trim only ascii whitespace for branch (#2521)

* trim only ascii whitespace for branch

* rebuild

__test__/input-helper.test.ts

@@ -24,9 +24,20 @@ const mockGithubContext: any = {
   payload: {}
 }
 
+// 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
+}
+
 // Mock @actions/core before loading input-helper
 jest.unstable_mockModule('@actions/core', () => ({
-  getInput: jest.fn((name: string) => inputs[name]),
+  getInput: jest.fn(getInputImpl),
   getBooleanInput: jest.fn((name: string) => inputs[name]),
   getMultilineInput: jest.fn((name: string) =>
     inputs[name] ? String(inputs[name]).split('\n').filter(Boolean) : []
@@ -76,9 +87,7 @@ describe('input-helper tests', () => {
     inputs = {}
     jest.clearAllMocks()
     // Re-apply default mocks
-    ;(core.getInput as jest.Mock<any>).mockImplementation(
+    ;(core.getInput as jest.Mock<any>).mockImplementation(getInputImpl as any)
-      (name: string) => inputs[name]
-    )
     mockDirectoryExistsSync.mockImplementation(
       (p: string) => p === gitHubWorkspace
     )
@@ -176,8 +185,84 @@ 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('does not reclassify a sha-256 ref as sha when a BOM is prefixed', async () => {
+    inputs.ref =
+      '\uFEFF1111111111222222222233333333334444444444555555555566666666667777'
+    const settings: IGitSourceSettings = await inputHelper.getInputs()
+    expect(settings.commit).toBeFalsy()
+    expect(settings.ref).toBe(
+      '1111111111222222222233333333334444444444555555555566666666667777'
+    )
+  })
+
+  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 = mockGithubContext.eventName
+      const originalPayload = mockGithubContext.payload
+      try {
+        mockGithubContext.eventName = 'pull_request_target'
+        mockGithubContext.payload = forkPayload
+        // Simulate a rebase/fast-forward merge where the base tip (event SHA)
+        // equals the PR head SHA. The default self-checkout must still succeed.
+        mockGithubContext.sha = '1234567890123456789012345678901234567890'
+        const settings: IGitSourceSettings = await inputHelper.getInputs()
+        expect(settings.commit).toBe('1234567890123456789012345678901234567890')
+      } finally {
+        mockGithubContext.eventName = originalEvent
+        mockGithubContext.payload = originalPayload
+      }
+    })
+
+    it('refuses an explicit fork repository on pull_request_target', async () => {
+      const originalEvent = mockGithubContext.eventName
+      const originalPayload = mockGithubContext.payload
+      try {
+        mockGithubContext.eventName = 'pull_request_target'
+        mockGithubContext.payload = forkPayload
+        inputs.repository = 'attacker/fork'
+        await expect(inputHelper.getInputs()).rejects.toThrow(
+          /Refusing to check out fork pull request code/
+        )
+      } finally {
+        mockGithubContext.eventName = originalEvent
+        mockGithubContext.payload = originalPayload
+      }
+    })
+  })
 })

dist/index.js

@@ -42100,6 +42100,22 @@ async function getInputs() {
         `${github_context.repo.owner}/${github_context.repo.repo}`.toUpperCase();
     // Source branch, source version
     result.ref = getInput('ref');
+    // core.getInput()'s default trim strips a range of Unicode characters such as a
+    // leading BOM (U+FEFF) or NBSP (U+00A0). Those are valid in a git ref name, so
+    // a fork branch named "<BOM>" + 40 hex chars would trim down to a bare SHA and
+    // be silently reclassified as a commit, bypassing the unsafe fork PR checkout
+    // guard.
+    //
+    // The trim below strips only the ASCII whitespace characters which are all forbidden
+    // in a git branch name.
+    //   \t  U+0009  horizontal tab   - ASCII control, forbidden in ref names
+    //   \n  U+000A  line feed        - ASCII control, forbidden in ref names
+    //   \v  U+000B  vertical tab     - ASCII control, forbidden in ref names
+    //   \f  U+000C  form feed        - ASCII control, forbidden in ref names
+    //   \r  U+000D  carriage return  - ASCII control, forbidden in ref names
+    //   ' ' U+0020  space            - forbidden in ref names
+    const asciiTrimmedRef = getInput('ref', { trimWhitespace: false })
+        .replace(/^[\t\n\v\f\r ]+|[\t\n\v\f\r ]+$/g, '');
     if (!result.ref) {
         if (isWorkflowRepository) {
             result.ref = github_context.ref;
@@ -42112,8 +42128,8 @@ async function getInputs() {
         }
     }
     // SHA?
-    else if (result.ref.match(/^(?:[0-9a-fA-F]{40}|[0-9a-fA-F]{64})$/)) {
+    else if (asciiTrimmedRef.match(/^(?:[0-9a-fA-F]{40}|[0-9a-fA-F]{64})$/)) {
-        result.commit = result.ref;
+        result.commit = asciiTrimmedRef;
         result.ref = '';
     }
     core_debug(`ref = '${result.ref}'`);
@@ -42191,12 +42207,19 @@ async function getInputs() {
         (getInput('allow-unsafe-pr-checkout') || 'false').toUpperCase() ===
             'TRUE';
     core_debug(`allow unsafe PR checkout = ${result.allowUnsafePrCheckout}`);
+    // The default self-checkout (this repository with no explicit ref) always
+    // resolves to the trusted ref/commit GitHub set for the triggering event, so
+    // the fork-checkout guard only needs to run when the caller customized the
+    // repository or ref.
+    const isDefaultCheckout = isWorkflowRepository && !getInput('ref');
+    if (!isDefaultCheckout) {
         assertSafePrCheckout({
             qualifiedRepository,
             ref: result.ref,
             commit: result.commit,
             allowUnsafePrCheckout: result.allowUnsafePrCheckout
         });
+    }
     return result;
 }
 

