* [pmg-devel] [PATCH pmg-api v4] fix-2971: DKIM: Add setting to use From header when signing
@ 2024-01-16 10:43 Maximiliano Sandoval
2024-02-15 19:21 ` Stoiko Ivanov
0 siblings, 1 reply; 3+ messages in thread
From: Maximiliano Sandoval @ 2024-01-16 10:43 UTC (permalink / raw)
To: pmg-devel
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 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@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/rfc7489#section-3.1.1
[2] https://datatracker.ietf.org/doc/html/rfc5322#section-3.6.2
Signed-off-by: Maximiliano Sandoval <m.sandoval@proxmox.com>
---
Do note that for testing one has to restart pmg-smtp-filter after changing the setting value.
Differences from v3:
- Take into account setting
- rename parsing function to parse_headers_for_signing
src/PMG/Config.pm | 7 ++++
src/PMG/DKIMSign.pm | 72 ++++++++++++++++++++++++++++++++++++----
src/PMG/RuleDB/Accept.pm | 3 +-
src/PMG/RuleDB/BCC.pm | 3 +-
src/bin/pmg-smtp-filter | 1 +
5 files changed, 75 insertions(+), 11 deletions(-)
diff --git a/src/PMG/Config.pm b/src/PMG/Config.pm
index 7339e0d..840c0ad 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_prefer_rfc5322_domain => {
+ 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_prefer_rfc5322_domain => { optional => 1 },
};
}
@@ -1788,6 +1794,7 @@ my $pmg_service_params = {
dkim_selector => 1,
dkim_sign => 1,
dkim_sign_all_mail => 1,
+ dkim_prefer_rfc5322_domain => 1,
},
};
diff --git a/src/PMG/DKIMSign.pm b/src/PMG/DKIMSign.pm
index 08197f8..2c73101 100644
--- a/src/PMG/DKIMSign.pm
+++ b/src/PMG/DKIMSign.pm
@@ -2,6 +2,7 @@ package PMG::DKIMSign;
use strict;
use warnings;
+use Email::Address::XS;
use Mail::DKIM::Signer;
use Mail::DKIM::TextWrap;
use Crypt::OpenSSL::RSA;
@@ -53,11 +54,16 @@ sub create_signature {
#determines which domain should be used for signing based on the e-mailaddress
sub signing_domain {
- my ($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, $prefer_rfc5322_domain) = @_;
+
+ my $input_domain;
+ if ($prefer_rfc5322_domain) {
+ $input_domain = parse_headers_for_signing($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 $self->{sign_all};
@@ -84,8 +90,60 @@ sub signing_domain {
}
+sub parse_headers_for_signing {
+ # If there is exactly one single address in the 'From' header we use that
+ # address for signing, otherwise we use the 'Sender' header.
+ my ($entity) = @_;
+
+ my @sender_list;
+ 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) {
+ my @send_headers = $entity->head->get('sender');
+ foreach my $send_header (@send_headers) {
+ my @senders = Email::Address::XS->parse($send_header);
+ foreach my $sender (@senders) {
+ push(@sender_list, $sender);
+ }
+ }
+ my $send_count = scalar(@sender_list);
+
+ if ($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 $sender_list[0]->host();
+ } else {
+ syslog(
+ 'warning',
+ "Email has multiple addresses in its 'From' header and no 'Sender'"
+ ." header, it won't be signed. See RFC 5322 Section 3.6.2"
+ );
+ }
+ } elsif ($from_count == 1) {
+ return $from_list[0]->host();
+ }
+}
+
+
sub sign_entity {
- my ($entity, $selector, $sender, $sign_all) = @_;
+ my ($entity, $dkim, $sender) = @_;
+
+ my $sign_all = $dkim->{sign_all};
+ my $prefer_rfc5322_domain = $dkim->{prefer_rfc5322_domain};
+ my $selector = $dkim->{selector};
die "no selector provided\n" if ! $selector;
@@ -110,7 +168,7 @@ sub sign_entity {
$signer->extended_headers($extended_headers);
- if ($signer->signing_domain($sender)) {
+ if ($signer->signing_domain($sender, $entity, $prefer_rfc5322_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 7da3de8..f7502f2 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}->{prefer_rfc5322_domain} = $pmg_cfg->get('admin', 'dkim_prefer_rfc5322_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
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [pmg-devel] [PATCH pmg-api v4] fix-2971: DKIM: Add setting to use From header when signing
2024-01-16 10:43 [pmg-devel] [PATCH pmg-api v4] fix-2971: DKIM: Add setting to use From header when signing Maximiliano Sandoval
@ 2024-02-15 19:21 ` Stoiko Ivanov
2024-02-16 12:36 ` Maximiliano Sandoval
0 siblings, 1 reply; 3+ messages in thread
From: Stoiko Ivanov @ 2024-02-15 19:21 UTC (permalink / raw)
To: Maximiliano Sandoval; +Cc: pmg-devel
Thanks for the update!
