fix: harden Protobuf Deserialization and Refactor Utilities (#1820)

* refactor: reorganize browser utility functions and improve buffer handling

* fix: harden protobuf deserialization and clean up code

* refactor: simplify data handling in GroupCipher and SenderKey classes

* fix: Ensure consistent Buffer hydration and remove redundant code

* refactor: update decodeAndHydrate calls to use proto types for improved type safety

src/Signal/Group/sender-key-message.ts

@@ -1,5 +1,6 @@
 import { calculateSignature, verifySignature } from 'libsignal/src/curve'
 import { proto } from '../../../WAProto/index.js'
+import { decodeAndHydrate } from '../../Utils/proto-utils'
 import { CiphertextMessage } from './ciphertext-message'
 
 export class SenderKeyMessage extends CiphertextMessage {
@@ -24,16 +25,13 @@ export class SenderKeyMessage extends CiphertextMessage {
 			const version = serialized[0]!
 			const message = serialized.slice(1, serialized.length - this.SIGNATURE_LENGTH)
 			const signature = serialized.slice(-1 * this.SIGNATURE_LENGTH)
-			const senderKeyMessage = proto.SenderKeyMessage.decode(message)
+			const senderKeyMessage = decodeAndHydrate(proto.SenderKeyMessage, message)
 
 			this.serialized = serialized
 			this.messageVersion = (version & 0xff) >> 4
 			this.keyId = senderKeyMessage.id
 			this.iteration = senderKeyMessage.iteration
-			this.ciphertext =
-				typeof senderKeyMessage.ciphertext === 'string'
-					? Buffer.from(senderKeyMessage.ciphertext, 'base64')
-					: senderKeyMessage.ciphertext
+			this.ciphertext = senderKeyMessage.ciphertext
 			this.signature = signature
 		} else {
 			const version = (((this.CURRENT_VERSION << 4) | this.CURRENT_VERSION) & 0xff) % 256