I have a collegue who is experimenting with signed mail (S/MIME).
He sent me a test mail and he also sent it to a test Mailman (2.1.11)
list. Here is the basic MIME header structure for the mail sent
directly to me:
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
MIME-Version: 1.0
Content-Type: multipart/signed;
micalg=SHA1;
protocol="application/x-pkcs7-signature";
boundary="----=_NextPart_000_0000_01C97713.0AE16F40"
This is a multi-part message in MIME format.
------=_NextPart_000_0000_01C97713.0AE16F40
Content-Type: multipart/alternative;
boundary="----=_NextPart_001_0001_01C97713.0AE16F40"
------=_NextPart_001_0001_01C97713.0AE16F40
Content-Type: text/plain;
charset="us-ascii"
Content-Transfer-Encoding: 7bit
<<the body of the mail>>
------=_NextPart_001_0001_01C97713.0AE16F40
Content-Type: text/html;
charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
<<the body of the mail in HTML-format>>
------=_NextPart_001_0001_01C97713.0AE16F40--
------=_NextPart_000_0000_01C97713.0AE16F40
Content-Type: application/x-pkcs7-signature;
name="smime.p7s"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="smime.p7s"
<<the base64-encoded digital signature>>
------=_NextPart_000_0000_01C97713.0AE16F40--
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
And here is the MIME structure after Mailman has processed the mail:
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="===============4389576766350830338=="
This is a multi-part message in MIME format.
--===============4389576766350830338==
Content-class: urn:content-classes:message
Content-Type: multipart/signed; micalg=SHA1;
protocol="application/x-pkcs7-signature";
boundary="----=_NextPart_000_0000_01C97713.0AE16F40"
This is a multi-part message in MIME format.
------=_NextPart_000_0000_01C97713.0AE16F40
Content-Type: multipart/alternative;
boundary="----=_NextPart_001_0001_01C97713.0AE16F40"
------=_NextPart_001_0001_01C97713.0AE16F40
Content-Type: text/plain;
charset="us-ascii"
Content-Transfer-Encoding: 7bit
<<the body of the mail>>
------=_NextPart_001_0001_01C97713.0AE16F40
Content-Type: text/html;
charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
<<the body of the mail in HTML-format>>
------=_NextPart_001_0001_01C97713.0AE16F40--
------=_NextPart_000_0000_01C97713.0AE16F40
Content-Type: application/x-pkcs7-signature;
name="smime.p7s"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="smime.p7s"
<<the base64-encoded digital signature>>
------=_NextPart_000_0000_01C97713.0AE16F40--
--===============4389576766350830338==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
<<the mailman-inserted footer>>
--===============4389576766350830338==--
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Note that Mailman has taken the existing three-part MIME structure
(plain-text body, HTML-formatted body, and digital signature) and
instead of placing the list footer as a fourth part in the same MIME
structure, Mailman has created a new two-part MIME structure with
the original three-part MIME structure as a first part and the list
footer as a second part. While this resulting structure is valid
MIME-encoding (I think), the result is that the initial header lines
Content-class: urn:content-classes:message
Content-Type: multipart/signed; micalg=SHA1;
protocol="application/x-pkcs7-signature";
boundary="----=_NextPart_000_0000_01C97713.0AE16F40"
are not at the beginning of the MIME structure. I believe that this
is causing the mail to appear as an unsigned mail message. I have just
begun reading "S/MIME 3.1" RFC 3851, and my initial quick reading
leads me to believe that this
Content-Type: multipart/signed;
header line needs to appear in the first part of the MIME headers
and not within a subsidiary MIME header.
Is there a reason why Mailman does not place the list footer as a
fourth section in the existing MIME structure? Thanks.
----------------------------------------------------------------------
Barry S. Finkel
Computing and Information Systems Division
Argonne National Laboratory Phone: +1 (630) 252-7277
9700 South Cass Avenue Facsimile:+1 (630) 252-4601
Building 222, Room D209 Internet: bsfin...@anl.gov
Argonne, IL 60439-4828 IBMMAIL: I1004994
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