tegwick
947ad50252
- The operator's Vergabe recipient journey completed after the KeyCape fresh-login fix: sign-in, callback and account confirmation. - ADR-0016 records MFA as user preference by default, workload-requested step-up for all or part of a feature set, and an unchanged IAM v0.3 floor. - NK-WP-0042 (proposed) plans the step-up contract and user journey. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Assistant: claude-code Assistant-Model: opus Assistant-Process: 299762@bnt-lap001 Assistant-Session: d3d3cea1-869c-44f1-be2a-3d6d3550e72e
75 lines
3.3 KiB
Markdown
75 lines
3.3 KiB
Markdown
---
|
|
id: NK-ADR-0016
|
|
type: architecture-decision-record
|
|
title: "MFA Is a User Preference by Default; Workloads Opt In to Requiring It"
|
|
status: accepted
|
|
owner: net-kingdom
|
|
revision: "1"
|
|
decided: "2026-09-23"
|
|
last_reviewed: "2026-09-23"
|
|
review_interval: 12m
|
|
---
|
|
|
|
# ADR-0016 - MFA Is a User Preference by Default; Workloads Opt In to Requiring It
|
|
|
|
**Status:** Accepted
|
|
**Date:** 2026-09-23
|
|
**Deciders:** Bernd Worsch, Claude
|
|
|
|
## Context
|
|
|
|
The attended Vergabe recipient journey on 2026-09-23 (NK-WP-0036-T05,
|
|
NK-WP-0037-T02) completed sign-in and account confirmation without MFA.
|
|
KeyCape policy P06 (`key-cape/docs/optional-mfa.md`, deployed 2026-09-14 for
|
|
`vergabe-demo-company` and `user-engine-portal`) allowed this. Under P06, AAL1
|
|
is permitted when privacyIDEA authoritatively reports no active factor, and
|
|
AAL2 is required once one exists.
|
|
|
|
NK-WP-0037 had been written on 2026-09-12 as "provider-required MFA". The
|
|
operator decided against requiring MFA for Vergabe Teilnahme now. The
|
|
enrollment and recovery journeys (user-engine U06, factor recovery) have not
|
|
yet been accepted from a user's perspective, and requiring MFA before they
|
|
work pushes users into support paths.
|
|
|
|
## Decision
|
|
|
|
1. **Default: MFA is the user's preference.** For ordinary human sign-in to a
|
|
workload, MFA is offered but not required. A user who activates a factor
|
|
is held to it: later sign-ins require AAL2, and a prior AAL1 session does
|
|
not satisfy it (P06 semantics).
|
|
2. **Workloads opt in to requiring MFA,** for all of their features or for
|
|
some of them. A workload states the requirement explicitly, either per
|
|
client registration or per request as a step-up (an explicit AAL2 request
|
|
at the moment a protected feature is used). An explicit workload
|
|
requirement always wins over a user's preference. Authorization decisions
|
|
read it from the normalized `assurance.level` claim (IAM Profile v0.3),
|
|
never from a provider-native claim.
|
|
3. **The IAM Profile v0.3 floor is unchanged.** Privileged, destructive,
|
|
platform-root, secret, credential-vending and emergency flows require AAL2
|
|
or stronger, and administration requires MFA even where ordinary sign-in
|
|
does not. This ADR relaxes nothing below that floor.
|
|
4. **Usability comes before a mandatory requirement.** The enrollment,
|
|
re-enrollment and recovery journeys must be accepted from a user's
|
|
perspective before any workload's default sign-in is switched to
|
|
required MFA.
|
|
|
|
## Consequences
|
|
|
|
- Vergabe Teilnahme keeps P06 optional MFA. NK-WP-0037's "provider-required
|
|
MFA" wording is superseded.
|
|
- A workload that needs MFA for part of its feature set needs a step-up path:
|
|
it requests AAL2 when a protected feature is used, and KeyCape answers with
|
|
an MFA challenge that its existing session cannot bypass. The KeyCape and
|
|
application contract for that step-up is follow-up work (NK-WP-0042,
|
|
proposed).
|
|
- The user-engine enrollment journey (U06) and factor recovery are
|
|
prerequisites for any workload making MFA mandatory by default.
|
|
- A per-client `mfaRequired: false` remains unconditional AAL1 and is not a
|
|
preference mechanism. Use P06 `mfaOptional` for preference-based clients.
|
|
|
|
## Related
|
|
|
|
- IAM Profile v0.3 (Human Interactive Flow; Assurance Evidence)
|
|
- `key-cape/docs/optional-mfa.md` (P06)
|
|
- NK-WP-0036, NK-WP-0037, NK-WP-0041
|
|
- user-engine account journeys U06 (voluntary authenticator activation)
|