From c047b04d95ddee3874582310864205f635d07079 Mon Sep 17 00:00:00 2001
From: Infendro <infendro@noreply.infendro.com>
Date: Sun, 20 Jul 2025 10:43:05 +0200
Subject: [PATCH] implement PBKDF2

---
 gradle/libs.versions.toml                     |  2 +-
 .../kotlin/com/infendro/kdf/PBKDF2.kt         | 45 +++++++++++++++++++
 .../kotlin/com/infendro/kdf/util/ByteArray.kt | 26 +++++++++++
 3 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 src/commonMain/kotlin/com/infendro/kdf/PBKDF2.kt
 create mode 100644 src/commonMain/kotlin/com/infendro/kdf/util/ByteArray.kt

diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index ed7967b..aa2fdd9 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -1,7 +1,7 @@
 [versions]
 kotlin = "2.1.20"
 mac = "1.1.0"
-hash = "1.1.0"
+hash = "1.2.0"
 
 [plugins]
 multiplatform = { id = "org.jetbrains.kotlin.multiplatform", version.ref = "kotlin" }
diff --git a/src/commonMain/kotlin/com/infendro/kdf/PBKDF2.kt b/src/commonMain/kotlin/com/infendro/kdf/PBKDF2.kt
new file mode 100644
index 0000000..95f4625
--- /dev/null
+++ b/src/commonMain/kotlin/com/infendro/kdf/PBKDF2.kt
@@ -0,0 +1,45 @@
+package com.infendro.kdf
+
+import com.infendro.hash.HashFunction
+import com.infendro.kdf.util.addAll
+import com.infendro.kdf.util.toByteArray
+import com.infendro.kdf.util.xor
+import com.infendro.mac.HMAC
+
+class PBKDF2(
+    function: HashFunction,
+) {
+    private val size = function.bytes
+    private val hmac = HMAC(function)
+
+    fun hash(
+        value: ByteArray,
+        salt: ByteArray,
+        iterations: Int,
+        length: Int,
+    ): ByteArray {
+        val key = mutableListOf<Byte>()
+
+        for (i in 1..(length + size - 1) / size) {
+            val input = salt + i.toUInt().toByteArray()
+
+            var u = hmac.hash(value, input)
+            var result = u
+            repeat(iterations - 1) {
+                u = hmac.hash(value, u)
+                result = result xor u
+            }
+
+            key.addAll(result)
+
+            if (key.size >= length) {
+                println(key.size)
+                break
+            }
+        }
+
+        return key
+            .take(length)
+            .toByteArray()
+    }
+}
diff --git a/src/commonMain/kotlin/com/infendro/kdf/util/ByteArray.kt b/src/commonMain/kotlin/com/infendro/kdf/util/ByteArray.kt
new file mode 100644
index 0000000..09aaaeb
--- /dev/null
+++ b/src/commonMain/kotlin/com/infendro/kdf/util/ByteArray.kt
@@ -0,0 +1,26 @@
+package com.infendro.kdf.util
+
+import kotlin.experimental.xor
+
+internal infix fun ByteArray.xor(
+    that: ByteArray,
+): ByteArray {
+    if (this.size != that.size) throw Exception()
+
+    return ByteArray(size) { i ->
+        this[i] xor that[i]
+    }
+}
+
+internal fun MutableCollection<Byte>.addAll(
+    bytes: ByteArray,
+): Boolean {
+    return addAll(bytes.toList())
+}
+
+internal fun UInt.toByteArray(): ByteArray {
+    return ByteArray(4) { i ->
+        val offset = (3 - i) * 8
+        (this shr offset).toByte()
+    }
+}