Merge pull request #8 from 0xProject/isSignatureValid

Add isSignatureValid method and tests for it

2 files changed, 39 insertions, 3 deletions

diff --git a/src/ts/0x.js.ts b/src/ts/0x.js.ts
index 95446ad74..dd67c49a0 100644
--- a/src/ts/0x.js.ts
+++ b/src/ts/0x.js.ts
@@ -1,6 +1,31 @@
+import * as ethUtil from 'ethereumjs-util';
+
+/**
+ * Elliptic Curve signature
+ */
+export interface ECSignature {
+    v: number;
+    r: string;
+    s: string;
+}
+
 export class ZeroEx {
-    /** Verifies the signature */
-    public verifySignature() {
-        // TODO
+    /**
+     * Verifies that the elliptic curve signature `signature` was generated
+     * by signing `data` with the private key corresponding to the `signer` address.
+     */
+    public static isValidSignature(data: string, signature: ECSignature, signer: ETHAddressHex): boolean {
+        const dataBuff = ethUtil.toBuffer(data);
+        const msgHashBuff = ethUtil.hashPersonalMessage(dataBuff);
+        try {
+            const pubKey = ethUtil.ecrecover(msgHashBuff,
+                signature.v,
+                ethUtil.toBuffer(signature.r),
+                ethUtil.toBuffer(signature.s));
+            const retrievedAddress = ethUtil.bufferToHex(ethUtil.pubToAddress(pubKey));
+            return retrievedAddress === signer;
+        } catch (err) {
+            return false;
+        }
     }
 }
diff --git a/src/ts/globals.d.ts b/src/ts/globals.d.ts
new file mode 100644
index 000000000..0f7391b39
--- /dev/null
+++ b/src/ts/globals.d.ts
@@ -0,0 +1,11 @@
+declare type ETHPublicKey = string;
+declare type ETHAddressHex = string;
+declare type ETHAddressBuff = Buffer;
+
+declare module 'ethereumjs-util' {
+    const toBuffer: (data: string) => Buffer;
+    const hashPersonalMessage: (msg: Buffer) => Buffer;
+    const bufferToHex: (buff: Buffer) => string;
+    const ecrecover: (msgHashBuff: Buffer, v: number, r: Buffer, s: Buffer) => ETHPublicKey;
+    const pubToAddress: (pubKey: ETHPublicKey) => ETHAddressBuff;
+}