feat(frontend): mob file decryption

frontend/app/player/MessageDistributor/MessageDistributor.ts

@@ -28,6 +28,7 @@ import AssistManager from './managers/AssistManager';
 
 import MFileReader from './messages/MFileReader';
 import { loadFiles, requestEFSDom, requestEFSDevtools } from './network/loadFiles';
+import { decryptSessionBytes } from './network/crypto';
 
 import { INITIAL_STATE as SUPER_INITIAL_STATE, State as SuperState } from './StatedScreen/StatedScreen';
 import { INITIAL_STATE as ASSIST_INITIAL_STATE, State as AssistState } from './managers/AssistManager';
@@ -215,14 +216,17 @@ export default class MessageDistributor extends StatedScreen {
   }
 
   private loadMessages() { 
-    const createNewParser = () => {
+    const createNewParser = (shouldDecrypt=true) => {
+      const decrypt = shouldDecrypt && this.session.fileKey
+        ? (b: Uint8Array) => decryptSessionBytes(b, this.session.fileKey)
+        : (b: Uint8Array) => Promise.resolve(b)
       // Each time called - new fileReader created
       const fileReader = new MFileReader(new Uint8Array(), this.sessionStart)
-      return (b: Uint8Array) => {
+      return (b: Uint8Array) => decrypt(b).then(b => {
         fileReader.append(b)
         this.parseAndDistributeMessages(fileReader)
         this.setMessagesLoading(false)
-      }
+      })
     }
     this.setMessagesLoading(true)
     this.waitingForFiles = true
@@ -230,7 +234,7 @@ export default class MessageDistributor extends StatedScreen {
     loadFiles(this.session.domURL, createNewParser())
     .catch(() => // do if  only the first file missing (404) (?)
       requestEFSDom(this.session.sessionId)
-        .then(createNewParser())
+        .then(createNewParser(false))
         // Fallback to back Compatability with mobsUrl
         .catch(e =>
           loadFiles(this.session.mobsUrl, createNewParser())
@@ -245,7 +249,7 @@ export default class MessageDistributor extends StatedScreen {
     loadFiles(this.session.devtoolsURL, createNewParser())
     .catch(() =>
       requestEFSDevtools(this.session.sessionId)
-        .then(createNewParser())
+        .then(createNewParser(false))
     )
     //.catch() // not able to download the devtools file
     .finally(() => update({ devtoolsLoading: false }))

frontend/app/player/MessageDistributor/network/crypto.ts

@@ -0,0 +1,28 @@
+
+
+const u8aFromHex = (hexString:string) =>
+  Uint8Array.from(hexString.match(/.{1,2}/g).map((byte) => parseInt(byte, 16)))
+
+const is16BitHex = (maybeHex: string | undefined) =>
+  maybeHex && maybeHex.length % 2 === 0 && !/[^a-fA-F0-9]/u.test(maybeHex)
+
+
+function truncPadding(padded: Uint8Array): Uint8Array {
+	let i = padded.length - 1
+	for (; !padded[i] ;i--) {}
+	return padded.subarray(0, i)
+}
+
+export function decryptSessionBytes(cypher: Uint8Array, keyString: string): Promise<Uint8Array> {
+	const [hexKey, hexIV] = keyString.split(",")
+	if (!is16BitHex(hexIV) || !is16BitHex(hexKey)) {
+		return Promise.reject("Wrong key/iv pair")
+	}
+	const iv = u8aFromHex(hexIV)
+	const byteKey = u8aFromHex(hexKey)
+	return crypto.subtle.importKey("raw",byteKey, { name: "AES-CBC" }, false, ["decrypt"])
+		.then(key => crypto.subtle.decrypt({ name: "AES-CBC", iv: iv}, key, cypher))
+		.then(truncPadding)
+}
+
+

frontend/app/types/session/session.ts

@@ -83,6 +83,7 @@ export default Record({
   agentToken: '',
   notes: [],
   notesWithEvents: [],
+  fileKey: '',
 }, {
   fromJS:({
     startTs=0,