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#!/usr/bin/perl -T
#------------------------------------------------------------------------------
# This is amavisd-signer, a DKIM signing service daemon for amavisd.
# It uses an AM.PDP protocol lookalike to receive a request from amavisd
# and provides two services: choosing a signing key, and signing a
# message digest with a chosen DKIM private key.
#
# Author: Mark Martinec <Mark.Martinec@ijs.si>
#
# Copyright (c) 2010-2014, Mark Martinec
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright notice,
# this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
# BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
#
# The views and conclusions contained in the software and documentation are
# those of the authors and should not be interpreted as representing official
# policies, either expressed or implied, of the Jozef Stefan Institute.
# (the above license is the 2-clause BSD license, also known as
# a "Simplified BSD License", and pertains to this program only)
#
# Patches and problem reports are welcome.
# The latest version of this program is available at:
# http://www.ijs.si/software/amavisd/
#------------------------------------------------------------------------------
# Using a separate signing service (which may run under a dedicated UID or
# GID or as root, having exclusive access to private keys) releaves amavisd
# process from needing to have access to private keys. Separating roles can
# provide improved protection for DKIM private keys, and/or can provide more
# flexibility in choosing a signing key.
#
# Usage:
# amavisd-signer &
package AmavisSigner;
use strict;
use re 'taint';
use warnings FATAL => 'utf8';
no warnings 'uninitialized';
use Sys::Syslog; # used by Net::Server for logging
use MIME::Base64;
use Mail::DKIM;
use Mail::DKIM::PrivateKey;
use Net::Server 0.91;
use Net::Server::Multiplex;
use vars qw(@ISA);
@ISA = qw(Net::Server::Multiplex);
use vars qw(
$VERSION $log_level
%dkim_signing_keys_by_domain
@dkim_signing_keys_list @dkim_signing_keys_storage
@dkim_signature_options_bysender_maps
$daemon_chroot_dir $daemon_user $daemon_group $pid_file $daemonize
$inet_socket_bind @listen_sockets $listen_queue_size
$syslog_ident $syslog_facility
);
$VERSION = 1.001; # 20100730
#
# Please adjust the following settings as necessary:
#
$daemon_user = 'amavis';
$daemon_group = 'amavis';
# $daemon_chroot_dir = '/var/amavis'; # chroot directory or undef
# $daemonize = 1;
$log_level = 2; # 0..5
$syslog_facility = 'mail';
$syslog_ident = 'amavisd-signer';
# the $inet_socket_bind and @listen_sockets should correspond to a
# setting $dkim_signing_service in amavisd.conf :
$inet_socket_bind = '127.0.0.1';
@listen_sockets = ( 20203 );
