILTER_RAW_DATA)pfc->pFilterContext;
pRawData->cbInBuffer = pInRawData->cbInBuffer;
pRawData->pvInData = (LPVOID)pfc->AllocMem( pfc, pRawData->cbInBuffer, dwReserved);
if ( NULL == pRawData->pvInData )
{
DisableNotifications(pfc,SF_NOTIFY_END_OF_REQUEST | SF_NOTIFY_SEND_RAW_DATA);
SetLastError( ERROR_NOT_ENOUGH_MEMORY );
return SF_STATUS_REQ_ERROR;
}
pRawData->cbInData = 0;
pRawData->dwReserved = pInRawData->dwReserved ;
}
/*
* Get the pRawData from the Request Context.
*/
PHTTP_FILTER_RAW_DATA pRawData = (PHTTP_FILTER_RAW_DATA)pfc->pFilterContext;
/*
* Check for integer overflow
*/
DWORD NewSize = pInRawData->cbInData + pRawData->cbInData ;
if (NewSize < pInRawData->cbInData || NewSize < pRawData->cbInData )
{
DisableNotifications(pfc,SF_NOTIFY_END_OF_REQUEST | SF_NOTIFY_SEND_RAW_DATA);
SetLastError( ERROR_NOT_ENOUGH_MEMORY );
return SF_STATUS_REQ_ERROR;
}
OutputDebugStringF("WEBRESPONSEMODIFIER: new data size: %d.\n",NewSize);
/*
* Check if the memory needed exceeds the limit allowed (the threshold).
* Note. In this sample, when the filter identifies such a case, it will try to
* change the response based on the partial data accumulated. After that,
* the filter will cease to receive notifications for the current request and
* will pass the rest of the response without change. This sample can be
* modified so that the filter will block the response if the threshold is
* exceeded.
*/
if (NewSize > ACCUMULATION_SIZE_LIMIT)
{
OutputDebugStringF("WEBRESPONSEMODIFIER: OnSendRawData, required data size (%d) exceeds accumulation limit (%d) - trying to insert header.\n",NewSize,ACCUMULATION_SIZE_LIMIT);
DWORD dwRetVal = OnEndOfRequest(pfc);
DisableNotifications( pfc, SF_NOTIFY_END_OF_REQUEST | SF_NOTIFY_SEND_RAW_DATA);
return dwRetVal;
}
/*
* If the buffer in pRawData is insufficient, increase the buffer size.
* Note. To achieve better performance, when additional memory allocation
* is needed, the filter allocates twice the amount of memory that is needed.
* This way, we reduce the number of allocation operations significantly and
* achieve better performance for the filter.
*/
if ( NewSize > pRawData->cbInBuffer)
{
/*
* Check for integer overflow
*/
pRawData->cbInBuffer = 2*NewSize;
if (pRawData->cbInBuffer < NewSize)
{
DisableNotifications(pfc,SF_NOTIFY_END_OF_REQUEST | SF_NOTIFY_SEND_RAW_DATA);
SetLastError( ERROR_ARITHMETIC_OVERFLOW );
return SF_STATUS_REQ_ERROR;
}
LPBYTE lpBuffer = (LPBYTE)pfc->AllocMem(pfc,pRawData->cbInBuffer, dwReserved);
if ( NULL == lpBuffer )
{
DisableNotifications(pfc,SF_NOTIFY_END_OF_REQUEST | SF_NOTIFY_SEND_RAW_DATA);
SetLastError( ERROR_NOT_ENOUGH_MEMORY );
return SF_STATUS_REQ_ERROR;
}
memcpy((LPVOID)lpBuffer, pRawData->pvInData, pRawData->cbInData);
pRawData->pvInData = (void *)lpBuffer;
}
/*
* Append InRawData ( new chunk ) to accumulation buffer.
*/
LPBYTE lpBuffer = (LPBYTE)pRawData->pvInData;
memcpy((LPVOID)(&lpBuffer[pRawData->cbInData]), pInRawData->pvInData, pInRawData->cbInData);
pRawData->cbInData = pRawData->cbInData + pInRawData->cbInData;
/*
* Mark current chunk as size 0 ( i.e. Don't send enything. )
*/
pInRawData->cbInData = 0;
return SF_STATUS_REQ_NEXT_NOTIFICATION;
}
/*
* OnEndOfRequest():
* During End Of Request Notification we:
* 1) Get the complete response from the filter Request Specific Data.
* 2) May manipulate that response.
* 3) Send that response.
