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scripts: add leaking_addresses.pl
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Currently we are leaking addresses from the kernel to user space. This
script is an attempt to find some of those leakages. Script parses
`dmesg` output and /proc and /sys files for hex strings that look like
kernel addresses.

Only works for 64 bit kernels, the reason being that kernel addresses on
64 bit kernels have 'ffff' as the leading bit pattern making greping
possible. On 32 kernels we don't have this luxury.

Scripts is _slightly_ smarter than a straight grep, we check for false
positives (all 0's or all 1's, and vsyscall start/finish addresses).

[ I think there is a lot of room for improvement here, but it's already
  useful, so I'm merging it as-is. The whole "hash %p format" series is
  expected to go into 4.15, but will not fix %x users, and will not
  incentivize people to look at what they are leaking.     - Linus ]

Signed-off-by: Tobin C. Harding <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@tcharding @torvalds
tcharding authored and torvalds committed Nov 6, 2017
1 parent af903dc commit 136fc5c
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5 changes: 5 additions & 0 deletions MAINTAINERS
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Original file line number Diff line number Diff line change
Expand Up @@ -7745,6 +7745,11 @@ S: Maintained
F: Documentation/scsi/53c700.txt
F: drivers/scsi/53c700*

LEAKING_ADDRESSES
M: Tobin C. Harding <[email protected]>
S: Maintained
F: scripts/leaking_addresses.pl

LED SUBSYSTEM
M: Richard Purdie <[email protected]>
M: Jacek Anaszewski <[email protected]>
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305 changes: 305 additions & 0 deletions scripts/leaking_addresses.pl
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#!/usr/bin/env perl
#
# (c) 2017 Tobin C. Harding <[email protected]>
# 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> ) {
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 = @_;
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);
}
}
}
}

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