Signing data using Crypt::OpenSSL::RSA in perl

Question

I am trying to sign my data using Crypt::OpenSSL::RSA in perl. This is my code

use Crypt::OpenSSL::RSA;
open $privfh, '>:encoding(UTF-8)', 'private_key';

$rsa = Crypt::OpenSSL::RSA->generate_key(1024); 

$key_string=$rsa->get_private_key_string();
print $privfh $key_string;

$rsa_priv = Crypt::OpenSSL::RSA->new_private_key($key_string);

$rsa_pub = $rsa->get_public_key_string();

$plaintext="hello";
$signature = $rsa_priv->sign($plaintext);
print "Signed correctly\n" if ($rsa->verify($plaintext, $signature));

This program is running fine and i am able to sign data correctly. But the issue is that i have to sign a lot of data so i am writing key_string to a file so that i can use it again and again but the issue is when i try to use it again using following code

use Crypt::OpenSSL::RSA;
open FILE ,'<','private_key';

{
  local $/;
  $keystring=<FILE>;
 }
 print "$keystring\n";
 $rsa_priv = Crypt::OpenSSL::RSA->new_private_key($key_string);

it is throwing error and not generating $rsa_priv. The error given by the program is RSA.xs:178: OpenSSL error: no start line at testperl.pl line 11, <FILE> line 1. What should i do so that i am able to signing again and again after generating key for one time only.

Answer 1

You are reading the file into a variable $keystring but initializing the private key using the variable $key_string. Change $keystring to $key_string.

Perl offers use strict; to avoid these kind of problems. Also, if you use use warnings;, perl will also warn you about accessing unitialized variables.