fix: prototype pollution in handleFlatJson

Author: kazupon

packages/vue-i18n-core/src/utils.ts

@@ -69,6 +69,9 @@ export function handleFlatJson(obj: unknown): unknown {
       let currentObj = obj
       let hasStringValue = false
       for (let i = 0; i < lastIndex; i++) {
+        if (subKeys[i] === '__proto__') {
+          throw new Error(`unsafe key: ${subKeys[i]}`)
+        }
         if (!(subKeys[i] in currentObj)) {
           currentObj[subKeys[i]] = create()
         }

packages/vue-i18n-core/test/utils.test.ts

@@ -1,65 +1,80 @@
 // utils
 import * as shared from '@intlify/shared'
+import { handleFlatJson } from '../src/utils'
+import { I18nWarnCodes, getWarnMessage } from '../src/warnings'
 vi.mock('@intlify/shared', async () => {
   const actual = await vi.importActual<object>('@intlify/shared')
   return {
     ...actual,
     warn: vi.fn()
   }
 })
-import { handleFlatJson } from '../src/utils'
-import { I18nWarnCodes, getWarnMessage } from '../src/warnings'
 
-test('handleFlatJson', () => {
-  const mockWarn = vi.spyOn(shared, 'warn')
-  // eslint-disable-next-line @typescript-eslint/no-empty-function
-  mockWarn.mockImplementation(() => {})
+describe('handleFlatJson', () => {
+  test('basic', () => {
+    const mockWarn = vi.spyOn(shared, 'warn')
+    // eslint-disable-next-line @typescript-eslint/no-empty-function
+    mockWarn.mockImplementation(() => {})
 
-  const obj = {
-    a: { a1: 'a1.value' },
-    'a.a2': 'a.a2.value',
-    'b.x': {
-      'b1.x': 'b1.x.value',
-      'b2.x': ['b2.x.value0', 'b2.x.value1'],
-      'b3.x': { 'b3.x': 'b3.x.value' }
-    },
-    c: {
-      'animal.dog': 'Dog',
-      animal: 'Animal'
-    },
-    d: {
-      'animal.dog': 'Dog',
-      animal: {}
-    }
-  }
-  const expectObj = {
-    a: {
-      a1: 'a1.value',
-      a2: 'a.a2.value'
-    },
-    b: {
-      x: {
-        b1: { x: 'b1.x.value' },
-        b2: { x: ['b2.x.value0', 'b2.x.value1'] },
-        b3: { x: { b3: { x: 'b3.x.value' } } }
+    const obj = {
+      a: { a1: 'a1.value' },
+      'a.a2': 'a.a2.value',
+      'b.x': {
+        'b1.x': 'b1.x.value',
+        'b2.x': ['b2.x.value0', 'b2.x.value1'],
+        'b3.x': { 'b3.x': 'b3.x.value' }
+      },
+      c: {
+        'animal.dog': 'Dog',
+        animal: 'Animal'
+      },
+      d: {
+        'animal.dog': 'Dog',
+        animal: {}
       }
-    },
-    c: {
-      'animal.dog': 'Dog',
-      animal: 'Animal'
-    },
-    d: {
-      animal: {
-        dog: 'Dog'
+    }
+    const expectObj = {
+      a: {
+        a1: 'a1.value',
+        a2: 'a.a2.value'
+      },
+      b: {
+        x: {
+          b1: { x: 'b1.x.value' },
+          b2: { x: ['b2.x.value0', 'b2.x.value1'] },
+          b3: { x: { b3: { x: 'b3.x.value' } } }
+        }
+      },
+      c: {
+        'animal.dog': 'Dog',
+        animal: 'Animal'
+      },
+      d: {
+        animal: {
+          dog: 'Dog'
+        }
       }
     }
-  }
 
-  expect(handleFlatJson(obj)).toEqual(expectObj)
-  expect(mockWarn).toHaveBeenCalled()
-  expect(mockWarn.mock.calls[0][0]).toEqual(
-    getWarnMessage(I18nWarnCodes.IGNORE_OBJ_FLATTEN, {
-      key: 'animal'
-    })
-  )
+    expect(handleFlatJson(obj)).toEqual(expectObj)
+    expect(mockWarn).toHaveBeenCalled()
+    expect(mockWarn.mock.calls[0][0]).toEqual(
+      getWarnMessage(I18nWarnCodes.IGNORE_OBJ_FLATTEN, {
+        key: 'animal'
+      })
+    )
+  })
+
+  // security advisories
+  // ref: https://github.com/intlify/vue-i18n/security/advisories/GHSA-p2ph-7g93-hw3m
+  test('prototype pollution', () => {
+    expect(() =>
+      handleFlatJson({ '__proto__.pollutedKey': 'pollutedValue' })
+    ).toThrow()
+    // @ts-ignore -- test
+    // eslint-disable-next-line no-proto
+    expect({}.__proto__.pollutedKey).toBeUndefined()
+    // @ts-ignore -- test
+    expect(Object.prototype.pollutedKey).toBeUndefined()
+  })
 })