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URN Namespace

Overview​

This document describes the 'stalwart' Uniform Resource Name (URN) namespace, which provides persistent, location-independent identifiers for resources related to the Stalwart Mail and Collaboration Server.

The namespace identifier (NID) is: stalwart

Purpose​

The 'stalwart' URN namespace is used to provide unique identifiers for:

  1. Custom JMAP extensions (RFC 8620)
  2. WebDAV lock tokens (RFC 4918)
  3. WebDAV synchronization tokens (RFC 6578)

Syntax​

URNs in the 'stalwart' namespace have the following structure:

urn:stalwart:{resource-type}:{specific-identifier}

Where:

  • urn: is the URI scheme
  • stalwart is the namespace identifier (NID)
  • {resource-type} identifies the category of resource
  • {specific-identifier} is the unique identifier for that resource

Resource Types​

Version 1 of this specification defines the following resource types:

  1. jmap - Used for JMAP protocol extensions
  2. davlock - Used for WebDAV lock tokens
  3. davsync - Used for WebDAV synchronization tokens

Specific Identifier Format​

The format of the specific identifier depends on the resource type:

Resource TypeSpecific Identifier FormatExample
jmapText string identifying the extensionmailfilter, calendar-settings
davlock128-bit number encoded as hexadecimala1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6
davsync64-bit number encoded as hexadecimala1b2c3d4e5f6a7b8

Examples​

Here are examples of valid URNs in the 'stalwart' namespace:

  • urn:stalwart:jmap:mailfilter
  • urn:stalwart:jmap:calendar-settings
  • urn:stalwart:davlock:a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6
  • urn:stalwart:davsync:a1b2c3d4e5f6a7b8

URN Equivalence​

URN equivalence within the 'stalwart' namespace follows the rules defined in RFC 8141, with the addition that string comparison of the Namespace Specific String (NSS) is case-insensitive.

This means:

  • urn:stalwart:jmap:MailFilter and urn:stalwart:jmap:mailfilter are equivalent
  • urn:stalwart:davlock:A1B2C3D4E5F6A7B8C9D0E1F2A3B4C5D6 and urn:stalwart:davlock:a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6 are equivalent

Assignment​

URNs in the 'stalwart' namespace are assigned by Stalwart Labs LLC. Assignment follows these guidelines:

  • JMAP Extensions (jmap):

    • Assigned based on the functionality provided by the extension
    • Names follow a convention similar to standard JMAP capabilities
    • Names should be concise, descriptive, and use lowercase letters and hyphens

  • WebDAV Lock Tokens (davlock):

    • Generated as random 128-bit numbers
    • Encoded as 32 character hexadecimal strings
    • Generated on demand when locks are created

  • WebDAV Synchronization Tokens (davsync):

    • Generated as 64-bit numbers
    • Encoded as 16 character hexadecimal strings
    • Generated when a resource changes to indicate its current version

Security and Privacy Considerations​

  • WebDAV lock tokens should be treated as private information, although they do not grant exclusive access to resources.
  • When WebDAV sync tokens or lock tokens are used across networks, they should be transmitted using secure protocols to prevent unauthorized interception.
  • JMAP extension identifiers may reveal information about specific server capabilities, which could be useful to potential attackers in fingerprinting server installations.

Usage Policy​

Use of the 'stalwart' URN namespace within the scope of projects related to or derived from the Stalwart Mail and Collaboration Server is permitted according to the terms of the server's license.

Version History​

  • Version 1 (2025-03-23): Initial definition with jmap, davlock, and davsync resource types.

Contact Information​

For questions or concerns regarding the 'stalwart' URN namespace, please contact: