From 447ebfd255c8092978ab5c0ed82f3f9232c9b27b Mon Sep 17 00:00:00 2001
From: Pat Garrity <pfm@garrity.co>
Date: Fri, 30 Jan 2026 17:02:57 -0600
Subject: [PATCH] argon2

---
 .../main/scala/gs/smolban/auth/Argon2.scala   | 158 ++++++++++++++++++
 .../scala/gs/smolban/auth/Argon2Hash.scala    | 145 ++++++++++++++++
 .../scala/gs/smolban/auth/Argon2Secret.scala  | 107 ++++++++++++
 .../gs/smolban/auth/RandomByteProvider.scala  |  57 +++++++
 4 files changed, 467 insertions(+)
 create mode 100644 modules/auth/src/main/scala/gs/smolban/auth/Argon2.scala
 create mode 100644 modules/auth/src/main/scala/gs/smolban/auth/Argon2Hash.scala
 create mode 100644 modules/auth/src/main/scala/gs/smolban/auth/Argon2Secret.scala
 create mode 100644 modules/auth/src/main/scala/gs/smolban/auth/RandomByteProvider.scala

diff --git a/modules/auth/src/main/scala/gs/smolban/auth/Argon2.scala b/modules/auth/src/main/scala/gs/smolban/auth/Argon2.scala
new file mode 100644
index 0000000..e91205e
--- /dev/null
+++ b/modules/auth/src/main/scala/gs/smolban/auth/Argon2.scala
@@ -0,0 +1,158 @@
+package gs.smolban.auth
+
+import cats.effect.Sync
+import cats.syntax.all.*
+import java.nio.charset.StandardCharsets
+import org.bouncycastle.crypto.generators.Argon2BytesGenerator
+import org.bouncycastle.crypto.params.Argon2Parameters
+
+/** Argon2 hashing support based on the Bouncy Castle library.
+  *
+  * @param config
+  *   Algorithm and configuration parameters.
+  * @param secret
+  *   The secret used to generate hashes.
+  * @param randomByteProvider
+  *   Used to generate random bytes.
+  */
+final class Argon2[F[_]: Sync](
+  val config: Argon2.Config,
+  val secret: Argon2Secret,
+  val randomByteProvider: RandomByteProvider[F]
+):
+
+  /** Calculate a new hash for some input.
+    *
+    * @param input
+    *   The input string to hash.
+    * @return
+    *   The calculated hash.
+    */
+  def calculateHash(input: String): F[Argon2Hash] =
+    randomSalt().map { salt =>
+      val ap    = buildAlgorithmParams(salt)
+      val a2    = new Argon2BytesGenerator()
+      val _     = a2.init(ap)
+      val bytes = new Array[Byte](config.hashLengthInBytes)
+      val _ = a2.generateBytes(input.getBytes(StandardCharsets.UTF_8), bytes)
+      new Argon2Hash(
+        algorithmVersion = config.algorithmVersion,
+        algorithmType = config.algorithmType,
+        iterations = config.iterations,
+        parallelism = config.parallelism,
+        memoryInKb = config.memoryInKb,
+        salt = salt,
+        hash = bytes
+      )
+    }
+
+  /** Given some input, determine if that input matches a stored hash.
+    *
+    * @param input
+    *   The input to compare.
+    * @param stored
+    *   The stored hash.
+    * @return
+    *   True if the input matches the hash, false otherwise.
+    */
+  def doesInputMatch(
+    input: String,
+    stored: Argon2Hash
+  ): F[Boolean] =
+    Sync[F].delay {
+      // Use the stored hash as the parameter source.
+      val ap = buildAlgorithmParams(stored)
+
+      // Hash the input using the stored parameters.
+      val a2    = new Argon2BytesGenerator()
+      val _     = a2.init(ap)
+      val bytes = new Array[Byte](stored.hash.length)
+      val _ = a2.generateBytes(input.getBytes(StandardCharsets.UTF_8), bytes)
+
+      // Compare the bytes to determine if the input matches the stored hash.
+      bytes.sameElements(stored.hash)
+    }
+
+  private def randomSalt(): F[Array[Byte]] =
+    randomByteProvider.generateBytes(config.saltLengthInBytes)
+
+  private def buildAlgorithmParams(salt: Array[Byte]): Argon2Parameters =
+    new Argon2Parameters.Builder(config.algorithmType)
+      .withIterations(config.iterations)
+      .withMemoryAsKB(config.memoryInKb)
+      .withParallelism(config.parallelism)
+      .withSalt(salt)
+      .withSecret(secret.bytes)
+      .withVersion(config.algorithmVersion)
+      .build()
+
+  private def buildAlgorithmParams(hash: Argon2Hash): Argon2Parameters =
+    new Argon2Parameters.Builder(hash.algorithmType)
+      .withVersion(hash.algorithmVersion)
+      .withIterations(hash.iterations)
+      .withParallelism(hash.parallelism)
+      .withMemoryAsKB(hash.memoryInKb)
+      .withSalt(hash.salt)
+      .withSecret(secret.bytes)
+      .build()
+
+object Argon2:
+  val Algorithm: Int = Argon2Parameters.ARGON2_id
+
+  /** Includes all parameters needed to support Argon2 for Smolban. Includes all
+    * standard algorithm parameters, along with additional information such as
+    * the number of bytes that Smolban uses to produce hashes.
+    *
+    * @param algorithmVersion
+    *   The algorithm version used to hash bytes.
+    * @param algorithmType
+    *   The Argon2 variant used to hash bytes.
+    * @param iterations
+    *   Number of algorithm iterations.
+    * @param parallelism
+    *   Amount of algorithm parallelism.
+    * @param memoryInKb
+    *   Memory, in KB, used by the algorithm.
+    * @param saltLengthInBytes
+    *   Number of bytes Smolban uses for salts.
+    * @param hashLengthInBytes
+    *   Number of bytes Smolban uses for output hashes.
+    */
+  case class Config(
+    algorithmVersion: Int,
+    algorithmType: Int,
+    iterations: Int,
+    parallelism: Int,
+    memoryInKb: Int,
+    saltLengthInBytes: Int,
+    hashLengthInBytes: Int
+  )
+
+  /** @return
+    *   [[Argon2.Params]] with default settings. Suitable for most cases.
+    */
+  def defaultConfig(): Config =
+    Config(
+      algorithmVersion = Defaults.AlgorithmVersion,
+      algorithmType = Defaults.AlgorithmType,
+      iterations = Defaults.Iterations,
+      parallelism = Defaults.Parallelism,
+      memoryInKb = Defaults.MemoryInKB,
+      saltLengthInBytes = Defaults.SaltLengthInBytes,
+      hashLengthInBytes = Defaults.HashLengthInBytes
+    )
+
+  object Defaults:
+
+    val AlgorithmVersion: Int  = Argon2Parameters.ARGON2_VERSION_13
+    val AlgorithmType: Int     = Argon2Parameters.ARGON2_id
+    val Iterations: Int        = 3
+    val Parallelism: Int       = 2
+    val SaltLengthInBytes: Int = 16
+    val MemoryInKB: Int        = 1024
+    val HashLengthInBytes: Int = 32
+    val KeyLengthInBytes: Int  = 32
+
+  end Defaults
+
+end Argon2
diff --git a/modules/auth/src/main/scala/gs/smolban/auth/Argon2Hash.scala b/modules/auth/src/main/scala/gs/smolban/auth/Argon2Hash.scala
new file mode 100644
index 0000000..787be73
--- /dev/null
+++ b/modules/auth/src/main/scala/gs/smolban/auth/Argon2Hash.scala
@@ -0,0 +1,145 @@
+package gs.smolban.auth
+
+import java.util.Base64
+import scala.util.Try
+
+/** Represents an Argon2 hash packed with the parameters that produced it.
+  *
+  * @param algorithmVersion
+  *   The Argon2 algorithm version.
+  * @param algorithmType
+  *   The Argon2 type.
+  * @param iterations
+  *   The Argon2 number of iterations.
+  * @param parallelism
+  *   The Argon2 parallelism factor.
+  * @param memoryInKb
+  *   The Argon2 memory, expressed in KB.
+  * @param salt
+  *   The unencoded salt.
+  * @param hash
+  *   The unencoded hash.
+  */
+final class Argon2Hash(
+  val algorithmVersion: Int,
+  val algorithmType: Int,
+  val iterations: Int,
+  val parallelism: Int,
+  val memoryInKb: Int,
+  val salt: Array[Byte],
+  val hash: Array[Byte]
+):
+
+  /** Encode this hash as a '$' delimited string that includes all parameters.
+    * This string can be parsed by using the `decode` function.
+    *
+    * @return
+    *   The encoded hash string.
