DESCRIPTION

This page is a work in progress.

tac_plus.conf contains configuration information for the tac_plus (tacacs+) daemon.

Each line contains either one of the directives documented below, white-space (blanks or tabs), or a comment.

Syntax enclosed in angle brackets (<>) below, refer to syntax documented elsewhere in this manual page.

TOP-LEVEL DIRECTIVES

#

Comments begin with a '#' character and extend to the end of the line. Comments may appear anywhere in the configuration file. To disable the special meaning of the '#' character, enclose the string containing it in double quotes ("#").

accounting

Only one configurable account parameter exists, the destination. All accounting records are either written to a file, syslog(3) at priority info, or both.

    accounting syslog;
    accounting file = <filename>

The default filename is /var/log/tac_plus.acct.

Since accounting requests occur (and are serviced) asynchronously, it is necessary to lock the accounting file so that two writers do not simultaneously write to it. The daemon uses fcntl(2) to lock the file. Although fcntl(2) locking over NFS is supported on some implementations, it is notoriously unreliable. Even if it is reliable, locking is likely to be extremely inefficient over NFS. The file is best located on a local file system.

acl

If compiled with acl support (--enable-acls), Access Control Lists can be defined to limit user's (or group's) login and/or enable access by daemon client IP address or hostname. An acl is referenced by its name, but must be defined before it can be referenced.

The acl is a series of permit or deny statements applied to the source IP address that the client used to connected to the daemon. The first <regex> that matches ends the evaluation and the result is the permit or deny on left. If no entry of the acl matches a given address, the result is an implicit deny.

    acl = <name> {
        <permission> = <regex>
        # deny 66.1.255/24, allow all else in 66.1/16
        deny = ^66\.1\.255\.
        permit = ^66\.1\.
        # implicit deny (ie: anything else)
    }

Briefly, if a company had all their loopback interfaces numbered from 66.1/16 (and thus all the tacacs clients are within 66.1/16), this acl might be used to dis-allow a user to login to (or enable on) any router whose loopback interface is in 66.1.255/24.

Note: because acls match against the daemon client's source IP address, the client should be configured to use a stable source such as a loopback interface. For example:

    ip tacacs-server source-interface loopback 0

default authentication

By default, authentication fails for users that do not appear in the configuration file. This overrides that behavior, thus permitting all authentication requests for such users.

    default authentication = file <filename>

Such users will be authentication via the <user> "DEFAULT".

Also see "user = DEFAULT", <default service>, and <default attribute>.

group

Analogous to a <user> and accepting the same syntax, a group provides a template of which a <user> or another group can be a member.

    group = <name> {
        <user_decl>
    }

A group may be recursive; that is a group may be a member of one other group (which may be a member of yet another group, and so on).

host

The host clause allows the configuration values noted below to be set for the client named by IP address. If tac_plus is started with the -L option, the name can also be name as resolved from the address with the gethostbyaddr(3) system call, which may be the FQDN (Fully Qualified Domain Name) if DNS is used. It is recommended that the IP address be used, since the resolver can be slow to timeout when network faults exist.

    host = <IP address> {
        key = <string>
        prompt = <string>
        enable = <password_spec>
    }

key specifics the packet encryption <key> for this host.

prompt specifies the username prompt that will be presented to a user.

key

Specifies an encryption key used to encrypt packets between the daemon and clients. This key must match the key configured on the clients.

key = <string>

The double quotes are only necessary if your key contains white-space, key-words, or special characters.

Note: encryption is highly recommended.

logging

Specifies the syslog(3) facility used. By default, logs are posted to the daemon facility.

    logging = <syslog_fac>

user

Define a user whose username is <name>.

    user = <name> {
        [ <default service> ]
        <user_attr>
        <svc>
    }

Note: seventeen special usernames exist: "DEFAULT", "$enable$", and "$enabN$" (where N is a privilege level number, normally in the range 0-15 on a Cisco). The "$enable$" user is for backward compatibility with previous versions of tacacs that is queried for privilege level 15 in addition to "$enab15$".

Also see the "priv-lvl" AV pair in the "AV Pairs" section below and the <default authentication> directive.

service

    user = <string> {
        [ default service = <permission> ]
        <user_attr>*
        <svc>*
    }

Also see the <default service> directive.

ADDITIONAL DIRECTIVE SYNTAX

attr_value_pair

Specify an AV (Attribute Value) pair. The "optional" keyword specifies that the AV pair is optional.

    [ optional ] <string> = <string>

Optional AV pairs are only sent to the client if it requests them. That is, the client must have included the given AV pair as a mandatory or optional pair in the request.

Some clients react incorrectly and negatively to receiving AV pairs that it did not solicit. Optional AV pairs should be ignored if they are not recognized or not supported in any given context.

Also see the "Configuring Authorization" and "AV Pairs" sections below.

cmd_auth

Specify command authorization.

For command authorization, the device should expand all abbreviated commands to their full names and compress adjacent white-space. For example, when the command "config t" is entered it will be expanded to "configure terminal".

    cmd = <string> {
        <cmd-match>
    }

cmd-match

Specify a command argument match.

