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 5E8CDBEFD4 for ; Wed, 3 Jan 2024 15:53:35 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 45A55342BC for ; Wed, 3 Jan 2024 15:53:35 +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 ; Wed, 3 Jan 2024 15:53:31 +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 5BE9C40BC4 for ; Wed, 3 Jan 2024 15:53:31 +0100 (CET) From: Maximiliano Sandoval To: pmg-devel@lists.proxmox.com Date: Wed, 3 Jan 2024 15:53:29 +0100 Message-Id: <20240103145329.538668-1-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 0.002 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. [ietf.org, accept.pm, bcc.pm, config.pm, dkimsign.pm, jetmore.org] Subject: [pmg-devel] [RFC PATCH] 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: Wed, 03 Jan 2024 14:53:35 -0000 We add an option to use the address from the `From:` header instead of the Envelope From address. Following RFC 5322 [2], we use the `Sender:` header when there are multiple addresses in the `From:` header. >From RFC 6376 [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. Current Problems: - `dkim_sign_rfc5322` is probably not a descriptive name for the setting - The setting description might be improved upon Tested with the following command: swaks --from foo@bar1 --to EMAIL -s PMG_ADDR:26 --data "Date: %DATE%\nTo: %TO_ADDRESS%\nFrom: foo@bar2\nSubject: test %DATE%\nMessage-Id: <%MESSAGEID%>\nX-Mailer: swaks v%SWAKS_VERSION% jetmore.org/john/code/swaks/\n%NEW_HEADERS%\n%BODY%\n" [1] https://datatracker.ietf.org/doc/html/rfc6376 [2] https://datatracker.ietf.org/doc/html/rfc5322#section-3.6.2 Signed-off-by: Maximiliano Sandoval --- src/PMG/Config.pm | 7 +++++++ src/PMG/DKIMSign.pm | 43 +++++++++++++++++++++++++++++++++++++++- src/PMG/RuleDB/Accept.pm | 2 +- src/PMG/RuleDB/BCC.pm | 2 +- src/bin/pmg-smtp-filter | 1 + 5 files changed, 52 insertions(+), 3 deletions(-) diff --git a/src/PMG/Config.pm b/src/PMG/Config.pm index 7339e0d..b6c61e1 100644 --- a/src/PMG/Config.pm +++ b/src/PMG/Config.pm @@ -134,6 +134,11 @@ EODESC description => "Default DKIM selector", type => 'string', format => 'dns-name', #see RFC6376 3.1 }, + dkim_sign_rfc5322 => { + description => "Whether to use the address from the From header when DKIM signing outbound mails.", + type => 'boolean', + default => 0, + }, }; } @@ -152,6 +157,7 @@ sub options { dkim_sign => { optional => 1 }, dkim_sign_all_mail => { optional => 1 }, dkim_selector => { optional => 1 }, + dkim_sign_rfc5322 => { optional => 1 }, }; } @@ -1788,6 +1794,7 @@ my $pmg_service_params = { dkim_selector => 1, dkim_sign => 1, dkim_sign_all_mail => 1, + dkim_sign_rfc5322 => 1, }, }; diff --git a/src/PMG/DKIMSign.pm b/src/PMG/DKIMSign.pm index 08197f8..009313d 100644 --- a/src/PMG/DKIMSign.pm +++ b/src/PMG/DKIMSign.pm @@ -84,8 +84,49 @@ sub signing_domain { } +sub parse_signing_sender { + # If there is exactly one single address in the 'From' header we use that + # address for signing, otherwise we use the 'Sender' header. + my ($entity) = @_; + + my $from_count = 0; + my @from_headers = $entity->head->get('from'); + foreach my $from_header (@from_headers) { + my @senders = split(',', $from_header); + $from_count += scalar(@senders); + } + + if ($from_count > 1) { + my $send_count = 0; + my @send_headers = $entity->head->get('sender'); + foreach my $send_header (@send_headers) { + my @senders = split(',', $send_header); + $send_count += scalar(@senders); + } + if ($send_count > 1) { + syslog('warning', "Email has more than one address in its 'Sender' " . + "it won't be signed. See RFC 5322 Section 3.6.2"); + } elsif ($send_count == 1) { + return $entity->head->get('sender', 0); + } else { + syslog('warning', "Email has multiple addresses in its 'From' header " . + "and no 'Sender' header, it won't be signed. See RFC 5322 Section 3.6.2"); + } + } elsif ($from_count == 1) { + return $entity->head->get('from', 0); + } +} + + sub sign_entity { - my ($entity, $selector, $sender, $sign_all) = @_; + my ($entity, $dkim, $sender) = @_; + + my $sign_all = $dkim->{sign_all}; + my $selector = $dkim->{selector}; + + if ($dkim->{sign_rfc5322}) { + $sender = parse_signing_sender($entity); + } die "no selector provided\n" if ! $selector; diff --git a/src/PMG/RuleDB/Accept.pm b/src/PMG/RuleDB/Accept.pm index 4ebd6da..2e1bfa7 100644 --- a/src/PMG/RuleDB/Accept.pm +++ b/src/PMG/RuleDB/Accept.pm @@ -103,7 +103,7 @@ sub execute { if ($dkim->{sign}) { eval { $entity = PMG::DKIMSign::sign_entity($entity, - $dkim->{selector}, $msginfo->{sender}, $dkim->{sign_all}); + $dkim, $msginfo->{sender}); }; syslog('warning', "Could not create DKIM-Signature - disabling Signing: $@") if $@; diff --git a/src/PMG/RuleDB/BCC.pm b/src/PMG/RuleDB/BCC.pm index 0f016f8..6db48af 100644 --- a/src/PMG/RuleDB/BCC.pm +++ b/src/PMG/RuleDB/BCC.pm @@ -143,7 +143,7 @@ sub execute { if ($dkim->{sign}) { eval { $entity = PMG::DKIMSign::sign_entity($entity, - $dkim->{selector}, $msginfo->{sender}, $dkim->{sign_all}); + $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 7da3de8..549dbd4 100755 --- a/src/bin/pmg-smtp-filter +++ b/src/bin/pmg-smtp-filter @@ -627,6 +627,7 @@ sub handle_smtp { my $dkim_sign = $msginfo->{trusted} && $pmg_cfg->get('admin', 'dkim_sign'); if ($dkim_sign) { $msginfo->{dkim}->{sign} = $dkim_sign; + $msginfo->{dkim}->{sign_rfc5322} = $pmg_cfg->get('admin', 'dkim_sign_rfc5322'); $msginfo->{dkim}->{sign_all} = $pmg_cfg->get('admin', 'dkim_sign_all_mail'); $msginfo->{dkim}->{selector} = $pmg_cfg->get('admin', 'dkim_selector'); } -- 2.39.2