+    */
+  def encode(): String =
+    s"v=$algorithmVersion$$t=$algorithmType$$i=$iterations$$p=$parallelism$$m=$memoryInKb}$$${encodedSalt()}$$${encodedHash()}"
+
+  private def encodedSalt(): String =
+    Base64.getEncoder().encodeToString(salt)
+
+  private def encodedHash(): String =
+    Base64.getEncoder().encodeToString(hash)
+
+object Argon2Hash:
+
+  /** Decode a string produced by the [[Argon2Hash]] encode function.
+    *
+    * @param input
+    *   The encoded string.
+    * @return
+    *   The parsed hash, or `None` if the input is not a valid hash.
+    */
+  def decode(input: String): Option[Argon2Hash] =
+    val parts = input.split("\\$")
+    if parts.length != 7 then None
+    else
+      for
+        v <- parseInt(parts(0))
+        t <- parseInt(parts(1))
+        i <- parseInt(parts(2))
+        p <- parseInt(parts(3))
+        m <- parseInt(parts(4))
+        s <- parseBytes(parts(5))
+        h <- parseBytes(parts(6))
+        out <- new Builder()
+          .withAlgorithmVersion(v)
+          .withAlgorithmType(t)
+          .withIterations(i)
+          .withParallelism(p)
+          .withMemoryInKb(m)
+          .withSalt(s)
+          .withHash(h)
+          .build()
+      yield out
+
+  private def parseInt(input: String): Option[Int] =
+    val parts = input.split("\\=")
+    if parts.length != 2 then None
+    else parts(1).toIntOption
+
+  private def parseBytes(input: String): Option[Array[Byte]] =
+    Try(Base64.getDecoder().decode(input)).toOption
+
+  private class Builder(
+    var algorithmVersion: Option[Int] = None,
+    var algorithmType: Option[Int] = None,
+    var iterations: Option[Int] = None,
+    var parallelism: Option[Int] = None,
+    var memoryInKb: Option[Int] = None,
+    var salt: Option[Array[Byte]] = None,
+    var hash: Option[Array[Byte]] = None
+  ):
+
+    def withAlgorithmVersion(input: Int): Builder =
+      algorithmVersion = Some(input)
+      this
+
+    def withAlgorithmType(input: Int): Builder =
+      algorithmType = Some(input)
+      this
+
+    def withIterations(input: Int): Builder =
+      iterations = Some(input)
+      this
+
+    def withParallelism(input: Int): Builder =
+      parallelism = Some(input)
+      this
+
+    def withMemoryInKb(input: Int): Builder =
+      memoryInKb = Some(input)
+      this
+
+    def withSalt(input: Array[Byte]): Builder =
+      salt = Some(input)
+      this
+
+    def withHash(input: Array[Byte]): Builder =
+      hash = Some(input)
+      this
+
+    def build(): Option[Argon2Hash] =
+      for
+        v <- algorithmVersion
+        t <- algorithmType
+        i <- iterations
+        p <- parallelism
+        m <- memoryInKb
+        s <- salt
+        h <- hash
+      yield new Argon2Hash(
+        algorithmVersion = v,
+        algorithmType = t,
+        iterations = i,
+        parallelism = p,
+        memoryInKb = m,
+        salt = s,
+        hash = h
+      )
+
+end Argon2Hash
diff --git a/modules/auth/src/main/scala/gs/smolban/auth/Argon2Secret.scala b/modules/auth/src/main/scala/gs/smolban/auth/Argon2Secret.scala
new file mode 100644
index 0000000..57105a5
--- /dev/null
+++ b/modules/auth/src/main/scala/gs/smolban/auth/Argon2Secret.scala
@@ -0,0 +1,107 @@
+package gs.smolban.auth
+
+import cats.Applicative
+import cats.effect.Sync
+import cats.syntax.all.*
+import java.nio.charset.StandardCharsets
+import java.nio.file.Files
+import java.nio.file.Path
+import java.nio.file.StandardOpenOption
+import java.util.Base64
+
+/** Secret intended for use with [[Argon2]]. Random array of bytes.
+  *
+  * @param bytes
+  *   The underlying bytes that represent the secret.
+  */
+final class Argon2Secret(val bytes: Array[Byte]):
+
+  override def equals(obj: Any): Boolean =
+    obj match
+      case other: Argon2Secret => bytes.sameElements(other.bytes)
+      case _                   => false
+
+  override def hashCode(): Int = bytes.hashCode()
+
+  /** @return
+    *   The value of this secret, encoded using Base64.
+    */
+  def encodeBase64(): String = Base64.getEncoder().encodeToString(bytes)
+
+  /** Write this secret to a local file.
+    *
+    * @param path
+    *   The path to write. Any existing file will be truncated.
