#!/usr/bin/perl -w
# dgit repos policy hook script for Debian
#
# Copyright (C) 2015-2016  Ian Jackson
#
#    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 Debian::Dgit::Infra; # must precede Debian::Dgit; - can change @INC!
use Debian::Dgit qw(:DEFAULT :policyflags);
setup_sigwarn();

use POSIX;
use JSON;
use File::Temp qw(tempfile);
use DBI;
use IPC::Open2;
use Data::Dumper;

use Debian::Dgit::Policy::Debian;

initdebug('%');
enabledebuglevel $ENV{'DGIT_DRS_DEBUG'};

END { $? = 127; } # deliberate exit uses _exit

our $distro = shift @ARGV // die "need DISTRO";
our $repos = shift @ARGV // die "need DGIT-REPOS-DIR";
our $dgitlive = shift @ARGV // die "need DGIT-LIVE-DIR";
our $distrodir = shift @ARGV // die "need DISTRO-DIR";
our $action = shift @ARGV // die "need ACTION";

our $publicmode = 02775;
our $new_upload_propagation_slop = 3600*4 + 100;# fixme config;

our $poldbh;
our $pkg;
our $pkgdir;
our ($pkg_exists,$pkg_secret);

our $stderr;

our ($version,$suite,$tagname);
our %deliberately;

# We assume that it is not possible for NEW to have a version older
# than sid.

# Whenever pushing, we check for
#   source-package-local tainted history
#   global tainted history
#   can be overridden by --deliberately except for an admin prohib taint
# 
# ALL of the following apply only if history is secret:
# 
# if NEW has no version, or a version which is not in our history[1]
#   (always)
#   check all suites
#   if any suite's version is in our history[1], publish our history
#   otherwise discard our history,
#     tainting --deliberately-include-questionable-history
# 
# if NEW has a version which is in our history[1]
#   (on push only)
#   require explicit specification of one of
#     --deliberately-include-questionable-history
#     --deliberately-not-fast-forward
#       (latter will taint old NEW version --d-i-q-h)
#   (otherwise)
#   leave it be
# 
# [1] looking for the relevant git tag for the version number and not
#    caring what that tag refers to.
#
#    When we are doing a push to a fresh repo, any version will do: in
#    this case, this is the first dgit upload of an existing package,
#    and we trust that the uploader hasn't included in their git
#    history any previous non-dgit uploads.
#
# A wrinkle: if we approved a push recently, we treat NEW as having
# a version which is in our history.  This is because the package may
# still be being uploaded.  (We record this using the timestamp of the
# package's git repo directory.)

# We aim for the following invariants and properties:
#
# - .dsc of published dgit package will have corresponding publicly
#   visible dgit-repo (soon)
#
# - when a new package is rejected we help maintainer avoid
#   accidentally including bad objects in published dgit history
#
# - .dsc of NEW dgit package has corresponding dgit-repo but not
#   publicly readable

sub apiquery ($) {
    my ($subpath) = @_;
    local $/=undef;
    my $dgit = "$dgitlive/dgit";
    $dgit = "dgit" if !stat_exists $dgit;
    my $cmd = "$dgit -d$distro \$DGIT_TEST_OPTS";
    $cmd .= " -".("D" x $debuglevel) if $debuglevel;
    $cmd .= " archive-api-query $subpath";
    printdebug "apiquery $cmd\n";
    $!=0; $?=0; my $json = `$cmd`;
    defined $json && !$? or die "$subpath $! $?";
    my $r = decode_json $json;
    my $d = new Data::Dumper([$r], [qw(r)]);
    printdebug "apiquery $subpath | ", $d->Dump() if $debuglevel>=2;
    return $r;
}

sub vsn_in_our_history ($) {
    my ($vsn) = @_;

    # Eventually, when we withdraw support for old-format (DEP-14
    # namespace) tags, we will need to change this to only look
    # for debiantag_new.  See the commit
    #   "Tag change: Update dgit-repos-policy-debian"
    # (reverting which is a good start for that change).

