Re: [PATCH] leaking_addresses: add support for 32-bit kernel addresses

Tobin C. Harding
2017-11-28T21:10:09Z

On Tue, Nov 28, 2017 at 03:16:24PM +0200, Alexander Kapshuk wrote:
> On Tue, Nov 28, 2017 at 8:32 AM, Tobin C. Harding <me@tobin.cc> wrote:
> > Currently, leaking_addresses.pl only supports scanning 64 bit
> > architectures. This is due to how the regular expressions are formed. We
> > can do better than this. 32 architectures can be supported if we take
> > into consideration the kernel virtual address split.
> >
> > Add support for ix86 32 bit architectures.
> > - Add command line option for page offset.
> > - Add command line option for kernel configuration file.
> > - Parse kernel config file for page offset (CONFIG_PAGE_OFFSET).
> > - Use page offset when checking for kernel virtual addresses.
> >
> > Signed-off-by: Kaiwan N Billimoria <kaiwan.billimoria@gmail.com>
> > Signed-off-by: Tobin C. Harding <me@tobin.cc>
> > ---
> >
> > As discussed this is a patch based on Kaiwan's previous patch. This
> > patch represents co development by Kaiwan and Tobin.
> >
> > Applies on top of commit 4fbd8d194f06 (Linux 4.15-rc1)
> >
> > thanks,
> > Tobin.
> >
> > scripts/leaking_addresses.pl | 168 +++++++++++++++++++++++++++++++++++++------
> > 1 file changed, 148 insertions(+), 20 deletions(-)
> >
> > diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
> > index bc5788000018..f03f2f140e0a 100755
> > --- a/scripts/leaking_addresses.pl
> > +++ b/scripts/leaking_addresses.pl
> > @@ -1,9 +1,11 @@
> > #!/usr/bin/env perl
> > #
> > # (c) 2017 Tobin C. Harding <me@tobin.cc>
> > +# (c) 2017 Kaiwan N Billimoria <kaiwan.billimoria@gmail.com> (ix86 stuff)
> > +#
> > # Licensed under the terms of the GNU GPL License version 2
> > #
> > -# leaking_addresses.pl: Scan 64 bit kernel for potential leaking addresses.
> > +# 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).
> > #
> > @@ -22,6 +24,7 @@ use Cwd 'abs_path';
> > use Term::ANSIColor qw(:constants);
> > use Getopt::Long qw(:config no_auto_abbrev);
> > use Config;
> > +use feature 'state';
> >
> > my $P = $0;
> > my $V = '0.01';
> > @@ -35,18 +38,19 @@ my $TIMEOUT = 10;
> > # Script can only grep for kernel addresses on the following architectures. If
> > # your architecture is not listed here and has a grep'able kernel address please
> > # consider submitting a patch.
> > -my @SUPPORTED_ARCHITECTURES = ('x86_64', 'ppc64');
> > +my @SUPPORTED_ARCHITECTURES = ('x86_64', 'ppc64', 'i[3456]86');
> >
> > # 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 $raw = 0; # Show raw output.
> > +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 $page_offset_32bit = 0; # 32-bit: value of CONFIG_PAGE_OFFSET
> > +my $kernel_config_file = ""; # Kernel configuration file.
> >
> > # Do not parse these files (absolute path).
> > my @skip_parse_files_abs = ('/proc/kmsg',
> > @@ -95,14 +99,16 @@ Version: $V
> >
> > 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.
> > - -d, --debug Display debugging output.
> > - -h, --help, --version Display this help and exit.
> > + -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.
> > + --page-offset-32bit=<hex> PAGE_OFFSET value (for 32-bit kernels).
> > + --kernel-config-file=<file> Kernel configuration file (e.g /boot/config)
> > + -d, --debug Display debugging output.
> > + -h, --help, --version Display this help and exit.
> >
> > Examples:
> >
> > @@ -115,7 +121,10 @@ Examples:
> > # View summary report.
> > $0 --input-raw scan.out --squash-by-filename
> >
> > -Scans the running (64 bit) kernel for potential leaking addresses.
> > + # Scan kernel on a 32-bit system with a 2GB:2GB virtual address split.
> > + $0 --page-offset-32bit=0x80000000
> > +
> > +Scans the running kernel for potential leaking addresses.
> >
> > EOM
> > exit($exitcode);
> > @@ -131,6 +140,8 @@ GetOptions(
> > 'squash-by-path' => \$squash_by_path,
> > 'squash-by-filename' => \$squash_by_filename,
> > 'raw' => \$raw,
> > + 'page-offset-32bit=o' => \$page_offset_32bit,
> > + 'kernel-config-file=s' => \$kernel_config_file,
> > ) or help(1);
> >
