From 5219cdf2c9b576d30c828e6375411528fcdddfd6 Mon Sep 17 00:00:00 2001
From: Evan Hahn <69474926+EvanHahn-Signal@users.noreply.github.com>
Date: Wed, 5 Oct 2022 16:35:56 +0000
Subject: [PATCH] Make 1 the minimum registration ID

---
 ts/Crypto.ts                    | 28 ++++++++--------------------
 ts/context/Crypto.ts            |  4 ++++
 ts/test-electron/Crypto_test.ts | 18 +++++++++++++++---
 ts/textsecure/WebAPI.ts         |  6 +++---
 4 files changed, 30 insertions(+), 26 deletions(-)

diff --git a/ts/Crypto.ts b/ts/Crypto.ts
index 15e3d4303c7f..4971b2b87494 100644
--- a/ts/Crypto.ts
+++ b/ts/Crypto.ts
@@ -34,17 +34,8 @@ export type EncryptedAttachment = {
   digest: Uint8Array;
 };
 
-// Generate a number between zero and 16383
 export function generateRegistrationId(): number {
-  const bytes = getRandomBytes(2);
-  const id = new Uint16Array(
-    bytes.buffer,
-    bytes.byteOffset,
-    bytes.byteLength / 2
-  )[0];
-
-  // eslint-disable-next-line no-bitwise
-  return id & 0x3fff;
+  return randomInt(1, 16383);
 }
 
 export function deriveStickerPackKey(packKey: Uint8Array): Uint8Array {
@@ -342,16 +333,6 @@ export function sha256(data: Uint8Array): Uint8Array {
 
 // Utility
 
-export function getRandomValue(low: number, high: number): number {
-  const diff = high - low;
-  const bytes = getRandomBytes(1);
-
-  // Because high and low are inclusive
-  const mod = diff + 1;
-
-  return (bytes[0] % mod) + low;
-}
-
 export function getZeroes(n: number): Uint8Array {
   return new Uint8Array(n);
 }
@@ -683,6 +664,13 @@ export function decrypt(
   return crypto.decrypt(...args);
 }
 
+/**
+ * Generate an integer between `min` and `max`, inclusive.
+ */
+export function randomInt(min: number, max: number): number {
+  return crypto.randomInt(min, max + 1);
+}
+
 export function getRandomBytes(size: number): Uint8Array {
   return crypto.getRandomBytes(size);
 }
diff --git a/ts/context/Crypto.ts b/ts/context/Crypto.ts
index be1f8a80cc56..e8651db34dc4 100644
--- a/ts/context/Crypto.ts
+++ b/ts/context/Crypto.ts
@@ -119,6 +119,10 @@ export class Crypto {
     return Buffer.concat([decipher.update(input), decipher.final()]);
   }
 
+  public randomInt(min: number, max: number): number {
+    return crypto.randomInt(min, max);
+  }
+
   public getRandomBytes(size: number): Uint8Array {
     return crypto.randomBytes(size);
   }
diff --git a/ts/test-electron/Crypto_test.ts b/ts/test-electron/Crypto_test.ts
index 88fbcf04dd7c..85f644376c74 100644
--- a/ts/test-electron/Crypto_test.ts
+++ b/ts/test-electron/Crypto_test.ts
@@ -25,6 +25,7 @@ import {
   decryptSymmetric,
   hmacSha256,
   verifyHmacSha256,
+  randomInt,
   uuidToBytes,
   bytesToUuid,
 } from '../Crypto';
@@ -164,11 +165,11 @@ describe('Crypto', () => {
   });
 
   describe('generateRegistrationId', () => {
-    it('generates an integer between 0 and 16383 (inclusive)', () => {
-      let max = 0;
+    it('generates an integer between 1 and 16383 (inclusive)', () => {
+      let max = -1;
       for (let i = 0; i < 100; i += 1) {
         const id = generateRegistrationId();
-        assert.isAtLeast(id, 0);
+        assert.isAtLeast(id, 1);
         assert.isAtMost(id, 16383);
         assert(Number.isInteger(id));
 
@@ -441,6 +442,17 @@ describe('Crypto', () => {
     });
   });
 
+  describe('randomInt', () => {
+    it('returns random integers in a range (inclusive)', () => {
+      const seen = new Set<number>();
+      for (let i = 0; i < 1_000_000 || seen.size < 3; i += 1) {
+        seen.add(randomInt(1, 3));
+      }
+
+      assert.deepStrictEqual(seen, new Set([1, 2, 3]));
+    });
+  });
+
   describe('uuidToBytes', () => {
     it('converts valid UUIDs to Uint8Arrays', () => {
       const expectedResult = new Uint8Array([
diff --git a/ts/textsecure/WebAPI.ts b/ts/textsecure/WebAPI.ts
index 3b930428e775..109da0b61c7b 100644
--- a/ts/textsecure/WebAPI.ts
+++ b/ts/textsecure/WebAPI.ts
@@ -35,7 +35,7 @@ import type { UUID, UUIDStringType } from '../types/UUID';
 import { UUIDKind } from '../types/UUID';
 import type { DirectoryConfigType } from '../types/RendererConfig';
 import * as Bytes from '../Bytes';
-import { getRandomValue } from '../Crypto';
+import { randomInt } from '../Crypto';
 import * as linkPreviewFetch from '../linkPreviews/linkPreviewFetch';
 import { isBadgeImageFileUrlValid } from '../badges/isBadgeImageFileUrlValid';
 
@@ -2431,11 +2431,11 @@ export function initialize({
     }
 
     function getHeaderPadding() {
-      const max = getRandomValue(1, 64);
+      const max = randomInt(1, 64);
       let characters = '';
 
       for (let i = 0; i < max; i += 1) {
-        characters += String.fromCharCode(getRandomValue(65, 122));
+        characters += String.fromCharCode(randomInt(65, 122));
       }
 
       return characters;