YAML::PP::Schema::Perl - Schema for serializing perl objects and special types

NAME  SYNOPSIS  DESCRIPTION  Tag Styles  Allow only certain classes  EXAMPLES  METHODS 

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NAME

YAML::PP::Schema::Perl − Schema for serializing perl objects and special types

SYNOPSIS

use YAML::PP;
# This can be dangerous when loading untrusted YAML!
my $yp = YAML::PP−>new( schema => [qw/ + Perl /] );
# or
my $yp = YAML::PP−>new( schema => [qw/ Core Perl /] );
my $yaml = $yp−>dump_string(sub { return 23 });
# loading code references
# This is very dangerous when loading untrusted YAML!!
my $yp = YAML::PP−>new( schema => [qw/ + Perl +loadcode /] );
my $code = $yp−>load_string(<<'EOM');
−−− !perl/code |
{
use 5.010;
my ($name) = @_;
say "Hello $name!";
}
EOM
$code−>("Ingy");

DESCRIPTION

This schema allows you to load and dump perl objects and special types.

Please note that loading objects of arbitrary classes can be dangerous in Perl. You have to load the modules yourself, but if an exploitable module is loaded and an object is created, its "DESTROY" method will be called when the object falls out of scope. File::Temp is an example that can be exploitable and might remove arbitrary files.

Dumping code references is on by default, but not loading (because that is easily exploitable since it's using string "eval").

Tag Styles

You can define the style of tags you want to support:

my $yp_perl_two_one = YAML::PP−>new(
schema => [qw/ + Perl tags=!!perl+!perl /],
);
"!perl" (default)

Only "!perl/type" tags are supported.

"!!perl"

Only "!!perl/type" tags are supported.

"!perl+!!perl"

Both "!perl/type" and "!!perl/tag" are supported when loading. When dumping, "!perl/type" is used.

"!!perl+!perl"

Both "!perl/type" and "!!perl/tag" are supported when loading. When dumping, "!!perl/type" is used.

YAML.pm, YAML::Syck and YAML::XS are using "!!perl/type" when dumping.

YAML.pm and YAML::Syck are supporting both "!perl/type" and "!!perl/type" when loading. YAML::XS currently only supports the latter.

Allow only certain classes

Since v0.017

Blessing arbitrary objects can be dangerous. Maybe you want to allow blessing only specific classes and ignore others. For this you have to instantiate a Perl Schema object first and use the "classes" option.

Currently it only allows a list of strings:

my $perl = YAML::PP::Schema::Perl−>new(
classes => ['Foo', 'Bar'],
);
my $yp = YAML::PP::Perl−>new(
schema => [qw/ + /, $perl],
);

Allowed classes will be loaded and dumped as usual. The others will be ignored.

If you want to allow no objects at all, pass an empty array ref.

EXAMPLES

This is a list of the currently supported types and how they are dumped into YAML:
array

# Code
[
qw/ one two three four /
]
# YAML
−−−
− one
− two
− three
− four

array_blessed

# Code
bless [
qw/ one two three four /
], "Just::An::Arrayref"
# YAML
−−− !perl/array:Just::An::Arrayref
− one
− two
− three
− four

circular

# Code
my $circle = bless [ 1, 2 ], 'Circle';
push @$circle, $circle;
$circle;
# YAML
−−− &1 !perl/array:Circle
− 1
− 2
− *1

coderef

# Code
sub {
my (%args) = @_;
return $args{x} + $args{y};
}
# YAML
−−− !perl/code |−
{
use warnings;
use strict;
(my(%args) = @_);
(return ($args{'x'} + $args{'y'}));
}

coderef_blessed

# Code
bless sub {
my (%args) = @_;
return $args{x} − $args{y};
}, "I::Am::Code"
# YAML
−−− !perl/code:I::Am::Code |−
{
use warnings;
use strict;
(my(%args) = @_);
(return ($args{'x'} − $args{'y'}));
}

