/*

Copyright (c) 2004, 2005 Carl Byington - 510 Software Group, released
under the GPL version 2 or any later version at your choice available at
http://www.fsf.org/licenses/gpl.txt

Based on a sample milter Copyright (c) 2000-2003 Sendmail, Inc. and its
suppliers.	Inspired by the DCC by Rhyolite Software

-p port  The port through which the MTA will connect to this milter.
-t sec	 The timeout value.
-c		 Check the config, and print a copy to stdout. Don't start the
		 milter or do anything with the socket.
-d		 increase debug level

*/


// from sendmail sample
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <sysexits.h>
#include <unistd.h>

// needed for socket io
#include <sys/ioctl.h>
#include <net/if.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <netdb.h>
#include <sys/socket.h>
#include <sys/un.h>

// needed for thread
#include <pthread.h>

// needed for std c++ collections
#include <set>
#include <map>
#include <list>

// for the dns resolver
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>

// misc stuff needed here
#include <ctype.h>
#include <syslog.h>
#include <pwd.h>
#include <sys/wait.h>	/* header for waitpid() and various macros */
#include <signal.h> 	/* header for signal functions */

#include "includes.h"

static char* smarchive_version="$Id$";


extern "C" {
	#include "libmilter/mfapi.h"
	sfsistat mlfi_connect(SMFICTX *ctx, char *hostname, _SOCK_ADDR *hostaddr);
	sfsistat mlfi_envfrom(SMFICTX *ctx, char **argv);
	sfsistat mlfi_envrcpt(SMFICTX *ctx, char **argv);
	sfsistat mlfi_eom(SMFICTX *ctx);
	sfsistat mlfi_abort(SMFICTX *ctx);
	sfsistat mlfi_close(SMFICTX *ctx);
	void sig_chld(int signo);
}

int  debug_syslog  = 0;
bool syslog_opened = false;
bool use_syslog    = true;	// false to printf
bool loader_run    = true;	// used to stop the config loader thread
CONFIG	 *config = NULL;	// protected by the config_mutex
int   generation = 0;		// protected by the config_mutex
const int maxlen = 1000;	// used for snprintf buffers

pthread_mutex_t  config_mutex;
pthread_mutex_t  syslog_mutex;


mlfiPriv::mlfiPriv() {
	pthread_mutex_lock(&config_mutex);
		pc = config;
		pc->reference_count++;
	pthread_mutex_unlock(&config_mutex);
	mailaddr	   = NULL;
	queueid 	   = NULL;
	processed_from = false;
}

mlfiPriv::~mlfiPriv() {
	pthread_mutex_lock(&config_mutex);
		pc->reference_count--;
	pthread_mutex_unlock(&config_mutex);
	reset(true);
}

void mlfiPriv::reset(bool final) {
	processed_from = false;
	if (mailaddr) free(mailaddr);
	if (queueid)  free(queueid);
	if (!final) {
		mailaddr = NULL;
		queueid  = NULL;
	}
}

#define MLFIPRIV	((struct mlfiPriv *) smfi_getpriv(ctx))


////////////////////////////////////////////////
// syslog a message
//
void my_syslog(mlfiPriv *priv, char *text) {
	char buf[maxlen];
	if (priv) {
		snprintf(buf, sizeof(buf), "%s: %s", priv->queueid, text);
		text = buf;
	}
	if (use_syslog) {
		pthread_mutex_lock(&syslog_mutex);
			if (!syslog_opened) {
				openlog("sm-archive", LOG_PID, LOG_MAIL);
				syslog_opened = true;
			}
			syslog(LOG_NOTICE, "%s", text);
		pthread_mutex_unlock(&syslog_mutex);
	}
	else {
		printf("%s \n", text);
	}
}

void my_syslog(char *text) {
	my_syslog(NULL, text);
}


////////////////////////////////////////////////
// this email address is passed in from sendmail, and will
// always be enclosed in <>. It may have mixed case, just
// as the mail client sent it. We dup the string and convert
// the duplicate to lower case.
//
char *to_lower_string(char *email);
char *to_lower_string(char *email) {
	int n = strlen(email)-2;
	if (n < 1) return strdup(email);
	char *key = strdup(email+1);
	key[n] = '\0';
	for (int i=0; i<n; i++) key[i] = tolower(key[i]);
	return key;
}


