[pmg-devel] [PATCH pmg-api v2] rulesystem: limit linelength of disclaimer to 998 bytes

[pmg-devel] [PATCH pmg-api v2] rulesystem: limit linelength of disclaimer to 998 bytes

[Stoiko Ivanov]

As described in
http://www.postfix.org/postconf.5.html#smtp_line_length_limit

postfix splits lines which are longer by inserting <cr><lf><space> to
adhere with RFC 5322 (section 2.1.1):
https://datatracker.ietf.org/doc/html/rfc5322#section-2.1.1
(or actually section 4.5.3.1.6. where characters are translated to
octets)

If a longer line is part of the disclaimer pmg-smtp-filter adds it
without this modification, which breaks DKIM signatures (since the
body is modified by postfix after the body hash is computed)

regular-expression matching is used instead of length(), because the
limit is on line-length (and a disclaimer can contain multiple lines)

reported in our community forum:
https://forum.proxmox.com/threads/.97919/

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
---
v2->v1:
* incorporated Thomas' feedback - huge thanks!
* replaced the 2/3 occurences of encode('UTF-8',...) by a temporary varialbe
* read up quite a bit on the magic world of encoding)
* verified that the encoded value is indeed the one we want to compare
  against

 src/PMG/RuleDB/Disclaimer.pm | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/PMG/RuleDB/Disclaimer.pm b/src/PMG/RuleDB/Disclaimer.pm
index 1b1accf..d3003b2 100644
--- a/src/PMG/RuleDB/Disclaimer.pm
+++ b/src/PMG/RuleDB/Disclaimer.pm
@@ -84,12 +84,17 @@ sub save {
     defined($self->{ogroup}) || die "undefined object attribute: ERROR";
     defined($self->{value}) || die "undefined object attribute: ERROR";
 
+    my $value = encode('UTF-8', $self->{value});
+    if ($value =~ /^.{998,}$/m) {
+	die "too long line in disclaimer - breaks RFC 5322!\n";
+    }
+
     if (defined ($self->{id})) {
 	# update
 	
 	$ruledb->{dbh}->do(
 	    "UPDATE Object SET Value = ? WHERE ID = ?", 
-	    undef, encode('UTF-8', $self->{value}), $self->{id});
+	    undef, $value, $self->{id});
 
     } else {
 	# insert
@@ -98,7 +103,7 @@ sub save {
 	    "INSERT INTO Object (Objectgroup_ID, ObjectType, Value) " .
 	    "VALUES (?, ?, ?);");
 
-	$sth->execute($self->ogroup, $self->otype, encode('UTF-8', $self->{value}));
+	$sth->execute($self->ogroup, $self->otype, $value);
     
 	$self->{id} = PMG::Utils::lastid($ruledb->{dbh}, 'object_id_seq'); 
     }
-- 
2.30.2

[pmg-devel] applied: [PATCH pmg-api v2] rulesystem: limit linelength of disclaimer to 998 bytes

[Thomas Lamprecht]

On 24.11.21 22:00, Stoiko Ivanov wrote:
> As described in
> http://www.postfix.org/postconf.5.html#smtp_line_length_limit
> 
> postfix splits lines which are longer by inserting <cr><lf><space> to
> adhere with RFC 5322 (section 2.1.1):
> https://datatracker.ietf.org/doc/html/rfc5322#section-2.1.1
> (or actually section 4.5.3.1.6. where characters are translated to
> octets)
> 
> If a longer line is part of the disclaimer pmg-smtp-filter adds it
> without this modification, which breaks DKIM signatures (since the
> body is modified by postfix after the body hash is computed)
> 
> regular-expression matching is used instead of length(), because the
> limit is on line-length (and a disclaimer can contain multiple lines)
> 
> reported in our community forum:
> https://forum.proxmox.com/threads/.97919/
> 
> Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
> ---
> v2->v1:
> * incorporated Thomas' feedback - huge thanks!
> * replaced the 2/3 occurences of encode('UTF-8',...) by a temporary varialbe

great that it could roughly stay the same amount of work, the memory scan should
be rather cheap.

> * read up quite a bit on the magic world of encoding)
> * verified that the encoded value is indeed the one we want to compare
>   against
> 
>  src/PMG/RuleDB/Disclaimer.pm | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
>

applied, thanks!