linux-hardening - [PATCH] leaking_addresses: Provide mechanism to scan binary files

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Message-Id: <20240218173809.work.286-kees@kernel.org>
Date: Sun, 18 Feb 2024 09:38:12 -0800
From: Kees Cook <keescook@...omium.org>
To: "Tobin C. Harding" <me@...in.cc>
Cc: Kees Cook <keescook@...omium.org>,
	Tycho Andersen <tycho@...ho.pizza>,
	Greg KH <gregkh@...uxfoundation.org>,
	Guixiong Wei <guixiongwei@...il.com>,
	linux-hardening@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] leaking_addresses: Provide mechanism to scan binary files

Introduce --kallsyms argument for scanning binary files for known symbol
addresses. This would have found the exposure in /sys/kernel/notes:

$ scripts/leaking_addresses.pl --kallsyms=<(sudo cat /proc/kallsyms)
/sys/kernel/notes: hypercall_page @ 156
/sys/kernel/notes: xen_hypercall_set_trap_table @ 156
/sys/kernel/notes: startup_xen @ 132

Signed-off-by: Kees Cook <keescook@...omium.org>
---
Cc: "Tobin C. Harding" <me@...in.cc>
Cc: Tycho Andersen <tycho@...ho.pizza>
Cc: Greg KH <gregkh@...uxfoundation.org>
Cc: Guixiong Wei <guixiongwei@...il.com>
Cc: linux-hardening@...r.kernel.org
---
 scripts/leaking_addresses.pl | 53 ++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
index e695634d153d..cbaa17c244cc 100755
--- a/scripts/leaking_addresses.pl
+++ b/scripts/leaking_addresses.pl
@@ -51,10 +51,13 @@ 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 $kallsyms_file = "";		# Kernel symbols file.
 my $kernel_config_file = "";	# Kernel configuration file.
 my $opt_32bit = 0;		# Scan 32-bit kernel.
 my $page_offset_32bit = 0;	# Page offset for 32-bit kernel.
 
+my @kallsyms = ();
+
 # Skip these absolute paths.
 my @skip_abs = (
 	'/proc/kmsg',
@@ -95,6 +98,8 @@ 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)
+	--kallsyms=<file>		Read kernel symbol addresses from file (for
+						scanning binary files).
 	--32-bit			Scan 32-bit kernel.
 	--page-offset-32-bit=o		Page offset (for 32-bit kernel 0xABCD1234).
 	-d, --debug			Display debugging output.
@@ -115,6 +120,7 @@ GetOptions(
 	'squash-by-path'        => \$squash_by_path,
 	'squash-by-filename'    => \$squash_by_filename,
 	'raw'                   => \$raw,
+	'kallsyms=s'            => \$kallsyms_file,
 	'kernel-config-file=s'	=> \$kernel_config_file,
 	'32-bit'		=> \$opt_32bit,
 	'page-offset-32-bit=o'	=> \$page_offset_32bit,
@@ -155,6 +161,25 @@ if ($output_raw) {
 	select $fh;
 }
 
+if ($kallsyms_file) {
+	open my $fh, '<', $kallsyms_file or die "$0: $kallsyms_file: $!\n";
+	while (<$fh>) {
+		chomp;
+		my @entry = split / /, $_;
+		my $addr_text = $entry[0];
+		# TODO: Why is hex() so impossibly slow?
+		my $addr = hex($addr_text);
+		my $symbol = $entry[2];
+		# Only keep kernel text addresses.
+		if ($addr_text !~ /^0/) {
+			my $long = pack("J", $addr);
+			my $entry = [$long, $symbol];
+			push @kallsyms, $entry;
+		}
+	}
+	close $fh;
+}
+
 parse_dmesg();
 walk(@DIRS);
 
@@ -442,6 +467,25 @@ sub timed_parse_file
 	}
 }
 
+sub parse_binary
+{
+	my ($file) = @_;
+
+	open my $fh, "<:raw", $file or return;
+	local $/ = undef;
+	my $bytes = <$fh>;
+	close $fh;
+
+	foreach my $entry (@kallsyms) {
+		my $addr = $entry->[0];
+		my $symbol = $entry->[1];
+		my $offset = index($bytes, $addr);
+		if ($offset != -1) {
+			printf("$file: $symbol @ $offset\n");
+		}
+	}
+}
+
 sub parse_file
 {
 	my ($file) = @_;
@@ -451,6 +495,15 @@ sub parse_file
 	}
 
 	if (! -T $file) {
+		if ($file =~ m|^/sys/kernel/btf/| or
+		    $file =~ m|^/sys/devices/pci| or
+		    $file =~ m|^/sys/firmware/efi/efivars/| or
+		    $file =~ m|^/proc/bus/pci/|) {
+			return;
+		}
+		if (scalar @kallsyms > 0) {
+			parse_binary($file);
+		}
 		return;
 	}
 
-- 
2.34.1