SNFMulti/scanner.cpp

// scanner.cpp
//
// (C) 2002-2020 MicroNeil Research Corporation

// 20041117 _M - Included new improved Filter Chain module UrlDecode. This module
// scans each anchor or image tag for URL encoded characters and converts them to
// their singly byte counterparts. If a characters is converted then the decoded
// anchor tag is injected into the scan stream immediately after the source link.

// 20041114 _M - Included new Filter Chain module: Defunker. The Defunker re-emits
// the message to the scanner with all of the HTML and some coding removed. This
// allows HTML obfuscated patterns to be recognized by the scanning engine.

// 20040113 _M - New Reset() method used in ScanMessage() to keep things nice and
// tidy. Also, modified ScanText() to create a new evaluation matrix if it is
// needed, and to append to the existing one if there is one.

// 20030928 _M - Moving toward the peer-server architecture and V3. The message
// scanning component has been moved into it's own object called "scanner". From
// now on, a message, or text will be passed to the scanner and the scanner will
// return an evaulation matrix. As always, if something goes wrong it will throw.
// This allows us to separate the creation of a scanner, and it's use, from any
// other nifty logic. So, if I'm in a server mode, I can take my scanner and throw
// messages at it as often as I like. Each message I pump in one side comes out the
// other side as an evaluation matrix. This will work well for SMTP based engines
// as well as peer-server, or any other "service pipeline".
//
// Note that the scanner object has two ways it will accept data. One way is as a
// message via .ScanMessage(c_str). This method employs the filter chain system and
// expects to see an SMTP message. The second way is as plain text via .ScanText(c_str).
// This method is useful for "internal" purposes such as secondary scans used to
// locate compound rules or parameter scans used to pick up tuning data from the
// rulebase.

#include "scanner.hpp"

// Scanner::LoadRuleBase(RuleFileName, SecurityKey)

void Scanner::LoadRuleBase(string& RuleFileName, string& SecurityKey) {
  
  RuleBase.Load(RuleFileName);                     // Load the rulebase file.
  RuleBase.Validate(SecurityKey);                  // Validate the rulebase file.

}

// Scanner::ScanMessage(MessageBuffer)

EvaluationMatrix* Scanner::ScanMessage(unsigned char* MessageBuffer) {  // Scan with the filter chain.

   FilterChainCString IV(MessageBuffer);           // Set up the filter chain.
   FilterChainBase64 IW(&IV);                      // Include Base64 decoding.
   FilterChainQuotedPrintable IX(&IW);             // Include Quoted Printable decoding.
   FilterChainUrlDecode IY(&IX);                   // Include URL decoder.
   FilterChainDefunker IZ(&IY);                    // Include Defunking.

   // Reset and create a new EvaluationMatrix object to use for this scan.
   // ScanMessage is always called with a new message.

   Reset();                                        // Reset for the new message.
   
   myEvaluationMatrix =                            // Allocate a new evaluation matrix
     new EvaluationMatrix(&RuleBase);              // using the current rulebase.

   if(!myEvaluationMatrix)                         // If the allocation fails then
     throw BadMatrixAllocation();                  // throw an appropriate exception.

   try {
   
     // Message header rules in earlier versions occasionally failed because there was not
     // a new-line character in front of the very first header. So, now we insert one :-)
     // This allows all header rules to start off with a ^ indicating the start of the line.
   
     myEvaluationMatrix->EvaluateThis('\n');       // Insert a newline ahead of each message.
      
     // Scan each byte in the file up to the horizon or the end of the message.
     // If something goes wrong, an exception will be thrown.
    
     while(myEvaluationMatrix->CountOfCharacters < ScanHorizon)
       myEvaluationMatrix->EvaluateThis(IZ.GetByte());
   }

   catch(FilterChain::Empty) {                     // We're expecting this so it's ok, but
   }                                               // anything else will still be thrown!
   
   return myEvaluationMatrix;                      // Return our results.
}

// Scanner::ScanText(TextBuffer)

EvaluationMatrix* Scanner::ScanText(unsigned char* TextBuffer) { // Scan without the filter chain.

   // If needed, create a new EvaluationMatrix object to use for this scan.
   // If not needed, we'll add this scanning to the existing matrix.
   
   if(!myEvaluationMatrix) {
     myEvaluationMatrix =                          // Allocate a new evaluation matrix
       new EvaluationMatrix(&RuleBase);            // using the current rulebase.

     if(!myEvaluationMatrix)                       // If the allocation fails then
       throw BadMatrixAllocation();                // throw an appropriate exception.
   }

   int index=0;                                    // Set up an index at zero...

   while(                                                       // For as long as we're
     TextBuffer[index]!=0 &&                                    // not yet terminated and
     myEvaluationMatrix->CountOfCharacters < ScanHorizon)       // not at the horizon then
       myEvaluationMatrix->EvaluateThis(TextBuffer[index++]);   // scan this byte & move.

   return myEvaluationMatrix;                      // Return our results.

}