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[perl #132739] bignum upgrade/downgrade path bug

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From:
Gabriel Withington
Date:
January 21, 2018 00:31
Subject:
[perl #132739] bignum upgrade/downgrade path bug
Message ID:
rt-4.0.24-31427-1516319879-780.132739-75-0@perl.org
# New Ticket Created by  Gabriel Withington 
# Please include the string:  [perl #132739]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=132739 >


This is a bug report for perl from gabriel.withington@gmail.com,
generated with the help of perlbug 1.40 running under perl 5.22.1.

Two integers ($a and $b) passed to a subroutine and then with the operation
$a % $b performed on them produces the following error:

Can't use an undefined value as an ARRAY reference at
/usr/share/perl/5.22/Math/BigInt/Calc.pm line 1359.

I've attached a script which demonstrates the problem, it is fixed by
adding an int() cast to lines 173 and 174.

Gabriel

P.S. The script might be of interest generally. It takes a semiprime and an
encryption exponent, the two components of an RSA public key, and
calculates an exponent which can be used to decrypt data for that key
(well, for the cipher text used). It's an interesting approach which skips
semiprimes and looks like the lower limit of time as a function of key
length may be linear. It's all very exciting and so far my efforts have
been pooh-pooh-ed by Bruce Schneier and Niels Ferguson.

---
Flags:
    category=library
    severity=low
    module=Math::BigInt
---
Site configuration information for perl 5.22.1:

Configured by Debian Project at Fri Nov 10 14:39:06 UTC 2017.

Summary of my perl5 (revision 5 version 22 subversion 1) configuration:

  Platform:
    osname=linux, osvers=3.16.0, archname=x86_64-linux-gnu-thread-multi
    uname='linux localhost 3.16.0 #1 smp debian 3.16.0 x86_64 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dcc=x86_64-linux-gnu-gcc
-Dcpp=x86_64-linux-gnu-cpp -Dld=x86_64-linux-gnu-gcc -Dccflags=-DDEBIAN
-Wdate-time -D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector-strong -Wformat
-Werror=format-security -Dldflags= -Wl,-Bsymbolic-functions -Wl,-z,relro
-Dlddlflags=-shared -Wl,-Bsymbolic-functions -Wl,-z,relro
-Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr
-Dprivlib=/usr/share/perl/5.22
-Darchlib=/usr/lib/x86_64-linux-gnu/perl/5.22 -Dvendorprefix=/usr
-Dvendorlib=/usr/share/perl5
-Dvendorarch=/usr/lib/x86_64-linux-gnu/perl5/5.22 -Dsiteprefix=/usr/local
-Dsitelib=/usr/local/share/perl/5.22.1
-Dsitearch=/usr/local/lib/x86_64-linux-gnu/perl/5.22.1
-Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3
-Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3
-Duse64bitint -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager
-Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -Ui_libutil -Uversiononly
-DDEBUGGING=-g -Doptimize=-O2 -dEs -Duseshrplib -Dlibperl=libperl.so.5.22.1'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='x86_64-linux-gnu-gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE
-DDEBIAN -fwrapv -fno-strict-aliasing -pipe -I/usr/local/include
-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fwrapv
-fno-strict-aliasing -pipe -I/usr/local/include'
    ccversion='', gccversion='5.4.0 20160609', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678,
doublekind=3
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16,
longdblkind=3
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t',
lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='x86_64-linux-gnu-gcc', ldflags =' -fstack-protector-strong
-L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/5/include-fixed
/usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu /lib/../lib
/usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=libc-2.23.so, so=so, useshrplib=true, libperl=libperl.so.5.22
    gnulibc_version='2.23'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib
-fstack-protector-strong'

