TASK-6e4ff870-a386-4a11-a59c-444ebc23732e: harden candidate evidence bounds

test/fleet/candidate-engine.test.mjs

@@ -1,12 +1,23 @@
 import assert from 'node:assert/strict';
+import { createHash } from 'node:crypto';
 import { mkdtempSync } from 'node:fs';
 import { tmpdir } from 'node:os';
 import { join } from 'node:path';
 import test from 'node:test';
-import { runCandidateEngine } from '../../src/checks/candidate-engine.mjs';
+import { CANDIDATE_ENGINE_LIMITS, runCandidateEngine } from '../../src/checks/candidate-engine.mjs';
+
+function engineLimits(overrides = {}) {
+  return { ...CANDIDATE_ENGINE_LIMITS, ...overrides };
+}
 
 function fixtureInput() {
-  return { directory: mkdtempSync(join(tmpdir(), 'torch-candidate-engine-')), digest: 'a'.repeat(64), bytes: 12 };
+  const bytes = Buffer.from('fixture input bytes', 'utf8');
+  return {
+    directory: mkdtempSync(join(tmpdir(), 'torch-candidate-engine-')),
+    digest: createHash('sha256').update(bytes).digest('hex'),
+    bytes,
+    byteLength: bytes.length,
+  };
 }
 
 function fixtureOptions(overrides = {}) {
@@ -14,9 +25,10 @@ function fixtureOptions(overrides = {}) {
     input: fixtureInput(),
     definition: { command: 'fixture-command', args: ['--fixed'] },
     args: ['--bounded'],
-    environment: { FIXTURE_MODE: '1', TZ: 'UTC' },
+    environment: { TZ: 'UTC' },
     artifactDirectory: mkdtempSync(join(tmpdir(), 'torch-candidate-artifacts-')),
     executor: () => ({ status: 0, stdout: 'fixture output', stderr: '' }),
+    limits: engineLimits(),
     ...overrides,
   };
 }
@@ -39,8 +51,10 @@ test('SCN-candidate-engine-pure-fixture: immutable bounded fixture execution ret
   assert.equal(observed.terminal.kind, 'exit');
   assert.deepEqual(invocation.args, ['--fixed', '--bounded']);
   assert.equal(invocation.execution.cwd, options.input.directory);
-  assert.deepEqual(invocation.execution.env, { FIXTURE_MODE: '1', TZ: 'UTC' });
+  assert.deepEqual(invocation.execution.env, { TZ: 'UTC' });
   assert.equal(Object.isFrozen(invocation.execution), true);
+  assert.equal(invocation.execution.timeout, CANDIDATE_ENGINE_LIMITS.timeoutMs);
+  assert.equal(invocation.execution.maxBuffer, CANDIDATE_ENGINE_LIMITS.maxOutputBytes);
   assert.equal(Object.hasOwn(invocation.execution, 'token'), false);
   assert.equal(Object.hasOwn(invocation.execution, 'receiptWriter'), false);
   assert.equal(Object.hasOwn(invocation.execution, 'controlPlane'), false);
@@ -49,20 +63,24 @@ test('SCN-candidate-engine-pure-fixture: immutable bounded fixture execution ret
 test('SCN-candidate-engine-limits: invalid bounded inputs, arguments, environment and artifact descriptors refuse before execution', () => {
   let executions = 0;
   const executor = () => { executions += 1; return { status: 0 }; };
-  assert.throws(() => runCandidateEngine(fixtureOptions({ executor, input: { directory: '/tmp', digest: 'bad', bytes: 1 } })),
+  assert.throws(() => runCandidateEngine(fixtureOptions({ executor, input: { directory: '/tmp', digest: 'bad', bytes: Buffer.from('x'), byteLength: 1 } })),
     { code: 'CANDIDATE_ENGINE_INPUT_INVALID' });
-  assert.throws(() => runCandidateEngine(fixtureOptions({ executor, args: ['x'.repeat(8)], limits: { maxArgBytes: 4 } })),
+  assert.throws(() => runCandidateEngine(fixtureOptions({ executor, args: ['x'.repeat(8)], limits: engineLimits({ maxArgBytes: 4 }) })),
     { code: 'CANDIDATE_ENGINE_INPUT_INVALID' });
   assert.throws(() => runCandidateEngine(fixtureOptions({ executor, environment: { bad: '1' } })),
+    { code: 'CANDIDATE_ENGINE_ENVIRONMENT_INVALID' });
+  assert.throws(() => runCandidateEngine(fixtureOptions({ executor, artifactDirectory: 'x'.repeat(5), limits: engineLimits({ maxArtifactPathBytes: 4 }) })),
     { code: 'CANDIDATE_ENGINE_INPUT_INVALID' });
-  assert.throws(() => runCandidateEngine(fixtureOptions({ executor, artifactDirectory: 'x'.repeat(5), limits: { maxArtifactPathBytes: 4 } })),
+  assert.throws(() => runCandidateEngine(fixtureOptions({ executor, limits: engineLimits({ maxInputBytes: 4 }) })),
+    { code: 'CANDIDATE_ENGINE_INPUT_INVALID' });
+  assert.throws(() => runCandidateEngine(fixtureOptions({ executor, environment: { TZ: 'UTC', LANG: 'C.UTF-8' }, limits: engineLimits({ maxEnvironmentEntries: 1 }) })),
     { code: 'CANDIDATE_ENGINE_INPUT_INVALID' });
   assert.equal(executions, 0, 'refusal must occur before a candidate executor starts');
 });
 
