feat(eval): end-to-end metered evaluator

package.json

@@ -15,6 +15,7 @@
     "packages/acorn-eventual-send",
     "packages/eventual-send",
     "packages/transform-eventual-send",
+    "packages/tame-metering",
     "packages/transform-metering",
     "packages/default-evaluate-options",
     "packages/evaluate",

packages/transform-metering/README.md

@@ -4,6 +4,40 @@ The purpose of this package is to provide a loose, but deterministic way to inte
 
 This technique is not airtight, but it is at least is a best approximation in the absence of an instrumented host platform.
 
+## Quickstart
+
+```js
+import SES from 'ses';
+import * as babelCore from '@babel/core';
+import { makeMeteredEvaluator } from '@agoric/transform-metering';
+import tameMetering from '@agoric/tame-metering';
+
+// Override all the global objects with metered versions.
+const setGlobalMeter = tameMetering();
+
+const meteredEval = makeMeteredEvaluator({
+  // Needed for enabling metering of the global builtins.
+  setGlobalMeter,
+  // Needed for source transforms that prevent runaways.
+  babelCore,
+  // ({ transforms }) => { evaluate(src, endowments = {}) { [eval function] } }
+  makeEvaluator: SES.makeSESRootRealm, // TODO: change to new SES/Compartment API
+});
+
+// Now use the returned meteredEval: it should not throw.
+const { exhausted, exceptionBox, returned } = meteredEval(untrustedSource, /* endowments */);
+if (exhausted) {
+  console.log('the meter was exhausted');
+}
+if (exceptionBox) {
+  console.log('the source threw exception', exceptionBox[0]);
+} else {
+  console.log('the source returned', returned);
+}
+```
+
+# Implementation Details
+
 ## Meter types
 
 There are three types of meters:

packages/transform-metering/package.json

@@ -24,6 +24,7 @@
   "dependencies": {
     "@agoric/harden": "^0.0.4",
     "@agoric/nat": "^2.0.1",
+    "@agoric/tame-metering": "^1.0.0",
     "re2": "^1.10.5"
   },
   "keywords": [],

packages/transform-metering/src/constants.js

@@ -1,8 +1,5 @@
 // These are the meter members of the meterId.
-export const METER_ALLOCATE = 'a';
-export const METER_COMPUTE = 'c';
-export const METER_ENTER = 'e';
-export const METER_LEAVE = 'l';
+export * from '@agoric/tame-metering/src/constants';
 export const METER_COMBINED = '*';
 
 export const DEFAULT_METER_ID = '$h\u200d_meter';

packages/transform-metering/src/evaluator.js

@@ -0,0 +1,39 @@
+import { makeWithMeter } from './with';
+import { makeMeterAndResetters } from './meter';
+import { makeMeteringTransformer } from './transform';
+
+export function makeMeteredEvaluator({
+  setGlobalMeter,
+  makeEvaluator,
+  babelCore,
+  maxima,
+}) {
+  const [meter, reset] = makeMeterAndResetters(maxima);
+  const { meterId, meteringTransform } = makeMeteringTransformer(babelCore);
+  const transforms = [meteringTransform];
+  const { withMeter } = makeWithMeter(setGlobalMeter, meter);
+
+  const ev = makeEvaluator({ transforms });
+
+  return (src, endowments = {}) => {
+    // Reset all meters to their defaults.
+    Object.values(reset).forEach(r => r());
+    endowments[meterId] = meter;
+    let exhausted = true;
+    let returned;
+    let exceptionBox = false;
+    try {
+      // Evaluate the source with the meter.
+      returned = withMeter(() => ev.evaluate(src, { [meterId]: meter }));
+      exhausted = false;
+    } catch (e) {
+      exceptionBox = [e];
+      exhausted = reset.isExhausted();
+    }
+    return {
+      exhausted,
+      returned,
+      exceptionBox,
+    };
+  };
+}

packages/transform-metering/src/index.js

@@ -1,3 +1,4 @@
+export { makeMeteredEvaluator } from './evaluator';
 export { makeMeter, makeMeterAndResetters } from './meter';
-export { makeMeteringEndowments } from './endow';
 export { makeMeteringTransformer } from './transform';
+export { makeWithMeter } from './with';

packages/transform-metering/src/meter.js

@@ -5,6 +5,8 @@ import * as c from './constants';
 
 const { isArray } = Array;
 const { getOwnPropertyDescriptors } = Object;
+const { ceil } = Math;
+const ObjectConstructor = Object;
 