hash

# Code
{
U => 2,
B => 52,
}
# YAML
−−−
B: 52
U: 2

hash_blessed

# Code
bless {
U => 2,
B => 52,
}, 'A::Very::Exclusive::Class'
# YAML
−−− !perl/hash:A::Very::Exclusive::Class
B: 52
U: 2

refref

# Code
my $ref = { a => 'hash' };
my $refref = \$ref;
$refref;
# YAML
−−− !perl/ref
=:
a: hash

refref_blessed

# Code
my $ref = { a => 'hash' };
my $refref = bless \$ref, 'Foo';
$refref;
# YAML
−−− !perl/ref:Foo
=:
a: hash

regexp

# Code
my $string = 'unblessed';
qr{$string}
# YAML
−−− !perl/regexp unblessed

regexp_blessed

# Code
my $string = 'blessed';
bless qr{$string}, "Foo"
# YAML
−−− !perl/regexp:Foo blessed

scalarref

# Code
my $scalar = "some string";
my $scalarref = \$scalar;
$scalarref;
# YAML
−−− !perl/scalar
=: some string

scalarref_blessed

# Code
my $scalar = "some other string";
my $scalarref = bless \$scalar, 'Foo';
$scalarref;
# YAML
−−− !perl/scalar:Foo
=: some other string

METHODS

new

my $perl = YAML::PP::Schema::Perl−>new(
tags => "!perl",
classes => ['MyClass'],
loadcode => 1,
dumpcode => 1,
);

The constructor recognizes the following options:
tags

Default: '"!perl"'

See "Tag Styles"

classes

Default: "undef"

Since: v0.017

Accepts an array ref of class names

loadcode

Default: 0

dumpcode

Default: 1

my $yp = YAML::PP−>new( schema => [qw/ + Perl −dumpcode /] );

register

A class method called by YAML::PP::Schema

construct_ref, represent_ref

Perl variables of the type "REF" are represented in yaml like this:

−−− !perl/ref
=:
a: 1

"construct_ref" returns the perl data:

my $data = YAML::PP::Schema::Perl−>construct_ref([ '=', { some => 'data' } );
my $data = \{ a => 1 };

"represent_ref" turns a "REF" variable into a YAML mapping:

my $data = YAML::PP::Schema::Perl−>represent_ref(\{ a => 1 });
my $data = { '=' => { a => 1 } };

construct_scalar, represent_scalar

Perl variables of the type "SCALAR" are represented in yaml like this:

−−− !perl/scalar
=: string

"construct_scalar" returns the perl data:

my $data = YAML::PP::Schema::Perl−>construct_ref([ '=', 'string' );
my $data = \'string';

"represent_scalar" turns a "SCALAR" variable into a YAML mapping:

my $data = YAML::PP::Schema::Perl−>represent_scalar(\'string');
my $data = { '=' => 'string' };

construct_regex, represent_regex

"construct_regex" returns a "qr{}" object from the YAML string:

my $qr = YAML::PP::Schema::Perl−>construct_regex('foo.*');

"represent_regex" returns a string representing the regex object:

my $string = YAML::PP::Schema::Perl−>represent_regex(qr{...});

evaluate_code, represent_code

"evaluate_code" returns a code reference from a string. The string must start with a "{" and end with a "}".

my $code = YAML::PP::Schema::Perl−>evaluate_code('{ return 23 }');

"represent_code" returns a string representation of the code reference with the help of B::Deparse:

my $string = YAML::PP::Schema::Perl−>represent_code(sub { return 23 });

construct_glob, represent_glob

"construct_glob" returns a glob from a hash.

my $glob = YAML::PP::Schema::Perl−>construct_glob($hash);

"represent_glob" returns a hash representation of the glob.

my $hash = YAML::PP::Schema::Perl−>represent_glob($glob);

object

Does the same as "bless":

my $object = YAML::PP::Schema::Perl−>object($data, $class);

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