package-lock.json

@@ -20,13 +20,13 @@
         "@types/node": "^24.1.0",
         "@typescript-eslint/eslint-plugin": "^8.54.0",
         "@typescript-eslint/parser": "^8.54.0",
-        "@vercel/ncc": "^0.44.1",
+        "@vercel/ncc": "^0.44.0",
         "eslint": "^9.39.2",
-        "eslint-plugin-github": "^6.1.1",
+        "eslint-plugin-github": "^6.0.0",
         "eslint-plugin-jest": "^29.12.1",
         "jest": "^29.7.0",
         "js-yaml": "^4.2.0",
-        "prettier": "^3.9.5",
+        "prettier": "^3.8.4",
         "ts-jest": "^29.4.11",
         "ts-node": "^10.9.2",
         "typescript": "^5.5.4"
@@ -680,19 +680,19 @@
       }
     },
     "node_modules/@eslint/compat": {
-      "version": "2.1.0",
+      "version": "1.4.1",
-      "resolved": "https://registry.npmjs.org/@eslint/compat/-/compat-2.1.0.tgz",
+      "resolved": "https://registry.npmjs.org/@eslint/compat/-/compat-1.4.1.tgz",
-      "integrity": "sha512-LgaSCymEpw7tF53xvDw9SNsraPb1IBHxpdABIOM0hW8UAlP8znrjYtuxfR58FSJ3L9BhwD+FaPRFQpZq84Nh6g==",
+      "integrity": "sha512-cfO82V9zxxGBxcQDr1lfaYB7wykTa0b00mGa36FrJl7iTFd0Z2cHfEYuxcBRP/iNijCsWsEkA+jzT8hGYmv33w==",
       "dev": true,
       "license": "Apache-2.0",
       "dependencies": {
-        "@eslint/core": "^1.2.1"
+        "@eslint/core": "^0.17.0"
       },
       "engines": {
-        "node": "^20.19.0 || ^22.13.0 || >=24"
+        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
       },
       "peerDependencies": {
-        "eslint": "^8.40 || 9 || 10"
+        "eslint": "^8.40 || 9"
       },
       "peerDependenciesMeta": {
         "eslint": {
@@ -700,19 +700,6 @@
         }
       }
     },
-    "node_modules/@eslint/compat/node_modules/@eslint/core": {
-      "version": "1.2.1",
-      "resolved": "https://registry.npmjs.org/@eslint/core/-/core-1.2.1.tgz",
-      "integrity": "sha512-MwcE1P+AZ4C6DWlpin/OmOA54mmIZ/+xZuJiQd4SyB29oAJjN30UW9wkKNptW2ctp4cEsvhlLY/CsQ1uoHDloQ==",
-      "dev": true,
-      "license": "Apache-2.0",
-      "dependencies": {
-        "@types/json-schema": "^7.0.15"
-      },
-      "engines": {
-        "node": "^20.19.0 || ^22.13.0 || >=24"
-      }
-    },
     "node_modules/@eslint/config-array": {
       "version": "0.21.2",
       "resolved": "https://registry.npmjs.org/@eslint/config-array/-/config-array-0.21.2.tgz",
@@ -1999,9 +1986,9 @@
       }
     },
     "node_modules/@vercel/ncc": {
-      "version": "0.44.1",
+      "version": "0.44.0",
-      "resolved": "https://registry.npmjs.org/@vercel/ncc/-/ncc-0.44.1.tgz",
+      "resolved": "https://registry.npmjs.org/@vercel/ncc/-/ncc-0.44.0.tgz",
-      "integrity": "sha512-cUjIE5P2YY1n+Kt9rFIazMMpGoPn1Fic04rOmTkElMkiDP5oszGfERMpo2shVkFKDL7rVppdM2pqJKC59shQWQ==",
+      "integrity": "sha512-pHyI+bZokSgIscTKFSmpNk5vZzmOrb9RW0Vu4SRyqUvkJ0kgg3PzaZLLDVTFXhbUiCqg0/Eu8L4fKtgViA92kg==",
       "dev": true,
       "license": "MIT",
       "bin": {
@@ -3423,13 +3410,13 @@
       }
     },
     "node_modules/eslint-plugin-github": {
-      "version": "6.1.1",
+      "version": "6.0.0",
-      "resolved": "https://registry.npmjs.org/eslint-plugin-github/-/eslint-plugin-github-6.1.1.tgz",
