Re: FW: Localizing %SIG in Safe.pm 2.{35,36,37} crashes POE::Wheel::Run ...

Hi all
Breaking out a Safe compartment is all about compiling code that will
be executed later. It happens that there are working exploits that use
a combination of %SIG and eval inside the safe-evaled block to execute
such compilations; then arbitrary commands can be run on any signal
received by the process that compiled the safe compartment.

(I repeat it again -- without this fix it's possible to make perl
execute `rm -fr /` through code passed to Safe. So the fix stays.)

The fix I put in Safe was to simply wipe out %SIG in the Safe
compartment. In theory that should not have been necessary, since %SIG
is not shared between %main:: and the Safe root stash, but that's
apparently not how the perl internals work; so, to have a fix
back-portable to older perls, I did not found any other way. If
someone wants to investigate, I'll be happy to provide details...

Also I'd like to understand why you need to set signal handlers in a
Safe compartment. As far as I can tell this has only ever worked by
accident.

On 16 July 2013 18:00, Markus Jansen <[email protected]> wrote:
> Hi,
>
> FYI ... hope none of you wastes time with this really nasty trap ...
>
> Best regards,
>         Markus
>
> -----Original Message-----
> From: Markus Jansen
> Sent: Tuesday, July 16, 2013 5:57 PM
> To: [email protected]
> Cc: Markus Jansen
> Subject: Localizing %SIG in Safe.pm 2.{35,36,37} crashes POE::Wheel::Run =
...
>
>
> This is a bug report for perl from [email protected], generated =
with the help of perlbug 1.39 running under perl 5.18.0.
>
>
> -----------------------------------------------------------------
> [Please describe your issue here]
>
> Dear Perl5 Porters,
>
> localizing %SIG in Safe.pm 2.35 (on CPAN, 2.{35,36,37} in Perl core) may =
be a great step for security, but it unfortunatately spoils POE::Wheel::Run=
 (basically POE and all other asynchronous frameworks dealing with external=
 processes).
>
> The symptom experienced is that your application might sooner or later cr=
ash (reliably when using POE::Component::Resolver upon exiting a Sidecar su=
bprocess) with the following famous last words:
>
>         Signal SIGCHLD received, but no signal handler set.
>
> Please consider a version (also on CPAN) of Safe.pm which has e.g. the lo=
calization of %SIG as a switchable feature.
>
> Best regards,
>         Markus
>
>
>
> [Please do not change anything below this line]
> -----------------------------------------------------------------
> ---
> Flags:
>     category=3Dlibrary
>     severity=3Dcritical
>     module=3DSafe
> ---
> Site configuration information for perl 5.18.0:
>
> Configured by ericsson at Fri Jul 12 19:17:48 CEST 2013.
>
> Summary of my perl5 (revision 5 version 18 subversion 0) configuration:
>
>   Platform:
>     osname=3Dlinux, osvers=3D2.6.16.60-0.42.10-smp, archname=3Dx86_64-lin=
ux-thread-multi
>     uname=3D'linux sekix562 2.6.16.60-0.42.10-smp #1 smp tue apr 27 05:11=
:27 utc 2010 x86_64 x86_64 x86_64 gnulinux '
>     config_args=3D'-d -e -O -D cc=3Dgcc -D prefix=3D/vobs/cc/CCA-perl01/p=
erl5_Linux_x64__________sixtyfive_char_path/prod -D usemultiplicity -U use5=
005threads -D usedl -D useshrplib -D libperl=3Dlibcmacperl.so -U usemymallo=
c -D cf_by=3Dericsson -D [email protected] -D perladm=
[email protected] -D uselargefiles -D usethreads -D useithr=
eads -D use64bitall -D ldcc=3DCC -D optimize=3D-O3 -D locincpth=3D/vobs/cc/=
CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/plib/include /vobs/=
cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/plib/apache/incl=
ude -D loclibpth=3D/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_c=
har_path/plib/lib /vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_ch=
