Internet DRAFT - draft-ietf-jmap-smime-sender-extensions
draft-ietf-jmap-smime-sender-extensions
Network Working Group A. Melnikov
Internet-Draft Isode Ltd
Intended status: Informational 3 August 2023
Expires: 4 February 2024
JMAP extension for S/MIME signing and encryption
draft-ietf-jmap-smime-sender-extensions-04
Abstract
This document specifies an extension to JMAP for sending S/MIME
signed and/or S/MIME encrypted messages, as well as automatic
decryption of received S/MIME messages.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 4 February 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 2
3. Addition to the capabilities object . . . . . . . . . . . . . 2
4. Extension to Email/set for S/MIME signing and/or
encryption . . . . . . . . . . . . . . . . . . . . . . . 3
5. Extension to Email/get and Email/query for S/MIME
decryption . . . . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6.1. JMAP capability registration for "smime-advanced" . . . . 7
6.2. JMAP Error Codes Registry Updates . . . . . . . . . . . . 7
6.2.1. signedSenderNotAllowed error code . . . . . . . . . . 7
6.2.2. validEncryptionKeyNotFound error code . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. Normative References . . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
[RFC8621] is a JSON based application protocol for synchronising
email data between a client and a server.
This document describes an extension to JMAP for sending S/MIME
signed and/or encrypted messages, as well as automatic decryption of
received S/MIME messages. It allows JMAP server to sign/encrypt
messages on user's behalf.
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Addition to the capabilities object
The capabilities object is returned as part of the standard JMAP
Session object; see the JMAP spec. Servers supporting _this_
specification MUST add a property called "urn:ietf:params:jmap:smime-
advanced" to the capabilities object.
The value of this property is an empty object in both the JMAP
session _capabilities_ property and an account's
_accountCapabilities_ property.
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4. Extension to Email/set for S/MIME signing and/or encryption
[RFC8621] defines Email/set method for creating new email messages.
This document defines the following additional request arguments that
can be used to create S/MIME signed and/or encrypted messages:
* smimeSign: "Boolean" (default: false). If included and has the
value "true", this requests the JMAP server to create an S/MIME
signed message from the message constructed according to other
specified arguments (the "original message"). This is done by
encapsulating the original message either inside application/
pkcs7-mime [RFC8551] or multipart/signed [RFC1847] container.
(smimeSignOpaque argument (see below) controls which of the two
mechanisms is used.) The signature's private key/certificate is
associated with the email address in the Sender header field, if
present; otherwise, it is associated with the email address in the
From header field, if present.
If multiple addresses are present in one of these header fields,
or there is more than one Sender/From header field, the server
SHOULD reject the Email/set as invalid with the "invalidEmail"
error code; otherwise, it MUST take the first address in the last
Sender/From header field. If JMAP account is not authorized to
sign message as the selected sender (as above), it SHOULD return
"signedSenderNotAllowed" error code.
* smimeEncrypt: "Boolean" (default: false). If included and has the
value "true", this requests the JMAP server to create an S/MIME
encrypted message from the constructed message. This is done by
encapsulating the message inside application/pkcs7-mime [RFC8551]
media type. The message MUST be encrypted to the sender and all
To/Cc/Bcc recipients. This extension assumes that there is some
kind of per user or organizational addressbook, that can be used
to lookup public keys of recipients. If lookup of a particular
public key fails, or results in an expired or revoked certificate,
the Email/set operation MUST fail with the
"validEncryptionKeyNotFound" error code.
* smimeHeaderProtect: "Boolean" (default: true). If has the value
"true", this requests the JMAP server to use S/MIME header
protection as specified in [draft-ietf-lamps-header-protection]
when at least one of smimeEncrypt/smimeSign is true.
* smimeSignOpaque: "Boolean" (default: true). If has the value
"true", this requests the JMAP server to use application/
pkcs7-mime media type for S/MIME signing, otherwise multipart/
signed media type.
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If both "smimeSign" and "smimeEncrypt" are set to true, the message
is first signed and then the signed version is encrypted (in that
order).
(Note that this extension doesn't allow management of private keys/
certificates. How private keys are managed or configured for a
particular user is out of scope for this document.)
[[ "Email/set", {
"accountId": "ue150411c",
"create": {
"k192": {
"mailboxIds": {
"2ea1ca41b38e": true
},
"keywords": {
"$seen": true,
"$draft": true
},
"from": [{
"name": "Joe Bloggs",
"email": "joe@example.com"
}],
"subject": "World domination",
"receivedAt": "2021-07-07T01:03:11Z",
"sentAt": "2021-07-10T11:03:11+10:00",
"smimeSign": true,
"smimeEncrypt": true,
"bodyStructure": {
"type": "text/plain",
"partId": "bd48",
"header:Content-Language": "en"
},
"bodyValues": {
"bd48": {
"value": "I have the most brilliant plan. Let me tell
you all about it.",
"isTruncated": false
}
}
}
}
}, "0" ]]
This will result in the following response:
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[[ "Email/set", {
"accountId": "ue150411c",
"oldState": "780823",
"newState": "780839",
"created": {
"k192": {
"id": "Mf40b5f831efa7233b9eb1c7f",
"blobId": "Gf40b5f831efa7233b9eb1c7f8f97d84eeeee64f7",
"threadId": "Td957e72e89f516dc",
"size": 5096
}
},
...