I got around to give it a spin in my testbed - and it looks ok from a
quick spin.
The docs-patch would be great for the next version!
a few comments inline:
On Tue, 16 Jan 2024 11:43:01 +0100
Maximiliano Sandoval <m.sandoval@proxmox.com> wrote:
> 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 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@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/rfc7489#section-3.1.1
> [2] https://datatracker.ietf.org/doc/html/rfc5322#section-3.6.2
>
> Signed-off-by: Maximiliano Sandoval <m.sandoval@proxmox.com>
> ---
> Do note that for testing one has to restart pmg-smtp-filter after changing the setting value.
>
> Differences from v3:
> - Take into account setting
> - rename parsing function to parse_headers_for_signing
>
> src/PMG/Config.pm | 7 ++++
> src/PMG/DKIMSign.pm | 72 ++++++++++++++++++++++++++++++++++++----
> src/PMG/RuleDB/Accept.pm | 3 +-
> src/PMG/RuleDB/BCC.pm | 3 +-
> src/bin/pmg-smtp-filter | 1 +
> 5 files changed, 75 insertions(+), 11 deletions(-)
>
> diff --git a/src/PMG/Config.pm b/src/PMG/Config.pm
> index 7339e0d..840c0ad 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_prefer_rfc5322_domain => {
I checked what others do for those hard-to-name things - maybe we could
orient ourselves on other mail-filters:
* https://rspamd.com/doc/modules/dkim_signing.html (dkim_use_domain a enum
with "envelope" and "header") - one upside is that that will remain a
term even if RFC5322 is obsoleted at some future point...
* opendkim seems to only use header information (but lets you select the
headers, which are search, which I'd like to avoid for usage-simplicity)
- http://opendkim.org/opendkim.conf.5.html
> + 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_prefer_rfc5322_domain => { optional => 1 },
> };
> }
>
> @@ -1788,6 +1794,7 @@ my $pmg_service_params = {
> dkim_selector => 1,
> dkim_sign => 1,
> dkim_sign_all_mail => 1,
> + dkim_prefer_rfc5322_domain => 1,
> },
> };
>
> diff --git a/src/PMG/DKIMSign.pm b/src/PMG/DKIMSign.pm
> index 08197f8..2c73101 100644
> --- a/src/PMG/DKIMSign.pm
> +++ b/src/PMG/DKIMSign.pm
> @@ -2,6 +2,7 @@ package PMG::DKIMSign;
>
> use strict;
> use warnings;
> +use Email::Address::XS;
> use Mail::DKIM::Signer;
> use Mail::DKIM::TextWrap;
> use Crypt::OpenSSL::RSA;
> @@ -53,11 +54,16 @@ sub create_signature {
>
> #determines which domain should be used for signing based on the e-mailaddress
> sub signing_domain {
> - my ($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, $prefer_rfc5322_domain) = @_;
> +
> + my $input_domain;
> + if ($prefer_rfc5322_domain) {
> + $input_domain = parse_headers_for_signing($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 $self->{sign_all};
> @@ -84,8 +90,60 @@ sub signing_domain {
> }
>
>
> +sub parse_headers_for_signing {
> + # If there is exactly one single address in the 'From' header we use that
> + # address for signing, otherwise we use the 'Sender' header.
