fix(gatsby-plugin-mdx): don't allow JS frontmatter by default (#35830)

e2e-tests/mdx-less-babel/.gitignore

@@ -9,3 +9,4 @@ yarn-error.log
 
 # Cypress output
 cypress/videos/
+cypress/screenshots/

e2e-tests/mdx-less-babel/cypress/fixtures/file-to-attempt-rce-on.txt

@@ -0,0 +1 @@
+Nothing here, do not remove

e2e-tests/mdx-less-babel/cypress/integration/js-frontmatter.js

@@ -0,0 +1,29 @@
+describe(`webpack loader`, () => {
+  it(`---js frontmatter should not parse by default`, () => {
+    cy.visit(`/js-frontmatter`).waitForRouteChange()
+
+    // Check frontmatter not parsed in page context
+    cy.get(`[data-cy="js-frontmatter"]`).invoke(`text`).should(`eq`, `disabled`)
+  })
+
+  it(`---javascript frontmatter should not parse by default`, () => {
+    cy.visit(`/javascript-frontmatter`).waitForRouteChange()
+
+    // Check frontmatter not parsed in page context
+    cy.get(`[data-cy="js-frontmatter"]`).invoke(`text`).should(`eq`, `disabled`)
+  })
+})
+
+describe(`data layer`, () => {
+  it(`---js or ---javascript frontmatter should not parse by default`, () => {
+    cy.visit(`/mdx-query-js-frontmatter/`).waitForRouteChange()
+    cy.contains(`I should not be parsed`).should("not.exist")
+  })
+})
+
+it(`---js and ---javascript frontmatter should not allow remote code execution`, () => {
+  cy.readFile(`cypress/fixtures/file-to-attempt-rce-on.txt`).should(
+    `eq`,
+    `Nothing here, do not remove`
+  )
+})

e2e-tests/mdx-less-babel/gatsby-node.js

@@ -0,0 +1,12 @@
+exports.createSchemaCustomization = ({ actions }) => {
+  const { createTypes } = actions
+
+  createTypes(`
+    type Mdx implements Node {
+      frontmatter: Frontmatter
+    }
+    type Frontmatter {
+      title: String
+    }
+  `)
+}

e2e-tests/mdx-less-babel/package.json

@@ -6,9 +6,9 @@
     "@mdx-js/mdx": "^1.6.6",
     "@mdx-js/react": "^1.6.6",
     "cypress": "^3.1.0",
-    "gatsby": "^2.0.118",
-    "gatsby-plugin-mdx": "^1.2.19",
-    "gatsby-source-filesystem": "^2.3.14",
+    "gatsby": "^3.0.0",
+    "gatsby-plugin-mdx": "^2.0.0",
+    "gatsby-source-filesystem": "^3.0.0",
     "react": "^16.9.0",
     "react-dom": "^16.9.0",
     "theme-ui": "^0.3.1"
@@ -18,10 +18,11 @@
   ],
   "license": "MIT",
   "scripts": {
-    "build": "gatsby build",
-    "develop": "gatsby develop",
+    "clean": "gatsby clean",
+    "build": "cross-env CYPRESS_SUPPORT=y gatsby build",
+    "develop": "cross-env CYPRESS_SUPPORT=y gatsby develop",
     "format": "prettier --write '**/*.js'",
-    "test": "cross-env CYPRESS_SUPPORT=y npm run build && npm run start-server-and-test",
+    "test": "npm run build && npm run start-server-and-test",
     "start-server-and-test": "start-server-and-test serve http://localhost:9000 cy:run",
     "serve": "gatsby serve",
     "cy:open": "cypress open",
@@ -34,4 +35,4 @@
     "prettier": "2.0.4",
     "start-server-and-test": "^1.7.1"
   }
-}
+}

