feat: supply system log to trusted plugins via FD

packages/build/src/core/build.ts

@@ -204,6 +204,7 @@ const tExecBuild = async function ({
     logs,
     debug,
     systemLog,
+    systemLogFile,
     verbose,
     timers: timersA,
     sendStatus,
@@ -264,6 +265,7 @@ export const runAndReportBuild = async function ({
   logs,
   debug,
   systemLog,
+  systemLogFile,
   verbose,
   timers,
   sendStatus,
@@ -315,6 +317,7 @@ export const runAndReportBuild = async function ({
       logs,
       debug,
       systemLog,
+      systemLogFile,
       verbose,
       timers,
       sendStatus,
@@ -418,6 +421,7 @@ const initAndRunBuild = async function ({
   logs,
   debug,
   systemLog,
+  systemLogFile,
   verbose,
   sendStatus,
   saveConfig,
@@ -466,6 +470,7 @@ const initAndRunBuild = async function ({
     timers: timersA,
     featureFlags,
     quiet,
+    systemLogFile,
   })
 
   try {

packages/build/src/plugins/child/run.js

@@ -2,6 +2,7 @@ import { getNewEnvChanges, setEnvChanges } from '../../env/changes.js'
 import { logPluginMethodStart, logPluginMethodEnd } from '../../log/messages/ipc.js'
 
 import { cloneNetlifyConfig, getConfigMutations } from './diff.js'
+import { getSystemLog } from './systemLog.js'
 import { getUtils } from './utils.js'
 
 // Run a specific plugin event handler
@@ -11,9 +12,19 @@ export const run = async function (
 ) {
   const method = methods[event]
   const runState = {}
+  const systemLog = getSystemLog()
   const utils = getUtils({ event, constants, runState })
   const netlifyConfigCopy = cloneNetlifyConfig(netlifyConfig)
-  const runOptions = { utils, constants, inputs, netlifyConfig: netlifyConfigCopy, packageJson, error, featureFlags }
+  const runOptions = {
+    utils,
+    constants,
+    inputs,
+    netlifyConfig: netlifyConfigCopy,
+    packageJson,
+    error,
+    featureFlags,
+    systemLog,
+  }
 
   const envBefore = setEnvChanges(envChanges)
 

packages/build/src/plugins/child/systemLog.js

@@ -0,0 +1,15 @@
+import { appendFileSync, openSync } from 'fs'
+
+const systemLogLocation = '/dev/fd/4'
+
+export const getSystemLog = () => {
+  try {
+    // throws if system log wasn't hooked up
+    const fd = openSync(systemLogLocation, 'a')
+    return (message) => {
+      appendFileSync(fd, `${message}\n`)
+    }
+  } catch {
+    return
+  }
+}

packages/build/src/plugins/spawn.ts

@@ -10,6 +10,7 @@ import {
   logIncompatiblePlugins,
   logLoadingIntegration,
 } from '../log/messages/compatibility.js'
+import { isTrustedPlugin } from '../steps/plugin.js'
 import { measureDuration } from '../time/main.js'
 
 import { getEventFromChild } from './ipc.js'
@@ -23,7 +24,7 @@ const CHILD_MAIN_FILE = fileURLToPath(new URL('child/main.js', import.meta.url))
 //    (for both security and safety reasons)
 //  - logs can be buffered which allows manipulating them for log shipping,
 //    transforming and parallel plugins
-const tStartPlugins = async function ({ pluginsOptions, buildDir, childEnv, logs, debug, quiet }) {
+const tStartPlugins = async function ({ pluginsOptions, buildDir, childEnv, logs, debug, quiet, systemLogFile }) {
   if (!quiet) {
     logRuntime(logs, pluginsOptions)
     logLoadingPlugins(logs, pluginsOptions, debug)
@@ -34,14 +35,16 @@ const tStartPlugins = async function ({ pluginsOptions, buildDir, childEnv, logs
   logIncompatiblePlugins(logs, pluginsOptions)
 
   const childProcesses = await Promise.all(
-    pluginsOptions.map(({ pluginDir, nodePath }) => startPlugin({ pluginDir, nodePath, buildDir, childEnv })),
+    pluginsOptions.map(({ pluginDir, nodePath, pluginPackageJson }) =>
+      startPlugin({ pluginDir, nodePath, buildDir, childEnv, systemLogFile, pluginPackageJson }),
+    ),
   )
   return { childProcesses }
 }
 
 export const startPlugins = measureDuration(tStartPlugins, 'start_plugins')
 