Locally applied patches:
    DEBPKG:debian/cpan_definstalldirs - Provide a sensible INSTALLDIRS
default for modules installed from CPAN.
    DEBPKG:debian/db_file_ver - http://bugs.debian.org/340047 Remove overly
restrictive DB_File version check.
    DEBPKG:debian/doc_info - Replace generic man(1) instructions with
Debian-specific information.
    DEBPKG:debian/enc2xs_inc - http://bugs.debian.org/290336 Tweak enc2xs
to follow symlinks and ignore missing @INC directories.
    DEBPKG:debian/errno_ver - http://bugs.debian.org/343351 Remove Errno
version check due to upgrade problems with long-running processes.
    DEBPKG:debian/libperl_embed_doc - http://bugs.debian.org/186778 Note
that libperl-dev package is required for embedded linking
    DEBPKG:fixes/respect_umask - Respect umask during installation
    DEBPKG:debian/writable_site_dirs - Set umask approproately for site
install directories
    DEBPKG:debian/extutils_set_libperl_path - EU:MM: set location of
libperl.a under /usr/lib
    DEBPKG:debian/no_packlist_perllocal - Don't install .packlist or
perllocal.pod for perl or vendor
    DEBPKG:debian/fakeroot - Postpone LD_LIBRARY_PATH evaluation to the
binary targets.
    DEBPKG:debian/instmodsh_doc - Debian policy doesn't install .packlist
files for core or vendor.
    DEBPKG:debian/ld_run_path - Remove standard libs from LD_RUN_PATH as
per Debian policy.
    DEBPKG:debian/libnet_config_path - Set location of libnet.cfg to
/etc/perl/Net as /usr may not be writable.
    DEBPKG:debian/mod_paths - Tweak @INC ordering for Debian
    DEBPKG:debian/prune_libs - http://bugs.debian.org/128355 Prune the list
of libraries wanted to what we actually need.
    DEBPKG:fixes/net_smtp_docs - [rt.cpan.org #36038]
http://bugs.debian.org/100195 Document the Net::SMTP 'Port' option
    DEBPKG:debian/perlivp - http://bugs.debian.org/510895 Make perlivp skip
include directories in /usr/local
    DEBPKG:debian/deprecate-with-apt - http://bugs.debian.org/747628 Point
users to Debian packages of deprecated core modules
    DEBPKG:debian/squelch-locale-warnings - http://bugs.debian.org/508764
Squelch locale warnings in Debian package maintainer scripts
    DEBPKG:debian/skip-upstream-git-tests - Skip tests specific to the
upstream Git repository
    DEBPKG:debian/patchlevel - http://bugs.debian.org/567489 List packaged
patches for 5.22.1-9ubuntu0.2 in patchlevel.h
    DEBPKG:debian/skip-kfreebsd-crash - http://bugs.debian.org/628493 [perl
#96272] Skip a crashing test case in t/op/threads.t on GNU/kFreeBSD
    DEBPKG:fixes/document_makemaker_ccflags - http://bugs.debian.org/628522
[rt.cpan.org #68613] Document that CCFLAGS should include $Config{ccflags}
    DEBPKG:debian/find_html2text - http://bugs.debian.org/640479 Configure
CPAN::Distribution with correct name of html2text
    DEBPKG:debian/perl5db-x-terminal-emulator.patch -
http://bugs.debian.org/668490 Invoke x-terminal-emulator rather than xterm
in perl5db.pl
    DEBPKG:debian/cpan-missing-site-dirs - http://bugs.debian.org/688842
Fix CPAN::FirstTime defaults with nonexisting site dirs if a parent is
writable
    DEBPKG:fixes/memoize_storable_nstore - [rt.cpan.org #77790]
http://bugs.debian.org/587650 Memoize::Storable: respect 'nstore' option
not respected
    DEBPKG:debian/regen-skip - Skip a regeneration check in unrelated git
repositories
    DEBPKG:debian/makemaker-pasthru - http://bugs.debian.org/758471 Pass LD
settings through to subdirectories
    DEBPKG:fixes/pod_man_reproducible_date - http://bugs.debian.org/759405
Support POD_MAN_DATE in Pod::Man for the left-hand footer
    DEBPKG:debian/locale-robustness - http://bugs.debian.org/782068 [perl
#124310] Make t/run/locale.t survive missing locales masked by LC_ALL
    DEBPKG:fixes/podman-utc - http://bugs.debian.org/780259 Make the
