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

kaiwan.billimoria
2018-01-04T12:21:35Z

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;
--
2.14.3