    my @tagrefs = map { "refs/tags/".$_ } debiantags $vsn, $distro;
    printdebug " checking history  vsn=$vsn tagrefs=@tagrefs\n";
    open F, "-|", qw(git for-each-ref), @tagrefs;
    $_ = <F>;
    close F;
    return 1 if defined && m/\S/;
    die "$pkg tagrefs @tagrefs $? $!" if $?;
    return 0;
}

sub specific_suite_has_suitable_vsn ($$) {
    my ($suite, $vsn_check) = @_; # tests $vsn_check->($version)
    my $in_suite = apiquery "dsc_in_suite/$suite/$pkg";
    foreach my $entry (@$in_suite) {
	my $vsn = $entry->{version};
	die "$pkg ?" unless defined $vsn;
	printdebug " checking history found suite=$suite vsn=$vsn\n";
	return 1 if $vsn_check->($vsn);
    }
    return 0;
}

sub new_has_vsn_in_our_history () {
    return specific_suite_has_suitable_vsn('new', \&vsn_in_our_history);
}

sub good_suite_has_suitable_vsn ($) {
    my ($vsn_check) = @_; # as for specific_suite_has_specific_vsn
    my $suites = apiquery "suites";
    foreach my $suitei (@$suites) {
	my $suite = $suitei->{name};
	die unless defined $suite;
	next if $suite =~ m/\bnew$/;
	return 1 if specific_suite_has_suitable_vsn($suite, $vsn_check);
    }
    return 0;
}

sub statpackage () {
    $pkgdir = "$repos/$pkg.git";
    if (!stat_exists $pkgdir) {
	printdebug "statpackage $pkg => ENOENT\n";
	$pkg_exists = 0;
    } else {
	$pkg_exists = 1;
	$pkg_secret = !!(~(stat _)[2] & 05);
	printdebug "statpackage $pkg => exists, secret=$pkg_secret.\n";
    }
}

sub getpackage () {
    die unless @ARGV >= 1;
    $pkg = shift @ARGV;
    die unless $pkg =~ m/^$package_re$/;

    statpackage();
}

sub add_taint ($$) {
    my ($refobj, $reason) = @_;

    printdebug "TAINTING $refobj\n",
        (map { "\%| $_" } split "\n", $reason),
        "\n";

    my $tf = new File::Temp or die $!;
    print $tf "$refobj^0\n" or die $!;
    flush $tf or die $!;
    seek $tf,0,0 or die $!;

    my $gcfpid = open GCF, "-|";
    defined $gcfpid or die $!;
    if (!$gcfpid) {
	open STDIN, "<&", $tf or die $!;
	exec 'git', 'cat-file', '--batch';
	die $!;
    }

    close $tf or die $!;
    $_ = <GCF>;
    defined $_ or die;
    m/^(\w+) (\w+) (\d+)\n/ or die "$_ ?";
    my $gitobjid = $1;
    my $gitobjtype = $2;
    my $bytes = $3;

    my $gitobjdata;
    if ($gitobjtype eq 'commit' or $gitobjtype eq 'tag') {
	$!=0; read GCF, $gitobjdata, $bytes == $bytes
	    or die "$gitobjid $bytes $!";
    }
    close GCF;

    $poldbh->do("INSERT INTO taints".
		" (package, gitobjid, gitobjtype, gitobjdata, time, comment)".
		" VALUES (?,?,?,?,?,?)", {},
		$pkg, $gitobjid, $gitobjtype, $gitobjdata, time, $reason);

    my $taint_id = $poldbh->last_insert_id(undef,undef,"taints","taint_id");
    die unless defined $taint_id;

    $poldbh->do("INSERT INTO taintoverrides".
		" (taint_id, deliberately)".
		" VALUES (?, '--deliberately-include-questionable-history')", 
		{}, $taint_id);
}

sub add_taint_by_tag ($$) {
    my ($tagname,$refobjid) = @_;
    add_taint($refobjid,
	      "tag $tagname referred to this object in git tree but all".
	      " previously pushed versions were found to have been".
	      " removed from NEW (ie, rejected) (or never arrived)");
}

sub check_package () {
    return 0 unless $pkg_exists;
    return 0 unless $pkg_secret;

    printdebug "check_package\n";

    chdir $pkgdir or die "$pkgdir $!";

    stat '.' or die "$pkgdir $!";
    my $mtime = ((stat _)[9]);
    my $age = time -  $mtime;
    printdebug "check_package age=$age\n";

    if (good_suite_has_suitable_vsn(\&vsn_in_our_history)) {
	chmod $publicmode, "." or die $!;
	$pkg_secret = 0;
	eval {
	    my $mirror_hook = "$distrodir/mirror-hook";
	    if (stat_exists $mirror_hook) {
		my @mirror_cmd =
		    ($mirror_hook, $distrodir, "updated-hook", $pkg);
		debugcmd " (mirror)",@mirror_cmd;
		system @mirror_cmd and failedcmd @mirror_cmd;
	    }
	};
	if (length $@) {
	    chomp $@;
	    print STDERR "policy hook: warning:".
		" failed to mirror publication of \`$pkg':".
		" $@\n";
	}
	return 0;
    }

