WIMSE / OAuth Working Group R. K. Durga Internet-Draft Microsoft Corporation Intended status: Standards Track 2 November 2026 Expires: 6 May 2027 Transitive CLEAR Revocation and Composite Physical-Safety Windows for Multi-Hop Autonomous Agent DAGs draft-durga-agent-clear-revocation-00 Abstract When an orchestrator agent delegates sub-tasks across a multi-hop Directed Acyclic Graph (DAG) of specialist agents, OAuth 2.0 Token Revocation (RFC 7009) revokes only individual client tokens and provides no mechanism to atomically halt in-flight child, grandchild, or sibling branches or enforce composite time-to-live windows across the entire execution tree. Furthermore, no protocol binds IEC 62443 / Purdue Enterprise Reference Architecture (PERA) zone boundaries into agent capability receipts. This document specifies the Transitive CLEAR (Cryptographic Lease Early-Abort & Revocation) DAG protocol and hard Operational Technology (OT) Level 0-2 physical- safety firewalling. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 6 May 2027. Copyright Notice Copyright (c) 2026 IETF Trust and the persons identified as the document authors. All rights reserved. Durga Expires 6 May 2027 [Page 1] Internet-Draft Transitive CLEAR DAG Revocation & OT Fir November 2026 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction and Problem Statement . . . . . . . . . . . . . 2 2. Conventions and Definitions . . . . . . . . . . . . . . . . . 2 3. Transitive CLEAR Token and OT Zone Firewall Profile . . . . . 3 4. Normative Fail-Closed Verification Rules . . . . . . . . . . 3 5. Strict Parser Determinism and Wire-Level Input Hardening . . 4 6. Implementation Status and Empirical Benchmark Evaluation . . 4 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 9. Normative References . . . . . . . . . . . . . . . . . . . . 6 10. Informative References . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction and Problem Statement In multi-agent workflows, revoking a parent agent's token leaves already-spawned downstream sub-agents free to execute stale tool calls against enterprise or industrial infrastructure. Existing delegation specs lack a transitive DAG epoch heartbeat and a cryptographic Purdue-zone firewall bit that unconditionally blocks autonomous writes to Level 0, Level 1, and Level 2 Programmable Logic Controllers (PLCs) and Safety Instrumented Systems (SIS). This specification complements the foundational execution-trace verification architecture defined in draft-durga-agenttrust-trace- verification-00 by introducing deterministic, fail-closed wire semantics specifically addressing Transitive CLEAR DAG Revocation & OT Firewall. 2. Conventions and Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 ([RFC2119] [RFC8174]) when, and only when, they appear in all capitals, as shown here. Durga Expires 6 May 2027 [Page 2] Internet-Draft Transitive CLEAR DAG Revocation & OT Fir November 2026 3. Transitive CLEAR Token and OT Zone Firewall Profile Every node in a multi-hop agent execution DAG MUST carry and verify a signed CLEAR DAG Envelope prior to executing any downstream tool call: { "clear_version": "1.0", "dag_root_id": "urn:uuid:9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d", "hop_index": 3, "parent_node_hash": "sha256:4b227777d4dd1fc61c6f884f48641d02b4d121d3fd328cb08b5531fcacdabf8a", "composite_window_start_ms": 1793404800000, "composite_window_end_ms": 1793404805000, "clear_revocation_epoch": 19, "effect_class": "ACTUATE_ADVISORY", "target_purdue_zone": "PERA_LEVEL_3_MES", "sis_hardware_interlock_present": false, "signature": { "alg": "Ed25519", "kid": "sha256:b600306cfa76723fdec395e53a9b3d9fdb78b1e2d7a23c32fcbcd2dc6d0c4092", "sig": "Ns1GRnHE2CtxrTdUqpjcxTq1Wpn_1VEx-zuUNz63I9hzBkJoruECGHT4sRFyLQfkX9meQ7BfxkjhlQ08wY0uDQ" } } 4. Normative Fail-Closed Verification Rules Conforming verifiers and relying-party gateways MUST enforce the following deterministic invariants before releasing any downstream side effect: 1. TRANSITIVE_ANCESTOR_REVOCATION: If any ancestor node in dag_root_id broadcasts a signed CLEAR abort frame or increments clear_revocation_epoch, all descendant nodes MUST immediately abort pending tool calls and release held resource leases within one heartbeat interval. 