$listen_queue_size = undef; # uses a default
# Load all available private keys and supply their public key RR constraints.
# Arguments are a domain, a selector, a key (a file name of a private key in
# PEM format), followed by optional attributes/constraints (tags, represented
# here as Perl hash key/value pairs) which are allowed by RFC 4871 in a public
# key resource record (v, g, h, k, n, s, t), of which only g, h, k, s and t
# are considered to be constraints limiting the choice of a signing key.
#
# signing domain selector private key options
# ------------- -------- ---------------------- ----------
# dkim_key('example.org', 'abc', '/var/db/dkim/a.key.pem');
# dkim_key('example.org', 'yyy', '/var/db/dkim/b.key.pem', t=>'s');
# dkim_key('example.org', 'zzz', '/var/db/dkim/b.key.pem', h=>'sha256');
# dkim_key('example.com', 'sel-2008', '/var/db/dkim/sel-example-com.key.pem',
# t=>'s:y', g=>'*', k=>'rsa', h=>'sha256:sha1', s=>'email',
# n=>'testing; 1, 2');
# dkim_key('guest.example.com', 'g', '/var/db/dkim/g-guest-ex-com.key.pem');
# dkim_key('mail.example.com', 'notif', '/var/db/dkim/notif-mail.key.pem');
# @dkim_signature_options_bysender_maps maps author/sender addresses or
# domains to signature tags/requirements; possible signature tags according
# to RFC 4871 are: (v), a, (b), (bh), c, d, (h), i, l, q, s, (t), x, z;
# of which the following are determined implicitly: v, b, bh, h, t
# (tag h is controlled by %signed_header_fields); currently ignored tags
# are l and z; instead of an absolute expiration time (tag x) one may use
# a pseudo tag 'ttl' to specify a relative expiration time in seconds, which
# is converted to an absolute expiration time prior to signing: x = t + ttl;
# a built-in default is provided for each tag if no better match is found
#
# @dkim_signature_options_bysender_maps = ( {
# 'postmaster@mail.example.com' => { a => 'rsa-sha1', ttl => 7*24*3600 },
# 'spam-reporter@example.com' => { a => 'rsa-sha1', ttl => 7*24*3600 },
# 'mail.example.com' => { a => 'rsa-sha1', ttl => 10*24*3600 },
# # explicit 'd' forces a third-party signature on foreign (hosted) domains
# 'guest.example' => { d => 'guest.example.com' },
# '.example.com' => { d => 'example.com' },
# # catchall defaults
# '.' => { a => 'rsa-sha256', c => 'relaxed/simple', ttl => 30*24*3600 },
# # 'd' defaults to a domain of an author/sender address,
# # 's' defaults to whatever selector is offered by a matching key
# } );
#
# No further user-configurable settings below (but feel free
# to customize code in choose_key_request() or replace it altogether.
#
sub ll($) {
my($level) = @_;
$level <= $log_level;
}
my($server); # a Net::Server object
sub do_log($$;@) {
my($level, $errmsg, @args) = @_;
$errmsg = sprintf($errmsg,@args) if @args;
if ($level <= $log_level) {
my($prio); # Net::Server logging priority
# 0=err, 1=warning, 2=notice, 3=info, 4=debug
if ($level >= 3) { $prio = 4 }
elsif ($level >= 0) { $prio = 2 }
elsif ($level >= -1) { $prio = 1 }
else { $prio = 0 }
$server->log($prio, sanitize_str($errmsg));
# Net::Server directs STDERR to the log_file
# print STDERR sanitize_str($errmsg)."\n";
}
}
sub sanitize_str {
my($str, $keep_eol) = @_;
my(%map) = ("\r" => '\\r', "\n" => '\\n', "\f" => '\\f', "\t" => '\\t',
"\b" => '\\b', "\e" => '\\e', "\\" => '\\\\');
if ($keep_eol) {
$str =~ s/([^\012\040-\133\135-\176])/ # and \240-\376 ?
exists($map{$1}) ? $map{$1} :
sprintf(ord($1)>255 ? '\\x{%04x}' : '\\%03o', ord($1))/eg;
} else {
$str =~ s/([^\040-\133\135-\176])/ # and \240-\376 ?
exists($map{$1}) ? $map{$1} :
sprintf(ord($1)>255 ? '\\x{%04x}' : '\\%03o', ord($1))/eg;
}
$str;
}
sub split_address($) {
my($mailbox) = @_; local($1,$2);
$mailbox =~ /^ (.*?) ( \@ (?: \[ (?: \\. | [^\]\\] ){0,999} (?: \] | \z)
| [^\[\@] )*
) \z/xs ? ($1, $2) : ($mailbox, '');
}
# THE dkim_key IS A DIRECT COPY OF THE SAME ROUTINE FROM amavisd
#
# Store a private DKIM signing key for a given domain and selector.
# The argument $key can be a Mail::DKIM::PrivateKey object or a file
# name containing a key in a PEM format (e.g. as generated by openssl).
# For compatibility with dkim_milter the signing domain can include a '*'
# as a wildcard - this is not recommended as this way amavisd could produce
# signatures which have no corresponding public key published in DNS.
# The proper way is to have one dkim_key entry for each published DNS RR.
# Optional arguments can provide additional information about the resource
# record (RR) of a public key, i.e. its options according to RFC 4871.
# The subroutine is typically called from a configuration file, once for
# each signing key available.
#
sub dkim_key($$$;@) {
my($domain,$selector,$key) = @_; shift; shift; shift;
@_%2 == 0 or die "dkim_key: a list of key/value pairs expected as options\n";
my(%key_options) = @_; # remaining args are options from a public key RR
defined $domain && $domain ne ''
or die "dkim_key: domain must not be empty: ($domain,$selector,$key)";
defined $selector && $selector ne ''
or die "dkim_key: selector must not be empty: ($domain,$selector,$key)";
my($key_storage_ind);
if (ref $key) { # key already preprocessed and provided as an object
push(@dkim_signing_keys_storage, [$key]);
$key_storage_ind = $#dkim_signing_keys_storage;
} else { # assume a name of a file containing a private key in PEM format
my($fname) = $key;
my($pem_fh) = IO::File->new; # open a file with a private key
$pem_fh->open($fname,'<') or die "Can't open PEM file $fname: $!";
my(@stat_list) = stat($pem_fh); # soft-link friendly
@stat_list or warn "Error on accessing $fname: $!";
my($dev,$inode) = @stat_list;
if ($dev && $inode) {
for my $j (0..$#dkim_signing_keys_storage) { # same file reused?