embedded date from Pod::Man reproducible
    DEBPKG:fixes/podman-utc-docs - http://bugs.debian.org/780259
Documentation and test suite updates for UTC fix
    DEBPKG:fixes/podman-empty-date - http://bugs.debian.org/780259 Support
an empty POD_MAN_DATE environment variable
    DEBPKG:fixes/podman-pipe - http://bugs.debian.org/777405 Better errors
for man pages from standard input
    DEBPKG:debian/pod2man-customized - Update porting/customized.dat for
pod2man modifications
    DEBPKG:debian/makemaker-manext - http://bugs.debian.org/247370 Make
EU::MakeMaker honour MANnEXT settings in generated manpage headers
    DEBPKG:debian/makemaker_customized - Update t/porting/customized.dat
for files patched in Debian
    DEBPKG:debian/do-not-record-build-date - [6baa8db]
http://bugs.debian.org/774422 [perl #125830] Allow overriding the compile
time in "perl -V" output
    DEBPKG:fixes/podman-source-date-epoch - http://bugs.debian.org/801621
Make Pod::Man honor the SOURCE_DATE_EPOCH environment variable
    DEBPKG:fixes/podman-source-date-epoch-cleanups -
http://bugs.debian.org/801621 Coding style and documentation for
SOURCE_EPOCH_DATE
    DEBPKG:fixes/podman-source-date-epoch-testfix -
http://bugs.debian.org/807086 Guard for building with SOURCE_DATE_EPOCH or
POD_MAN_DATE set
    DEBPKG:debian/devel-ppport-reproducibility -
http://bugs.debian.org/801523 Sort the list of XS code files when
generating RealPPPort.xs
    DEBPKG:fixes/encode-unicode-bom - http://bugs.debian.org/798727 [
rt.cpan.org #107043] Address
https://rt.cpan.org/Public/Bug/Display.html?id=107043
    DEBPKG:debian/encode-unicode-bom-doc - http://bugs.debian.org/798727
Document Debian backport of Encode::Unicode fix
    DEBPKG:debian/kfreebsd-softupdates - http://bugs.debian.org/796798 Work
around Debian Bug#796798
    DEBPKG:fixes/autodie-scope - http://bugs.debian.org/798096 Fix a
scoping issue with "no autodie" and the "system" sub
    DEBPKG:debian/debugperl-compat-fix - [perl #127212]
http://bugs.debian.org/810326 Disable PERL_TRACK_MEMPOOL for debugging
builds
    DEBPKG:fixes/CVE-2015-8607_file_spec_taint_fix -
http://bugs.debian.org/810719 [perl #126862] ensure File::Spec::canonpath()
preserves taint
    DEBPKG:fixes/mkstemp-umask - http://bugs.debian.org/810924 [perl
#127322] [e57270b] Fix umask for mkstemp(3) calls
    DEBPKG:fixes/crosscompile-no-targethost - [perl #127234] Fix the
Configure escape with usecrosscompile but no targethost
    DEBPKG:fixes/podlators-no-encode - [rt.cpan.org #111156] Degrade
gracefully if utf8 is requested but Encode is not available
    DEBPKG:debian/cross-time-hires - [rt.cpan.org #111391] Add an
environment variable to skip running configuration probes
    DEBPKG:fixes/encode-unicode-pod - Unicode.pm: Fix POD error
    DEBPKG:fixes/memoize-pod - [rt.cpan.org #89441] Fix POD errors in
Memoize
    DEBPKG:fixes/ok-pod - Added encoding for pod.
    DEBPKG:fixes/CVE-2016-2381_duplicate_env - remove duplicate environment
variables from environ
    DEBPKG:fixes/CVE-2017-12837.patch - [PATCH] regcomp [perl #131582]
    DEBPKG:fixes/CVE-2017-12883.patch - [PATCH] PATCH: [perl #131598]

---
@INC for perl 5.22.1:
    /etc/perl
    /usr/local/lib/x86_64-linux-gnu/perl/5.22.1
    /usr/local/share/perl/5.22.1
    /usr/lib/x86_64-linux-gnu/perl5/5.22
    /usr/share/perl5
    /usr/lib/x86_64-linux-gnu/perl/5.22
    /usr/share/perl/5.22
    /usr/local/lib/site_perl
    /usr/lib/x86_64-linux-gnu/perl-base
    .

---
Environment for perl 5.22.1:
    HOME=/home/gabrielw
    LANG=en_US.UTF-8
    LANGUAGE=en_US
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)

PATH=/home/gabrielw/bin:/home/gabrielw/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
    PERL_BADLANG (unset)
    SHELL=/bin/bash

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