Merge pull request #159 from Clee681/recover-pub-key

add KeyUtil.recoverPublicKey
argentlabs · Nov 29, 2021 · d9494a9 · d9494a9
2 parents 8205d3f + d4130d5
commit d9494a9
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diff --git a/web3sTests/Utils/KeyUtilTests.swift b/web3sTests/Utils/KeyUtilTests.swift
@@ -51,4 +51,12 @@ class KeyUtilTests: XCTestCase {
         XCTAssertEqual(address.value, "0x751e735a83a8142c1b9dc722ef559b898f1d77fa")
     }
 
+    func testRecoverPublicKey() {
+        let account = try! EthereumAccount(keyStorage: TestEthereumKeyStorage(privateKey: "0x2639f727ded571d584643895d43d02a7a190f8249748a2c32200cfc12dde7173"))
+        let signature = try! account.sign(message: "Hello message!")
+
+        let address = try! KeyUtil.recoverPublicKey(message: "Hello message!".web3.keccak256, signature: signature)
+
+        XCTAssertEqual(address, account.address.value.lowercased())
+    }
 }
diff --git a/web3swift/src/Utils/KeyUtil.swift b/web3swift/src/Utils/KeyUtil.swift
@@ -14,10 +14,11 @@ enum KeyUtilError: Error {
     case privateKeyInvalid
     case unknownError
     case signatureFailure
+    case signatureParseFailure
+    case badArguments
 }
 
 class KeyUtil {
-
     static func generatePrivateKeyData() -> Data? {
         return Data.randomOfLength(32)
     }
@@ -105,4 +106,52 @@ class KeyUtil {
 
         return signature
     }
+
+    static func recoverPublicKey(message: Data, signature: Data) throws -> String {
+        if signature.count != 65 || message.count != 32 {
+            throw KeyUtilError.badArguments
+        }
+
+        guard let ctx = secp256k1_context_create(UInt32(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY)) else {
+            print("Failed to sign message: invalid context.")
+            throw KeyUtilError.invalidContext
+        }
+        defer { secp256k1_context_destroy(ctx) }
+
+        // get recoverable signature
+        let signaturePtr = UnsafeMutablePointer<secp256k1_ecdsa_recoverable_signature>.allocate(capacity: 1)
+        defer { signaturePtr.deallocate() }
+
+        let serializedSignature = Data(signature[0..<64])
+        var v = Int32(signature[64])
+        if v >= 27 && v <= 30 {
+            v -= 27
+        } else if v >= 31 && v <= 34 {
+            v -= 31
+        } else if v >= 35 && v <= 38 {
+            v -= 35
+        }
+
+        try serializedSignature.withUnsafeBytes {
+            guard secp256k1_ecdsa_recoverable_signature_parse_compact(ctx, signaturePtr, $0.bindMemory(to: UInt8.self).baseAddress!, v) == 1 else {
+                print("Failed to parse signature: recoverable ECDSA signature parse failed.")
+                throw KeyUtilError.signatureParseFailure
+            }
+        }
+        let pubkey = UnsafeMutablePointer<secp256k1_pubkey>.allocate(capacity: 1)
+        defer { pubkey.deallocate() }
+
+        try message.withUnsafeBytes {
+            guard secp256k1_ecdsa_recover(ctx, pubkey, signaturePtr, $0.bindMemory(to: UInt8.self).baseAddress!) == 1 else {
+                throw KeyUtilError.signatureFailure
+            }
+        }
+        var size: Int = 65
+        var rv = Data(count: size)
+        rv.withUnsafeMutableBytes {
+            secp256k1_ec_pubkey_serialize(ctx, $0.bindMemory(to: UInt8.self).baseAddress!, &size, pubkey, UInt32(SECP256K1_EC_UNCOMPRESSED))
+            return
+        }
+        return "0x\(rv[1...].web3.keccak256.web3.hexString.suffix(40))"
+    }
 }