my($k,$dv,$in,$fn) = @{$dkim_signing_keys_storage[$j]};
if ($dv == $dev && $in == $inode) { $key_storage_ind = $j; last }
}
}
if (!defined($key_storage_ind)) {
# read file and store its contents as a new entry
my($nbytes,$buff); $key = '';
while (($nbytes=$pem_fh->read($buff,16384)) > 0) { $key .= $buff }
defined $nbytes or die "Error reading key from file $fname: $!";
push(@dkim_signing_keys_storage, [$key,$dev,$inode,$fname]);
$key_storage_ind = $#dkim_signing_keys_storage;
}
$pem_fh->close or die "Error closing file $fname: $!";
$key_options{k} = 'rsa' if defined $key_options{k}; # force RSA
}
$domain = lc($domain) if !ref($domain); # possibly a regexp
$selector = lc($selector);
$key_options{domain} = $domain; $key_options{selector} = $selector;
$key_options{key_storage_ind} = $key_storage_ind;
if (@dkim_signing_keys_list > 100) {
# sorry, skip the test to avoid slow O(n^2) searches
} else {
!(grep { $_->{domain} eq $domain && $_->{selector} eq $selector }
@dkim_signing_keys_list)
or die "dkim_key: selector $selector for domain $domain already in use\n";
}
$key_options{key_ind} = $#dkim_signing_keys_list + 1;
push(@dkim_signing_keys_list, \%key_options); # using a list preserves order
}
# THE dkim_key_postprocess IS A DIRECT COPY OF THE SAME ROUTINE FROM amavisd
#
# Convert private keys (as strings in PEM format) into RSA objects
# and do some pre-processing on @dkim_signing_keys_list entries
# (may run unprivileged)
#
sub dkim_key_postprocess() {
# convert private keys (as strings in PEM format) into RSA objects
for my $ks (@dkim_signing_keys_storage) {
my($pkcs1,$dev,$inode,$fname) = @$ks;
if (ref($pkcs1) && UNIVERSAL::isa($pkcs1,'Crypt::OpenSSL::RSA')) {
# it is already a Crypt::OpenSSL::RSA object
} else {
# assume a string is a private key in PEM format, convert it to RSA obj
$ks->[0] = Crypt::OpenSSL::RSA->new_private_key($pkcs1);
}
}
for my $ent (@dkim_signing_keys_list) {
my($domain) = $ent->{domain};
$dkim_signing_keys_by_domain{$domain} = []
if !$dkim_signing_keys_by_domain{$domain};
}
my($any_wild); my($j) = 0;
for my $ent (@dkim_signing_keys_list) {
$ent->{v} = 'DKIM1' if !defined $ent->{v}; # provide a default
if (defined $ent->{n}) { # encode n as qp-section (rfc4871, rfc2047)
$ent->{n} =~ s{([\000-\037\177=;"])}{sprintf('=%02X',ord($1))}egs;
}
my($domain) = $ent->{domain};
if (ref($domain) eq 'Regexp') {
$ent->{domain_re} = $domain;
$any_wild = sprintf("key#%d, %s", $j+1, $domain) if !defined $any_wild;
} elsif ($domain =~ /\*/) {
# wildcarded signing domain in a key declaration, evil, asks for trouble!
# support wildcards in signing domain for compatibility with dkim_milter
my($regexp) = $domain;
$regexp =~ s/\*{2,}/*/gs; # collapse successive wildcards
# '*' is a wildcard, quote the rest
$regexp =~ s{ ([@#/.^$|*+?(){}\[\]\\]) }{$1 eq '*' ? '.*' : '\\'.$1}gex;
$regexp = '^' . $regexp . '\\z'; # implicit anchors
$regexp =~ s/^\^\.\*//s; # remove leading anchor if redundant
$regexp =~ s/\.\*\\z\z//s; # remove trailing anchor if redundant
$regexp = '(?:)' if $regexp eq ''; # just in case, non-empty regexp
# presence of {'domain_re'} entry lets get_dkim_key use this regexp
# instead of a direct string comparision with {'domain'}
$ent->{domain_re} = qr{$regexp}; # compiled regexp object
$any_wild = sprintf("key#%d, %s", $j+1, $domain) if !defined $any_wild;
}
# %dkim_signing_keys_by_domain entries contain lists of indices into
# the @dkim_signing_keys_list of all potentially applicable signing keys.
# This hash (keyed by domain name) avoids linear searching for signing
# keys for all fully-specified domains in @dkim_signing_keys_list.
# Wildcarded entries must still be looked up sequentially at run-time
# to preserve the declared order and the 'first match wins' paradigm.
# Such entries are only supported for compatibility with dkim_milter
# and are evil because amavisd has no quick way of verifying that DNS RR
# really exists, so signatures generated by amavisd can fail when not all
# possible DNS resource records exist for wildcarded signing domains.
#
if (!defined($ent->{domain_re})) { # no regexp, just plain match on domain
push(@{$dkim_signing_keys_by_domain{$domain}}, $j);
} else { # a wildcard in a signing domain, compatibility with dkim_milter
# wildcarded signing domain potentially matches any _by_domain entry
for my $d (keys %dkim_signing_keys_by_domain) {
push(@{$dkim_signing_keys_by_domain{$d}}, $j);
}
# the '*' entry collects only wildcarded signing keys
$dkim_signing_keys_by_domain{'*'} = []
if !$dkim_signing_keys_by_domain{'*'};
push(@{$dkim_signing_keys_by_domain{'*'}}, $j);
}
$j++;
}
do_log(0,"dkim: wildcard in signing domain (%s), may produce unverifiable ".
