backport fixes to releases-v3 (#2525)

* block checking out fork pr for pull_request_target and workflow_run (#2454)

* block checking out fork pr for some events

* address copilot and reviewer feedback

* run prettier formatting

* build

* update urls

* update readme

* update description and url again

* edit url one more time

* update error wording (#2467)

* Upgrade upload-artifact action to version 4

.github/workflows/check-dist.yml

@@ -44,7 +44,7 @@ jobs:
           fi
 
       # If dist/ was different than expected, upload the expected version as an artifact
-      - uses: actions/upload-artifact@v2
+      - uses: actions/upload-artifact@v4
         if: ${{ failure() && steps.diff.conclusion == 'failure' }}
         with:
           name: dist

README.md

@@ -114,6 +114,15 @@ When Git 2.18 or higher is not in your PATH, falls back to the REST API to downl
     # running from unless specified. Example URLs are https://github.com or
     # https://my-ghes-server.example.com
     github-server-url: ''
+
+    # Required to check out fork pull request code from a workflow triggered by
+    # `pull_request_target` or `workflow_run`. These workflows run with the base
+    # repository's GITHUB_TOKEN, secrets, default-branch cache scope, and runner
+    # access; fetching and executing a fork's code in that trusted context commonly
+    # leads to "pwn request" vulnerabilities. Set to `true` only after reviewing the
+    # risks at https://gh.io/securely-using-pull_request_target.
+    # Default: false
+    allow-unsafe-pr-checkout: ''
 ```
 <!-- end usage -->
 

__test__/git-auth-helper.test.ts

@@ -819,7 +819,8 @@ async function setup(testName: string): Promise<void> {
     sshStrict: true,
     workflowOrganizationId: 123456,
     setSafeDirectory: true,
-    githubServerUrl: githubServerUrl
+    githubServerUrl: githubServerUrl,
+    allowUnsafePrCheckout: false
   }
 }
 

__test__/input-helper.test.ts

@@ -12,15 +12,24 @@ const gitHubWorkspace = path.resolve('/checkout-tests/workspace')
 // Inputs for mock @actions/core
 let inputs = {} as any
 
+// Replicate @actions/core getInput behavior: it trims whitespace by default
+// (String.prototype.trim(), which strips characters such as a leading U+FEFF BOM)
+// unless trimWhitespace is explicitly set to false.
+const getInputImpl = (name: string, options?: {trimWhitespace?: boolean}) => {
+  const val = inputs[name] ?? ''
+  if (options && options.trimWhitespace === false) {
+    return val
+  }
+  return typeof val === 'string' ? val.trim() : val
+}
+
 // Shallow clone original @actions/github context
 let originalContext = {...github.context}
 
 describe('input-helper tests', () => {
   beforeAll(() => {
     // Mock getInput
-    jest.spyOn(core, 'getInput').mockImplementation((name: string) => {
-      return inputs[name]
-    })
+    jest.spyOn(core, 'getInput').mockImplementation(getInputImpl as any)
 
     // Mock error/warning/info/debug
     jest.spyOn(core, 'error').mockImplementation(jest.fn())
@@ -89,6 +98,7 @@ describe('input-helper tests', () => {
     expect(settings.repositoryOwner).toBe('some-owner')
     expect(settings.repositoryPath).toBe(gitHubWorkspace)
     expect(settings.setSafeDirectory).toBe(true)
+    expect(settings.allowUnsafePrCheckout).toBe(false)
   })
 
   it('qualifies ref', async () => {
@@ -138,8 +148,76 @@ describe('input-helper tests', () => {
     expect(settings.commit).toBeFalsy()
   })
 
+  it('does not reclassify a ref as sha when a BOM is prefixed', async () => {
+    // A fork branch named "<U+FEFF>" + 40 hex chars. core.getInput trims the
+    // BOM by default, which previously collapsed this into a bare SHA and
+    // bypassed the unsafe fork PR checkout guard.
+    inputs.ref = '\uFEFF522d932fae5296da51fdf431934425ecf891c6a2'
+    const settings: IGitSourceSettings = await inputHelper.getInputs()
+    expect(settings.commit).toBeFalsy()
+    expect(settings.ref).toBe('522d932fae5296da51fdf431934425ecf891c6a2')
+  })
+
+  it('treats a sha surrounded by ascii whitespace as a commit', async () => {