    <permission> <regex>
    <permission> <regex>
        ...
    <permission>

The <regex> matches arguments of the command <string>. For example, to allow show diag but no other show commands:

    cmd = show {
        permit diag
        deny
    }

The end of the <cmd-match> has an implicit <permission> determined by <default service>. So, if the 'deny' had been omitted in the example above, the result of the authorization would be the value of <default service>.

Note: 'cmd-arg' should never appear in a configuration file. It is used internally by the daemon to construct a string which is then matched against the regular expressions which appear in a cmd clause in the configuration file.

Note: when a command has multiple arguments, they may be entered in many different permutations. It can be cumbersome to create regular expressions which will reliably authorize commands under these conditions. Administrators may wish to consider other methods of performing authorization.

default service

Specifies the default <permission> for service authorization.

    default service = <permission>

If omitted, the default is 'deny'.

Note: if used, <default service> must precede all other <svc> directives in a <user> clause.

default attribute

Specifies the default attribute <permission> for service authorization.

    default attribute = <permission>

Note: if used, <default attribute> must precede all other <svc_attr> directives in a <svc> clause.

des_string

Represents the one-way encryption of a password <string>. For example, a password might encrypt to the string 0AmUKnIT2gheo.

DES is the encryption historically used in Unix passwd(5) files. The crypt() function of the system's libcrypt is used to perform the encryption. The libcrypt of modern Unicies tend to support additional encryption algorithms and thus so would tac_plus. See the system's crypt manual page. To utilize another format, use the des keyword followed by the crypt in the format as described in the manpage. Typically it will have a "$1" prefix for MD5, "$2" for blowfish, and so on.

tac_pwd(8) is a utility supplied with tac_plus to assist in performing this encryption.

expires

Causes the <user>'s password to become invalid, starting on the specified expiration date.

    expires "May 23 2005"

A expiry warning message is sent to the user at login time, starting at 14 days before the expiration date.

If the <user>'s <login> <password_spec> is "file", the "expires" field of the configuration file is not consulted. Instead, the daemon looks at the the "shell" field of the password file entry for a valid expiration date.

If Solaris shadow password files are used for authentication, the "expires" field of the configuration file is not consulted. The expiry field from the shadow password file (if it exists) is used as the expiration date.

Case is not significant.

filename

A <string> specifying a file located in the filesystem.

While the daemon does change directories to / (root) when it starts, it is best to specify files by their FQPN (Fully Qualified Path Name). That is, a path that begins with /. For example, /var/log/file rather than the relative path var/log/file.

IP address

A <string> representing an IPv4 address in dotted-quad notation. For example:

    192.168.1.1

name

A <string> by which to refer to a configuration element, such as an <acl> or a <group>.

In general, a <name> must be defined before it can be referenced. For example, before a <user> can be a specified as a member of a <group>, the <group> has to be defined.

password_spec

There are five authentication mechanisms available: no password, cleartext, DES, PAM, a file in passwd(5) format, and skey.

    file <filename>
    cleartext <string>
    des <des_string>
    PAM
    skey
    nopassword

skey is an OTP (One Time Password) facility. The daemon must be built with skey (--enable-skey) support.

PAM (Pluggable Authentication Modules framework) is an authentication mechanism (and much more) capable of various types of authentication methods that are chosen by a configuration file. The PAM service name is the name of tac_plus executable, normally "tac_plus". PAM can be used only for login authentication, it is not implemented for enable authorization, and does not support OTP-like challenge system (ie: no additional prompting). The daemon must be built with PAM support, which is included by default if libpam is found.

Note: some cases of <password_spec> do not accept all of these mechanisms.

permission

Specifies that some match (for example a <service> or <cmd-match>) is to be allowed or denied.

    (permit | deny)

proto

A protocol is a subset of a service. Typical NAS supported values are atalk, bap, bridging, ccp, cdp, deccp, ip, ipx, lat, lcp, multilink, nbf, osicp, pad, rlogin, telnet, tn3270, vines, vpdn, xns, xremote, and unknown. Note that 'protocol' is actually an AV pair.

string

A series of characters, not including white-space or tac_plus key-words or special characters (ie: A-Za-z0-9_). To include any of those exceptions, enclose the string in double quotes ("this has whitespace").

svc

       XXX:

    <svc_auth> | <cmd_auth>

svc_auth

       XXX:
                service = ( arap | connection | exec | ppp protocol = <proto> |
                        shell | slip | system | tty-daemon | <client defined> )
                        {
                        [ <default attribute> ]

                        <attr_value_pair>*
                    }

The service AV pair is required.

syslog_fac

syslog(3) normally has 16 well-known channels, called facilities. syslogd(8) can be configured to direct each of these facilities to different files. The facilities are named: auth, cron, daemon, local[0-7], lpr, mail, news, syslog, user, and uucp.

user_attr

       XXX:

    user = bart {
        arap = cleartext "arap password"
        chap = cleartext "chap password"
        enable = <password_spec>
        pap  = cleartext "inbound pap password"
        opap = cleartext "outbound pap password"
        pap  = des <des_string>
        pap  = file <filename>
        pap  = PAM
        login = <password_spec>
        global = cleartext "outbound pap password"
    }

global specifies the authentication method for all services. login applies to normal logins (exec). arap, chap, pap, and opap (outbound PAP) service passwords may be defined separately.

