PGP

NAME

PGP - perl module to work with PGP messages

SYNOPSIS

use PGP;

$message = new PGP $pgppath;

DESCRIPTION

The PGP module allow a perl script to work with PGP related files.

* PGP::new
$pgp = new PGP [$pgppath], [$pgpexec];

Create the PGP encapsulation object. The standard location for the PGP executable is /usr/local/bin/pgp.

* PGP::Exec
$pid = Exec $pgp $args, $in, $out, $err;

Execute the PGP command and attach the $in, $out, $err file handles. This should be fine for the moment, but need to look into making sure that data is not written to a temporary file anywhere.

The $args variable can have several substituted strings:

%p PGP path variable %r Path to PGP keyring %k Specified user

The file handle variables--$in, $out and $err--are send as normal filehandle names, but they reside in the PGP package. For example, the following procedure call is made:

PGP->Exec ($args, FIN, FOUT, FERR);

Even though the file handles were specified as FIN, FOUT and FERR; they must be referred to as PGP::FIN, PGP::FOUT and PGP::FERR in the orignal procedure that made the call.

* PGP::Sign
$signed_document = Sign $pgp %args;

The Sign procedure will take a file or data and sign with a PGP secret key. The default behavior is to sign the data with the last secret key added to the keyring, but that can be overridden with the Key argument. This method always returns the signed document.

The %args consist of a series of keys and values. Since there are several variations in the way data can be signed, not all the following options must be specified. This approach also makes it much easier to scale to new versions of PGP with more options.

The only absolute argument that is always required is the Password.

Examples

Sign $pgp Password => 'xyz', File => '/etc/motd', Clear => 1, Armor => 1;

This would return a signed copy of the /etc/motd file. In this case, we use a file as the input, but the output is returned at the method's termination. The orignal file remains in the clear, and the signature is ASCII armored (Base64).

Sign $pgp Password => 'abc', Text => 'Important info', Armor => 1, Signfile => 'signed.asc', Key => $keyobj;

This is sort of the reverse of the first example. It takes what is in the Text field and signs it. It then puts the result in the file signed.asc and returns it to the caller. In this case, the entire message is ASCII armored including the orignal text (i.e. Text). We also specify another secret key to produce the signature. For more information on the the key objects, please see ``PGP::Key'' section.

* PGP::Encrypt
$encrypted_document = Encrypt $pgp %args;

The Encrypt method produces an encrypted document with the given public keys specified by Key. The Encrypt method follow the same conventions as the Sign method. The data to be encrypted can be sent to the method or can reside in a file. The resulting encrypted data can also reside in a file or be sent back to the caller.

In addition to encrypting a document, the document can also be signed by using the Sign key in the %args array. If the document is to be signed by the default secret key (last key added to the secret keyring), then Sign can be left undefined or contain something other than a reference to a key object. Otherwise the Sign key should contain a reference to a specific key object (see ``PGP::Key'').

* PGP::Decrypt
\%stats = Decrypt $pgp %args;

Decrypt will use a PGP secret key to decrypt a message. The secret key must reside on the secret keyring. The Decrypt method follows the same conventions for data transfer that Sign and Encrypt follow. The resulting associative array that is sent back contains three fields:

The following are the accepted arguments:

The Password argument is required to perform the decryption of the document. The Keyring argument is also required if any document information is to be returned.

* PGP::Document_Info
\%doc = Document_Info $pgp %args;

Document_Info returns an associative array or a reference to an associative array to the caller. This returned structure contains information about the document that is sent to the Document_Info method. The returned structure is fairly straight forward:

The Document_Info method currently accepts the following arguments:

PGP::Keyring

The PGP::Keyring object is used to perform key management functions.

* PGP::Keyring::new
$Keyring = new PGP::Keyring $pgpkeyring;

* PGP::Keyring::Add_Key
$signature = Add_Key $Keyring $signature;

Add a signature to the keyring. At this point, there is no error checking or verification that the key has been added.

* PGP::Remove_Key
Remove_Key $Keyring $key;

Remove a signature from a keyring.

* PGP::Extract_Key
$key = Extract_Key $Keyring $keyobj;

Extract a key from the specified keyring. A real simple dirty way of extracting the key.

* PGP::Generate_Key
Generate_Key $Keyring;

Generate a new secret and public key set. This routine will not be present in the first rev of code. It is also subject to change.

* PGP::Revoke_Key
$certificate = Revoke_Key $Keyring $Keyobj;

Produce a revocation certificate for the given key. Revocation is actually a two step process. We must first mark the key as revoked. This is the same as the Remove_Key method. After flaging the key, the key must be extracted to produce a revocation certificate.

* PGP::Keyring::List_Keys
@{$keyobj} = List_Keys $Keyring;

List the keys on a given keyring. This routine simply captures the output of the command pgp -kc $keyring and does a quick parse on it. It takes the lines that it parses, and constructs PGP::Key objects. In the near future, this function will also pass the trust factors to the PGP::Key object. We got it in the output, so why not use it.

* PGP::Keyring::Find
@keys = Find $keyring %criteria; \@keys = Find $keyring %criteria; $key = Find $keyring %criteria; (Single match)

Function to locate a single key.

PGP::Key

The PGP::Key object is used to store the individual key information. It is primarily used by the PGP::Keyring object and for passing to the various methods that accept key parameters to encrypt and sign documents.

Future revisions will provide actual methods to do key comparison for the trust and validity factors. These methods will provide a standardized way to determine which keys can be trusted and which keys should not be used at all.

* PGP::Key::new
$key = new PGP::Key $keyline;

This is the constructor for the PGP::Key object. This is primarily used by the PGP::Keyring methods. The PGP::Keyring methods keep track of the keys and maintain the Trust and Validity components. About the only useful method is the PGP::Key::Fingerprint, which will return a string that is the finger print of the given key.

+ PGP::Key::Add_ID
Add_ID $key $desc;

The Add_ID method will add identification information to the owner and email portions of the given PGP::Key object. This is to support keys that multiple identification packets associated with them.

* PGP::Key::Trust
This will set and/or retrieve the trust factor. Currently, this routine will just store what is sent to it. Need to define some ``trust'' variables and provide useful routines to use them.

* PGP::Key::Validity
This function will set and/or return the validity factor. This subroutine is very much like PGP::Key::Trust. It also needs to be worked on quite a bit.

* PGP::Key::Fingerprint
$fingerprint = Fingerprint $key;

Known Bugs and Limitations

+ Hopefully none, proabably many!

Author

Gerard Hickey RR 2 Box 409 Lower Main St. North Berwick, ME 03906 hickey@ctron.com

Copyrights

Copyleft (l) 1996, by Gerard Hickey

What this means is that this program may be copied freely given that there is no payment in exchange for this program, and that all the source is left intact with all comments and documentation. If you wish to modify this program to correct bugs or to extend it's usefullness, please coordinate such actions with the author.