add function to extract MLS external group

core/node/events/stream_viewstate_mls.go

@@ -77,6 +77,8 @@ func (r *streamViewImpl) GetMlsGroupState() (*mls_tools.MlsGroupState, error) {
 					mlsGroupState.ExternalGroupSnapshot = content.Mls.GetInitializeGroup().ExternalGroupSnapshot
 				case *protocol.MemberPayload_Mls_ExternalJoin_:
 					mlsGroupState.Commits = append(mlsGroupState.Commits, content.Mls.GetExternalJoin().Commit)
+				case *protocol.MemberPayload_Mls_WelcomeMessage_:
+					mlsGroupState.Commits = append(mlsGroupState.Commits, content.Mls.GetWelcomeMessage().Commit)
 				default:
 					break
 				}

packages/sdk/src/client.ts

@@ -152,6 +152,7 @@ import { SignerContext } from './signerContext'
 import { decryptAESGCM, deriveKeyAndIV, encryptAESGCM, uint8ArrayToBase64 } from './crypto_utils'
 import { makeTags, makeTipTags } from './tags'
 import { TipEventObject } from '@river-build/generated/dev/typings/ITipping'
+import { extractMlsExternalGroup } from './mls/utils/mlsutils'
 
 export type ClientEvents = StreamEvents & DecryptionEvents
 
@@ -2525,6 +2526,19 @@ export class Client
             method: 'mls',
         })
     }
+
+    public async getMlsExternalGroupInfo(streamId: string): Promise<{
+        externalGroupSnapshot: Uint8Array
+        groupInfoMessage: Uint8Array
+        commits: { commit: Uint8Array; groupInfoMessage: Uint8Array }[]
+    }> {
+        let streamView = this.stream(streamId)?.view
+        if (!streamView || !streamView.isInitialized) {
+            streamView = await this.getStream(streamId)
+        }
+        check(isDefined(streamView), `stream not found: ${streamId}`)
+        return extractMlsExternalGroup(streamView)
+    }
 }
 
 function ensureNoHexPrefix(value: string): string {

packages/sdk/src/mls/utils/mlsutils.ts

@@ -0,0 +1,57 @@
+import { check } from '@river-build/dlog'
+import { IStreamStateView } from '../../streamStateView'
+
+export function extractMlsExternalGroup(streamView: IStreamStateView): {
+    externalGroupSnapshot: Uint8Array
+    groupInfoMessage: Uint8Array
+    commits: { commit: Uint8Array; groupInfoMessage: Uint8Array }[]
+} {
+    const indexOfLastSnapshot = streamView.timeline.findLastIndex((event) => {
+        const payload = event.remoteEvent?.event.payload
+        if (payload?.case !== 'miniblockHeader') {
+            return false
+        }
+        return payload.value.snapshot !== undefined
+    })
+
+    const payload = streamView.timeline[indexOfLastSnapshot].remoteEvent?.event.payload
+    check(payload?.case === 'miniblockHeader', 'no snapshot found')
+    const snapshot = payload.value.snapshot
+    check(snapshot !== undefined, 'no snapshot found')
+    const externalGroupSnapshot = snapshot.members?.mls?.externalGroupSnapshot
+    check(externalGroupSnapshot !== undefined, 'no externalGroupSnapshot found')
+    const groupInfoMessage = snapshot.members?.mls?.groupInfoMessage
+    check(groupInfoMessage !== undefined, 'no groupInfoMessage found')
+    const commits: { commit: Uint8Array; groupInfoMessage: Uint8Array }[] = []
+    for (let i = indexOfLastSnapshot; i < streamView.timeline.length; i++) {
+        const event = streamView.timeline[i]
+        const payload = event.remoteEvent?.event.payload
+        if (payload?.case !== 'memberPayload') {
+            continue
+        }
+        if (payload?.value?.content.case !== 'mls') {
+            continue
+        }
+
+        const mlsPayload = payload.value.content.value
+        switch (mlsPayload.content.case) {
+            case 'externalJoin':
+                commits.push({
+                    commit: mlsPayload.content.value.commit,
+                    groupInfoMessage: mlsPayload.content.value.groupInfoMessage,
+                })
+                break
+            case 'welcomeMessage':
+                commits.push({
+                    commit: mlsPayload.content.value.commit,
+                    groupInfoMessage: mlsPayload.content.value.groupInfoMessage,
+                })
+                break
+            case undefined:
+                break
+            default:
+                break
+        }
+    }
+    return { externalGroupSnapshot, groupInfoMessage, commits: commits }
+}

