Implement Signature: header verification for Travis

This theoretically addresses #43,
though ideally we should fetch Travis' public key ourselves
rather than requiring the user to copy it into the settings file themself.

README.md

@@ -120,11 +120,22 @@ savage {
     // The HMAC is used to verify that Savage is really being contacted by GitHub,
     // and not by some random hacker.
     github-web-hook-secret-key = abcdefg
-    // Used as a shared secret in a hashing scheme that's used to verify
-    // that Savage is really being contacted by Travis CI,
+    // Travis's public RSA key.
+    // Used to verify the signatures of Webhook requests from Travis,
+    // to ensure that Savage is really being contacted by Travis CI,
     // and not by some random hacker. For how to find your Travis token,
-    // see http://docs.travis-ci.com/user/notifications/#Authorization-for-Webhooks
-    travis-token = abcdefg
+    // See https://docs.travis-ci.com/user/notifications/#Verifying-Webhook-requests
+    // If you're using travis-ci.org, then the key is the value of
+    // config.notifications.webhook.public_key on https://api.travis-ci.org/config
+    travis-public-key = """-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAvtjdLkS+FP+0fPC09j25
+y/PiuYDDivIT86COVedvlElk99BBYTrqNaJybxjXbIZ1Q6xFNhOY+iTcBr4E1zJu
+tizF3Xi0V9tOuP/M8Wn4Y/1lCWbQKlWrNQuqNBmhovF4K3mDCYswVbpgTmp+JQYu
+Bm9QMdieZMNry5s6aiMA9aSjDlNyedvSENYo18F+NYg1J0C0JiPYTxheCb4optr1
+5xNzFKhAkuGs4XTOA5C7Q06GCKtDNf44s/CVE30KODUxBi0MCKaxiXw/yy55zxX2
+/YdGphIyQiA5iO1986ZmZCLLW8udz9uhW5jUr3Jlp9LbmphAC61bVSf4ou2YsJaN
+0QIDAQAB
+-----END PUBLIC KEY-----"""
 }
 ```
 

src/main/resources/application.conf

@@ -50,5 +50,13 @@ savage {
     username = twbs-savage
     password = XXXXXXXX
     github-web-hook-secret-key = abcdefg
-    travis-token = abcdefg
+    travis-public-key = """-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAvtjdLkS+FP+0fPC09j25
+y/PiuYDDivIT86COVedvlElk99BBYTrqNaJybxjXbIZ1Q6xFNhOY+iTcBr4E1zJu
+tizF3Xi0V9tOuP/M8Wn4Y/1lCWbQKlWrNQuqNBmhovF4K3mDCYswVbpgTmp+JQYu
+Bm9QMdieZMNry5s6aiMA9aSjDlNyedvSENYo18F+NYg1J0C0JiPYTxheCb4optr1
+5xNzFKhAkuGs4XTOA5C7Q06GCKtDNf44s/CVE30KODUxBi0MCKaxiXw/yy55zxX2
+/YdGphIyQiA5iO1986ZmZCLLW8udz9uhW5jUr3Jlp9LbmphAC61bVSf4ou2YsJaN
+0QIDAQAB
+-----END PUBLIC KEY-----"""
 }

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

@@ -5,5 +5,5 @@ sealed trait SignatureVerificationStatus
 object SuccessfullyVerified extends SignatureVerificationStatus
 
 trait FailedVerification extends SignatureVerificationStatus
-object FailedVerification extends SignatureVerificationStatus
+object FailedVerification extends FailedVerification
 case class ExceptionDuringVerification(error: Throwable) extends FailedVerification

src/main/scala/com/getbootstrap/savage/server/SavageWebService.scala

@@ -69,7 +69,7 @@ class SavageWebService(
       path("travis") {
         pathEndOrSingleSlash {
           post {
-            authenticatedTravisEvent(travisToken = settings.TravisToken, repo = settings.TestRepoId, log = log) { event =>
+            authenticatedTravisEvent(travisPublicKey = settings.TravisPublicKey, testRepo = settings.TestRepoId, log = log) { event =>
               SavageBranch(event.branchName) match {
                 case Some(branch@SavageBranch(prNum, _)) => {
                   branchDeleter ! branch

src/main/scala/com/getbootstrap/savage/server/Settings.scala

