Combined patch for simscan-1.4.1 (https://github.com/qmail/simscan/releases) by Roberto Puzzanghera
More info at https://notes.sagredo.eu/en/qmail-notes-185/simscan-38.html
v. 20230913

This patch puts together:

* jms patch to improve the debugging of simscan on qmail-smtpd log
  https://notes.sagredo.eu/files/qmail/patches/simscan/jms/simscan-1.4.0-debug.patch
  more info here https://qmail.jms1.net/simscan/

* A bug fix by Bob Greco where a received message with multiple 'local' recipients executes spamc
  as null user and not as the user extracted from the first local recipient.
  https://notes.sagredo.eu/en/qmail-notes-185/simscan-38.html#comment844

* The "attachments-size-limit" patch by Roberto Puzzanghera
  https://notes.sagredo.eu/files/qmail/patches/simscan/simscan-1.4.1_attachments-size-limit_v2.patch
  This patch let the administrator set the attachments' size limit in bytes by setting the
  /var/qmail/control/simsizelimit file.
  Furthermore, events where simscan is not activated are now logged at smtpd level (it was logged
  only when debug is active).
  Note: this patch is alternative to this one
  https://notes.sagredo.eu/files/qmail/patches/simscan/simscan-1.4.1_attachments-size-limit.patch
  which sets the limit at compilation time.

===================================================================================================

diff -ruN ../simscan-1.4.1_original/simscan.c simscan-1.4.1/simscan.c
--- ../simscan-1.4.1_original/simscan.c	2015-01-23 09:57:43.000000000 +0100
+++ simscan-1.4.1/simscan.c	2023-09-13 21:34:53.791256656 +0200
@@ -102,6 +102,7 @@
 int str_rstr(register char *h,register char *n);
 char *replace(char *string, char *oldpiece, char *newpiece);
 int DebugFlag = 0;
+int DebugFiles = 0;
 
 /* --stdout is required for reading virus names */
 char *viri_args[] = { "clamdscan", "--stdout", message_name, NULL };
@@ -171,6 +172,7 @@
 int InClamHeaders;
 int check_clam();
 int is_clam(char *clambuf);
+void log_clam(char *clambuf);
 #endif
 
 /* Attachment scanning globals */
@@ -253,6 +255,11 @@
  int i = 0;
  int gotrcpt = 0;
  int gotfrom = 0;
+ /* attachments-size-limit patch */
+ char ch, simsizelimit_file[300], buf[32];
+ FILE *simsizelimit;
+ int size_limit=250000, buflen=0, ibuf;
+ /* end attachments-size-limit patch */
 
   /* print out version information if requested */
   if ( argc > 1 && strcmp(argv[1],"-v" )==0 ) {
@@ -274,6 +281,11 @@
   if ( (tmpstr=getenv("SIMSCAN_DEBUG"))!=NULL ) {
     DebugFlag = atoi(tmpstr);
   }
+
+  /* Set the "leave temp files alone" flag */
+  if ( (tmpstr=getenv("SIMSCAN_DEBUG_FILES"))!=NULL ) {
+    DebugFiles = atoi(tmpstr);
+  }
   
 #ifdef ENABLE_ATTACH
   init_attach();
@@ -546,11 +558,33 @@
 #endif
 
 #ifdef ENABLE_SPAM
-if (msgsize >= 250000) {
-  if ( DebugFlag > 0 ) {
-    fprintf(stderr, "simscan: big file (%lu bytes); skipping SpamAssassin\n",
-      (unsigned long) msgsize);
+/* attachments-size-limit patch */
+// read control/simsizelimit file
+snprintf(simsizelimit_file, sizeof(simsizelimit_file), "%s/simsizelimit", CONTROLDIR);
+simsizelimit = fopen(simsizelimit_file, "r");
+if( simsizelimit != NULL ) {
+  while(1) {
+    ch = fgetc(simsizelimit);
+    if(ch==EOF || ch==' ' || ch=='\n' || ch=='\t' || ch=='\r') {
+      ibuf = atoi(buf);
+      // returns 0 if it's not an integer
+      if (ibuf > 0) size_limit = ibuf;
+      break;
+    }
+    else {
+      buf[buflen] = ch;
+      buflen++;
+    }
   }
+  fclose(simsizelimit);
+}
+if ( DebugFlag > 0 ) fprintf(stderr, "simscan: size limit is %d bytes\n", size_limit);
+if (msgsize >= size_limit) {
+//  if ( DebugFlag > 0 ) { // now logging also when debug is off
+    fprintf(stderr, "simscan: big file (%lu bytes); size limit is %d bytes; skipping SpamAssassin\n",
+      (unsigned long) msgsize, size_limit);
+//  }
+/* end attachments-size-limit patch */
 } else {
   /* re-open the file read only */
   if ( (fd = open(message_name, O_RDONLY)) == -1 ) {
@@ -828,10 +862,12 @@
   }
 
   /* remove the working files */
-  if ( remove_files(workdir) == -1 ) {
-    exit_clean(EXIT_400);
+  if ( DebugFiles < 2 ) {
+    if ( remove_files(workdir) == -1 ) {
+      exit_clean(EXIT_400);
+    }
   }
-  
+
   /* pass qmail-queue's exit status on */
   _exit(WEXITSTATUS(qstat));
 
@@ -984,6 +1020,7 @@
   InClamHeaders = 1;
   memset(buffer,0,sizeof(buffer));
   while((file_count=read(0,buffer,BUFFER_SIZE))>0) {
+    if ( DebugFlag > 2 ) log_clam(buffer) ;
     if ( InClamHeaders == 1 ) {
       is_clam(buffer);
     }
@@ -1010,6 +1047,35 @@
   return(-1);
 }
 
+void log_clam(char *clambuf)
+{
+	char *p ;
+	int needh = 1 ;
+
+	p = clambuf ;
+	while ( *p )
+	{
+		if ( *p != '\r' )
+		{
+			if ( needh )
+			{
+				fputs ( "simscan: clamdscan: " , stderr ) ;
+				needh = 0 ;
+			}
+
+			fputc ( *p , stderr ) ;
+
+			if ( *p == '\n' )
+				needh = 1 ;
+		}
+
+		p++ ;
+	}
+
+	if ( ! needh )
+		fputc ( '\n' , stderr ) ;
+}
+
 int is_clam(char *clambuf)
 {
  int i,j,k;
@@ -1315,7 +1381,7 @@
     spamc_args[i++] = "-u";
     spamc_args[i++] = spamuser;
 #ifdef ENABLE_SPAMC_USER
-  } else if ( MaxRcptTo==1 && i<MAX_SPAMC_ARGS-2 && strlen(spamuser) == 0) {
+  } else if ( MaxRcptTo>0 && i<MAX_SPAMC_ARGS-2 && strlen(spamuser) == 0) {
     spamc_args[i++] = "-u";
     spamc_args[i++] = RcptTo[0];
 #endif
@@ -1638,7 +1704,8 @@
  */
 void exit_clean( int error_code )
 {
-  remove_files(workdir);
+  if ( DebugFiles < 1 )
+    remove_files(workdir);
   if ( DebugFlag > 0 ) {
     fprintf(stderr, "simscan:[%d]: exit error code: %d\n", getppid(), error_code); 
   }