Oh, sorry, it's a simple function to satisfy the base64 length requirements:
import Foundation
import CryptoKit
class JWTValidator {
static func validateSignature() {
let jwtToken = "eyJhbGciOiJFUzM4NCIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWUsImlhdCI6MTUxNjIzOTAyMn0.VUPWQZuClnkFbaEKCsPy7CZVMh5wxbCSpaAWFLpnTe9J0--PzHNeTFNXCrVHysAa3eFbuzD8_bLSsgTKC8SzHxRVSj5eN86vBPo_1fNfE7SHTYhWowjY4E_wuiC13yoj"
let publicKeyBase64 = "MHYwEAYHKoZIzj0CAQYFK4EEACIDYgAEC1uWSXj2czCDwMTLWV5BFmwxdM6PX9p+Pk9Yf9rIf374m5XP1U8q79dBhLSIuaojsvOT39UUcPJROSD1FqYLued0rXiooIii1D3jaW6pmGVJFhodzC31cy5sfOYotrzF"
let parts = jwtToken.components(separatedBy: ".")
let header = parts[0]
let payload = parts[1]
let signature = parts[2]
let dataPublicKey = Data(base64Encoded: publicKeyBase64)!
let dataSigned = (header + "." + payload).data(using: .ascii)!
let dataSignature = Data(base64Encoded: base64StringWithPadding(base64str: signature))!
if #available(iOS 14.0, *) {
let ck = try! P384.Signing.PublicKey(derRepresentation: dataPublicKey)
let x963 = ck.x963Representation
let publicKey = SecKeyCreateWithData(x963 as NSData, [
kSecAttrKeyType as String: kSecAttrKeyTypeECSECPrimeRandom,
kSecAttrKeyClass as String: kSecAttrKeyClassPublic,
] as NSDictionary, nil)!
print(publicKey)
// we have the SecKey representation of the public key.
// validate the JWT with the public key.
var validateError : Unmanaged<CFError>?
let algorithm: SecKeyAlgorithm = .eciesEncryptionStandardX963SHA384AESGCM
let result = SecKeyVerifySignature(publicKey,
algorithm,
dataSigned as NSData,
dataSignature as NSData,
&validateError)
if let validateError = validateError {
print(validateError)
}
print("JWT is valid: \(result)") // prints JWT is valid: false
}
}
static func base64StringWithPadding(base64str: String) -> String {
var newStr = base64str.replacingOccurrences(of: "-", with: "+")
.replacingOccurrences(of: "_", with: "/")
let count = newStr.count % 4
if count > 0 {
let amount = 4 - count
for _ in 0..<amount {
newStr += "="
}
}
return newStr
}
}