@@ -10,6 +10,7 @@ import akka.actor.ExtensionIdProvider
 import akka.actor.ExtendedActorSystem
 import akka.util.ByteString
 import org.eclipse.egit.github.core.RepositoryId
+import com.getbootstrap.savage.crypto.RsaPublicKey
 import com.getbootstrap.savage.github.Branch
 import com.getbootstrap.savage.util.{FilePathWhitelist,FilePathWatchlist,Utf8String,RichConfig}
 
@@ -19,7 +20,7 @@ class SettingsImpl(config: Config) extends Extension {
   val BotUsername: String = config.getString("savage.username")
   val BotPassword: String = config.getString("savage.password")
   val GitHubWebHookSecretKey: ByteString = ByteString(config.getString("savage.github-web-hook-secret-key").utf8Bytes)
-  val TravisToken: String = config.getString("savage.travis-token")
+  val TravisPublicKey: RsaPublicKey = RsaPublicKey.fromPem(config.getString("savage.travis-public-key")).get
   val UserAgent: String = config.getString("spray.can.client.user-agent-header")
   val DefaultPort: Int = config.getInt("savage.default-port")
   val SquelchInvalidHttpLogging: Boolean = config.getBoolean("savage.squelch-invalid-http-logging")

src/main/scala/com/getbootstrap/savage/server/TravisSignatureDirectives.scala

@@ -0,0 +1,54 @@
+package com.getbootstrap.savage.server
+
+import java.util.Base64
+import scala.util.Try
+import akka.event.LoggingAdapter
+import spray.http.FormData
+import spray.routing.{Directive1, MalformedHeaderRejection, MalformedRequestContentRejection, ValidationRejection}
+import spray.routing.directives.{BasicDirectives, HeaderDirectives, RouteDirectives, MarshallingDirectives}
+import com.getbootstrap.savage.crypto.{RsaPublicKey, Sha1WithRsa, SuccessfullyVerified}
+import com.getbootstrap.savage.util.Utf8String
+
+trait TravisSignatureDirectives {
+  import BasicDirectives.provide
+  import HeaderDirectives.headerValueByName
+  import RouteDirectives.reject
+  import MarshallingDirectives.{entity, as}
+
+  private val signatureHeaderName = "Signature"
+  private val signatureHeaderValue = headerValueByName(signatureHeaderName)
+
+  def travisSignature(log: LoggingAdapter): Directive1[Array[Byte]] = signatureHeaderValue.flatMap { base64 =>
+    Try{ Base64.getDecoder.decode(base64) }.toOption match {
+      case Some(bytesFromBase64) => provide(bytesFromBase64)
+      case None => {
+        log.error(s"Received Travis request with malformed Base64 value in ${signatureHeaderName} header!")
+        reject(MalformedHeaderRejection(signatureHeaderName, "Malformed Base64 value"))
+      }
+    }
+  }
+
+  private val formDataEntity = entity(as[FormData])
+
+  def stringEntityIfTravisSignatureValid(travisPublicKey: RsaPublicKey, log: LoggingAdapter): Directive1[String] = travisSignature(log).flatMap { signature =>
+    formDataEntity.flatMap { formData =>
+      formData.fields.toMap.get("payload") match {
+        case Some(payload:String) => {
+          Sha1WithRsa.verifySignature(signature = signature, publicKey = travisPublicKey, signedData = payload.utf8Bytes) match {
+            case SuccessfullyVerified => provide(payload)
+            case _ => {
+              log.warning("Received Travis request with incorrect signature! Signature={} Payload={}", signature, payload)
+              reject(ValidationRejection("Incorrect SHA-1+RSA signature"))
+            }
+          }
+        }
+        case None => {
+          log.error("Received Travis request that was missing the `payload` field!")
