Add Api key verifier.

* Add Api key verifier.

Author: geiralund

ktor-utils/src/main/kotlin/no/nav/dagpenger/ktor/auth/ApiKeyVerifier.kt

@@ -0,0 +1,31 @@
+package no.nav.dagpenger.ktor.auth
+
+import javax.crypto.Mac
+import javax.crypto.spec.SecretKeySpec
+
+class ApiKeyVerifier(private val secret: ByteArray) {
+
+    private val algorithm = "HmacSHA256"
+
+    fun verify(apiKey: ByteArray, expectedApiKey: ByteArray): Boolean {
+
+        val hmac = generate(apiKey)
+
+        if (hmac.size != expectedApiKey.size) return false
+        var result = 0
+        for (i in 0 until hmac.size) {
+            result = result.or(hmac[i].toInt().xor(expectedApiKey[i].toInt()))
+        }
+
+        return result == 0
+    }
+
+    fun generate(apiKey: ByteArray): ByteArray {
+        val keySpec = SecretKeySpec(secret, algorithm)
+        val mac = Mac.getInstance(algorithm)
+        mac.init(keySpec)
+
+        val hmac = mac.doFinal(apiKey)
+        return hmac
+    }
+}

ktor-utils/src/test/kotlin/no/nav/dagpenger/ktor/auth/ApiKeyVerifierTest.kt

@@ -0,0 +1,30 @@
+package no.nav.dagpenger.ktor.auth
+
+import org.junit.jupiter.api.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+internal class ApiKeyVerifierTest {
+
+    @Test
+    fun `Should be able to verify api key with same secret`() {
+        val verifier = ApiKeyVerifier("secret".toByteArray())
+        val enc = verifier.generate("apikey".toByteArray())
+        assertTrue { verifier.verify("apikey".toByteArray(), enc) }
+    }
+
+    @Test
+    fun `Should not be able to verify api if key has changed key with same secret`() {
+        val verifier = ApiKeyVerifier("secret".toByteArray())
+        val enc = verifier.generate("apikey".toByteArray())
+        assertFalse { verifier.verify("Apikey".toByteArray(), enc) }
+    }
+
+    @Test
+    fun `Should not be able to verify api if with secret changed`() {
+        val generator = ApiKeyVerifier("another secret".toByteArray())
+        val enc = generator.generate("apikey".toByteArray())
+        val verifier = ApiKeyVerifier("secret".toByteArray())
+        assertFalse { verifier.verify("apikey".toByteArray(), enc) }
+    }
+}