=encoding utf8

=head1 NAME

perldelta - what is new for perl v5.22.3

=head1 DESCRIPTION

This document describes differences between the 5.22.2 release and the 5.22.3
release.

If you are upgrading from an earlier release such as 5.22.1, first read
L<perl5222delta>, which describes differences between 5.22.1 and 5.22.2.

=head1 Security

=head2 B<-Di> switch is now required for PerlIO debugging output

Previously PerlIO debugging output would be sent to the file specified by the
C<PERLIO_DEBUG> environment variable if perl wasn't running setuid and the
B<-T> or B<-t> switches hadn't been parsed yet.

If perl performed output at a point where it hadn't yet parsed its switches
this could result in perl creating or overwriting the file named by
C<PERLIO_DEBUG> even when the B<-T> switch had been supplied.

Perl now requires the B<-Di> switch to produce PerlIO debugging output.  By
default this is written to C<stderr>, but can optionally be redirected to a
file by setting the C<PERLIO_DEBUG> environment variable.

If perl is running setuid or the B<-T> switch was supplied C<PERLIO_DEBUG> is
ignored and the debugging output is sent to C<stderr> as for any other B<-D>
switch.

=head2 Core modules and tools no longer search F<"."> for optional modules

The tools and many modules supplied in core no longer search the default
current directory entry in L<C<@INC>|perlvar/@INC> for optional modules.  For
example, L<Storable> will remove the final F<"."> from C<@INC> before trying to
load L<Log::Agent>.

This prevents an attacker injecting an optional module into a process run by
another user where the current directory is writable by the attacker, e.g. the
F</tmp> directory.

In most cases this removal should not cause problems, the exception being
L<base>.

L<base> treats every module name supplied as optional.  If you have
applications that use L<base> to load non-optional modules from the current
directory you will need to modify your code or environment.

If your code always trusts the contents of the current directory, the simplest
change is adding F<"."> to C<PERL5LIB>:

  # for Bourne shell and similar
  set PERL5LIB=.
  export PERL5LIB

If you do B<not> trust the current directory this will open your code up to
attacks on any module load, not just optional modules.  You may want to add the
absolute path of your application's module directory to C<PERL5LIB> instead.

Alternatively, you can change your code, either to add the directory with your
binary to C<@INC>:

  use FindBin;
  use lib $FindBin::Bin;

or switch to L<parent>, which requires an explicit parameter for optional
modules:

  use parent 'Nonoptional::Module';

though this will have the same problem if the current directory is removed from
C<@INC> in Perl 5.26.

Also, since L<base> now localizes C<@INC> when loading modules, changes to
C<@INC> in the loaded module will be discarded when C<@INC> is restored to its
previous value.

To protect your own code from this attack, either remove the default F<".">
entry from C<@INC> at the start of your script, so:

  #!/usr/bin/perl
  use strict;
  ...

becomes:

  #!/usr/bin/perl
  BEGIN { pop @INC if $INC[-1] eq '.' }
  use strict;
  ...

or for modules, remove F<"."> from a localized C<@INC>, so:

  my $can_foo = eval { require Foo; }

becomes:

  my $can_foo = eval {
      local @INC = @INC;
      pop @INC if $INC[-1] eq '.';
      require Foo;
  };

=head1 Incompatible Changes

Other than the security changes above there are no changes intentionally
incompatible with Perl 5.22.2.  If any exist, they are bugs, and we request
that you submit a report.  See L</Reporting Bugs> below.

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<Archive::Tar> has been upgraded from version 2.04 to 2.04_01.

=item *

L<base> has been upgraded from version 2.22 to 2.22_01.

=item *

L<bignum> has been upgraded from version 0.39 to 0.39_01.

=item *

L<CPAN> has been upgraded from version 2.11 to 2.11_01.

=item *

L<Digest> has been upgraded from version 1.17 to 1.17_01.

=item *

L<Digest::SHA> has been upgraded from version 5.95 to 5.95_01.

=item *

L<Encode> has been upgraded from version 2.72 to 2.72_01.

=item *

L<ExtUtils::Command> has been upgraded from version 1.20 to 1.20_01.

=item *

L<ExtUtils::MakeMaker> has been upgraded from version 7.04_01 to 7.04_02.

=item *

L<File::Fetch> has been upgraded from version 0.48 to 0.48_01.

=item *

L<File::Spec> has been upgraded from version 3.56_01 to 3.56_02.

=item *

L<HTTP::Tiny> has been upgraded from version 0.054 to 0.054_01.

=item *

L<IO> has been upgraded from version 1.35 to 1.35_01.