e2e-tests/mdx-less-babel/src/pages/javascript-frontmatter.mdx

@@ -0,0 +1,16 @@
+---javascript
+(() => {
+require(`fs`).writeFileSync(`${process.cwd()}/cypress/fixtures/file-to-attempt-rce-on.txt`, (new Error('Helpful stack trace if this does execute. It should not execute.')).stack)
+console.trace()
+return {
+title: `I should not be parsed`
+}
+})()
+
+---
+
+<h1>JS frontmatter engine is disabled by default</h1>
+
+<span data-cy="js-frontmatter">
+  {props.pageContext.frontmatter?.title || `disabled`}
+</span>

e2e-tests/mdx-less-babel/src/pages/js-frontmatter.mdx

@@ -0,0 +1,16 @@
+---js
+(() => {
+require(`fs`).writeFileSync(`${process.cwd()}/cypress/fixtures/file-to-attempt-rce-on.txt`, (new Error('Helpful stack trace if this does execute. It should not execute.')).stack)
+console.trace()
+return {
+title: `I should not be parsed`
+}
+})()
+
+---
+
+<h1>JS frontmatter engine is disabled by default</h1>
+
+<span data-cy="js-frontmatter">
+  {props.pageContext.frontmatter?.title || `disabled`}
+</span>

e2e-tests/mdx-less-babel/src/pages/mdx-query-js-frontmatter.js

@@ -0,0 +1,30 @@
+import React from "react"
+import { graphql } from "gatsby"
+
+export default function PageRunningGraphqlResolversOnJSFrontmatterTestInputs({
+  data,
+}) {
+  return <pre>{JSON.stringify(data.allMdx.nodes, null, 2)}</pre>
+}
+
+export const query = graphql`
+  {
+    allMdx(filter: { slug: { glob: "frontmatter-engine/*" } }) {
+      nodes {
+        frontmatter {
+          title
+        }
+        body
+        excerpt
+        tableOfContents
+        timeToRead
+        wordCount {
+          paragraphs
+          sentences
+          words
+        }
+        mdxAST
+      }
+    }
+  }
+`

e2e-tests/mdx-less-babel/src/posts/frontmatter-engine/javascript-frontmatter.mdx

@@ -0,0 +1,16 @@
+---javascript
+(() => {
+require(`fs`).writeFileSync(`${process.cwd()}/cypress/fixtures/file-to-attempt-rce-on.txt`, (new Error('Helpful stack trace if this does execute. It should not execute.')).stack)
+console.trace()
+return {
+title: `I should not be parsed`
+}
+})()
+
+---
+
+<h1>JS frontmatter engine is disabled by default w</h1>
+
+<span data-cy="js-frontmatter">
+  {props.pageContext.frontmatter?.title || `disabled`}
+</span>

e2e-tests/mdx-less-babel/src/posts/frontmatter-engine/js-frontmatter.mdx

@@ -0,0 +1,16 @@
+---js
+(() => {
+require(`fs`).writeFileSync(`${process.cwd()}/cypress/fixtures/file-to-attempt-rce-on.txt`, (new Error('Helpful stack trace if this does execute. It should not execute.')).stack)
+console.trace()
+return {
+title: `I should not be parsed`
+}
+})()
+
+---
+
+<h1>JS frontmatter engine is disabled by default</h1>
+
+<span data-cy="js-frontmatter">
+  {props.pageContext.frontmatter?.title || `disabled`}
+</span>

