NAME

FSM::Basic - Finite state machine using HASH as state definitions

VERSION

Version 0.21

SYNOPSIS

A small finite state machine using a HASH data as description of the states Mainly used to create fake bash or fake telnet server in the purpose to mimic some CLI device interface (like SWITCH or ROUTER interface) Perhaps a little code snippet. The HASH is easily using a JSON file

    use FSM::Basic;

    my $fsm = FSM::Basic->new( \%states, 'accept' );
    my $final = 0;
    my $out;
    foreach my $in ( @ins )
    {
        ( $final, $out ) = $fsm->run( $in );
        say $out;
        last if $final;
   }

SUBROUTINES/METHODS

new

my $fsm = FSM::Basic->new( \%states, 'accept' );

Create the FSM with the HASH ref as first paramter and the initial state as second parameter

The HASH is like this:

 my %states = (
    'accept' => {
        'expect' => {
            'default' => {
                'final'    => 0,
                'matching' => 'prompt'
            }
        },
        'not_matching'           => 'accept',
        'not_matching0'          => 'close',
        'not_matching_info_last' => '% Bad passwords
',
        'output' => 'Password: ',
        'repeat' => 2
    },

    'close'  => {'final' => 1},
    'prompt' => {
        'expect' => {
            'not_matching' => 'prompt',
            'exit'         => {
                'matching'    => 'close',
                'final' => 0
            },
            'meminfo'     => {'do' => 'do { local( @ARGV, $/ ) = "/proc/meminfo" ; <> }'},
            'h(elp)?|\\?' => {
                'output' => 'exit
meminfo
mem_usage
User> '
            },
            'mem_usage' => {'do' => 'my ( $tot,$avail) = (split /\\n/ ,do { local( @ARGV, $/ ) = "/proc/meminfo" ; <> })[0,2];$tot =~ s/\\D*//g; $avail =~ s/\\D*//g; sprintf "%0.2f%%\\n",(100*($tot-$avail)/$tot); '},
        },
        'not_matching_info' => '% Unknown command or computer name, or unable to find computer address',
        'output'            => 'User> '
    }
);

The keys are the states name. "expect" contain a sub HASH where the keys are word or REGEX expected as input

In this hash, you have :
executable code:

"do" for perl code

"exec" for system code,

and 4 dedicated commands:

"cat" just reading the file content provided in parameter).

"catRAND" chose randomly one of the files provided in parameter space separated

"catWRAND" chose randomly (weighted) one of the files provided in parameter space separatedwith a : to separate the weight

e.g. 'catWRAND' => './t/test_cat.txt:1 ./t/test_cat1.txt:50', in this case the file ./t/test_cat1.txt get 50 more chance to be selected than file ./t/test_cat.txt

"catSEQ" read sequentialy the next files provided in parameter space separated if "catSEQ_idx" is defined, that file is used to keep the state. Otherwise , the state file is named used all the files name from "catSEQ" concatenated with a final '.tate'. All spaces are replaced by an underscore

    It is possible to use a regex to allow generics commands

    e.g. "h(elp)?|\\?": { "output": "default\nexit\ntimeoutA\n__PROMPT__" }

    This json section match for 'h' 'help' or '?'

    In the regex, the group capture could be used in the command parameter as a substitution

    1st group is substituted by __1__

    2nd group is substituted by __2__

    .. e.g. for a ping

    "ping (.*)" => {"exec" => "ping -c 3 __1__"},

    The __1__ is substitued by the first parameter in the expected command

    If you run the command "ping 127.0.0.1" the exec run the command "ping -c 3 127.0.0.1"

    Other example:

          "cat /tmp/test/((\\w)(\\d))": {
            "cat": "/tmp/test/__3__"
          }
          

    If you call with "cat /tmp/test/a1 the cat read the file /tmp/test/1" (without the 'a' because the group 3 is matching a single digit after a single character

"matching" to define the state when the input match the "expect" value
"final" to return a flag
"not_matching" the state if the input is not matching the "expect" value (if missing stay in the same state)
"repeat" a number of trial before the state goes to "not_matching0"
"not_matching0" the state when the number of failled matching number is reached
"not_matching_info_last" info returned as second value when the failled matching number is reached
"output" the info returned as second value

