Add support for certificates (#31)

* add ident command * add Certificate struct * fix ident command
status-im · Sep 23, 2024 · afb1983 · afb1983
1 parent e75e6b8
commit afb1983
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Showing 10 changed files with 125 additions and 17 deletions.
diff --git a/Keycard.podspec b/Keycard.podspec
@@ -1,6 +1,6 @@
 Pod::Spec.new do |spec|
 	spec.name = 'Keycard'
-	spec.version = '3.0.7'
+	spec.version = '3.1.0'
 	spec.authors = {'Bitgamma' => 'opensource@bitgamma.com'}
 	spec.homepage = 'https://github.com/status-im/Keycard.swift'
 	spec.license = { :type => 'Apache' }

diff --git a/Package.resolved b/Package.resolved
@@ -24,7 +24,7 @@
         "repositoryURL": "https://github.com/status-im/secp256k1.swift.git",
         "state": {
           "branch": "master",
-          "revision": "d2c49786e9245d77f4eba6ce78a87f87506623c5",
+          "revision": "4ab977cc2b2d7319be858bcb30a5d189bb149884",
           "version": null
         }
       },

diff --git a/Package.swift b/Package.swift
@@ -25,7 +25,8 @@ let package = Package(
         // Targets can depend on other targets in this package, and on products in packages which this package depends on.
         .target(
             name: "Keycard",
-            dependencies: ["secp256k1", "CryptoSwift", "ZipArchive", "BigInt"]),
+            dependencies: ["secp256k1", "CryptoSwift", "ZipArchive", "BigInt"],
+            swiftSettings: [.define("USE_SPM")]),
         .testTarget(
             name: "KeycardTests",
             dependencies: ["Keycard"]),

diff --git a/Sources/Keycard/Certificate.swift b/Sources/Keycard/Certificate.swift
@@ -0,0 +1,35 @@
+enum CertificateTag: UInt8 {
+    case certificate = 0x8A
+}
+
+public struct Certificate {
+    let identPub: [UInt8]
+    let caSignature: RecoverableSignature
+
+    public static func fromTLV(certData: [UInt8]) -> Certificate {
+        let pub = Array(certData[0..<33])
+        let r = Array(certData[33..<65])
+        let s = Array(certData[65..<97])
+        let recId = certData[97]
+
+        let hash = Crypto.shared.sha256(pub)
+        let caPub = Crypto.shared.secp256k1RecoverPublic(r: r, s: s, recId: recId, hash: hash, compressed: true)
+        let caSig = RecoverableSignature(r: r, s: s, recId: recId, publicKey: caPub, compressed: true)
+
+        return Certificate(identPub: pub, caSignature: caSig);
+    }
+
+    public static func verifyIdentity(hash: [UInt8], tlvData: [UInt8]) throws -> [UInt8]? {
+        let tlv = TinyBERTLV(tlvData)
+        _ = try tlv.enterConstructed(tag: ECDSASignatureTag.signatureTemplate.rawValue)
+        let certData = try tlv.readPrimitive(tag: CertificateTag.certificate.rawValue)
+        let cert = Certificate.fromTLV(certData: certData)
+        let signature = tlv.peekUnread()
+
+        if (!Crypto.shared.secp256k1Verify(signature: signature, hash: hash, pubKey: cert.identPub)) {
+            return nil
+        }
+
+        return cert.caSignature.publicKey
+    }
+}
diff --git a/Sources/Keycard/Crypto.swift b/Sources/Keycard/Crypto.swift
@@ -195,16 +195,16 @@ class Crypto {
     func secp256k1PublicFromPrivate(_ privKey: [UInt8]) -> [UInt8] {
         var pubKey = secp256k1_pubkey()
         _ = secp256k1_ec_pubkey_create(secp256k1Ctx, &pubKey, privKey)
-        return _secp256k1PubToBytes(&pubKey)
+        return _secp256k1PubToBytes(&pubKey, false)
     }
 
