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hailey.at
1import Foundation
2import CryptoKit
3import JOSESwift
4
5class CryptoUtil: NSObject {
6 static func digest(data: Data) -> Data {
7 let hash = SHA256.hash(data: data)
8 return Data(hash)
9 }
10
11 public static func getRandomValues(byteLength: Int) -> Data {
12 let bytes = (0..<byteLength).map { _ in UInt8.random(in: UInt8.min...UInt8.max) }
13 return Data(bytes)
14 }
15
16 static func generateJwk() -> EncodedJWK {
17 let kid = UUID().uuidString
18
19 let privKey = P256.Signing.PrivateKey()
20 let pubKey = privKey.publicKey
21
22 let x = pubKey.x963Representation[1..<33].base64URLEncodedString()
23 let y = pubKey.x963Representation[33...].base64URLEncodedString()
24 let d = privKey.rawRepresentation.base64URLEncodedString()
25
26 let jwk = EncodedJWK()
27 jwk.kty = "EC"
28 jwk.use = "sig"
29 jwk.crv = "P-256"
30 jwk.kid = kid
31 jwk.x = x
32 jwk.y = y
33 jwk.d = d
34 jwk.alg = "ES256"
35
36 return jwk
37 }
38
39 static func decodeJwk(x: String, y: String, d: String) throws -> SecKey {
40 func base64UrlDecode(_ string: String) -> Data? {
41 var base64 = string
42 .replacingOccurrences(of: "-", with: "+")
43 .replacingOccurrences(of: "_", with: "/")
44
45 let remainder = base64.count % 4
46 if remainder > 0 {
47 base64 += String(repeating: "=", count: 4 - remainder)
48 }
49
50 return Data(base64Encoded: base64)
51 }
52
53 guard let xData = base64UrlDecode(x),
54 let yData = base64UrlDecode(y),
55 let dData = base64UrlDecode(d) else {
56 throw ExpoAtprotoAuthError.invalidJwk
57 }
58
59 var keyData = Data()
60 keyData.append(0x04)
61 keyData.append(xData)
62 keyData.append(yData)
63 keyData.append(dData)
64
65 let attributes: [String: Any] = [
66 kSecAttrKeyType as String: kSecAttrKeyTypeEC,
67 kSecAttrKeyClass as String: kSecAttrKeyClassPrivate,
68 kSecAttrKeySizeInBits as String: 256
69 ]
70
71 var error: Unmanaged<CFError>?
72
73 let key = SecKeyCreateWithData(keyData as CFData, attributes as CFDictionary, &error)
74 if error != nil {
75 throw error!.takeUnretainedValue()
76 }
77
78 guard let key = key else {
79 throw ExpoAtprotoAuthError.invalidJwk
80 }
81
82 return key
83 }
84}