NAME

       Module::Signature - Module signature file manipulation

SYNOPSIS

       As a shell command:

           % cpansign              # verify an existing SIGNATURE, or
                                   # make a new one if none exists

           % cpansign sign         # make signature; overwrites existing one
           % cpansign -s           # same thing

           % cpansign verify       # verify a signature
           % cpansign -v           # same thing
           % cpansign -v --skip    # ignore files in MANIFEST.SKIP

           % cpansign help         # display this documentation
           % cpansign -h           # same thing

       In programs:

           use Module::Signature qw(sign verify SIGNATURE_OK);
           sign();
           sign(overwrite => 1);       # overwrites without asking

           # see the CONSTANTS section below
           (verify() == SIGNATURE_OK) or die "failed!";

DESCRIPTION

       Module::Signature adds cryptographic authentications to CPAN distributions, via the
       special SIGNATURE file.

       If you are a module user, all you have to do is to remember to run "cpansign -v" (or just
       "cpansign") before issuing "perl Makefile.PL" or "perl Build.PL"; that will ensure the
       distribution has not been tampered with.

       Module authors can easily add the SIGNATURE file to the distribution tarball; see "NOTES"
       below for how to do it as part of "make dist".

       If you really want to sign a distribution manually, simply add "SIGNATURE" to MANIFEST,
       then type "cpansign -s" immediately before "make dist".  Be sure to delete the SIGNATURE
       file afterwards.

       Please also see "NOTES" about MANIFEST.SKIP issues, especially if you are using
       Module::Build or writing your own MANIFEST.SKIP.

VARIABLES

       No package variables are exported by default.

       $Verbose
           If true, Module::Signature will give information during processing including gpg
           output.  If false, Module::Signature will be as quiet as possible as long as
           everything is working ok.  Defaults to false.

       $SIGNATURE
           The filename for a distribution's signature file.  Defaults to "SIGNATURE".

       $KeyServer
           The OpenPGP key server for fetching the author's public key (currently only
           implemented on "gpg", not "Crypt::OpenPGP").  May be set to a false value to prevent
           this module from fetching public keys.

       $KeyServerPort
           The OpenPGP key server port, defaults to 11371.

       $Timeout
           Maximum time to wait to try to establish a link to the key server.  Defaults to 3.

       $AutoKeyRetrieve
           Whether to automatically fetch unknown keys from the key server.  Defaults to 1.

       $Cipher
           The default cipher used by the "Digest" module to make signature files.  Defaults to
           "SHA1", but may be changed to other ciphers via the "MODULE_SIGNATURE_CIPHER"
           environment variable if the SHA1 cipher is undesirable for the user.

           The cipher specified in the SIGNATURE file's first entry will be used to validate its
           integrity.  For "SHA1", the user needs to have any one of these four modules
           installed: Digest::SHA, Digest::SHA1, Digest::SHA::PurePerl, or (currently
           nonexistent) Digest::SHA1::PurePerl.

       $Preamble
           The explanatory text written to newly generated SIGNATURE files before the actual
           entries.

ENVIRONMENT

       Module::Signature honors these environment variables:

       MODULE_SIGNATURE_CIPHER
           Works like $Cipher.

       MODULE_SIGNATURE_VERBOSE
           Works like $Verbose.

       MODULE_SIGNATURE_KEYSERVER
           Works like $KeyServer.

       MODULE_SIGNATURE_KEYSERVERPORT
           Works like $KeyServerPort.

       MODULE_SIGNATURE_TIMEOUT
           Works like $Timeout.

CONSTANTS

       These constants are not exported by default.

       CANNOT_VERIFY (0E0)
           Cannot verify the OpenPGP signature, maybe due to the lack of a network connection to
           the key server, or if neither gnupg nor Crypt::OpenPGP exists on the system.

       SIGNATURE_OK (0)
           Signature successfully verified.

       SIGNATURE_MISSING ("-1")
           The SIGNATURE file does not exist.

       SIGNATURE_MALFORMED ("-2")
           The signature file does not contains a valid OpenPGP message.

