elliptic: fix key verification in loadCompressedPublicKey

Author: ChALkeR

lib/elliptic.js

@@ -18,6 +18,10 @@ function loadCompressedPublicKey (first, xbuf) {
   let 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 } })
 }
 

package.json

@@ -40,7 +40,7 @@
     "node-gyp": "=10.1.0",
     "nyc": "^15.0.0",
     "prebuildify": "^6.0.1",
-    "prebuildify-cross": "github:fanatid/prebuildify-cross#9f7af67698f06e07d42304d9813a6f19aee5812c",
+    "prebuildify-cross": "^5.1.1",
     "standard": "^14.3.1",
     "tap-dot": "^2.0.0",
     "tape": "^4.10.1",

test/publickey.js

@@ -32,6 +32,12 @@ module.exports = (t, secp256k1) => {
       invalidLength[0] = publicKey.compressed[0]
       t.false(secp256k1.publicKeyVerify(invalidLength), 'invalid length')
 
+      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()
     })