+      "resolved": "https://registry.npmjs.org/eslint-plugin-github/-/eslint-plugin-github-6.0.0.tgz",
-      "integrity": "sha512-xCqu1S/s/CCvoRLafaXNvwiVrxhroNOFLGyG9Dhi4i1PWZgPHlipjXysH6wccPFQyhSKE7gAjSLqdSdM204bZQ==",
+      "integrity": "sha512-J8MvUoiR/TU/Y9NnEmg1AnbvMUj9R6IO260z47zymMLLvso7B4c80IKjd8diqmqtSmeXXlbIus4i0SvK84flag==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
-        "@eslint/compat": "^2.0.0",
+        "@eslint/compat": "^1.2.3",
         "@eslint/eslintrc": "^3.1.0",
         "@eslint/js": "^9.14.0",
         "@github/browserslist-config": "^1.0.0",
@@ -3446,24 +3433,24 @@
         "eslint-plugin-no-only-tests": "^3.0.0",
         "eslint-plugin-prettier": "^5.2.1",
         "eslint-rule-documentation": ">=1.0.0",
-        "globals": "^17.7.0",
+        "globals": "^16.0.0",
         "jsx-ast-utils": "^3.3.2",
         "prettier": "^3.0.0",
         "svg-element-attributes": "^1.3.1",
-        "typescript": "^6.0.3",
+        "typescript": "^5.7.3",
         "typescript-eslint": "^8.14.0"
       },
       "bin": {
         "eslint-ignore-errors": "bin/eslint-ignore-errors.js"
       },
       "peerDependencies": {
-        "eslint": "^8 || ^9 || ^10"
+        "eslint": "^8 || ^9"
       }
     },
     "node_modules/eslint-plugin-github/node_modules/globals": {
-      "version": "17.7.0",
+      "version": "16.5.0",
-      "resolved": "https://registry.npmjs.org/globals/-/globals-17.7.0.tgz",
+      "resolved": "https://registry.npmjs.org/globals/-/globals-16.5.0.tgz",
-      "integrity": "sha512-Czmyns5dUsq4seFBR/Kdydhmo8y9kC79hiSkPn0YcGtNnYWnrgt0vjrSjx9tspoDGWm2CMarffRuLjM4xUz8xg==",
+      "integrity": "sha512-c/c15i26VrJ4IRt5Z89DnIzCGDn9EcebibhAOjw5ibqEHsE1wLUgkPn9RDmNcUKyU87GeaL633nyJ+pplFR2ZQ==",
       "dev": true,
       "license": "MIT",
       "engines": {
@@ -3473,20 +3460,6 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
-    "node_modules/eslint-plugin-github/node_modules/typescript": {
-      "version": "6.0.3",
-      "resolved": "https://registry.npmjs.org/typescript/-/typescript-6.0.3.tgz",
-      "integrity": "sha512-y2TvuxSZPDyQakkFRPZHKFm+KKVqIisdg9/CZwm9ftvKXLP8NRWj38/ODjNbr43SsoXqNuAisEf1GdCxqWcdBw==",
-      "dev": true,
-      "license": "Apache-2.0",
-      "bin": {
-        "tsc": "bin/tsc",
-        "tsserver": "bin/tsserver"
-      },
-      "engines": {
-        "node": ">=14.17"
-      }
-    },
     "node_modules/eslint-plugin-i18n-text": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/eslint-plugin-i18n-text/-/eslint-plugin-i18n-text-1.0.1.tgz",
@@ -6470,9 +6443,9 @@
       }
     },
     "node_modules/prettier": {
-      "version": "3.9.5",
+      "version": "3.8.4",
-      "resolved": "https://registry.npmjs.org/prettier/-/prettier-3.9.5.tgz",
+      "resolved": "https://registry.npmjs.org/prettier/-/prettier-3.8.4.tgz",
-      "integrity": "sha512-/FVl766LpUfB5vXgCYOYa0MeV/441Ia99AeICQIQFTY/Nw0roZwULcXpku5i1/m5kt/baz+s4Zogspd839HSMg==",
+      "integrity": "sha512-N2MylSdi48+5N/6S5j+maeHbUSIzzZ5uOcX5Hm4QpV8Dkb1HFjfAKTKX6yNPJQD9AhcT3ifHNB66tWTTJDi11Q==",
       "dev": true,
       "license": "MIT",
       "bin": {

