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Message-ID: <20171218055746.GC4627@eros>
Date: Mon, 18 Dec 2017 16:57:46 +1100
From: "Tobin C. Harding" <me@...in.cc>
To: kaiwan.billimoria@...il.com
Cc: linux-kernel@...r.kernel.org,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH] leaking_addresses: add generic 32-bit support
On Mon, Dec 18, 2017 at 09:24:47AM +0530, kaiwan.billimoria@...il.com wrote:
> The script attempts to detect the architecture it's running upon; as of now,
> we explicitly support x86_64, PPC64 and x86_32.
> If it's one of them, we proceed "normally". If we fail to detect the arch,
> we fallback to 64-bit scanning, unless the user has passed either of these
> option switches: "--32-bit" and/or "--page-offset-32bit=<val>".
>
> If so, we switch to scanning for leaked addresses based on the value of
> PAGE_OFFSET (via an auto-detected or fallback mechanism).
>
> As of now, we have code (or "rules") to detect special cases for x86_64 and ppc64
> (in the get_address_re sub). Also, we now have also builtin "stubs", for lack of a better term,
> where additional rules for other 64-bit arch's can be plugged in, in future,
> as applicable.
>
> Signed-off-by: Kaiwan N Billimoria <kaiwan.billimoria@...il.com>
> ---
>
> This is a patch based on Tobin's latest tree, 'leaks' branch.
> Applies on top of commit 6c3942594657 (leaking_addresses: add support for 5 page table levels (origin/leaks))
That commit is not the tip of the branch. leaks branch is currently at
commit 266891c62bf0 (leaking_addresses: add support for 5 page table levels)
>
> Thanks,
> Kaiwan.
>
> scripts/leaking_addresses.pl | 213 +++++++++++++++++++++++++++++++++++++------
> 1 file changed, 184 insertions(+), 29 deletions(-)
>
> diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
> index a29e13e577a7..a667f243c95b 100755
> --- a/scripts/leaking_addresses.pl
> +++ b/scripts/leaking_addresses.pl
> @@ -1,10 +1,10 @@
> #!/usr/bin/env perl
> #
> # (c) 2017 Tobin C. Harding <me@...in.cc>
> -
> +# (c) 2017 Kaiwan N Billimoria <kaiwan.billimoria@...il.com>
> # 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 kernel for potential leaking addresses.
> # - Scans dmesg output.
> # - Walks directory tree and parses each file (for each directory in @DIRS).
> #
> @@ -35,7 +35,7 @@ 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;
> @@ -48,7 +48,9 @@ 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 $kernel_config_file = ""; # Kernel configuration file.
> +my $opt_32_bit = 0; # Detect 32-bit kernel leaking addresses.
> +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',
> @@ -97,17 +99,19 @@ Version: $V
>
> Options:
>
> - -o, --output-raw=<file> Save results for future processing.
> - -i, --input-raw=<file> Read results from file instead of scanning.
> - --raw Show raw results (default).
> - --suppress-dmesg Do not show dmesg results.
> - --squash-by-path Show one result per unique path.
> - --squash-by-filename Show one result per unique filename.
> - --kernel-config-file=<file> Kernel configuration file (e.g /boot/config)
> - -d, --debug Display debugging output.
> - -h, --help, --versionq Display this help and exit.
> + -o, --output-raw=<file> Save results for future processing.
> + -i, --input-raw=<file> Read results from file instead of scanning.
> + --raw Show raw results (default).
> + --suppress-dmesg Do not show dmesg results.
> + --squash-by-path Show one result per unique path.
> + --squash-by-filename Show one result per unique filename.
> + --32-bit Detect 32-bit kernel leaking addresses.
> + --page-offset-32bit=<hex> PAGE_OFFSET value (for 32-bit kernels).
> + --kernel-config-file=<file> Kernel configuration file (e.g /boot/config).
> + -d, --debug Display debugging output.
> + -h, --help, --version Display this help and exit.
We don't need this, it's already indented.
> -Scans the running (64 bit) kernel for potential leaking addresses.
> +Scans the running kernel for potential leaking addresses.