NOTE: a global user password cannot be used for outbound PAP. This is because outbound PAP is implemented by sending the password from the daemon to the client. This is a security issue if the <key> is ever compromised.

enable specifies the enable password. The <password_spec> may only be of type cleartext, des, nopassword or file. If the daemon was compiled with per-user enable support (--enable-uenable), the host enable password will be evaluated iff the user does not have a personal enable password.

login name member  - can only be 1
default service = permit expires "May 23 2005"
    arap = cleartext "Fred's arap secret"
    chap = cleartext "Fred's chap secret" acl = <string> enableacl = <string>

In the case of recursion, the first match is returned. host enable is cleartext, des, nopassword or file only. arap chap expires May 23 2005 login member password         user_attr :=
                name = <string> |

                         login    = <password_spec> |
                         member   = <string> |
                         expires  = <string> |
                         arap     = cleartext <string> |
                         chap     = cleartext <string> |         #ifdef MSCHAP

                         ms-chap  = cleartext <string> |         #endif

                         pap      = cleartext <string> |
                         pap      = des <string> |
                         pap      = file <filename> |         #ifdef PAM

                         pap      = PAM |         #endif

                         opap     = cleartext <string> |
                         global   = cleartext <string> |
                         msg      = <string>
                         before authorization = <string> |
                         after authorization = <string>

CONFIGURING AUTHORIZATION

Authorizing a single session can result in multiple requests being sent to the daemon. For example, to authorize a dialin ppp user for IP, the following authorization requests would be made from the client:

1)

An initial authorization request to startup ppp from the exec, using the AV pairs service=ppp protocol=ip, will be made (Note: this initial request will be omitted if you are autoselecting ppp, since username will not be known yet).

This request is really done to find the address for dumb PPP (or SLIP) clients who cannot do address negotiation. Instead, they expect you to tell them what address to use before PPP starts up, via a text message.

2)

Next, an authorization request is made from the PPP subsystem to see if ppp's LCP layer is authorized. LCP parameters can be set at this time (e.g. callback). This request contains the AV pairs service=ppp protocol=lcp.

3)

Next an authorization request to startup ppp's IPCP layer is made using the AV pairs service=ppp protocol=ipcp. Any parameters returned by the daemon are cached.

4)

Next, during PPP's address negotiation phase, each time the remote peer requests a specific address, if that address isn't in the cache obtained in step 3, a new authorization request is made to see if the peers requested address is allowable. This step can be repeated multiple times until both sides agree on the remote peer's address or until the NAS (or client) decide they're never going to agree and they shut down PPP instead.

As you can see from the above, a program which plans to handle authorization must be able to handle a variety of requests and respond appropriately.

Authorization must be configured on both the client and the daemon to operate correctly. By default, the client will allow everything until configured to make authorization requests to the daemon.

With the daemon, the opposite is true; by default, the daemon will deny authorization of anything that isn't explicitly permitted.

Authorization allows the daemon to deny commands and services outright, or to modify commands and services on a per-user basis. Authorization on the daemon is divided into two separate parts: commands and services.

Authorizing:

commands

Exec commands are those commands which are typed at a Cisco exec prompt. When authorization is requested by the NAS, the entire command is sent to the daemon for authorization.

Command authorization is configured by specifying a list of <regex>s to match command arguments and an action which is a <permission>.

The following permits user Fred to run these commands:

    telnet 131.108.13.<any number> and
    telnet 128.<any number>.12.3 and
    show <anything>

All other commands are denied (by default).

    user=fred {
        cmd = telnet {
            # permit specified telnets
            permit 131\.108\.13\.[0-9]+
            permit 128\.[0-9]+\.12\.3
        }
        cmd = show {
            # permit show commands
            permit .*
        }
    }

The command and arguments which the user types are matched to the regular expressions specified in the configuration file (in order of appearance). The first successful match performs the associated action (<permission>). If there is no match, the command is denied by default.

Also see the <default authentication>, <default authorization>, <default attribute>, and <default service> directives.

AUTHORIZATION SCRIPTS

There are some limitations to the authorization that can be done using a configuration file. One solution is to arrange for the daemon to call user-supplied programs to control authorization. These "callouts" permit almost complete control over authorization, allowing you to read all the fields in the authorization packet sent by the client, including all its AV pairs, and to set authorization status and send a new set of AV pairs to the client in response.

Pre and post authorization programs are invoked by handing the command line to the Bourne shell. On most Unix systems, if the shell doesn't find the specified program it returns a status of one, which denies authorization. However, at least one Unix system (BSDI) returns a status code of 2 under these circumstances, which will permit authorization, and probably isn't what you intended.

