Fix stack buffer overflow in var_subst() (dg_variables.c)

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Co-authored-by: welcor <357770+welcor@users.noreply.github.com>

src/comm.c

@@ -415,7 +415,7 @@ void copyover_recover()
 
   for (;;) {
     fOld = TRUE;
-    if (fscanf(fp, "%d %ld %511s %1023s %1023s\n", &desc, &pref, name, host, guiopt) != 5) {
+    if (fscanf(fp, "%d %ld %s %s %s\n", &desc, &pref, name, host, guiopt) != 5) {
       if(!feof(fp)) {
         if(ferror(fp))
           log("SYSERR: error reading copyover file %s: %s", COPYOVER_FILE, strerror(errno));

src/dg_variables.c

@@ -1636,6 +1636,13 @@ void var_subst(void *go, struct script_data *sc, trig_data *trig,
   int paren_count = 0;
   int dots = 0;
 
+  /* reject lines that would overflow our fixed-size buffers */
+  if (strnlen(line, MAX_INPUT_LENGTH) >= MAX_INPUT_LENGTH) {
+    script_log("Trigger VNum %d: variable substitution line too long, ignoring.", GET_TRIG_VNUM(trig));
+    *buf = '\0';
+    return;
+  }
+
   /* skip out if no %'s */
   if (!strchr(line, '%')) {
     strcpy(buf, line);