#!/usr/bin/perl

# Build log hardening check, checks build logs for missing hardening flags.

# Copyright (C) 2012  Simon Ruderich
#
# 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, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.


use strict;
use warnings;

use Getopt::Long ();
use Term::ANSIColor ();

our $VERSION = '0.01';


# FUNCTIONS

sub error_flags {
    my ($message, $missing_flags_ref, $flag_renames_ref, $line) = @_;

    # Rename flags if requested.
    my @missing_flags = map {
        (exists $flag_renames_ref->{$_})
            ? $flag_renames_ref->{$_}
            : $_
    } @{$missing_flags_ref};

    my $flags = join ' ', @missing_flags;
    printf "%s (%s)%s %s",
           error_color($message, 'red'), $flags, error_color(':', 'yellow'),
           $line;
}
sub error_color {
    my ($message, $color) = @_;

    # Use colors when writing to a terminal.
    if (-t STDOUT) {
        return Term::ANSIColor::colored($message, $color);
    } else {
        return $message;
    }
}

sub any_flags_used {
    my ($line, @flags) = @_;

    foreach my $flag (@flags) {
        return 1 if $line =~ /\s$flag(\s|\\|$)/;
    }

    return 0;
}
sub all_flags_used {
    my ($line, $missing_flags_ref, @flags) = @_;

    my @missing_flags = ();
    foreach my $flag (@flags) {
        if ($line !~ /\s$flag(\s|\\|$)/) {
            push @missing_flags, $flag;
        }
    }

    if (scalar @missing_flags == 0) {
        return 1;
    }

    @{$missing_flags_ref} = @missing_flags;
    return 0;
}

# Modifies $missing_flags_ref array.
sub pic_pie_conflict {
    my ($line, $pie, $missing_flags_ref, @flags_pie) = @_;

    return 0 if not $pie;
    return 0 if not any_flags_used($line, ('-fPIC'));

    my %flags = map { $_ => 1 } @flags_pie;

    # Remove all PIE flags from @missing_flags as they are not required with
    # -fPIC.
    my @result = grep {
        not exists $flags{$_}
    } @{$missing_flags_ref};
    @{$missing_flags_ref} = @result;

    # We got a conflict when no flags are left, thus only PIE flags were
    # missing. If other flags were missing abort because the conflict is not
    # the problem.
    return scalar @result == 0;
}


# CONSTANTS/VARIABLES

# Regex to catch (GCC) compiler warnings.
my $warning_regex = qr/^(.+?):([0-9]+):[0-9]+: warning: (.+?) \[(.+?)\]$/;

# Expected hardening flags. All flags are used as regexps.
my @cflags = (
    '-g',
    '-O2',
    '-fstack-protector',
    '--param=ssp-buffer-size=4',
    '-Wformat',
    '-Wformat-security',
    '-Werror=format-security',
);
my @cflags_pie = (
    '-fPIE',
);
my @cppflags = (
    '-D_FORTIFY_SOURCE=2',
);
my @ldflags = (
    '-Wl,(-z,)?relro',
);
my @ldflags_pie = (
    '-fPIE',
    '-pie',
);
my @ldflags_bindnow = (
    '-Wl,(-z,)?now',
);
# All (hardening) flags.
my @flags = (@cflags, @cflags_pie,
             @cppflags,
             @ldflags, @ldflags_pie, @ldflags_bindnow);
# Renaming rules for the output so the regex parts are not visible.
my %flag_renames = (
    '-Wl,(-z,)?relro' => '-Wl,-z,relro',
    '-Wl,(-z,)?now'   => '-Wl,-z,now',
);


# MAIN

# Additional hardening options.
my $pie     = 0;
my $bindnow = 0;

# Parse command line arguments.
my $option_all     = 0;
my $option_help    = 0;
my $option_version = 0;
if (not Getopt::Long::GetOptions(
            'help|h|?' => \$option_help,
            'version'  => \$option_version,
            'pie'      => \$pie,
            'bindnow'  => \$bindnow,
            'all'      => \$option_all,
        )) {
    require Pod::Usage;
    Pod::Usage::pod2usage(2);
}
if ($option_help) {
    require Pod::Usage;
    Pod::Usage::pod2usage(1);
}
if ($option_version) {
    print "blhc $VERSION  Copyright (C) 2012  Simon Ruderich

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, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
";
    exit 0;
}

if ($option_all) {
    $pie     = 1;
    $bindnow = 1;
}

# Final exit code.
my $exit = 0;

# Input lines, contain only the lines with compiler commands.
my @input = ();

my $continuation = 0;
while (my $line = <>) {
    # Ignore compiler warnings for now.
    next if $line =~ /$warning_regex/;

    # One line may contain multiple commands (";"). Treat each one as single
    # line.
    my @line = split /(?<!\\);/, $line;
    foreach $line (@line) {
        # Add newline, drop all other whitespace at the end of a line.
        $line =~ s/\s+$//;
        $line .= "\n";

        if ($continuation) {
            $continuation = 0;

