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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
       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)

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