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#!/usr/bin/env perl
# Copyright (c) The Exim Maintainers 2022
# SPDX-License-Identifier: GPL-2.0-or-later
use warnings;
use strict;
BEGIN { pop @INC if $INC[-1] eq '.' };
use Fcntl qw(:DEFAULT :flock :seek);
use File::Find;
use File::Spec;
use constant MIN_AGE => 60; # seconds
my $exim = exists $ENV{'EXIM_BINARY'} ? $ENV{'EXIM_BINARY'} : 'exim';
my %known_okay = map {$_=>1} qw( linux darwin freebsd );
unless (exists $known_okay{$^O}) {
warn "for ease, this perl uses flock, not fcntl, assuming they're the same\n";
warn "this is not known by this author to be the case on $^O\n";
warn "please investigate and either add to allowed-list in script, or rewrite\n";
die "bailing out";
# Another approach to rewriting script: stop all exim receivers and
# queue-runners, prevent them from starting, then add your OS to the list and
# run, even though the locking type is wrong, relying upon not actually
# contending.
}
my $spool_dir = `$exim -n -bP spool_directory`;
chomp $spool_dir;
chdir(File::Spec->catfile($spool_dir, 'input'))
or die "chdir($spool_dir/input) failed: $!\n";
my $exim_msgid_r = qr/(?:[0-9A-Za-z]{6}-[0-9A-Za-z]{6}-[0-9A-Za-z]{2})/;
my $spool_dfile_r = qr/^(($exim_msgid_r)-D)\z/o;
sub fh_ends_newline {
my ($fh, $dfn, $verbose) = @_;
seek($fh, -1, 2) or do { warn "seek(file($dfn)) failed: $!\n"; return -1 };
my $count = read $fh, my $ch, 1;
if ($count == -1) { warn "failed to read last byte of $dfn\n"; return -1 };
if ($count == 0) { warn "file shrunk by one?? problem with $dfn\n"; return -1 };
if ($ch eq "\n") { print "okay!\n" if $verbose; return 1 }
print "PROBLEM: $dfn missing final newline (got $ch)\n" if $verbose;
return 0;
}
sub each_found_file {
return unless $_ =~ $spool_dfile_r;
my ($msgid, $dfn) = ($2, $1);
# We should have already upgraded Exim before invoking us, thus any spool
# files will be old and we can reduce spending time trying to lock files
# still being written to, etc.
my @st = lstat($dfn) or return;
if ($^T - $st[9] < MIN_AGE) { return };
-f "./${msgid}-H" || return;
print "consider: $dfn\n";
open(my $fh, '+<:raw', $dfn) or do {
warn "open($dfn) failed: $!\n";
return;
};
# return with a lexical FH in modern Perl should guarantee close, AIUI
# we do our first check without a lock, so that we can scan past messages
# being handled by Exim quickly, and only lock up on those which Exim is
# trying and failing to deliver. However, since Exim will be hung on remote
# hosts, this is likely. Thus best to kill queue-runners first.
return if fh_ends_newline($fh, $dfn, 0); # also returns on error
print "Problem? $msgid probably missing newline, locking to be sure ...\n";
flock($fh, LOCK_EX) or do { warn "flock(file($dfn)) failed: $!\n"; return };
return if fh_ends_newline($fh, $dfn, 1); # also returns on error
fixup_message($msgid, $dfn, $fh);
close($fh) or warn "close($dfn) failed: $!\n";
};
sub fixup_message {
my ($msgid, $dfn, $fh) = @_;
# we can't freeze the message, our lock stops that, which is good!
seek($fh, 0, 2) or do { warn "seek(file($dfn)) failed: $!\n"; return -1 };
my $r = inc_message_header_linecount($msgid);
if ($r < 0) {
warn "failed to fix message headers in ${msgid}-H so not editing message\n";
return;
}
print {$fh} "\n";
print "${msgid}: added newline\n";
};
sub inc_message_header_linecount {
my ($msgid) = @_;
my $name_in = "${msgid}-H";
my $name_out = "${msgid}-chunkfix";
open(my $in, '<:perlio', $name_in) or do { warn "open(${name_in}) failed: $!\n"; return -1 };
open(my $out, '>:perlio', $name_out) or do { warn "write-open(${name_out}) failed: $!\n"; return -1 };
my $seen = 0;
my $lc;
foreach (<$in>) {
if ($seen) {
print {$out} $_;
next;
}
if (/^(-body_linecount\s+)(\d+)(\s*)$/) {
$lc = $2 + 1;
print {$out} "${1}${lc}${3}";
$seen = 1;
next;
}
print {$out} $_;
}
close($in) or do {
warn "read-close(${msgid}-H) failed, assuming incomplete: $!\n";
close($out);
unlink $name_out;
return -1;
};
close($out) or do {
warn "write-close(${msgid}-chunkfix) failed, aborting: $!\n";
unlink $name_out;
return -1;
};
my @target = stat($name_in) or do { warn "stat($name_in) failed: $!\n"; unlink $name_out; return -1 };
my @created = stat($name_out) or do { warn "stat($name_out) failed: $!\n"; unlink $name_out; return -1 };
# 4=uid, 5=gid, 2=mode
if (($created[5] != $target[5]) or ($created[4] != $target[4])) {
chown $target[4], $target[5], $name_out or do {
warn "chown($name_out) failed: $!\n";
unlink $name_out;
return -1;
};
}
if (($created[2]&07777) != ($target[2]&0x7777)) {
chmod $target[2]&0x7777, $name_out or do {
warn "chmod($name_out) failed: $!\n";
unlink $name_out;
return -1;
};
}
rename $name_out, $name_in or do {
warn "rename '${msgid}-chunkfix' -> '${msgid}-H' failed: $!\n";
unlink $name_out;
return -1;
};
print "${msgid}: linecount set to $lc\n";
return 1;
}
find({wanted => \&each_found_file}, '.');
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