Viewing file:  leaking_addresses.pl (12.8 KB) -rwxr-xr-x
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#!/usr/bin/env perl
# SPDX-License-Identifier: GPL-2.0-only
#
# (c) 2017 Tobin C. Harding <[email protected]>
#
# leaking_addresses.pl: Scan the 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.
#
# When the system is idle it is likely that most files under /proc/PID will be
# identical for various processes. Scanning _all_ the PIDs under /proc is
# unnecessary and implies that we are thoroughly scanning /proc. This is _not_
# the case because there may be ways userspace can trigger creation of /proc
# files that leak addresses but were not present during a scan. For these two
# reasons we exclude all PID directories under /proc except '1/'
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);
use Config;
use bigint qw/hex/;
use feature 'state';
my $P = $0;
# Directories to scan.
my @DIRS = ('/proc', '/sys');
# Timer for parsing each file, in seconds.
my $TIMEOUT = 10;
# Kernel addresses vary by architecture. We can only auto-detect the following
# architectures (using `uname -m`). (flag --32-bit overrides auto-detection.)
my @SUPPORTED_ARCHITECTURES = ('x86_64', 'ppc64', 'x86');
# Command line options.
my $help = 0;
my $debug = 0;
my $raw = 0;
my $output_raw = ""; # Write raw results to file.
my $input_raw = ""; # Read raw results from file instead of scanning.
my $suppress_dmesg = 0; # Don't show dmesg in output.
my $squash_by_path = 0; # Summary report grouped by absolute path.
my $squash_by_filename = 0; # Summary report grouped by filename.
my $kernel_config_file = ""; # Kernel configuration file.
my $opt_32bit = 0; # Scan 32-bit kernel.
my $page_offset_32bit = 0; # Page offset for 32-bit kernel.
# Skip these absolute paths.
my @skip_abs = (
'/proc/kmsg',
'/proc/device-tree',
'/proc/1/syscall',
'/sys/firmware/devicetree',
'/sys/kernel/debug/tracing/trace_pipe',
'/sys/kernel/security/apparmor/revision');
# Skip these under any subdirectory.
my @skip_any = (
'pagemap',
'events',
'access',
'registers',
'snapshot_raw',
'trace_pipe_raw',
'ptmx',
'trace_pipe',
'fd',
'usbmon');
sub help
{
my ($exitcode) = @_;
print << "EOM";
Usage: $P [OPTIONS]
Options:
-o, --output-raw=<file> Save results for future processing.
-i, --input-raw=<file> Read results from file instead of scanning.
--raw Show raw results (default).
--suppress-dmesg Do not show dmesg results.
--squash-by-path Show one result per unique path.
--squash-by-filename Show one result per unique filename.
--kernel-config-file=<file> Kernel configuration file (e.g /boot/config)
--32-bit Scan 32-bit kernel.
--page-offset-32-bit=o Page offset (for 32-bit kernel 0xABCD1234).
-d, --debug Display debugging output.
-h, --help Display this help and exit.
Scans the running kernel for potential leaking addresses.
EOM
exit($exitcode);
}
GetOptions(
'd|debug' => \$debug,
'h|help' => \$help,
'o|output-raw=s' => \$output_raw,
'i|input-raw=s' => \$input_raw,
'suppress-dmesg' => \$suppress_dmesg,
'squash-by-path' => \$squash_by_path,
'squash-by-filename' => \$squash_by_filename,
'raw' => \$raw,
'kernel-config-file=s' => \$kernel_config_file,
'32-bit' => \$opt_32bit,
'page-offset-32-bit=o' => \$page_offset_32bit,
) or help(1);
help(0) if ($help);
if ($input_raw) {
format_output($input_raw);
exit(0);
}
if (!$input_raw and ($squash_by_path or $squash_by_filename)) {
printf "\nSummary reporting only available with --input-raw=<file>\n";
printf "(First run scan with --output-raw=<file>.)\n";
exit(128);
}
if (!(is_supported_architecture() or $opt_32bit or $page_offset_32bit)) {
printf "\nScript does not support your architecture, sorry.\n";
printf "\nCurrently we support: \n\n";
foreach(@SUPPORTED_ARCHITECTURES) {
printf "\t%s\n", $_;
}
printf("\n");
printf("If you are running a 32-bit architecture you may use:\n");
printf("\n\t--32-bit or --page-offset-32-bit=<page offset>\n\n");
my $archname = `uname -m`;
printf("Machine hardware name (`uname -m`): %s\n", $archname);
exit(129);
}
if ($output_raw) {
open my $fh, '>', $output_raw or die "$0: $output_raw: $!\n";
select $fh;
}
parse_dmesg();
walk(@DIRS);
exit 0;
sub dprint
{
printf(STDERR @_) if $debug;
}
sub is_supported_architecture
{
return (is_x86_64() or is_ppc64() or is_ix86_32());
}
sub is_32bit
{
# Allow --32-bit or --page-offset-32-bit to override
if ($opt_32bit or $page_offset_32bit) {
return 1;
}
return is_ix86_32();
}
sub is_ix86_32
{
state $arch = `uname -m`;
chomp $arch;
if ($arch =~ m/i[3456]86/) {
return 1;
}
return 0;
}
sub is_arch
{
my ($desc) = @_;
my $arch = `uname -m`;
chomp $arch;
if ($arch eq $desc) {
return 1;
}
return 0;
}
sub is_x86_64
{
state $is = is_arch('x86_64');
return $is;
}
sub is_ppc64
{
state $is = is_arch('ppc64');
return $is;