-    func secp256k1RecoverPublic(r: [UInt8], s: [UInt8], recId: UInt8, hash: [UInt8]) -> [UInt8] {
+    func secp256k1RecoverPublic(r: [UInt8], s: [UInt8], recId: UInt8, hash: [UInt8], compressed: Bool) -> [UInt8] {
         var sig = secp256k1_ecdsa_recoverable_signature()
         _ = secp256k1_ecdsa_recoverable_signature_parse_compact(secp256k1Ctx, &sig, r + s, Int32(recId))
 
         var pubKey = secp256k1_pubkey()
         _ = secp256k1_ecdsa_recover(secp256k1Ctx, &pubKey, &sig, hash)
-        return _secp256k1PubToBytes(&pubKey)
+        return _secp256k1PubToBytes(&pubKey, compressed)
     }
 
     func secp256k1Sign(hash: [UInt8], privKey: [UInt8]) -> [UInt8] {
@@ -217,11 +217,33 @@ class Crypto {
         secp256k1_ecdsa_signature_serialize_der(secp256k1Ctx, &derSig, &derOutLen, &sig)
         return Array(derSig[0..<derOutLen])
     }
+
+    func secp256k1Verify(signature: [UInt8], hash: [UInt8], pubKey: [UInt8]) -> Bool {
+        var sig = secp256k1_ecdsa_signature()
+        _ = secp256k1_ecdsa_signature_parse_der(secp256k1Ctx, &sig, signature, signature.count)
+        var signorm = secp256k1_ecdsa_signature()
+        _ = secp256k1_ecdsa_signature_normalize(secp256k1Ctx, &signorm, &sig)
+
+        var pkey = secp256k1_pubkey();
+        _ = secp256k1_ec_pubkey_parse(secp256k1Ctx, &pkey, pubKey, pubKey.count)
+
+        return secp256k1_ecdsa_verify(secp256k1Ctx, &signorm, hash, &pkey) != 0
+    }
 
-    private func _secp256k1PubToBytes(_ pubKey: inout secp256k1_pubkey) -> [UInt8] {
-        var pubKeyBytes = [UInt8](repeating: 0, count: 65)
-        var outputLen = 65
-        _ = secp256k1_ec_pubkey_serialize(secp256k1Ctx, &pubKeyBytes, &outputLen, &pubKey, UInt32(SECP256K1_EC_UNCOMPRESSED))
+    private func _secp256k1PubToBytes(_ pubKey: inout secp256k1_pubkey, _ compressed: Bool) -> [UInt8] {
+        var outputLen: Int
+        var compressedFlag: UInt32
+
+        if (compressed) {
+            outputLen = 33
+            compressedFlag = UInt32(SECP256K1_EC_COMPRESSED)
+        } else {
+            outputLen = 65
+            compressedFlag = UInt32(SECP256K1_EC_UNCOMPRESSED)
+        }
+
+        var pubKeyBytes = [UInt8](repeating: 0, count: outputLen)
+        _ = secp256k1_ec_pubkey_serialize(secp256k1Ctx, &pubKeyBytes, &outputLen, &pubKey, compressedFlag)
 
         return pubKeyBytes
     }

diff --git a/Sources/Keycard/FileLoader.swift b/Sources/Keycard/FileLoader.swift
@@ -1,5 +1,10 @@
 import Foundation
+
+#if USE_SPM
+import ZipArchive
+#else
 import SSZipArchive
+#endif
 
 struct FileLoader {
     private static let blockSize = 247 // 255 - 8 bytes for MAC

diff --git a/Sources/Keycard/Keycard.swift b/Sources/Keycard/Keycard.swift
@@ -29,6 +29,7 @@ public enum KeycardINS: UInt8 {
     case initialize = 0xfe
     case factoryReset = 0xfd
     case getStatus = 0xf2
+    case identifyCard = 0x14
     case verifyPIN = 0x20
     case changePIN = 0x21
     case unblockPIN = 0x22

diff --git a/Sources/Keycard/KeycardCommandSet.swift b/Sources/Keycard/KeycardCommandSet.swift
@@ -61,6 +61,11 @@ public class KeycardCommandSet {
     public func unpairOthers() throws {
         try secureChannel.unpairOthers(channel: cardChannel)
     }
+
+    public func identifyCard(challenge: [UInt8]) throws -> APDUResponse {
+        let cmd = APDUCommand(cla: CLA.proprietary.rawValue, ins: KeycardINS.identifyCard.rawValue, p1: 0x00, p2: 0x00, data: challenge)
+        return try cardChannel.send(cmd)
+    }
 
     public func openSecureChannel(index: UInt8, data: [UInt8]) throws -> APDUResponse {
         try secureChannel.openSecureChannel(channel: cardChannel, index: index, data: data)
@@ -302,5 +307,5 @@ public class KeycardCommandSet {
     public func factoryReset() throws -> APDUResponse {
         let cmd = APDUCommand(cla: CLA.proprietary.rawValue, ins: KeycardINS.factoryReset.rawValue, p1: FactoryResetP1.magic.rawValue, p2: FactoryResetP2.magic.rawValue, data: [])
         return try cardChannel.send(cmd)
-    }    
+    }
 }
diff --git a/Sources/Keycard/RecoverableSignature.swift b/Sources/Keycard/RecoverableSignature.swift
@@ -1,5 +1,6 @@
 enum ECDSASignatureTag: UInt8 {
     case signatureTemplate = 0xA0
+    case rawSignature = 0x80
     case ecdsaTemplate = 0x30
 }
 
