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Diffstat (limited to 'scripts/hardening-check.pl')
| -rwxr-xr-x | scripts/hardening-check.pl | 684 |
1 files changed, 684 insertions, 0 deletions
diff --git a/scripts/hardening-check.pl b/scripts/hardening-check.pl new file mode 100755 index 0000000..ad7f4e4 --- /dev/null +++ b/scripts/hardening-check.pl @@ -0,0 +1,684 @@ +#!/usr/bin/perl +# Report the hardening characteristics of a set of binaries. +# Copyright (C) 2009-2013 Kees Cook <kees@debian.org> +# License: GPLv2 or newer +use strict; +use warnings; +use Getopt::Long qw(:config no_ignore_case bundling); +use Pod::Usage; +use IPC::Open3; +use Symbol qw(gensym); +use Term::ANSIColor; +use IO::Select; + +my $skip_pie = 0; +my $skip_stackprotector = 0; +my $skip_fortify = 0; +my $skip_relro = 0; +my $skip_bindnow = 0; +my $skip_cfprotection = 0; +my $report_functions = 0; +my $find_libc_functions = 0; +my $color = 0; +my $lintian = 0; +my $verbose = 0; +my $debug = 0; +my $quiet = 0; +my $help = 0; +my $man = 0; + +GetOptions( + "nopie|p+" => \$skip_pie, + "nostackprotector|s+" => \$skip_stackprotector, + "nofortify|f+" => \$skip_fortify, + "norelro|r+" => \$skip_relro, + "nobindnow|b+" => \$skip_bindnow, + "nocfprotection|x+" => \$skip_cfprotection, + "report-functions|R!" => \$report_functions, + "find-libc-functions|F!" => \$find_libc_functions, + "color|c!" => \$color, + "lintian|l!" => \$lintian, + "verbose|v!" => \$verbose, + "debug!" => \$debug, + "quiet|q!" => \$quiet, + "help|h|?" => \$help, + "man|H" => \$man, +) or pod2usage(2); +pod2usage(1) if $help; +pod2usage(-exitstatus => 0, -verbose => 2, -noperldoc => 1) if $man; + +my $overall = 0; +my $rc = 0; +my $report = ""; +my @tags; +my %libc = ( + 'asprintf' => 1, + 'confstr' => 1, + 'dprintf' => 1, + 'fdelt' => 1, + 'fgets' => 1, + 'fgets_unlocked' => 1, + 'fgetws' => 1, + 'fgetws_unlocked' => 1, + 'fprintf' => 1, + 'fread' => 1, + 'fread_unlocked' => 1, + 'fwprintf' => 1, + 'getcwd' => 1, + 'getdomainname' => 1, + 'getgroups' => 1, + 'gethostname' => 1, + 'getlogin_r' => 1, + 'gets' => 1, + 'getwd' => 1, + 'longjmp' => 1, + 'mbsnrtowcs' => 1, + 'mbsrtowcs' => 1, + 'mbstowcs' => 1, + 'memcpy' => 1, + 'memmove' => 1, + 'mempcpy' => 1, + 'memset' => 1, + 'obstack_printf' => 1, + 'obstack_vprintf' => 1, + 'poll' => 1, + 'ppoll' => 1, + 'pread64' => 1, + 'pread' => 1, + 'printf' => 1, + 'ptsname_r' => 1, + 'read' => 1, + 'readlink' => 1, + 'readlinkat' => 1, + 'realpath' => 1, + 'recv' => 1, + 'recvfrom' => 1, + 'snprintf' => 1, + 'sprintf' => 1, + 'stpcpy' => 1, + 'stpncpy' => 1, + 'strcat' => 1, + 'strcpy' => 1, + 'strncat' => 1, + 'strncpy' => 1, + 'swprintf' => 1, + 'syslog' => 1, + 'ttyname_r' => 1, + 'vasprintf' => 1, + 'vdprintf' => 1, + 'vfprintf' => 1, + 'vfwprintf' => 1, + 'vprintf' => 1, + 'vsnprintf' => 1, + 'vsprintf' => 1, + 'vswprintf' => 1, + 'vsyslog' => 1, + 'vwprintf' => 1, + 'wcpcpy' => 1, + 'wcpncpy' => 1, + 'wcrtomb' => 1, + 'wcscat' => 1, + 'wcscpy' => 1, + 'wcsncat' => 1, + 'wcsncpy' => 1, + 'wcsnrtombs' => 1, + 'wcsrtombs' => 1, + 'wcstombs' => 1, + 'wctomb' => 1, + 'wmemcpy' => 1, + 'wmemmove' => 1, + 'wmempcpy' => 1, + 'wmemset' => 1, + 'wprintf' => 1, +); + +# Report a good test. +sub good { + my ($name, $msg_color, $msg) = @_; + $msg_color = colored($msg_color, 'green') if $color; + if (defined $msg) { + $msg_color .= $msg; + } + good_msg("$name: $msg_color"); +} + +sub good_msg($) { + my ($msg) = @_; + if ($quiet == 0) { + $report .