e2e-tests/mdx/.gitignore

@@ -9,3 +9,4 @@ yarn-error.log
 
 # Cypress output
 cypress/videos/
+cypress/screenshots/

e2e-tests/mdx/cypress/fixtures/file-to-attempt-rce-on.txt

@@ -0,0 +1 @@
+Nothing here, do not remove

e2e-tests/mdx/cypress/integration/js-frontmatter.js

@@ -0,0 +1,29 @@
+describe(`webpack loader`, () => {
+  it(`---js frontmatter should not parse by default`, () => {
+    cy.visit(`/js-frontmatter`).waitForRouteChange()
+
+    // Check frontmatter not parsed in page context
+    cy.get(`[data-cy="js-frontmatter"]`).invoke(`text`).should(`eq`, `disabled`)
+  })
+
+  it(`---javascript frontmatter should not parse by default`, () => {
+    cy.visit(`/javascript-frontmatter`).waitForRouteChange()
+
+    // Check frontmatter not parsed in page context
+    cy.get(`[data-cy="js-frontmatter"]`).invoke(`text`).should(`eq`, `disabled`)
+  })
+})
+
+describe(`data layer`, () => {
+  it(`---js or ---javascript frontmatter should not parse by default`, () => {
+    cy.visit(`/mdx-query-js-frontmatter/`).waitForRouteChange()
+    cy.contains(`I should not be parsed`).should("not.exist")
+  })
+})
+
+it(`---js and ---javascript frontmatter should not allow remote code execution`, () => {
+  cy.readFile(`cypress/fixtures/file-to-attempt-rce-on.txt`).should(
+    `eq`,
+    `Nothing here, do not remove`
+  )
+})

e2e-tests/mdx/gatsby-config.js

@@ -37,7 +37,7 @@ module.exports = {
  * See #26914 for more info.
  */
 function remarkRequireFilePathPlugin() {
-  return function transformer(tree, file) {
+  return function transformer(_, file) {
     if (!file.dirname) {
       throw new Error("No directory name for this markdown file!")
     }

e2e-tests/mdx/gatsby-node.js

@@ -16,3 +16,16 @@ exports.onPostBuild = async ({ graphql }) => {
     { spaces: 2 }
   )
 }
+
+exports.createSchemaCustomization = ({ actions }) => {
+  const { createTypes } = actions
+
+  createTypes(`
+    type Mdx implements Node {
+      frontmatter: Frontmatter
+    }
+    type Frontmatter {
+      title: String
+    }
+  `)
+}

e2e-tests/mdx/package.json

@@ -19,6 +19,7 @@
   ],
   "license": "MIT",
   "scripts": {
+    "clean": "gatsby clean",
     "build": "cross-env CYPRESS_SUPPORT=y gatsby build",
     "develop": "cross-env CYPRESS_SUPPORT=y gatsby develop",
     "format": "prettier --write '**/*.js'",

e2e-tests/mdx/src/pages/javascript-frontmatter.mdx

@@ -0,0 +1,16 @@
+---javascript
+(() => {
+require(`fs`).writeFileSync(`${process.cwd()}/cypress/fixtures/file-to-attempt-rce-on.txt`, (new Error('Helpful stack trace if this does execute. It should not execute.')).stack)
+console.trace()
+return {
+title: `I should not be parsed`
+}
+})()
+
+---
+
+<h1>JS frontmatter engine is disabled by default</h1>
+
+<span data-cy="js-frontmatter">
+  {props.pageContext.frontmatter?.title || `disabled`}
+</span>

e2e-tests/mdx/src/pages/js-frontmatter.mdx

@@ -0,0 +1,16 @@
+---js
+(() => {
+require(`fs`).writeFileSync(`${process.cwd()}/cypress/fixtures/file-to-attempt-rce-on.txt`, (new Error('Helpful stack trace if this does execute. It should not execute.')).stack)
+console.trace()
+return {
+title: `I should not be parsed`
+}
+})()
+
+---
+
+<h1>JS frontmatter engine is disabled by default</h1>
+
+<span data-cy="js-frontmatter">
+  {props.pageContext.frontmatter?.title || `disabled`}
+</span>

e2e-tests/mdx/src/pages/mdx-query-js-frontmatter.js

@@ -0,0 +1,30 @@
+import React from "react"
+import { graphql } from "gatsby"
+
+export default function PageRunningGraphqlResolversOnJSFrontmatterTestInputs({
+  data,
+}) {
+  return <pre>{JSON.stringify(data.allMdx.nodes, null, 2)}</pre>
+}
+
+export const query = graphql`
+  {
+    allMdx(filter: { slug: { glob: "frontmatter-engine/*" } }) {
+      nodes {
+        frontmatter {
+          title
+        }
+        body
+        excerpt
+        tableOfContents
+        timeToRead
+        wordCount {
+          paragraphs
+          sentences
+          words
+        }
+        mdxAST
+      }
+    }
+  }
+`