@@ -8,29 +9,63 @@ public struct RecoverableSignature {
     public let recId: UInt8
     public let r: [UInt8]
     public let s: [UInt8]
+    public let compressed: Bool
+
+    public init(r: [UInt8], s: [UInt8], recId: UInt8, publicKey: [UInt8], compressed: Bool) {
+        self.r = r
+        self.s = s
+        self.recId = recId
+        self.publicKey = publicKey
+        self.compressed = compressed
+    }
 
     public init(hash: [UInt8], data: [UInt8]) throws {
         let tlv = TinyBERTLV(data)
+        let tag = try tlv.readTag()
+        tlv.unreadLastTag()
+
+        if (tag == ECDSASignatureTag.rawSignature.rawValue) {
+            try self.init(hash: hash, signature: tlv.readPrimitive(tag: tag))
+        } else if (tag == ECDSASignatureTag.signatureTemplate.rawValue) {
+            try self.init(hash: hash, tlv: tlv)
+        } else {
+            throw TLVError.unexpectedTag(expected: ECDSASignatureTag.signatureTemplate.rawValue, actual: tag)
+        }
+    }
+
+    private init(hash: [UInt8], tlv: TinyBERTLV) throws {
         _ = try tlv.enterConstructed(tag: ECDSASignatureTag.signatureTemplate.rawValue)
         self.publicKey = try tlv.readPrimitive(tag: AppInfoTag.pubKey.rawValue)
         _ = try tlv.enterConstructed(tag: ECDSASignatureTag.ecdsaTemplate.rawValue)
         self.r = try Util.shared.dropZeroPrefix(uint8: tlv.readPrimitive(tag: TLVTag.int.rawValue))
         self.s = try Util.shared.dropZeroPrefix(uint8: tlv.readPrimitive(tag: TLVTag.int.rawValue))
-
+        self.compressed = false
+        self.recId = try RecoverableSignature.calculateRecId(hash: hash, pubkey: self.publicKey, r: self.r, s: self.s, compressed: self.compressed)
+    }
+
+    private init(hash: [UInt8], signature: [UInt8]) throws {
+        self.r = Array(signature[0..<32])
+        self.s = Array(signature[32..<64])
+        self.recId = signature[64]
+        self.compressed = false
+        self.publicKey = Crypto.shared.secp256k1RecoverPublic(r: self.r, s: self.s, recId: self.recId, hash: hash, compressed: self.compressed)
+    }
+
+    public static func calculateRecId(hash: [UInt8], pubkey: [UInt8], r: [UInt8], s: [UInt8], compressed: Bool) throws -> UInt8 {
         var foundID: UInt8 = UInt8.max
 
         for i: UInt8 in 0...3 {
-            let pub = Crypto.shared.secp256k1RecoverPublic(r: r, s: s, recId: i, hash: hash)
-            if (pub == self.publicKey) {
+            let pub = Crypto.shared.secp256k1RecoverPublic(r: r, s: s, recId: i, hash: hash, compressed: compressed)
+            if (pub == pubkey) {
                 foundID = i
                 break
             }
         }
 
-        if (foundID != UInt8.max) {
-            self.recId = foundID
-        } else {
+        if (foundID == UInt8.max) {
             throw CardError.unrecoverableSignature
         }
+
+        return foundID
     }
 }
diff --git a/Sources/Keycard/TinyBERTLV.swift b/Sources/Keycard/TinyBERTLV.swift
@@ -113,6 +113,10 @@ class TinyBERTLV {
       throw TLVError.unexpectedLength(length: val.count)
     }
   }
+
+  func peekUnread() -> [UInt8] {
+    return Array(self.buf[self.pos..<self.buf.count])
+  }
 
   func readLength() -> Int {
     var len = Int(buf[pos])