Note: if your program hangs, the authorization will time out and return an error on the client, and you'll tie up a process slot on the daemon host, eventually running out of resources. There is no special code to detect this in the daemon.

The daemon communicates with pre and post (before and after) authorization programs over a pair of pipes. Programs using the standard i/o library will use full buffering in these circumstances. This should not be a problem, since AV pairs will be read until end of file (EOF) is seen on input, and output will be flushed when they exit.

Fields from the authorization packet can be supplied to the programs as arguments on the command line by using the appropriate dollar-sign variables in the configuration file. These fields are:

    user    -- user name
    name    -- client/NAS name
    ip      -- client/NAS IP
    port    -- client/NAS port
    address -- user address (remote user location)
    priv    -- privilege level number (0-15)
    method  -- a digit (1-4)
    type    -- digit (1-4)
    service -- digit (1-7)
    status  -- (pass, fail, error, unknown)

Unrecognized variables will appear as the string "unknown".

AV pairs from the authorization packet are fed to the program's standard input, one per line. The program is expected to process the AV pairs and write them to its standard output, one per line. What happens then is determined by the exit status of the program.

Note: when AV pairs containing spaces are listed in the configuration file, you need to enclose them in double quotes so that they are parsed correctly. AV pairs which are returned via standard output do not need delimiters and so should not be enclosed in double quotes.

Note: unless special arrangements are made, the daemon will run as root and hence the programs it invokes will also run as root, which is a security weakness. It is strongly recommended that FQPNs are used when specifying programs to execute, and that the daemon is compiled with unprivileged user and group IDs (--with-userid and --with-groupid) so that the daemon is not running as root when calling these programs,

Calling scripts

before authorization

Specify a per-user program to be called before any other authorization attempt is made by using a "before" clause.

    user = auth1 {
        before authorization "/path/pre_authorize $user $port $address"
    }

The AV pairs sent from the NAS will be supplied to the program standard input, one pair per line.

If the program returns a status of 0, authorization is unconditionally permitted. No further processing is done on this request and no AV pairs are returned to the client.

If the program returns a status of 1, authorization is unconditionally denied. No further processing is done on this request and no AV pairs are returned to the client.

If the program returns a status of 2, authorization is permitted. The program is expected to modify the AV pairs that it receives on its standard input (or to create entirely new ones) and to write them, one per line, to its standard output. The new AV pairs will be sent to the client with a status of AUTHOR_STATUS_PASS_REPL. No further processing takes place on this request.

If the program returns a status of 3, authorization is denied, but all attributes returned by the program via stdout are returned to the client. Also, whatever the program returns on stderr is placed into the server-msg field and returned to the client.

Any other status value returned from the program will cause an error to be returned to the client.

Note: a status of 2 is not acceptable when doing command authorization.

after authorization

Specify a per-user program to be called after authorization processing has been performed by the default, but before the authorization status and AV pairs have been transmitted to the client, by using a "after" clause.

    group = auth1 {
        after authorization "/path/post_authorize $user $port $status"
    }

The AV pairs resulting from the authorization algorithm that the daemon proposes to return to the NAS, are supplied to the program on standard input, one AV pair per line, so they can be modified if required.

The program is expected to process the AV pairs and write them to its standard output, one per line. What happens then is determined by the exit status of the program:

If the program returns a status of 0, authorization continues as if the program had never been called. Use this if (for example) to just send mail when an authorization occurs, without otherwise affecting normal authorization.

If the program returns a status of 1, authorization is unconditionally denied. No AV pairs are returned to the NAS. No further authorization processing occurs on this request.

If the program returns a status of 2, authorization is permitted and any AV pairs returned from the program on its standard output are sent to the NAS in place of any AV pairs that the daemon may have constructed.

Any other value will cause an error to be returned to the NAS by the daemon.

Current attributes are:

    "unknown"
    "service"
    "start_time"
    "port"
    "elapsed_time"
    "status"
    "priv_level"
    "cmd"
    "protocol"
    "cmd-arg"
    "bytes_in"
    "bytes_out"
    "paks_in"
    "paks_out"
    "address"
    "task_id"
    "callback-dialstring"
    "nocallback-verify"
    "callback-line"
    "callback-rotary"

Also see the "AV Pairs" section below.

AV PAIRS

AV (Attribute Value) pairs are text strings exchanged between the client and server of the form "attribute=value". The value may not appear in authorization request packets, indicating that it is null or unspecified. The equal sign ('=') means that this is a mandatory attribute. An asterisk ('*') may appear in place of the equal sign, indicating that it is an optional attribute which either the client or server may not understand or may ignore.