+    * @return
+    *   An effect which writes the secret.
+    */
+  def writeToLocalFile[F[_]: Sync](path: Path): F[Unit] =
+    Argon2Secret.writeToLocalFile[F](path, this)
+
+object Argon2Secret:
+
+  /** Decode the given Base64 string as an [[Argon2Secret]].
+    *
+    * @param input
+    *   The string that houses encoded bytes.
+    * @return
+    *   The new [[Argon2Secret]] instance, backed by the input bytes.
+    */
+  def decode(input: String): Argon2Secret =
+    new Argon2Secret(Base64.getDecoder().decode(input))
+
+  /** Load a secret from a local file. The following assumptions are made:
+    *
+    *   - The file contains nothing but the base64-encoded bytes.
+    *   - The file has no newlines.
+    *
+    * @param path
+    *   The path to the local file.
+    * @return
+    *   The loaded secret.
+    */
+  def loadFromLocalFile[F[_]: Sync](path: Path): F[Argon2Secret] =
+    Sync[F]
+      .delay(
+        Files.readString(path, StandardCharsets.UTF_8)
+      )
+      .map(decode)
+
+  /** Write a secret to a local file. The resultant file will contain the
+    * base64-encoded bytes of the given secret.
+    *
+    * @param path
+    *   The path for the local file. This file will be truncated if it exists.
+    * @param secret
+    *   The secret to write.
+    * @return
+    *   An effect which writes the secret.
+    */
+  def writeToLocalFile[F[_]: Sync](
+    path: Path,
+    secret: Argon2Secret
+  ): F[Unit] =
+    Sync[F].delay(
+      Files.writeString(
+        path,
+        secret.encodeBase64(),
+        StandardOpenOption.TRUNCATE_EXISTING
+      )
+    )
+
+  /** Generate a new random secret.
+    *
+    * @param size
+    *   The number of bytes in the secret value.
+    * @param randomByteProvider
+    *   The [[RandomByteProvider]].
+    * @return
+    *   The new [[Argon2Secret]].
+    */
+  def generate[F[_]: Applicative](
+    size: Int,
+    randomByteProvider: RandomByteProvider[F]
+  ): F[Argon2Secret] =
+    randomByteProvider.generateBytes(size).map(new Argon2Secret(_))
+
+end Argon2Secret
diff --git a/modules/auth/src/main/scala/gs/smolban/auth/RandomByteProvider.scala b/modules/auth/src/main/scala/gs/smolban/auth/RandomByteProvider.scala
new file mode 100644
index 0000000..f75cb98
--- /dev/null
+++ b/modules/auth/src/main/scala/gs/smolban/auth/RandomByteProvider.scala
@@ -0,0 +1,57 @@
+package gs.smolban.auth
+
+import cats.effect.Sync
+import java.security.SecureRandom
+
+/** Utility which produces random bytes. Used for cryptographic support.
+  */
+trait RandomByteProvider[F[_]]:
+  /** Generate the specified number of random bytes.
+    *
+    * @param numberOfBytes
+    *   The number of bytes to generate.
+    * @return
+    *   New array with the specified number of random bytes.
+    */
+  def generateBytes(numberOfBytes: Int): F[Array[Byte]]
+
+object RandomByteProvider:
+
+  /** Default random number generator.
+    */
+  lazy val RNG: SecureRandom = new SecureRandom
+
+  /** New [[RandomByteProvider]] that uses the default (secure) random number
+    * generator to produce bytes.
+    *
+    * @return
+    *   The new provider instance.
+    */
+  def secureRandom[F[_]: Sync]: RandomByteProvider[F] =
+    new SecureRandomProvider[F](RNG)
+
+  /** New [[RandomByteProvider]] that uses the given `SecureRandom` instance to
+    * produce bytes.
+    *
+    * @param random
+    *   The `SecureRandom` instance.
+    * @return
+    *   The new provider.
+    */
+  def secureRandom[F[_]: Sync](random: SecureRandom): RandomByteProvider[F] =
+    new SecureRandomProvider[F](random)
+
+  final class SecureRandomProvider[F[_]: Sync](
+    val random: SecureRandom
+  ) extends RandomByteProvider[F]:
+
+    /** @inheritDocs
+      */
+    override def generateBytes(numberOfBytes: Int): F[Array[Byte]] =
+      Sync[F].delay {
+        val b = new Array[Byte](numberOfBytes)
+        random.nextBytes(b)
+        b
+      }
+
+end RandomByteProvider