= "\n$msg"; + } +} + +sub unknown { + my ($name, $msg) = @_; + $msg = colored($msg, 'yellow') if $color; + good_msg("$name: $msg"); +} + +# Report a failed test, possibly ignoring it. +sub bad($$$$$) { + my ($name, $file, $long_name, $msg, $ignore) = @_; + + $msg = colored($msg, 'red') if $color; + + $msg = "$long_name: " . $msg; + if ($ignore) { + $msg .= " (ignored)"; + } else { + $rc = 1; + if ($lintian) { + push(@tags, "$name:$file"); + } + } + $report .= "\n$msg"; +} + +# Safely run list-based command line and return stdout. +sub output(@) { + my (@cmd) = @_; + my ($pid, $stdout, $stderr); + if ($debug) { + print join(" ", @cmd), "\n"; + } + $stdout = gensym; + $stderr = gensym; + $pid = open3(gensym, $stdout, $stderr, @cmd); + + my $selector = IO::Select->new(); + $selector->add($stdout); + $selector->add($stderr); + + my $collect_out = ""; + my $collect_err = ""; + + while (my @ready = $selector->can_read()) { + foreach my $fh (@ready) { + my $buf; + my $len = sysread($fh, $buf, 4096); + if ($len == 0) { + $selector->remove($fh); + next; + } + + if ($fh == $stdout) { + $collect_out .= $buf; + } else { + $collect_err .= $buf; + } + } + } + + waitpid($pid, 0); + my $rc = $?; + if ($rc != 0) { + print STDERR $collect_err; + return ""; + } + return $collect_out; +} + +# Find the libc used in this executable, if any. +sub find_libc($) { + my ($file) = @_; + my $ldd = output("ldd", $file); + $ldd =~ /^\s*libc\.so\.\S+\s+\S+\s+(\S+)/m; + return $1 || ""; +} + +sub find_functions($$) { + my ($file, $undefined) = @_; + my (%funcs); + + # Catch "NOTYPE" for object archives. + my $func_regex = " (I?FUNC|NOTYPE) "; + + my $relocs = output("readelf", "-sW", $file); + for my $line (split("\n", $relocs)) { + next if ($line !~ /$func_regex/); + next if ($undefined && $line !~ /$func_regex.* UND /); + + $line =~ s/ \([0-9]+\)$//; + $line =~ s/.* //; + $line =~ s/@.*//; + $funcs{$line} = 1; + } + + return \%funcs; +} + +$ENV{'LANG'} = "C"; + +if ($find_libc_functions) { + pod2usage(1) if (!defined($ARGV[0])); + my $libc_path = find_libc($ARGV[0]); + + my $funcs = find_functions($libc_path, 0); + for my $func (sort(keys(%{$funcs}))) { + if ($func =~ /^__(\S+)_chk$/) { + print " '$1' => 1,\n"; + } + } + exit(0); +} +die "List of libc functions not defined!" if (scalar(keys %libc) < 1); + +my $name; +foreach my $file (@ARGV) { + $rc = 0; + my $elf = 1; + + $report = "$file:"; + @tags = (); + + # Get program headers. + my $PROG_REPORT = output("readelf", "-lW", $file); + if (length($PROG_REPORT) == 0) { + $overall = 1; + next; + } + + # Get ELF headers. + my $DYN_REPORT = output("readelf", "-dW", $file); + + # Get disassembly + my $DISASM + = output("objdump", "-d", "--no-show-raw-insn", "-M", "intel", $file); + + # Get notes + my $NOTES = output("readelf", "-n", $file); + + # Get list of all symbols needing external resolution. + my $functions = find_functions($file, 1); + + # PIE + # First, verify this is an executable, not a library. This seems to be + # best seen by checking for the PHDR program header. + $name = " Position Independent Executable"; + $PROG_REPORT =~ /^Elf file type is (\S+)/m; + my $elftype = $1 || ""; + if ($elftype eq "DYN") { + if ($PROG_REPORT =~ /^ *\bPHDR\b/m) { + + # Executable, DYN ELF type. + good($name, "yes"); + } else { + # Shared library, DYN ELF type. + good($name, "no, regular shared library (ignored)"); + } + } elsif ($elftype eq "EXEC") { + + # Executable, EXEC ELF type. + bad("no-pie", $file, $name, "no, normal executable!", $skip_pie); + } else { + $elf = 0; + + # Is this an ar file with objects? + open(AR, "<$file"); + my $header = <AR>; + close(AR); + if ($header eq "!