ar_path/plib/apache/lib -D lddlflags=3D-shared -lpthread -Wl,-L/vobs/cc/CCA=
-perl01/perl5_Linux_x64__________sixtyfive_char_path/prod/lib/5.18.0/x86_64=
-linux-thread-multi/CORE -Wl,-rpath,/vobs/cc/CCA-perl01/perl5_Linux_x64____=
______sixtyfive_char_path/prod/lib/5.18.0
>  /x86_64-linux-thread-multi/CORE -Wl,-L/vobs/cc/CCA-perl01/perl5_Linux_x6=
4__________sixtyfive_char_path/plib/lib -Wl,-rpath,/vobs/cc/CCA-perl01/perl=
5_Linux_x64__________sixtyfive_char_path/plib/lib -Wl,-L/vobs/cc/CCA-perl01=
/perl5_Linux_x64__________sixtyfive_char_path/plib/apache/lib -Wl,-rpath,/v=
obs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/plib/apache/=
lib -Wl,--enable-new-dtags -D ldflags=3D-lpthread -Wl,-L/vobs/cc/CCA-perl01=
/perl5_Linux_x64__________sixtyfive_char_path/prod/lib/5.18.0/x86_64-linux-=
thread-multi/CORE -Wl,-rpath,/vobs/cc/CCA-perl01/perl5_Linux_x64__________s=
ixtyfive_char_path/prod/lib/5.18.0/x86_64-linux-thread-multi/CORE -Wl,-L/vo=
bs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/plib/lib -Wl,=
-rpath,/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/pli=
b/lib -Wl,-L/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_pat=
h/plib/apache/lib -Wl,-rpath,/vobs/cc/CCA-perl01/perl5_Linux_x64__________s=
ixtyfive_char_path/
>  plib/apache/lib -Wl,--enable-new-dtags -D ccdlflags=3D-Bdynamic -Wl,-L/v=
obs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/prod/lib/5.1=
8.0/x86_64-linux-thread-multi/CORE -Wl,-rpath,/vobs/cc/CCA-perl01/perl5_Lin=
ux_x64__________sixtyfive_char_path/prod/lib/5.18.0/x86_64-linux-thread-mul=
ti/CORE -Wl,-L/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_p=
ath/plib/lib -Wl,-rpath,/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyf=
ive_char_path/plib/lib -Wl,-L/vobs/cc/CCA-perl01/perl5_Linux_x64__________s=
ixtyfive_char_path/plib/apache/lib -Wl,-rpath,/vobs/cc/CCA-perl01/perl5_Lin=
ux_x64__________sixtyfive_char_path/plib/apache/lib -D ldlibpthname=3DLD_LI=
BRARY_PATH -D cccdlflags=3D-fPIC -D dlsrc=3Ddl_dlopen.xs -D ccflags=3D-O2 -=
D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -pthread -DPERL_IMPLICIT_CONT=
EXT -DPERL_USE_SAFE_PUTENV -m64 -pipe -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BI=
TS=3D64 -fPIC -D so=3Dso -D libswanted=3Dnsl dl m crypt pthread c'
>     hint=3Drecommended, useposix=3Dtrue, d_sigaction=3Ddefine
>     useithreads=3Ddefine, usemultiplicity=3Ddefine
>     useperlio=3Ddefine, d_sfio=3Dundef, uselargefiles=3Ddefine, usesocks=
=3Dundef
>     use64bitint=3Ddefine, use64bitall=3Ddefine, uselongdouble=3Dundef
>     usemymalloc=3Dn, bincompat5005=3Dundef
>   Compiler:
>     cc=3D'gcc', ccflags =3D'-D_REENTRANT -D_GNU_SOURCE -O2 -D_REENTRANT -=
D_GNU_SOURCE -DTHREADS_HAVE_PIDS -pthread -DPERL_IMPLICIT_CONTEXT -DPERL_US=
E_SAFE_PUTENV -m64 -pipe -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=3D64 -fPIC=
 -fno-strict-aliasing -fstack-protector -I/vobs/cc/CCA-perl01/perl5_Linux_x=
64__________sixtyfive_char_path/plib/include -I/vobs/cc/CCA-perl01/perl5_Li=
nux_x64__________sixtyfive_char_path/plib/apache/include -D_LARGEFILE_SOURC=
E -D_FILE_OFFSET_BITS=3D64',
>     optimize=3D'-O3',
>     cppflags=3D'-D_REENTRANT -D_GNU_SOURCE -O2 -D_REENTRANT -D_GNU_SOURCE=
 -DTHREADS_HAVE_PIDS -pthread -DPERL_IMPLICIT_CONTEXT -DPERL_USE_SAFE_PUTEN=
V -m64 -pipe -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=3D64 -fPIC -fno-strict=
-aliasing -fstack-protector -I/vobs/cc/CCA-perl01/perl5_Linux_x64__________=
sixtyfive_char_path/plib/include -I/vobs/cc/CCA-perl01/perl5_Linux_x64_____=
_____sixtyfive_char_path/plib/apache/include'
>     ccversion=3D'', gccversion=3D'4.1.2 20070115 (SUSE Linux)', gccosandv=
ers=3D''
>     intsize=3D4, longsize=3D8, ptrsize=3D8, doublesize=3D8, byteorder=3D1=
