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HOSTS_ACCESS

Section: C Library Functions (3)
Index

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.alibrary. They implement a rule-based access control language withoptional shell commands that are executed when a rule fires.

request_init() initializes a structure with information about a clientrequest. request_set() updates an already initialized requeststructure. Both functions take a variable-length list of key-valuepairs and return their first argument. The argument lists areterminated with a zero key value. All string-valued arguments arecopied. 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. Thecontents 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 thehosts_access(5) manual page. When internal endpoint informationis available, host names and client user names are looked up on demand,using the request structure as a cache. hosts_access() returns zero ifaccess 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 notpass on enough information to support automated client usernamelookups). The client host address, client host name and usernamearguments should contain valid data or STRING_UNKNOWN. hosts_ctl()returns zero if access should be denied.

The allow_severity and deny_severity variables determinehow accepted and rejected requests may be logged. They must be providedby the caller and may be modified by rules in the access controltables.

DIAGNOSTICS

Problems are reported via the syslog daemon.

FILES

/etc/hosts.allow, /etc/hosts.deny, access control tables.

BUGS

hosts_access() uses the strtok() library function. This may interferewith other code that relies on strtok().

AUTHOR

Wietse Venema (wietseAATTwzv.win.tue.nl)Department of Mathematics and Computing ScienceEindhoven University of TechnologyDen Dolech 2, P.O. Box 513, 5600 MB Eindhoven, The Netherlands

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