"signatures with no published public key, avoid!", $any_wild)
if $any_wild;
}
# THE get_dkim_key IS A DIRECT COPY OF THE SAME ROUTINE FROM amavisd
#
# Fetch a private DKIM signing key for a given signing domain, with its
# resource-record (RR) constraints compatible with proposed signature options.
# The first such key is returned as a hash; if no key is found an empty hash
# is returned. When a selector (s) is given it must match the selector of
# a key; when algorithm (a) is given, the key type and a hash algorithm must
# match the desired use too; the service type (s) must be 'email' or '*';
# when identity (i) is given it must match the granularity (g) of a key;
#
# sign.opts. key options
# ---------- -----------
# d => domain
# s => selector
# a => k, h(list)
# i => g, t=s
#
sub get_dkim_key(@) {
@_ % 2 == 0 or die "get_dkim_key: a list of pairs is expected as query opts";
my(%options) = @_; # signature options (v, a, c, d, h, i, l, q, s, t, x, z),
# of which d is required, while s, a and t are optional but taken into
# account in searching for a compatible key - the rest are ignored
my(%key_options);
my($domain) = $options{d};
defined $domain && $domain ne ''
or die "get_dkim_key: domain is required, but tag 'd' is missing";
$domain = lc($domain);
my(@indices) = $dkim_signing_keys_by_domain{$domain} ?
@{$dkim_signing_keys_by_domain{$domain}} :
$dkim_signing_keys_by_domain{'*'} ?
@{$dkim_signing_keys_by_domain{'*'}} : ();
if (@indices) {
my($selector) = $options{s};
$selector = $selector eq '' ? undef : lc($selector) if defined $selector;
local($1,$2);
my($keytype,$hashalg) =
defined $options{a} && $options{a} =~ /^([a-z0-9]+)-(.*)\z/is ? ($1,$2)
: ('rsa',undef);
my($identity_localpart,$identity_domain) =
!defined($options{i}) ? () : split_address($options{i});
$identity_localpart = '' if !defined $identity_localpart;
$identity_domain = '' if !defined $identity_domain;
# find the first key (associated with a domain) with compatible options
for my $j (@indices) {
my($ent) = $dkim_signing_keys_list[$j];
next unless defined $ent->{domain_re} ? $domain =~ $ent->{domain_re}
: $domain eq $ent->{domain};
next if defined $selector && $ent->{selector} ne $selector;
next if $keytype ne (exists $ent->{k} ? $ent->{k} : 'rsa');
next if exists $ent->{s} &&
!(grep { $_ eq '*' || $_ eq 'email' } split(/:/, $ent->{s}) );
next if defined $hashalg && exists $ent->{'h'} &&
!(grep { $_ eq $hashalg } split(/:/, $ent->{'h'}) );
if (defined($options{i})) {
if (lc($identity_domain) eq $domain) {
# ok
} elsif (exists $ent->{t} && (grep {$_ eq 's'} split(/:/,$ent->{t}))) {
next; # no subdomains allowed
}
if (!exists($ent->{g}) || $ent->{g} eq '*') {
# ok
} elsif ($ent->{g} =~ /^ ([^*]*) \* (.*) \z/xs) {
next if $identity_localpart !~ /^ \Q$1\E .* \Q$2\E \z/xs;
} else {
next if $identity_localpart ne $ent->{g};
}
}
%key_options = %$ent; last; # found a suitable match
}
}
if (defined $key_options{key_storage_ind}) {
# obtain actual key from @dkim_signing_keys_storage
($key_options{key}) =
@{$dkim_signing_keys_storage[$key_options{key_storage_ind}]};
}
%key_options;
}
sub proto_encode($@) {
my($attribute_name,@strings) = @_; local($1);
for ($attribute_name,@strings) {
# just in case, handle non-octet characters:
s/([^\000-\377])/sprintf('\\x{%04x}',ord($1))/eg and
do_log(-1,"proto_encode: non-octet character encountered: %s", $_);
}
$attribute_name =~ # encode all but alfanumerics, . _ + -
s/([^0-9a-zA-Z._+-])/sprintf("%%%02x",ord($1))/eg;
for (@strings) { # encode % and nonprintables
s/([^\041-\044\046-\176])/sprintf("%%%02x",ord($1))/eg;
}
$attribute_name . '=' . join(' ',@strings);
}
sub proto_decode($) {
my($str) = @_; local($1);
$str =~ s/%([0-9a-fA-F]{2})/pack("C",hex($1))/egs;
$str;
}
sub split_localpart($$) {
my($localpart, $delimiter) = @_;
my($owner_request_special) = 1; # configurable ???