packages/sdk/src/tests/multi_ne/mls.test.ts

@@ -187,7 +187,7 @@ describe('mlsTests', () => {
         client: MlsClient,
         groupInfoMessage: Uint8Array,
         externalGroupSnapshot: Uint8Array,
-    ): Promise<{ commit: Uint8Array; groupInfoMessage: Uint8Array }> {
+    ): Promise<{ commit: Uint8Array; groupInfoMessage: Uint8Array; group: MlsGroup }> {
         const externalClient = new ExternalClient()
         const externalSnapshot = ExternalSnapshot.fromBytes(externalGroupSnapshot)
         const externalGroup = await externalClient.loadGroup(externalSnapshot)
@@ -201,6 +201,7 @@ describe('mlsTests', () => {
         return {
             commit: commitOutput.commit.toBytes(),
             groupInfoMessage: updatedGroupInfoMessage.toBytes(),
+            group: commitOutput.group,
         }
     }
 
@@ -566,6 +567,7 @@ describe('mlsTests', () => {
         await expect(
             bobMlsGroup.processIncomingMessage(commitOutput.commitMessage),
         ).resolves.not.toThrow()
+        latestGroupInfoMessage = groupInfoMessage!.toBytes()
         commits.push(commit)
     })
 
@@ -587,6 +589,53 @@ describe('mlsTests', () => {
         })
     })
 
+    test('correct external group info is returned', async () => {
+        const externalGroupInfo = await bobClient.getMlsExternalGroupInfo(streamId)
+        const externalClient = new ExternalClient()
+        const externalGroupSnapshot = ExternalSnapshot.fromBytes(
+            externalGroupInfo.externalGroupSnapshot,
+        )
+        expect(externalGroupInfo.commits.length).toBe(1)
+
+        let latestValidGroupInfoMessage = externalGroupInfo.groupInfoMessage
+        const externalGroup = await externalClient.loadGroup(externalGroupSnapshot)
+        for (const commit of externalGroupInfo.commits) {
+            try {
+                const mlsMessage = MlsMessage.fromBytes(commit.commit)
+                await externalGroup.processIncomingMessage(mlsMessage)
+                latestValidGroupInfoMessage = commit.groupInfoMessage
+            } catch {
+                // catch, in case this is an invalid commit
+            }
+        }
+
+        expect(bin_equal(latestValidGroupInfoMessage, latestGroupInfoMessage)).toBe(true)
+
+        const aliceThrowawayClient = await MlsClient.create(new Uint8Array(randomBytes(32)))
+        const {
+            commit: aliceCommit,
+            groupInfoMessage: aliceGroupInfoMessage,
+            group: aliceGroup,
+        } = await commitExternal(
+            aliceThrowawayClient,
+            latestValidGroupInfoMessage,
+            externalGroup.snapshot().toBytes(),
+        )
+        const aliceMlsPayload = makeMlsPayloadExternalJoin(
+            aliceThrowawayClient.signaturePublicKey(),
+            aliceCommit,
+            aliceGroupInfoMessage,
+        )
+
+        await expect(
+            bobMlsGroup.processIncomingMessage(MlsMessage.fromBytes(aliceCommit)),
+        ).resolves.not.toThrow()
+
+        expect(bobMlsGroup.currentEpoch).toBe(aliceGroup.currentEpoch)
+        await expect(aliceClient._debugSendMls(streamId, aliceMlsPayload)).resolves.not.toThrow()
+        commits.push(aliceCommit)
+    })
+
     test('devices added from key packages are snapshotted', async () => {
         // force snapshot
         await expect(
@@ -596,6 +645,6 @@ describe('mlsTests', () => {
         // verify that the key package is picked up in the snapshot
         const streamAfterSnapshot = await bobClient.getStream(streamId)
         const mls = streamAfterSnapshot.membershipContent.mls
-        expect(mls.members[aliceClient.userId].signaturePublicKeys.length).toBe(2)
+        expect(mls.members[aliceClient.userId].signaturePublicKeys.length).toBe(3)
     })
 })