Revert "Store IV when encrypting or decrypting attachments"

ts/AttachmentCrypto.ts

@@ -27,7 +27,6 @@ import type { ContextType } from './types/Message2';
 import { strictAssert } from './util/assert';
 import * as Errors from './types/errors';
 import { isNotNil } from './util/isNotNil';
-import { missingCaseError } from './util/missingCaseError';
 
 // This file was split from ts/Crypto.ts because it pulls things in from node, and
 //   too many things pull in Crypto.ts, so it broke storybook.
@@ -47,14 +46,12 @@ export function _generateAttachmentIv(): Uint8Array {
 
 export type EncryptedAttachmentV2 = {
   digest: Uint8Array;
-  iv: Uint8Array;
   plaintextHash: string;
   ciphertextSize: number;
 };
 
 export type DecryptedAttachmentV2 = {
   path: string;
-  iv: Uint8Array;
   plaintextHash: string;
 };
 
@@ -62,21 +59,10 @@ export type PlaintextSourceType =
   | { data: Uint8Array }
   | { absolutePath: string };
 
-export type HardcodedIVForEncryptionType =
-  | {
-      reason: 'test';
-      iv: Uint8Array;
-    }
-  | {
-      reason: 'reencrypting-for-backup';
-      iv: Uint8Array;
-      digestToMatch: Uint8Array;
-    };
-
 type EncryptAttachmentV2PropsType = {
   plaintext: PlaintextSourceType;
   keys: Readonly<Uint8Array>;
-  dangerousIv?: HardcodedIVForEncryptionType;
+  dangerousTestOnlyIv?: Readonly<Uint8Array>;
   dangerousTestOnlySkipPadding?: boolean;
 };
 
@@ -110,7 +96,7 @@ export async function encryptAttachmentV2ToDisk(
 export async function encryptAttachmentV2({
   keys,
   plaintext,
-  dangerousIv,
+  dangerousTestOnlyIv,
   dangerousTestOnlySkipPadding,
   sink,
 }: EncryptAttachmentV2PropsType & {
@@ -120,26 +106,9 @@ export async function encryptAttachmentV2({
 
   const { aesKey, macKey } = splitKeys(keys);
 
-  if (dangerousIv) {
-    if (dangerousIv.reason === 'test') {
-      if (window.getEnvironment() !== Environment.Test) {
-        throw new Error(
-          `${logId}: Used dangerousIv with reason test outside tests!`
-        );
-      }
-    } else if (dangerousIv.reason === 'reencrypting-for-backup') {
-      strictAssert(
-        dangerousIv.digestToMatch.byteLength === DIGEST_LENGTH,
-        `${logId}: Must provide valid digest to match if providing iv for re-encryption`
-      );
-      log.info(
-        `${logId}: using hardcoded iv because we are re-encrypting for backup`
-      );
-    } else {
-      throw missingCaseError(dangerousIv);
-    }
+  if (dangerousTestOnlyIv && window.getEnvironment() !== Environment.Test) {
+    throw new Error(`${logId}: Used dangerousTestOnlyIv outside tests!`);
   }
-
   if (
     dangerousTestOnlySkipPadding &&
     window.getEnvironment() !== Environment.Test
@@ -148,8 +117,7 @@ export async function encryptAttachmentV2({
       `${logId}: Used dangerousTestOnlySkipPadding outside tests!`
     );
   }
-
-  const iv = dangerousIv?.iv || _generateAttachmentIv();
+  const iv = dangerousTestOnlyIv || _generateAttachmentIv();
   const plaintextHash = createHash(HashType.size256);
   const digest = createHash(HashType.size256);
 
@@ -199,16 +167,8 @@ export async function encryptAttachmentV2({
 
   strictAssert(ciphertextSize != null, 'Failed to measure ciphertext size!');
 
-  if (dangerousIv?.reason === 'reencrypting-for-backup') {
-    if (!constantTimeEqual(ourDigest, dangerousIv.digestToMatch)) {
-      throw new Error(
-        `${logId}: iv was hardcoded for backup re-encryption, but digest does not match`
-      );
-    }
-  }
   return {
     digest: ourDigest,
-    iv,
     plaintextHash: ourPlaintextHash,
     ciphertextSize,
   };
@@ -270,7 +230,6 @@ export async function decryptAttachmentV2(
 
   let readFd;
   let writeFd;
-  let iv: Uint8Array | undefined;
   try {
     try {
       readFd = await open(ciphertextPath, 'r');
@@ -293,9 +252,7 @@ export async function decryptAttachmentV2(
         getMacAndUpdateHmac(hmac, theirMacValue => {
           theirMac = theirMacValue;
         }),
-        getIvAndDecipher(aesKey, theirIv => {
-          iv = theirIv;
-        }),
+        getIvAndDecipher(aesKey),
         trimPadding(options.size),
         peekAndUpdateHash(plaintextHash),
         writeFd.createWriteStream(),
@@ -340,11 +297,6 @@ export async function decryptAttachmentV2(
     throw new Error(`${logId}: Bad digest`);
   }
 
-  strictAssert(
-    iv != null && iv.byteLength === IV_LENGTH,
-    `${logId}: failed to find their iv`
-  );
-
   if (outerEncryption) {
     strictAssert(outerHmac, 'outerHmac must exist');
 
@@ -366,7 +318,6 @@ export async function decryptAttachmentV2(
 
   return {
     path: relativeTargetPath,
-    iv,
     plaintextHash: ourPlaintextHash,
   };
 }
@@ -453,10 +404,7 @@ export function getMacAndUpdateHmac(
  * Gets the IV from the start of the stream and creates a decipher.
  * Then deciphers the rest of the stream.
  */
-export function getIvAndDecipher(
-  aesKey: Uint8Array,
-  onFoundIv?: (iv: Buffer) => void
-): Transform {
+export function getIvAndDecipher(aesKey: Uint8Array): Transform {
   let maybeIvBytes: Buffer | null = Buffer.alloc(0);
   let decipher: Decipher | null = null;
   return new Transform({
@@ -480,7 +428,6 @@ export function getIvAndDecipher(
         // remainder of the bytes through.
         const iv = maybeIvBytes.subarray(0, IV_LENGTH);
         const remainder = maybeIvBytes.subarray(IV_LENGTH);
-        onFoundIv?.(iv);
         maybeIvBytes = null; // free memory
         decipher = createDecipheriv(CipherType.AES256CBC, aesKey, iv);
         callback(null, decipher.update(remainder));