hosts_access

HOSTS_ACCESS(3)						      HOSTS_ACCESS(3)



NAME
       hosts_access,  hosts_ctl,  request_init,	 request_set - access control
       library

SYNOPSIS
       #include "tcpd.h"

       extern int allow_severity;
       extern int deny_severity;

       struct request_info *request_init(request, key, value, ..., 0)
       struct request_info *request;

       struct request_info *request_set(request, key, value, ..., 0)
       struct request_info *request;

       int hosts_access(request)
       struct request_info *request;

       int hosts_ctl(daemon, client_name, client_addr, client_user)
       char *daemon;
       char *client_name;
       char *client_addr;
       char *client_user;

DESCRIPTION
       The routines described in this document	are  part  of  the  libwrap.a
       library.	 They  implement  a  rule-based	 access control language with
       optional shell commands that are executed when a rule fires.

       request_init() initializes a structure with information about a client
       request.	 request_set()	updates an already initialized request struc-
       ture. Both functions take a variable-length list	 of  key-value	pairs
       and  return  their  first argument.  The argument lists are terminated
       with a zero key value. All string-valued	 arguments  are	 copied.  The
       expected keys (and corresponding value types) are:

       RQ_FILE (int)
	      The file descriptor associated with the request.

       RQ_CLIENT_NAME (char *)
	      The client host name.

       RQ_CLIENT_ADDR (char *)
	      A printable representation of the client network address.

       RQ_CLIENT_SIN (struct sockaddr_in *)
	      An  internal  representation  of the client network address and
	      port.  The contents of the structure are not copied.

       RQ_SERVER_NAME (char *)
	      The hostname associated with the server endpoint address.

       RQ_SERVER_ADDR (char *)
	      A printable representation of the server endpoint address.

       RQ_SERVER_SIN (struct sockaddr_in *)
	      An internal representation of the server endpoint	 address  and
	      port.  The contents of the structure are not copied.

       RQ_DAEMON (char *)
	      The name of the daemon process running on the server host.

       RQ_USER (char *)
	      The  name of the user on whose behalf the client host makes the
	      request.

       hosts_access() consults the access control  tables  described  in  the
       hosts_access(5)	manual	page.	When internal endpoint information is
       available, host names and client user names are looked up  on  demand,
       using  the  request structure as a cache.  hosts_access() returns zero
       if access should be denied.

       hosts_ctl() is a wrapper around the request_init() and  hosts_access()
       routines	 with a perhaps more convenient interface (though it does not
       pass on	enough	information  to	 support  automated  client  username
       lookups).   The	client	host  address,	client host name and username
       arguments should contain valid data  or	STRING_UNKNOWN.	  hosts_ctl()
       returns zero if access should be denied.

       The  allow_severity and deny_severity variables determine how accepted
       and rejected requests may be logged. They  must	be  provided  by  the
       caller and may be modified by rules in the access control tables.

DIAGNOSTICS
       Problems are reported via the syslog daemon.

SEE ALSO
       hosts_access(5),	   format    of	   the	  access    control   tables.
       hosts_options(5), optional extensions to the base language.

FILES
       /etc/hosts.allow, /etc/hosts.deny, access control tables.

BUGS
       hosts_access() uses the strtok() library function. This may  interfere
       with other code that relies on strtok().

AUTHOR
       Wietse Venema (wietse@wzv.win.tue.nl)
       Department of Mathematics and Computing Science
       Eindhoven University of Technology
       Den Dolech 2, P.O. Box 513,
       5600 MB Eindhoven, The Netherlands




							      HOSTS_ACCESS(3)