    return 0 if $age < $new_upload_propagation_slop;

    return 0 if new_has_vsn_in_our_history();

    printdebug "check_package secret, deleted, tainting\n";

    git_for_each_ref('refs/tags', sub {
	my ($objid,$objtype,$fullrefname,$tagname) = @_;
	add_taint_by_tag($tagname,$objid);
    });

    return FRESHREPO;
}

sub action_check_package () {
    getpackage();
    return check_package();
}

sub getpushinfo () {
    die unless @ARGV >= 4;
    $version = shift @ARGV;
    $suite = shift @ARGV;
    $tagname = shift @ARGV;
    my $delibs = shift @ARGV;
    foreach my $delib (split /\,/, $delibs) {
	$deliberately{$delib} = 1;
    }
}

sub deliberately ($) { return $deliberately{"--deliberately-$_[0]"}; }

sub action_push () {
    getpackage();
    getpushinfo();

    check_package(); # might make package public, or might add taints

    return 0 unless $pkg_exists;
    return 0 unless $pkg_secret;

    # we suppose that NEW has a version which is already in our
    # history, as otherwise the repo would have been blown away

    if (deliberately('not-fast-forward')) {
	add_taint(server_ref($suite),
		  "rewound suite $suite; --deliberately-not-fast-forward".
		  " specified in signed tag $tagname for upload of".
		  " version $version");
	return NOFFCHECK|FRESHREPO;
    }
    if (deliberately('include-questionable-history')) {
	return 0;
    }
    die "\nPackage is in NEW and has not been accepted or rejected yet;".
	" use a --deliberately option to specify whether you are".
	" keeping or discarding the previously pushed history. ".
	" Please RTFM dgit(1).\n\n";
}

sub action_push_confirm () {
    getpackage();
    getpushinfo();
    die unless @ARGV >= 1;
    my $freshrepo = shift @ARGV;

    my $initq = $poldbh->prepare(<<END);
        SELECT taint_id, gitobjid FROM taints t
            WHERE (package = ? OR package = '')
END
    $initq->execute($pkg);

    my @objscatcmd = qw(git);
    push @objscatcmd, qw(--git-dir), $freshrepo if length $freshrepo;
    push @objscatcmd, qw(cat-file --batch);
    debugcmd '|',@objscatcmd if $debuglevel>=2;

    my @taintids;
    my $chkinput = tempfile();
    while (my $taint = $initq->fetchrow_hashref()) {
	push @taintids, $taint->{taint_id};
	print $chkinput $taint->{gitobjid}, "\n" or die $!;
	printdebug '|> ', $taint->{gitobjid}, "\n" if $debuglevel>=2;
    }
    flush $chkinput or die $!;
    seek $chkinput,0,0 or die $!;

    my $checkpid = open CHKOUT, "-|" // die $!;
    if (!$checkpid) {
	open STDIN, "<&", $chkinput or die $!;
	delete $ENV{GIT_ALTERNATE_OBJECT_DIRECTORIES};
	# ^ recent versions of git set this in the environment of
	# receive hooks.  This can cause us to see things which
	# the user is trying to abolish.
	exec @objscatcmd or die $!;
    }

    my ($taintinfoq,$overridesanyq,$untaintq,$overridesq);

    my $overridesstmt = <<END;
        SELECT deliberately FROM taintoverrides WHERE (
            1=0
END
    my @overridesv = sort keys %deliberately;
    $overridesstmt .= <<END foreach @overridesv;
            OR deliberately = ?
END
    $overridesstmt .= <<END;
	) AND taint_id = ?
        ORDER BY deliberately ASC
END

    my $mustreject=0;

    while (my $taintid = shift @taintids) {
	$!=0; $_ = <CHKOUT>;
	die "($taintid @objscatcmd) $!" unless defined $_;
	printdebug "|< ", $_ if $debuglevel>=2;

	next if m/^\w+ missing$/;
	die "($taintid @objscatcmd) $_ ?" unless m/^(\w+) (\w+) (\d+)\s/;
	my ($objid,$objtype,$nbytes) = ($1,$2,$3);

	my $drop;
	(read CHKOUT, $drop, $nbytes) == $nbytes
	    or die "($taintid @objscatcmd) $!";

	$!=0; $_ = <CHKOUT>;
	die "($taintid @objscatcmd) $!" unless defined $_;
	die "($taintid @objscatcmd) $_ ?" if m/\S/;