as hinted in my reply to your v1:
https://lists.proxmox.com/pipermail/pmg-devel/2024-January/002625.html
if I read the DMARC-RFC right this fallback is not wanted there
(and DKIM itself does not mention that the dkim-domain (d= tag in the
signature header, would need to be particularly related to either header
or envelope-addresses)
> + my ($entity) = @_;
> +
> + my @sender_list;
> + 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) {
> + my @send_headers = $entity->head->get('sender');
> + foreach my $send_header (@send_headers) {
> + my @senders = Email::Address::XS->parse($send_header);
> + foreach my $sender (@senders) {
> + push(@sender_list, $sender);
> + }
> + }
> + my $send_count = scalar(@sender_list);
> +
> + if ($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 $sender_list[0]->host();
> + } else {
> + syslog(
> + 'warning',
> + "Email has multiple addresses in its 'From' header and no 'Sender'"
> + ." header, it won't be signed. See RFC 5322 Section 3.6.2"
> + );
> + }
> + } elsif ($from_count == 1) {
> + return $from_list[0]->host();
> + }
> +}
> +
> +
> sub sign_entity {
> - my ($entity, $selector, $sender, $sign_all) = @_;
> + my ($entity, $dkim, $sender) = @_;
> +
> + my $sign_all = $dkim->{sign_all};
> + my $prefer_rfc5322_domain = $dkim->{prefer_rfc5322_domain};
> + my $selector = $dkim->{selector};
>
> die "no selector provided\n" if ! $selector;
>
> @@ -110,7 +168,7 @@ sub sign_entity {
>
> $signer->extended_headers($extended_headers);
>
> - if ($signer->signing_domain($sender)) {
> + if ($signer->signing_domain($sender, $entity, $prefer_rfc5322_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 7da3de8..f7502f2 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}->{prefer_rfc5322_domain} = $pmg_cfg->get('admin', 'dkim_prefer_rfc5322_domain');
> $msginfo->{dkim}->{sign_all} = $pmg_cfg->get('admin', 'dkim_sign_all_mail');
> $msginfo->{dkim}->{selector} = $pmg_cfg->get('admin', 'dkim_selector');
> }
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [pmg-devel] [PATCH pmg-api v4] fix-2971: DKIM: Add setting to use From header when signing
2024-02-15 19:21 ` Stoiko Ivanov
@ 2024-02-16 12:36 ` Maximiliano Sandoval
0 siblings, 0 replies; 3+ messages in thread
From: Maximiliano Sandoval @ 2024-02-16 12:36 UTC (permalink / raw)
To: Stoiko Ivanov; +Cc: pmg-devel
Stoiko Ivanov <s.ivanov@proxmox.com> writes:
>> + dkim_prefer_rfc5322_domain => {
> I checked what others do for those hard-to-name things - maybe we could
> orient ourselves on other mail-filters:
> * https://rspamd.com/doc/modules/dkim_signing.html (dkim_use_domain a enum
> with "envelope" and "header") - one upside is that that will remain a
> term even if RFC5322 is obsoleted at some future point...
> * opendkim seems to only use header information (but lets you select the
> headers, which are search, which I'd like to avoid for usage-simplicity)
> - http://opendkim.org/opendkim.conf.5.html
👍 for using dkim_use_domain as a setting name with possible values
being 'envelope', 'header'. Will send v5 in a bit.
--
Maximiliano
^ permalink raw reply [flat|nested] 3+ messages in thread
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2024-01-16 10:43 [pmg-devel] [PATCH pmg-api v4] fix-2971: DKIM: Add setting to use From header when signing Maximiliano Sandoval
2024-02-15 19:21 ` Stoiko Ivanov
2024-02-16 12:36 ` Maximiliano Sandoval
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