////////////////////////////////////////////////
// start of sendmail milter interfaces
//
sfsistat mlfi_connect(SMFICTX *ctx, char *hostname, _SOCK_ADDR *hostaddr)
{
	// allocate some private memory
	mlfiPriv *priv = new mlfiPriv;
	// save the private data
	smfi_setpriv(ctx, (void*)priv);
	// continue processing
	return SMFIS_CONTINUE;
}

sfsistat mlfi_envfrom(SMFICTX *ctx, char **from)
{
	mlfiPriv &priv = *MLFIPRIV;
	priv.mailaddr  = to_lower_string(from[0]);
	return SMFIS_CONTINUE;
}

sfsistat mlfi_envrcpt(SMFICTX *ctx, char **rcpt)
{
	mlfiPriv &priv = *MLFIPRIV;
	CONFIG &dc = *priv.pc;
	if (!priv.queueid) priv.queueid = strdup(smfi_getsymval(ctx, "i"));
	char *rcptaddr	= to_lower_string(rcpt[0]);
	if (debug_syslog > 1) {
		char msg[maxlen];
		snprintf(msg, sizeof(msg), "from <%s> to <%s>", priv.mailaddr, rcptaddr);
		my_syslog(&priv, msg);
	}
	char *target = dc.find_to(rcptaddr);
	if (target) smfi_addrcpt(ctx, target);
	free(rcptaddr);
	if (!priv.processed_from) {
		target = dc.find_from(priv.mailaddr);
		if (target) smfi_addrcpt(ctx, target);
		priv.processed_from = true;
	}
	return SMFIS_CONTINUE;
}

sfsistat mlfi_eom(SMFICTX *ctx)
{
	// reset for a new message on the same connection
	mlfi_abort(ctx);
	return SMFIS_CONTINUE;
}

sfsistat mlfi_abort(SMFICTX *ctx)
{
	mlfiPriv &priv = *MLFIPRIV;
	priv.reset();
	return SMFIS_CONTINUE;
}

sfsistat mlfi_close(SMFICTX *ctx)
{
	mlfiPriv *priv = MLFIPRIV;
	if (!priv) return SMFIS_CONTINUE;
	delete priv;
	smfi_setpriv(ctx, NULL);
	return SMFIS_CONTINUE;
}

struct smfiDesc smfilter =
{
	"SM-ARCHIVE",       // filter name
	SMFI_VERSION,		// version code -- do not change
	SMFIF_ADDRCPT,		// flags
	mlfi_connect,		// connection info filter
	NULL,				// SMTP HELO command filter
	mlfi_envfrom,		// envelope sender filter
	mlfi_envrcpt,		// envelope recipient filter
	NULL,				// header filter
	NULL,				// end of header
	NULL,				// body block filter
	mlfi_eom,			// end of message
	mlfi_abort, 		// message aborted
	mlfi_close, 		// connection cleanup
};


////////////////////////////////////////////////
//	reload the config
//
CONFIG* new_conf();
CONFIG* new_conf() {
	CONFIG *newc = new CONFIG;
	pthread_mutex_lock(&config_mutex);
		newc->generation = generation++;
	pthread_mutex_unlock(&config_mutex);
	if (debug_syslog) {
		char buf[maxlen];
		snprintf(buf, sizeof(buf), "loading configuration generation %d", newc->generation);
		my_syslog(buf);
	}
	if (load_conf(*newc, "sm-archive.conf")) {
		newc->load_time = time(NULL);
		return newc;
	}
	delete newc;
	return NULL;
}


