in reply to Re: Crypt::OpenPGP PassphraseCallback example please
in thread Crypt::OpenPGP PassphraseCallback example please

Here is what I am doing thus far, I appologize if I am long winded.
#### creating private/public key files, seems to work fine 
use Crypt::OpenPGP;
$pgp = Crypt::OpenPGP->new ();

%attrib = (
              'Type'  => 'RSA',
              'Size' => '1024',
              'Identity' => 'Garett L Holmes gaholmes@hotmail.com',
              'Passphrase' => 'password',
              'Cipher' => 'DES3',
              'Verbosity'  => '1',
              'Compat'      =>  'PGP5',
          );

($pubkey, $privkey) = $pgp->keygen( %attrib ) or die $pgp->errstr;
$public = $pubkey->save;
open(PUBLIC,">test.public") or die "COULD NOT OPEN pub\n";
print PUBLIC $public;
close(PUBLIC);

$private = $privkey->save;
open(PRIVATE,">test.private") or die "COULD NOT OPEN priv\n"; 
print PRIVATE $private; 
close(PRIVATE);

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#### Then I encrypt the data using the private key, seems to work 
use Crypt::OpenPGP;
use Crypt::OpenPGP::KeyRing;
$pgp = Crypt::OpenPGP->new(PubRing => 'test.public');
$crypt = $pgp->encrypt(
   Compat      =>  'PGP5',
   Data => 'squeamish ossifrage',
   Recipients => 'gaholmes\@hotmail.com',
   Armour => 1,
);
defined($crypt) ? print $crypt : die $pgp->errstr;

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This is where I seem to lose it. I now want to decrypt $crypt using the secret key. I tried this this but know now that I am not understanding the passphrasecallback. I have read the documentation but can't seem to grasp it. After all the time I spent getting he modules installed and functioning on win32 I think I have brain burn. The module looks like just what I need and I would appreciate any assistance with understanding it. Thanks in advance.
boat73 
$pgp = Crypt::OpenPGP->new (
       "SecRing" => './pgp/test.private'
  )or die Crypt::OpenPGP->errstr;



        my $plaintext = $pgp->decrypt(
                   "Data"        =>  $crypt,
                   "PassphraseCallback" => \&passphrase_cb
             );
    
  die "decryption failed: ", $pgp->errstr unless $plaintext;

print "PLAINTEXT IS $plaintext\n";    


    sub passphrase_cb {
        if (my $cert = $_[0]) {
            printf "Enter passphrase for secret key %s: ",
                $cert->key_id_hex;
        } else {
            print "Enter passphrase: ";
        }
    }

&passphrase_cb(password);
    sub passphrase_cb {
        if (my $cert = $_[0]) {
            printf "Enter passphrase for secret key %s: ",
                $cert->key_id_hex;
        } else {
            print "Enter passphrase: ";
        }
    }

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Edited by Chady -- fixed code tags.

Replies are listed 'Best First'.
Re: Re: Re: Crypt::OpenPGP PassphraseCallback example please
by hv (Prior) on Mar 17, 2004 at 11:49 UTC

    I think the examples given are a bit misleading; the key part is the definition of the PassphraseCallback argument in the docs, in particular the last part:

        In either case, the callback routine should return the
    passphrase, a scalar string.

    The various examples sometimes leave off the final call to _prompt(), and since it is an undocumented internal routine it isn't obvious that this is doing the guts of the work: showing a prompt, setting noecho, getting the text from the user's input, and returning the resulting string.

    I'd suggest looking at the code for _prompt() in the module (it's in the top-level Crypt/OpenPGP.pm) to see what needs doing, and then (probably) avoid using ths undocumented interface directly by copying what you need out of there.

    Here's some similar code I use in a less critical situation, which copes with the possibility that Term::Readkey isn't installed by letting the password be entered unhidden:

    sub getpass {
    my $prompt = shift;
    local $| = 1;
    print "$prompt: ";
    eval { require Term::ReadKey };
    my $haveterm = !$@;
    Term::ReadKey::ReadMode(2) if $haveterm;    # turn on noecho
    my $pass = <STDIN>;
    chomp $pass;
    Term::ReadKey::ReadMode(0) if $haveterm;    # restore
    print "\n";
    return $pass;
}

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    Hugo

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      This is a big help but I have another question. In reading more it looks like PassphraseCallback is used only when you want a user to enter the passphrase. If I wan't to hard code the passphrase into my script shouldn't this code work? Or is Passphrase only used for symetric? When I run it I get the following error

      decryption failed: Seckey unlock failed: Bad checksum

      $pgp = Crypt::OpenPGP->new (
       "SecRing" => 'test.private'
  )or die Crypt::OpenPGP->errstr;



        my $plaintext = $pgp->decrypt(
                   "Data"        =>  $crypt,
                   "Passphrase" => 'password'
             );<br>
    
  die "decryption failed: ", $pgp->errstr unless $plaintext;

print "PLAINTEXT IS $plaintext\n";

      [download]


      Thanks boat73
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