Re: [PATCH v5] leaking_addresses: add generic 32-bit support

kaiwan.billimoria
2018-01-05T01:52:56Z

As a follow-up, pl see below some quick test cases on an emulated ARM32
platform (the Yocto-based qemuarm32 ARM Versatile):

root@qemuarm:~# ./leaking_addresses.pl

FATAL: Script does not recognize your architecture

$ uname -m
armv5tejl
root@qemuarm:~#

As expected..
Now running with the '--opt-32bit' switch, forcing 32-bit mode:

root@qemuarm:~# ./leaking_addresses.pl --opt-32bit
dmesg: [ 0.000000] free_area_init_node: node 0, pgdat c0a2bff4, node_mem_map cfdb9000
dmesg: vector : 0xffff0000 - 0xffff1000 ( 4 kB)
dmesg: fixmap : 0xffc00000 - 0xfff00000 (3072 kB)
dmesg: vmalloc : 0xd0800000 - 0xff800000 ( 752 MB)
dmesg: lowmem : 0xc0000000 - 0xd0000000 ( 256 MB)
dmesg: modules : 0xbf000000 - 0xc0000000 ( 16 MB)
dmesg: .text : 0xc0008000 - 0xc06bb388 (6861 kB)
dmesg: .init : 0xc0944000 - 0xc09aa000 ( 408 kB)
dmesg: .data : 0xc09aa000 - 0xc0a3195c ( 543 kB)
dmesg: .bss : 0xc0a3195c - 0xc0ad2f68 ( 646 kB)
dmesg: [ 0.000000] VIC @d0800000: id 0x00041190, vendor 0x41
dmesg: [ 0.000000] FPGA IRQ chip 0 "intc" @ d0802000, 20 irqs, parent IRQ: 47
^C

Above: works, with PAGE_OFFSET being auto-detected to 0xc0000000
Below: now explicitly set the PAGE_OFFSET to 0xe0000000:

root@qemuarm:~# ./leaking_addresses.pl -d --opt-32bit --page-offset-32bit=0xe0000000
Detected architecture: 32 bit
dmesg: vector : 0xffff0000 - 0xffff1000 ( 4 kB)
dmesg: fixmap : 0xffc00000 - 0xfff00000 (3072 kB)
dmesg: vmalloc : 0xd0800000 - 0xff800000 ( 752 MB)
parsing: /proc/fb
parsing: /proc/mtd
parsing: /proc/keys
skipping file: /proc/kmsg
parsing: /proc/misc
parsing: /proc/stat
^C
root@qemuarm:~#

Above test case also works identically if we omit the '--opt-32bit' switch.

Thanks,
Kaiwan.