Optional attributes are preceded by the "optional" key-word in the configuration. For example:

    priv_lvl = 15
    optional allow-shell = true
    service=ppp
    protocol=ip
    addr*131.108.12.44

The following AV pairs specify which service is being authorized. They are typically accompanied by protocol AV pairs and other, additional pairs from the lists below.

service=arap

service=shell

for exec startup, and also for command authorizations. Requires:

    aaa authorization exec tacacs+

service=ppp

service=slip

service=system

not used.

service=raccess

Used for managing reverse telnet connections e.g.

    user = jim {
        login = cleartext lab
        service = raccess {
            port#1 = clientname1/tty2
            port#2 = clientname2/tty5
        }
    }

Requires IOS configuration

    aaa authorization reverse-access tacacs+

protocol=lcp

The lower layer of PPP, always brought up before IP, IPX, etc. is brought up.

protocol=ip

Used with service=ppp and service=slip to indicate which protocol layer is being authorized.

protocol=ipx

Used with service=ppp to indicate which protocol layer is being authorized.

protocol=atalk

with service=ppp or service=arap

protocol=vines

For vines over ppp.

protocol=ccp

Authorization of CCP. Compression Control Protocol). No other AV-pairs associated with this.

protocol=cdp

Authorization of CDP (Cisco Discovery Protocol). No other av-pairs associated with this.

protocol=multilink

Authorization of multilink PPP.

protocol=unknown

For undefined/unsupported conditions. Should not occur under normal circumstances.

Incomplete list of Cisco AV pairs. Other vendors may provide additional AV pairs specific to their products.

acl

For EXEC authorization this contains an access-class number (acl=2) which is applied to the line (tty) as the output access class. The specified access-list must be predefined.

ARAP, EXEC.

addr

The IP address the remote host should be assigned when a slip or PPP/IP connection is made. For example: addr=1.2.3.4

SLIP, PPP/IP.

autocmd

During exec startup, this specifies an autocommand, like the autocommand option to the username configuration command. For example: autocmd="telnet foo.com"

EXEC.

callback-line

The number of a TTY line to use for the callback. Used with service=arap, slip, ppp, or shell. Does not work for ISDN.

callback-rotary

The number of a rotary group (0 through 100) to use for the callback. Used with service=arap, slip, ppp, and shell. Does not work for ISDN.

cmd

If the value of cmd is NULL (cmd=), then this is an authorization request for starting an exec.

If cmd is non-null, this is a command authorization request. It contains the name of the command being authorized. For example: cmd=telnet

EXEC.

cmd-arg

During command authorization, the name of the command is given by an accompanying "cmd=" AV pair, and each command argument is represented by a cmd-arg AV pair e.g. cmd-arg=archie.sura.net

NOTE: 'cmd-arg' should never appear in a configuration file. It is used internally by the daemon to construct a string which is then matched against the regular expressions which appear in a cmd clause in the configuration file.

EXEC.

dns-servers

Identifies a primary or backup DNS server that can be requested by Microsoft PPP clients during IPCP negotiation. Used with service=ppp and protocol=ip.

gw-password

Specifies the password for the home gateway during L2F tunnel authentication. Used with service=ppp and protocol=vpdn.

idletime

Sets a value, in minutes, after which an IDLE session will be terminated. Does NOT work for PPP.

EXEC, 11.1 onward.

inacl

This AV pair contains an IP or IPX input access list number for slip or PPP (inacl=2). The access list itself must be pre-configured on the Cisco box. Per-user access lists do not work with ISDN interfaces unless you also configure a virtual interface. After 11.2(5.1)F, you can also use the name of a predefined named access list, instead of a number, for the value of this attribute.

Note: For IPX, inacl is only valid after 11.2(4)F.

PPP/IP/IPX.

inacl#<n>

This AV pair contains the definition of an input access list to be installed and applied to an interface for the duration of the current connection, e.g.

    inacl#1="permit ip any any precedence immediate"
    inacl#2="deny igrp 0.0.1.2 255.255.0.0 any"

Attributes are sorted numerically before they are applied. For IP, standard OR extended access list syntax may be used, but it is an error to mix the two within a given access-list.

For IPX, only extended access list syntax may be used.

PPP/IP/PPP/IPX, 11.2(4)F.

interface-config

Specifies user-specific AAA interface configuration information with Virtual Profiles. The information that follows the equal sign (=) can be any Cisco IOS interface configuration command.

ip-address

List of possible IP addresses, separated by spaces, that can be used for the end-point of a tunnel. Used with service=ppp and protocol=vpdn.

link-compression

Defines whether to turn on or turn off Stac compression over a PPP link. Valid values are:

        0       None
        1       Stac
        2       Stac Draft-9
        3       MS-Stac

load-threshold

This AV pair sets the load threshold at which an additional multilink link is added to the bundle (if load goes above) or deleted (if load goes below).

    service=ppp protocol=multilink {
        load-threshold=<n>
    }

The range of <n> is [1-255].

PPP/multilink - Multilink parameter, 11.3.

max-links

This AV pair restricts the number of multilink bundle links that a user can have.

    service=ppp protocol=multilink {
        max-links=<n>
    }

The range of <n> is [1-255].