my($extension); local($1,$2);
if ($localpart =~ /^(postmaster|mailer-daemon|double-bounce)\z/i) {
# do not split these, regardless of what the delimiter is
} elsif ($delimiter eq '-' && $owner_request_special &&
$localpart =~ /^owner-.|.-request\z/si) {
# don't split owner-foo or foo-request
} elsif ($localpart =~ /^(.+?)(\Q$delimiter\E.*)\z/s) {
($localpart, $extension) = ($1, $2); # extension includes a delimiter
# do not split the address if the result would have a null localpart
}
($localpart, $extension);
}
sub unique_ref(@) {
my($r) = @_ == 1 && ref($_[0]) ? $_[0] : \@_; # accept list, or a list ref
my(%seen); my(@result) = grep { defined($_) && !$seen{$_}++ } @$r;
\@result;
}
sub make_query_keys($$$;$) {
my($addr,$at_with_user,$include_bare_user,$append_string) = @_;
my($localpart,$domain) = split_address($addr); $domain = lc($domain);
my($saved_full_localpart) = $localpart;
$localpart = lc($localpart); ### if !c('localpart_is_case_sensitive');
# chop off leading @, and trailing dots
local($1);
$domain = $1 if $domain =~ /^\@?(.*?)\.*\z/s;
my($extension); my($delim) = '+'; ### c('recipient_delimiter');
if ($delim ne '') {
($localpart,$extension) = split_localpart($localpart,$delim);
# extension includes a delimiter since amavisd-new-2.5.0!
}
$extension = '' if !defined $extension; # mute warnings
my($append_to_user,$prepend_to_domain) = $at_with_user ? ('@','') : ('','@');
my(@keys); # a list of query keys
push(@keys, $addr); # as is
push(@keys, $localpart.$extension.'@'.$domain)
if $extension ne ''; # user+foo@example.com
push(@keys, $localpart.'@'.$domain); # user@example.com
if ($include_bare_user) { # typically enabled for local users only
push(@keys, $localpart.$extension.$append_to_user)
if $extension ne ''; # user+foo(@)
push(@keys, $localpart.$append_to_user); # user(@)
}
push(@keys, $prepend_to_domain.$domain); # (@)sub.example.com
if ($domain =~ /\[/) { # don't split address literals
push(@keys, $prepend_to_domain.'.'); # (@).
} else {
my(@dkeys); my($d) = $domain;
for (;;) { # (@).sub.example.com (@).example.com (@).com (@).
push(@dkeys, $prepend_to_domain.'.'.$d);
last if $d eq '';
$d = ($d =~ /^([^.]*)\.(.*)\z/s) ? $2 : '';
}
if (@dkeys > 10) { @dkeys = @dkeys[$#dkeys-9 .. $#dkeys] } # sanity limit
push(@keys,@dkeys);
}
if (defined $append_string && $append_string ne '') {
$_ .= $append_string for @keys;
}
my($keys_ref) = unique_ref(\@keys); # remove duplicates
ll(5) && do_log(5,"query_keys: %s", join(', ',@$keys_ref));
# the rhs replacement strings are similar to what would be obtained
# by lookup_re() given the following regular expression:
# /^( ( ( [^\@]*? ) ( \Q$delim\E [^\@]* )? ) (?: \@ (.*) ) )$/xs
my($rhs) = [ # a list of right-hand side replacement strings
$addr, # $1 = User+Foo@Sub.Example.COM
$saved_full_localpart, # $2 = User+Foo
$localpart, # $3 = user
$extension, # $4 = +foo
$domain, # $5 = sub.example.com
];
($keys_ref, $rhs);
}
sub lookup_hash($$;$%) {
my($addr, $hash_ref,$get_all,%options) = @_;
ref($hash_ref) eq 'HASH'
or die "lookup_hash: arg2 must be a hash ref: $hash_ref";
local($1,$2,$3,$4); my(@matchingkey,@result); my($append_string);
$append_string = $options{AppendStr} if defined $options{AppendStr};
my($keys_ref,$rhs_ref) = make_query_keys($addr,1,1,$append_string);
for my $key (@$keys_ref) { # do the search
if (exists $$hash_ref{$key}) { # got it
push(@result,$$hash_ref{$key}); push(@matchingkey,$key);
last if !$get_all;
}
}
# do the right-hand side replacements if any $n, ${n} or $(n) is specified
for my $r (@result) { # remember that $r is just an alias to array elements
if (defined($r) && !ref($r) && index($r,'$') >= 0) { # plain string with $
my($any) = $r =~ s{ \$ ( (\d+) | \{ (\d+) \} | \( (\d+) \) ) }
{ my($j)=$2+$3+$4; $j<1 ? '' : $rhs_ref->[$j-1] }gxse;
# bring taintedness of input to the result
$r .= substr($addr,0,0) if $any;
}
}
if (!$get_all) { ($result[0], $matchingkey[0]) }
