hosts_access.3 (2010 09)

h
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;
extern int rfc931_timeout;
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 here are a part of the libwrap.sl/libwrap.so
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
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