hosts_access, hosts_ctl, request_init, request_set - access control library
#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;
void fromhost(request)
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;
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. fromhost() must be called before hosts_access().
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.
Problems are reported via the syslog daemon.
hosts_access(5), format of the access control tables.
hosts_options(5), optional
extensions to the base language.
/etc/hosts.allow, /etc/hosts.deny, access control tables.
hosts_access() uses the strtok() library function. This may interfere with other
code that relies on strtok().
Wietse Venema ([email protected])
Department of Mathematics and Computing Science
Eindhoven University of Technology
Den Dolech 2, P.O. Box 513,
5600 MB Eindhoven, The Netherlands