It is perfectly possible to add extra tag not used by FSM::Basic for generic purpose. Check examples/fake_bash_ssh1.* Take a look at timout and timer usage In this example if destination IP from the SSH connection is available, the file IP.json is used as definition (with fallback to fake_bash1.pl)

run

my ( $final, $out ) = $fsm->run( $in );

Run the FSM with the input and return the expected output and an extra flag

EXAMPLE

    use strict;
    use feature qw( say );
    use FSM::Basic;
    use JSON;
    use Term::ReadLine;

        my %states = (
        'accept' => {
            'expect' => {
                'default' => {
                    'final'    => 0,
                    'matching' => 'prompt'
                }
            },
            'not_matching'           => 'accept',
            'not_matching0'          => 'close',
            'not_matching_info_last' => '% Bad passwords
    ',
            'output' => 'Password: ',
            'repeat' => 2
        },

        'close'  => {'final' => 1},
        'prompt' => {
            'expect' => {
                'not_matching' => 'prompt',
                'exit'         => {
                    'matching' => 'close',
                    'final'    => 0
                },
                "read"         => {'cat' => 'file.txt'},
                "read_random"  => {'catRAND' => 'file1.txt file2.txt file3.txt'},
                "read_seq"     => {'catSEQ' => 'file1.txt file2.txt file3.txt', 'catSEQ_idx' => 'catSEQ_status'},
                'meminfo'      => {'do' => 'do { local( @ARGV, $/ ) = "/proc/meminfo" ; <> }'},
                'mem'          => {
                                   'do' => "my ( $tot,$avail) = (split /\n/ ,do { local( @ARGV, $/ ) = \"/proc/meminfo\" ; <> })[0,2];$tot =~ s/\\D*//g; $avail =~ s/\\D*//g; sprintf \"%0.2f%%\\n\",(100*($tot-$avail)/$tot);"
                                  },
                'h(elp)?|\\?'  => {
                    'output' => 'exit
    read
    read_random
    read_seq
    meminfo
    mem_usage
    mem
    User> '
                },
                'mem_usage' => {'do' => 'my ( $tot,$avail) = (split /\\n/ ,do { local( @ARGV, $/ ) = "/proc/meminfo" ; <> })[0,2];$tot =~ s/\\D*//g; $avail =~ s/\\D*//g; sprintf "%0.2f%%\\n",(100*($tot-$avail)/$tot); '},
            },
            'not_matching_info' => '% Unknown command or computer name, or unable to find computer address',
            'output'            => 'User> '
        }
    );
    my $history_file = glob( '/tmp/fsm.history' );
    my $prompt       = '> ';
    my $line;
    my $final   = 0;
    my $term    = new Term::ReadLine 'bash';
    my $attribs = $term->Attribs->ornaments( 0 );
    $term->using_history();
    $term->read_history( $history_file );
    $term->clear_signals();

    my $fsm = FSM::Basic->new( \%states, 'accept' );
    my $out = "Password> ";
    while ( defined( $line = $term->readline( $out ) ) )
    {
        ( $final, $out ) = $fsm->run( $line );
        $term->write_history( $history_file );
        last if $final;
    }

    print $out if $final;

More sample code in the examples folder.

TODO

add "edit" to allow on the fly modification of the states definition

add "verify_states" to check all states are reachable from a original state

SEE ALSO

FSA::Rules

https://metacpan.org/pod/FSA::Rules

AUTHOR

DULAUNOY Fabrice, <fabrice at dulaunoy.com>

BUGS

Please report any bugs or feature requests to bug-FSM-basic at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=FSM-Basic. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT

You can find documentation for this module with the perldoc command.

    perldoc FSM::Basic

You can also look for information at:

ACKNOWLEDGEMENTS

LICENSE AND COPYRIGHT

Copyright 2008 - 2020 DULAUNOY Fabrice.

This program is free software; you can redistribute it and/or modify it under the terms of the the Artistic License (2.0). You may obtain a copy of the full license at:

http://www.perlfoundation.org/artistic_license_2_0

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This license does not grant you the right to use any trademark, service mark, tradename, or logo of the Copyright Holder.

This license includes the non-exclusive, worldwide, free-of-charge patent license to make, have made, use, offer to sell, sell, import and otherwise transfer the Package with respect to any patent claims licensable by the Copyright Holder that are necessarily infringed by the Package. If you institute patent litigation (including a cross-claim or counterclaim) against any party alleging that the Package constitutes direct or contributory patent infringement, then this Artistic License to you shall terminate on the date that such litigation is filed.

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