Factor out the function that reads a host specification from an input

file.

nmap.cc

@@ -417,9 +417,8 @@ static int ip_is_reserved(struct in_addr *ip)
 
 static char *grab_next_host_spec(FILE *inputfd, int argc, char **fakeargv) {
   static char host_spec[1024];
-  unsigned int host_spec_index;
-  int ch;
   struct in_addr ip;
+  size_t n;
 
   if (o.generate_random_ips) {
     do {
@@ -429,25 +428,12 @@ static char *grab_next_host_spec(FILE *inputfd, int argc, char **fakeargv) {
   } else if (!inputfd) {
     return( (optind < argc)?  fakeargv[optind++] : NULL);
   } else { 
-    host_spec_index = 0;
-    while((ch = getc(inputfd)) != EOF) {
-      if (ch == ' ' || ch == '\r' || ch == '\n' || ch == '\t' || ch == '\0') {
-	if (host_spec_index == 0) continue;
-	host_spec[host_spec_index] = '\0';
-	return host_spec;
-      } else if (ch == '#') {
-        /* Found a comment marker, ignore everything until EOL or EOF */
-        while ((ch = getc(inputfd)) != EOF && ch != '\n')
-          ;
-        if (ch != EOF)
-          ungetc(ch, inputfd);
-      } else if (host_spec_index < sizeof(host_spec) / sizeof(char) -1) {
-	host_spec[host_spec_index++] = (char) ch;
-      } else fatal("One of the host_specifications from your input file is too long (> %d chars)", (int) sizeof(host_spec));
-    }
-    host_spec[host_spec_index] = '\0';
+    n = read_host_from_file(inputfd, host_spec, sizeof(host_spec));
+    if (n == 0)
+      return NULL;
+    else if (n >= sizeof(host_spec))
+      fatal("One of the host_specifications from your input file is too long (>= %u chars)", (unsigned int) sizeof(host_spec));
   }
-  if (!*host_spec) return NULL;
   return host_spec;
 }
 

targets.cc

@@ -347,6 +347,47 @@ TargetGroup* load_exclude(FILE *fExclude, char *szExclude) {
   return excludelist;
 }
 
+static inline bool is_host_separator(int c) {
+  return c == ' ' || c == '\r' || c == '\n' || c == '\t' || c == '\0';
+}
+
+/* Read a single host specification from a file, as for -iL and --excludefile.
+   It returns the length of the string read; an overflow is indicated when the
+   return value is >= n. Returns 0 if there was no specification to be read. The
+   buffer is always null-terminated. */
+size_t read_host_from_file(FILE *fp, char *buf, size_t n)
+{
+  int ch;
+  size_t i;
+
+  i = 0;
+  ch = getc(fp);
+  while (is_host_separator(ch) || ch == '#') {
+    if (ch == '#') {
+      /* Skip comments to the end of the line. */
+      while ((ch = getc(fp)) != EOF && ch != '\n')
+        ;
+    } else {
+      ch = getc(fp);
+    }
+  }
+  while (ch != EOF && !(is_host_separator(ch) || ch == '#')) {
+    if (i < n)
+      buf[i] = ch;
+    i++;
+    ch = getc(fp);
+  }
+  if (ch != EOF)
+    ungetc(ch, fp);
+  if (i < n)
+    buf[i] = '\0';
+  else if (n > 0)
+    /* Null-terminate even though it was too long. */
+    buf[n - 1] = '\0';
+
+  return i;
+}
+
 /* A debug routine to dump some information to stdout.                  (mdmcl)
  * Invoked if debugging is set to 3 or higher
  * I had to make signigicant changes from wam's code. Although wam

targets.h

@@ -161,6 +161,8 @@ Target *nexthost(HostGroupState *hs, TargetGroup *exclude_group,
 		 struct scan_lists *ports, int pingtype);
 /* loads an exclude file into a excluded target list */
 TargetGroup* load_exclude(FILE *fExclude, char *szExclude);
+/* Read a single host specification from a file, as for -iL and --excludefile. */
+size_t read_host_from_file(FILE *fp, char *buf, size_t n);
 /* a debugging routine to dump an exclude list to stdout. */
 int dumpExclude(TargetGroup*exclude_group);
 /* Returns the last host obtained by nexthost.  It will be given again the next