/* greylisting without database for Exim 4.51 or newer.		*/
/* http://wiki.exim.org/DbLessGreyListingC			*/
/* version 0.4  December 13, 2019  Lena(at)lena.kiev.ua		*/
/* BSD license.							*/

/* times in seconds: */
#define defer_timeout 60*3  /* 3 min - how long to defer delivery */
#define allow_timeout 60*60*6  /* 6 hours - after passing the	      */
			       /* greylisting test, how long to allow */
			       /* (plus up to update_delay)	      */
#define update_delay 60*30  /* 30 min - minimal time between */
			    /* (a little expensive) updates  */

/* Changelog:							*/
/* 0.4 Dec13,2019 avoid using store_get() because number of its	*/
/*		  arguments changed at Exim 4.93		*/
/* 0.3 May28,2008 don't write to files, judge by age - faster;	*/
/*		  update twice a hour is enough			*/
/* 0.2 May26,2008 test for . and .. dirs by d_name instead	*/
/*		  of d_namlen for compatibility with Linux	*/
/* 0.1 May23,2008 first release					*/

#include "local_scan.h"
#include <string.h>
#include <dirent.h>
#include <utime.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/uio.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>

int grey(uschar **yield, int argc, uschar *argv[])
{
struct timeval curtime;
struct stat mystat;
DIR *dir_stream;
struct dirent *dp;
int i;
uschar *filename = expand_string(US "$spool_directory/grey"
  "1234567 10 234567 20 234567 30 234567 40 234567 50"
  "1234567 60 234567 70 234567 80 234567 90 23456 100"
  "123456 110 23456 120 23456 130 23456 140 23456 150"
  "123456 160 23456 170 23456 180 23456 190 23456 200"
  "123456 210 23456 220 23456 230 23456 240 23456 250"
  "123456");   /* 256 characters */
size_t dir_len = strlen((char *)filename)-256;

if (argc != 1) {
  *yield = US "bad number of arguments";
  return ERROR;
}
(void)gettimeofday(&curtime, NULL);
(void)strcpy(CS filename+dir_len, ".lastupdated");
if (stat(CCS filename, &mystat)) {   /* if the very first call */
  filename[dir_len] = '\0';
  if (stat(CCS filename, &mystat) && mkdir(CCS filename, 0750)) {
    *yield = US "cannot create 'grey' subdir in the spool directory";
    return ERROR;
  }
  (void)strcpy(CS filename+dir_len, ".lastupdated");
  (void)close(open(CCS filename, O_WRONLY | O_CREAT, 0644));
}
if (curtime.tv_sec-mystat.st_mtime > update_delay) {
  filename[dir_len] = '\0';
  dir_stream = opendir(CCS filename);
  filename[dir_len] = '/';
  while ((dp = readdir(dir_stream)) != NULL)
    if (*(dp->d_name) != '.') {   /* neither . nor .. directories */
      (void)strcpy(CS filename+dir_len+1, dp->d_name);
      (void)stat(CCS filename, &mystat);
      if (curtime.tv_sec-mystat.st_mtime > defer_timeout+allow_timeout)
	(void)unlink(CCS filename);
    }
  (void)closedir(dir_stream);
  (void)strcpy(CS filename+dir_len, ".lastupdated");
  (void)utime(CCS filename, NULL);
}
filename[dir_len] = '/';
(void)strncpy(CS filename+dir_len+1, CCS argv[0], 255);  /* filename is
						  truncated if too long */
for (i=dir_len+1; filename[i]; i++)
  if (filename[i] == '/')   /* inadmissible in filenames */
    filename[i] = ';';
if (stat(CCS filename, &mystat)) {   /* if file doesn't exist */
  (void)close(open(CCS filename, O_WRONLY | O_CREAT, 0644));
  *yield = US "1";   /* defer */
}
else if (curtime.tv_sec-mystat.st_mtime > defer_timeout)
  *yield = US "0";   /* allow */
else *yield = US "1";   /* defer */
return OK;
}