Implement JCA-based SHA1-RSA signature verification logic

To be used for Travis's new authentication mechanism
Refs #43

build.sbt

@@ -19,6 +19,9 @@ libraryDependencies += "com.google.code.gson" % "gson" % "2.8.0"
 
 libraryDependencies += "ch.qos.logback" % "logback-classic" % "1.1.9"
 
+// For reading PEM ("-----BEGIN PUBLIC KEY-----"), which Travis's API uses for its public key.
+libraryDependencies += "org.bouncycastle" % "bcpkix-jdk15on" % "1.56"
+
 libraryDependencies ++= {
   val akkaV = "2.3.16"
   val sprayV = "1.3.4"

src/main/scala/com/getbootstrap/savage/crypto/Pem.scala

@@ -0,0 +1,41 @@
+package com.getbootstrap.savage.crypto
+
+import scala.util.{Try,Success,Failure}
+import java.io.StringReader
+import java.security.spec.X509EncodedKeySpec
+import org.bouncycastle.util.io.pem.PemReader
+import org.bouncycastle.util.io.pem.PemObject
+
+
+sealed class MalformedPemException(cause: Throwable) extends RuntimeException("The given data did not conform to the PEM format!", cause)
+
+sealed class UnexpectedPemDataTypeException(expectedType: String, pemObj: PemObject)
+  extends RuntimeException(s"PEM contained data of unexpected type! Expected: ${expectedType} Actual: ${pemObj.getType}")
+
+// PEM is the name for the format that involves "-----BEGIN PUBLIC KEY-----" etc.
+object Pem {
+  private val PublicKeyPemType = "PUBLIC KEY"
+
+  @throws[MalformedPemException]("if there is a problem decoding the PEM data")
+  private def decode(pem: String): PemObject = {
+    val pemReader = new PemReader(new StringReader(pem))
+    val pemObjTry = Try { pemReader.readPemObject() }
+    val closeTry = Try { pemReader.close() }
+    (pemObjTry, closeTry) match {
+      case (Failure(readExc), _) => throw new MalformedPemException(readExc)
+      case (_, Failure(closeExc)) => throw new MalformedPemException(closeExc)
+      case (Success(pemObj), Success(_)) => pemObj
+    }
+  }
+
+  // Decodes PKCS8 data in PEM format into a X509EncodedKeySpec
+  // which can be handled by sun.security.rsa.RSAKeyFactory
+  @throws[UnexpectedPemDataTypeException]("if the PEM contains non-public-key data")
+  def decodePublicKeyIntoSpec(publicKeyInPem: String): X509EncodedKeySpec = {
+    val pemObj = decode(publicKeyInPem)
+    pemObj.getType match {
+      case PublicKeyPemType => new X509EncodedKeySpec(pemObj.getContent)
+      case unexpectedType => throw new UnexpectedPemDataTypeException(PublicKeyPemType, pemObj)
+    }
+  }
+}

src/main/scala/com/getbootstrap/savage/crypto/RsaPublicKey.scala

@@ -0,0 +1,16 @@
+package com.getbootstrap.savage.crypto
+
+import scala.util.Try
+import java.security.KeyFactory
+import java.security.PublicKey
+import java.security.spec.X509EncodedKeySpec
+
+
+sealed case class RsaPublicKey private(publicKey: PublicKey)
+
+object RsaPublicKey {
+  private val rsaKeyFactory = KeyFactory.getInstance("RSA") // Supported in all spec-compliant JVMs
+
+  def fromX509Spec(keySpec: X509EncodedKeySpec): Try[RsaPublicKey] = Try{ rsaKeyFactory.generatePublic(keySpec) }.map{ new RsaPublicKey(_) }
+  def fromPem(pem: String): Try[RsaPublicKey] = Try{ Pem.decodePublicKeyIntoSpec(pem) }.flatMap{ fromX509Spec(_) }
+}

src/main/scala/com/getbootstrap/savage/crypto/Sha1WithRsa.scala

@@ -0,0 +1,27 @@
+package com.getbootstrap.savage.crypto
+
+import java.security.Signature
+import java.security.SignatureException
+import java.security.InvalidKeyException
+
+
+object Sha1WithRsa {
+  private val signatureAlgorithmName = "SHA1withRSA" // Supported in all spec-compliant JVMs
+  private def newSignatureVerifier(): Signature = Signature.getInstance(signatureAlgorithmName)
+
+  def verifySignature(signature: Array[Byte], publicKey: RsaPublicKey, signedData: Array[Byte]): SignatureVerificationStatus = {
+    val verifier = newSignatureVerifier()
+    try {
+      verifier.initVerify(publicKey.publicKey)
+      verifier.update(signedData)
+      verifier.verify(signature) match {
+        case true => SuccessfullyVerified
+        case false => FailedVerification
+      }
+    }
+    catch {
+      case keyExc:InvalidKeyException => ExceptionDuringVerification(keyExc)
+      case sigExc:SignatureException => ExceptionDuringVerification(sigExc)
+    }
+  }
+}

src/main/scala/com/getbootstrap/savage/crypto/SignatureVerificationStatus.scala

@@ -0,0 +1,9 @@
+package com.getbootstrap.savage.crypto
+
+sealed trait SignatureVerificationStatus
+
+object SuccessfullyVerified extends SignatureVerificationStatus
+
+trait FailedVerification extends SignatureVerificationStatus
+object FailedVerification extends SignatureVerificationStatus
+case class ExceptionDuringVerification(error: Throwable) extends FailedVerification