Merge pull request #177 from xmtp/negotiated-topic-invitation-class

Negotiated topic invitation classes

Author: neekolas

src/ApiClient.ts

@@ -1,7 +1,6 @@
 import { messageApi } from '@xmtp/proto'
 import { NotifyStreamEntityArrival } from '@xmtp/proto/ts/dist/types/fetch.pb'
-import { retry, sleep } from './utils'
-import Long from 'long'
+import { dateToNs, retry, sleep } from './utils'
 import AuthCache from './authn/AuthCache'
 import { Authenticator } from './authn'
 import { version } from '../package.json'
@@ -48,7 +47,7 @@ export type SubscribeCallback = NotifyStreamEntityArrival<messageApi.Envelope>
 export type UnsubscribeFn = () => Promise<void>
 
 const toNanoString = (d: Date | undefined): undefined | string => {
-  return d && Long.fromNumber(d.valueOf()).multiply(1_000_000).toString()
+  return d && dateToNs(d).toString()
 }
 
 const isAbortError = (err?: Error): boolean => {

src/Invitation.ts

@@ -0,0 +1,202 @@
+import Long from 'long'
+import { SignedPublicKeyBundle } from './crypto/PublicKeyBundle'
+import { invitation } from '@xmtp/proto'
+import Ciphertext from './crypto/Ciphertext'
+import { decrypt, encrypt } from './crypto'
+import { PrivateKeyBundleV2 } from './crypto/PrivateKeyBundle'
+import { dateToNs } from './utils'
+
+/**
+ * InvitationV1 is a protobuf message to be encrypted and used as the ciphertext in a SealedInvitationV1 message
+ */
+export class InvitationV1 implements invitation.InvitationV1 {
+  topic: string
+  aes256GcmHkdfSha256: invitation.InvitationV1_Aes256gcmHkdfsha256 // eslint-disable-line camelcase
+
+  constructor({ topic, aes256GcmHkdfSha256 }: invitation.InvitationV1) {
+    if (!topic || !topic.length) {
+      throw new Error('Missing topic')
+    }
+    if (
+      !aes256GcmHkdfSha256 ||
+      !aes256GcmHkdfSha256.keyMaterial ||
+      !aes256GcmHkdfSha256.keyMaterial.length
+    ) {
+      throw new Error('Missing key material')
+    }
+    this.topic = topic
+    this.aes256GcmHkdfSha256 = aes256GcmHkdfSha256
+  }
+
+  toBytes(): Uint8Array {
+    return invitation.InvitationV1.encode(this).finish()
+  }
+
+  static fromBytes(bytes: Uint8Array): InvitationV1 {
+    return new InvitationV1(invitation.InvitationV1.decode(bytes))
+  }
+}
+
+/**
+ * SealedInvitationHeaderV1 is a protobuf message to be used as the headerBytes in a SealedInvitationV1
+ */
+export class SealedInvitationHeaderV1
+  implements invitation.SealedInvitationHeaderV1
+{
+  sender: SignedPublicKeyBundle
+  recipient: SignedPublicKeyBundle
+  createdNs: Long
+
+  constructor({
+    sender,
+    recipient,
+    createdNs,
+  }: invitation.SealedInvitationHeaderV1) {
+    if (!sender) {
+      throw new Error('Missing sender')
+    }
+    if (!recipient) {
+      throw new Error('Missing recipient')
+    }
+    this.sender = new SignedPublicKeyBundle(sender)
+    this.recipient = new SignedPublicKeyBundle(recipient)
+    this.createdNs = createdNs
+  }
+
+  toBytes(): Uint8Array {
+    return invitation.SealedInvitationHeaderV1.encode(this).finish()
+  }
+
+  static fromBytes(bytes: Uint8Array): SealedInvitationHeaderV1 {
+    return new SealedInvitationHeaderV1(
+      invitation.SealedInvitationHeaderV1.decode(bytes)
+    )
+  }
+}
+
+export class SealedInvitationV1 implements invitation.SealedInvitationV1 {
+  headerBytes: Uint8Array
+  ciphertext: Ciphertext
+  private _header?: SealedInvitationHeaderV1
+  private _invitation?: InvitationV1
+
+  constructor({ headerBytes, ciphertext }: invitation.SealedInvitationV1) {
+    if (!headerBytes || !headerBytes.length) {
+      throw new Error('Missing header bytes')
+    }
+    if (!ciphertext) {
+      throw new Error('Missing ciphertext')
+    }
+    this.headerBytes = headerBytes
+    this.ciphertext = new Ciphertext(ciphertext)
+  }
+
+  /**
+   * Accessor method for the full header object
+   */
+  get header(): SealedInvitationHeaderV1 {
+    // Use cached value if already exists
+    if (this._header) {
+      return this._header
+    }
+    this._header = SealedInvitationHeaderV1.fromBytes(this.headerBytes)
+    return this._header
+  }
+
+  /**
+   * getInvitation decrypts and returns the InvitationV1 stored in the ciphertext of the Sealed Invitation
+   */
+  async getInvitation(viewer: PrivateKeyBundleV2): Promise<InvitationV1> {
+    // Use cached value if already exists
+    if (this._invitation) {
+      return this._invitation
+    }
+    // The constructors for child classes will validate that this is complete
+    const header = this.header
+    let secret: Uint8Array
+    if (viewer.identityKey.matches(this.header.sender.identityKey)) {
+      secret = await viewer.sharedSecret(
+        header.recipient,
+        header.sender.preKey,
+        false
+      )
+    } else {
+      secret = await viewer.sharedSecret(
+        header.sender,
+        header.recipient.preKey,
+        true
+      )
+    }
+
+    const decryptedBytes = await decrypt(
+      this.ciphertext,
+      secret,
+      this.headerBytes
+    )
+    this._invitation = InvitationV1.fromBytes(decryptedBytes)
+    return this._invitation
+  }
+
+  toBytes(): Uint8Array {
+    return invitation.SealedInvitationV1.encode(this).finish()
+  }
+
+  static fromBytes(bytes: Uint8Array): SealedInvitationV1 {
+    return new SealedInvitationV1(invitation.SealedInvitationV1.decode(bytes))
+  }
+}
+
+/**
+ * Wrapper class for SealedInvitationV1 and any future iterations of SealedInvitation
+ */
+export class SealedInvitation implements invitation.SealedInvitation {
+  v1: SealedInvitationV1
+
+  constructor({ v1 }: invitation.SealedInvitation) {
+    if (!v1) {
+      throw new Error('Missing v1 invitation')
+    }
+    this.v1 = new SealedInvitationV1(v1)
+  }
+
+  toBytes(): Uint8Array {
+    return invitation.SealedInvitation.encode(this).finish()
+  }
+
+  static fromBytes(bytes: Uint8Array): SealedInvitation {
+    return new SealedInvitation(invitation.SealedInvitation.decode(bytes))
+  }
+
+  /**
+   * Create a SealedInvitation with a SealedInvitationV1 payload
+   * Will encrypt all contents and validate inputs
+   */
+  static async createV1({
+    sender,
+    recipient,
+    created,
+    invitation,
+  }: {
+    sender: PrivateKeyBundleV2
+    recipient: SignedPublicKeyBundle
+    created: Date
+    invitation: InvitationV1
+  }): Promise<SealedInvitation> {
+    const headerBytes = new SealedInvitationHeaderV1({
+      sender: sender.getPublicKeyBundle(),
+      recipient,
+      createdNs: dateToNs(created),
+    }).toBytes()
+
+    const secret = await sender.sharedSecret(
+      recipient,
+      sender.getCurrentPreKey().publicKey,
+      false
+    )
+
+    const invitationBytes = invitation.toBytes()
+    const ciphertext = await encrypt(invitationBytes, secret, headerBytes)
+
+    return new SealedInvitation({ v1: { headerBytes, ciphertext } })
+  }
+}

