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.

There is nothing new printed on using `use Data::Dumper' print Dumper $keystring;`. It is same as my simple print statement in both code. — shivams, Dec 30 '14 at 06:59
It could be that there is corrupt character at the beginning of file. Extra space or line. — Chankey Pathak, Dec 30 '14 at 07:47
How am i going to get rid of that? Because when i am printing the content of file it is looking fine. — shivams, Dec 30 '14 at 07:49
Open the file in notepad++ and check the encoding. Also see this: http://stackoverflow.com/a/20837236/257635 — Chankey Pathak, Dec 30 '14 at 07:52
This is what i am getting from the command `text/plain; charset=us-ascii` Also this is the same output as i will get for ssh private key file i.e. id_rsa — shivams, Dec 30 '14 at 08:07
Vexing. Seems a bug to me, but I don't know how to view the Perl source itself. — Maarten Bodewes, Dec 30 '14 at 11:44
You're setting UTF-8 encoding when you write the string to the file, but not when you read it. This can lead to the same sequence of bytes getting printed, depending on your terminal settings, but different sequences of bytes getting fed to the OpenSSL code. Not saying this _is_ the problem, but it's at least worth giving setting the encoding on read a shot. It's not like it's a huge effort. — Calle Dybedahl, Dec 30 '14 at 18:18
@CalleDybedahl (not org author) I've tried every kind of character encoding including `:raw`, `binary` and line endings, all to no avail. It *was* indeed worth the shot :) — Maarten Bodewes, Dec 30 '14 at 21:11

score 1 · Answer 1 · answered Jan 20 '15 at 10:43

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.

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

1 Answers1