How Data Member Accessor Methods are Created

Each module in the GnuPG::Interface bundle relies on Moo to generate the get/set methods used to set the object's data members. This is very important to realize. This means that any data member which is a list has special methods assigned to it for pushing, popping, and clearing the list.

Understanding Bidirectional Communication

It is also imperative to realize that this package uses interprocess communication methods similar to those used in IPC::Open3 and "Bidirectional Communication with Another Process" in perlipc, and that users of this package need to understand how to use this method because this package does not abstract these methods for the user greatly. This package is not designed to abstract this away entirely (partly for security purposes), but rather to simply help create 'proper', clean calls to GnuPG, and to implement key-listing parsing. Please see "Bidirectional Communication with Another Process" in perlipc to learn how to deal with these methods.

Using this package to do message processing generally invovlves creating a GnuPG::Interface object, creating a GnuPG::Handles object, setting some options in its options data member, and then calling a method which invokes GnuPG, such as clearsign. One then interacts with with the handles appropriately, as described in "Bidirectional Communication with Another Process" in perlipc.

Initialization Methods

new( %initialization_args )

This methods creates a new object. The optional arguments are initialization of data members.

hash_init( %args ).

Object Methods which use a GnuPG::Handles Object

list_public_keys( % )

list_sigs( % )

list_secret_keys( % )

encrypt( % )

encrypt_symmetrically( % )

sign( % )

clearsign( % )

detach_sign( % )

sign_and_encrypt( % )

decrypt( % )

verify( % )

import_keys( % )

export_keys( % )

recv_keys( % )

send_keys( % )

search_keys( % )

These methods each correspond directly to or are very similar to a GnuPG command described in gpg. Each of these methods takes a hash, which currently must contain a key of handles which has the value of a GnuPG::Handles object. Another optional key is command_args which should have the value of an array reference; these arguments will be passed to GnuPG as command arguments. These command arguments are used for such things as determining the keys to list in the export_keys method. Please note that GnuPG command arguments are not the same as GnuPG options. To understand what are options and what are command arguments please read "COMMANDS" in gpg and "OPTIONS" in gpg.

Each of these calls returns the PID for the resulting GnuPG process. One can use this PID in a "waitpid" call instead of a "wait" call if more precise process reaping is needed.

These methods will attach the handles specified in the handles object to the running GnuPG object, so that bidirectional communication can be established. That is, the optionally-defined stdin, stdout, stderr, status, logger, and passphrase handles will be attached to GnuPG's input, output, standard error, the handle created by setting status-fd, the handle created by setting logger-fd, and the handle created by setting passphrase-fd respectively. This tying of handles of similar to the process done in IPC::Open3.

If you want the GnuPG process to read or write directly to an already-opened filehandle, you cannot do this via the normal IPC::Open3 mechanisms. In order to accomplish this, set the appropriate handles data member to the already-opened filehandle, and then set the option direct to be true for that handle, as described in "options" in GnuPG::Handles. For example, to have GnuPG read from the file input.txt and write to output.txt, the following snippet may do:

my $infile  = IO::File->new( 'input.txt' );
my $outfile = IO::File->new( '>output.txt' );
my $handles = GnuPG::Handles->new( stdin  => $infile,
                                   stdout => $outfile,
                                 );
$handles->options( 'stdin'  )->{direct} = 1;
$handles->options( 'stdout' )->{direct} = 1;

If any handle in the handles object is not defined, GnuPG's input, output, and standard error will be tied to the running program's standard error, standard output, or standard error. If the status or logger handle is not defined, this channel of communication is never established with GnuPG, and so this information is not generated and does not come into play.

If the passphrase data member handle of the handles object is not defined, but the the passphrase data member handle of GnuPG::Interface object is, GnuPG::Interface will handle passing this information into GnuPG for the user as a convenience. Note that this will result in GnuPG::Interface storing the passphrase in memory, instead of having it simply 'pass-through' to GnuPG via a handle.

If neither the passphrase data member of the GnuPG::Interface nor the passphrase data member of the handles object is defined, then GnuPG::Interface assumes that access and control over the secret key will be handled by the running gpg-agent process. This represents the simplest mode of operation with the GnuPG "stable" suite (version 2.2 and later). It is also the preferred mode for tools intended to be user-facing, since the user will be prompted directly by gpg-agent for use of the secret key material. Note that for programmatic use, this mode requires the gpg-agent and pinentry to already be correctly configured.

Other Methods

get_public_keys( @search_strings )

get_secret_keys( @search_strings )

get_public_keys_with_sigs( @search_strings )

These methods create and return objects of the type GnuPG::PublicKey or GnuPG::SecretKey respectively. This is done by parsing the output of GnuPG with the option with-colons enabled. The objects created do or do not have signature information stored in them, depending if the method ends in _sigs; this separation of functionality is there because of performance hits when listing information with signatures.

test_default_key_passphrase()

This method will return a true or false value, depending on whether GnuPG reports a good passphrase was entered while signing a short message using the values of the passphrase data member, and the default key specified in the options data member.

version()

Returns the version of GnuPG that GnuPG::Interface is running.