src/Message.ts

@@ -124,7 +124,7 @@ export default class Message implements proto.MessageV1 {
     const headerBytes = proto.MessageHeaderV1.encode(header).finish()
     const ciphertext = await encrypt(message, secret, headerBytes)
     const protoMsg = {
-      v1: { headerBytes: headerBytes, ciphertext },
+      v1: { headerBytes, ciphertext },
       v2: undefined,
     }
     const bytes = proto.Message.encode(protoMsg).finish()

src/authn/AuthData.ts

@@ -1,5 +1,6 @@
 import { authn as authnProto } from '@xmtp/proto'
 import Long from 'long'
+import { dateToNs } from '../utils'
 
 export default class AuthData implements authnProto.AuthData {
   walletAddr: string
@@ -13,8 +14,8 @@ export default class AuthData implements authnProto.AuthData {
   static create(walletAddr: string, timestamp?: Date): AuthData {
     timestamp = timestamp || new Date()
     return new AuthData({
-      walletAddr: walletAddr,
-      createdNs: Long.fromNumber(timestamp.getTime()).multiply(1_000_000),
+      walletAddr,
+      createdNs: dateToNs(timestamp),
     })
   }
 

src/crypto/PrivateKey.ts

@@ -237,7 +237,7 @@ export class PrivateKey implements privateKey.PrivateKey {
 
   // derive shared secret from peer's PublicKey;
   // the peer can derive the same secret using their PrivateKey and our PublicKey
-  sharedSecret(peer: PublicKey): Uint8Array {
+  sharedSecret(peer: PublicKey | SignedPublicKey): Uint8Array {
     return secp.getSharedSecret(
       this.secp256k1.bytes,
       peer.secp256k1Uncompressed.bytes,

src/crypto/PrivateKeyBundle.ts

@@ -193,7 +193,7 @@ export class PrivateKeyBundleV1 implements proto.PrivateKeyBundleV1 {
   // @myPreKey indicates which of my preKeys should be used to derive the secret
   // @recipient indicates if this is the sending or receiving side.
   async sharedSecret(
-    peer: PublicKeyBundle,
+    peer: PublicKeyBundle | SignedPublicKeyBundle,
     myPreKey: PublicKey,
     isRecipient: boolean
   ): Promise<Uint8Array> {

src/utils.ts

@@ -1,3 +1,5 @@
+import Long from 'long'
+
 export type IsRetryable = (err?: Error) => boolean
 
 export const buildContentTopic = (name: string): string =>
@@ -70,3 +72,7 @@ export async function retry<T extends (...arg0: any[]) => any>(
     return retry(fn, args, maxRetries, sleepTime, isRetryableFn, currRetry + 1)
   }
 }
+
+export function dateToNs(date: Date): Long {
+  return Long.fromNumber(date.valueOf()).multiply(1_000_000)
+}

test/ApiClient.test.ts

@@ -6,6 +6,7 @@ import { sleep } from './helpers'
 import { Authenticator } from '../src/authn'
 import { PrivateKey } from '../src'
 import { version } from '../package.json'
+import { dateToNs } from '../src/utils'
 const { MessageApi } = messageApi
 
 const PATH_PREFIX = 'http://fake:5050'
@@ -165,9 +166,7 @@ describe('Publish', () => {
         {
           message: msg.message,
           contentTopic: msg.contentTopic,
-          timestampNs: Long.fromNumber(now.valueOf())
-            .multiply(1_000_000)
-            .toString(),
+          timestampNs: dateToNs(now).toString(),
         },
       ],
     }