> > help(0) if ($help);
> > @@ -146,7 +157,9 @@ if (!$input_raw and ($squash_by_path or $squash_by_filename)) {
> > exit(128);
> > }
> >
> > -if (!is_supported_architecture()) {
> > +if (is_supported_architecture()) {
> > + show_detected_architecture() if $debug;
> > +} else {
> > printf "\nScript does not support your architecture, sorry.\n";
> > printf "\nCurrently we support: \n\n";
> > foreach(@SUPPORTED_ARCHITECTURES) {
> > @@ -177,7 +190,7 @@ sub dprint
> >
> > sub is_supported_architecture
> > {
> > - return (is_x86_64() or is_ppc64());
> > + return (is_x86_64() or is_ppc64() or is_ix86_32());
> > }
> >
> > sub is_x86_64
> > @@ -200,10 +213,40 @@ sub is_ppc64
> > return 0;
> > }
> >
> > +sub is_ix86_32
> > +{
> > + my $archname = $Config{archname};
> > +
> > + if ($archname =~ m/i[3456]86-linux/) {
> > + return 1;
> > + }
> > + return 0;
> > +}
> > +
> > +sub show_detected_architecture
> > +{
> > + printf "Detected architecture: ";
> > + if (is_ix86_32()) {
> > + printf "32 bit x86\n";
> > + } elsif (is_x86_64()) {
> > + printf "x86_64\n";
> > + } elsif (is_ppc64()) {
> > + printf "ppc64\n";
> > + } else {
> > + printf "failed to detect architecture\n"
> > + }
> > +}
> > +
> > sub is_false_positive
> > {
> > my ($match) = @_;
> >
> > + if (is_ix86_32()) {
> > + return is_false_positive_ix86_32($match);
> > + }
> > +
> > + # 64 bit architectures
> > +
> > if ($match =~ '\b(0x)?(f|F){16}\b' or
> > $match =~ '\b(0x)?0{16}\b') {
> > return 1;
> > @@ -220,6 +263,87 @@ sub is_false_positive
> > return 0;
> > }
> >
> > +sub is_false_positive_ix86_32
> > +{
> > + my ($match) = @_;
> > + state $page_offset = get_page_offset(); # only gets called once
> > +
> > + if ($match =~ '\b(0x)?(f|F){8}\b') {
> > + return 1;
> > + }
> > +
> > + my $addr32 = eval hex($match);
> > + if ($addr32 < $page_offset) {
> > + return 1;
> > + }
> > +
> > + return 0;
> > +}
> > +
>
>
>
> > +sub get_page_offset
> > +{
> > + my $page_offset;
> > + my $default_offset = "0xc0000000";
> > + my @config_files;
> > +
> > + # Allow --page-offset-32bit to over ride.
> > + if ($page_offset_32bit != 0) {
> > + return $page_offset_32bit;
> > + }
> > +
> > + # Allow --kernel-config-file to over ride.
> > + if ($kernel_config_file != "") {
> > + @config_files = ($kernel_config_file);
> > + } else {
> > + my $config_file = '/boot/config-' . `uname -r`;
> > + @config_files = ($config_file, '/boot/config');
> > + }
> > +
> > + if (-R "/proc/config.gz") {
> > + my $tmp_file = "/tmp/tmpkconf";
> > + if (system("gunzip < /proc/config.gz > $tmp_file")) {
> > + dprint " parse_kernel_config: system(gunzip...) failed\n";
> > + } else {
> > + $page_offset = parse_kernel_config_file($tmp_file);
> > + if ($page_offset ne "") {
> > + return $page_offset;
> > + }
> > + }
> > + system("rm -f $tmp_file");
> > + }
> > +
> > + foreach my $config_file (@config_files) {
> > + $page_offset = parse_kernel_config($config_file);
> > + if ($page_offset ne "") {
> > + return $page_offset;
> > + }
> > + }
> > +
> > + printf STDERR "Failed to parse kernel config files\n";
> > + printf STDERR "Falling back to %s\n", $default_offset;
> > + return $default_offset;
> > +}
> > +
> > +sub parse_kernel_config_file
> > +{
> > + my ($file) = @_;
> > + my $config = 'CONFIG_PAGE_OFFSET';
> > + my $val = "";
> > +
> > + open(my $fh, "<", $file) or return "";
> > + while (my $line = <$fh> ) {
> > + if ($line =~ /^$config/) {
> > + my ($str, $val) = split /=/, $line;
> > + chomp($val);
> > + last;
> > + }
> > + }
> > +
> > + close $fh;
> > + return $val;
> > +}
> > +
> > +
>
> Get_page_offset attempts to build a list of config files, which are
> then passed into the parsing function for further processing.
> This splits up the code to do with the config files between
> get_page_offset() and parse_kernel_config_file().
> May I suggest putting the kernel config file processing code into the
> parse_kernel_config_file() instead, and let the parsing function
> handle the config files and either return the page_offset or an empty
> string.
>
> See below for the proposed implementation.