On Thu, 2018-01-04 at 17:51 +0530, kaiwan.billimoria@gmail.com wrote:
> The script now attempts to detect the architecture it's running upon; as of now,
> we explicitly support x86_64, PPC64, ARM64, MIPS64 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: "--opt-32bit" 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).
>
> Currently, code (or "rules") to detect special cases for x86_64, PPC64 and Aarch64
> (in the get_address_re sub) is present. 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 into the code, in future, as applicable.
>
> This patch adds support for ix86 and generic 32 bit architectures.
> - Add command line option for generic 32-bit checking.
> - 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.
>
> The script has been lightly tested on the following systems:
> x86_64
> x86_32 (on a i686 running Debian 7 to be precise)
> ARM32 (on a Yocto-based qemuarm32 ARM Versatile platform (ARM926EJ-S cpu))
>
> In the first two cases, one just has to run the script - no parameters required.
> In the ARM-32 case, it will, by design, fail to detect the architecture;
> (re)running it with the '--32-bit' and/or the '--page-offset-32bit=<hexval>'
> option switch(es) has the desired effect: it now detects 32-bit leaking kernel
> addresses, if any.
>
> Request more testing on the above and other platforms.
>
>
> Signed-off-by: Kaiwan N Billimoria <kaiwan.billimoria@gmail.com>
>
> ---
> scripts/leaking_addresses.pl | 190 +++++++++++++++++++++++++++++++++++--------
> 1 file changed, 156 insertions(+), 34 deletions(-)
>
> diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
> index a29e13e577a7..b0807b3a3c7c 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@tobin.cc>
> -
> +# (c) 2017 Kaiwan N Billimoria <kaiwan.billimoria@gmail.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).
> #
> @@ -32,11 +32,6 @@ my @DIRS = ('/proc', '/sys');
> # Timer for parsing each file, in seconds.
> 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');
> -
> # Command line options.
> my $help = 0;
> my $debug = 0;
> @@ -48,7 +43,9 @@ 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 (only) 32-bit kernel leaking addresses.
> +my $page_offset_32bit = 0; # 32-bit: value of CONFIG_PAGE_OFFSET.
> +my $kernel_config_file = ""; # Kernel configuration file.
>
> # Do not parse these files (absolute path).
> my @skip_parse_files_abs = ('/proc/kmsg',
> @@ -104,10 +101,12 @@ Options:
> --squash-by-path Show one result per unique path.
> --squash-by-filename Show one result per unique filename.
> --kernel-config-file=<file> Kernel configuration file (e.g /boot/config)
> + --opt-32bit Detect (only) 32-bit kernel leaking addresses.
> + --page-offset-32bit=<hex> PAGE_OFFSET value (for 32-bit kernels).
> -d, --debug Display debugging output.
> - -h, --help, --versionq Display this help and exit.
> + -h, --help, --version Display this help and exit.
>
> -Scans the running (64 bit) kernel for potential leaking addresses.
> +Scans the running kernel for potential leaking addresses.
>
> EOM
> exit($exitcode);
> @@ -123,7 +122,9 @@ GetOptions(
> 'squash-by-path' => \$squash_by_path,
> 'squash-by-filename' => \$squash_by_filename,
> 'raw' => \$raw,
> - 'kernel-config-file=s' => \$kernel_config_file,
> + 'opt-32bit' => \$opt_32_bit,
> + 'page-offset-32bit=o' => \$page_offset_32bit,
> + 'kernel-config-file=s' => \$kernel_config_file,
> ) or help(1);
>
> help(0) if ($help);
> @@ -139,16 +140,15 @@ if (!$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;
>
> - my $archname = $Config{archname};
> - printf "\n\$ perl -MConfig -e \'print \"\$Config{archname}\\n\"\'\n";
> - printf "%s\n", $archname;
> +if (!is_known_architecture()) {
> + printf STDERR "\nFATAL: Script does not recognize your architecture\n";
> +
> + my $arch = `uname -m`;
> + chomp $arch;
> + printf "\n\$ uname -m\n";
> + printf "%s\n", $arch;
>
> exit(129);
> }
> @@ -168,21 +168,45 @@ sub dprint
> printf(STDERR @_) if $debug;
> }
>
> -sub is_supported_architecture
> +sub is_known_architecture
> {
> - return (is_x86_64() or is_ppc64());
> + return (is_64bit() or is_32bit());
> }
>
> -sub is_x86_64
> +sub is_32bit
> {
> - my $archname = $Config{archname};
> + # 32-bit actual case
> + if (is_ix86_32()) {
> + return 1;
> + }
>
> - if ($archname =~ m/x86_64/) {
> + # 32-bit "forced" case (for any arch other than IA-32)
> + if ($opt_32_bit or $page_offset_32bit) {
> return 1;
> }
> return 0;
> }
>
> +sub is_64bit
> +{
> + return (is_x86_64() or is_ppc64() or is_arm64() or is_mips64());
> +}
> +
> +sub is_x86_64
> +{
> + is_arch("x86_64");
> +}
> +
> +sub is_arm64
> +{
> + is_arch("aarch64");
> +}
> +
> +sub is_mips64
> +{
> + is_arch("mips64");
> +}
> +
> sub is_ppc64
> {
> my $archname = $Config{archname};
> @@ -193,6 +217,47 @@ sub is_ppc64
> return 0;
> }
>
> +sub is_ix86_32
> +{
> + my $arch = `uname -m`;
> +
> + chomp $arch;
> + if ($arch =~ m/i[3456]86/) {
> + return 1;
> + }
> + return 0;
> +}
> +
> +sub is_arch
> +{
> + my ($desc) = @_;
> + my $arch = `uname -m`;
> +
> + chomp $arch;
> + if ($arch eq $desc) {
> + return 1;
> + }
> + return 0;
> +}
> +
> +sub show_detected_architecture
> +{
> + printf "Detected architecture: ";
> + if (is_32bit()) {
> + printf "32 bit\n";
> + } elsif (is_x86_64()) {
> + printf "x86_64\n";
> + } elsif (is_ppc64()) {
> + printf "PPC64\n";
> + } elsif (is_arm64()) {
> + printf "ARM64\n";
> + } elsif (is_mips64()) {
> + printf "MIPS64\n";
> + } else {
> + printf "failed to detect architecture\n"
> + }
> +}
> +
> # gets config option value from kernel config file
> sub get_kernel_config_option
> {
> @@ -212,7 +277,6 @@ sub get_kernel_config_option
> } else {
> @config_files = ($tmp_file);
> }
> -
> } else {
> my $file = '/boot/config-' . `uname -r`;
> chomp $file;
> @@ -220,7 +284,6 @@ sub get_kernel_config_option
> }
>
> foreach my $file (@config_files) {
> - dprint("parsing config file: %s\n", $file);
> $value = option_from_file($option, $file);
> if ($value ne "") {
> last;
> @@ -258,6 +321,14 @@ sub is_false_positive
> {
> my ($match) = @_;
>
> + # 32 bit architectures, actual or forced
> +
> + if (is_32bit()) {
> + return is_false_positive_32bit($match);
> + }
> +
> + # 64 bit architectures
> +
> if ($match =~ '\b(0x)?(f|F){16}\b' or
> $match =~ '\b(0x)?0{16}\b') {
> return 1;
> @@ -281,6 +352,58 @@ sub is_in_vsyscall_memory_region
> return ($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 $addr32 = hex($match);
> + if ($addr32 < $page_offset) {
> + return 1;
> + }
> +
> + return 0;
> +}
> +
> +sub get_page_offset
> +{
> + my $page_offset;
> + my $default_offset = hex("0xc0000000");
> + my @config_files;
> +
> + # Allow --page-offset-32bit to override.
> + if ($page_offset_32bit != 0) {
> + return $page_offset_32bit;
> + }
> +
> + $page_offset = get_kernel_config_option('CONFIG_PAGE_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
> {
> @@ -300,8 +423,6 @@ sub may_leak_address
> }
>
> $address_re = get_address_re();
> - dprint("Kernel address regular expression: %s\n", $address_re);
> -
> while (/($address_re)/g) {
> if (!is_false_positive($1)) {
> return 1;
> @@ -313,16 +434,17 @@ sub may_leak_address
>
> sub get_address_re
> {
> - my $re;
> + my $re = "";
>
> if (is_x86_64()) {
> $re = get_x86_64_re();
> } elsif (is_ppc64()) {
> $re = '\b(0x)?[89abcdef]00[[:xdigit:]]{13}\b';
> - }
> -
> - if ($re eq "") {
> - print STDERR "$0: failed to build kernel address regular expression\n";
> + ###
> + # 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;