348 lines
10 KiB
Groff
348 lines
10 KiB
Groff
.\" Copyright 1998 Juniper Networks, Inc.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 2, 1998
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.Dt LIBTACPLUS 3
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.Os FreeBSD
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.Sh NAME
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.Nm libtacplus
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.Nd TACACS+ client library
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.Sh SYNOPSIS
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.Fd #include <taclib.h>
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.Ft int
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.Fn tac_add_server "struct tac_handle *h" "const char *host" "int port" "const char *secret" "int timeout" "int flags"
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.Ft void
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.Fn tac_close "struct tac_handle *h"
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.Ft int
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.Fn tac_config "struct tac_handle *h" "const char *path"
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.Ft int
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.Fn tac_create_authen "struct tac_handle *h" "int action" "int type" "int service"
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.Ft void *
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.Fn tac_get_data "struct tac_handle *h" "size_t *len"
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.Ft char *
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.Fn tac_get_msg "struct tac_handle *h"
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.Ft struct tac_handle *
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.Fn tac_open "void"
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.Ft int
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.Fn tac_send_authen "struct tac_handle *h"
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.Ft int
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.Fn tac_set_data "struct tac_handle *h" "const void *data" "size_t data_len"
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.Ft int
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.Fn tac_set_msg "struct tac_handle *h" "const char *msg"
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.Ft int
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.Fn tac_set_port "struct tac_handle *h" "const char *port"
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.Ft int
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.Fn tac_set_priv "struct tac_handle *h" "int priv"
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.Ft int
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.Fn tac_set_rem_addr "struct tac_handle *h" "const char *addr"
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.Ft int
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.Fn tac_set_user "struct tac_handle *h" "const char *user"
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.Ft const char *
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.Fn tac_strerror "struct tac_handle *h"
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.Sh DESCRIPTION
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The
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.Nm
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library implements the client side of the TACACS+ network access
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control protocol. TACACS+ allows clients to perform authentication,
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authorization, and accounting by means of network requests to remote
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servers. This library currently supports only the authentication
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portion of the protocol.
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.Sh INITIALIZATION
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To use the library, an application must first call
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.Fn tac_open
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to obtain a
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.Va struct tac_handle * ,
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which provides context for subsequent operations.
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Calls to
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.Fn tac_open
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always succeed unless insufficient virtual memory is available. If
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the necessary memory cannot be allocated,
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.Fn tac_open
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returns
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.Dv NULL .
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.Pp
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Before issuing any TACACS+ requests, the library must be made aware
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of the servers it can contact. The easiest way to configure the
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library is to call
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.Fn tac_config .
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.Fn tac_config
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causes the library to read a configuration file whose format is
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described in
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.Xr tacplus.conf 5 .
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The pathname of the configuration file is passed as the
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.Va file
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argument to
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.Fn tac_config .
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This argument may also be given as
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.Dv NULL ,
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in which case the standard configuration file
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.Pa /etc/tacplus.conf
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is used.
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.Fn tac_config
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returns 0 on success, or -1 if an error occurs.
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.Pp
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The library can also be configured programmatically by calls to
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.Fn tac_add_server .
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The
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.Va host
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parameter specifies the server host, either as a fully qualified
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domain name or as a dotted-quad IP address in text form.
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The
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.Va port
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parameter specifies the TCP port to contact on the server. If
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.Va port
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is given as 0, the library uses port 49, the standard TACACS+ port.
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The shared secret for the server host is passed to the
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.Va secret
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parameter. It may be any null-terminated string of bytes.
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The timeout for receiving replies from the server is passed to the
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.Va timeout
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parameter, in units of seconds.
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The
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.Va flags
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parameter is a bit mask of flags to specify various characteristics of
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the server. It may contain:
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.Pp
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.Bl -tag -width Fl
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.It Dv TAC_SRVR_SINGLE_CONNECT
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Causes the library to attempt to negotiate single connection mode
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when communicating with the server. In single connection mode, the
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original TCP connection is held open for multiple TACACS+ sessions.
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Older servers do not support this mode, and some of them become
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confused if the client attempts to negotiate it.
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.El
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.Pp
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.Fn tac_add_server
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returns 0 on success, or -1 if an error occurs.
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.Pp
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.Fn tac_add_server
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may be called multiple times, and it may be used together with
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.Fn tac_config .
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At most 10 servers may be specified.
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When multiple servers are given, they are tried in round-robin
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fashion until a working, accessible server is found. Once the
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library finds such a server, it continues to use it as long as it
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works.
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.Sh CREATING A TACACS+ AUTHENTICATION REQUEST
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To begin constructing a new authentication request, call
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.Fn tac_create_authen .
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The
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.Va action ,
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.Va type ,
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and
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.Va service
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arguments must be be set to appropriate values as defined in the
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TACACS+ protocol specification. The
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.Aq taclib.h
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header file contains symbolic constants for these values.
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.Pp
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After creating a request with
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.Fn tac_create_authen ,
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various optional parameters may be attached to it through calls to
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.Fn tac_set_data ,
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.Fn tac_set_port ,
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.Fn tac_set_priv ,
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.Fn tac_set_rem_addr ,
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and
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.Fn tac_set_user .
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The library creates its own copies of any strings provided to these
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functions, so that it is not necessary for the caller to preserve
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them. By default, each of these parameters is empty except for the
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privilege level, which defaults to
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.Ql USER
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privilege.
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.Sh SENDING THE AUTHENTICATION REQUEST AND RECEIVING THE RESPONSE
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After the TACACS+ request has been constructed, it is sent by means
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of
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.Fn tac_send_authen .