else { (\@result, \@matchingkey) }
}
sub lookup2($$$%) {
my($get_all, $addr, $tables_ref, %options) = @_;
(@_ - 3) % 2 == 0 or die "lookup2: options argument not in pairs (not hash)";
my($label, @result,@matchingkey);
for my $tb (!$tables_ref ? () : @$tables_ref) {
my($t) = ref($tb) eq 'REF' ? $$tb : $tb; # allow one level of indirection
if (!ref($t) || ref($t) eq 'SCALAR') { # a scalar always matches
my($r) = ref($t) ? $$t : $t; # allow direct or indirect reference
if (defined $r) {
do_log(5,'lookup: (scalar) matches, result="%s"', $r);
push(@result,$r); push(@matchingkey,"(constant:$r)");
}
} elsif (ref($t) eq 'HASH') {
my($r,$mk);
($r,$mk) = lookup_hash($addr,$t,$get_all,%options) if %$t;
if (!defined $r) {}
elsif (!$get_all) { push(@result,$r); push(@matchingkey,$mk) }
elsif (@$r) { push(@result,@$r); push(@matchingkey,@$mk) }
} else {
die "TROUBLE: lookup table not implemented for object: " . ref($t);
}
last if @result && !$get_all;
}
if (!$get_all) { ($result[0], $matchingkey[0]) }
else { (\@result, \@matchingkey) }
}
sub parse_quoted_rfc2821($$) {
my($addr,$unquote) = @_;
# the angle-bracket stripping is not really a duty of this subroutine,
# as it should have been already done elsewhere, but we allow it here anyway:
$addr =~ s/^\s*<//s; $addr =~ s/>\s*\z//s; # tolerate unmatched angle brkts
local($1,$2); my($source_route,$localpart,$domain) = ('','','');
# RFC 2821: so-called "source route" MUST BE accepted,
# SHOULD NOT be generated, and SHOULD be ignored.
# Path = "<" [ A-d-l ":" ] Mailbox ">"
# A-d-l = At-domain *( "," A-d-l )
# At-domain = "@" domain
if (index($addr,':') >= 0 && # triage before more testing for source route
$addr =~ m{^ ( [ \t]* \@ (?: [0-9A-Za-z.!\#\$%&*/^{}=_+-]* |
\[ (?: \\. | [^\]\\] ){0,999} \] ) [ \t]*
(?: , [ \t]* \@ (?: [0-9A-Za-z.!\#\$%&*/^{}=_+-]* |
\[ (?: \\. | [^\]\\] ){0,999} \] ) [ \t]* )*
: [ \t]* ) (.*) \z }xs)
{ # NOTE: we are quite liberal on allowing whitespace around , and : here,
# and liberal in allowed character set and syntax of domain names,
# we mainly avoid stop-characters in the domain names of source route
$source_route = $1; $addr = $2;
}
if ($addr =~ m{^ ( .*? )
( \@ (?: [^\@\[\]]+ | \[ (?: \\. | [^\]\\] ){0,999} \]
| [^\@] )* )
\z}xs) {
($localpart,$domain) = ($1,$2);
} else {
($localpart,$domain) = ($addr,'');
}
$localpart =~ s/ " | \\ (.) | \\ \z /$1/xsg if $unquote; # undo quoted-pairs
($source_route, $localpart, $domain);
}
sub unquote_rfc2821_local($) {
my($mailbox) = @_;
my($source_route,$localpart,$domain) = parse_quoted_rfc2821($mailbox,1);
# make address with '@' in the localpart but no domain (like <"aa@bb.com"> )
# distinguishable from <aa@bb.com> by representing it as aa@bb.com@ in
# unquoted form; (it still obeys all regular rules, it is not a dirty trick)
$domain = '@' if $domain eq '' && $localpart ne '' && $localpart =~ /\@/;
$localpart . $domain;
}
#
# ======================================================================
# Code above is copied from amavisd; some day it should be factored out.
# Code from here on is specific to amavisd-signer.
# ======================================================================
#
# process a request to choose a signing key;
#
sub choose_key_request($) {
my($attr) = @_;
my(@results);
my(%sig_options); # signature options, and constraints for choosing a key
my(%key_options); # options associated with a signing key
my(@tried_domains); # used for logging a failure
my($chosen_addr,$chosen_addr_src);
my($cand) = $attr->{candidate};
my(@candidates) = !defined $cand ? () : !ref $cand ? $cand : @$cand;
my($sobm) = \@dkim_signature_options_bysender_maps;
for my $pair (@candidates) {
my($addr_src,$addr) = split(' ',$pair,2);
$addr = unquote_rfc2821_local($addr);
my($addr_localpart,$addr_domain) = split_address($addr);
$addr_domain = lc($addr_domain);
my($dkim_options_ref,$mk_ref) = lookup2(1,$addr,$sobm);
$dkim_options_ref = [] if !defined $dkim_options_ref; #***?
