feat: Add PSS signing and verifying

Sources/CryptorRSA/CryptorRSA.swift

@@ -765,10 +765,11 @@ public class CryptorRSA {
 		/// - Parameters:
 		///		- key:				The `PrivateKey`.
 		///		- algorithm:		The algorithm to use (`Data.Algorithm`).
+		///		- usePSS: 			Bool stating whether or not to use RSA-PSS (Probabilistic signature scheme).
 		///
 		///	- Returns:				A new optional `SignedData` containing the digital signature.
 		///
-		public func signed(with key: PrivateKey, algorithm: Data.Algorithm) throws -> SignedData? {
+		public func signed(with key: PrivateKey, algorithm: Data.Algorithm, usePSS: Bool = false) throws -> SignedData? {
 
 			// Must be plaintext...
 			guard self.type == .plaintextType else {
@@ -793,9 +794,20 @@ public class CryptorRSA {
 
                 let (md, _) = algorithm.algorithmForSignature
 
-                // Provide a pkey_ctx to EVP_DigestSignInit so that the EVP_PKEY_CTX of the signing operation
-                // is written to it, to allow alternative signing options to be set
-                EVP_DigestSignInit(md_ctx, nil, .make(optional: md), nil, .make(optional: key.reference))
+				if usePSS {
+					// If using PSS padding, create a PKEY and set it's padding, mask generation function and salt length.
+					// NID_rsassaPss is `EVP_PKEY_RSA_PSS` as defined in evp.h
+					var pkey_ctx = EVP_PKEY_CTX_new_id(NID_rsassaPss, nil)
+					EVP_DigestSignInit(md_ctx, &pkey_ctx, .make(optional: md), nil, .make(optional: key.reference))
+					EVP_PKEY_CTX_ctrl(pkey_ctx, EVP_PKEY_RSA, -1, EVP_PKEY_CTRL_RSA_PADDING, RSA_PKCS1_PSS_PADDING, nil)
+					EVP_PKEY_CTX_ctrl(pkey_ctx, -1, EVP_PKEY_OP_SIGN, EVP_PKEY_CTRL_RSA_MGF1_MD, 0, .make(optional: md))
+					// Sets salt length to be equal to message digest length
+					EVP_PKEY_CTX_ctrl(pkey_ctx, -1, EVP_PKEY_OP_SIGN, EVP_PKEY_CTRL_RSA_PSS_SALTLEN, -1, .make(optional: md))
+				} else {
+					// Provide a pkey_ctx to EVP_DigestSignInit so that the EVP_PKEY_CTX of the signing operation
+					// is written to it, to allow alternative signing options to be set
+					EVP_DigestSignInit(md_ctx, nil, .make(optional: md), nil, .make(optional: key.reference))
+				}
 
                 // Convert Data to UnsafeRawPointer!
                 _ = self.data.withUnsafeBytes({ (message: UnsafeRawBufferPointer) -> Int32 in
@@ -829,8 +841,19 @@ public class CryptorRSA {
 
 			#else
 
+				let signingAlgorithm: SecKeyAlgorithm
+				if usePSS {
+					if #available(macOS 10.13, iOS 10.0, *) {
+						signingAlgorithm = usePSS ? algorithm.algorithmForPssSignature : algorithm.algorithmForSignature
+					} else {
+						throw Error(code: ERR_NOT_IMPLEMENTED, reason: "RSA-PSS only supported on macOS 10.13/iOS 10.0 and above.")
+					}
+				} else {
+					signingAlgorithm = algorithm.algorithmForSignature
+				}
+
 				var response: Unmanaged<CFError>? = nil
-				let sData = SecKeyCreateSignature(key.reference, algorithm.algorithmForSignature, self.data as CFData, &response)
+				let sData = SecKeyCreateSignature(key.reference, signingAlgorithm, self.data as CFData, &response)
 				if response != nil {
 
 					guard let error = response?.takeRetainedValue() else {
@@ -853,10 +876,11 @@ public class CryptorRSA {
 		///		- key:				The `PublicKey`.
 		///		- signature:		The `SignedData` containing the signature to verify against.
 		///		- algorithm:		The algorithm to use (`Data.Algorithm`).
+		///		- usePSS: 			Bool stating whether or not to use RSA-PSS (Probabilistic signature scheme).
 		///
 		///	- Returns:				True if verification is successful, false otherwise
 		///
-		public func verify(with key: PublicKey, signature: SignedData, algorithm: Data.Algorithm) throws -> Bool {
+		public func verify(with key: PublicKey, signature: SignedData, algorithm: Data.Algorithm, usePSS: Bool = false) throws -> Bool {
 