       SIGNATURE_BAD ("-3")
           Invalid signature detected -- it might have been tampered with.

       SIGNATURE_MISMATCH ("-4")
           The signature is valid, but files in the distribution have changed since its creation.

       MANIFEST_MISMATCH ("-5")
           There are extra files in the current directory not specified by the MANIFEST file.

       CIPHER_UNKNOWN ("-6")
           The cipher used by the signature file is not recognized by the "Digest" and
           "Digest::*" modules.

NOTES

   Signing your module as part of "make dist"
       The easiest way is to use Module::Install:

           sign;       # put this before "WriteAll"
           WriteAll;

       For ExtUtils::MakeMaker (version 6.18 or above), you may do this:

           WriteMakefile(
               (MM->can('signature_target') ? (SIGN => 1) : ()),
               # ... original arguments ...
           );

       Users of Module::Build may do this:

           Module::Build->new(
               (sign => 1),
               # ... original arguments ...
           )->create_build_script;

   MANIFEST.SKIP Considerations
       (The following section is lifted from Iain Truskett's Test::Signature module, under the
       Perl license.  Thanks, Iain!)

       It is imperative that your MANIFEST and MANIFEST.SKIP files be accurate and complete. If
       you are using "ExtUtils::MakeMaker" and you do not have a MANIFEST.SKIP file, then don't
       worry about the rest of this. If you do have a MANIFEST.SKIP file, or you use
       "Module::Build", you must read this.

       Since the test is run at "make test" time, the distribution has been made. Thus your
       MANIFEST.SKIP file should have the entries listed below.

       If you're using "ExtUtils::MakeMaker", you should have, at least:

           #defaults
           ^Makefile$
           ^blib/
           ^pm_to_blib
           ^blibdirs

       These entries are part of the default set provided by "ExtUtils::Manifest", which is
       ignored if you provide your own MANIFEST.SKIP file.

       If you are using "Module::Build", you should have two extra entries:

           ^Build$
           ^_build/

       If you don't have the correct entries, "Module::Signature" will complain that you have:

           ==> MISMATCHED content between MANIFEST and distribution files! <==

       You should note this during normal development testing anyway.

   Testing signatures
       You may add this code as t/0-signature.t in your distribution tree:

           #!/usr/bin/perl

           use strict;
           print "1..1\n";

           if (!$ENV{TEST_SIGNATURE}) {
               print "ok 1 # skip Set the environment variable",
                           " TEST_SIGNATURE to enable this test\n";
           }
           elsif (!-s 'SIGNATURE') {
               print "ok 1 # skip No signature file found\n";
           }
           elsif (!eval { require Module::Signature; 1 }) {
               print "ok 1 # skip ",
                       "Next time around, consider install Module::Signature, ",
                       "so you can verify the integrity of this distribution.\n";
           }
           elsif (!eval { require Socket; Socket::inet_aton('pool.sks-keyservers.net') }) {
               print "ok 1 # skip ",
                       "Cannot connect to the keyserver\n";
           }
           else {
               (Module::Signature::verify() == Module::Signature::SIGNATURE_OK())
                   or print "not ";
               print "ok 1 # Valid signature\n";
           }

           __END__

       If you are already using Test::More for testing, a more straightforward version of
       t/0-signature.t can be found in the Module::Signature distribution.

       Also, if you prefer a more full-fledged testing package, and are willing to inflict the
       dependency of Module::Build on your users, Iain Truskett's Test::Signature might be a
       better choice.

SEE ALSO

       Digest, Digest::SHA, Digest::SHA1, Digest::SHA::PurePerl

       ExtUtils::Manifest, Crypt::OpenPGP, Test::Signature

       Module::Install, ExtUtils::MakeMaker, Module::Build

       Dist::Zilla::Plugin::Signature

AUTHORS

       XX <cpan@audreyt.org>

CC0 1.0 Universal

       To the extent possible under law, XX has waived all copyright and related or neighboring
       rights to Module-Signature.

       This work is published from Taiwan.

       <http://creativecommons.org/publicdomain/zero/1.0>