+          reject(MalformedRequestContentRejection("Request body form data lacked required `payload` field"))
+        }
+      }
+    }
+  }
+}
+
+object TravisSignatureDirectives extends TravisSignatureDirectives

src/main/scala/com/getbootstrap/savage/server/TravisWebHookDirectives.scala

@@ -6,21 +6,30 @@ import spray.routing.{Directive1, ValidationRejection}
 import spray.routing.directives.{BasicDirectives, RouteDirectives}
 import spray.json._
 import org.eclipse.egit.github.core.RepositoryId
+import com.getbootstrap.savage.crypto.RsaPublicKey
 import com.getbootstrap.savage.travis.{TravisJsonProtocol, TravisPayload}
 
 trait TravisWebHookDirectives {
   import RouteDirectives.reject
   import BasicDirectives.provide
-  import TravisAuthDirectives.stringEntityIfTravisAuthValid
+  import TravisSignatureDirectives.stringEntityIfTravisSignatureValid
   import TravisJsonProtocol._
 
-  def authenticatedTravisEvent(travisToken: String, repo: RepositoryId, log: LoggingAdapter): Directive1[TravisPayload] = stringEntityIfTravisAuthValid(travisToken, repo, log).flatMap{ entityJsonString =>
+  def authenticatedTravisEvent(travisPublicKey: RsaPublicKey, testRepo: RepositoryId, log: LoggingAdapter): Directive1[TravisPayload] = stringEntityIfTravisSignatureValid(travisPublicKey, log).flatMap{ entityJsonString =>
     Try { entityJsonString.parseJson.convertTo[TravisPayload] } match {
       case Failure(exc) => {
         log.error("Received Travis request with bad JSON!")
         reject(ValidationRejection("JSON was either malformed or did not match expected schema!"))
       }
-      case Success(payload) => provide(payload)
+      case Success(payload) => {
+        val TestRepo = testRepo
+        payload.repository.id match {
+          case TestRepo => provide(payload)
+          case otherRepo => {
+            reject(ValidationRejection(s"Received Travis request regarding irrelevant repo ${otherRepo}"))
+          }
+        }
+      }
     }
   }
 }

src/main/scala/com/getbootstrap/savage/travis/TravisJsonProtocol.scala

@@ -3,5 +3,6 @@ package com.getbootstrap.savage.travis
 import spray.json._
 
 object TravisJsonProtocol extends DefaultJsonProtocol {
-  implicit val travisPayloadFormat = jsonFormat4(TravisPayload.apply)
+  implicit val travisRepositoryFormat = jsonFormat2(Repository.apply)
+  implicit val travisPayloadFormat = jsonFormat5(TravisPayload.apply)
 }

src/main/scala/com/getbootstrap/savage/travis/TravisPayload.scala

@@ -2,14 +2,23 @@ package com.getbootstrap.savage.travis
 
 import scala.util.{Try,Success,Failure}
 import spray.http.Uri
+import org.eclipse.egit.github.core.RepositoryId
 import com.getbootstrap.savage.github.{Branch, CommitSha}
 import com.getbootstrap.savage.travis.build_status.BuildStatus
 
+case class Repository(
+  owner_name: String,
+  name: String
+) {
+  def id: RepositoryId = RepositoryId.create(owner_name, name)
+}
+
 case class TravisPayload(
   status_message: String,
   build_url: String,
   branch: String,
-  commit: String
+  commit: String,
+  repository: Repository
 ) {
   def status: BuildStatus = BuildStatus(status_message).getOrElse{ throw new IllegalStateException(s"Invalid Travis build status message: ${status_message}") }
   def commitSha: CommitSha = CommitSha(commit).getOrElse{ throw new IllegalStateException(s"Invalid commit SHA: ${commit}") }