*/
static DWORD OnEndOfRequest ( PHTTP_FILTER_CONTEXT pfc )
{
logLn("OnEndOfRequest" );
if ( NULL == pfc)
{
SetLastError( ERROR_INVALID_PARAMETER);
return SF_STATUS_REQ_ERROR;
}
/*
* Making the filter CARP-aware. We change the HTTP reply (adding the header) only
* if we are the first server. Note that if this is not the first server, all the data already transferred
* and there is nothing left to do.
*
*/
BOOL IsFirst;
DWORD dwErrorCode = IsFirstInCARP(pfc,&IsFirst) ;
if (dwErrorCode != ERROR_SUCCESS)
{
SetLastError(dwErrorCode);
return SF_STATUS_REQ_ERROR;
}
if (!IsFirst)
{
OutputDebugStringA("WEBRESPONSEMODIFIER: OnEndOfRequest, intra array server, do nothing.\n" );
return SF_STATUS_REQ_NEXT_NOTIFICATION;
}
OutputDebugStringA("WEBRESPONSEMODIFIER: First array server, insert header and send.\n" );
/*
* Block the following SEND_RESPONSE and END_OF_REQUEST notifications for
* this request. ( WriteClient() bellow will generate them.)
*
*/
DisableNotifications( pfc, SF_NOTIFY_END_OF_REQUEST | SF_NOTIFY_SEND_RAW_DATA);
/*
* OK all data was accumulated. Now extract from Request Data
* the response buffer. (which now contains the complete response).
*/
PHTTP_FILTER_RAW_DATA pRawData = (PHTTP_FILTER_RAW_DATA)pfc->pFilterContext;
if ( NULL == pRawData)
{
return SF_STATUS_REQ_NEXT_NOTIFICATION;
}
LPBYTE lpBuffer = (LPBYTE)pRawData->pvInData;
DWORD bytesToSend = pRawData->cbInData;
/*
* Empty Request data to make it ready for next response
* in case the connection is kept alive
*/
pfc->pFilterContext = NULL;
/*
* Add here code to modify the response. It is now the complete response.
* any decisions and changes that demand the complete Response in hand
* should be done here.
*/
if (!InsertOurHTMLHeader( pfc, &lpBuffer, &bytesToSend))
{
SetLastError( ERROR_NOT_ENOUGH_MEMORY );
return SF_STATUS_REQ_ERROR;
}
/*
* Send the complete response in one chunk.
*/
DWORD dwReserved = 0 ;
if ( pfc->WriteClient(pfc,(LPVOID)lpBuffer,&bytesToSend,dwReserved) )
{
return SF_STATUS_REQ_NEXT_NOTIFICATION;
}
else
{
return SF_STATUS_REQ_ERROR;
}
}
#define STRING_SIZE(str) (sizeof(str) - 1)
/*
*
* InsertOurHTMLHeader()
* Given the full response chunk, test if the response is in HTML format (has
* <HTML> in it). If so, insert an HTML header line into the response
* HTML. To do that we look at the input HTML as made of 3 chunks:
* Chunk1 from start till "Content-Length: ..." header ( if exist.)
* Chunk2 from "\r\n" after "Content-Length:" header until last character of
* "<HTML>".
* Chunk3 from first character after "<HTML>" till the end of the response.
* We then calculate the new Content-Length value by adding the length of the
* line we will insert to the original content length, and finally allocate a new
* buffer and paste into it the chunks in the following order:
* Chunk1, Updateded-Content-Length-Header, Chunk2, Line-we-wish-to-insert, chunk3.
*
*/
static bool InsertOurHTMLHeader ( PHTTP_FILTER_CONTEXT pfc, LPBYTE *ppBuffer, LPDWORD lpdwLen )
{
logLn("InsertOurHTMLHeader" );
LPSTR lpBuffer = (LPSTR)*ppBuffer;
DWORD dwLen = *lpdwLen;
bool bStatus = true;
if (lpBuffer == NULL || dwLen > INT_MAX)
{
bStatus = false;
goto ReturnBuffer;
}
if ( 0 < strnstr( lpBuffer, "<HTML>", dwLen) )
{
/*
*
* Find first chunk. If no Content-Length header then first chunk will be
* zero sized.
*
*/
int iStartChunk1 = 0;
int iEndChunk1 = strnstr( lpBuffer, CONTENT_LENGTH, dwLen);
if ( 0 >= iEndChunk1 )
iEndChunk1 = 0;
int iTmp = 0;
if ( 0 < iEndChunk1 )
{
/*
*
* If we are here then there is a Content-Length header, so we
* find the first "\r\n" after the the Content-Length header.
