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Message-Id: <1508998863-14629-1-git-send-email-me@tobin.cc>
Date: Thu, 26 Oct 2017 17:21:03 +1100
From: "Tobin C. Harding" <me@...in.cc>
To: kernel-hardening@...ts.openwall.com
Cc: "Tobin C. Harding" <me@...in.cc>,
"Jason A. Donenfeld" <Jason@...c4.com>,
Theodore Ts'o <tytso@....edu>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Kees Cook <keescook@...omium.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Tycho Andersen <tycho@...ker.com>,
"Roberts, William C" <william.c.roberts@...el.com>,
Tejun Heo <tj@...nel.org>,
Jordan Glover <Golden_Miller83@...tonmail.ch>,
Greg KH <gregkh@...uxfoundation.org>,
Petr Mladek <pmladek@...e.com>,
Joe Perches <joe@...ches.com>,
Ian Campbell <ijc@...lion.org.uk>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <wilal.deacon@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Chris Fries <cfries@...gle.com>,
Dave Weinstein <olorin@...gle.com>,
Daniel Micay <danielmicay@...il.com>,
Djalal Harouni <tixxdz@...il.com>,
linux-kernel@...r.kernel.org
Subject: [PATCH] scripts: add leaking_addresses.pl
Currently we are leaking addresses from the kernel to user space. This
script is an attempt to find 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.
Signed-off-by: Tobin C. Harding <me@...in.cc>
---
Changes since RFC V2
- Refactor the code that skips directories and files into helper functions.
- Add documentation.
- Add an entry in MAINTAINERS.
MAINTAINERS | 5 +
scripts/leaking_addresses.pl | 282 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 287 insertions(+)
create mode 100755 scripts/leaking_addresses.pl
diff --git a/MAINTAINERS b/MAINTAINERS
index e652a3e2929d..c1ad6d133a57 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7745,6 +7745,11 @@ S: Maintained
F: Documentation/scsi/53c700.txt
F: drivers/scsi/53c700*
+LEAKING_ADDRESSES
+M: Tobin C. Harding <me@...in.cc>
+S: Maintained
+F: scripts/leaking_addresses.pl
+
LED SUBSYSTEM
M: Richard Purdie <rpurdie@...ys.net>
M: Jacek Anaszewski <jacek.anaszewski@...il.com>
diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
new file mode 100755
index 000000000000..430ff1b0c3ec
--- /dev/null
+++ b/scripts/leaking_addresses.pl
@@ -0,0 +1,282 @@
+#!/usr/bin/env perl
+#
+# (c) 2017 Tobin C. Harding <me@...in.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 $debug = 0;
+my @dont_walk = ();
+my @dont_parse = ();
+
+# Do not parse these files (ablosute path).
+my @skip_parse_files_abs = ('/proc/kmsg',
+ '/proc/kcore',
+ '/proc/fs/ext4/sdb1/mb_groups',
+ '/proc/1/fd/3',
+ '/sys/kernel/debug/tracing/trace_pipe',
+ '/sys/kernel/security/apparmor/revision');
+
+# Do not parse thes files under any subdirectory.
+my @skip_parse_files_any = ('0',
+ '1',
+ '2',
+ 'pagemap',
+ 'events',
+ 'access',
+ 'registers',
+ 'snapshot_raw',
+ 'trace_pipe_raw',
+ 'ptmx',
+ 'trace_pipe');
+
+# Do not walk these directories (absolute path).
+my @skip_walk_dirs_abs = ();
+
+# Do not walk these directories under any subdirectory.
+my @skip_walk_dirs_any = ('self',
+ 'thread-self',
+ 'cwd',
+ 'fd',
+ 'stderr',
+ 'stdin',
+ 'stdout');
+
+sub help
+{
+ my ($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: ' . $path;
+ }
+ }
+}
+
+# Push command line options to global arrays.
+sub push_to_global
+{
+ push_in_abs_any(\@dont_walk, \@skip_walk_dirs_abs, \@skip_walk_dirs_any);
+ push_in_abs_any(\@dont_parse, \@skip_parse_files_abs, \@skip_parse_files_any);
+}
+
+# True if argument potentially contains a kernel address.
+sub may_leak_address
+{
+ my ($line) = @_;
+
+ # Ignore false positives.
+ if ($line =~ '\b(0x)?(f|F){16}\b' or
+ $line =~ '\b(0x)?0{16}\b' or
+ $line =~ '\bKEY=[[:xdigit:]]{14} [[:xdigit:]]{16} [[:xdigit:]]{16}\b') {
+ return 0;
+ }
+
+ # Potential kernel address.
+ if ($line =~ '\b(0x)?ffff[[:xdigit:]]{12}\b') {
+ 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);
+ }
+ }
+ }
+}
+
--
2.7.4
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