 			// Must be plaintext...
 			guard self.type == .plaintextType else {
@@ -886,9 +910,17 @@ public class CryptorRSA {
 
                 let (md, _) = algorithm.algorithmForSignature
 
-                // Provide a pkey_ctx to EVP_DigestSignInit so that the EVP_PKEY_CTX of the signing operation
-                // is written to it, to allow alternative signing options to be set
-                EVP_DigestVerifyInit(md_ctx, nil, .make(optional: md), nil, .make(optional: key.reference))
+				if usePSS {
+					// If using PSS padding, create a PKEY and set it's padding and mask generation function.
+					var pkey_ctx = EVP_PKEY_CTX_new_id(NID_rsassaPss, nil)
+					EVP_DigestVerifyInit(md_ctx, &pkey_ctx, .make(optional: md), nil, .make(optional: key.reference))
+					EVP_PKEY_CTX_ctrl(pkey_ctx, EVP_PKEY_RSA, -1, EVP_PKEY_CTRL_RSA_PADDING, RSA_PKCS1_PSS_PADDING, nil)
+					EVP_PKEY_CTX_ctrl(pkey_ctx, -1, EVP_PKEY_OP_VERIFY, EVP_PKEY_CTRL_RSA_MGF1_MD, 0, .make(optional: md))
+				} else {
+					// Provide a pkey_ctx to EVP_DigestSignInit so that the EVP_PKEY_CTX of the signing operation
+					// is written to it, to allow alternative signing options to be set
+					EVP_DigestVerifyInit(md_ctx, nil, .make(optional: md), nil, .make(optional: key.reference))
+				}
 
 
                 var rc = self.data.withUnsafeBytes({ (message: UnsafeRawBufferPointer) -> Int32 in
@@ -915,8 +947,19 @@ public class CryptorRSA {
 
 			#else
 
+				let signingAlgorithm: SecKeyAlgorithm
+				if usePSS {
+					if #available(macOS 10.13, iOS 10.0, *) {
+						signingAlgorithm = usePSS ? algorithm.algorithmForPssSignature : algorithm.algorithmForSignature
+					} else {
+						throw Error(code: ERR_NOT_IMPLEMENTED, reason: "RSA-PSS only supported on macOS 10.13/iOS 10.0 and above.")
+					}
+				} else {
+					signingAlgorithm = algorithm.algorithmForSignature
+				}
+
 				var response: Unmanaged<CFError>? = nil
-				let result = SecKeyVerifySignature(key.reference, algorithm.algorithmForSignature, self.data as CFData, signature.data as CFData, &response)
+				let result = SecKeyVerifySignature(key.reference, signingAlgorithm, self.data as CFData, signature.data as CFData, &response)
 				if response != nil {
 
 					guard let error = response?.takeRetainedValue() else {

Sources/CryptorRSA/CryptorRSADigest.swift

@@ -192,6 +192,31 @@ extension Data {
                     return .rsaSignatureMessagePKCS1v15SHA1
 				}
 			}
+
+			@available(macOS 10.13, iOS 10.0, *)
+			var algorithmForPssSignature: SecKeyAlgorithm {
+				switch self {
+
+				case .sha1:
+					return .rsaSignatureMessagePSSSHA1
+
+				case .sha224:
+					return .rsaSignatureMessagePSSSHA224
+
+				case .sha256:
+					return .rsaSignatureMessagePSSSHA256
+
+				case .sha384:
+					return .rsaSignatureMessagePSSSHA384
+
+				case .sha512:
+					return .rsaSignatureMessagePSSSHA512
+
+				case .gcm:
+					return .rsaSignatureMessagePSSSHA1
+
+				}
+			}
 
 			@available(macOS 10.12, iOS 10.0, *)
 			public var alogrithmForEncryption: SecKeyAlgorithm {

