/* greylisting without database for Exim 4.51 or newer.		*/
/* http://wiki.exim.org/DbLessGreyListingC			*/
/* version 0.3  May 28, 2008  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:							*/
/* 0.3 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 *dir = expand_string(US "$spool_directory/grey");
size_t dir_len = strlen(dir);
uschar *filename = US store_get(dir_len+257);

if (argc != 1) {
  *yield = US "bad number of arguments";
  return ERROR;
}
(void)gettimeofday(&curtime, NULL);
(void)memcpy(filename, dir, dir_len);
(void)strcpy(CS filename+dir_len, ".lastupdated");
if (stat(CCS filename, &mystat)) {   /* if the very first call */
  if (stat(CCS dir, &mystat) && mkdir(CCS dir, 0750)) {
    *yield = US "cannot create 'grey' subdir in the spool directory";
    return ERROR;
  }
  (void)close(open(CCS filename, O_WRONLY | O_CREAT, 0644));
}
if (curtime.tv_sec-mystat.st_mtime > update_delay) {
  filename[dir_len] = '/';
  dir_stream = opendir(CCS dir);
  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[dir_len+256] = '\0';   /* 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;
}