Illegal character in hostname

[Gisle Vanem <gvanem () broadpark no>]

I found that nmap doesn't like IP-addresses that simply resolves to 
a dot '.'. E.g. 77.247.181.164 -> '.'.

nmap spews out a lot of these lines when encountering such a name:
 Illegal character(s) in hostname -- replacing with '*'
 Illegal character(s) in hostname -- replacing with '*'
 Illegal character(s) in hostname -- replacing with '*'
 Illegal character(s) in hostname -- replacing with '*'
 Illegal character(s) in hostname -- replacing with '*
...

I think the function encoded_name_to_normal() in nmap_dns.cc
doesn't handle such "joke hostname"; it's stepping out-of-bounds.
A patch that works for me:

@@ -601,6 +602,13 @@
// a normal decimal separated hostname.
// ASSUMES NAME LENGTH/VALIDITY HAS ALREADY BEEN VERIFIED
static int encoded_name_to_normal(unsigned char *buf, char *output, int outputsize){
+
+  if (!buf[0]) {
+    *output++ = '.';
+    *output++ = '\0';
+    return 0;
+  }
+
  while (buf[0]) {
    if (buf[0] >= outputsize-1) return -1;
    memcpy(output, buf+1, buf[0]);

--gv
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