Tests/CryptorRSATests/CryptorRSATests.swift

@@ -584,6 +584,102 @@ cSNAr2BBC8bJ9AfZnRu9+Y1/VyXY91R95bQoMFfgwZdMUEyuL5gG524QplqF
 			print("Test of algorithm: \(name) succeeded")
 		}
 	}
+
+	func test_signVerifyAllDigestTypesPSS() throws {
+
+		// PSS is only supported from swift 4.1 onwards
+		#if !swift(>=4.1) 
+		return
+		#endif
+
+		let algorithms: [(Data.Algorithm, String)] = [(.sha1, ".sha1"),
+													  (.sha224, ".sha224"),
+													  (.sha256, ".sha256"),
+													  (.sha384, ".sha384"),
+													  (.gcm, ".gcm"),
+													/*(.sha512, ".sha512")*/]
+		// Test all the algorithms available...
+		//	Note: .sha512 pss appears to be broken internally on Apple platforms, so we skip it...
+		guard let publicKey = self.publicKey,
+			let privateKey = self.privateKey else {
+				XCTFail("Could not find key")
+				return
+		}
+
+		// Test all the algorithms available...
+		for (algorithm, name) in algorithms {
+
+			print("Testing algorithm: \(name)")
+			let data = CryptorRSATests.randomData(count: 8192)
+			let message = CryptorRSA.createPlaintext(with: data)
+			let signature = try message.signed(with: privateKey, algorithm: algorithm, usePSS: true)
+			XCTAssertNotNil(signature)
+			let verificationResult = try message.verify(with: publicKey, signature: signature!, algorithm: algorithm, usePSS: true)
+			XCTAssertTrue(verificationResult)
+			print("Test of algorithm: \(name) succeeded")
+		}
+	}
+
+	func test_signVerifyBase64PSS() throws {
+
+		// PSS is only supported from swift 4.1 onwards
+		#if !swift(>=4.1) 
+			return
+		#endif
+
+		let algorithms: [(Data.Algorithm, String)] = [(.sha1, ".sha1"),
+													  (.sha224, ".sha224"),
+													  (.sha256, ".sha256"),
+													  (.sha384, ".sha384"),
+													  (.gcm, ".gcm"),
+													/*(.sha512, ".sha512")*/]
+		// Test all the algorithms available...
+		//	Note: .sha512 pss appears to be broken internally on Apple platforms, so we skip it...
+
+		guard let publicKey = self.publicKey,
+			let privateKey = self.privateKey else {
+				XCTFail("Could not find key")
+				return
+		}
+
+		// Test all the algorithms available...
+		for (algorithm, name) in algorithms {
+
+			print("Testing algorithm: \(name)")
+			let data = CryptorRSATests.randomData(count: 8192)
+			let message = CryptorRSA.createPlaintext(with: data)
+			let signature = try message.signed(with: privateKey, algorithm: algorithm, usePSS: true)
+			XCTAssertNotNil(signature)
+			XCTAssertEqual(signature!.base64String, signature!.data.base64EncodedString())
+			let verificationResult = try message.verify(with: publicKey, signature: signature!, algorithm: algorithm, usePSS: true)
+			XCTAssertTrue(verificationResult)
+			print("Test of algorithm: \(name) succeeded")
+		}
+	}
+
+	func test_verifyExtenalPSSSignature() {
+
+		// PSS is only supported from swift 4.1 onwards
+		#if !swift(>=4.1) 
+		return
+		#endif
+
+		guard let publicKey = self.publicKey else {
+			XCTFail("Could not find key")
+			return
+		}
+		// Generated by jwt.io
+		let externalMessage = "eyJhbGciOiJQUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWUsImlhdCI6MTUxNjIzOTAyMn0"
+		let externalSignature = "Itey9AhjNgb1owBaVsTE-7NrZY1c7AJtp990w4AJRZWMOeX-2UiVdil9vflW7BkduRXMA83hCdhQjqzvnJGhxEVllZshPYvueW0otxzI-wl4fPY6ai6qiBh9JzDwFlb9IHyIDGhr3HHKaMjYEwpt8VJYxzEcHwdGg34aczspM0U"
+		let message = CryptorRSA.createPlaintext(with: Data(externalMessage.utf8))
+		let signature = CryptorRSA.createSigned(with: Data(base64urlEncoded: externalSignature)!)
+		do {
+			let verificationResult = try message.verify(with: publicKey, signature: signature, algorithm: .sha256, usePSS: true)
+			XCTAssertTrue(verificationResult)
+		} catch {
+			XCTFail("Error thrown during verification: \(error)")
+		}
+	}
 
     func test_verifyAppIDToken() throws {
 
@@ -772,9 +868,31 @@ cSNAr2BBC8bJ9AfZnRu9+Y1/VyXY91R95bQoMFfgwZdMUEyuL5gG524QplqF
             ("test_randomByteEncryption", test_randomByteEncryption),
 			("test_signVerifyAllDigestTypes", test_signVerifyAllDigestTypes),
 			("test_signVerifyBase64", test_signVerifyBase64),
+			("test_signVerifyAllDigestTypesPSS", test_signVerifyAllDigestTypesPSS),
+			("test_signVerifyBase64PSS", test_signVerifyBase64PSS),
+			("test_verifyExtenalPSSSignature", test_verifyExtenalPSSSignature),
             ("test_verifyAppIDToken", test_verifyAppIDToken),
             ("test_makeKeyPair", test_makeKeyPair),
         ]
     }
 }
 
+private extension Data {	
+
+	func base64urlEncodedString() -> String {
+		let result = self.base64EncodedString()
+		return result.replacingOccurrences(of: "+", with: "-")
+			.replacingOccurrences(of: "/", with: "_")
+			.replacingOccurrences(of: "=", with: "")
+	}
+
+	init?(base64urlEncoded: String) {
+		let paddingLength = 4 - base64urlEncoded.count % 4
+		let padding = (paddingLength < 4) ? String(repeating: "=", count: paddingLength) : ""
+		let base64EncodedString = base64urlEncoded
+			.replacingOccurrences(of: "-", with: "+")
+			.replacingOccurrences(of: "_", with: "/")
+			+ padding
+		self.init(base64Encoded: base64EncodedString)
+	}
+}