            # Join lines, but leave the "\" in place so it's clear where the
            # original line break was.
            chomp $input[-1];
            $input[-1] .= ' ' . $line;

        } else {
            # Ignore lines with no compiler commands.
            next if $line !~ /\b(cc|gcc|g\+\+|c\+\+)(\s|\\)/;

            # Ignore false positives.
            #
            # `./configure` output.
            if ($line =~ /^checking /) {
                next;
            }

            push @input, $line;
        }

        # Line continuation, line ends with "\".
        if ($line =~ /\\\s*$/) {
            $continuation = 1;
        }
    }
}

if (scalar @input == 0) {
    print "No compiler commands!\n";
    $exit |= 1;
    exit $exit;
}

# Check if additional hardening options were used. Used to ensure they are
# used for the complete build.
foreach my $line (@input) {
    $pie     = 1 if any_flags_used($line, @cflags_pie, @ldflags_pie);
    $bindnow = 1 if any_flags_used($line, @ldflags_bindnow);
}

if ($pie) {
    @cflags  = (@cflags,  @cflags_pie);
    @ldflags = (@ldflags, @ldflags_pie);
}
if ($bindnow) {
    @ldflags = (@ldflags, @ldflags_bindnow);
}

foreach my $line (@input) {
    # Ignore false positives.
    #
    # ./configure summary.
    next if $line =~ /^Compiler:\s+(cc|gcc|g\+\+|c\+\+)$/;

    # Is this a compiler or linker command?
    my $compiler = 1;
    my $linker   = 0;

    # Linker commands.
    if ($line =~ m{\s-o                  # -o
                   [\s\\]*\s+            # possible line continuation
                   ([A-Za-z0-9_/.-]+/)?  # path to file
                   [A-Za-z0-9_-]+        # binary name (no dots!)
                   (\.so([0-9.])*|\.la)? # library (including version)
                   (\s|\\|\$)            # end of file name
                  }x
            or $line =~ /^libtool: link: /
            or $line =~ m{\s*/bin/bash .+?libtool\s+(.+?\s+)?--mode=(re)?link}) {
        $compiler = 0;
        $linker   = 1;
    }

    # If there are source files then it's compiling/linking in one step and we
    # must check both.
    if ($line =~ /\.(c|cc|cpp)\b/) {
        $compiler = 1;
    }

    # Check hardening flags.
    my @missing;
    if ($compiler and not all_flags_used($line, \@missing, @cflags)
            # Libraries linked with -fPIC don't have to (and can't) be linked
            # with -fPIE as well. It's no error if only PIE flags are missing.
            and not pic_pie_conflict($line, $pie, \@missing, @cflags_pie)) {
        error_flags('CFLAGS missing', \@missing, \%flag_renames, $line);
        $exit |= 1 << 2;
    }
    if ($compiler and not all_flags_used($line, \@missing, @cppflags)) {
        error_flags('CPPFLAGS missing', \@missing, \%flag_renames, $line);
        $exit |= 1 << 2;
    }
    if ($linker and not all_flags_used($line, \@missing, @ldflags)
            # Same here, -fPIC conflicts with -fPIE.
            and not pic_pie_conflict($line, $pie, \@missing, @ldflags_pie)) {
        error_flags('LDFLAGS missing', \@missing, \%flag_renames, $line);
        $exit |= 1 << 2;
    }
}

exit $exit;


__END__

=head1 NAME

blhc - build log hardening check, checks build logs for missing hardening flags

=head1 SYNOPSIS

B<blhc> [-h -? --help]

B<blhc> [--pie] [--bindnow] [--all]

    --help                  available options
    --version               version number and license
    --pie                   force +pie check
    --bindnow               force +bindbow check
    --all                   force +all (+pie, +bindnow) check

=head1 DESCRIPTION

blhc is a small tool which checks build logs for missing hardening flags and
other important warnings. It's licensed under the GPL 3 or later.

=head1 OPTIONS

=over 8

=item B<-h -? --help>

Print available options.

=item B<--version>

Print version number and license.

=item B<--pie>

Force check for all +pie hardening flags. By default it's auto detected.

=item B<--bindnow>

Force check for all +bindnow hardening flags. By default it's auto detected.

=item B<--all>

Force check for all +all (+pie, +bindnow) hardening flags. By default it's
auto detected.

=back

Auto detection only works if at least one command uses the required hardening
flag (e.g. -fPIE). Then it's required for all other commands as well.

=head1 EXIT STATUS

The exit status is a "bit mask", each listed status is ORed when the error
condition occurs to get the result.

=over 8

=item B<0>

Success.

=item B<1>

No compiler commands were found.

=item B<2>

Invalid arguments/options given to blhc.

=item B<4>

Missing hardening flags.

=back

=head1 AUTHOR

Simon Ruderich, E<lt>simon@ruderich.orgE<gt>

=head1 COPYRIGHT AND LICENSE

Copyright (C) 2012 by Simon Ruderich

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, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

=cut