e2e-tests/mdx/src/posts/frontmatter-engine/javascript-frontmatter.mdx

@@ -0,0 +1,16 @@
+---javascript
+(() => {
+require(`fs`).writeFileSync(`${process.cwd()}/cypress/fixtures/file-to-attempt-rce-on.txt`, (new Error('Helpful stack trace if this does execute. It should not execute.')).stack)
+console.trace()
+return {
+title: `I should not be parsed`
+}
+})()
+
+---
+
+<h1>JS frontmatter engine is disabled by default w</h1>
+
+<span data-cy="js-frontmatter">
+  {props.pageContext.frontmatter?.title || `disabled`}
+</span>

e2e-tests/mdx/src/posts/frontmatter-engine/js-frontmatter.mdx

@@ -0,0 +1,16 @@
+---js
+(() => {
+require(`fs`).writeFileSync(`${process.cwd()}/cypress/fixtures/file-to-attempt-rce-on.txt`, (new Error('Helpful stack trace if this does execute. It should not execute.')).stack)
+console.trace()
+return {
+title: `I should not be parsed`
+}
+})()
+
+---
+
+<h1>JS frontmatter engine is disabled by default</h1>
+
+<span data-cy="js-frontmatter">
+  {props.pageContext.frontmatter?.title || `disabled`}
+</span>

packages/gatsby-plugin-mdx/README.md

@@ -129,6 +129,7 @@ scope, and more.
 | [`mediaTypes`](#media-types)                                              | `["text/markdown", "text/x-markdown"]` | Determine which media types are processed by MDX                      |
 | [`shouldBlockNodeFromTransformation`](#shouldblocknodefromtransformation) | `(node) => false`                      | Disable MDX transformation for nodes where this function returns true |
 | [`commonmark`](#commonmark)                                               | `false`                                | Use CommonMark                                                        |
+| [`JSFrontmatterEngine`](#jsfrontmatterengine)                             | `false`                                | Add support for JavaScript frontmatter engine                         |
 
 #### Extensions
 
@@ -472,6 +473,10 @@ module.exports = {
 
 MDX will be parsed using CommonMark.
 
+#### JSFrontmatterEngine
+
+Adds support for JavaScript frontmatter engine. Use with caution - see https://github.com/gatsbyjs/gatsby/security/advisories/GHSA-mj46-r4gr-5x83
+
 ### Components
 
 MDX and `gatsby-plugin-mdx` use components for different things like rendering

packages/gatsby-plugin-mdx/__tests__/gatsby-node.js

@@ -17,6 +17,7 @@ describe(`pluginOptionsSchema`, () => {
       `"mediaTypes[1]" must be a string`,
       `"shouldBlockNodeFromTransformation" must have an arity lesser or equal to 1`,
       `"root" must be a string`,
+      `"JSFrontmatterEngine" must be a boolean`,
     ]
 
     const { errors } = await testPluginOptionsSchema(pluginOptionsSchema, {
@@ -29,6 +30,7 @@ describe(`pluginOptionsSchema`, () => {
       mediaTypes: [1, 2],
       shouldBlockNodeFromTransformation: (wrong, number) => null,
       root: 1,
+      JSFrontmatterEngine: `this should be a boolean`,
     })
 
     expect(errors).toEqual(expectedErrors)
@@ -63,6 +65,7 @@ describe(`pluginOptionsSchema`, () => {
       mediaTypes: [`text/markdown`, `text/x-markdown`, `custom-media/type`],
       shouldBlockNodeFromTransformation: node => Boolean(node),
       root: `james-holden`,
+      JSFrontmatterEngine: true,
     })
 
     expect(isValid).toBe(true)