elliptic: fix key verification in loadCompressedPublicKey

Author: ChALkeR

lib/elliptic/index.js

@@ -20,6 +20,10 @@ function loadCompressedPublicKey (first, xBuffer) {
   var y = x.redSqr().redIMul(x).redIAdd(ecparams.b).redSqrt()
   if ((first === 0x03) !== y.isOdd()) y = y.redNeg()
 
+  // x*x*x + b = y*y
+  const x3 = x.redSqr().redIMul(x)
+  if (!y.redSqr().redISub(x3.redIAdd(ecparams.b)).isZero()) return null
+
   return ec.keyPair({ pub: { x: x, y: y } })
 }
 

test/publickey.js

@@ -171,6 +171,16 @@ module.exports = function (t, secp256k1) {
       t.end()
     })
 
+    t.test('zero key', function (t) {
+      const zeroUncompressed = Buffer.concat([Buffer.from([0x04]), Buffer.alloc(64)])
+      t.false(secp256k1.publicKeyVerify(zeroUncompressed), 'zero uncompressed')
+
+      const zeroCompressed = Buffer.concat([Buffer.from([0x02]), Buffer.alloc(32)])
+      t.false(secp256k1.publicKeyVerify(zeroCompressed), 'zero compressed')
+
+      t.end();
+    })
+
     util.repeat(t, 'random tests', util.env.repeat, function (t) {
       var privateKey = util.getPrivateKey()
       var publicKey = util.getPublicKey(privateKey)