 test('SCN-candidate-engine-terminal-observation: overflow, including exit zero plus ENOBUFS, is raw parent evidence and never success', () => {
   const overflow = runCandidateEngine(fixtureOptions({
-    limits: { maxOutputBytes: 4 },
+    limits: engineLimits({ maxOutputBytes: 4 }),
     executor: () => ({ status: 0, error: Object.assign(new Error('overflow'), { code: 'ENOBUFS' }), stdout: 'too many bytes' }),
   }));
   assert.equal(overflow.terminal.exitStatus, 0);
@@ -88,3 +106,81 @@ test('SCN-candidate-engine-capability-boundary: registered-state and writer-shap
   assert.throws(() => runCandidateEngine(options), { code: 'CANDIDATE_ENGINE_CAPABILITY_FORBIDDEN' });
   assert.equal(executions, 0);
 });
+
+test('SCN-candidate-engine-boundary-limits: every execution bound is explicit, finite and supplied to the native-shaped executor options', () => {
+  let executions = 0;
+  const executor = () => { executions += 1; return { status: 0 }; };
+  const missingTimeout = engineLimits();
+  delete missingTimeout.timeoutMs;
+  const missingOutput = engineLimits();
+  delete missingOutput.maxOutputBytes;
+  const missingInput = engineLimits();
+  delete missingInput.maxInputBytes;
+  for (const limits of [missingTimeout, missingOutput, missingInput, engineLimits({ timeoutMs: 0 }), engineLimits({ timeoutMs: 60_001 })]) {
+    assert.throws(() => runCandidateEngine(fixtureOptions({ executor, limits })), { code: 'CANDIDATE_ENGINE_LIMIT_INVALID' });
+  }
+  assert.equal(executions, 0, 'missing or invalid bounds refuse before execution');
+
+  let execution;
+  runCandidateEngine(fixtureOptions({ executor: (_command, _args, options) => { execution = options; return { status: 0 }; } }));
+  assert.deepEqual(Object.keys(execution).sort(), ['artifactDirectory', 'cwd', 'encoding', 'env', 'killSignal', 'maxBuffer', 'stdio', 'timeout']);
+  assert.equal(execution.timeout, CANDIDATE_ENGINE_LIMITS.timeoutMs);
+  assert.equal(execution.maxBuffer, CANDIDATE_ENGINE_LIMITS.maxOutputBytes);
+});
+
+test('SCN-candidate-engine-utf8-overflow: retained output is a valid UTF-8 prefix inside the byte cap and cannot become success', () => {
+  const fourBytes = runCandidateEngine(fixtureOptions({
+    limits: engineLimits({ maxOutputBytes: 4 }),
+    executor: () => ({ status: 0, stdout: '😀😀', stderr: '' }),
+  }));
+  assert.equal(fourBytes.terminal.stdout.text, '😀');
+  assert.equal(Buffer.byteLength(fourBytes.terminal.stdout.text, 'utf8'), 4);
+  assert.equal(fourBytes.terminal.overflow, true);
+  assert.equal(fourBytes.terminal.success, false);
+
+  const threeBytes = runCandidateEngine(fixtureOptions({
+    limits: engineLimits({ maxOutputBytes: 3 }),
+    executor: () => ({ status: 0, stdout: '😀😀', stderr: '' }),
+  }));
+  assert.equal(threeBytes.terminal.stdout.text, '');
+  assert.equal(Buffer.byteLength(threeBytes.terminal.stdout.text, 'utf8') <= 3, true);
+  assert.equal(threeBytes.terminal.stdout.text.includes('\uFFFD'), false);
+  assert.equal(threeBytes.terminal.success, false);
+});
+
+test('SCN-candidate-engine-immutable-input-and-environment: only matched byte snapshots and allowlisted deterministic environment reach the executor', () => {
+  let executions = 0;
+  const executor = () => { executions += 1; return { status: 0 }; };
+  const mismatched = fixtureInput();
+  mismatched.digest = '0'.repeat(64);
+  assert.throws(() => runCandidateEngine(fixtureOptions({ executor, input: mismatched })), { code: 'CANDIDATE_ENGINE_INPUT_INVALID' });
+  assert.throws(() => runCandidateEngine(fixtureOptions({ executor, input: { directory: '/tmp', digest: '0'.repeat(64), byteLength: 0 } })),
+    { code: 'CANDIDATE_ENGINE_INPUT_INVALID' });
+  assert.throws(() => runCandidateEngine(fixtureOptions({ executor, environment: { UNREVIEWED_SECRET: '1' } })),
+    { code: 'CANDIDATE_ENGINE_ENVIRONMENT_INVALID' });
+  assert.equal(executions, 0, 'invalid snapshot or environment refuses before execution');
+
+  const input = fixtureInput();
+  const definition = { command: 'fixture-command', args: ['--fixed'] };
+  const args = ['--bounded'];
+  const environment = { TZ: 'UTC' };
+  let invocation;
+  const observed = runCandidateEngine(fixtureOptions({
+    input, definition, args, environment,
+    executor: (_command, commandArgs, execution) => {
+      input.bytes.fill(0);
+      definition.args[0] = '--mutated';
+      args[0] = '--mutated';
+      environment.TZ = 'America/New_York';
+      invocation = { commandArgs, execution };
+      return { status: 0 };
+    },
+  }));
+  assert.deepEqual(invocation.commandArgs, ['--fixed', '--bounded']);
+  assert.deepEqual(invocation.execution.env, { TZ: 'UTC' });
+  assert.deepEqual(observed.input, {
+    directory: input.directory,
+    digest: createHash('sha256').update(Buffer.from('fixture input bytes')).digest('hex'),
+    bytes: Buffer.byteLength('fixture input bytes'),
+  });
+});