When using shadow in YP, the password field contains a ``x''
or ``##login'', not the encryped password. In this case,
ypchsh/ypchfn will wrongly write the magic shadow word (x or ##login)
to password field. Thus, user can not login until root reset his/her
password.

This patch preserves old password by re-encrypt it.
The correctness of the old password is checked before sending new
pw struct.

--- yppasswd.c.orig	Sun Mar 11 19:10:01 2001
+++ yppasswd.c	Fri Aug 15 16:55:54 2003
@@ -663,6 +663,8 @@
       char gecos[1024], *sp, new_gecos[1024];
       char name[254], location[254], office[254], phone[254];
       char oname[254], olocation[254], ooffice[254], ophone[254];
+      char salt[2];
+      time_t tm;
 
       printf (_("\nChanging full name for %s on %s.\n"
 	     "To accept the default, simply press return. To enter an empty\n"
@@ -691,11 +693,19 @@
 	*sp = '\0';
 
       yppwd.newpw.pw_gecos = strdup (new_gecos);
+
+      time (&tm);
+      salt[0] = bin_to_ascii (tm & 0x3f);
+      salt[1] = bin_to_ascii ((tm >> 6) & 0x3f);
+
+      yppwd.newpw.pw_passwd = strdup (crypt (yppwd.oldpass, salt));
     }
 
   if (l_flag)
     {
       char new_shell[PATH_MAX];
+      char salt[2];
+      time_t tm;
 
       printf (_("\nChanging login shell for %s on %s.\n"
 		"To accept the default, simply press return. To use the\n"
@@ -707,6 +717,12 @@
 	return 1;
 
       yppwd.newpw.pw_shell = strdup (new_shell);
+
+      time (&tm);
+      salt[0] = bin_to_ascii (tm & 0x3f);
+      salt[1] = bin_to_ascii ((tm >> 6) & 0x3f);
+
+      yppwd.newpw.pw_passwd = strdup (crypt (yppwd.oldpass, salt));
     }
 
   clnt = clnt_create (master, YPPASSWDPROG, YPPASSWDVERS, "udp");