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…, list locking, env isolation, intent-anchor wrapper, IBCT (#2496, #2497, #2504) Phase 1 (no new deps): - Cross-server sanitized_id collision detection in McpManager: warnings on connect and add_server, first-registered tool wins dispatch (MF-1, SF-6) - Tool-list snapshot locking (lock_tool_list config): tools/list_changed rejected for connected servers; lock set atomically before connect_entry to eliminate TOCTOU race (MF-2) - Per-server Stdio environment isolation (env_isolation config): spawned processes receive only BASE_ENV_VARS + server env; XDG dirs included for Linux (SF-3) - Intent-anchor wrapper for MCP tool output: per-invocation UUID nonce boundary prevents delimiter injection; [TOOL_OUTPUT:: escaped in content (MF-5) Phase 2 (hmac 0.13 + sha2 0.11): - IBCT module (crates/zeph-a2a/src/ibct.rs): HMAC-SHA256, key_id field for rotation, Vec<IbctKey> for graceful key rollover, base64-JSON X-Zeph-IBCT header, vault_ref config field for secure key storage (MF-3, MF-4) - ibct feature gate in zeph-a2a; enabled via a2a workspace feature
RC-1: replace hex string comparison in ibct.rs with constant-time
verify_signature() using Mac::verify_slice() to eliminate the
timing side-channel in HMAC verification.
RC-2: remove hardcoded trust=untrusted field from intent-anchor wrapper
format; the trust annotation was redundant and potentially misleading
since callers already control context.
RC-3: replace all .expect("connected_server_ids lock poisoned") with
.unwrap_or_else(PoisonError::into_inner) to avoid cascade panics
on RwLock poison in manager.rs.
REC-1: add tool_list_locked.remove() in add_server() error branches
for list_tools and run_probe failures, ensuring the lock is always
cleaned up on early return.
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Summary
Implements security hardening for
zeph-mcpandzeph-a2aacross three research issues.#2496 — MCP/A2A threat modeling mitigations
McpManager: duplicatesanitized_idacross servers with different trust levels logs a warning; first-registered wins deterministicallyadd_server()re-runs collision detection on dynamic server additions#2497 — SMCP lifecycle hardening
intent_anchor_wrap) applied to all MCP tool output before insertion into LLM context; nonce-based per-invocation boundary ([TOOL_OUTPUT::{uuid}::BEGIN]) prevents injection via fixed delimiters; embedded[TOOL_OUTPUT::sequences in content are escapedenv_isolation = falseby default): child processes receive onlyBASE_ENV_VARS+ declared serverenvslice; XDG dirs includedlock_tool_list = falseby default): set atomically at connect time, blocksToolRefreshEventmid-session; cleaned up on all error paths inadd_server()#2504 — AIP Invocation-Bound Capability Tokens
ibct.rsmodule inzeph-a2a(feature-gatedibct): HMAC-SHA256 signed tokens withkey_id,task_id,endpoint,expires_atverify_signature()usesMac::verify_slice()for constant-time comparisonVec<IbctKey>config supports key rotation;ibct_signing_key_vault_reffor vault-resolved secretsMcpManagerand A2A client/server wired for token attachment and verificationTest plan
--features full,a2a)cargo +nightly fmt --check✅,cargo clippy --workspace --features full,a2a -- -D warnings✅ (0 warnings)Closes
Closes #2496, #2497, #2504