# place catchall default(s) at the end of the list of options;
push(@$dkim_options_ref, { c => 'relaxed/simple', a => 'rsa-sha256' });
%sig_options = (); # signature options:
# (v), a, (b), (bh), c, d, (h), i, (l), q, s, (t), x, (z)
# traverse from specific to general, first match wins
for my $opts_hash_ref (@$dkim_options_ref) {
while (my($k,$v) = each(%$opts_hash_ref))
{ $sig_options{$k} = $v if !exists($sig_options{$k}) }
}
# a default for a signing domain is a domain of each tried address
if (!exists($sig_options{d}))
{ my($d) = $addr_domain; $d =~ s/^\@//; $sig_options{d} = $d }
push(@tried_domains, $sig_options{d});
ll(5) && do_log(5, "signature options for %s(%s): %s", $addr,$addr_src,
join('; ', map { $_.'='.$sig_options{$_} } keys %sig_options));
# find a private key associated with a signing domain and selector,
# and meeting constraints
%key_options = get_dkim_key(%sig_options)
if defined $sig_options{d} && $sig_options{d} ne '';
my($key) = $key_options{key};
if (defined $key && $key ne '') { # found; copy the key and its options
$sig_options{key} = $key; $sig_options{s} = $key_options{selector};
$chosen_addr = $addr; $chosen_addr_src = $addr_src;
last;
}
}
# if any signature options were specified in the request and not overruled
# by more specific ones here, copy them to the resulting set of sig options
for my $opt (keys %$attr) {
if ($opt =~ /^sig\.(.+)\z/) {
$sig_options{$1} = $attr->{$opt} if !exists($sig_options{$1});
}
}
ll(5) && do_log(5, "sig options: %s",
join('; ', map { $_.'='.$sig_options{$_} } keys %sig_options));
my(%key_options);
if (defined $sig_options{d} && $sig_options{d} ne '') {
%key_options = get_dkim_key(%sig_options);
}
do_log(5, "key options: %s is %s",
$_, $key_options{$_}) for keys %key_options;
my($s) = $key_options{'selector'};
my($d) = $key_options{'domain'};
$sig_options{'s'} = $s;
$sig_options{'d'} = $d;
delete $sig_options{'key'}; # no use of key ref in the protocol
for my $opt (sort keys %sig_options) {
if (defined $sig_options{$opt}) {
push(@results, proto_encode('sig.'.$opt, $sig_options{$opt}));
}
}
# optional information if available: client may log it, or use for debugging
if (defined $chosen_addr_src && defined $chosen_addr) {
push(@results, proto_encode('chosen_candidate',
$chosen_addr_src, $chosen_addr));
}
\@results;
}
# sign a digest code using the specified algorithm and a private signing key
#
sub dkim_rsa_sign($$$) {
my($digest,$alg_name,$key) = @_;
my($result);
$digest = '' if !defined $digest;
$alg_name = '' if !defined $alg_name;
if (defined $key && $key ne '') {
my($key) = Mail::DKIM::PrivateKey->load(Cork => $key);
$key or die "no key available\n";
$result = $key->sign_digest($alg_name,$digest);
}
$result;
}
# process a request to sign the supplied digest with a selected key
#
# presence of the 'b' attribute in the result indicates success,
# otherwise the result is treated as signature unavailable
#
sub sign_request($) {
my($attr) = @_;
my(@results, $reason, $sig);
my($digest, $digest_alg, $selector, $domain) =
@$attr{qw(digest digest_alg s d)};
if (!defined $digest || $digest eq '') {
$reason = 'cannot sign, digest not provided, nothing to sign';
} elsif (!defined $digest_alg || $digest_alg eq '') {
$reason = 'cannot sign, digest algorithm name not provided';
} elsif (!defined $domain || $domain eq '') {
$reason = 'cannot sign, signing domain not provided';
} elsif (!defined $selector || $selector eq '') {
$reason = 'cannot sign, selector not provided';
} else {
my(%sig_options); # signature options: v, a, c, d, h, i, l, q, s, t, x, z
$sig_options{s} = $selector;
$sig_options{d} = $domain;
my(%key_options) = get_dkim_key(%sig_options);
if (!defined $key_options{key}) {
$reason = 'cannot sign, signing key not available';
} else {
do_log(5, "key options: %s is %s",
$_, $key_options{$_}) for keys %key_options;
eval {
$sig = dkim_rsa_sign(decode_base64($digest),
$digest_alg, $key_options{key}); 1;
} or do {
my($eval_stat) = $@ ne '' ? $@ : "errno=$!"; chomp $eval_stat;
do_log(0, "signing failed: %s", $eval_stat);
$reason = 'cannot sign: ' . $eval_stat;
};
push(@results, proto_encode('d', $key_options{'domain'}));
push(@results, proto_encode('s', $key_options{'selector'}));