<arch>\n") { + good($name, "no, object archive (ignored)"); + } else { + # ELF type is neither DYN nor EXEC. + bad("unknown-elf", $file, $name, + "not a known ELF type!? ($elftype)", 0); + } + } + + # Stack-protected + $name = " Stack protected"; + if (defined($functions->{'__stack_chk_fail'}) + || (!$elf && defined($functions->{'__stack_chk_fail_local'}))) { + good($name, "yes"); + } else { + if (%{$functions} eq 0) { + unknown($name, "unknown, no symbols found"); + } else { + bad("no-stackprotector", $file, $name, "no, not found!", + $skip_stackprotector); + } + } + + # Fortified Source + $name = " Fortify Source functions"; + my @unprotected; + my @protected; + for my $name (keys(%libc)) { + if (defined($functions->{$name})) { + push(@unprotected, $name); + } + if (defined($functions->{"__${name}_chk"})) { + push(@protected, $name); + } + } + if ($#protected > -1) { + if ($#unprotected == -1) { + + # Certain. + good($name, "yes"); + } else { + # Vague, due to possible compile-time optimization, + # multiple linkages, etc. Assume "yes" for now. + good($name, "yes", " (some protected functions found)"); + } + } else { + if ($#unprotected == -1) { + unknown($name, "unknown, no protectable libc functions used"); + } else { + # Vague, since it's possible to have the compile-time + # optimizations do away with them, or be unverifiable + # at runtime. Assume "no" for now. + bad("no-fortify-functions", $file, $name, + "no, only unprotected functions found!", + $skip_fortify); + } + } + if ($verbose) { + for my $name (@unprotected) { + good_msg("\tunprotected: $name"); + } + for my $name (@protected) { + good_msg("\tprotected: $name"); + } + } + + # Format + # Unfortunately, I haven't thought of a way to test for this after + # compilation. What it really needs is a lintian-like check that + # reviews the build logs and looks for the warnings, or that the + # argument is changed to use -Werror=format-security to stop the build. + + # RELRO + $name = " Read-only relocations"; + if ($PROG_REPORT =~ /^ *\bGNU_RELRO\b/m) { + good($name, "yes"); + } else { + if ($elf) { + bad("no-relro", $file, $name, "no, not found!", $skip_relro); + } else { + good($name, "no", ", non-ELF (ignored)"); + } + } + + # BIND_NOW + # This marking keeps changing: + # 0x0000000000000018 (BIND_NOW) + # 0x000000006ffffffb (FLAGS) Flags: BIND_NOW + # 0x000000006ffffffb (FLAGS_1) Flags: NOW + + $name = " Immediate binding"; + if ( $DYN_REPORT =~ /^\s*\S+\s+\(BIND_NOW\)/m + || $DYN_REPORT =~ /^\s*\S+\s+\(FLAGS\).*\bBIND_NOW\b/m + || $DYN_REPORT =~ /^\s*\S+\s+\(FLAGS_1\).*\bNOW\b/m) { + good($name, "yes"); + } else { + if ($elf) { + bad("no-bindnow", $file, $name, "no, not found!", $skip_bindnow); + } else { + good($name, "no", ", non-ELF (ignored)"); + } + } + + # For stack clash we need to look for a specific sequence of + # instructions in the objdump disassembly + $name = " Stack clash protection"; + my $index = 0; + my $cmp_addr = 0; + my @patterns = ( + qr/^\s+([0-9a-f]+):\s+cmp\s+(rsp.*|.*0x1000)/, + qr/^\s+[0-9a-f]+:\s+j[eb]\s+([x0-9a-f]+)/, + qr/^\s+[0-9a-f]+:\s+sub\s+(.*,0x1000)/, + qr/^\s+[0-9a-f]+:\s+or\s+(.