2. COMPOSITE_WINDOW_CONTAINMENT: At every hop i, the child execution window [start_i, end_i] MUST be a strict subset of its parent's window [start_{i-1}, end_{i-1}], and execution MUST fail closed if current_time > composite_window_end_ms. 3. OT_PURDUE_L0_L2_FIREWALL: Any agent invocation targeting target_purdue_zone in {PERA_LEVEL_0_PROCESS, PERA_LEVEL_1_BASIC_CONTROL, PERA_LEVEL_2_SUPERVISORY} with effect_class != READ_ONLY MUST be unconditionally rejected by the protocol gateway. Durga Expires 6 May 2027 [Page 3] Internet-Draft Transitive CLEAR DAG Revocation & OT Fir November 2026 5. Strict Parser Determinism and Wire-Level Input Hardening In multi-hop industrial and enterprise agent DAGs, a single permissive parser on an intermediate hop can allow a revoked or expired branch to actuate downstream systems. Conforming CLEAR DAG verifiers and OT zone gateways MUST enforce five pre-canonicalization parser invariants: 1. DUPLICATE_KEY_REJECTION: The JSON parser MUST reject any CLEAR envelope containing duplicate keys (such as duplicate target_purdue_zone or effect_class fields) at parse time before policy evaluation. 2. IEEE754_FINITE_SAFE_INTEGER_BOUNDS: All epoch and window fields (hop_index, composite_window_start_ms, composite_window_end_ms, clear_revocation_epoch) MUST be exact JSON integers within [0, 2^53 - 1]. Boolean types, string-coerced integers, and non- finite IEEE-754 floats (NaN, Infinity, 1e1000) MUST fail closed. 3. CYCLE_SAFE_TRANSITIVE_DAG_VERIFICATION: Verifiers MUST track visited node digests along the parent_node_hash chain and immediately reject any cyclic graph or hop depth exceeding the policy maximum. 4. CANONICAL_HEX_AND_BASE64URL_ENFORCEMENT: parent_node_hash and kid MUST match ^sha256:[0-9a-f]{64}$, and sig MUST be canonical unpadded Base64url with zero non-zero trailing pad bits. 5. EVIDENCE_TO_RULE_BYTE_BINDING: When a multi-hop CLEAR receipt chain is evaluated inside an external Verdict Record ([I-D.wright-verdict-record]), the rule checker MUST extract composite_window_end_ms, target_purdue_zone, and parent_node_hash directly from the digest-verified hop receipt bytes rather than trusting copied summary fields in the Verdict Record body. 6. Implementation Status and Empirical Benchmark Evaluation The transitive CLEAR DAG revocation protocol and Purdue Level 0-2 physical-safety firewall specified in this document have been implemented and benchmarked across open-source governance suites: * Open-Source Delegation & Kill-Switch Verifiers: Multi-hop delegation link verification, kill-switch signature validation, and scope-attenuation assertions are implemented across agentrust- io/trace-spec, agentrust-io/cmcp, OWASP/Agent-Security-Regression- Harness, and GenAI-Security-Project/GenAI-Agent-Security- Initiative ([AGENTIC-GOV-BENCHMARKS]). Durga Expires 6 May 2027 [Page 4] Internet-Draft Transitive CLEAR DAG Revocation & OT Fir November 2026 * Core Rust Evidence Engine: Deterministic RFC 8785 JCS trace evidence reporting and monotonic confidence bounds are merged in xerj-org/xerj (engine/crates/xerj-common/src/hub_evidence.rs, [XERJ-HUB-EVIDENCE]). * Empirical Benchmark Results: Evaluated across 100 contested multi- agent trials in the OWASP ASI01-ASI10 benchmark ([OWASP-ASI-BENCHMARK-DOI]) and the companion Technical Report ([ZENODO-TR-2026-03]), cycle-safe transitive CLEAR revocation halts downstream child and grandchild branches within a single heartbeat window and achieves 0.0% unauthorized writes across Purdue Level 0-2 PLC/SIS boundaries. 