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.

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