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/__tests__/Utils/generics.test.ts

@@ -0,0 +1,70 @@
+import { BufferJSON } from '../../Utils/generics'
+
+describe('BufferJSON', () => {
+	const originalObject = {
+		id: 1,
+		key: Buffer.from([1, 2, 3, 4, 5]),
+		nested: {
+			data: Buffer.from([6, 7, 8])
+		}
+	}
+
+	const legacyJsonString = '{"id":1,"key":{"0":1,"1":2,"2":3,"3":4,"4":5},"nested":{"data":{"0":6,"1":7,"2":8}}}'
+
+	it('should correctly perform a round trip (stringify with replacer, parse with reviver)', () => {
+		const serialized = JSON.stringify(originalObject, BufferJSON.replacer)
+
+		expect(serialized).toContain('"type":"Buffer"')
+		expect(serialized).not.toContain('"data":[1,2,3,4,5]')
+
+		const revived = JSON.parse(serialized, BufferJSON.reviver)
+
+		expect(Buffer.isBuffer(revived.key)).toBe(true)
+		expect(Buffer.isBuffer(revived.nested.data)).toBe(true)
+		expect(revived.key).toEqual(originalObject.key)
+		expect(revived).toEqual(originalObject)
+	})
+
+	it('should correctly revive a legacy JSON string with object-like buffers', () => {
+		const revived = JSON.parse(legacyJsonString, BufferJSON.reviver)
+
+		expect(Buffer.isBuffer(revived.key)).toBe(true)
+		expect(Buffer.isBuffer(revived.nested.data)).toBe(true)
+		expect(revived.key).toEqual(originalObject.key)
+		expect(revived.nested.data).toEqual(originalObject.nested.data)
+		expect(revived.id).toEqual(originalObject.id)
+	})
+
+	it('should not corrupt legitimate objects that are not buffers', () => {
+		const legitimateProtoObject = {
+			'0': 'some-value',
+			'1': 'another-value'
+		}
+		const jsonString = JSON.stringify(legitimateProtoObject)
+		const revived = JSON.parse(jsonString, BufferJSON.reviver)
+
+		expect(Buffer.isBuffer(revived)).toBe(false)
+		expect(revived).toEqual(legitimateProtoObject)
+	})
+
+	it('should not convert other objects or null values', () => {
+		const otherObject = {
+			a: 1,
+			b: 2,
+			c: null,
+			d: { '0': 1, foo: 'bar' }
+		}
+		const jsonString = JSON.stringify(otherObject)
+		const revived = JSON.parse(jsonString, BufferJSON.reviver)
+
+		expect(Buffer.isBuffer(revived.a)).toBe(false)
+		expect(revived.c).toBeNull()
+		expect(Buffer.isBuffer(revived.d)).toBe(false)
+		expect(revived).toEqual(otherObject)
+	})
+
+	it('should correctly handle an empty object', () => {
+		const revived = JSON.parse('{}', BufferJSON.reviver)
+		expect(revived).toEqual({})
+	})
+})