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Message-ID: <20171206230316.GJ11835@eros>
Date: Thu, 7 Dec 2017 10:03:16 +1100
From: "Tobin C. Harding" <me@...in.cc>
To: kaiwan.billimoria@...il.com
Cc: Alexander Kapshuk <alexander.kapshuk@...il.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v3] scripts: leaking_addresses: add support for 32-bit
kernel addresses
On Wed, Dec 06, 2017 at 06:23:51PM +0530, kaiwan.billimoria@...il.com wrote:
> On Wed, 2017-12-06 at 17:21 +0530, kaiwan.billimoria@...il.com wrote:
> > On Wed, 2017-12-06 at 15:04 +1100, Tobin C. Harding wrote:
> > > On Tue, Dec 05, 2017 at 11:56:44AM +0530, kaiwan.billimoria@...il.com 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 (via the PAGE_OFFSET
> > > > kernel configurable).
> > > >
> > > > 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@...il.com>
> > > > ---
> > >
> > > Right, this is starting to look awesome.
> >
> > Great!
> >
> > > > Note- This patch represents co development by Tobin and Kaiwan (plus suggestions from
> > > > Alexander Kapshuk). Applies on Tobin's tree 'leaks' branch on top of commit 680db1ef560f
> > > > (leaking_addresses: fix typo function not called).
> > > >
> > > >
> > > > scripts/leaking_addresses.pl | 169 +++++++++++++++++++++++++++++++++++++------
> > > > 1 file changed, 148 insertions(+), 21 deletions(-)
> > > >
> > > > diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
> > > > index 2d5336b3e1ea..6b015980d117 100755
> > > > --- a/scripts/leaking_addresses.pl
> > > > +++ b/scripts/leaking_addresses.pl
> > > > @@ -24,6 +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';
> > > > @@ -37,18 +38,20 @@ 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 $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',
> > > > @@ -97,14 +100,16 @@ 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:
> > > >
> > > > @@ -117,7 +122,10 @@ 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);
> > > > @@ -133,6 +141,8 @@ 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 ($help);
> > > > @@ -148,6 +158,7 @@ if (!$input_raw and ($squash_by_path or $squash_by_filename)) {
> > > > exit(128);
> > > > }
> > > >
> > > > +show_detected_architecture() if $debug;
> > > > if (!is_supported_architecture()) {
> > > > printf "\nScript does not support your architecture, sorry.\n";
> > > > printf "\nCurrently we support: \n\n";
> > > > @@ -179,7 +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
> > > > @@ -202,10 +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
> > > > $match =~ '\b(0x)?0{16}\b') {
> > > > return 1;
> > > > @@ -222,6 +263,89 @@ sub is_false_positive
> > > > return 0;
> > > > }
> > > >
> > > > +sub is_false_positive_ix86_32
> > > > +{
> > > > + my ($match) = @_;
> > > > + state $page_offset = get_page_offset(); # only gets called once
> > >
> > > nit: new line here
> >
> > Will do
> > > > + if ($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 = hex("0xc0000000");
> > > > + my @config_files;
> > >
> > > my $tmp_file = "";
> > >
> > > See comments below for reasoning.
> > >
> > > > + # Allow --page-offset-32bit to override.
> > > > + if ($page_offset_32bit != 0) {
> > > > + return $page_offset_32bit;
> > > > + }
> > > > +
> > > > + # Allow --kernel-config-file to override.
> > > > + if ($kernel_config_file ne "") {
> > > > + @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";
> > >
> > > $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 ($page_offset ne "") {
> > > > + return hex($page_offset);
> > > > + }
> > > > + }
> > > > + system("rm -f $tmp_file");
> > > > + }
> > >
> > > The logic is a bit broken here. sub returns without rm'ing tmp file.
> >
> > Caught! :-) Thanks..
> >
> > > I
> > > believe we discussed using
> > >
> > > @config_files = ($tmp_file);
> > >
> > > Then continuing to iterate @config_files as done.
> >
> > I thought, why not just do this:
> >
> > 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 "") {
> > system("rm -f $tmp_file");
> > return hex($page_offset);
> > }
> > system("rm -f $tmp_file");
> > }
> > }
> >
> > Also, this way, the '$tmp_file' var remains localized to the handling of
> > the /proc/config.gz file 'if' statement scope.
> >
> > > > +
> > > > + foreach my $config_file (@config_files) {
> > > > + chomp $config_file;
> > > > + $page_offset = parse_kernel_config_file($config_file);
> > > > + if ($page_offset ne "") {
> > > > + return hex($page_offset);
> > > > + }
> > > > + }
> > >
> > > We may need to use 'last' instead of returning so we can check for
> > >
> > > if ($tmp_file ne "") {
> > > system("rm -f $tmp_file");
> > > }
> >
> > Not required, if we use the manner I propose above..
> > >
> > > And one final (particularly trivial) nitpick
> > >
> > > Can you use the brief commit log with prefix
> > >
> > > leaking_addresses:
> > >
> > > please. That prefix is what is currently used. Using 'scripts:' makes it
> > > hard to fit a descriptive message within 52 characters.
> > >
> >
> > Understood, sorry for the current patch series not using this style.
> >
> > > I know we have changed it already, but perhaps it should mention x86 not
> > > just 32 bit (since it is not 32 bit generic).
> > >
> > > I realized while reviewing your code that there is no reason for this to
> > > be x86 specific, if we can get a config file with CONFIG_PAGE_OFFSET
> > > then we can scan the kernel like this irrespective of architecture. Perl
> > > doesn't manage to correctly identify the RaspberryPi I tried it on as 32
> > > bit so we may not be able to do it how we currently are.
> >
> > Interesting..
> > >
> > > I'm mentioning this because I don't want you to go to all this work and
> > > then remove a bunch of your code immediately while making it 32 bit
> > > generic. If you want to work on a generic version then I'm happy to work
> > > with you on it.
> >
> > Sure, lets try for a generic ver! Thanks for your help on this..
> > As your experience woth the R Pi shows, we may have to just resort to building a
> > generic framework of sorts, letting folks "plugin" appropriate "truth values"
> > for their particular platform; this way, we support as much as we can for now
> > and, going forward, it's generic.
> > As of right now though, am unsure what this "generic framework" is..
> >
>
> A way forward, perhaps:
> uname -m
>
> Looks promising.
> The output on a few test platforms:
>
> +--------------+------------------+
> Platform/CPU | `uname -m` |
> +--------------+------------------+
> x86_64 | x86_64 |
> +--------------+------------------+
> x86-32 | i686 |
> +--------------+------------------+
> ARM-32 (yocto | armv5tejl |
> qemuarm32) | |
> +--------------+------------------+
> ARM64 (yocto | aarch64 |
> qemuarm64) | |
> +--------------+------------------+
> MIPS64 (yocto | mips64 |
> qemumips64) | |
> +--------------+------------------+
> ARM32 (qemu | armv7l |
> IMX6 Sabrelite)| |
> +--------------+------------------+
This would require an if/else clause with a statement for each
architecture. As Greg k-h likes to say, ugkh!
Tobin
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