SNFMilter/SNFMilter.hpp

// SNFMilter.hpp
// Copyright (C) 2007 ARM Research Labs, LLC.
// See www.armresearch.com for the copyright terms.
//
// This file defines the SNFMilter configuration data structures and interface.

#ifndef SNFMilterhpp_included
#define SNFMilterhpp_included

#include <signal.h>

#include <libmilter/mfapi.h>

#include <vector>
#include <string>
#include "MailHeaders.hpp"
#include "timing.hpp"
#include "threading.hpp"

using namespace std;

class snf_EngineHandler;                                                        // We must know that these exist.
class snf_RulebaseHandler;

// Connection types.

enum SNFMilterSocketType {
    TCPMilterSocket = 1,
    UNIXMilterSocket = 2,
    NOMilterSocket = 3
};

// SNFMilterAction - What we can do.

enum SNFMilterAction {                                                          // SNFMilter Actions
    Error = -1,                                                                 // Error result.
    Allow = 0,                                                                  // Process the message.
    Accept = 1,                                                                 // White-List the message.
    Retry = 2,                                                                  // Return Try Again (tmp fail)
    Reject = 3,                                                                 // Reject the message.
    Discard = 4,                                                                // Silently discard.
    Quarantine = 5,                                                             // Store in quarantine.
    NoAction = 6,                                                               // Take no action.
    NMilterActions
};

//
// Configuration.
//
const string AllowActionMnemonic = "0";
const string AcceptActionMnemonic = "1";
const string RetryActionMnemonic = "2";
const string RejectActionMnemonic = "3";
const string DiscardActionMnemonic = "4";
const string QuarantineActionMnemonic = "5";
const string NoActionMnemonic = "6";

const string TCPMilterSocketMnemonic = "1";
const string UNIXMilterSocketMnemonic = "2";

const int ResultCodesCount = 64;                                                // Number of valid result codes.
const int ConfigurationLifetime = 1000;                                         // Config life time in ms.
const bool PrependLocalReceivedHeader = true;                                   // True to prepend local received headers
                                                                                // to the buffer to scan.
const sfsistat FailSafeMilterResponse = SMFIS_CONTINUE;                         // Return value to libmilter
                                                                                // in case of error.
const string::size_type MailBufferReserveSize = 65536;                          // Maximum amount of email message to scan.
const string SMTPENDL = "\r\n";                                                 // SMTP endline.
const int ShutdownPeriods = 5;                                                  // Number of time periods to wait while
                                                                                // shutting down.
const int ShutdownWaitPeriod_ms = 1000;                                         // Time period duration for shutting down.

const string UnknownExceptionMessage = "Unknown exception occurred.";           // Logged when an unknown exception occurs.

const int ShutdownSignal = SIGTERM;                                             // Signal for shutdown.

//
// End of configuration.
//

// The SNFMilterEngine class provides up to date configuration data and
// a scanning engine for the milter. It is presumed that at one of these objects
// will be used in each message scan. They can be created, used, and destroyed,
// or for a more optimized approach they can be created, used, stored in a pool,
// and refreshed, and used again for a new scan. They should all be properly
// destroyed before runLibMilter() returns.
class SNFMilterEngine {                                                         // Milter config objec. One per scan.
private:

    Mutex ConfigMutex;                                                          // Configuration lock mutex.

    snf_RulebaseHandler* myRulebase;                                            // Where is my rulebase?
    snf_EngineHandler* myEngine;                                                // Where is my engine?

    // Configuration data.
    // IP scan actions

    SNFMilterAction WhiteAction;                                                // Action for White IP.
    SNFMilterAction CautionAction;                                              // Action for Caution IP.
    SNFMilterAction BlackAction;                                                // Action for Black IP.
    SNFMilterAction TruncateAction;                                             // Action for Truncate IP.
    SNFMilterAction NonZeroAction;                                              // Action for nonzero scans.

    // Message scan actions

    SNFMilterAction ResultActions[ResultCodesCount];                            // Array of possible scan actions.

    Timeout ConfigurationCheckTime;                                             // Timer for checking the configuration.
    string RunningConfiguration;                                                // The current running config string.
    void readConfiguration();                                                   // Parses the configuration.
    void checkConfiguration();                                                  // Reload the config if it is old.

public:
    SNFMilterEngine(snf_RulebaseHandler* R);                                    // Construct the configuration.
    ~SNFMilterEngine();                                                         // Destroy the configuration.

    void setResultAction(int Result, SNFMilterAction Action);                   // Set a result / action pair.