Nice, this is much better! Thanks.

> Apologies for the absence of indentation.

Re-posting with indentation, comments in line.

> Disclaimer: I did not test-run the code being proposed.

I also did not test my comments ;)

> sub get_page_offset
> {
> my $default_offset = "0xc0000000";
> my $page_offset;
>
> # Allow --page-offset-32bit to over ride.
> if ($page_offset_32bit != 0) {
> return $page_offset_32bit;
> }
>
> $page_offset = parse_kernel_config_file();
> if ($page_offset ne "") {
> return $page_offset
> }
>
> printf STDERR "Failed to parse kernel config files\n";
> printf STDERR "Falling back to %s\n", $default_offset;
>
> return $default_offset;
> }
>
> sub parse_kernel_config_file
> {
> my @config_files;
> my $config = 'CONFIG_PAGE_OFFSET';
>
> # Allow --kernel-config-file to over ride.
> if ($kernel_config_file != "") {
> @config_files = ($kernel_config_file);
> } else {
> my $config_file = '/boot/config-' . `uname -r`;
> @config_files = ($config_file, '/boot/config');
> }
>
> if (-R "/proc/config.gz") {

perhaps
my $tmpkconf = '/tmp/tmpkconf';

> if (system("gunzip < /proc/config.gz > /tmp/tmpkconf") == 0) {
> push @config_files, "/tmp/tmpkconf";
> }
> }

Won't there only ever be a single config file? So if /proc/config.gz is
readable we could do

@config_files = ($tmpkconf)

> foreach my $config_file (@config_files) {
> open(my $fh, "<", $config_file) or return "";

open(my $fh, "<", $config_file) or next;

> while (my $line = <$fh> ) {
> if ($line =~ /^$config/) {
> my ($config_name, $page_offset) = split /=/, $line;
> chomp($page_offset);
> last;
> }
> }
> }
> system("rm -f $tmp_file");
> close $fh;
>
> return $page_offset;
> }

thanks,
Tobin.