fix(agent): validate mandate timestamp ordering

Reject signed mandates whose issued, expiry, and commit timestamps
are logically inconsistent. Enforce issuedAt <= commitDeadline <=
expiresAt with exact equality allowed. Add focused tests for each
invalid ordering and equality-boundary behavior.

Closes #274

Author: olu-cmd

services/agent/src/mandate.test.ts

@@ -9,6 +9,7 @@ import {
   assertBidWithinMandate,
   bidFromAppraisal,
   createSessionMandate,
+  mandateDigest,
   MandateCapError,
   MandateError,
   usdcToStroops,
@@ -91,3 +92,74 @@ test("bidFromAppraisal clamps to mandate maxBid", () => {
   assert.equal(bidValue, usdcToStroops(40));
   assert.equal(escrow, usdcToStroops(40));
 });
+
+test("verifySessionMandate rejects when issuedAt > expiresAt", () => {
+  const p = baseParams();
+  const { mandate } = createSessionMandate(p);
+  const { signature: _sig, ...payload } = mandate;
+  const tamperedPayload = { ...payload, issuedAt: payload.expiresAt + 10 };
+  const tampered = {
+    ...tamperedPayload,
+    signature: Keypair.fromSecret(p.principalSecret).sign(mandateDigest(tamperedPayload)).toString("base64"),
+  };
+  assert.throws(
+    () => verifySessionMandate(tampered, { clock: p.clock }),
+    (error: unknown) => error instanceof MandateError && /issuedAt.*expiresAt/.test((error as Error).message),
+  );
+});
+
+test("verifySessionMandate rejects when issuedAt > commitDeadline", () => {
+  const p = baseParams();
+  const { mandate } = createSessionMandate(p);
+  const { signature: _sig, ...payload } = mandate;
+  const tamperedPayload = { ...payload, commitDeadline: payload.issuedAt - 10 };
+  const tampered = {
+    ...tamperedPayload,
+    signature: Keypair.fromSecret(p.principalSecret).sign(mandateDigest(tamperedPayload)).toString("base64"),
+  };
+  assert.throws(
+    () => verifySessionMandate(tampered, { clock: p.clock }),
+    (error: unknown) => error instanceof MandateError && /issuedAt.*commitDeadline/.test((error as Error).message),
+  );
+});
+
+test("verifySessionMandate rejects when commitDeadline > expiresAt", () => {
+  const p = baseParams();
+  const { mandate } = createSessionMandate(p);
+  const { signature: _sig, ...payload } = mandate;
+  const tamperedPayload = { ...payload, commitDeadline: payload.expiresAt + 10 };
+  const tampered = {
+    ...tamperedPayload,
+    signature: Keypair.fromSecret(p.principalSecret).sign(mandateDigest(tamperedPayload)).toString("base64"),
+  };
+  assert.throws(
+    () => verifySessionMandate(tampered, { clock: p.clock }),
+    (error: unknown) => error instanceof MandateError && /commitDeadline.*expiresAt/.test((error as Error).message),
+  );
+});
+
+test("verifySessionMandate allows equality boundaries (issuedAt == commitDeadline == expiresAt)", () => {
+  const p = baseParams();
+  // Make commitDeadline equal to expiresAt at creation (already is), then tamper to set all three equal
+  const { mandate } = createSessionMandate(p);
+  const { signature: _sig, ...payload } = mandate;
+  const equalTime = payload.expiresAt;
+  const tamperedPayload = { ...payload, issuedAt: equalTime, commitDeadline: equalTime, expiresAt: equalTime };
+  const tampered = {
+    ...tamperedPayload,
+    signature: Keypair.fromSecret(p.principalSecret).sign(mandateDigest(tamperedPayload)).toString("base64"),
+  };
+  assert.doesNotThrow(() => verifySessionMandate(tampered, { clock: p.clock }));
+});
+
+test("createSessionMandate rejects timestamp ordering violations at creation", () => {
+  const p = baseParams();
+  assert.throws(
+    () => createSessionMandate({ ...p, commitDeadline: p.clock.nowSeconds() - 10 }),
+    (error: unknown) => error instanceof MandateError && /issuedAt.*commitDeadline/.test((error as Error).message),
+  );
+  assert.throws(
+    () => createSessionMandate({ ...p, commitDeadline: p.clock.nowSeconds() + 7200, ttlSeconds: 3600 }),
+    (error: unknown) => error instanceof MandateError && /commitDeadline.*expiresAt/.test((error as Error).message),
+  );
+});

services/agent/src/mandate.ts

@@ -49,6 +49,18 @@ export interface SessionMandate extends SessionMandatePayload {
 export class MandateError extends Error {}
 export class MandateCapError extends MandateError {}
 
+function validateMandateTimestampOrdering(payload: SessionMandatePayload): void {
+  if (payload.issuedAt > payload.expiresAt) {
+    throw new MandateError("issuedAt must be <= expiresAt");
+  }
+  if (payload.issuedAt > payload.commitDeadline) {
+    throw new MandateError("issuedAt must be <= commitDeadline");
+  }
+  if (payload.commitDeadline > payload.expiresAt) {
+    throw new MandateError("commitDeadline must be <= expiresAt");
+  }
+}
+
 const canonical = (value: unknown): string => {
   if (Array.isArray(value)) return `[${value.map(canonical).join(",")}]`;
   if (value && typeof value === "object") {
@@ -122,6 +134,7 @@ export function createSessionMandate(params: CreateMandateParams): {
     issuedAt: now,
     expiresAt: now + (params.ttlSeconds ?? 3600),
   };
+  validateMandateTimestampOrdering(payload);
   const sig = principal.sign(mandateDigest(payload));
   return {
     mandate: { ...payload, signature: sig.toString("base64") },
@@ -145,6 +158,8 @@ export function verifySessionMandate(
   );
   if (!ok) throw new MandateError("invalid mandate signature");
 
+  validateMandateTimestampOrdering(payload);
+
   const now = opts?.now ?? (opts?.clock ?? systemClock).nowSeconds();
   if (now > mandate.expiresAt) throw new MandateError("mandate expired");
   if (now > mandate.commitDeadline) throw new MandateError("commit deadline passed");