Twitter OAuth 1.0 authentication with signature in perl - perl

Question

I'm getting this problem with my app in perl for oauth authentication:
401 Unauthorized Failed to validate oauth signature and token
Here is my code:
sub Twitter {
my $IN = new CGI;
my $qs = build_query({
oauth_callback => $callback_url,
oauth_consumer_key => $consumer_key,
oauth_nonce => time,
oauth_signature_method => "HMAC-SHA1",
oauth_timestamp => time,
oauth_version => "1.0"
});
# Create Signature
my $signing_key = $IN->escape($consumer_secret)."&";
my $base_signature = "POST&".$IN->escape($request_token_url)."&".$qs;
use Digest::HMAC_SHA1;
my $hmac = Digest::HMAC_SHA1->new($signing_key);
$hmac->add($base_signature);
$qs .= "&oauth_signature=".$IN->escape($hmac->b64digest);
# Fetch the page
use LWP;
my $ua = LWP::UserAgent->new;
my $req = HTTP::Request->new(POST => $request_token_url);
$req->content_type('application/x-www-form-urlencoded');
$req->content($qs);
my $res = $ua->request($req);
# Check the outcome of the response
unless ($res->is_success) {
print $IN->header.$res->status_line, "\n";
print $res->content;
exit;
}
print $IN->header.$res->content;
}
sub build_query {
my $input = shift;
use URI;
my $uri = URI->new;
$uri->query_form($input);
return $uri->query;
}
I have obviously deleted my callback url and key information.

Answer 1

I figured it out. I was encoding the signature wrong, I had to sort my query strings, and the call back URL is not needed in this instance. Here is my working code:
sub Twitter {
my $IN = new CGI;
my $params = {
oauth_consumer_key => $consumer_key,
oauth_nonce => time,
oauth_signature_method => "HMAC-SHA1",
oauth_timestamp => time,
oauth_version => "1.0"
};
my $qs = build_sorted_query($params);
my $signing_key = $IN->escape($consumer_secret)."&";
my $signature_base = "POST&".$IN->escape($request_token_url)."&".$IN->escape($qs);
use Digest::HMAC_SHA1;
use MIME::Base64;
my $hmac = Digest::HMAC_SHA1->new($signing_key);
$hmac->add($signature_base);
$params->{oauth_signature} = $IN->escape(encode_base64($hmac->digest));
$qs = build_sorted_query($params);
use LWP;
my $ua = LWP::UserAgent->new;
my $req = HTTP::Request->new(POST => $request_token_url);
$req->content_type('application/x-www-form-urlencoded');
$req->content($qs);
my $res = $ua->request($req);
# Check the outcome of the response
unless ($res->is_success) {
print $IN->header.$res->status_line, "\n";
print $res->content;
exit;
}
print $IN->header.$res->content;
return;
}
sub build_sorted_query {
my $input = shift;
my $qs;
foreach (sort keys %$input) {
$qs .= $_."=".$input->{$_}."&";
}
return substr ($qs, 0, -1);
}
Thanks for looking!