	$taintinfoq ||= $poldbh->prepare(<<END);
            SELECT package, time, comment FROM taints WHERE taint_id =  ?
END
        $taintinfoq->execute($taintid);

	my $ti = $taintinfoq->fetchrow_hashref();
	die "($taintid)" unless $ti;

	my $timeshow = defined $ti->{time}
	    ? " at time ".strftime("%Y-%m-%d %H:%M:%S Z", gmtime $ti->{time})
	    : "";
	my $pkgshow = length $ti->{package}
	    ? "package $ti->{package}"
	    : "any package";

	$stderr .= <<END;

History contains tainted $objtype $objid
Taint recorded$timeshow for $pkgshow
Reason: $ti->{comment}
END

        printdebug "SQL overrides: @overridesv $taintid /\n$overridesstmt\n";

        $overridesq ||= $poldbh->prepare($overridesstmt);
	$overridesq->execute(@overridesv, $taintid);
	my ($ovwhy) = $overridesq->fetchrow_array();
	if (!defined $ovwhy) {
	    $overridesanyq ||= $poldbh->prepare(<<END);
	        SELECT 1 FROM taintoverrides WHERE taint_id = ? LIMIT 1
END
	    $overridesanyq->execute($taintid);
	    my ($ovany) = $overridesanyq->fetchrow_array();
	    $stderr .= $ovany ? <<END : <<END;
Could be forced using --deliberately.  Consult documentation.
END
Uncorrectable error.  If confused, consult administrator.
END
            $mustreject = 1;
	} else {
	    $stderr .= <<END;
Forcing due to --deliberately-$ovwhy
END
            $untaintq ||= $poldbh->prepare(<<END);
                DELETE FROM taints WHERE taint_id = ?
END
            $untaintq->execute($taintid);
        }
    }
    close CHKOUT;

    if ($mustreject) {
	$stderr .= <<END;

Rejecting push due to questionable history.
END
        return 1;
    }

    if (length $freshrepo) {
	if (!good_suite_has_suitable_vsn(sub { 1; })) {
	    stat $freshrepo or die "$freshrepo $!";
	    my $oldmode = ((stat _)[2]);
	    my $oldwrites = $oldmode & 0222;
	    # remove r and x bits which have corresponding w bits clear
	    my $newmode = $oldmode &
		(~0555 | ($oldwrites << 1) | ($oldwrites >> 1));
	    printdebug sprintf "chmod %#o (was %#o) %s\n",
	        $newmode, $oldmode, $freshrepo;
	    chmod $newmode, $freshrepo or die $!;
	    utime undef, undef, $freshrepo or die $!;
	}
    }

    return 0;
}

sub action_check_list () {
    opendir L, "$repos" or die "$repos $!";
    while (defined (my $dent = readdir L)) {
	next unless $dent =~ m/^($package_re)\.git$/;
	$pkg = $1;
	statpackage();
	next unless $pkg_exists;
	next unless $pkg_secret;
	print "$pkg\n" or die $!;
    }
    closedir L or die $!;
    close STDOUT or die $!;
    return 0;
}

$action =~ y/-/_/;
my $fn = ${*::}{"action_$action"};
if (!$fn) {
    printdebug "dgit-repos-policy-debian: unknown action $action\n";
    exit 0;
}

my $sleepy=0;
my $rcode;

my $db_busy_exception= 'Debian::Dgit::Policy::Debian::DB_BUSY';

my @orgargv = @ARGV;

for (;;) {
    @ARGV = @orgargv;
    eval {
	poldb_setup(poldb_path($repos), sub {
	    $poldbh->{HandleError} = sub {
		return 0 unless $poldbh->err == 5; # SQLITE_BUSY, not in .pm :-(
		die bless { }, $db_busy_exception;
	    };

	    eval ($ENV{'DGIT_RPD_TEST_DBLOOP_HOOK'}//'');
	    die $@ if length $@;
	    # used by tests/tests/debpolicy-dbretry
        });

	$stderr = '';

	$rcode = $fn->();
	die unless defined $rcode;

	$poldbh->commit;
    };
    last unless length $@;
    die $@ unless ref $@ eq $db_busy_exception;

    die if $sleepy >= 20;
    $sleepy++;
    print STDERR "[policy database busy, retrying (${sleepy}s)]\n";

    eval { $poldbh->rollback; };
}

print STDERR $stderr or die $!;
flush STDERR or die $!;
_exit $rcode;