Merge pull request #171 from ethereumjs/fix-isValidSignature-method

Fix isValidSignature method

index.js

@@ -571,15 +571,16 @@ exports.addHexPrefix = function (str) {
 /**
  * Validate ECDSA signature
  * @method isValidSignature
- * @param {Buffer} v
+ * @param {Number} v
  * @param {Buffer} r
  * @param {Buffer} s
- * @param {Boolean} [homestead=true]
+ * @param {Boolean} [homesteadOrLater=true] Indicates whether this is being used on either the homestead hardfork or a later one
  * @param {Number} [chainId]
  * @return {Boolean}
  */
 
-exports.isValidSignature = function (v, r, s, homestead, chainId) {
+exports.isValidSignature = function (v, r, s, homesteadOrLater, chainId) {
+  homesteadOrLater = homesteadOrLater === undefined ? true : homesteadOrLater
   const SECP256K1_N_DIV_2 = new BN('7fffffffffffffffffffffffffffffff5d576e7357a4501ddfe92f46681b20a0', 16)
   const SECP256K1_N = new BN('fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141', 16)
 
@@ -598,7 +599,7 @@ exports.isValidSignature = function (v, r, s, homestead, chainId) {
     return false
   }
 
-  if ((homestead === false) && (new BN(s).cmp(SECP256K1_N_DIV_2) === 1)) {
+  if (homesteadOrLater && (new BN(s).cmp(SECP256K1_N_DIV_2) === 1)) {
     return false
   }
 

test/index.js

@@ -558,6 +558,24 @@ describe('isValidSignature', function () {
     const s = Buffer.from('129ff05af364204442bdb53ab6f18a99ab48acc9326fa689f228040429e3ca66', 'hex')
     assert.equal(ethUtils.isValidSignature(29, r, s), false)
   })
+  it('should fail when on homestead and s > secp256k1n/2', function () {
+    const SECP256K1_N_DIV_2 = new BN('7fffffffffffffffffffffffffffffff5d576e7357a4501ddfe92f46681b20a0', 16)
+
+    const r = Buffer.from('99e71a99cb2270b8cac5254f9e99b6210c6c10224a1579cf389ef88b20a1abe9', 'hex')
+    const s = Buffer.from(SECP256K1_N_DIV_2.add(new BN('1', 16)).toString(16), 'hex')
+
+    const v = 27
+    assert.equal(ethUtils.isValidSignature(v, r, s, true), false)
+  })
+  it('should not fail when not on homestead but s > secp256k1n/2', function () {
+    const SECP256K1_N_DIV_2 = new BN('7fffffffffffffffffffffffffffffff5d576e7357a4501ddfe92f46681b20a0', 16)
+
+    const r = Buffer.from('99e71a99cb2270b8cac5254f9e99b6210c6c10224a1579cf389ef88b20a1abe9', 'hex')
+    const s = Buffer.from(SECP256K1_N_DIV_2.add(new BN('1', 16)).toString(16), 'hex')
+
+    const v = 27
+    assert.equal(ethUtils.isValidSignature(v, r, s, false), true)
+  })
   it('should work otherwise', function () {
     const r = Buffer.from('99e71a99cb2270b8cac5254f9e99b6210c6c10224a1579cf389ef88b20a1abe9', 'hex')
     const s = Buffer.from('129ff05af364204442bdb53ab6f18a99ab48acc9326fa689f228040429e3ca66', 'hex')