}
# Gets config option value from kernel config file.
# Returns "" on error or if config option not found.
sub get_kernel_config_option
{
my ($option) = @_;
my $value = "";
my $tmp_file = "";
my @config_files;
# Allow --kernel-config-file to override.
if ($kernel_config_file ne "") {
@config_files = ($kernel_config_file);
} elsif (-R "/proc/config.gz") {
my $tmp_file = "/tmp/tmpkconf";
if (system("gunzip < /proc/config.gz > $tmp_file")) {
dprint("system(gunzip < /proc/config.gz) failed\n");
return "";
} else {
@config_files = ($tmp_file);
}
} else {
my $file = '/boot/config-' . `uname -r`;
chomp $file;
@config_files = ($file, '/boot/config');
}
foreach my $file (@config_files) {
dprint("parsing config file: $file\n");
$value = option_from_file($option, $file);
if ($value ne "") {
last;
}
}
if ($tmp_file ne "") {
system("rm -f $tmp_file");
}
return $value;
}
# Parses $file and returns kernel configuration option value.
sub option_from_file
{
my ($option, $file) = @_;
my $str = "";
my $val = "";
open(my $fh, "<", $file) or return "";
while (my $line = <$fh> ) {
if ($line =~ /^$option/) {
($str, $val) = split /=/, $line;
chomp $val;
last;
}
}
close $fh;
return $val;
}
sub is_false_positive
{
my ($match) = @_;
if (is_32bit()) {
return is_false_positive_32bit($match);
}
# 64 bit false positives.
if ($match =~ '\b(0x)?(f|F){16}\b' or
$match =~ '\b(0x)?0{16}\b') {
return 1;
}
if (is_x86_64() and is_in_vsyscall_memory_region($match)) {
return 1;
}
return 0;
}
sub is_false_positive_32bit
{
my ($match) = @_;
state $page_offset = get_page_offset();
if ($match =~ '\b(0x)?(f|F){8}\b') {
return 1;
}
if (hex($match) < $page_offset) {
return 1;
}
return 0;
}
# returns integer value
sub get_page_offset
{
my $page_offset;
my $default_offset = 0xc0000000;
# Allow --page-offset-32bit to override.
if ($page_offset_32bit != 0) {
return $page_offset_32bit;
}
$page_offset = get_kernel_config_option('CONFIG_PAGE_OFFSET');
if (!$page_offset) {
return $default_offset;
}
return $page_offset;
}
sub is_in_vsyscall_memory_region
{
my ($match) = @_;
my $hex = hex($match);
my $region_min = hex("0xffffffffff600000");
my $region_max = hex("0xffffffffff601000");
return ($hex >= $region_min and $hex <= $region_max);
}
# True if argument potentially contains a kernel address.
sub may_leak_address
{
my ($line) = @_;
my $address_re;
# Signal masks.
if ($line =~ '^SigBlk:' or
$line =~ '^SigIgn:' 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;
}
$address_re = get_address_re();
while ($line =~ /($address_re)/g) {
if (!is_false_positive($1)) {
return 1;
}
}
return 0;
}
sub get_address_re
{
if (is_ppc64()) {
return '\b(0x)?[89abcdef]00[[:xdigit:]]{13}\b';
} elsif (is_32bit()) {
return '\b(0x)?[[:xdigit:]]{8}\b';
}
return get_x86_64_re();
}
sub get_x86_64_re
{
# We handle page table levels but only if explicitly configured using
# CONFIG_PGTABLE_LEVELS. If config file parsing fails or config option
# is not found we default to using address regular expression suitable
# for 4 page table levels.
state $ptl = get_kernel_config_option('CONFIG_PGTABLE_LEVELS');
if ($ptl == 5) {
return '\b(0x)?ff[[:xdigit:]]{14}\b';
}
return '\b(0x)?ffff[[:xdigit:]]{12}\b';
}
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) = @_;
foreach (@skip_abs) {
return 1 if (/^$path$/);
}
my($filename, $dirs, $suffix) = fileparse($path);
foreach (@skip_any) {
return 1 if (/^$filename$/);
}
return 0;
}
sub timed_parse_file
{
my ($file) = @_;
eval {
local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required.
