perl5241delta - what is new for perl v5.24.1

NAME

perl5241delta - what is new for perl v5.24.1

DESCRIPTION

This document describes differences between the 5.24.0 release and the 5.24.1 release.

If you are upgrading from an earlier release such as 5.22.0, first read the perl5240delta manpage, which describes differences between 5.22.0 and 5.24.0.

Security

-Di switch is now required for PerlIO debugging output

Previously PerlIO debugging output would be sent to the file specified by the PERLIO_DEBUG environment variable if perl wasn't running setuid and the -T or -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 PERLIO_DEBUG even when the -T switch had been supplied.

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

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

Core modules and tools no longer search ``.'' for optional modules

The tools and many modules supplied in core no longer search the default current directory entry in @INC for optional modules. For example, the Storable manpage will remove the final ``.'' from @INC before trying to load the Log::Agent manpage.

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 /tmp directory.

In most cases this removal should not cause problems, but difficulties were encountered with the base manpage, which treats every module name supplied as optional. These difficulties have not yet been resolved, so for this release there are no changes to the base manpage. We hope to have a fix for the base manpage in Perl 5.24.2.

To protect your own code from this attack, either remove the default ``.'' entry from @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 ``.'' from a localized @INC, so:

  my $can_foo = eval { require Foo; }

becomes:

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

Incompatible Changes

Other than the security changes above there are no changes intentionally incompatible with Perl 5.24.0. If any exist, they are bugs, and we request that you submit a report. See Reporting Bugs below.

Modules and Pragmata

Updated Modules and Pragmata

Documentation

Changes to Existing Documentation

the perlapio manpage

the perlrun manpage

Testing

Selected Bug Fixes

Acknowledgements

Perl 5.24.1 represents approximately 8 months of development since Perl 5.24.0 and contains approximately 8,100 lines of changes across 240 files from 18 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 2,200 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 5.24.1:

Aaron Crane, Alex Vandiver, Aristotle Pagaltzis, Chad Granum, Chris 'BinGOs' Williams, Craig A. Berry, Father Chrysostomos, James E Keenan, Jarkko Hietaniemi, Karen Etheridge, Leon Timmermans, Matthew Horsfall, Ricardo Signes, Sawyer X, Sébastien Aperghis-Tramoni, 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 AUTHORS file in the Perl source distribution.

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 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 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 see SECURITY VULNERABILITY CONTACT INFORMATION in the perlsec manpage for details of how to report the issue.

SEE ALSO

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

The INSTALL file for how to build Perl.

The README file for general stuff.

The Artistic and Copying files for copyright information.

 perl5241delta - what is new for perl v5.24.1