com.chatwork.scala.jwk.JWKThumbprint.scala Maven / Gradle / Ivy

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scala-jwk

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package com.chatwork.scala.jwk

import java.nio.charset.Charset
import java.security.{ MessageDigest, NoSuchAlgorithmException }

import io.circe.Json
import io.circe.syntax._
import cats.implicits._
import com.chatwork.scala.jwk.JWKError.{ Cause, JWKThumbprintError }
import com.github.j5ik2o.base64scala.{ Base64String, Base64StringFactory }

object JWKThumbprint extends JWKJsonImplicits {

  // See RFC 7638 3.2
  val requiredKeysForEC: Set[String]  = Set("crv", "kty", "x", "y")
  val requiredKeysForRSA: Set[String] = Set("e", "kty", "n")

  def computeFromJWK(jwk: JWK, hashAlg: String = "SHA-256"): Either[JWKThumbprintError, Base64String] =
    jwk.keyType match {
      case KeyType.EC       => computeFromJson(jwk.asJson.mapObject(_.filterKeys(requiredKeysForEC.contains)), hashAlg)
      case KeyType.RSA      => computeFromJson(jwk.asJson.mapObject(_.filterKeys(requiredKeysForRSA.contains)), hashAlg)
      case KeyType.Other(_) => computeFromJson(jwk.asJson, hashAlg)
    }

  private def getDigest(json: Json, hashAlg: String): Either[JWKThumbprintError, Array[Byte]] = {
    try {
      val md = MessageDigest.getInstance(hashAlg)
      md.update(json.noSpacesSortKeys.getBytes(Charset.defaultCharset()))
      Right(md.digest())
    } catch {
      case ex: NoSuchAlgorithmException =>
        Left(
          JWKThumbprintError(
            "Couldn't compute JWK thumbprint: Unsupported hash algorithm: " + ex.getMessage,
            Some(Cause(ex))
          )
        )
    }
  }

  def computeFromJson(
      json: Json,
      hashAlg: String = "SHA-256"
  ): Either[JWKThumbprintError, Base64String] = {
    for {
      v <- getDigest(json, hashAlg)
      r <- Base64StringFactory(urlSafe = true, isNoPadding = true)
        .encode(v)
        .leftMap(error => JWKThumbprintError(error.message))
    } yield r
  }

}