Bug#105364: installer allows user to insert underscores in the hostname

[Matt Kraai <kraai@debian.org>]

On Sun, Jul 15, 2001 at 07:20:59PM +0200, Eduard Bloch wrote:
> I was helping a new user to configure his woody installation, and was
> surprised by some "funny" messages from misc. config script. First, I
> could find the reason, then I realized that he used an _ underscore in
> the hostname. Normally this must not be used, but the installer allowed
> him to do so and "hostname" does not complain about "broken" strings, so
> the this may be reproduced by newbies, sooner or later. We should
> install something to check the entries, IMHO.

The following patch checks the input for RFC 608 compliance.  OK
to apply?

Matt

--- netconfig.c.orig	Sun Jul 15 13:32:46 2001
+++ netconfig.c	Sun Jul 15 13:38:45 2001
@@ -261,6 +261,8 @@
 int get_host()
 {
   char *def = NULL;
+  static const char *valid_hostname_chars =
+	  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-";
 
   for (;;) {
     if(host)
@@ -284,19 +286,20 @@
       return 255;
     }
 
-    if(strchr(host, ' ')) {
-      problemBox(_("The host name must be one word."), _("Problem"));
+    /* Check the hostname for RFC 608 compliance.  */
+    if (!isalpha(host[0])) {
+      problemBox(_("The host name must begin with a character from the alphabet."),
+		 _("Problem"));
+    } else if (host[strlen(host) - 1] == '-') {
+      problemBox(_("The host name must not end in a minus sign."), _("Problem"));
+    } else if (host[strspn(host, valid_hostname_chars)] != '\0') {
+      problemBox(_("The host name may only contain alphanumeric characters and the minus sign."),
+		 _("Problem"));
+    } else if (strlen(host) > 48) {
+      problemBox(_("The host name must contain 48 characters or less."),
+		 _("Problem"));
     } else {
-      if (strchr(host, '.')) {
-        problemBox(_("The host name must not contain dots."), _("Problem"));
-      } else {
-        if (isdigit(*host)) {
-          problemBox(_("The host name contains leading numerical character(s).\nNote that the RFC does not allow this."),
-                     _("Problem"));
-        } else {
-          break;
-        }
-      }
+      break;
     }
   }
   return 0;