////////////////////////////////////////////////
//	thread to watch the old config files for changes
//	and reload when needed. we also cleanup old
//	configs whose reference count has gone to zero.
//
void* config_loader(void *arg);
void* config_loader(void *arg) {
	typedef set<CONFIG *> configp_set;
	configp_set old_configs;
	while (loader_run) {
		sleep(180);  // look for modifications every 3 minutes
		if (!loader_run) break;
		CONFIG &dc = *config;
		time_t then = dc.load_time;
		struct stat st;
		bool reload = false;
		for (string_set::iterator i=dc.config_files.begin(); i!=dc.config_files.end(); i++) {
			char *fn = *i;
			if (stat(fn, &st))			 reload = true; // file disappeared
			else if (st.st_mtime > then) reload = true; // file modified
			if (reload) break;
		}
		if (reload) {
			CONFIG *newc = new_conf();
			if (newc) {
				// replace the global config pointer
				pthread_mutex_lock(&config_mutex);
					CONFIG *old = config;
					config = newc;
				pthread_mutex_unlock(&config_mutex);
				if (old) old_configs.insert(old);
			}
			else {
				// failed to load new config
				my_syslog("failed to load new configuration");
				system("echo 'failed to load new sm-archive configuration from /etc/sm-archive' | mail -s 'error in /etc/sm-archive configuration' root");
				// update the load time on the current config to prevent complaining every 3 minutes
				dc.load_time = time(NULL);
			}
		}
		// now look for old configs with zero ref counts
		for (configp_set::iterator i=old_configs.begin(); i!=old_configs.end(); ) {
			CONFIG *old = *i;
			if (!old->reference_count) {
				if (debug_syslog) {
					char buf[maxlen];
					snprintf(buf, sizeof(buf), "freeing memory for old configuration generation %d", old->generation);
					my_syslog(buf);
				}
				delete old; // destructor does all the work
				old_configs.erase(i++);
			}
			else i++;
		}
	}
	return NULL;
}


void usage(char *prog);
void usage(char *prog)
{
	fprintf(stderr, "Usage: %s  [-d [level]] [-c] -p sm-sock-addr [-t timeout]\n", prog);
	fprintf(stderr, "where sm-sock-addr is for the connection to sendmail\n");
	fprintf(stderr, "    and should be one of\n");
	fprintf(stderr, "        inet:port@ip-address\n");
	fprintf(stderr, "        local:local-domain-socket-file-name\n");
	fprintf(stderr, "-c will load and dump the config to stdout\n");
	fprintf(stderr, "-d will set the syslog message level, currently 0 to 3\n");
}



void setup_socket(char *sock);
void setup_socket(char *sock) {
	unlink(sock);
	//	sockaddr_un addr;
	//	memset(&addr, '\0', sizeof addr);
	//	addr.sun_family = AF_UNIX;
	//	strncpy(addr.sun_path, sock, sizeof(addr.sun_path)-1);
	//	int s = socket(AF_UNIX, SOCK_STREAM, 0);
	//	bind(s, (sockaddr*)&addr, sizeof(addr));
	//	close(s);
}


/*
 * The signal handler function -- only gets called when a SIGCHLD
 * is received, ie when a child terminates
 */
void sig_chld(int signo)
{
	int status;
	/* Wait for any child without blocking */
	while (waitpid(-1, &status, WNOHANG) > 0) {
		// ignore child exit status, we only do this to cleanup zombies
	}
}


int main(int argc, char**argv)
{
	token_init();
	bool check	 = false;
	bool setconn = false;
	int c;
	const char *args = "p:t:d:ch";
	extern char *optarg;

