fix: allow exporting PeerIds from the keychain (#1546)

We can import a PeerId but not export it, so this PR adds the ability
to export a PeerId.  This is useful for IPNS and other things that
need the ability to act on PeerIds stored in the keychain.

src/keychain/index.ts

@@ -14,6 +14,8 @@ import type { PeerId } from '@libp2p/interface-peer-id'
 import { pbkdf2, randomBytes } from '@libp2p/crypto'
 import type { Startable } from '@libp2p/interfaces/dist/src/startable'
 import type { Datastore } from 'interface-datastore'
+import { peerIdFromKeys } from '@libp2p/peer-id'
+import type { KeyTypes } from '@libp2p/crypto/keys'
 
 const log = logger('libp2p:keychain')
 
@@ -222,7 +224,7 @@ export class KeyChain implements Startable {
    * @param {string} type - One of the key types; 'rsa'.
    * @param {number} [size = 2048] - The key size in bits. Used for rsa keys only
    */
-  async createKey (name: string, type: 'RSA' | 'Ed25519', size = 2048): Promise<KeyInfo> {
+  async createKey (name: string, type: KeyTypes, size = 2048): Promise<KeyInfo> {
     if (!validateKeyName(name) || name === 'self') {
       await randomDelay()
       throw errCode(new Error('Invalid key name'), codes.ERR_INVALID_KEY_NAME)
@@ -432,6 +434,17 @@ export class KeyChain implements Startable {
     }
   }
 
+  /**
+   * Export an existing key as a PeerId
+   */
+  async exportPeerId (name: string) {
+    const password = 'temporary-password'
+    const pem = await this.exportKey(name, password)
+    const privateKey = await importKey(pem, password)
+
+    return await peerIdFromKeys(privateKey.public.bytes, privateKey.bytes)
+  }
+
   /**
    * Import a new key from a PEM encoded PKCS #8 string
    *

test/keychain/keychain.spec.ts

@@ -373,6 +373,14 @@ describe('keychain', () => {
       expect(key.id).to.equal(alice.toString())
     })
 
+    it('private key can be exported', async () => {
+      const alice2 = await ks.exportPeerId('alice')
+
+      expect(alice.equals(alice2)).to.be.true()
+      expect(alice2).to.have.property('privateKey').that.is.ok()
+      expect(alice2).to.have.property('publicKey').that.is.ok()
+    })
+
     it('private key import requires a valid name', async () => {
       // @ts-expect-error invalid parameters
       await expect(ks.importPeer(undefined, alice)).to.eventually.be.rejected.with.property('code', 'ERR_INVALID_KEY_NAME')
@@ -396,6 +404,36 @@ describe('keychain', () => {
       expect(key).to.have.property('name', 'alice')
       expect(key).to.have.property('id', alice.toString())
     })
+
+    it('can create Ed25519 peer id', async () => {
+      const name = 'ed-key'
+      await ks.createKey(name, 'Ed25519')
+      const peer = await ks.exportPeerId(name)
+
+      expect(peer).to.have.property('type', 'Ed25519')
+      expect(peer).to.have.property('privateKey').that.is.ok()
+      expect(peer).to.have.property('publicKey').that.is.ok()
+    })
+
+    it('can create RSA peer id', async () => {
+      const name = 'rsa-key'
+      await ks.createKey(name, 'RSA', 2048)
+      const peer = await ks.exportPeerId(name)
+
+      expect(peer).to.have.property('type', 'RSA')
+      expect(peer).to.have.property('privateKey').that.is.ok()
+      expect(peer).to.have.property('publicKey').that.is.ok()
+    })
+
+    it('can create secp256k1 peer id', async () => {
+      const name = 'secp256k1-key'
+      await ks.createKey(name, 'secp256k1')
+      const peer = await ks.exportPeerId(name)
+
+      expect(peer).to.have.property('type', 'secp256k1')
+      expect(peer).to.have.property('privateKey').that.is.ok()
+      expect(peer).to.have.property('publicKey').that.is.ok()
+    })
   })
 
   describe('rename', () => {