fixes #1

Author: overheadhunter

CryptoLib/Masterkey.swift

@@ -77,6 +77,21 @@ public class Masterkey {
 		}
 		let macKey = try unwrapMasterKey(wrappedKey: wrappedHmacKey.bytes, kek: kek)
 
+		// time-constant version MAC check:
+		guard let storedVersionMac = Data(base64Encoded: jsonData.versionMac), storedVersionMac.count == CC_SHA256_DIGEST_LENGTH else {
+			throw MasterkeyError.malformedMasterkeyFile("invalid base64 data in versionMac")
+		}
+		var calculatedVersionMac = [UInt8](repeating: 0x00, count: Int(CC_SHA256_DIGEST_LENGTH))
+		let versionBytes = withUnsafeBytes(of: UInt32(jsonData.version).bigEndian, Array.init)
+		CCHmac(CCHmacAlgorithm(kCCHmacAlgSHA256), macKey, macKey.count, versionBytes, versionBytes.count, &calculatedVersionMac)
+		var diff : UInt8 = 0x00
+		for i in 0..<calculatedVersionMac.count {
+			diff |= calculatedVersionMac[i] ^ storedVersionMac[i]
+		}
+		if diff != 0x00 {
+			throw MasterkeyError.malformedMasterkeyFile("incorrect version or versionMac")
+		}
+		
 		return createFromRaw(aesMasterKey: aesKey, macMasterKey: macKey)
 	}
 

CryptoLibTests/MasterkeyTests.swift

@@ -68,6 +68,24 @@ class MasterkeyTests: XCTestCase {
 		})
     }
 
+	func testCreateFromMasterkeyFileWithInvalidVersionMac() throws {
+		let jsonData = """
+		{
+			"version": 3,
+			"scryptSalt": "AAAAAAAAAAA=",
+			"scryptCostParam": 2,
+			"scryptBlockSize": 8,
+			"primaryMasterKey": "mM+qoQ+o0qvPTiDAZYt+flaC3WbpNAx1sTXaUzxwpy0M9Ctj6Tih/Q==",
+			"hmacMasterKey": "mM+qoQ+o0qvPTiDAZYt+flaC3WbpNAx1sTXaUzxwpy0M9Ctj6Tih/Q==",
+			"versionMac": "iUmRRHITuyJsJbVNqGNw+82YQ4A3Rma7j/y1v0DCVLa="
+		}
+		""".data(using: .utf8)!
+
+		XCTAssertThrowsError(try Masterkey.createFromMasterkeyFile(jsonData: jsonData, password: "asd"), "invalid password", { error in
+			XCTAssertEqual(error as! MasterkeyError, MasterkeyError.malformedMasterkeyFile("incorrect version or versionMac"))
+		})
+    }
+	
 	func testCreateFromMasterkeyFileWithMalformedJson1() throws {
 		let jsonData = """
 		{
@@ -103,5 +121,23 @@ class MasterkeyTests: XCTestCase {
 			XCTAssertEqual(error as! MasterkeyError, MasterkeyError.malformedMasterkeyFile("invalid base64 data in hmacMasterKey"))
 		})
     }
+	
+	func testCreateFromMasterkeyFileWithMalformedJson3() throws {
+		let jsonData = """
+		{
+			"version": 3,
+			"scryptSalt": "AAAAAAAAAAA=",
+			"scryptCostParam": 2,
+			"scryptBlockSize": 8,
+			"primaryMasterKey": "mM+qoQ+o0qvPTiDAZYt+flaC3WbpNAx1sTXaUzxwpy0M9Ctj6Tih/Q==",
+			"hmacMasterKey": "mM+qoQ+o0qvPTiDAZYt+flaC3WbpNAx1sTXaUzxwpy0M9Ctj6Tih/Q==",
+			"versionMac": "iUmRRHITuyJsJbVN"
+		}
+		""".data(using: .utf8)!
+
+		XCTAssertThrowsError(try Masterkey.createFromMasterkeyFile(jsonData: jsonData, password: "asd"), "invalid password", { error in
+			XCTAssertEqual(error as! MasterkeyError, MasterkeyError.malformedMasterkeyFile("invalid base64 data in versionMac"))
+		})
+    }
 
 }