File Coverage

blib/lib/Amazon/PAApi5/Signature.pm

Criterion	Covered	Total	%
statement	75	76	98.6
branch	5	8	62.5
condition	9	16	56.2
subroutine	19	20	95.0
pod	6	6	100.0
total	114	126	90.4

package Amazon::PAApi5::Signature;
use strict;
use warnings;
use Carp qw/croak/;
use POSIX qw/strftime/;
use Digest::SHA qw/sha256_hex hmac_sha256 hmac_sha256_hex/;
use Class::Accessor::Lite (
    rw  => [qw/
        access_key
        secret_key
        payload
        resource_path
        operation
        host
        region
        aws_headers
        str_signed_header
    /],
    ro  => [qw/
        service
        http_method
        hmac_algorithm
        aws4_request
        x_amz_date
        current_date
    /],
);

our $VERSION = '0.04';

sub new {
    my $class      = shift;
    my $access_key = shift or croak 'access_key is required';
    my $secret_key = shift or croak 'secret_key is required';
    my $payload    = shift or croak 'payload is required';
    my $opt        = shift || {};

    my $operation     = $opt->{operation} || 'SearchItems';
    my $resource_path = $opt->{resource_path} ? $opt->{resource_path} : '/paapi5/' . lc($operation);

    return bless {
        access_key     => $access_key,
        secret_key     => $secret_key,
        payload        => $payload,
        resource_path  => $resource_path,
        operation      => $operation,
        host           => $opt->{host}           || 'webservices.amazon.com',
        region         => $opt->{region}         || 'us-east-1',
        service        => $opt->{service}        || 'ProductAdvertisingAPI',
        http_method    => $opt->{http_method}    || 'POST',
        hmac_algorithm => $opt->{hmac_algorithm} || 'AWS4-HMAC-SHA256',
        aws4_request   => $opt->{aws4_request}   || 'aws4_request',
        x_amz_date     => $class->_get_time_stamp,
        current_date   => $class->_get_date,
        aws_headers    => {},
        str_signed_header => '',
    }, $class;
}

sub req_url {
    my ($self) = @_;

    return sprintf("https://%s%s", $self->host, $self->resource_path);
}

sub _prepare_canonical_url {
    my ($self) = @_;

    my $canonical_url = $self->http_method . "\n";

    $canonical_url .= $self->resource_path . "\n\n";

    my $signed_headers = '';
    for my $key (grep { $_ !~ m!content-type! } sort keys %{$self->aws_headers}) {
        $signed_headers .=  lc($key) . ';';
        $canonical_url .= lc($key) . ':' . $self->aws_headers->{$key} . "\n";
    }

    $canonical_url .= "\n";

    $self->str_signed_header(substr($signed_headers, 0, -1)); # remove ';'
    $canonical_url .= $self->str_signed_header . "\n";

    $canonical_url .= sha256_hex($self->payload);

    return $canonical_url;
}

sub _prepare_string_to_sign {
    my ($self, $canonical_url) = @_;

    return join("\n",
        $self->hmac_algorithm,
        $self->x_amz_date,
        join('/', $self->current_date, $self->region, $self->service, $self->aws4_request),
        sha256_hex($canonical_url),
    );
}

sub _calculate_signature {
    my ($self, $string_to_sign) = @_;

    my $signature_key = $self->_get_signature_key;

    return lc(hmac_sha256_hex($string_to_sign, $signature_key));
}

sub _build_authorization_string {
    my ($self, $signature) = @_;

    return $self->hmac_algorithm . ' '
        . 'Credential=' . join('/', $self->access_key, $self->_get_date, $self->region, $self->service, $self->aws4_request)
        . ',SignedHeaders=' . $self->str_signed_header
        . ',Signature=' . $signature
    ;
}

sub headers {
    my ($self) = @_;

    my $aws_headers = $self->aws_headers;

    $aws_headers->{'content-encoding'} = 'amz-1.0';
    $aws_headers->{'content-type'}     = 'application/json; charset=UTF-8';
    $aws_headers->{'host'}             = $self->host;
    $aws_headers->{'x-amz-date'}       = $self->x_amz_date;
    $aws_headers->{'x-amz-target'}     = $self->_build_amz_target;

    my $canonical_url = $self->_prepare_canonical_url;

    my $string_to_sign = $self->_prepare_string_to_sign($canonical_url);

    my $signature = $self->_calculate_signature($string_to_sign);

    $aws_headers->{Authorization} = $self->_build_authorization_string($signature);

    $self->aws_headers($aws_headers);

    return %{$aws_headers};
}

sub headers_as_arrayref {
    return [shift->headers];
}

sub headers_as_hashref {
    return {shift->headers};
}

sub _get_signature_key {
    my ($self) = @_;

    my $k_date    = hmac_sha256($self->current_date, 'AWS4' . $self->secret_key);
    my $k_region  = hmac_sha256($self->region, $k_date);
    my $k_service = hmac_sha256($self->service, $k_region);
    my $k_signing = hmac_sha256($self->aws4_request, $k_service);

    return $k_signing;
}

sub _build_amz_target {
    return 'com.amazon.paapi5.v1.ProductAdvertisingAPIv1.' . shift->operation;
}

sub _get_time_stamp {
    return strftime("%Y%m%dT%H%M%SZ", gmtime()); # 20191128T235650Z
}

sub _get_date {
    return strftime("%Y%m%d", gmtime()); # 20191128
}

sub to_request {
    my ($self) = @_;

    return {
        method  => $self->http_method,
        uri     => $self->req_url,
        headers => $self->headers_as_hashref,
        content => $self->payload,
    };
}

1;

__END__