-const startPlugin = async function ({ pluginDir, nodePath, buildDir, childEnv }) {
+const startPlugin = async function ({ pluginDir, nodePath, buildDir, childEnv, systemLogFile, pluginPackageJson }) {
   const childProcess = execaNode(CHILD_MAIN_FILE, [], {
     cwd: buildDir,
     preferLocal: true,
@@ -50,6 +53,8 @@ const startPlugin = async function ({ pluginDir, nodePath, buildDir, childEnv })
     execPath: nodePath,
     env: childEnv,
     extendEnv: false,
+    stdio:
+      isTrustedPlugin(pluginPackageJson) && systemLogFile ? ['pipe', 'pipe', 'pipe', 'ipc', systemLogFile] : undefined,
   })
 
   try {

packages/build/src/steps/plugin.js

@@ -7,6 +7,8 @@ import { getSuccessStatus } from '../status/success.js'
 import { getPluginErrorType } from './error.js'
 import { updateNetlifyConfig, listConfigSideFiles } from './update_config.js'
 
+export const isTrustedPlugin = (pluginPackageJson) => pluginPackageJson?.name?.startsWith('@netlify/')
+
 // Fire a plugin step
 export const firePluginStep = async function ({
   event,
@@ -33,8 +35,6 @@ export const firePluginStep = async function ({
 }) {
   const listeners = pipePluginOutput(childProcess, logs)
 
-  const isTrustedPlugin = pluginPackageJson?.name?.startsWith('@netlify/')
-
   try {
     const configSideFiles = await listConfigSideFiles([headersPath, redirectsPath])
     const {
@@ -48,7 +48,7 @@ export const firePluginStep = async function ({
         event,
         error,
         envChanges,
-        featureFlags: isTrustedPlugin ? featureFlags : undefined,
+        featureFlags: isTrustedPlugin(pluginPackageJson) ? featureFlags : undefined,
         netlifyConfig,
         constants,
       },

packages/build/tests/plugins/fixtures/feature_flags/plugin.js

@@ -1,3 +1,4 @@
-export const onBuild = function ({ featureFlags }) {
+export const onBuild = function ({ featureFlags, systemLog }) {
+  systemLog("some system-facing logs")
   console.log(JSON.stringify(featureFlags))
 }

packages/build/tests/plugins/fixtures/feature_flags_untrusted/plugin.js

@@ -1,3 +1,6 @@
-export const onBuild = function ({ featureFlags }) {
+export const onBuild = function ({ featureFlags, systemLog }) {
+  if (systemLog) {
+    throw new Error("System log shouldn't be acessible from untrusted plugins")
+  }
   console.log("typeof featureflags:", typeof featureFlags)
 }

packages/build/tests/plugins/tests.js

@@ -1,7 +1,9 @@
+import * as fs from 'fs/promises'
 import { fileURLToPath } from 'url'
 
 import { Fixture, normalizeOutput, removeDir } from '@netlify/testing'
 import test from 'ava'
+import { tmpName } from 'tmp-promise'
 
 const FIXTURES_DIR = fileURLToPath(new URL('fixtures', import.meta.url))
 
@@ -142,13 +144,22 @@ test('Plugins can have inputs', async (t) => {
   t.snapshot(normalizeOutput(output))
 })
 
-test('Plugins are passed featureflags', async (t) => {
+test('Trusted plugins are passed featureflags and system log', async (t) => {
+  const systemLogFile = await tmpName()
   const output = await new Fixture('./fixtures/feature_flags')
     .withFlags({
       featureFlags: { test_flag: true },
+      debug: false,
+      systemLogFile: await fs.open(systemLogFile, 'a'),
     })
     .runWithBuild()
 
+  const systemLog = (await fs.readFile(systemLogFile, { encoding: 'utf8' })).split('\n')
+
+  const expectedSystemLogs = 'some system-facing logs'
+  t.false(output.includes(expectedSystemLogs))
+  t.true(systemLog.includes(expectedSystemLogs))
+
   t.true(
     output.includes(
       JSON.stringify({
@@ -165,6 +176,8 @@ test('Plugins are passed featureflags', async (t) => {
   const outputUntrusted = await new Fixture('./fixtures/feature_flags_untrusted')
     .withFlags({
       featureFlags: { test_flag: true },
+      debug: false,
+      systemLogFile: await fs.open(systemLogFile, 'a'),
     })
     .runWithBuild()
 

packages/build/types/netlify_plugin_options.d.ts

@@ -21,4 +21,5 @@ export interface NetlifyPluginOptions<TInputs extends PluginInputs<StringKeys<TI
   constants: NetlifyPluginConstants
   utils: NetlifyPluginUtils
   featureFlags?: Record<string, unknown>
+  systemLog?(message: string): void
 }