Add getOwnDMKey function

README.md

@@ -63,11 +63,12 @@ sbot.db.create(
 Adding this module as a secret-stack plugin means that you can use these methods
 on the `sbot.box2` namespace:
 
-- `setOwnDMKey(key)`: Adds a `key` (a buffer) to the list of keys that can be
+- `setOwnDMKey(key)`: Sets a `key` (a buffer) as the key that will be
   used to encrypt messages to yourself. By specifying the direct message (DM)
   for yourself, you are free to supply that from any source. The key you provide
   _will_ be persisted locally. For direct messaging other feeds, a key is
   automatically derived.
+- `getOwnDMKey(cb)`: Gets the key that would be used for DM'ing yourself. On the format `{ key, scheme }`.
 - `addGroupInfo(groupId, addInfo, cb)`: `groupId` must be a cloaked message Id or a uri encoded group and `addInfo` must be an object. Can be called multiple times to add multiple read keys. The first key that is added will automatically also be set as the write key. To change the write key, use `pickGroupWriteKey`. If you add a key to an excluded group, the group will be un-excluded. Returns a promise if cb isn't provided. `addInfo` can have these keys:
   - `key` must be a buffer. The key can then be used for decrypting messages from the group, and if picked with `pickGroupWriteKey`, as a "recp" to encrypt messages to the group. Note that the keys are not persisted in this module.
   - `scheme` _String_ - scheme of that encryption key (optional, there is only one option at the moment which we default to)

format.js

@@ -84,6 +84,12 @@ function makeEncryptionFormat() {
     })
   }
 
+  function getOwnDMKey(cb) {
+    keyringReady.onReady(() => {
+      cb(null, keyring.self.get())
+    })
+  }
+
   function addDMPairSync(myKeys, theirId) {
     if (!keyringReady.ready) throw new Error('keyring not ready')
     const myId = myKeys.id
@@ -405,6 +411,7 @@ function makeEncryptionFormat() {
     decrypt,
     // ssb-box2 specific APIs:
     setOwnDMKey,
+    getOwnDMKey,
     addGroupInfo,
     pickGroupWriteKey,
     excludeGroupInfo,

index.js

@@ -27,6 +27,7 @@ exports.init = function (ssb, config) {
 
   return {
     setOwnDMKey: encryptionFormat.setOwnDMKey,
+    getOwnDMKey: encryptionFormat.getOwnDMKey,
     canDM: encryptionFormat.canDM,
     addGroupInfo: encryptionFormat.addGroupInfo,
     pickGroupWriteKey: encryptionFormat.pickGroupWriteKey,

test/index.js

@@ -2,6 +2,7 @@
 //
 // SPDX-License-Identifier: Unlicense
 
+const { promisify: p } = require('util')
 const test = require('tape')
 const { check } = require('ssb-encryption-format')
 const ssbKeys = require('ssb-keys')
@@ -213,6 +214,25 @@ test('cannot decrypt own DM after we changed our own DM keys', (t) => {
   })
 })
 
+test('can get own self dm key', async (t) => {
+  const box2 = Box2()
+  const keys = ssbKeys.generate(null, 'alice', 'buttwoo-v1')
+
+  await p(box2.setup)({ keys })
+
+  const ownKey = Buffer.from(
+    '30720d8f9cbf37f6d7062826f6decac93e308060a8aaaa77e6a4747f40ee1a76',
+    'hex'
+  )
+
+  box2.setOwnDMKey(ownKey)
+
+  const gottenKey = await p(box2.getOwnDMKey)()
+
+  t.equal(gottenKey.key, ownKey, 'got correct key')
+  t.equal(gottenKey.scheme, keySchemes.feed_id_self, 'got correct scheme')
+})
+
 test('cannot encrypt to zero valid recipients', (t) => {
   const box2 = Box2()
   const keys = ssbKeys.generate(null, 'alice', 'buttwoo-v1')
@@ -367,30 +387,34 @@ test('decrypt as pobox recipient', (t) => {
   const testkey = poBoxDH.toBuffer().secret
 
   box2.setup({ keys }, () => {
-    box2.addPoBox(poBoxId, {
-      key: testkey,
-    }, (err) => {
-      t.error(err, "added pobox key")
-
-      const opts = {
-        keys,
-        content: { type: 'post', text: 'super secret' },
-        previous: null,
-        timestamp: 12345678900,
-        tag: buttwoo.tags.SSB_FEED,
-        hmacKey: null,
-        recps: [poBoxId, ssbKeys.generate(null, '2').id],
+    box2.addPoBox(
+      poBoxId,
+      {
+        key: testkey,
+      },
+      (err) => {
+        t.error(err, 'added pobox key')
+
+        const opts = {
+          keys,
+          content: { type: 'post', text: 'super secret' },
+          previous: null,
+          timestamp: 12345678900,
+          tag: buttwoo.tags.SSB_FEED,
+          hmacKey: null,
+          recps: [poBoxId, ssbKeys.generate(null, '2').id],
+        }
+
+        const plaintext = buttwoo.toPlaintextBuffer(opts)
+        t.true(Buffer.isBuffer(plaintext), 'plaintext is a buffer')
+
+        const ciphertext = box2.encrypt(plaintext, opts)
+
+        const decrypted = box2.decrypt(ciphertext, { ...opts, author: keys.id })
+        t.deepEqual(decrypted, plaintext, 'decrypted plaintext is the same')
+
+        t.end()
       }
-
-      const plaintext = buttwoo.toPlaintextBuffer(opts)
-      t.true(Buffer.isBuffer(plaintext), 'plaintext is a buffer')
-
-      const ciphertext = box2.encrypt(plaintext, opts)
-
-      const decrypted = box2.decrypt(ciphertext, { ...opts, author: keys.id })
-      t.deepEqual(decrypted, plaintext, 'decrypted plaintext is the same')
-
-      t.end()
-    })
+    )
   })
-})
+})