PPP/multilink, 11.3.

nas-password

Specifies the password for the NAS during L2F tunnel authentication. Used with service=ppp and protocol=vpdn.

nocallback-verify

Indicates that no callback verification is required. The only valid value for this parameter is the digit one, i.e. nocallback-verify=1. Not valid for ISDN. ARAP/EXEC, 11.1 onward.

noescape

During exec startup, this specifies "noescape", like the noescape option to the username configuration command. Can have as its value the string "true" or "false". For example: noescape=true

EXEC.

nohangup

During exec startup, this specifies "nohangup", like the nohangup option to the username configuration command. Can have as its value the string "true" or "false". For example: nohangup=true

EXEC.

old-prompts

Allows the prompts in TACACS+ to appear identical to those of earlier systems (TACACS and Extended TACACS). This allows the upgrade from TACACS or Extended TACACS to TACACS+ to be transparent to users.

outacl

This AV pair contains an IP or IPX output access list number for SLIP. PPP/IP or PPP/IPX connections (outacl=4). The access list itself must be pre-configured. Per-user access lists do not work with ISDN interfaces unless you also configure a virtual interface. PPP/IPX is supported in 11.1 onward only. After 11.2(5.1)F, you can also use the name of a predefined named access list, as well as a number, for the value of this attribute.

PPP/IP, PPP/IPX.

outacl#<n>

This AV pair contains an output access list definition to be installed and applied to an interface for the duration of the current connection.

    outacl#1="permit ip any any precedence immediate"
    outacl#2="deny igrp 0.0.9.10 255.255.0.0 any"

Attributes are sorted numerically before they are applied. For IP, standard OR extended access list syntax may be used, but it is an error to mix the two within a given access-list.

For IPX, only extended access list syntax may be used.

PPP/IP/PPP/IPX, 11.2(4)F.

pool-def#

Defines IP address pools on the NAS. Used with service=ppp and protocol=ip.

pool-timeout

In conjunction with pool-def, defines IP address pools on the NAS. During IPCP address negotiation, if an IP pool name is specified for a user (see the addr-pool attribute), a check is made that the named pool is defined on the NAS. If it is, the pool is consulted for an IP address.

ppp-vj-slot-compression

Instructs the Cisco router not to use slot compression when sending VJ-compressed packets over a PPP link.

priv-lvl

Specifies the current privilege level for command authorizations, a number from zero to 15. For example: priv_lvl=5.

Note: in 10.3 this attribute was priv_lvl, i.e. it contained an underscore instead of a hyphen.

EXEC.

route

This AV pair specifies a temporary static route to be applied, which expunged once the connection terminates. The daemon side declaration is:

    service=ppp protocol=ip {
        route="<dst_addr> <mask> [ <gateway> ]"
    }

<dst_address>, <mask>, and <gateway> are <IP address>'s. If the gateway is omitted, the peer's address is assumed.

PPP/IP/SLIP, 11.1 onward.

route#<n>

Same as the "route" attribute, except that these are valid for IPX as well as IP, and they are numbered, allowing multiple routes to be applied. For example:

    route#1="3.0.0.0 255.0.0.0 1.2.3.4"
    route#2="4.0.0.0 255.0.0.0"

or, for IPX,

    route#1="4C000000 ff000000 30.12.3.4"
    route#2="5C000000 ff000000 30.12.3.5"

PPP/IP/IPX, 11.2(4)F.

routing

Equivalent to the /routing flag in slip and ppp commands. Can have as its value the string "true" or "false".

SLIP/PPP/IP.

rte-ftr-in#

Specifies an input access list definition to be installed and applied to routing updates on the current interface for the duration of the current connection. Used with service=ppp protocol=ip or protocol=ipx.

rte-ftr-out#

Output version of rte-ftr-in#.

sap#<n>

This AV pair specifies static SAPs (Service Advertising Protocol) to be installed for the duration of a connection. For example:

    sap#1="4 CE1-LAB 1234.0000.0000.0001 451 4"
    sap#2="5 CE3-LAB 2345.0000.0000.0001 452 5"

The syntax of static saps is the same as that used by the IOS "ipx sap" command. Used with service=ppp protocol=ipx.

PPP/IPX, 11.2(4)F.

sap-fltr-in#<n>

This AV pair specifies an input SAP filter access list definition to be installed and applied to the current interface, for the duration of the current connection.

Only Cisco extended access list syntax is legal (ipx input-sap-filter <number>). For example:

    sap-fltr-in#1="deny 6C01.0000.0000.0001"
    sap-fltr-in#2="permit -1"

Attributes are sorted numerically before being applied. Used with service=ppp protocol=ipx.

PPP/IPX, 11.2(4)F.

sap-fltr-out#<n>

This AV pair specifies an output sap filter access list definition to be installed and applied on the current interface, for the duration of the current connection.

Only Cisco extended access list syntax is legal (ipx output-sap-filter <number>), e.g

    sap-fltr-out#1="deny 6C01.0000.0000.0001"
    sap-fltr-out#2="permit -1"

Attributes are sorted numerically before being applied. Used with service=ppp protocol=ipx.

