From: Maximiliano Sandoval <m.sandoval@proxmox.com>
To: pmg-devel@lists.proxmox.com
Subject: [pmg-devel] [RFC PATCH] fix-2971: DKIM: Add setting to use From header when signing
Date: Wed, 3 Jan 2024 15:53:29 +0100 [thread overview]
Message-ID: <20240103145329.538668-1-m.sandoval@proxmox.com> (raw)
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 <m.sandoval@proxmox.com>
---
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
next reply other threads:[~2024-01-03 14:53 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-03 14:53 Maximiliano Sandoval [this message]
2024-01-10 21:39 ` Stoiko Ivanov
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