*,0x0)/, + qr/^\s+([0-9a-f]+):\s+(jmp\s+([x0-9a-f]+)|cmp\s+rsp,.*)/, + qr/^\s+([0-9a-f]+):\s+jne\s+([x0-9a-f]+)/ + ); + my $found = 0; + foreach my $line (split /\n/, $DISASM) { + + # look for each regex from patterns in succession - they all + # should be consecutive in the binary so we always fall back to + # index 0 if we fail to find the next one + if (my @matches = ($line =~ $patterns[$index])) { + if ($index == 0) { + $cmp_addr = hex($matches[0]); + } elsif ($index == 4) { + + # this could be either the jmp or cmp - if is jump then + # this is the last instruction in the sequence otherwise + # cmp has a jne following for index 5 + if ($matches[1] =~ /^jmp.*/) { + my $arg = hex($matches[2]); + if ($arg == $cmp_addr) { + good($name, "yes"); + $found = 1; + last; + } else { + # since the expected instructions should be + # contiguous, always fall back to zero on failure + $index = 0; + next; + } + } + + # nothing to do for the cmp case + } elsif ($index == 5) { + my $arg = hex($matches[1]); + if ($arg == $cmp_addr + 5) { + good($name, "yes"); + $found = 1; + last; + } else { + # since the expected instructions should be + # contiguous, always fall back to zero on failure + $index = 0; + next; + } + } + ++$index; + } else { + $index = 0; + } + } + if (!$found) { + unknown($name, + "unknown, no -fstack-clash-protection instructions found"); + } + + # For cf-protection look for x86 feature: IBT, SHSTK + $name = " Control flow integrity"; + if ($NOTES =~ /^\s+Properties: x86 feature: IBT, SHSTK/m) { + good($name, "yes"); + } else { + bad("no-cfprotection", $file, $name, "no, not found!", + $skip_cfprotection); + } + + if (!$lintian && (!$quiet || $rc != 0)) { + print $report, "\n"; + } + + if ($report_functions) { + for my $name (keys(%{$functions})) { + print $name, "\n"; + } + } + + if (!$lintian && $rc) { + $overall = $rc; + } + + if ($lintian) { + for my $tag (@tags) { + print $tag, "\n"; + } + } +} + +exit($overall); + +__END__ + +=head1 NAME + +hardening-check - check binaries for security hardening features + +=head1 SYNOPSIS + +hardening-check [options] [ELF ...] + +Examine a given set of ELF binaries and check for several security hardening +features, failing if they are not all found. + +=head1 DESCRIPTION + +This utility checks a given list of ELF binaries for several security +hardening features that can be compiled into an executable. These +features are: + +=over 8 + +=item B<Position Independent Executable> + +This indicates that the executable was built in such a way (PIE) that +the "text" section of the program can be relocated in memory. To take +full advantage of this feature, the executing kernel must support text +Address Space Layout Randomization (ASLR). + +=item B<Stack Protected> + +This indicates that there is evidence that the ELF was compiled with the +L<gcc(1)> option B<-fstack-protector> (e.g. uses B<__stack_chk_fail>). The +program will be resistant to having its stack overflowed. + +When an executable was built without any character arrays being allocated +on the stack, this check will lead to false alarms (since there is no +use of B<__stack_chk_fail>), even though it was compiled with the correct +options. + +=item B<Fortify Source functions> + +This indicates that the executable was compiled with +B<-D_FORTIFY_SOURCE=2> and B<-O1> or higher. This causes certain unsafe +glibc functions with their safer counterparts (e.g. B<strncpy> instead +of B<strcpy>), or replaces