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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  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 argu-
       ments 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 call-
       er 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)

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