import java.io._
import java.security._
import java.nio.file._
import scala.collection.JavaConverters._

Security.addProvider(new ru.CryptoPro.JCP.JCP)

val path = Paths.get("/home/dmitry/work/tmp/test.store")

def mkInputStream(path: Path) = Files.newInputStream(path)

def overrideAvailable(is: InputStream) =
  new FilterInputStream(is) {
    override def available = 0
  }

def dumpAliases(is: InputStream) = {
  val ks = KeyStore.getInstance("CertStore", "JCP")
  ks.load(is, null)
  println(ks.aliases.asScala.toList)
}

// Вывод (правильный): List(test-cert)
dumpAliases(mkInputStream(path))
// Вывод (неправильный): List()
dumpAliases(overrideAvailable(mkInputStream(path)))