Updated: 2022/Sep/29

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HOSTS_ACCESS(3)            Library Functions Manual            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
       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 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.

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)