>
> EOM
> exit($exitcode);
> @@ -123,7 +127,9 @@ GetOptions(
> 'squash-by-path' => \$squash_by_path,
> 'squash-by-filename' => \$squash_by_filename,
> 'raw' => \$raw,
> - 'kernel-config-file=s' => \$kernel_config_file,
> + '32-bit' => \$opt_32_bit,
> + 'page-offset-32bit=o' => \$page_offset_32bit,
> + 'kernel-config-file=s' => \$kernel_config_file,
Perhaps
$opt_32bit so as to be consistent.
> ) or help(1);
>
> help(0) if ($help);
> @@ -139,11 +145,16 @@ if (!$input_raw and ($squash_by_path or $squash_by_filename)) {
> exit(128);
> }
>
> -if (!is_supported_architecture()) {
> - printf "\nScript does not support your architecture, sorry.\n";
> - printf "\nCurrently we support: \n\n";
> - foreach(@SUPPORTED_ARCHITECTURES) {
> - printf "\t%s\n", $_;
> +show_detected_architecture() if $debug;
> +
> +if (!is_known_architecture()) {
> + printf STDERR "\n*** WARNING! Script does not recognize your architecture ***\n";
> + if ($opt_32_bit or $page_offset_32bit) {
> + printf STDERR "Scanning for 32-bit leaking kernel addresses\n\n";
> + } else {
> + printf STDERR "Scanning for 64-bit leaking kernel addresses\n";
> + printf STDERR "If you\'d rather scan for 32-bit addresses, use the ";
> + printf STDERR "--32-bit (and --page-offset-32bit=) option switch(es).\n\n";
> }
>
> my $archname = $Config{archname};
> @@ -168,9 +179,14 @@ sub dprint
> printf(STDERR @_) if $debug;
> }
>
> -sub is_supported_architecture
> +sub is_known_architecture
> +{
> + return (is_64bit() or is_ix86_32());
> +}
> +
> +sub is_64bit
> {
> - return (is_x86_64() or is_ppc64());
> + return (is_x86_64() or is_ppc64() or is_arm64() or is_mips64());
> }
Perhaps we could have
sub is_32bit
{
if ($opt_32bit or $page_offset_32bit) {
return 1;
}
if (is_ix86_32()) {
return 1;
}
return 0;
}
>
> sub is_x86_64
> @@ -193,6 +209,50 @@ sub is_ppc64
> return 0;
> }
>
> +sub is_arm64
> +{
> + if (`uname -m` eq "aarch64") {
> + return 1;
> + }
> + return 0;
> +}
> +
> +sub is_mips64
> +{
> + if (`uname -m` eq "mips64") {
> + return 1;
> + }
> + return 0;
> +}
> +
> +sub is_ix86_32
> +{
> + my $archname = $Config{archname};
> +
> + if ($archname =~ m/i[3456]86-linux/) {
> + return 1;
> + }
> + return 0;
> +}
Why do we use $Config{archname} here and `uname -m` above? Can we use
just one of them? If so we could have a helper function
sub is_arch()
{
my ($desc) = @_;
if (`uname -m` eq $desc) {
return 1;
}
return 0;
}
and
is_mips64 { is_arch("mips64"); }
...
> +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";
We probably should use capitals for PPC64 since ARM and MIPS get capitals.
> + } elsif (is_arm64()) {
> + printf "ARM64\n";
> + } elsif (is_mips64()) {
> + printf "MIPS64\n";
> + } else {
> + printf "failed to detect architecture\n"
> + }
> +}
> +
> # gets config option value from kernel config file
> sub get_kernel_config_option
> {
> @@ -220,7 +280,8 @@ sub get_kernel_config_option
> }
>
> foreach my $file (@config_files) {
> - dprint("parsing config file: %s\n", $file);
> + printf("file: %s\n", $file) if $debug;
We should actually just remove this debugging line all together, it will
be overly verbose and not that useful (see below).
