feat(keys): implement generateKeyPairFromSeed for ed25519

Implement generateKeyPairFromSeed for ed25519 - this will produce the same keypair for the same seed (or first 32 bytes of reader) as given to GenerateKeyPairWithReader in go-libp2p.

src/crypto/ed25519.js

@@ -22,6 +22,22 @@ exports.generateKey = function (callback) {
   done(null, keys)
 }
 
+// seed should be a 32 byte uint8array
+exports.generateKeyFromSeed = function (seed, callback) {
+  const done = (err, res) => setImmediate(() => {
+    callback(err, res)
+  })
+
+  let keys
+  try {
+    keys = nacl.sign.keyPair.fromSeed(seed)
+  } catch (err) {
+    done(err)
+    return
+  }
+  done(null, keys)
+}
+
 exports.hashAndSign = function (key, msg, callback) {
   setImmediate(() => {
     callback(null, Buffer.from(nacl.sign.detached(msg, key)))

src/index.js

@@ -30,6 +30,19 @@ exports.generateKeyPair = (type, bits, cb) => {
   key.generateKeyPair(bits, cb)
 }
 
+// Generates a keypair of the given type and bitsize
+// seed is a 32 byte uint8array
+exports.generateKeyPairFromSeed = (type, seed, bits, cb) => {
+  let key = keys[type.toLowerCase()]
+  if (!key) {
+    return cb(new Error('invalid or unsupported key type'))
+  }
+  if (type.toLowerCase() !== 'ed25519') {
+    return cb(new Error('Seed key derivation is unimplemented for RSA or secp256k1'))
+  }
+  key.generateKeyPairFromSeed(seed, bits, cb)
+}
+
 // Converts a protobuf serialized public key into its
 // representative object
 exports.unmarshalPublicKey = (buf) => {

src/keys/ed25519.js

@@ -117,6 +117,27 @@ function generateKeyPair (_bits, cb) {
   })
 }
 
+function generateKeyPairFromSeed (seed, _bits, cb) {
+  if (cb === undefined && typeof _bits === 'function') {
+    cb = _bits
+  }
+
+  crypto.generateKeyFromSeed(seed, (err, keys) => {
+    if (err) {
+      return cb(err)
+    }
+    let privkey
+    try {
+      privkey = new Ed25519PrivateKey(keys.secretKey, keys.publicKey)
+    } catch (err) {
+      cb(err)
+      return
+    }
+
+    cb(null, privkey)
+  })
+}
+
 function ensure (cb) {
   if (typeof cb !== 'function') {
     throw new Error('callback is required')
@@ -138,5 +159,6 @@ module.exports = {
   Ed25519PrivateKey,
   unmarshalEd25519PrivateKey,
   unmarshalEd25519PublicKey,
-  generateKeyPair
+  generateKeyPair,
+  generateKeyPairFromSeed
 }