}
}
if (defined $sig && $sig ne '') {
push(@results, proto_encode('b', encode_base64($sig,'')));
} else {
$reason = 'cannot sign: signing failed' if !defined $reason;
push(@results, proto_encode('reason', $reason));
}
\@results;
}
# process the request received from amavisd
#
sub do_the_request($) {
my($attr) = @_;
ll(2) && do_log(2, "got: %s", join('; ', map {
my($k) = $_; my($v) = $attr->{$k};
map { $k.'='.$_ } (!ref $v ? $v : @$v) } keys %$attr));
my(@results);
my($req_id) = $attr->{request_id};
my($log_id) = $attr->{log_id};
push(@results, proto_encode('request_id', $req_id)) if defined $req_id;
push(@results, proto_encode('log_id', $log_id)) if defined $log_id;
my($request_type) = $attr->{request};
$request_type = '' if !defined $request_type;
if ($request_type eq 'choose_key') {
push(@results, @{choose_key_request($attr)});
} elsif ($request_type eq 'sign') {
push(@results, @{sign_request($attr)});
} else {
push(@results, proto_encode('reason', 'unknown request type'));
do_log(2, "got: ignoring request: %s", $request_type);
}
ll(1) && do_log(1, "response: %s", join('; ', @results));
do_log(5, "");
\@results;
}
# IO::Multiplex -style callback hook
#
sub mux_connection {
my($self,$mux,$fh) = @_;
do_log(3, "client %s just connected", $self->{peeraddr});
$self->{attr} = {};
}
# the mux_connection callback is guaranteed to have already been run once
#
sub mux_input {
my($self,$mux,$fh,$in_ref) = @_;
my $attr = $self->{attr};
do_log(5, "input from %s ready", $self->{peeraddr});
# process each line in the input, leaving partial lines in the input buffer
local($1,$2); my($quit) = 0;
while ($$in_ref =~ s/^(.*?)\015?\012//) {
my($ln) = $1;
if ($ln eq '') { # empty line indicates end of a request
my($results_ref) = do_the_request($attr);
print(join('', map { $_."\015\012" } (@$results_ref,'')))
or do_log(0,"mux_input: error writing a response to socket" );
%$attr = (); # reset, awaiting next request in the same session
} elsif ($ln =~ /^ ([^=\000\012]*?) (?: = | : [ \t]* ) (.*) \z/xsi) {
my($attr_name) = proto_decode($1);
my($attr_val) = proto_decode($2);
if (!exists $attr->{$attr_name}) {
$attr->{$attr_name} = $attr_val; # simple scalar for one-time attrs
} elsif (!ref($attr->{$attr_name})) { # multiple, convert to a list
$attr->{$attr_name} = [ $attr->{$attr_name}, $attr_val ];
} else { # append to a list of same-name attributes
push(@{$attr->{$attr_name}}, $attr_val);
}
} else {
do_log(0, "mux_input: ignored line: %s", $ln);
}
}
close(STDOUT) if $quit;
}
#
# Main program starts here (after initializations near the top of this file)
#
dkim_key_postprocess();
# set up a Net::Server configuration
$server = AmavisSigner->new({
# limit socket bind (e.g. to the loopback interface)
host => (!defined $inet_socket_bind || $inet_socket_bind eq '' ? '*'
: $inet_socket_bind),
port => \@listen_sockets, # listen on these sockets (Unix or inet)
listen => $listen_queue_size, # undef for a default
user => ($> == 0 || $< == 0) ? $daemon_user : undef,
group => ($> == 0 || $< == 0) ? $daemon_group : undef,
background => $daemonize ? 1 : undef,
setsid => $daemonize ? 1 : undef,
chroot => $daemon_chroot_dir ne '' ? $daemon_chroot_dir : undef,
pid_file => $pid_file,
log_file => $daemonize ? 'Sys::Syslog' : undef,
syslog_ident => $syslog_ident,
syslog_facility => $syslog_facility,
syslog_logsock => 'native',
# 0=err, 1=warning, 2=notice, 3=info, 4=debug
log_level => $log_level >= 5 ? 4 : 2,
});
$server->run; # transferring control to Net::Server
exit 1; # shouldn't get here
# TODO: pkcs11 URI
# In order to use a key an application needs the path to the PKCS11 lib,
# the key ID, username, pin and the slot number
#
# http://blogs.sun.com/janp/entry/pkcs_11_engine_patch_including
# pkcs11:[object=<label>] # object (key) label, eg. "mykey"
# [;token=<label>] # token label
# [;manuf=<label>] # manufacturer ID
# [;serial=<label>] # serial number of the token
# [;model=<label>] # token model
# [;objecttype=(public|private|cert|data)]
# [;passphrasedialog=(builtin|exec:<file>)]
#
# alternative:
# pkcs11:///path/to/pkcs11/lib?slot=0&id=123
# file:///path/to/pem/file
#
# SEE: http://blog.nominet.org.uk/tech/category/crypto/