calls that are verifiable at runtime with the +runtime-check version (e.g. B<__memcpy_chk> insteade of B<memcpy>). + +When an executable was built such that the fortified versions of the glibc +functions are not useful (e.g. use is verified as safe at compile time, or +use cannot be verified at runtime), this check will lead to false alarms. +In an effort to mitigate this, the check will pass if any fortified function +is found, and will fail if only unfortified functions are found. Uncheckable +conditions also pass (e.g. no functions that could be fortified are found, or +not linked against glibc). + +=item B<Read-only relocations> + +This indicates that the executable was build with B<-Wl,-z,relro> to +have ELF markings (RELRO) that ask the runtime linker to mark any +regions of the relocation table as "read-only" if they were resolved +before execution begins. This reduces the possible areas of memory in +a program that can be used by an attacker that performs a successful +memory corruption exploit. + +=item B<Immediate binding> + +This indicates that the executable was built with B<-Wl,-z,now> to have +ELF markings (BIND_NOW) that ask the runtime linker to resolve all +relocations before starting program execution. When combined with RELRO +above, this further reduces the regions of memory available to memory +corruption attacks. + +=back + +=head1 OPTIONS + +=over 8 + +=item B<--nopie>, B<-p> + +Do not require that the checked binaries be built as PIE. + +=item B<--nostackprotector>, B<-s> + +Do not require that the checked binaries be built with the stack protector. + +=item B<--nofortify>, B<-f> + +Do not require that the checked binaries be built with Fortify Source. + +=item B<--norelro>, B<-r> + +Do not require that the checked binaries be built with RELRO. + +=item B<--nobindnow>, B<-b> + +Do not require that the checked binaries be built with BIND_NOW. + +=item B<--nocfprotection>, B<-b> + +Do not require that the checked binaries be built with control flow protection. + +=item B<--quiet>, B<-q> + +Only report failures. + +=item B<--verbose>, B<-v> + +Report verbosely on failures. + +=item B<--report-functions>, B<-R> + +After the report, display all external functions needed by the ELF. + +=item B<--find-libc-functions>, B<-F> + +Instead of the regular report, locate the libc for the first ELF on the +command line and report all the known "fortified" functions exported by +libc. + +=item B<--color>, B<-c> + +Enable colorized status output. + +=item B<--lintian>, B<-l> + +Switch reporting to lintian-check-parsable output. + +=item B<--debug> + +Report some debugging during processing. + +=item B<--help>, B<-h>, B<-?> + +Print a brief help message and exit. + +=item B<--man>, B<-H> + +Print the manual page and exit. + +=back + +=head1 RETURN VALUE + +When all checked binaries have all checkable hardening features detected, +this program will finish with an exit code of 0. If any check fails, the +exit code with be 1. Individual checks can be disabled via command line +options. + +=head1 AUTHOR + +Kees Cook <kees@debian.org> + +=head1 COPYRIGHT AND LICENSE + +Copyright 2009-2013 Kees Cook <kees@debian.org>. + +This program is free software; you can redistribute it and/or modify it +under the terms of the GNU General Public License as published by the +Free Software Foundation; version 2 or later. + +=head1 SEE ALSO + +L<gcc(1)>, L<hardening-wrapper(1)> + +=cut |