 // eslint-disable-next-line no-bitwise
 const bigIntWord = typeof BigInt !== 'undefined' && BigInt(1 << 32);
@@ -64,7 +66,7 @@ export function makeAllocateMeter(maybeAbort, meter, allocateCounter = null) {
       meter[c.METER_ENTER]();
       maybeAbort();
       let cost = 1;
-      if (value && Object(value) === value) {
+      if (value && ObjectConstructor(value) === value) {
         // Either an array or an object with properties.
         if (isArray(value)) {
           // The size of the array.  This property cannot be overridden.
@@ -83,7 +85,7 @@ export function makeAllocateMeter(maybeAbort, meter, allocateCounter = null) {
         switch (t) {
           case 'string':
             // The size of the string, in approximate words.
-            cost += Math.ceil(value.length / 4);
+            cost += ceil(value.length / 4);
             break;
           case 'bigint': {
             // Compute the number of words in the bigint.
@@ -183,6 +185,14 @@ export function makeMeterAndResetters(maxima = {}) {
     }
   };
   const resetters = {
+    isExhausted() {
+      try {
+        maybeAbort();
+        return undefined;
+      } catch (e) {
+        return e;
+      }
+    },
     allocate: makeResetter(allocateCounter),
     stack: makeResetter(stackCounter),
     compute: makeResetter(computeCounter),

packages/transform-metering/src/transform.js

@@ -1,18 +1,26 @@
+import harden from '@agoric/harden';
+
 import * as c from './constants';
 
+// We'd like to import this, but RE2 is cjs
+const RE2 = require('re2');
+
 const METER_GENERATED = Symbol('meter-generated');
 
 export function makeMeteringTransformer(
   babelCore,
-  overrideParser = undefined,
-  overrideMeterId = c.DEFAULT_METER_ID,
-  overrideRegexpIdPrefix = c.DEFAULT_REGEXP_ID_PREFIX,
+  {
+    overrideParser = undefined,
+    overrideRegExp = harden(RE2),
+    overrideMeterId = c.DEFAULT_METER_ID,
+    overrideRegExpIdPrefix = c.DEFAULT_REGEXP_ID_PREFIX,
+  } = {},
 ) {
   const parser = overrideParser
     ? overrideParser.parse || overrideParser
     : babelCore.parseSync;
   const meterId = overrideMeterId;
-  const regexpIdPrefix = overrideRegexpIdPrefix;
+  const regexpIdPrefix = overrideRegExpIdPrefix;
   let regexpNumber = 0;
 
   const meteringPlugin = regexpList => ({ types: t }) => {
@@ -167,10 +175,17 @@ const ${reid}=RegExp(${JSON.stringify(pattern)},${JSON.stringify(flags)});`);
           ? `(function(){${reSource}return ${maybeSource}})()`
           : `${reSource}${maybeSource}`;
 
+      if (overrideRegExp) {
+        // By default, override with RE2, which protects against
+        // catastrophic backtracking.
+        endowments.RegExp = overrideRegExp;
+      }
+
       // console.log('metered source:', actualSource);
       return {
         ...ss,
         ast,
+        endowments,
         src: actualSource,
       };
     },

packages/transform-metering/src/with.js

@@ -0,0 +1,13 @@
+export function makeWithMeter(setGlobalMeter, defaultMeter = null) {
+  const withMeter = (thunk, newMeter = defaultMeter) => {
+    let oldMeter;
+    try {
+      oldMeter = setGlobalMeter(newMeter);
+      return thunk();
+    } finally {
+      setGlobalMeter(oldMeter);
+    }
+  };
+  const withoutMeter = thunk => withMeter(thunk, null);
+  return { withMeter, withoutMeter };
+}