> $value = option_from_file($option, $file);
> if ($value ne "") {
> last;
> @@ -258,6 +319,14 @@ sub is_false_positive
> {
> my ($match) = @_;
>
> + # 32 bit architectures, actual or forced
> +
> + if (!is_64bit() and ($opt_32_bit or $page_offset_32bit)) {
> + return is_false_positive_32bit($match);
> + }
and now we could have just
if (is_32_bit()) {
...
> +
> + # 64 bit architectures
> +
> if ($match =~ '\b(0x)?(f|F){16}\b' or
> $match =~ '\b(0x)?0{16}\b') {
> return 1;
> @@ -281,6 +350,91 @@ sub is_in_vsyscall_memory_region
> return ($hex >= $region_min and $hex <= $region_max);
> }
>
> +sub is_false_positive_32bit
> +{
> + my ($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);
Remember we don't like 'eval' :) Just make sure your code does not
generate warnings in the first place.
> + if ($addr32 < $page_offset) {
> + return 1;
> + }
> +
> + return 0;
> +}
> +
> +sub get_page_offset
> +{
> + my $page_offset;
> + my $default_offset = hex("0xc0000000");
> + my @config_files;
> +
> + # Allow --page-offset-32bit to override.
> + if ($page_offset_32bit != 0) {
> + return $page_offset_32bit;
> + }
We don't need the rest of this function since we now have
get_kernel_config_option('CONFIG_PAGE_OFFSET');
And using this for CONFIG_PAGE_OFFSET after we have done so for
CONFIG_PGTABLE_LEVELS is why I suggest above removing debugging line.
> +
> + # Allow --kernel-config-file to override.
> + if ($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";
> + if (system("gunzip < /proc/config.gz > $tmp_file")) {
> + dprint " parse_kernel_config: system(gunzip...) failed\n";
> + system("rm -f $tmp_file 2>/dev/null");
> + } else {
> + $page_offset = parse_kernel_config_file($tmp_file);
> + system("rm -f $tmp_file");
> + if ($page_offset ne "") {
> + return hex($page_offset);
> + }
> + }
> + }
> +
> + 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);
> + }
> + }
> +
> + printf STDERR "\nFailed to parse kernel config files\n";
> + printf STDERR "*** NOTE ***\n";
> + printf STDERR "Falling back to PAGE_OFFSET = %#x\n\n", $default_offset;
> +
> + return $default_offset;
> +}
> +
> +sub parse_kernel_config_file
> +{
> + my ($file) = @_;
> + my $config = 'CONFIG_PAGE_OFFSET';
> + my $str = "";
> + my $val = "";
> +
> + open(my $fh, "<", $file) or return "";
> + while (my $line = <$fh> ) {
> + if ($line =~ /^$config/) {
> + ($str, $val) = split /=/, $line;
> + chomp($val);
> + last;
> + }
> + }
> +
> + close $fh;
> + return $val;
> +}
> +
> # True if argument potentially contains a kernel address.
> sub may_leak_address
> {
> @@ -300,7 +454,7 @@ sub may_leak_address
> }
>
> $address_re = get_address_re();
> - dprint("Kernel address regular expression: %s\n", $address_re);
> +# dprint("Kernel address regular expression: %s\n", $address_re);
Just remove this line altogether (I assume it annoyed you while
debugging).
> while (/($address_re)/g) {
> if (!is_false_positive($1)) {
> @@ -313,16 +467,17 @@ sub may_leak_address
>
> sub get_address_re
> {
> - my $re;
> + my $re = "";
>
> if (is_x86_64()) {
> $re = get_x86_64_re();
> } elsif (is_ppc64()) {
> $re = '\b(0x)?[89abcdef]00[[:xdigit:]]{13}\b';
} elsif (is_32bit())
$re = '\b(0x)?[[:xdigit:]]{8}\b';
> - }
> -
> - if ($re eq "") {
> - print STDERR "$0: failed to build kernel address regular expression\n";
And then we can leave this as is.
> + ###
> + # Any special cases for other arch's go below this line
> + ###
> + } else { # nothing? then we assume it's a generic 32-bit
> + $re = '\b(0x)?[[:xdigit:]]{8}\b';
> }
>
> return $re;
> --
> 2.14.3
thanks,
Tobin.
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