*
*/
iTmp = strnstr( lpBuffer + iEndChunk1, "\r\n" , dwLen - iEndChunk1);
if ( 0 >= iTmp )
goto ReturnBuffer;
}
/*
*
* Find the second chunk. It starts on the "\r\n" after the Content-Length
* Header, and ends after the first "<HTML>".
*
*/
int iStartChunk2 = iEndChunk1 + iTmp;
iTmp = strnstr( lpBuffer + iStartChunk2, "<HTML>", dwLen - iStartChunk2);
if ( 0 >= iTmp )
goto ReturnBuffer;
int iEndChunk2 = iStartChunk2 + iTmp + STRING_SIZE("<HTML>" );
/*
*
* The third and last chunk starts after the first "<HTML>" and goes till
* the end of the input response.
*
*/
int iStartChunk3 = iEndChunk2;
int iEndChunk3 = (int)dwLen;
char szContentLen[100];
if ( 0 < iEndChunk1 )
{
/*
*
* If there is Content-Length Header then find the Input Content Length,
* and add to it the length of the inserted line.
*
*/
DWORD dwContentLen =
dwfnContentLen( lpBuffer + iEndChunk1, iStartChunk2 - iEndChunk1) +
STRING_SIZE(LINE_TO_INSERT);
char *p = (char *) memcpy( szContentLen, CONTENT_LENGTH, STRING_SIZE(CONTENT_LENGTH)) +
STRING_SIZE(CONTENT_LENGTH);
*p++ = ' ';
_ultoa( dwContentLen, p, 10);
}
else
{
szContentLen[0] = 0;
}
/*
*
* Allocate a buffer for the new response.
*
*/
iTmp = iEndChunk1 - iStartChunk1 + strlen(szContentLen) + iEndChunk2 - iStartChunk2 +
STRING_SIZE(LINE_TO_INSERT) + iEndChunk3 - iStartChunk3 + 1;
DWORD dwReserved = 0;
LPSTR lpNewBuffer = (LPSTR)pfc->AllocMem(pfc,iTmp, dwReserved);
if ( !lpNewBuffer )
{
bStatus = false;
goto ReturnBuffer;
}
#define MEMCAT(lpTarget,lpSource,SourceLen,TargetLen) \
memcpy(lpTarget,lpSource,SourceLen); TargetLen += SourceLen;
DWORD dwNewLen = 0;
MEMCAT( lpNewBuffer + dwNewLen, lpBuffer + iStartChunk1, iEndChunk1 - iStartChunk1, dwNewLen);
MEMCAT( lpNewBuffer + dwNewLen, szContentLen, strlen(szContentLen), dwNewLen);
MEMCAT( lpNewBuffer + dwNewLen, lpBuffer + iStartChunk2, iEndChunk2 - iStartChunk2, dwNewLen);
MEMCAT( lpNewBuffer + dwNewLen, LINE_TO_INSERT, strlen(LINE_TO_INSERT), dwNewLen);
MEMCAT( lpNewBuffer + dwNewLen, lpBuffer + iStartChunk3, iEndChunk3 - iStartChunk3, dwNewLen);
/*
* We don't have to do that, but making it a string is good for debugging
*/
lpNewBuffer[dwNewLen] = 0;
lpBuffer = lpNewBuffer;
dwLen = dwNewLen;
}
ReturnBuffer:
*ppBuffer = (LPBYTE)lpBuffer;
*lpdwLen = dwLen;
return bStatus;
}
/*
*
* Extract the input Content-Length value.
*
* Note: This function receive a pointer to a string begins with "Content-Length:".
* It searches for the first occurrence of ":" and tries to parse the number followed by
* the ":" character. If the parsing fails, the function return 0.
*
*/
static ULONG dwfnContentLen(LPSTR ContentLenLine, int iLineLen)
{
.....
}
/*
*
* Utility function to notify that a filter is not to be called
* to a notification throughout the lifetime of the current Request.
*
*/
static void DisableNotifications ( PHTTP_FILTER_CONTEXT pfc, DWORD flags )
{
.....
}
/*
* strnstr()
* finds first appearance of strCharSet in string ignoring
* letters case.
*/
static int strnstr ( const char *string, const char *strCharSet , int n)
{
....
}
void OutputDebugStringF (const char* pchFormat, ...)
{
.....
}
/*
* IsFirstInCARP()
* Returns in IsFirst variable true if the current server is the first server and false otherwise.
*/
static DWORD IsFirstInCARP(PHTTP_FILTER_CONTEXT pfc, BOOL *pfIsFirst)
{
.....
} |
exemple WebResponseModifier (isa 2004 server SDK exemple) ne marche pas
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