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#!/usr/bin/env perl
#
# (c) 2017 Tobin C. Harding <me@tobin.cc>
# Licensed under the terms of the GNU GPL License version 2
#
# leaking_addresses.pl: Scan 64 bit kernel for potential leaking addresses.
# - Scans dmesg output.
# - Walks directory tree and parses each file (for each directory in @DIRS).
#
# Use --debug to output path before parsing, this is useful to find files that
# cause the script to choke.
#
# You may like to set kptr_restrict=2 before running script
# (see Documentation/sysctl/kernel.txt).
use warnings;
use strict;
use POSIX;
use File::Basename;
use File::Spec;
use Cwd 'abs_path';
use Term::ANSIColor qw(:constants);
use Getopt::Long qw(:config no_auto_abbrev);
my $P = $0;
my $V = '0.01';
# Directories to scan.
my @DIRS = ('/proc', '/sys');
# Command line options.
my $help = 0;
my $debug = 0;
# Do not parse these files (absolute path).
my @skip_parse_files_abs = ('/proc/kmsg',
'/proc/kcore',
'/proc/fs/ext4/sdb1/mb_groups',
'/proc/1/fd/3',
'/sys/kernel/debug/tracing/trace_pipe',
'/sys/kernel/security/apparmor/revision');
# Do not parse thes files under any subdirectory.
my @skip_parse_files_any = ('0',
'1',
'2',
'pagemap',
'events',
'access',
'registers',
'snapshot_raw',
'trace_pipe_raw',
'ptmx',
'trace_pipe');
# Do not walk these directories (absolute path).
my @skip_walk_dirs_abs = ();
# Do not walk these directories under any subdirectory.
my @skip_walk_dirs_any = ('self',
'thread-self',
'cwd',
'fd',
'stderr',
'stdin',
'stdout');
sub help
{
my ($exitcode) = @_;
print << "EOM";
Usage: $P [OPTIONS]
Version: $V
Options:
-d, --debug Display debugging output.
-h, --help, --version Display this help and exit.
Scans the running (64 bit) kernel for potential leaking addresses.
EOM
exit($exitcode);
}
GetOptions(
'd|debug' => \$debug,
'h|help' => \$help,
'version' => \$help
) or help(1);
help(0) if ($help);
parse_dmesg();
walk(@DIRS);
exit 0;
sub dprint
{
printf(STDERR @_) if $debug;
}
sub is_false_positive
{
my ($match) = @_;
if ($match =~ '\b(0x)?(f|F){16}\b' or
$match =~ '\b(0x)?0{16}\b') {
return 1;
}
if ($match =~ '\bf{10}600000\b' or# vsyscall memory region, we should probably check against a range here.
$match =~ '\bf{10}601000\b') {
return 1;
}
return 0;
}
# True if argument potentially contains a kernel address.
sub may_leak_address
{
my ($line) = @_;
my $address = '\b(0x)?ffff[[:xdigit:]]{12}\b';
# Signal masks.
if ($line =~ '^SigBlk:' or
$line =~ '^SigCgt:') {
return 0;
}
if ($line =~ '\bKEY=[[:xdigit:]]{14} [[:xdigit:]]{16} [[:xdigit:]]{16}\b' or
$line =~ '\b[[:xdigit:]]{14} [[:xdigit:]]{16} [[:xdigit:]]{16}\b') {
return 0;
}
while (/($address)/g) {
if (!is_false_positive($1)) {
return 1;
}
}
return 0;
}
sub parse_dmesg
{
open my $cmd, '-|', 'dmesg';
while (<$cmd>) {
if (may_leak_address($_)) {
print 'dmesg: ' . $_;
}
}
close $cmd;
}
# True if we should skip this path.
sub skip
{
my ($path, $paths_abs, $paths_any) = @_;
foreach (@$paths_abs) {
return 1 if (/^$path$/);
}
my($filename, $dirs, $suffix) = fileparse($path);
foreach (@$paths_any) {
return 1 if (/^$filename$/);
}
return 0;
}
sub skip_parse
{
my ($path) = @_;
return skip($path, \@skip_parse_files_abs, \@skip_parse_files_any);
}
sub parse_file
{
my ($file) = @_;
if (! -R $file) {
return;
}
if (skip_parse($file)) {
dprint "skipping file: $file\n";
return;
}
dprint "parsing: $file\n";
open my $fh, "<", $file or return;
while ( <$fh> ) {
if (may_leak_address($_)) {
print $file . ': ' . $_;
}
}
close $fh;
}
# True if we should skip walking this directory.
sub skip_walk
{
my ($path) = @_;
return skip($path, \@skip_walk_dirs_abs, \@skip_walk_dirs_any)
}
# Recursively walk directory tree.
sub walk
{
my @dirs = @_;
while (my $pwd = shift @dirs) {
next if (skip_walk($pwd));
next if (!opendir(DIR, $pwd));
my @files = readdir(DIR);
closedir(DIR);
foreach my $file (@files) {
next if ($file eq '.' or $file eq '..');
my $path = "$pwd/$file";
next if (-l $path);
if (-d $path) {
push @dirs, $path;
} else {
parse_file($path);
}
}
}
}
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