+    // ASCII whitespace can only come from the workflow author's YAML (git ref
+    // names cannot contain it), so trimming it and treating the value as a
+    // commit is safe.
+    inputs.ref = '  1111111111222222222233333333334444444444  '
+    const settings: IGitSourceSettings = await inputHelper.getInputs()
+    expect(settings.ref).toBeFalsy()
+    expect(settings.commit).toBe('1111111111222222222233333333334444444444')
+  })
+
   it('sets workflow organization ID', async () => {
     const settings: IGitSourceSettings = await inputHelper.getInputs()
     expect(settings.workflowOrganizationId).toBe(123456)
   })
+
+  describe('unsafe PR checkout guard', () => {
+    const forkPayload = {
+      repository: {id: 100},
+      pull_request: {
+        head: {
+          sha: '1234567890123456789012345678901234567890',
+          repo: {id: 200, full_name: 'attacker/fork'}
+        },
+        merge_commit_sha: 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
+      }
+    }
+
+    it('allows the default self-checkout on a fork pull_request_target', async () => {
+      const originalEvent = github.context.eventName
+      const originalPayload = github.context.payload
+      const originalSha = github.context.sha
+      try {
+        github.context.eventName = 'pull_request_target'
+        github.context.payload = forkPayload as any
+        // Simulate a rebase/fast-forward merge where the base tip (event SHA)
+        // equals the PR head SHA. The default self-checkout must still succeed.
+        github.context.sha = '1234567890123456789012345678901234567890'
+        const settings: IGitSourceSettings = await inputHelper.getInputs()
+        expect(settings.commit).toBe('1234567890123456789012345678901234567890')
+      } finally {
+        github.context.eventName = originalEvent
+        github.context.payload = originalPayload
+        github.context.sha = originalSha
+      }
+    })
+
+    it('refuses an explicit fork repository on pull_request_target', async () => {
+      const originalEvent = github.context.eventName
+      const originalPayload = github.context.payload
+      try {
+        github.context.eventName = 'pull_request_target'
+        github.context.payload = forkPayload as any
+        inputs.repository = 'attacker/fork'
+        await expect(inputHelper.getInputs()).rejects.toThrow(
+          /Refusing to check out fork pull request code/
+        )
+      } finally {
+        github.context.eventName = originalEvent
+        github.context.payload = originalPayload
+      }
+    })
+  })
 })

__test__/unsafe-pr-checkout-helper.test.ts

@@ -0,0 +1,267 @@
+import * as github from '@actions/github'
+import {assertSafePrCheckout} from '../lib/unsafe-pr-checkout-helper'
+
+// Shallow clone original @actions/github context
+const originalContext = {...github.context}
+const originalEventName = github.context.eventName
+const originalPayload = github.context.payload
+
+const BASE_REPO_ID = 100
+const FORK_REPO_ID = 200
+const PR_HEAD_SHA = '1111111111111111111111111111111111111111'
+const PR_MERGE_SHA = '2222222222222222222222222222222222222222'
+const SAFE_BASE_SHA = '3333333333333333333333333333333333333333'
+const WORKFLOW_RUN_HEAD_COMMIT_SHA = '4444444444444444444444444444444444444444'
+const BASE_QUALIFIED_REPO = 'some-owner/some-repo'
+const FORK_QUALIFIED_REPO = 'another-repo/fork'
+
+function setContext(eventName: string, payload: object): void {
+  ;(github.context as {eventName: string}).eventName = eventName
+  ;(github.context as {payload: object}).payload = payload
+}
+
+function forkPullRequestTargetPayload(): object {
+  return {
+    repository: {id: BASE_REPO_ID},
+    pull_request: {
+      head: {
+        sha: PR_HEAD_SHA,
+        repo: {id: FORK_REPO_ID, full_name: FORK_QUALIFIED_REPO}
+      },
+      merge_commit_sha: PR_MERGE_SHA
+    }
+  }
+}
+
+function sameRepoPullRequestTargetPayload(): object {
+  return {
+    repository: {id: BASE_REPO_ID},
+    pull_request: {
+      head: {
+        sha: PR_HEAD_SHA,
+        repo: {id: BASE_REPO_ID, full_name: BASE_QUALIFIED_REPO}
+      },
+      merge_commit_sha: PR_MERGE_SHA