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This function connects to a server if not already connected, sends
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the request, and waits for a reply. On failure,
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.Fn tac_send_authen
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returns -1. Otherwise, it returns the TACACS+ status code and flags,
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packed into an integer value. The status can be extracted using the
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macro
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.Fn TAC_AUTHEN_STATUS .
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Possible status codes, defined in
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.Aq taclib.h ,
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include:
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.Pp
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.Bl -item -compact -offset indent
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.It
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.Dv TAC_AUTHEN_STATUS_PASS
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.It
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.Dv TAC_AUTHEN_STATUS_FAIL
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.It
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.Dv TAC_AUTHEN_STATUS_GETDATA
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.It
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.Dv TAC_AUTHEN_STATUS_GETUSER
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.It
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.Dv TAC_AUTHEN_STATUS_GETPASS
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.It
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.Dv TAC_AUTHEN_STATUS_RESTART
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.It
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.Dv TAC_AUTHEN_STATUS_ERROR
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.It
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.Dv TAC_AUTHEN_STATUS_FOLLOW
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.El
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.Pp
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The only flag is the no-echo flag, which can be tested using the
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macro
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.Fn TAC_AUTHEN_NOECHO .
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.Sh EXTRACTING INFORMATION FROM THE SERVER'S RESPONSE
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An authentication response packet from the server may contain a
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server message, a data string, or both. After a successful call to
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.Fn tac_send_authen ,
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this information may be retrieved from the response by calling
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.Fn tac_get_msg
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and
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.Fn tac_get_data .
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These functions return dynamically-allocated copies of the
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information from the packet. The caller is responsible for freeing
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the copies when it no longer needs them. The data returned from
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these functions is guaranteed to be terminated by a null byte.
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.Pp
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In the case of
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.Fn tac_get_data ,
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the
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.Va len
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argument points to a location into which the library will store the
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actual length of the received data, not including the null
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terminator. This argument may be given as
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.Dv NULL
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if the caller is not interested in the length.
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.Sh SENDING AUTHENTICATION CONTINUE PACKETS
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If
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.Fn tac_send_authen
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returns a value containing one of the status codes
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.Dv TAC_AUTHEN_STATUS_GETDATA ,
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.Dv TAC_AUTHEN_STATUS_GETUSER ,
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or
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.Dv TAC_AUTHEN_STATUS_GETPASS ,
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then the client must provide additional information to the server by
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means of a TACACS+ CONTINUE packet. To do so, the application must
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first set the packet's user message and/or data fields using
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.Fn tac_set_msg
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and
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.Fn tac_set_data .
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The client then sends the CONTINUE packet with
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.Fn tac_send_authen .
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N.B.,
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.Fn tac_create_authen
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should
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.Em not
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be called to construct a CONTINUE packet; it is used only for the
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initial authentication request.
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.Pp
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When it receives the CONTINUE packet, the server may again request
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more information by returning
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.Dv TAC_AUTHEN_STATUS_GETDATA ,
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.Dv TAC_AUTHEN_STATUS_GETUSER ,
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or
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.Dv TAC_AUTHEN_STATUS_GETPASS .
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The application should send further CONTINUEs until some other
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status is received from the server.
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.Sh OBTAINING ERROR MESSAGES
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Those functions which accept a
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.Va struct tac_handle *
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argument record an error message if they fail. The error message
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can be retrieved by calling
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.Fn tac_strerror .
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The message text is overwritten on each new error for the given
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.Va struct tac_handle * .
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Thus the message must be copied if it is to be preserved through
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subsequent library calls using the same handle.
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.Sh CLEANUP
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To free the resources used by the TACACS+ library, call
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.Fn tac_close .
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.Sh RETURN VALUES
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The following functions return a non-negative value on success. If
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they detect an error, they return -1 and record an error message
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which can be retrieved using
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.Fn tac_strerror .
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.Pp
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.Bl -item -offset indent -compact
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.It
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.Fn tac_add_server
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.It
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.Fn tac_config
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.It
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.Fn tac_create_authen
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.It
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.Fn tac_send_authen
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.It
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.Fn tac_set_data
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.It
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.Fn tac_set_msg
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.It
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.Fn tac_set_port
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.It
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.Fn tac_set_priv
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.It
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.Fn tac_set_rem_addr
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.It
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.Fn tac_set_user
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.El
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.Pp
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The following functions return a
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.No non- Ns Dv NULL
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pointer on success. If they are unable to allocate sufficient
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virtual memory, they return
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.Dv NULL
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and record an error message which can be retrieved using
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.Fn tac_strerror .
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.Pp
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.Bl -item -offset indent -compact
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.It
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.Fn tac_get_data
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.It
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.Fn tac_get_msg
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.El
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.Pp
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The following functions return a
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.No non- Ns Dv NULL
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pointer on success. If they are unable to allocate sufficient
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virtual memory, they return
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.Dv NULL ,
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without recording an error message.
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.Pp
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.Bl -item -offset indent -compact
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.It
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.Fn tac_open
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.El
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.Sh FILES
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.Pa /etc/tacplus.conf
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.Sh SEE ALSO
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.Xr tacplus.conf 5
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.Rs
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.%A D. Carrel and Lol Grant
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.%T The TACACS+ Protocol, Version 1.78
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.%O draft-grant-tacacs-02.txt (Internet Draft)
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.Re
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.Sh AUTHORS
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This software was written by
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.An John Polstra ,
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and donated to the FreeBSD project by Juniper Networks, Inc.
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