ECRecovery library added with test and docs

contracts/ECRecovery.sol

+pragma solidity ^0.4.11;
+
+
+/**
+ * Eliptic curve signature operations
+ * Based on https://gist.github.com/axic/5b33912c6f61ae6fd96d6c4a47afde6d
+ */
+library ECRecovery {
+
+	// Duplicate Solidity's ecrecover, but catching the CALL return value
+	function safeRecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) internal returns (bool, address) {
+		// We do our own memory management here. Solidity uses memory offset
+		// 0x40 to store the current end of memory. We write past it (as
+		// writes are memory extensions), but don't update the offset so
+		// Solidity will reuse it. The memory used here is only needed for
+		// this context.
+
+		bool ret;
+		address addr;
+
+		assembly {
+			let size := mload(0x40)
+			mstore(size, hash)
+			mstore(add(size, 32), v)
+			mstore(add(size, 64), r)
+			mstore(add(size, 96), s)
+
+			// NOTE: we can reuse the request memory because we deal with
+			//       the return code
+			ret := call(3000, 1, 0, size, 128, size, 32)
+			addr := mload(size)
+		}
+
+		return (ret, addr);
+	}
+
+	function recover(bytes32 hash, bytes sig) internal returns (address) {
+		bytes32 r;
+		bytes32 s;
+		uint8 v;
+
+		if (sig.length != 65)
+			return (address(0));
+
+		assembly {
+			r := mload(add(sig, 32))
+			s := mload(add(sig, 64))
+			v := byte(0, mload(add(sig, 96)))
+		}
+
+		// albeit non-transactional signatures are not specified by the YP, one would expect it
+		// to match the YP range of [27, 28]
+		//
+		// geth uses [0, 1] and some clients have followed. This might change, see:
+		//  https://github.com/ethereum/go-ethereum/issues/2053
+		if (v < 27)
+			v += 27;
+
+		if (v != 27 && v != 28)
+			return (address(0));
+
+		bool ret;
+		address addr;
+		(ret, addr) = safeRecover(hash, v, r, s);
+		return addr;
+	}
+
+}

docs/source/ecrecovery.rst

+ECReovery
+=============================================
+
+Recover the signer address of messages using elliptic curve signatures.
+
+safeRecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) internal returns (bool, address)
+"""""""""""""""""""""""""""""""""""""""""""""""""
+
+Returns the signer of the the hash using the signature divided in v, r, and s values.
+
+recover(bytes32 hash, bytes sig) internal returns (address)
+"""""""""""""""""""""""""""""""""""""""""""""""""
+
+Returns the signer of the the hash using the signature that provides the web3.sign() method.

test/ECRecovery.js

+var ECRecoveryMock = artifacts.require("./helpers/ECRecoveryMock.sol");
+
+contract('ECRecovery', function(accounts) {
+
+  let ecrecovery;
+
+  before(async function() {
+    ecrecovery = await ECRecoveryMock.new();
+  });
+
+  it("recover v0", async function() {
+    let signer = '0x2cc1166f6212628a0deef2b33befb2187d35b86c';
+    let message = '0x7dbaf558b0a1a5dc7a67202117ab143c1d8605a983e4a743bc06fcc03162dc0d'; // web3.sha3('OpenZeppelin')
+    let signature = '0x5d99b6f7f6d1f73d1a26497f2b1c89b24c0993913f86e9a2d02cd69887d9c94f3c880358579d811b21dd1b7fd9bb01c1d81d10e69f0384e675c32b39643be89200';
+    await ecrecovery.recover(message, signature);
+    assert.equal(signer, await ecrecovery.signer());
+  });
+
+  it("recover v1", async function() {
+    let signer = '0x1e318623ab09fe6de3c9b8672098464aeda9100e';
+    let message = '0x7dbaf558b0a1a5dc7a67202117ab143c1d8605a983e4a743bc06fcc03162dc0d'; // web3.sha3('OpenZeppelin')
+    let signature = '0x331fe75a821c982f9127538858900d87d3ec1f9f737338ad67cad133fa48feff48e6fa0c18abc62e42820f05943e47af3e9fbe306ce74d64094bdf1691ee53e001';
+    await ecrecovery.recover(message, signature);
+    assert.equal(signer, await ecrecovery.signer());
+  });
+
+  it("safeRecover v0", async function() {
+    let signer = '0x58d5f9f841bcf9e502b438cc81d1ea3ba3f8f7f3';
+    let message = '0x7dbaf558b0a1a5dc7a67202117ab143c1d8605a983e4a743bc06fcc03162dc0d'; // web3.sha3('OpenZeppelin')
+    let signature = '3690f285f30200dfacd35b9ee9af4beaf2c2f4b7880d93dd9bdf776e8fdbec6a095d00c80e20e95a68c8effc038707dd740aabf94a6ca37c09733874f772d6e000';
+    let v = (signature.substring(128,130) == '01') ? 28 : 27;
+    let r = '0x'+signature.substring(0,64);
+    let s = '0x'+signature.substring(64,128);
+    await ecrecovery.safeRecover(message, v, r, s);
+    assert.equal(signer, await ecrecovery.signer());
+    assert.equal(true, await ecrecovery.result());
+  });
+
+  it("safeRecover v1", async function() {
+    let signer = '0x0b8124c2429c44e8ca31e7db6f85845abf146415';
+    let message = '0x7dbaf558b0a1a5dc7a67202117ab143c1d8605a983e4a743bc06fcc03162dc0d'; // web3.sha3('OpenZeppelin')
+    let signature = '7696f87b3f14e2f1c408c552c0005479bfe35df3a9efb493a2ad2bdf25d95c8c605b6f83699faca9bcbc3c665b434ed8d9c717aa71a1916f054fc41671dd38ad01';
+    let v = (signature.substring(128,130) == '01') ? 28 : 27;
+    let r = '0x'+signature.substring(0,64);
+    let s = '0x'+signature.substring(64,128);
+    await ecrecovery.safeRecover(message, v, r, s);
+    assert.equal(signer, await ecrecovery.signer());
+    assert.equal(true, await ecrecovery.result());
+  });
+
+});

test/helpers/ECRecoveryMock.sol

+pragma solidity ^0.4.11;
+
+
+import '../../contracts/ECRecovery.sol';
+
+
+contract ECRecoveryMock {
+
+  bool public result;
+  address public signer;
+
+  function safeRecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) {
+    (result, signer) = ECRecovery.safeRecover(hash, v, r, s);
+  }
+
+  function recover(bytes32 hash, bytes sig) {
+    signer = ECRecovery.recover(hash, sig);
+  }
+
+}