[kernel-hardening] [PATCH 1/2] scripts: leaking_addresses: add support for 32-bit kernel addresses

[kaiwan.billimoria@gmail.com]

The current leaking_addresses.pl script only supports showing "leaked"
64-bit kernel virtual addresses. This patch adds support for showing
"leaked" 32-bit kernel virtual addresses. It also takes into account Tobin's
feedback on the previous iteration. (Note: this patch is meant to apply on
the 'leaks' branch of Tobin's tree).

Briefly, the way it works- once it detects we're running on an i'x'86 platform,
(where x=3|4|5|6), it takes this arch into account for checking. The essential rationale:
 if virt-addr >= PAGE_OFFSET => it's a kernel virtual address.

This version programatically queries and sets PAGE_OFFSET based on the
/boot/config-$(uname -r) content. If, for any reason, this file cannot be
used, we fallback to requesting the user to pass PAGE_OFFSET as a parameter.

Pending/TODO:
- support for ARM-32

Feedback welcome..


Signed-off-by: Kaiwan N Billimoria <kaiwan.billimoria@gmail.com>
---
diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
index 865c07649dff..0566f8055ec5 100755
--- a/scripts/leaking_addresses.pl
+++ b/scripts/leaking_addresses.pl
@@ -2,10 +2,10 @@
 #
 # (c) 2017 Tobin C. Harding <me@tobin.cc>
 # (c) 2017 Kaiwan N Billimoria <kaiwan.billimoria@gmail.com> (ix86 support)
- 
+
 # 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 32/64 bit kernel for potential leaking addresses.
 #  - Scans dmesg output.
 #  - Walks directory tree and parses each file (for each directory in @DIRS).
 #
@@ -14,7 +14,7 @@
 #
 # You may like to set kptr_restrict=2 before running script
 # (see Documentation/sysctl/kernel.txt).
-
+#
 use warnings;
 use strict;
 use POSIX;
@@ -37,7 +37,7 @@ 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;
@@ -49,6 +49,12 @@ 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_param = 0;      # 32-bit: overrides value of PAGE_OFFSET_32BIT
+
+my $bit_size = 64;      # Check 64-bit kernel addresses by default
+my $kconfig_file = '/boot/config-'.`uname -r`;
+$kconfig_file =~ s/\R*//g;
+my $PAGE_OFFSET_32BIT = 0xc0000000;
 
 # Do not parse these files (absolute path).
 my @skip_parse_files_abs = ('/proc/kmsg',
@@ -99,10 +105,11 @@ 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.
+	--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=<hex>      PAGE_OFFSET value (for 32-bit kernels).
 	-d, --debug              Display debugging output.
 	-h, --help, --version    Display this help and exit.
 
@@ -117,7 +124,7 @@ Examples:
 	# View summary report.
 	$0 --input-raw scan.out --squash-by-filename
 
-Scans the running (64 bit) kernel for potential leaking addresses.
+Scans the running (32 or 64 bit) kernel for potential leaking addresses.
 
 EOM
 	exit($exitcode);
@@ -133,10 +140,16 @@ GetOptions(
 	'squash-by-path'        => \$squash_by_path,
 	'squash-by-filename'    => \$squash_by_filename,
 	'raw'                   => \$raw,
+	'page-offset=o'         => \$page_offset_param,
 ) or help(1);
 
 help(0) if ($help);
 
+sub dprint
+{
+	printf(STDERR @_) if $debug;
+}
+
 if ($input_raw) {
 	format_output($input_raw);
 	exit(0);
@@ -162,6 +175,24 @@ if (!is_supported_architecture()) {
 	exit(129);
 }
 
+dprint "Detected arch : $bit_size bits\n";
+
+if ($bit_size == 32) {
+	# Parameter --page-offset passed? if Y, override with it
+	if ($page_offset_param != 0) {
+		$PAGE_OFFSET_32BIT = $page_offset_param;
+	} else {
+		$PAGE_OFFSET_32BIT = eval parse_kconfig($kconfig_file, "CONFIG_PAGE_OFFSET");
+		if ($PAGE_OFFSET_32BIT == 0) {
+			printf "$P: Fatal Error :: couldn't parse CONFIG_PAGE_OFFSET, aborting...\n";
+			printf " [Detail :: arch=32-bit, kconfig file=$kconfig_file]\n\n";
+			printf "You can pass it as a parameter via the --page-offset= option switch.\n";
+			exit(1);
+		}
+	}
+	dprint "PAGE_OFFSET = 0x%X\n", $PAGE_OFFSET_32BIT;
+}
+
 if ($output_raw) {
 	open my $fh, '>', $output_raw or die "$0: $output_raw: $!\n";
 	select $fh;
@@ -172,14 +203,9 @@ walk(@DIRS);
 
 exit 0;
 
-sub dprint
-{
-	printf(STDERR @_) if $debug;
-}
-
 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
@@ -187,6 +213,7 @@ sub is_x86_64
 	my $archname = $Config{archname};
 
 	if ($archname =~ m/x86_64/) {
+		$bit_size = 64;
 		return 1;
 	}
 	return 0;
@@ -197,6 +224,19 @@ sub is_ppc64
 	my $archname = $Config{archname};
 
 	if ($archname =~ m/powerpc/ and $archname =~ m/64/) {
+		$bit_size = 64;
+		return 1;
+	}
+	return 0;
+}
+
+# 32-bit x86: is_i'x'86_32() ; where is [3 or 4 or 5 or 6]
+sub is_ix86_32
+{
+	my $archname = $Config{archname};
+
+	if ($archname =~ m/i[3456]86-linux/) {
+		$bit_size = 32;
 		return 1;
 	}
 	return 0;
@@ -217,6 +257,14 @@ sub is_false_positive
 		    $match =~ '\bf{10}601000\b') {
 			return 1;
 		}
+	} elsif ($bit_size == 32) {
+		my $addr32 = eval hex($match);
+		if ($addr32 < $PAGE_OFFSET_32BIT ) {
+			return 1;
+		}
+		if ($match =~ '\b(0x)?(f|F){8}\b') {
+			return 1;
+		}
 	}
 
 	return 0;
@@ -245,6 +293,8 @@ sub may_leak_address
 		$address_re = '\b(0x)?ffff[[:xdigit:]]{12}\b';
 	} elsif (is_ppc64()) {
 		$address_re = '\b(0x)?[89abcdef]00[[:xdigit:]]{13}\b';
+	} elsif (is_ix86_32()) {
+		$address_re = '\b(0x)?[[:xdigit:]]{8}\b';
 	}
 
 	while (/($address_re)/g) {
@@ -501,3 +551,28 @@ sub add_to_cache
 	}
 	push @{$cache->{$key}}, $value;
 }
+
+sub parse_kconfig
+{
+	my ($file,$config) = @_;
+	my $str;
+	my $val=NULL;
+
+	if (! -R $file) {
+               return NULL;
+	}
+
+	open my $fh, "<", $file or return;
+	while (my $line = <$fh> ) {
+		if ($line =~ /^$config/) {
+			($str,$val) = split /=/, $line;
+		}
+	}
+	close $fh;
+
+	if ($val eq NULL) {
+		return NULL;
+	}
+	$val =~ s/\R*//g;
+	return $val;
+}