}, "0" ]]
Figure 1: Example 1:
5. Extension to Email/get and Email/query for S/MIME decryption
[RFC8621] defines Email/get method for retrieving information about
email messages. This document defines the following additional
request arguments of the "bodyProperties" object that can be used to
facilitate decryption of S/MIME encrypted messages:
* smimeBlobId: "Id|null". The id representing the raw octets of the
decrypted contents of the part. When processing this request
argument, the server first removes the Content-Transfer-Encoding
(see then "blobId" request argument in RFC 8621). If the Content-
Transfer-Encoding is supported by the server, the content is then
S/MIME decrypted. The resulting Id can be used in Email/parse
method to import the decrypted message. If the body part is not
encrypted, the returned smimeBlobId attribute has the same value
as the "blobId" attribute.
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[[ "Email/get", {
"ids": [ "f123u986" ],
"properties": [ "threadId", "mailboxIds", "from", "subject",
"receivedAt", "htmlBody" ],
"bodyProperties": [ "partId", "smimeBlobId", "size", "type" ]
}, "#1" ]]
This will result in the following response:
[[ "Email/get", {
"accountId": "abc",
"state": "41234123231",
"list": [
{
"id": "f123u986",
"threadId": "cb1314a",
"mailboxIds": { "da123c": true },
"from": [{ "name": "Mice Ace", "email": "mike@example.com" }],
"subject": "Dinner on Saturday?",
"receivedAt": "2023-03-09T14:12:00Z",
"htmlBody": [{
"partId": "1",
"smimeBlobId": "B841623871",
"size": 120537,
"type": "text/html"
}]
}
]
}, "#1" ]]
Figure 2: Example 2:
[RFC8621] defines Email/query method for searching for email
messages. This document defines the following additional request
arguments to the *FilterCondition* object that can be used to search
for S/MIME encrypted messages:
* isEncrypted: "Boolean" (default: false) If isEncrypted is true,
then an Email matches this condition if its top level body part
has content type "application/pkcs7-mime" with smime-type
parameter that has the case-insensitive value "enveloped-data" or
"authEnveloped-data". [[Alexey: Do we want to limit this to S/
MIME encryption and not OpenPGP?]]
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* isNotEncrypted: "Boolean" (default: false) If isNotEncrypted is
true, then an Email matches this condition if its top level body
part has any content type other than "application/pkcs7-mime", or
its top level body part has content type "application/pkcs7-mime"
but the smime-type parameter has the case-insensitive value other
than "enveloped-data" or "authEnveloped-data". [[Alexey: what if
smime-type is absent? It is defined as optional! Shall we make
compliant server implementations test the inner CMS structure
type?]]
6. IANA Considerations
6.1. JMAP capability registration for "smime-advanced"
IANA is requested to register the "smime" JMAP Capability as follows:
Capability Name: "urn:ietf:params:jmap:smime-advanced"
Specification document: this document
Intended use: common
Change Controller: IETF
Security and privacy considerations: this document, Section 7
6.2. JMAP Error Codes Registry Updates
6.2.1. signedSenderNotAllowed error code
JMAP Error Code: signedSenderNotAllowed
Intended use: common
Change controller: IETF
Reference: This document, Section 4
Description: JMAP account is not authorized to S/MIME sign message as
the specified sender.
6.2.2. validEncryptionKeyNotFound error code
JMAP Error Code: validEncryptionKeyNotFound
Intended use: common
Change controller: IETF
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Reference: This document, Section 4
Description: S/MIME encrypted message can't be generated because no
valid certificate (non expired and non revoked) can be found for one
of recipients.
7. Security Considerations
This JMAP extension assumes trust between the user and the JMAP
server for purposes of signing and encrypting messages on user's
behalf.
This JMAP extension also relies on access to user's (or
organization's) addressbook which contain up-to-date certificates for
recipients.
This JMAP extension doesn't support management of user's private keys
and corresponding certificates.
8. Normative References
[RFC1847] Galvin, J., Murphy, S., Crocker, S., and N. Freed,
"Security Multiparts for MIME: Multipart/Signed and
Multipart/Encrypted", RFC 1847, DOI 10.17487/RFC1847,
October 1995, <https://www.rfc-editor.org/info/rfc1847>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8550] Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
Certificate Handling", RFC 8550, DOI 10.17487/RFC8550,
April 2019, <https://www.rfc-editor.org/info/rfc8550>.
[RFC8551] Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
Message Specification", RFC 8551, DOI 10.17487/RFC8551,
April 2019, <https://www.rfc-editor.org/info/rfc8551>.
[RFC8620] Jenkins, N. and C. Newman, "The JSON Meta Application
Protocol (JMAP)", RFC 8620, DOI 10.17487/RFC8620, July
2019, <https://www.rfc-editor.org/info/rfc8620>.
[RFC8621] Jenkins, N. and C. Newman, "The JSON Meta Application
Protocol (JMAP) for Mail", RFC 8621, DOI 10.17487/RFC8621,
August 2019, <https://www.rfc-editor.org/info/rfc8621>.
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[draft-ietf-lamps-header-protection]
Gillmor, D. K., Hoeneisen, B., and A. Melnikov, "Header
Protection for Cryptographically Protected E-mail", Work
in Progress, Internet-Draft, draft-ietf-lamps-header-
protection-13, 10 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-lamps-
header-protection-13>.
Author's Address
Alexey Melnikov
Isode Ltd
14 Castle Mews
Hampton
TW12 2NP
United Kingdom
Email: Alexey.Melnikov@isode.com
Melnikov Expires 4 February 2024 [Page 9]