2345678
>     d_longlong=3Ddefine, longlongsize=3D8, d_longdbl=3Ddefine, longdblsiz=
e=3D16
>     ivtype=3D'long', ivsize=3D8, nvtype=3D'double', nvsize=3D8, Off_t=3D'=
off_t', lseeksize=3D8
>     alignbytes=3D8, prototype=3Ddefine
>   Linker and Libraries:
>     ld=3D'gcc', ldflags =3D'-lpthread -Wl,-L/vobs/cc/CCA-perl01/perl5_Lin=
ux_x64__________sixtyfive_char_path/prod/lib/5.18.0/x86_64-linux-thread-mul=
ti/CORE -Wl,-rpath,/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_c=
har_path/prod/lib/5.18.0/x86_64-linux-thread-multi/CORE -Wl,-L/vobs/cc/CCA-=
perl01/perl5_Linux_x64__________sixtyfive_char_path/plib/lib -Wl,-rpath,/vo=
bs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/plib/lib -Wl,=
-L/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/plib/apa=
che/lib -Wl,-rpath,/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_c=
har_path/plib/apache/lib -Wl,--enable-new-dtags -fstack-protector'
>     libpth=3D/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_=
path/plib/lib /vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_p=
ath/plib/apache/lib /lib/../lib64 /usr/lib/../lib64 /lib /usr/lib /usr/loca=
l/lib /lib64 /usr/lib64 /usr/local/lib64
>     libs=3D-lnsl -ldl -lm -lcrypt -lpthread -lc
>     perllibs=3D-lnsl -ldl -lm -lcrypt -lpthread -lc
>     libc=3D/lib/libc-2.4.so, so=3Dso, useshrplib=3Dtrue, libperl=3Dlibcma=
cperl.so
>     gnulibc_version=3D'2.4'
>   Dynamic Linking:
>     dlsrc=3Ddl_dlopen.xs, dlext=3Dso, d_dlsymun=3Dundef, ccdlflags=3D'-Bd=
ynamic -Wl,-L/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_pa=
th/prod/lib/5.18.0/x86_64-linux-thread-multi/CORE -Wl,-rpath,/vobs/cc/CCA-p=
erl01/perl5_Linux_x64__________sixtyfive_char_path/prod/lib/5.18.0/x86_64-l=
inux-thread-multi/CORE -Wl,-L/vobs/cc/CCA-perl01/perl5_Linux_x64__________s=
ixtyfive_char_path/plib/lib -Wl,-rpath,/vobs/cc/CCA-perl01/perl5_Linux_x64_=
_________sixtyfive_char_path/plib/lib -Wl,-L/vobs/cc/CCA-perl01/perl5_Linux=
_x64__________sixtyfive_char_path/plib/apache/lib -Wl,-rpath,/vobs/cc/CCA-p=
erl01/perl5_Linux_x64__________sixtyfive_char_path/plib/apache/lib'
>     cccdlflags=3D'-fPIC', lddlflags=3D'-shared -lpthread -Wl,-L/vobs/cc/C=
CA-perl01/perl5_Linux_x64__________sixtyfive_char_path/prod/lib/5.18.0/x86_=
64-linux-thread-multi/CORE -Wl,-rpath,/vobs/cc/CCA-perl01/perl5_Linux_x64__=
________sixtyfive_char_path/prod/lib/5.18.0/x86_64-linux-thread-multi/CORE =
-Wl,-L/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/plib=
/lib -Wl,-rpath,/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char=
_path/plib/lib -Wl,-L/vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive=
_char_path/plib/apache/lib -Wl,-rpath,/vobs/cc/CCA-perl01/perl5_Linux_x64__=
________sixtyfive_char_path/plib/apache/lib -Wl,--enable-new-dtags -fstack-=
protector'
>
> Locally applied patches:
>
>
> ---
> @INC for perl 5.18.0:
>     /vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/prod=
/lib/site_perl/5.18.0/x86_64-linux-thread-multi
>     /vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/prod=
/lib/site_perl/5.18.0
>     /vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/prod=
/lib/5.18.0/x86_64-linux-thread-multi
>     /vobs/cc/CCA-perl01/perl5_Linux_x64__________sixtyfive_char_path/prod=
/lib/5.18.0
>     .
>
> ---
> Environment for perl 5.18.0:
>     HOME=3D/home/eedmja
>     LANG=3Den_US.UTF-8
>     LANGUAGE (unset)
>     LD_LIBRARY_PATH (unset)
>     LOGDIR (unset)
>     PATH=3D/tmp/_cc_CCA-perl01/perl5_Linux_x64__________sixtyfive_char_pa=
th/prod/bin:/tmp/_cc_CCA-perl01/perl5_Linux_x64__________sixtyfive_char_pat=
h/plib/bin:/bin:/usr/bin:/sbin:/usr/sbin:/opt/gnome/bin:/opt/kde3/bin:/usr/=
bin/X11:/home/eedmja/bin:/opt/rational/clearcase/bin
>     PERL_BADLANG (unset)
>     SHELL=3D/bin/tcsh