PPP/IPX, 11.2(4)F.

source-ip

This specifies a single ip address that will be used as the source of all VPDN packets generated as part of the VPDN tunnel (see the equivalent source-ip keyword in the IOS vpdn outgoing command).

PPP/VPDN, now deprecated, only existed in releases 11.2(1.4) thru 11.2(4.0.2).

timeout

Sets the time until an ARAP or exec session disconnects unconditionally (in minutes). For example: timeout=60

ARAP/EXEC, 11.0 onward.

tunnel-id

This AV pair specifies the username that will be used to authenticate the tunnel over which the individual user MID will be projected. This is analogous to the "NAS name" in the "vpdn outgoing" command.

PPP/VPDN, 11.2 onward.

zonelist

An Appletalk zonelist for arap (ARAP) equivalent to the line configuration command "arap zonelist". For example: zonelist=5.

AV pairs reserved for future use (this list may be out-dated):

    ppp-vj-slot-compression
    link-compression
    asyncmap
    x25-addresses (PPP/VPDN)
    frame-relay (PPP/VPDN)

Note: this AV pair list is NOT complete and not all AV pairs are supported by all vendors. See the vendor's documentation. When a client (or server) receives a mandatory AV pair that it does not understand, the authorization FAILS!

Also see the tac_plus user guide. Some of the callback, appletalk, IPX, VPDN, PPP routing, and address pool related AV pairs found in the user guide have been omitted.

ACCOUNTING AV PAIRS

bytes_in

The number of input bytes transferred during this connection.

bytes_out

The number of output bytes transferred during this connection.

cmd

The command the user executed.

data-rate

This AV pair has been renamed. See nas-rx-speed.

disc-cause

Specifies the reason a connection was taken off-line. The Disconnect-Cause attribute is sent in accounting stop records. This attribute also causes stop records to be generated without first generating start records if disconnected before authentication.

        1       User request
        2       Lost carrier
        3       Lost service
        4       Idle timeout
        5       Session timeout
        6       Admin reset
        7       Admin reboot
        8       Port error
        9       NAS error
        10      NAS request
        11      NAS reboot
        12      Port unneeded
        13      Port pre-empted
        14      Port suspended
        15      Service unavailable
        16      Callback
        17      User error
        18      Host request

disc-cause-ext

Extends the disc-cause attribute to support vendor-specific reasons that a connection was taken off-line.

        1000    Session timed out. This value applies to all session types.
        1002    Reason unknown.
        1004    Failure to authenticate calling-party number.
        1010    No carrier detected. This value applies to modem connections.
        1011    Loss of carrier. This value applies to modem connections.
        1012    Failure to detect modem result codes. This value applies to modem connections.
        1020    User terminates a session. This value applies to EXEC sessions.
        1021    Timeout waiting for user input. This value applies to all session types.
        1022    Disconnect due to exiting Telnet session. This value applies to EXEC sessions.
        1023    Could not switch to SLIP/PPP; the remote end has no IP address. This value applies to EXEC sessions.
        1024    Disconnect due to exiting raw TCP. This value applies to EXEC sessions.
        1025    Bad passwords. This value applies to EXEC sessions.
        1026    Raw TCP disabled. This value applies to EXEC sessions.
        1027    Control-C detected. This value applies to EXEC sessions.
        1028    EXEC process destroyed. This value applies to EXEC sessions.
        1040    PPP LCP negotiation timed out. This value applies to PPP sessions.
        1041    PPP LCP negotiation failed.
        1042    PPP PAP authentication failed.
        1043    PPP CHAP authentication failed.
        1044    PPP remote authentication failed.
        1045    PPP received a Terminate Request from remote end.
        1046    Upper layer requested that the session be closed.  This value applies to PPP sessions.
        1101    Session failed for security reasons. This value applies to all session types.
        1102    Session terminated due to callback. This value applies to all session types.
        1120    Call refused because the detected protocol is disabled. This value applies to all session types.

elapsed_time

The elapsed time in seconds for the action. Useful when the device does not keep real time.

event

Information included in the accounting packet that describes a state change in the router. Events described are accounting starting and accounting stopping.

mlp-links-max

Gives the count of links known to have been in a given multilink session at the time the accounting record is generated.

mlp-sess-id

Reports the identification number of the multilink bundle when the session closes. This attribute applies to sessions that are part of a multilink bundle. This attribute is sent in authentication-response packets.

nas-rx-speed

Specifies the average number of bits per second over the course of the connection's lifetime. This attribute is sent in accounting stop records.

nas-tx-speed

Reports the transmit speed negotiated by the two modems.

paks_in

The number of input packets transferred during this connection.

paks_out

The number of output packets transferred during this connection.

port

The port into which the user was logged.

pre-bytes-in

Records the number of input bytes before authentication. This attribute is sent in accounting stop records.

pre-bytes-out

Records the number of output bytes before authentication. This attribute is sent in accounting stop records.

pre-paks-in

Records the number of input packets before authentication. This attribute is sent in accounting stop records.