    SNFMilterAction scanIP(unsigned long int IP);                               // Scans an IP.
    SNFMilterAction scanMessage(const unsigned char* bfr, int length);          // Scans a message.
    string XHeaders();                                                          // Return X headers from last scan.
};

// The SNFMilterContext class maintains the context for a connection
// from the MTA.  There is one SNFMilterContext object for each
// connection from the MTA.  They can be created, used, and destroyed,
// or for a more optimized approach they can be created, used, stored
// in a pool, and refreshed, and used again for a new scan. They
// should all be properly destroyed before runLibMilter() returns.

class SNFMilterContext {                                                        // Milter connection context object.
public:

    // Object states.  The object transitions to the corresponding state
    // when a libmilter callback is invoked.  The object is in the
    // Pooled state when the object is not being used.
    enum SNFMilterState {
        Pooled,
        Connect,
        Helo,
        EnvFrom,
        EnvRcpt,
        Data,
        Header,
        EOH,
        Body,
        EOM,
        Close,
        NMilterStates
    } State;

    SNFMilterContext(snf_RulebaseHandler *);
    ~SNFMilterContext();

    sfsistat SkipReturn;                                                        // libmilter return value when further
                                                                                // callbacks of the same type are to be skipped.

    // Map the scan result to the libmilter return value.
    sfsistat
    smfisReturn(SNFMilterAction);

    // Scanning engine.
    SNFMilterEngine milterEngine;

    string getLocalReceivedHeader();

    // Connection data.
    struct SNFMilterConnectionData {
        string HostName;
        IP4Address HostIP;
        string HostHelo;

        // Clear the object.
        void clear() {
            HostName.clear();
            HostIP = (long unsigned )0;
            HostHelo.clear();
        }

    } ConnectionData;

    // Message buffer.
    struct SNFMilterMessageData {

        // Buffer to hold the message.
        string MessageBuffer;

        // Sender address.
        string SenderAddress;

        // Constructor reserves memory to hold the message.
        SNFMilterMessageData(string::size_type reserveSize) {
            MessageBuffer.reserve(reserveSize);
        }

        // Clear the object.
        void clear() {
            MessageBuffer.clear();
            SenderAddress.clear();
        }

    } MessageData;

};

class SNFMilterContextPool {                                                    // SNFMilter Pool Manager
private:
    Mutex ContextAllocationControl;                                             // Protects context allocation.
    vector<SNFMilterContext*> ContextPool;                                      // Contains all created contexts.
    ProductionQueue<SNFMilterContext*> AvailableContexts;                       // Contains all available contexts.

    snf_RulebaseHandler* myRulebase;                                            // Rulebase handler.

    // Connection info.
    SNFMilterSocketType MilterSocketType;
    string MilterSocketPath;
    string MilterSocketGroup;
    string MilterSocketIP;
    int MilterSocketPort;

public:
    SNFMilterContextPool(snf_RulebaseHandler* Rulebase);                        // Ctor needs a live rulebase handler.
    ~SNFMilterContextPool();                                                    // Dtor gracefully discards contexts.

    SNFMilterSocketType getSocketType();                                        // Named pipe or TCP socket specified
                                                                                // in the configuration.

    string getSocketPath();                                                     // Path of named pipe specified in
                                                                                // the configuration

    string getSocketGroup();                                                    // Group specified for named pipe
                                                                                // in the conofiguration.

    string getSocketIP();                                                       // IP (host) specified in the
                                                                                // configuration.

    int getSocketPort();                                                        // TCP port specified in the
                                                                                // configuration

    SNFMilterContext* grab();                                                   // Get an context to use.
    void drop(SNFMilterContext* E);                                             // Drop an context after use.
    bool allUnused();                                                           // Return true if no contexts are in use.
    void logThisError(string ContextName, int Code, string Text);               // Log an error message.
    void logThisInfo(string ContextName, int Code, string Text);                // Log an informational message.
    
};

// The runLibMilter function establishes the appropriate libmilter call backs and
// accepts calls from the MTA via libmilter until it is told to quit. When it
// is told to quit it gracefully closes down, reclaims any memory it allocated,
// and returns.

// The actual code for the runLibMilter() function call is found in SNFMilter.cpp.

void runLibMilter(SNFMilterContextPool* Contexts, bool DebugMode);               // Run the milter 'til it's done.

#endif