Extensions to JMAP for S​/​MIME signature verification
draft-ietf-jmap-smime-00

Abstract

This document specifies extension to JMAP for returning S​/​MIME signature verification status.

Status of This Memo

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Copyright Notice

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Table of Contents

• 1. Introduction
• 2. Conventions Used in This Document
• 3. Addition to the capabilities object
• 4. Extension to Email/get for S/MIME signature verification
• 5. Open Issues
• 6. IANA Considerations
• 6.1. JMAP capability registration for "smime"
• 7. Security Considerations
• 8. Normative References
• Author's Address

1. Introduction

[I-D.ietf-jmap-mail] is a JSON based application protocol for synchronising email data between a client and a server.

This document describes an extension to JMAP for returning S​/​MIME [RFC8551] signature verification status, without requiring a JMAP client to download the signature and all signed body parts or to download and decode CMS.

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" 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.

4. Extension to Email/get for S/MIME signature verification

[I-D.ietf-jmap-mail] defines Email/get method for retrieving message specific information. This document defines the following pseudo values in the _properties_ argument:
o *smimeStatus*: If "smimeStatus" is included in the list of requested properties, it MUST be interpreted by the server as a request to return "smimeStatus" property.

The "smimeStatus" response property is defined as follows:

*smimeStatus*: "String|null". null signifies that the message doesn't contain any signature. Possible string values of the property are listed below. Servers MAY return other values not defined below. Client MUST treat unrecognized values as "unknown":

unknown

S​/​MIME message, but it is neither signed, nor encrypted. This can also be returned for a multipart/signed message which contains unrecognized signing protocol (for example OpenPGP).

signed

S​/​MIME signed message, but the signature was not yet verified. Some servers might not attempt to verify signature until a particular message is requested by the client.

signed/verified

S​/​MIME signed message and the sender's signature was successfully verified, sender matches the From header field and the sender's certificate (and the certificate chain) is trusted for signing.

signed/failed

S​/​MIME signed message, but the signature failed to verify. This might be a policy related decision (message signer doesn't match the From header field), message was modified, the signer's certificate has expired or was revoked, etc.

        
      ["Email/get", {
      "ids": [ "f123u987" ],
      "properties": [ "mailboxIds", "from", "subject", "date", "smimeStatus" ]
      }, "#1"]
      
This will result in the following response:

      [["Email/get", {
         "accountId": "abc",
         "state": "41234123231",
         "list": [
           {
             id: "f123u457",
             mailboxIds: { "f123": true },
             from: [{name: "Joe Bloggs", email: "joe@bloggs.com"}],
             subject: "Dinner on Thursday?",
             date: "2013-10-13T14:12:00Z",
             smimeStatus: "signed/verified"
           }
         ]
      }, "#1"]]

Example

5. Open Issues

[[This section should be empty before publication]]

6. IANA Considerations

6.1. JMAP capability registration for "smime"

IANA is requested to register the "smime" JMAP Capability as follows:

Capability Name: "urn:ietf:params:jmap:smime"

Specification document: this document

Intended use: common

Change Controller: IETF

Security and privacy considerations: this document, Section 7

7. Security Considerations

Server side S​/​MIME signature verification requires the client to trust server verification code and configuration to perform S​/​MIME signature verification. For example, if the server is not configured with some Trust Anchors, some messages will have "signed/failed" status instead of "signed/verified".

TBD.

8. Normative References

Author's Address