alarm $TIMEOUT;
parse_file($file);
alarm 0;
};
if ($@) {
die unless $@ eq "alarm\n"; # Propagate unexpected errors.
printf STDERR "timed out parsing: %s\n", $file;
}
}
sub parse_file
{
my ($file) = @_;
if (! -R $file) {
return;
}
if (! -T $file) {
return;
}
open my $fh, "<", $file or return;
while ( <$fh> ) {
chomp;
if (may_leak_address($_)) {
printf("$file: $_\n");
}
}
close $fh;
}
# Checks if the actual path name is leaking a kernel address.
sub check_path_for_leaks
{
my ($path) = @_;
if (may_leak_address($path)) {
printf("Path name may contain address: $path\n");
}
}
# Recursively walk directory tree.
sub walk
{
my @dirs = @_;
while (my $pwd = shift @dirs) {
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 $path);
# skip /proc/PID except /proc/1
next if (($path =~ /^\/proc\/[0-9]+$/) &&
($path !~ /^\/proc\/1$/));
next if (skip($path));
check_path_for_leaks($path);
if (-d $path) {
push @dirs, $path;
next;
}
dprint("parsing: $path\n");
timed_parse_file($path);
}
}
}
sub format_output
{
my ($file) = @_;
# Default is to show raw results.
if ($raw or (!$squash_by_path and !$squash_by_filename)) {
dump_raw_output($file);
return;
}
my ($total, $dmesg, $paths, $files) = parse_raw_file($file);
printf "\nTotal number of results from scan (incl dmesg): %d\n", $total;
if (!$suppress_dmesg) {
print_dmesg($dmesg);
}
if ($squash_by_filename) {
squash_by($files, 'filename');
}
if ($squash_by_path) {
squash_by($paths, 'path');
}
}
sub dump_raw_output
{
my ($file) = @_;
open (my $fh, '<', $file) or die "$0: $file: $!\n";
while (<$fh>) {
if ($suppress_dmesg) {
if ("dmesg:" eq substr($_, 0, 6)) {
next;
}
}
print $_;
}
close $fh;
}
sub parse_raw_file
{
my ($file) = @_;
my $total = 0; # Total number of lines parsed.
my @dmesg; # dmesg output.
my %files; # Unique filenames containing leaks.
my %paths; # Unique paths containing leaks.
open (my $fh, '<', $file) or die "$0: $file: $!\n";
while (my $line = <$fh>) {
$total++;
if ("dmesg:" eq substr($line, 0, 6)) {
push @dmesg, $line;
next;
}
cache_path(\%paths, $line);
cache_filename(\%files, $line);
}
return $total, \@dmesg, \%paths, \%files;
}
sub print_dmesg
{
my ($dmesg) = @_;
print "\ndmesg output:\n";
if (@$dmesg == 0) {
print "<no results>\n";
return;
}
foreach(@$dmesg) {
my $index = index($_, ': ');
$index += 2; # skid ': '
print substr($_, $index);
}
}
sub squash_by
{
my ($ref, $desc) = @_;
print "\nResults squashed by $desc (excl dmesg). ";
print "Displaying [<number of results> <$desc>], <example result>\n";
if (keys %$ref == 0) {
print "<no results>\n";
return;
}
foreach(keys %$ref) {
my $lines = $ref->{$_};
my $length = @$lines;
printf "[%d %s] %s", $length, $_, @$lines[0];
}
}
sub cache_path
{
my ($paths, $line) = @_;
my $index = index($line, ': ');
my $path = substr($line, 0, $index);
$index += 2; # skip ': '
add_to_cache($paths, $path, substr($line, $index));
}
sub cache_filename
{
my ($files, $line) = @_;
my $index = index($line, ': ');
my $path = substr($line, 0, $index);
my $filename = basename($path);
$index += 2; # skip ': '
add_to_cache($files, $filename, substr($line, $index));
}
sub add_to_cache
{
my ($cache, $key, $value) = @_;
if (!$cache->{$key}) {
$cache->{$key} = ();
}
push @{$cache->{$key}}, $value;
}
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