Encrypting

# We'll let the standard error of GnuPG pass through
# to our own standard error, by not creating
# a stderr-part of the $handles object.
my ( $input, $output ) = ( IO::Handle->new(),
                           IO::Handle->new() );
my $handles = GnuPG::Handles->new( stdin    => $input,
                                   stdout   => $output );
# this sets up the communication
# Note that the recipients were specified earlier
# in the 'options' data member of the $gnupg object.
my $pid = $gnupg->encrypt( handles => $handles );
# this passes in the plaintext
print $input @original_plaintext;
# this closes the communication channel,
# indicating we are done
close $input;
my @ciphertext = <$output>;  # reading the output
waitpid $pid, 0;  # clean up the finished GnuPG process

Signing

# This time we'll catch the standard error for our perusing
my ( $input, $output, $error ) = ( IO::Handle->new(),
                                   IO::Handle->new(),
                                   IO::Handle->new(),
                                 );
my $handles = GnuPG::Handles->new( stdin    => $input,
                                   stdout   => $output,
                                   stderr   => $error,
                                 );
# indicate our pasphrase through the
# convenience method
$gnupg->passphrase( $passphrase );
# this sets up the communication
my $pid = $gnupg->sign( handles => $handles );
# this passes in the plaintext
print $input @original_plaintext;
# this closes the communication channel,
# indicating we are done
close $input;
my @ciphertext   = <$output>;  # reading the output
my @error_output = <$error>;   # reading the error
close $output;
close $error;
waitpid $pid, 0;  # clean up the finished GnuPG process

Decryption

# This time we'll catch the standard error for our perusing
# as well as passing in the passphrase manually
# as well as the status information given by GnuPG
my ( $input, $output, $error, $passphrase_fh, $status_fh )
  = ( IO::Handle->new(),
      IO::Handle->new(),
      IO::Handle->new(),
      IO::Handle->new(),
      IO::Handle->new(),
    );
my $handles = GnuPG::Handles->new( stdin      => $input,
                                   stdout     => $output,
                                   stderr     => $error,
                                   passphrase => $passphrase_fh,
                                   status     => $status_fh,
                                 );
# this time we'll also demonstrate decrypting
# a file written to disk
# Make sure you "use IO::File" if you use this module!
my $cipher_file = IO::File->new( 'encrypted.gpg' );
# this sets up the communication
my $pid = $gnupg->decrypt( handles => $handles );
# This passes in the passphrase
print $passphrase_fh $passphrase;
close $passphrase_fh;
# this passes in the plaintext
print $input $_ while <$cipher_file>;
# this closes the communication channel,
# indicating we are done
close $input;
close $cipher_file;
my @plaintext    = <$output>;    # reading the output
my @error_output = <$error>;     # reading the error
my @status_info  = <$status_fh>; # read the status info
# clean up...
close $output;
close $error;
close $status_fh;
waitpid $pid, 0;  # clean up the finished GnuPG process

Printing Keys

# This time we'll just let GnuPG print to our own output
# and read from our input, because no input is needed!
my $handles = GnuPG::Handles->new();
my @ids = ( 'ftobin', '0xABCD1234ABCD1234ABCD1234ABCD1234ABCD1234' );
# this time we need to specify something for
# command_args because --list-public-keys takes
# search ids as arguments
my $pid = $gnupg->list_public_keys( handles      => $handles,
                                    command_args => [ @ids ] );
 waitpid $pid, 0;

Creating GnuPG::PublicKey Objects

my @ids = [ 'ftobin', '0xABCD1234ABCD1234ABCD1234ABCD1234ABCD1234' ];
my @keys = $gnupg->get_public_keys( @ids );
# no wait is required this time; it's handled internally
# since the entire call is encapsulated

Custom GnuPG call

# assuming $handles is a GnuPG::Handles object
my $pid = $gnupg->wrap_call
  ( commands     => [ qw( --list-packets ) ],
    command_args => [ qw( test/key.1.asc ) ],
    handles      => $handles,
  );
  my @out = <$handles->stdout()>;
  waitpid $pid, 0;

Large Amounts of Data

Currently there are problems when transmitting large quantities of information over handles; I'm guessing this is due to buffering issues. This bug does not seem specific to this package; IPC::Open3 also appears affected.

OpenPGP v3 Keys

I don't know yet how well this module handles parsing OpenPGP v3 keys.

RHEL 7 Test Failures

Testing with the updates for version 1.00 we saw intermittent test failures on RHEL 7 with GnuPG version 2.2.20. In some cases the tests would all pass for several runs, then one would fail. We're unable to reliably reproduce this so we would be interested in feedback from other users.