package.json

@@ -43,13 +43,13 @@
     "@types/node": "^24.1.0",
     "@typescript-eslint/eslint-plugin": "^8.54.0",
     "@typescript-eslint/parser": "^8.54.0",
-    "@vercel/ncc": "^0.44.1",
+    "@vercel/ncc": "^0.44.0",
     "eslint": "^9.39.2",
-    "eslint-plugin-github": "^6.1.1",
+    "eslint-plugin-github": "^6.0.0",
     "eslint-plugin-jest": "^29.12.1",
     "jest": "^29.7.0",
     "js-yaml": "^4.2.0",
-    "prettier": "^3.9.5",
+    "prettier": "^3.8.4",
     "ts-jest": "^29.4.11",
     "ts-node": "^10.9.2",
     "typescript": "^5.5.4"

src/input-helper.ts

@@ -59,6 +59,23 @@ export async function getInputs(): Promise<IGitSourceSettings> {
 
   // Source branch, source version
   result.ref = core.getInput('ref')
+  // core.getInput()'s default trim strips a range of Unicode characters such as a
+  // leading BOM (U+FEFF) or NBSP (U+00A0). Those are valid in a git ref name, so
+  // a fork branch named "<BOM>" + 40 hex chars would trim down to a bare SHA and
+  // be silently reclassified as a commit, bypassing the unsafe fork PR checkout
+  // guard.
+  //
+  // The trim below strips only the ASCII whitespace characters which are all forbidden
+  // in a git branch name.
+  //   \t  U+0009  horizontal tab   - ASCII control, forbidden in ref names
+  //   \n  U+000A  line feed        - ASCII control, forbidden in ref names
+  //   \v  U+000B  vertical tab     - ASCII control, forbidden in ref names
+  //   \f  U+000C  form feed        - ASCII control, forbidden in ref names
+  //   \r  U+000D  carriage return  - ASCII control, forbidden in ref names
+  //   ' ' U+0020  space            - forbidden in ref names
+  const asciiTrimmedRef = core
+    .getInput('ref', {trimWhitespace: false})
+    .replace(/^[\t\n\v\f\r ]+|[\t\n\v\f\r ]+$/g, '')
   if (!result.ref) {
     if (isWorkflowRepository) {
       result.ref = github.context.ref
@@ -72,8 +89,8 @@ export async function getInputs(): Promise<IGitSourceSettings> {
     }
   }
   // SHA?
-  else if (result.ref.match(/^(?:[0-9a-fA-F]{40}|[0-9a-fA-F]{64})$/)) {
+  else if (asciiTrimmedRef.match(/^(?:[0-9a-fA-F]{40}|[0-9a-fA-F]{64})$/)) {
-    result.commit = result.ref
+    result.commit = asciiTrimmedRef
     result.ref = ''
   }
   core.debug(`ref = '${result.ref}'`)
@@ -168,12 +185,19 @@ export async function getInputs(): Promise<IGitSourceSettings> {
     'TRUE'
   core.debug(`allow unsafe PR checkout = ${result.allowUnsafePrCheckout}`)
 
+  // The default self-checkout (this repository with no explicit ref) always
+  // resolves to the trusted ref/commit GitHub set for the triggering event, so
+  // the fork-checkout guard only needs to run when the caller customized the
+  // repository or ref.
+  const isDefaultCheckout = isWorkflowRepository && !core.getInput('ref')
+  if (!isDefaultCheckout) {
     unsafePrCheckoutHelper.assertSafePrCheckout({
       qualifiedRepository,
       ref: result.ref,
       commit: result.commit,
       allowUnsafePrCheckout: result.allowUnsafePrCheckout
     })
+  }
 
   return result
 }