=item *

The IO-Compress modules have been upgraded from version 2.068 to 2.068_001.

=item *

L<IPC::Cmd> has been upgraded from version 0.92 to 0.92_01.

=item *

L<JSON::PP> has been upgraded from version 2.27300 to 2.27300_01.

=item *

L<Locale::Maketext> has been upgraded from version 1.26 to 1.26_01.

=item *

L<Locale::Maketext::Simple> has been upgraded from version 0.21 to 0.21_01.

=item *

L<Memoize> has been upgraded from version 1.03 to 1.03_01.

=item *

L<Module::CoreList> has been upgraded from version 5.20160429 to 5.20160730_22.

=item *

L<Net::Ping> has been upgraded from version 2.43 to 2.43_01.

=item *

L<Pod::Html> has been upgraded from version 1.22 to 1.2201.

=item *

L<Pod::Perldoc> has been upgraded from version 3.25 to 3.25_01.

=item *

L<Storable> has been upgraded from version 2.53_01 to 2.53_02.

=item *

L<Sys::Syslog> has been upgraded from version 0.33 to 0.33_01.

=item *

L<Test> has been upgraded from version 1.26 to 1.26_01.

=item *

L<Test::Harness> has been upgraded from version 3.35 to 3.35_01.

=item *

L<XSLoader> has been upgraded from version 0.20 to 0.20_01, fixing a security
hole in which binary files could be loaded from a path outside of C<@INC>.
L<[perl #128528]|https://rt.perl.org/Public/Bug/Display.html?id=128528>

=back

=head1 Documentation

=head2 Changes to Existing Documentation

=head3 L<perlapio>

=over 4

=item *

The documentation of C<PERLIO_DEBUG> has been updated.

=back

=head3 L<perlrun>

=over 4

=item *

The new B<-Di> switch has been documented, and the documentation of
C<PERLIO_DEBUG> has been updated.

=back

=head1 Testing

=over 4

=item *

A new test script, F<t/run/switchDx.t>, has been added to test that the new
B<-Di> switch is working correctly.

=back

=head1 Selected Bug Fixes

=over 4

=item *

The C<PadlistNAMES> macro is an lvalue again.

=back

=head1 Acknowledgements

Perl 5.22.3 represents approximately 3 months of development since Perl 5.22.2
and contains approximately 3,300 lines of changes across 240 files from 16
authors.

Excluding auto-generated files, documentation and release tools, there were
approximately 1,400 lines of changes to 170 .pm, .t, .c and .h files.

Perl continues to flourish into its third decade thanks to a vibrant community
of users and developers.  The following people are known to have contributed
the improvements that became Perl 5.22.3:

Abigail, Alex Vandiver, Aristotle Pagaltzis, Craig A. Berry, David Mitchell,
Father Chrysostomos, James E Keenan, Karen Etheridge, Karl Williamson, Matthew
Horsfall, Niko Tyni, Ricardo Signes, Sawyer X, Stevan Little, Steve Hay, Tony
Cook.

The list above is almost certainly incomplete as it is automatically generated
from version control history.  In particular, it does not include the names of
the (very much appreciated) contributors who reported issues to the Perl bug
tracker.

Many of the changes included in this version originated in the CPAN modules
included in Perl's core.  We're grateful to the entire CPAN community for
helping Perl to flourish.

For a more complete list of all of Perl's historical contributors, please see
the F<AUTHORS> file in the Perl source distribution.

=head1 Reporting Bugs

If you find what you think is a bug, you might check the articles recently
posted to the comp.lang.perl.misc newsgroup and the Perl bug database at
https://rt.perl.org/ .  There may also be information at http://www.perl.org/ ,
the Perl Home Page.

If you believe you have an unreported bug, please run the L<perlbug> program
included with your release.  Be sure to trim your bug down to a tiny but
sufficient test case.  Your bug report, along with the output of C<perl -V>,
will be sent off to perlbug@perl.org to be analysed by the Perl porting team.

If the bug you are reporting has security implications, which make it
inappropriate to send to a publicly archived mailing list, then please send it
to perl5-security-report@perl.org.  This points to a closed subscription
unarchived mailing list, which includes all the core committers, who will be
able to help assess the impact of issues, figure out a resolution, and help
co-ordinate the release of patches to mitigate or fix the problem across all
platforms on which Perl is supported.  Please only use this address for
security issues in the Perl core, not for modules independently distributed on
CPAN.

=head1 SEE ALSO

The F<Changes> file for an explanation of how to view exhaustive details on
what changed.

The F<INSTALL> file for how to build Perl.

The F<README> file for general stuff.

The F<Artistic> and F<Copying> files for copyright information.

=cut
