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@orangetw orangetw/DSSAFE.pm Secret
Created Aug 30, 2019

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code snippet of DSSAFE.pm
# ...
@EXPORT = qw(open popen ppopen close system psystem exec backtick pbacktick
maketemp untaint is_tainted);
# ...
sub __parsecmd {
my $cmd = shift;
my @args = quotewords('\s+', 1, $cmd);
my @env = (); # currently not used. pending review.
my @xargs = (); # arguments of the command
my ($xcmd, $fout, $fin, $ferr, $mout, $min, $merr, $rd2);
while (@args) {
my $arg = shift @args;
next if (length($arg) == 0);
unless (defined $xcmd) {
if ($arg =~ /^(\w+)=(.+)$/) {
push @env, {$1 => $2};
next;
} elsif ($arg =~ /^[^\/a-zA-Z]/) {
__log("Invalid command: $cmd"); # must be / or letter
return undef;
}
$xcmd = untaint($arg);
next;
}
if ($arg =~ /^(2|1)>&(2|1)$/) {
$rd2 = $2;
} elsif ($arg =~ /^(1|2)?(>>?)([^>].*)?$/) {
if ($1 and $1 == 2) {
($merr, $ferr) = ($2, $3 || untaint(shift @args));
} else {
($mout, $fout) = ($2, $3 || untaint(shift @args));
}
} elsif ($arg =~ /^(<)(.+)?$/) {
($min, $fin) = ($1, $2 || untaint(shift @args));
} elsif ($arg =~ /^(>&)(.+)?$/) {
$fout = $ferr = $2 || untaint(shift @args);
$mout = $merr = ">";
} elsif ($arg =~ /^(\'|\")(.*)(\'|\")$/) {
push @xargs, $2; # skip checking meta between quotes
# } elsif ($arg =~ /[\$\&\*\(\)\{\}\[\]\`\;\|\?\n~<>]/) {
} elsif ($arg =~ /[\&\*\(\)\{\}\[\]\`\;\|\?\n~<>]/) {
__log("Meta characters not allowed: ($arg) $cmd");
return undef;
} elsif ($arg =~ /\W\$/) {
__log("Meta characters not allowed: ($arg) $cmd");
} else {
push @xargs, untaint($arg);
}
}
if ($rd2) {
# redirect both 2 and 1 to the same place
if (defined $fout) {
($ferr, $merr) = ($fout, $mout);
} elsif (defined $ferr) {
($fout, $mout) = ($ferr, $merr);
} elsif ($rd2 == 1) {
open STDERR, ">&STDOUT" or die "cannot dup STDERR to STDOUT:$!\n";
select STDERR; $|=1;
select STDOUT; $|=1;
} elsif ($rd2 == 2) {
open STDOUT, ">&STDERR" or die "cannot dup STDOUT to STDERR:$!\n";
select STDOUT; $|=1;
select STDERR; $|=1;
}
}
unless ($xcmd) {
__log("Command parsing error: $cmd");
return undef;
}
# need to untaint $cmd. otherwise the whole hash will be tainted.
# but $cmd will never be used for exec anyway, only for debug.
my $params = { cmd => untaint($cmd), xcmd => $xcmd, xargs => \@xargs };
$params->{fstdout} = $fout if $fout;
$params->{mstdout} = $mout if $mout;
$params->{fstderr} = $ferr if $ferr;
$params->{mstderr} = $merr if $merr;
$params->{fstdin} = $fin if $fin;
$params->{mstdin} = $min if $min;
return $params;
}
# ...
sub system {
return CORE::system(@_) if (@_ > 1);
my $params = __parsecmd(join(' ', @_));
return -1 unless ($params);
# We want SIGINT and SIGQUIT to be ignored in the parent
# while the child is running. However, we want the child
# to get these signals -- so we declare a block around
# the code that ignores SIGINT such that the child will
# exec with the signals turned on.
{
local $SIG{INT} = 'IGNORE';
local $SIG{QUIT} = 'IGNORE';
flush STDOUT; flush STDERR; flush STDIN;
my $pid = fork;
unless (defined $pid) {
__log("system: cannot fork $!");
return -1;
}
if ($pid) {
waitpid $pid, 0;
return $?;
}
}
return __execo $params;
}
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