/*
 * uvscan local_scan() function for Exim (requires at least Exim v4.14)
 * known to work with VirusScan for Linux v4.16.0 (Scan engine v4.2.40)
 * but should be OK with other platforms
 *
 * this file is free software (license=GNU GPLv2) and comes with no
 * guarantees--if it breaks, you get to keep the pieces (maybe not the mail)!
 *
 * by (ie patches / flames to): mb/local_scan@dcs.qmul.ac.uk, 2003-05-02
 * (original version on 2002-05-25)
 */

#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <string.h>
#include "local_scan.h"

/*
 * remember to set LOCAL_SCAN_HAS_OPTIONS=yes in Local/Makefile
 * otherwise you get stuck with the compile-time defaults
 */

static uschar *uvscan_binary = US"/usr/local/uvscan/uvscan";
static uschar *data_directory = US"/usr/local/uvscan";

optionlist local_scan_options[] = { /* alphabetical order */
	{ "data_directory", opt_stringptr, &data_directory },
	{ "uvscan_binary", opt_stringptr, &uvscan_binary }
};

int local_scan_options_count = sizeof(local_scan_options)/sizeof(optionlist);

/* log headers in rejectlog or not? */

//#define VIRUS_IN_MAIL LOCAL_SCAN_REJECT
#define VIRUS_IN_MAIL LOCAL_SCAN_REJECT_NOLOGHDR

/*
 * buffer is used both for file copying and catching uvscan's output
 * BUFSIZE = 1024 should always be fine
 */

#define BUFSIZE 1024

/* some number which uvscan doesn't return */
#define MAGIC 123

/*
 * some macros to make the main function more obvious
 * NB bailing out might leave tempfiles hanging around
 * (and open fds, but no need to be worried about that)
 */

#define BAIL(btext) { log_write(0, LOG_MAIN, "UVSCAN ERROR: "btext); \
	*return_text = "local scanning problem: please try again later"; \
	return LOCAL_SCAN_TEMPREJECT; }

#define DEBUG(dtext) if ((debug_selector & D_local_scan) != 0) \
		{ debug_printf(dtext); sleep(1); }
	/* sleep useful for running exim -d */

#define RESULT(rtext) header_add(32, \
	"X-uvscan-result: "rtext" (%s)\n", message_id);

#define FREEZE(ftext) { header_add(32, \
	"X-uvscan-warning: frozen for manual attention (%s)\n", message_id); \
	RESULT(ftext); *return_text = ftext; return LOCAL_SCAN_ACCEPT_FREEZE; }

/* OK, enough waffle. On with the show! */

int local_scan(int fd, uschar **return_text)
{
	char tf[] = "/tmp/local_scan.XXXXXX"; /* should this be tunable? */
	int tmpfd, bytesin, bytesout, pid, status, pipe_fd[2];
	fd_set fds; 
	static uschar buffer[BUFSIZE];

	DEBUG("entered uvscan local_scan() function");

	/*
	 * I set majordomo to resend using -oMr lsmtp
         * (and yes, I know majordomo isn't actually using SMTP..)
	 * no point in scanning these beasties twice
	 */

	if(!strcmp(received_protocol, "lsmtp"))
		return LOCAL_SCAN_ACCEPT;

	/* create a file to copy the data into */

	if ((tmpfd = mkstemp(tf)) == -1)
		BAIL("mkstemp failed");

	DEBUG("made tmp file");

	/* copy said file BUFSIZE at a time */

	while ((bytesin = read(fd, buffer, BUFSIZE)) > 0) {
		bytesout = write(tmpfd, buffer, bytesin);
		if (bytesout < 1)
			BAIL("writing to tmp file");
	}
	if (bytesin < 0)
		BAIL("reading from spool file");

	close(tmpfd);

	if(pipe(pipe_fd) == -1)
		BAIL("making pipe");

	/* fork and scan */	

	if((pid = fork()) == -1)
		BAIL("couldn't fork");

	if(pid == 0) {
		close(1); /* close stdout */
		if(dup2(pipe_fd[1],1) == -1) /* duplicate write as stdout */
			BAIL("dup2 (stdout) failed");
		if(fcntl(1,F_SETFD,0) == -1) /* fd to NOT close on exec() */
			BAIL("fcntl (stdout) failed");

		execl(uvscan_binary, uvscan_binary, "--mime", "--secure",
			"-d", data_directory, tf, NULL);
		DEBUG("execl failed");
		_exit(MAGIC);
	}

	if(waitpid(pid, &status, 0) < 1)
		BAIL("couldn't wait for child");
	
	DEBUG("about to unlink");

	if(unlink(tf) == -1)
		FREEZE("couldn't unlink tmp file");

	DEBUG("unlinked :)");

	/*
	 * choose what to do based on the return code of uvscan
	 * RESULT() or FREEZE() according to personal taste
	 */

	if(WIFEXITED(status) != 0)
		switch(WEXITSTATUS(status)) {
		case 0: RESULT("clean"); break;
		case 2: RESULT("driver integrity check failed"); break;
		case 6: FREEZE("general problem occurred"); break;
		case 8: RESULT("could not find a driver"); break;
		case 12: FREEZE("failed to clean file"); break;
		case 13:
			// RESULT("virus detected"); /* were we to accept */
			DEBUG("about to read from uvscan process");
			FD_ZERO(&fds);
			FD_SET(pipe_fd[0], &fds);
			if(select(pipe_fd[0]+1, &fds, NULL, NULL, NULL)) {
				/* last NULL above means wait forever! */
				DEBUG("select returned non-zero");
				if((bytesin = read(pipe_fd[0], buffer,
						BUFSIZE - 1)) > 0) {
					buffer[bytesin] = (uschar)0;
					*return_text = buffer + 22;
					/* 22 was empirically found ;) */
					return VIRUS_IN_MAIL;
				} else
					BAIL("reading from uvscan process");
			}
			break;
		case 15: FREEZE("self-check failed"); break;
		case 19: FREEZE("virus detected and cleaned"); break;
		case MAGIC: RESULT("couldn't run uvscan"); break;
		default:
			RESULT("unknown error code");
			header_add(32, "X-uvscan-status: %d\n",
				WEXITSTATUS(status));
			break;
		}
	else
		BAIL("child exited abnormally");

	return LOCAL_SCAN_ACCEPT;
}