From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id 862BB94E1E for ; Fri, 23 Feb 2024 13:49:25 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 633C61875B for ; Fri, 23 Feb 2024 13:49:25 +0100 (CET) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [94.136.29.106]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS for ; Fri, 23 Feb 2024 13:49:24 +0100 (CET) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 64A3F44F66 for ; Fri, 23 Feb 2024 13:49:24 +0100 (CET) From: Maximiliano Sandoval To: pmg-devel@lists.proxmox.com Date: Fri, 23 Feb 2024 13:49:22 +0100 Message-Id: <20240223124922.426491-1-m.sandoval@proxmox.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SPAM-LEVEL: Spam detection results: 0 AWL 0.019 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record T_SCC_BODY_TEXT_LINE -0.01 - URIBL_BLOCKED 0.001 ADMINISTRATOR NOTICE: The query to URIBL was blocked. See http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block for more information. [dkimsign.pm, bcc.pm, config.pm, jetmore.org, ietf.org, accept.pm] Subject: [pmg-devel] [PATCH pmg-api v7] fix-2971: DKIM: add setting to use From header when signing X-BeenThere: pmg-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Mail Gateway development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 23 Feb 2024 12:49:25 -0000 Following RFC 5322 [2], we add an option to use the address from the `From:` header instead of the Envelope From address. >From RFC 7489 [1]: To illustrate, in relaxed mode, if a validated DKIM signature successfully verifies with a "d=" domain of "example.com", and the RFC5322.From address is "alerts@news.example.com", the DKIM "d=" domain and the RFC5322.From domain are considered to be "in alignment". In strict mode, this test would fail, since the "d=" domain does not exactly match the FQDN of the address. Tested with the following command: swaks --from foo@envelope.domain --to EMAIL -s PMG_ADDR:26 --data "Date: %DATE%\nTo: %TO_ADDRESS%\nFrom: bar@header.domain\nSubject: test %DATE%\nMessage-Id: <%MESSAGEID%>\nX-Mailer: swaks v%SWAKS_VERSION% jetmore.org/john/code/swaks/\n%NEW_HEADERS%\n%BODY%\n" Where EMAIL and PMG_ADDR are given adequate values, and envelope.domain and header.domain are in the 'Sign Domains' list. [1] https://datatracker.ietf.org/doc/html/rfc7489#section-3.1.1 [2] https://datatracker.ietf.org/doc/html/rfc5322#section-3.6.2 Signed-off-by: Maximiliano Sandoval --- Differences from vN-1: - Do not use uppercase in commit title - Rename dkim_use_domain to dkim-use-domain src/PMG/Config.pm | 8 +++++++ src/PMG/DKIMSign.pm | 48 ++++++++++++++++++++++++++++++++++------ src/PMG/RuleDB/Accept.pm | 3 +-- src/PMG/RuleDB/BCC.pm | 3 +-- src/bin/pmg-smtp-filter | 1 + 5 files changed, 52 insertions(+), 11 deletions(-) diff --git a/src/PMG/Config.pm b/src/PMG/Config.pm index 71d4c0b..0c5419e 100644 --- a/src/PMG/Config.pm +++ b/src/PMG/Config.pm @@ -134,6 +134,12 @@ EODESC description => "Default DKIM selector", type => 'string', format => 'dns-name', #see RFC6376 3.1 }, + 'dkim-use-domain' => { + description => "Whether to sign using the address from the header or the envelope.", + type => 'string', + enum => [qw(header envelope)], + default => 'envelope', + }, }; } @@ -152,6 +158,7 @@ sub options { dkim_sign => { optional => 1 }, dkim_sign_all_mail => { optional => 1 }, dkim_selector => { optional => 1 }, + 'dkim-use-domain' => { optional => 1 }, }; } @@ -1808,6 +1815,7 @@ my $pmg_service_params = { dkim_selector => 1, dkim_sign => 1, dkim_sign_all_mail => 1, + 'dkim-use-domain' => 1, }, }; diff --git a/src/PMG/DKIMSign.pm b/src/PMG/DKIMSign.pm index 08197f8..5df9aa8 100644 --- a/src/PMG/DKIMSign.pm +++ b/src/PMG/DKIMSign.pm @@ -2,6 +2,7 @@ package PMG::DKIMSign; use strict; use warnings; +use Email::Address::XS; use Mail::DKIM::Signer; use Mail::DKIM::TextWrap; use Crypt::OpenSSL::RSA; @@ -53,11 +54,16 @@ sub create_signature { #determines which domain should be used for signing based on the e-mailaddress sub signing_domain { - my ($self, $sender_email) = @_; - - my @parts = split('@', $sender_email); - die "no domain in sender e-mail\n" if scalar(@parts) < 2; - my $input_domain = $parts[-1]; + my ($self, $sender_email, $entity, $use_domain) = @_; + + my $input_domain; + if ($use_domain eq 'header') { + $input_domain = parse_headers_for_signing($entity); + } else { + my @parts = split('@', $sender_email); + die "no domain in sender e-mail\n" if scalar(@parts) < 2; + $input_domain = $parts[-1]; + } if ($self->{sign_all}) { $self->domain($input_domain) if $self->{sign_all}; @@ -84,8 +90,36 @@ sub signing_domain { } +sub parse_headers_for_signing { + # Following RFC 7489 [1], we only sign emails with exactly one sender in the + # From header. + # + # [1] https://datatracker.ietf.org/doc/html/rfc7489#section-6.6.1 + my ($entity) = @_; + + my @from_list; + + my @from_headers = $entity->head->get('from'); + foreach my $from_header (@from_headers) { + my @senders = Email::Address::XS->parse($from_header); + foreach my $sender (@senders) { + push(@from_list, @senders); + } + } + my $from_count = scalar(@from_list); + + if ($from_count == 1) { + return $from_list[0]->host(); + } +} + + sub sign_entity { - my ($entity, $selector, $sender, $sign_all) = @_; + my ($entity, $dkim, $sender) = @_; + + my $sign_all = $dkim->{sign_all}; + my $use_domain = $dkim->{use_domain}; + my $selector = $dkim->{selector}; die "no selector provided\n" if ! $selector; @@ -110,7 +144,7 @@ sub sign_entity { $signer->extended_headers($extended_headers); - if ($signer->signing_domain($sender)) { + if ($signer->signing_domain($sender, $entity, $use_domain)) { $entity->print($signer); my $signature = $signer->create_signature(); $entity->head->add('DKIM-Signature', $signature, 0); diff --git a/src/PMG/RuleDB/Accept.pm b/src/PMG/RuleDB/Accept.pm index 4ebd6da..d14c2fb 100644 --- a/src/PMG/RuleDB/Accept.pm +++ b/src/PMG/RuleDB/Accept.pm @@ -102,8 +102,7 @@ sub execute { if ($dkim->{sign}) { eval { - $entity = PMG::DKIMSign::sign_entity($entity, - $dkim->{selector}, $msginfo->{sender}, $dkim->{sign_all}); + $entity = PMG::DKIMSign::sign_entity($entity, $dkim, $msginfo->{sender}); }; syslog('warning', "Could not create DKIM-Signature - disabling Signing: $@") if $@; diff --git a/src/PMG/RuleDB/BCC.pm b/src/PMG/RuleDB/BCC.pm index 0f016f8..65b6fb5 100644 --- a/src/PMG/RuleDB/BCC.pm +++ b/src/PMG/RuleDB/BCC.pm @@ -142,8 +142,7 @@ sub execute { my $dkim = $msginfo->{dkim} // {}; if ($dkim->{sign}) { eval { - $entity = PMG::DKIMSign::sign_entity($entity, - $dkim->{selector}, $msginfo->{sender}, $dkim->{sign_all}); + $entity = PMG::DKIMSign::sign_entity($entity, $dkim, $msginfo->{sender}); }; syslog('warning', "Could not create DKIM-Signature - disabling Signing: $@") if $@; diff --git a/src/bin/pmg-smtp-filter b/src/bin/pmg-smtp-filter index dc7128c..6061459 100755 --- a/src/bin/pmg-smtp-filter +++ b/src/bin/pmg-smtp-filter @@ -636,6 +636,7 @@ sub handle_smtp { my $dkim_sign = $msginfo->{trusted} && $pmg_cfg->get('admin', 'dkim_sign'); if ($dkim_sign) { $msginfo->{dkim}->{sign} = $dkim_sign; + $msginfo->{dkim}->{use_domain} = $pmg_cfg->get('admin', 'dkim-use-domain'); $msginfo->{dkim}->{sign_all} = $pmg_cfg->get('admin', 'dkim_sign_all_mail'); $msginfo->{dkim}->{selector} = $pmg_cfg->get('admin', 'dkim_selector'); } -- 2.39.2