[Security] Harden takeRandomFromArray

packages/cli-kit/src/public/common/array.test.ts

@@ -1,4 +1,4 @@
-import {difference, uniq, uniqBy} from './array.js'
+import {difference, takeRandomFromArray, uniq, uniqBy} from './array.js'
 import {describe, test, expect} from 'vitest'
 
 describe('uniqBy', () => {
@@ -62,3 +62,38 @@ describe('difference', () => {
     expect(got).toEqual([1])
   })
 })
+
+describe('takeRandomFromArray', () => {
+  test('returns a random element from the array', () => {
+    // Given
+    const array = [1, 2, 3, 4, 5]
+
+    // When
+    const got = takeRandomFromArray(array)
+
+    // Then
+    expect(array).toContain(got)
+  })
+
+  test('returns undefined for an empty array', () => {
+    // Given
+    const array: number[] = []
+
+    // When
+    const got = takeRandomFromArray(array)
+
+    // Then
+    expect(got).toBeUndefined()
+  })
+
+  test('handles arrays with a single element', () => {
+    // Given
+    const array = ['only']
+
+    // When
+    const got = takeRandomFromArray(array)
+
+    // Then
+    expect(got).toBe('only')
+  })
+})

packages/cli-kit/src/public/common/array.ts

@@ -9,7 +9,19 @@ import type {List, ValueIteratee} from 'lodash'
  * @returns A random element from the array.
  */
 export function takeRandomFromArray<T>(array: T[]): T {
-  return array[Math.floor(Math.random() * array.length)]!
+  if (array.length === 0) {
+    return undefined as T
+  }
+  const arrayLength = array.length
+  const maxUint32 = 0xffffffff
+  const limit = maxUint32 - (maxUint32 % arrayLength)
+  const buffer = new Uint32Array(1)
+  let randomNumber: number
+  do {
+    globalThis.crypto.getRandomValues(buffer)
+    randomNumber = buffer[0]!
+  } while (randomNumber >= limit)
+  return array[randomNumber % arrayLength]!
 }
 
 /**