	// Process command line options
	while ((c = getopt(argc, argv, args)) != -1) {
		switch (c) {
			case 'p':
				if (optarg == NULL || *optarg == '\0') {
					fprintf(stderr, "Illegal sendmail socket: %s\n", optarg);
					exit(EX_USAGE);
				}
				if (smfi_setconn(optarg) == MI_FAILURE) {
					fprintf(stderr, "smfi_setconn failed\n");
					exit(EX_SOFTWARE);
				}
					 if (strncasecmp(optarg, "unix:", 5) == 0)  setup_socket(optarg + 5);
				else if (strncasecmp(optarg, "local:", 6) == 0) setup_socket(optarg + 6);
				setconn = true;
				break;

			case 't':
				if (optarg == NULL || *optarg == '\0') {
					fprintf(stderr, "Illegal timeout: %s\n", optarg);
					exit(EX_USAGE);
				}
				if (smfi_settimeout(atoi(optarg)) == MI_FAILURE) {
					fprintf(stderr, "smfi_settimeout failed\n");
					exit(EX_SOFTWARE);
				}
				break;

			case 'c':
				check = true;
				break;

			case 'd':
				if (optarg == NULL || *optarg == '\0') debug_syslog = 1;
				else								   debug_syslog = atoi(optarg);
				break;

			case 'h':
			default:
				usage(argv[0]);
				exit(EX_USAGE);
		}
	}

	if (check) {
		use_syslog	 = false;
		debug_syslog = 10;
		CONFIG *conf = new_conf();
		if (conf) {
			conf->dump();
			delete conf;
			return 0;
		}
		else {
			return 1;	// config failed to load
		}
	}

	if (!setconn) {
		fprintf(stderr, "%s: Missing required -p argument\n", argv[0]);
		usage(argv[0]);
		exit(EX_USAGE);
	}

	if (smfi_register(smfilter) == MI_FAILURE) {
		fprintf(stderr, "smfi_register failed\n");
		exit(EX_UNAVAILABLE);
	}

	// switch to background mode
	if (daemon(1,0) < 0) {
		fprintf(stderr, "daemon() call failed\n");
		exit(EX_UNAVAILABLE);
	}

	// write the pid
	const char *pidpath = "/var/run/sm-archive.pid";
	unlink(pidpath);
	FILE *f = fopen(pidpath, "w");
	if (f) {
#ifdef linux
		// from a comment in the DCC source code:
		// Linux threads are broken.  Signals given the
		// original process are delivered to only the
		// thread that happens to have that PID.  The
		// sendmail libmilter thread that needs to hear
		// SIGINT and other signals does not, and that breaks
		// scripts that need to stop milters.
		// However, signaling the process group works.
		fprintf(f, "-%d\n", (u_int)getpgrp());
#else
		fprintf(f, "%d\n", (u_int)getpid());
#endif
		fclose(f);
	}

	// initialize the thread sync objects
	pthread_mutex_init(&config_mutex, 0);
	pthread_mutex_init(&syslog_mutex, 0);

	// drop root privs
	struct passwd *pw = getpwnam("sm-archive");
	if (pw) {
		if (setgid(pw->pw_gid) == -1) {
			my_syslog("failed to switch to group sm-archive");
		}
		if (setuid(pw->pw_uid) == -1) {
			my_syslog("failed to switch to user sm-archive");
		}
	}

	// load the initial config
	config = new_conf();
	if (!config) {
		my_syslog("failed to load initial configuration, quitting");
		exit(1);
	}

	// only create threads after the fork() in daemon
	pthread_t tid;
	if (pthread_create(&tid, 0, config_loader, 0))
		my_syslog("failed to create config loader thread");
	if (pthread_detach(tid))
		my_syslog("failed to detach config loader thread");

	time_t starting = time(NULL);
	int rc = smfi_main();
	if ((rc != MI_SUCCESS) && (time(NULL) > starting+5*60)) {
		my_syslog("trying to restart after smfi_main()");
		loader_run = false; 	// eventually the config loader thread will terminate
		execvp(argv[0], argv);
	}
	exit((rc == MI_SUCCESS) ? 0 : EX_UNAVAILABLE);
}