pre-paks-out

Records the number of output packets before authentication. This attribute is sent in accounting stop records as Pre-Output-Packets.

pre-session-time

Specifies the length of time, in seconds, from when a call first connects to when it completes authentication.

priv_level

The privilege level associated with the action.

protocol

The protocol associated with the action.

reason

Information included in the accounting packet that describes the event that caused a system change. Events described are system reload, system shutdown, or accounting reconfiguration (turned on or off).

service

The service the user used.

start_time

The time, in seconds since 12:00 a.m. January 1, 1970, that the action started. The clock must be configured to receive this information.

stop_time

The time, in seconds since 12:00 a.m. January 1, 1970, that the action stopped. The clock must be configured to receive this information.

task_id

Start and stop records for the same event must have matching (unique) task_id numbers.

timezone

The time zone abbreviation for all timestamps included in this packet.

xmit-rate

This AV pair has been renamed nas-tx-speed.

EXAMPLE CLIENT CONFIGURATION

Example Cisco configuration for tacacs+:

    aaa new-model
    aaa authentication login default tacacs+ local
    aaa authentication enable default tacacs+ enable
    aaa authorization exec default tacacs+
    aaa accounting exec default start-stop tacacs+
    !
    username root privilege 15 password 0 <root's password>
    !
    tacacs-server key <your key here>
    tacacs-server host <ip_address>
    ip tacacs source-interface loopback0
    !
    enable secret 0 <enable password>

Note that the aaa command syntax varies slightly between some versions of Cisco IOS and CatOS (Catalyst OS) also varies.

Example Juniper configuration for tacacs+:

    system {
        authentication-order [ password tacplus ];
        tacplus-server {
            <ip_address> secret <your key here>;
            <ip_address> {
                secret <your key here>;
                timeout 90;
            }
        }
    }

Both of these examples are brief. See the vendor's documentation for a description of what these configuration commands specify and for additional commands and arguments.

WARNING: If not properly configured, it may not be possible to login to the device!

EXAMPLE TAC_PLUS CONFIGURATION

key = "your key here"
accounting file = /var/log/tac.acct
# authentication users not appearing elsewhere via
# the file /etc/passwd
default authentication = file /etc/passwd
acl = dial_only {
    # All access routers are in 192.168/16, but except for
    # 192.168.0.1 all backbone router are in 198.168.0/24.
    # deny access to the backbone routers.
    permit = ^192\.168\.0\.1$
    deny   = ^192\.168\.0\.
    permit = ^192\.168\.
}
group = no_backbone {
    # permit an exec to start and permit all commands and
    # services by default
    default service = permit
    service = exec {
        # When an exec is started, its connection access list
        # will be 4. "acl" is quoted because it is a keyword.
        # It also has an autocmd
        "acl" = 4
        autocmd = "telnet duffhost"
    }
    # group will only be allowed to login on NASes
    acl = dial_only
}
group = admin {
    # group members who don't have their own login password will be
    # looked up in /etc/passwd
    login = file /etc/passwd
    # group members who have no expiry date set will use this one
    expires = "Jan 1 1997"
    # deny access to backbone routers
    acl = dial_only
}
user = DEFAULT {
    service = ppp protocol = ip {
        addr-pool=foobar
    }
}
user = homer {
    default service = permit
    member = no_backbone
}
user = fred {
    login = des mEX027bHtzTlQ
    name = "Fred Flintstone"
    member = admin
    expires = "May 23 2005"
    arap = cleartext "Fred's arap secret"
    chap = cleartext "Fred's chap secret"
    service = exec {
        # When Fred starts an exec, his connection access
        # list is 5
        "acl" = 5
        # We require this autocmd to be done at startup
        autocmd = "telnet foo"
    }
    # All commands except show system are denied for Fred
    cmd = show {
        # Fred can run the following show command
        permit system
        deny .*
    }
    service = ppp protocol = ip {
        # Fred can run ip over ppp only if he uses one
        # of the following mandatory addresses. If he
        # supplies no address, the first one here will
        # be mandated
        addr=131.108.12.11
        addr=131.108.12.12
        addr=131.108.12.13
        addr=131.108.12.14
        # Fred's mandatory input access list number is 101
        inacl=101
        # We will suggest an output access list of 102, but the NAS may
        # choose to ignore or override it
        optional outacl=102
    }
    service = slip {
        # Fred can run slip. When he does, he will have to use
        # these mandatory access lists
        inacl=101
        outacl=102
    }
}
user = wilma {
    # Wilma has no password of her own, but she's a group member so
    # she'll use the group password if there is one. Same for her
    # password expiry date
    member = admin
}

FILES

/etc/tac_plus.conf

Configuration file.

/var/log/tac_plus.acct

The default accounting file.

/var/log/tac_plus.log

The default log file.

AUTHOR

The tac_plus (tacacs+) developer's kit is a product of Cisco Systems. Made available at no cost and with no warranty of any kind. See the file COPYING and source files that came with the distribution for specifics.

HISTORY

This manual page was adapted from code inspection and Cisco's tac_plus user guide.