Provided by: libgnupg-interface-perl_1.04-1_all 
NAME
GnuPG::Interface - Perl interface to GnuPG
SYNOPSIS
# A simple example
use IO::Handle;
use GnuPG::Interface;
# setting up the situation
my $gnupg = GnuPG::Interface->new();
$gnupg->options->hash_init( armor => 1,
homedir => '/home/foobar' );
# Note you can set the recipients even if you aren't encrypting!
$gnupg->options->push_recipients( 'ftobin@cpan.org' );
$gnupg->options->meta_interactive( 0 );
# how we create some handles to interact with GnuPG
my $input = IO::Handle->new();
my $output = IO::Handle->new();
my $handles = GnuPG::Handles->new( stdin => $input,
stdout => $output );
# Now we'll go about encrypting with the options already set
my @plaintext = ( 'foobar' );
my $pid = $gnupg->encrypt( handles => $handles );
# Now we write to the input of GnuPG
print $input @plaintext;
close $input;
# now we read the output
my @ciphertext = <$output>;
close $output;
waitpid $pid, 0;
DESCRIPTION
GnuPG::Interface and its associated modules are designed to provide an object-oriented method for
interacting with GnuPG, being able to perform functions such as but not limited to encrypting, signing,
decryption, verification, and key-listing parsing.
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.
GnuPG Versions
As of this version of GnuPG::Interface, there are three supported versions of GnuPG: 1.4.x, 2.2.x, and
2.4.x. The GnuPG download page <https://gnupg.org/download/index.html> has updated information on the
currently supported versions.
GnuPG released 2.0 and 2.1 versions in the past and some packaging systems may still provide these if you
install the default "gpg", "gnupg", "gnupg2", etc. packages. 2.0 and 2.1 versions are not supported, so
you may need to find additional package repositories or build from source to get the updated version.
OBJECT METHODS
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.
Invoking GnuPG with a custom call
GnuPG::Interface attempts to cover a lot of the commands of GnuPG that one would want to perform;
however, there may be a lot more calls that GnuPG is and will be capable of, so a generic command
interface is provided, "wrap_call".
wrap_call( %args )
Call GnuPG with a custom command. The %args hash must contain at least the following keys:
commands
The value of this key in the hash must be a reference to a a list of commands for GnuPG, such as
"[ qw( --encrypt --sign ) ]".
handles
As with most other GnuPG::Interface methods, handles must be a GnuPG::Handles object.
The following keys are optional.
command_args
As with other GnuPG::Interface methods, the value in hash for this key must be a reference to a
list of arguments to be passed to the GnuPG command, such as which keys to list in a key-listing.
OBJECT DATA MEMBERS
call
This defines the call made to invoke GnuPG. Defaults to '/usr/bin/gpg'; this should be changed if
there is a different name for the binary on your system.
passphrase
In order to lessen the burden of using handles by the user of this package, setting this option to
one's passphrase for a secret key will allow the package to enter the passphrase via a handle to
GnuPG by itself instead of leaving this to the user. See also "passphrase" in GnuPG::Handles.
options
This data member, of the type GnuPG::Options; the setting stored in this data member are used to
determine the options used when calling GnuPG via any of the object methods described in this
package. See GnuPG::Options for more information.
EXAMPLES
The following setup can be done before any of the following examples:
use IO::Handle;
use GnuPG::Interface;
my @original_plaintext = ( "How do you doo?" );
my $passphrase = "Three Little Pigs";
my $gnupg = GnuPG::Interface->new();
$gnupg->options->hash_init( armor => 1,
recipients => [ 'ftobin@uiuc.edu',
'0xABCD1234ABCD1234ABCD1234ABCD1234ABCD1234' ],
meta_interactive => 0 ,
);
$gnupg->options->debug_level(4);
$gnupg->options->logger_file("/tmp/gnupg-$$-decrypt-".time().".log");
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;
FAQ
How do I get GnuPG::Interface to read/write directly from a filehandle?
You need to set GnuPG::Handles direct option to be true for the filehandles in concern. See
"options" in GnuPG::Handles and "Object Methods which use a GnuPG::Handles Object" for more
information.
Why do you make it so difficult to get GnuPG to write/read from a filehandle? In the shell, I can just
call GnuPG with the --outfile option!
There are lots of issues when trying to tell GnuPG to read/write directly from a file, such as if the
file isn't there, or there is a file, and you want to write over it! What do you want to happen
then? Having the user of this module handle these questions beforehand by opening up filehandles to
GnuPG lets the user know fully what is going to happen in these circumstances, and makes the module
less error-prone.
When having GnuPG process a large message, sometimes it just hanges there.
Your problem may be due to buffering issues; when GnuPG reads/writes to non-direct filehandles (those
that are sent to filehandles which you read to from into memory, not that those access the disk),
buffering issues can mess things up. I recommend looking into "options" in GnuPG::Handles.
NOTES
This package is the successor to PGP::GPG::MessageProcessor, which I found to be too inextensible to
carry on further. A total redesign was needed, and this is the resulting work.
After any call to a GnuPG-command method of GnuPG::Interface in which one passes in the handles, one
should all wait to clean up GnuPG from the process table.
BUGS
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.
SEE ALSO
GnuPG::Options, GnuPG::Handles, GnuPG::PublicKey, GnuPG::SecretKey, gpg, "Bidirectional Communication
with Another Process" in perlipc
LICENSE
This module is free software; you can redistribute it and/or modify it under the same terms as Perl
itself.
AUTHOR
GnuPG::Interface is currently maintained by Best Practical Solutions <BPS@cpan.org>.
Frank J. Tobin, ftobin@cpan.org was the original author of the package.
perl v5.36.0 2023-12-15 GnuPG::Interface(3pm)