leaking_addresses.pl

#!/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).
#
# You can configure the behaviour of the script;
#
#  - By adding paths, for directories you do not want to walk;
#     absolute paths: @skip_walk_dirs_abs
#     directory names: @skip_walk_dirs_any
#
#  - By adding paths, for files you do not want to parse;
#     absolute paths: @skip_parse_files_abs
#     file names: @skip_parse_files_any
#
# The use of @skip_xxx_xxx_any causes files to be skipped where ever they occur.
# For example adding 'fd' to @skip_walk_dirs_any causes the fd/ directory to be
# skipped for all PID sub-directories of /proc
#
# The same thing can be achieved by passing command line options to --dont-walk
# and --dont-parse. If absolute paths are supplied to these options they are
# appended to the @skip_xxx_xxx_abs arrays. If file names are supplied to these
# options, they are appended to the @skip_xxx_xxx_any arrays.
#
# 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;
my @dont_walk = ();
my @dont_parse = ();

# 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:

	--dont-walk=<dir>      Don't walk tree starting at <dir>.
	--dont-parse=<file>    Don't parse <file>.
	-d, --debug                Display debugging output.
	-h, --help, --version      Display this help and exit.

If an absolute path is passed to --dont_XXX then this path is skipped. If a
single filename is passed then this file/directory will be skipped when
appearing under any subdirectory.

Example:

	# Just scan dmesg output.
	scripts/leaking_addresses.pl --dont_walk_abs /proc --dont_walk_abs /sys

Scans the running (64 bit) kernel for potential leaking addresses.

EOM
	exit($exitcode);
}

GetOptions(
	'dont-walk=s'		=> \@dont_walk,
	'dont-parse=s'		=> \@dont_parse,
	'd|debug'		=> \$debug,
	'h|help'		=> \$help,
	'version'		=> \$help
) or help(1);

help(0) if ($help);

push_to_global();

parse_dmesg();
walk(@DIRS);

exit 0;

sub debug_arrays
{
	print 'dirs_any: ' . join(", ", @skip_walk_dirs_any) . "\n";
	print 'dirs_abs: ' . join(", ", @skip_walk_dirs_abs) . "\n";
	print 'parse_any: ' . join(", ", @skip_parse_files_any) . "\n";
	print 'parse_abs: ' . join(", ", @skip_parse_files_abs) . "\n";
}

sub dprint
{
	printf(STDERR @_) if $debug;
}

sub push_in_abs_any
{
	my ($in, $abs, $any) = @_;

	foreach my $path (@$in) {
		if (File::Spec->file_name_is_absolute($path)) {
			push @$abs, $path;
		} elsif (index($path,'/') == -1) {
			push @$any, $path;
		} else {
			print 'path error: ' . $path;
		}
	}
}

# Push command line options to global arrays.
sub push_to_global
{
	push_in_abs_any(\@dont_walk, \@skip_walk_dirs_abs, \@skip_walk_dirs_any);
	push_in_abs_any(\@dont_parse, \@skip_parse_files_abs, \@skip_parse_files_any);
}

sub is_false_positive
{
        my ($match) = @_;

        if ($match =~ '\b(0x)?(f|F){16}\b' or
            $match =~ '\b(0x)?0{16}\b') {
                return 1;
        }

        # vsyscall memory region, we should probably check against a range here.
        if ($match =~ '\bf{10}600000\b' or
            $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> ) {
		chomp;
		if (may_leak_address($_)) {
			printf("$file: $_\n");
		}
	}
	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 = @_;
	my %seen;

	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);
			}
		}
	}
}