+    }
+  }
+}
+
+function forkWorkflowRunPayload(): object {
+  return {
+    repository: {id: BASE_REPO_ID},
+    workflow_run: {
+      event: 'pull_request',
+      head_commit: {id: WORKFLOW_RUN_HEAD_COMMIT_SHA},
+      head_repository: {id: FORK_REPO_ID, full_name: FORK_QUALIFIED_REPO}
+    }
+  }
+}
+
+describe('unsafe-pr-checkout-helper', () => {
+  beforeAll(() => {
+    jest.spyOn(github.context, 'repo', 'get').mockReturnValue({
+      owner: 'some-owner',
+      repo: 'some-repo'
+    })
+  })
+
+  afterEach(() => {
+    ;(github.context as {eventName: string}).eventName = originalEventName
+    ;(github.context as {payload: object}).payload = originalPayload
+  })
+
+  afterAll(() => {
+    ;(github.context as {eventName: string}).eventName =
+      originalContext.eventName
+    ;(github.context as {payload: object}).payload = originalContext.payload
+    jest.restoreAllMocks()
+  })
+
+  it('allows pull_request events untouched', () => {
+    setContext('pull_request', forkPullRequestTargetPayload())
+    expect(() =>
+      assertSafePrCheckout({
+        qualifiedRepository: 'attacker/fork',
+        ref: 'refs/pull/1/merge',
+        commit: '',
+        allowUnsafePrCheckout: false
+      })
+    ).not.toThrow()
+  })
+
+  it('allows pull_request_target default checkout (base branch)', () => {
+    setContext('pull_request_target', forkPullRequestTargetPayload())
+    expect(() =>
+      assertSafePrCheckout({
+        qualifiedRepository: BASE_QUALIFIED_REPO,
+        ref: 'refs/heads/main',
+        commit: SAFE_BASE_SHA,
+        allowUnsafePrCheckout: false
+      })
+    ).not.toThrow()
+  })
+
+  it('allows same-repo pull_request_target checkout of PR head', () => {
+    setContext('pull_request_target', sameRepoPullRequestTargetPayload())
+    expect(() =>
+      assertSafePrCheckout({
+        qualifiedRepository: BASE_QUALIFIED_REPO,
+        ref: '',
+        commit: PR_HEAD_SHA,
+        allowUnsafePrCheckout: false
+      })
+    ).not.toThrow()
+  })
+
+  it('refuses pull_request_target fork PR head SHA checkout', () => {
+    setContext('pull_request_target', forkPullRequestTargetPayload())
+    expect(() =>
+      assertSafePrCheckout({
+        qualifiedRepository: BASE_QUALIFIED_REPO,
+        ref: '',
+        commit: PR_HEAD_SHA,
+        allowUnsafePrCheckout: false
+      })
+    ).toThrow(/Refusing to check out fork pull request code/)
+  })
+
+  it('refuses pull_request_target fork PR merge_commit_sha checkout', () => {
+    setContext('pull_request_target', forkPullRequestTargetPayload())
+    expect(() =>
+      assertSafePrCheckout({
+        qualifiedRepository: BASE_QUALIFIED_REPO,
+        ref: '',
+        commit: PR_MERGE_SHA,
+        allowUnsafePrCheckout: false
+      })
+    ).toThrow(/allow-unsafe-pr-checkout/)
+  })
+
+  it('refuses pull_request_target fork PR ref pattern (head)', () => {
+    setContext('pull_request_target', forkPullRequestTargetPayload())
+    expect(() =>
+      assertSafePrCheckout({
+        qualifiedRepository: BASE_QUALIFIED_REPO,
+        ref: 'refs/pull/42/head',
+        commit: '',
+        allowUnsafePrCheckout: false
+      })
+    ).toThrow()
+  })
+
+  it('refuses pull_request_target fork PR ref pattern (merge)', () => {
+    setContext('pull_request_target', forkPullRequestTargetPayload())
+    expect(() =>
+      assertSafePrCheckout({
+        qualifiedRepository: BASE_QUALIFIED_REPO,
+        ref: 'refs/pull/42/merge',
+        commit: '',
+        allowUnsafePrCheckout: false
+      })
+    ).toThrow()
+  })
+
+  it('refuses pull_request_target when repository points at the fork', () => {
+    setContext('pull_request_target', forkPullRequestTargetPayload())
+    expect(() =>
+      assertSafePrCheckout({
+        qualifiedRepository: FORK_QUALIFIED_REPO,
+        ref: 'refs/heads/main',
+        commit: '',
+        allowUnsafePrCheckout: false
+      })
+    ).toThrow()
+  })
+
+  it('allows pull_request_target checkout of an unrelated third-party repo', () => {
+    setContext('pull_request_target', forkPullRequestTargetPayload())