#!/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 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, --version           Display this help and exit.

Scans the running kernel for potential leaking addresses.

EOM
        exit($exitcode);
}

GetOptions(
        'd|debug'               => \$debug,
        'h|help'                => \$help,
        'version'               => \$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 "$0: system(gunzip < /proc/config.gz) failed\n";
                        return "";
                } else {
                        @config_files = ($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: %s\n", $file);
                $value = option_from_file($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> ) {
                if (may_leak_address($_)) {
                        print $file . ': ' . $_;
                }
        }
        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;
}