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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 rulebased
       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  structure. 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 struc-ture structure
              ture 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 user-name username
       name 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)