HDNode: enforces sane seed lengths

src/hdnode.js

@@ -51,6 +51,10 @@ HDNode.HIGHEST_BIT = 0x80000000
 HDNode.LENGTH = 78
 
 HDNode.fromSeedBuffer = function(seed, network) {
+  assert(Buffer.isBuffer(seed), 'Expected Buffer, got' + seed)
+  assert(seed.length >= 16, 'Seed should be atleast 128 bits')
+  assert(seed.length <= 64, 'Seed should be atmost 512 bits')
+
   var I = crypto.HmacSHA512(seed, HDNode.MASTER_SECRET)
   var IL = I.slice(0, 32)
   var IR = I.slice(32)

test/hdnode.js

@@ -65,6 +65,18 @@ describe('HDNode', function() {
         assert.equal(hd.chainCode.toString('hex'), f.master.chainCode)
       })
     })
+
+    it('throws on low entropy seed', function() {
+      assert.throws(function() {
+        HDNode.fromSeedHex('ffffffffff')
+      }, /Seed should be atleast 128 bits/)
+    })
+
+    it('throws on too high entropy seed', function() {
+      assert.throws(function() {
+        HDNode.fromSeedHex('ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff')
+      }, /Seed should be atmost 512 bits/)
+    })
   })
 
   describe('toBase58', function() {