7. Security Considerations All pre-image objects MUST be canonicalized using RFC 8785 JSON Canonicalization Scheme (JCS) prior to signature generation or verification under RFC 8032 Ed25519. Any clock skew exceeding 60 seconds, digest mismatch, or missing cryptographic binding MUST cause the verifier to fail closed and emit an auditable security rejection receipt. For the normative test vector in Section 3, the Ed25519 test key seed is 2a2a...2a (32 bytes of 0x2a), yielding raw 32-byte public key 197f6b23e16c8532c6abc838facd5ea789be0c76b2920334039bfa8b3d368d61 (kid = sha256:b600306cfa76723fdec395e53a9b3d9fdb78b1e2d7a23c32fcbcd2dc6d0c4092), and the full RFC 8785 JCS-canonicalized envelope (620 bytes) hashes to SHA-256 efc24ed02692c73f33560c5f91924dedb24da33dfcbd2f02eba6960d2f4119fa. This specification cross-references the companion Internet-Drafts ([I-D.durga-agenttrust-trace-verification], [I-D.durga-wimse-ctx-isolation], [I-D.durga-pquip-pqc-agentic-delegation], [I-D.durga-agent-tx-compensation-lease]), external Verdict Record evidence binding ([I-D.wright-verdict-record]), Remote Attestation ([RFC9334]), Merkle Tree domain separation ([RFC9162]), and the 100-scenario OWASP ASI01-ASI10 benchmark ([OWASP-ASI-BENCHMARK-DOI]). 8. IANA Considerations This document requests IANA registration of the media type application/agent-clear-dag+json and the registry IETF Agent Industrial Purdue Zone Identifiers (PERA_LEVEL_0_PROCESS through PERA_LEVEL_5_ENTERPRISE), alongside the following header fields: * HTTP/MCP Header Field: Agent-Clear-DAG * HTTP/MCP Header Field: Agent-OT-Zone-Assertion Durga Expires 6 May 2027 [Page 5] Internet-Draft Transitive CLEAR DAG Revocation & OT Fir November 2026 9. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, May 2017, . [RFC8785] Rundgren, A., Jordan, B., and S. Erdtman, "JSON Canonicalization Scheme (JCS)", RFC 8785, June 2020, . [RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital Signature Algorithm (EdDSA)", RFC 8032, January 2017, . 10. Informative References [RFC9162] Laurie, B., Messeri, E., and R. Stradling, "Certificate Transparency Version 2.0", RFC 9162, December 2021, . [RFC9334] Birkholz, H., Thaler, D., Richardson, M., Smith, N., and W. Pan, "Remote ATtestation procedureS (RATS) Architecture", RFC 9334, January 2023, . [I-D.durga-agenttrust-trace-verification] Durga, R. K., "Cryptographic Execution-Trace Verification, JCS Canonicalization, and Fail-Closed Delegation Chains for Autonomous AI Agents", Work in Progress, Internet- Draft, draft-durga-agenttrust-trace-verification-00, October 2026, . [I-D.durga-wimse-ctx-isolation] Durga, R. K., "Cryptographic Context Isolation and Instruction-Data Plane Separation for Autonomous Agent Tool Invocations", Work in Progress, Internet-Draft, draft-durga-wimse-ctx-isolation-00, October 2026, . [I-D.durga-pquip-pqc-agentic-delegation] Durga, R. K., "Post-Quantum Hybrid Cryptographic Delegation Chains and Merkle-Aggregated Execution Receipts Durga Expires 6 May 2027 [Page 6] Internet-Draft Transitive CLEAR DAG Revocation & OT Fir November 2026 for Autonomous AI Agents", Work in Progress, Internet- Draft, draft-durga-pquip-pqc-agentic-delegation-00, October 2026, . [I-D.durga-agent-tx-compensation-lease] Durga, R. K., "Pre-Release Transactional Compensation Leases and CAS Fencing Receipts for Autonomous Agents Over Systems of Record", Work in Progress, Internet-Draft, draft-durga-agent-tx-compensation-lease-00, November 2026, . [I-D.wright-verdict-record] Wright, D., "Verdict Records: Results on Claims that Cite Receipts as Evidence", Work in Progress, Internet-Draft, draft-wright-verdict-record-01, November 2026, . [OWASP-ASI-BENCHMARK-DOI] Durga, R. K., "OWASP ASI01-ASI10 Enterprise Agentic AI Security Regression Benchmark Dataset (N=100 Scenarios)", DOI 10.57967/hf/11352, October 2026, . [XERJ-HUB-EVIDENCE] Durga, R. K., "XERJ Common Rust Engine: Deterministic JCS TraceEvidenceReport, PinnedCitation, and Isotonic Confidence Verification", GitHub xerj-org/xerj#2857, November 2026, . [AGENTIC-GOV-BENCHMARKS] Durga, R. K., "Enterprise Agentic Governance Benchmarks and Reference Verifier Suite v1.0.0", Version 1.0.0, November 2026, . [ZENODO-TR-2026-03] Durga, R. K., "Transitive CLEAR DAG Revocation, Pre- Release Compensation Leases, and Purdue OT Firewalls for Autonomous Industrial Agents", DOI 10.5281/zenodo.23735278, October 2026, . Author's Address Durga Expires 6 May 2027 [Page 7] Internet-Draft Transitive CLEAR DAG Revocation & OT Fir November 2026 Raghuvar Karthik Durga Microsoft Corporation United States of America Email: rdurga@microsoft.com Durga Expires 6 May 2027 [Page 8]